Tag Archives: Lockheed Martin

Lockheed Martin Passes Its Mantle for Hybrid Airship Development and Commercialization to AT2

Peter Lobner, 10 May 2023

1. Introduction

On 9 May 2023, Lockheed Martin announced that its hybrid airship business, including intellectual property and related assets, had been transitioned to a newly formed, commercial company called ATAerospace. The Lockheed Martin press release reported, “AT2 Aerospace, based in Santa Clarita, California, is extending our work to bring hybrid airships to fruition. The AT2 team is developing airship solutions to support commercial and humanitarian applications around the world.  Dr. Robert Boyd, retired Lockheed Martin Hybrid Airship program manager, is president and chief operating officer of AT2 Aerospace.”

The AT2 website is here: www.at2aero.space 

2. Background on Lockheed Martin’s hybrid airship program

Since the 1980s, Lockheed Martin has been developing several different design approaches for semi-buoyant, hybrid airships with lifting body hulls. That work became focused in Lockheed Martin’s Advanced Development Programs (the Skunk Works) in Palmdale, CA, and produced an extensive series of patents related to large, hybrid airship design.

The only Lockheed Martin hybrid airship to fly was the P-791, which was a 120 foot (36.6 meter) long, tri-lobe, semi-buoyant hybrid airship that flew under a Defense Advanced Research Projects Agency (DARPA) sponsored Project WALRUS Phase 1 contract, and also served as a sub-scale technology demonstrator for future Lockheed Martin heavy-lift hybrid airships. The first flight of the P-791 took place on 31 January 2006 at Lockheed Martin’s facility in Palmdale.  Airship magazine reported that the P-791 flew six times. Lockheed Martin claimed that all flight test objectives were successfully met and there were no subsequent flight tests.

Lockheed Martin P-791. Source: Lockheed Martin (2006)

In March 2011, Lockheed Martin announced that it planned to develop a larger commercial version of the P-791, to be called SkyTug, which would be a scaled up hybrid airship designed to carry at least 20 tons of cargo.  A trademark application for the term “SkyTug” was filed on 25 August 2011.

By 2013, reference to SkyTug had disappeared and Lockheed Martin was promoting the LMH-1 as their next large commercial hybrid airship based on the P-791 design.  

General arrangement of the LMH-1 hybrid airship.  Source:  Lockheed Martin

Rendering, LMH-1 bow quarter view. Source: Lockheed Martin via BBC (November 2019)

On March 12, 2012 the U.S. Federal Aviation Administration (FAA) announced that Lockheed Martin Aeronautics submitted an application for type certification for the model LMZ1M (LMH-1), which is “a manned cargo lifting hybrid airship incorporating a number of advanced features.”  The FAA assigned docket number FAA-2013-0550 to that application. 

To address the gap in airship regulations head-on, Lockheed Martin submitted to the FAA their recommended criteria document, “Hybrid Certification Criteria (HCC) for Transport Category Hybrid Airships,” which is a 206 page document developed specifically for the LMZ1M (LMH-1).  The HCC is also known as Lockheed Martin Aeronautics Company Document Number 1008D0122, Rev. C, dated 31 January 2013.  You can download the HCC document and related public docketed items from the FAA website here: 


In November 2015, the FAA’s Seattle Aircraft Certification Office approved Lockheed’s project-specific certification plan for the LMZ1M (LMH-1). In a 17 November 2015 press release, Lockheed Martin announced:

“Given that Hybrid Airships did not fit within existing FAA regulations, the team worked to create a new set of criteria allowing non rigid hybrid airships to safely operate in a commercial capacity. Transport Canada was also involved in the development of this criteria to ensure it included safety concerns unique to Canada.”

“Lockheed Martin and the FAA have been working together for more than a decade to define the criteria to certify Hybrid Airships for the Transport Category. This criteria was approved by the FAA in April 2013.  Following that approval, the team has been developing the project specific certification plan over the past two years, which details how it will accomplish everything outlined in the Hybrid Certification Criteria.”

“Earlier this year Lockheed Martin along with Hybrid Enterprises LLC kicked off sales for the 20 ton variety of the Hybrid Airship. They are on track to deliver operational airships as early as 2018.”

No new documentation was subsequently added to the public webpage for docket FAA-2013-0550, so there was no public visibility of the type certification effort.  

In September 2017, Lockheed Martin reported it had Letters of Intent (LOIs) for 24 LMH-1 hybrid airships, with their largest customer being Straightline Aviation (https://www.straightlineaviation.com), which had signed an LOI for 12 LMH-1s. At that time, the first “float out” of the LMZ1M (LMH-1) had slipped to 2019. As of May 2023, the airship has not yet been “floated out”. 

On 9 May 2023, Lockheed Martin reported, “For some time, we have been in search of a transition partner to continue development of this important commercial work.” That “transition partner” is the newly formed, commercial company ATAerospace.

3. The AT2 Aerospace Z1 Hybrid Airship

As portrayed on the AT2 Aerospace website, their Z1 hybrid airship appears to be the current incarnation of the former Lockheed Martin LMH-1. AT2 Aerospace summarizes the main attributes of their Z1 hybrid airship as follows:

“AT2 Aerospace’s revolutionary hybrid airship is the future of aviation technology. Capable of operating in the most remote and inaccessible locations, this innovative aircraft offers a cost-effective solution for heavy cargo transpiration while minimizing environmental and social impact.”

  • “The Z1’s unique Air Cushion Landing System (ACLS) allows the Z1 to land and takeoff from almost any location on the planet.
  • The Z1 utilizes buoyant lift technology delivering exceptional fuel efficiency, minimizing carbon emissions, and ultimately reducing transportation costs.
  • The Z1 will connect emerging economies to global trade networks.
  • The Z1 moves cargo faster than sea and land transportation at a fraction of the cost of existing cargo aircraft, filling a major gap in the global transportation market from a speed vs. cost perspective.”

AT2 Aerospace also identified the following attributes:

  • Simple controls minimize human error
  • Large volume cargo bays, larger payloads
  • Safer in icing effects
  • Quiet: Ideal for noise sensitive locations

AT2 Aerospace expects that their Z1 hybrid airship will “open the entire world to commerce, humanitarian aid and exploration with affordable and reliable operations.”

General arrangement of the Z1 hybrid airship. Source: AT2 Aerospace

The near-term challenge for AT2 Aerospace will be to get clarity from the FAA on the actions remaining, and the approximate time scale, to conclude the first-ever type certification process for a hybrid airship in the U.S. With a type certificate in hand, the Z1 can be put to the test by a few early-adopters in what hopefully will become an emerging worldwide commercial airship market.

4. For more information

The Fork in the Road to Electric Power From Fusion

Peter Lobner, 1 February 2021

This article provides a brief overview of the “mainstream” international plans to deliver the first large tokamak commercial fusion power plant prototype in the 2060 to 2070 timeframe.  Then we’ll take a look at alternate plans that could lead to smaller and less expensive commercial fusion power plants being deployed much sooner, perhaps in the 2030s. These alternate plans are enabled by recent technical advances and a combination of public and private funding for many creative teams that are developing and testing a diverse range of fusion machines that may be developed in the near-term into compact, relatively low-cost fusion power plants.  

This article includes links in Section 6 to a set of supporting articles that provide details on 18 fusion power reactor development projects, mostly at private firms. You can download a pdf copy of this main article here: https://lynceans.org/wp-content/uploads/2021/02/The-Fork-in-the-Road-to-Electric-Power-From-Fusion-converted_1.pdf

1. Plodding down the long road to controlled nuclear fusion with ITER

Mainstream fusion development is focused on the construction of the International Thermonuclear Experimental Reactor (ITER), which is a very large magnetic confinement fusion machine.  The 35-nation ITER program describes their reactor as follows:  “Conceived as the last experimental step to prove the feasibility of fusion as a large-scale and carbon-free source of energy, ITER will be the world’s largest tokamak, with ten times the plasma volume of the largest tokamak operating today.” ITER is intended “to advance fusion science and technology to the point where demonstration fusion power plants can be designed.”

ITER is intended to be the first fusion experiment to produce a net energy gain (“Q”) from fusion.  Energy gain is the ratio of the amount of fusion energy produced (Pfusion) to the amount of input energy needed to create the fusion reaction (Pinput).  In its simplest form, “breakeven” occurs when Pfusion = Pinput and Q = 1.0.  The highest value of Q achieved to date is 0.67, by the Joint European Torus (JET) tokamak in 1997.The ITER program was formally started with the ITER Agreement, which was signed on 21 November 2006.  

Nations contributing to the manufacture of major ITER 
components.  Source: SciTechDaily (28 Jul 2020)

The official start of the “assembly phase” of the ITER reactor began on 28 July 2020. The target date of “first plasma” currently is in Q4, 2025.  At that time, the reactor will be only partially complete.  During the following ten years, construction of the reactor internals and other systems will be completed along with a comprehensive testing and commissioning program. The current goal is to start experiments with deuterium / deuterium-tritium (D/D-T) plasmas in December 2035.  

After initial experiments in early 2036, there will be a gradual transition to fusion power production over the next 12 – 15 months.  By mid-2037, ITER may be ready to conduct initial high-power demonstrations, operating at several hundred megawatts of D-T fusion power for several tens of seconds.  This milestone will be reached more than 30 years after the ITER Agreement was signed.

Subsequent experimental campaigns will be planned on a two-yearly cycle. The principal scientific mission goals of the ITER project are:

  • Produce 500 MW of energy from fusion while using only 50 MW of energy for input heating, yielding Q ≥ 10
  • Demonstrate Q ≥ 10 for burn durations of 300 – 500 seconds (5.0 – 8.3 minutes)
  • Demonstrate long-pulse, non-inductive operation with Q ~ 5 for periods of up to 3,000 seconds (50 minutes).

All that energy will get absorbed in reactor structures, with some of it being carried off in cooling systems.  However, ITER will not generate any electric power from fusion.  

The total cost of the ITER program currently is estimated to be about $22.5 billion. In 2018, Reuters reported that the US had given about $1 billion to ITER so far, and was planning to contribute an additional $500 million through 2025. In Fiscal Year 2018 alone, the US contributed $122 million to the ITER project.

You’ll find more information on the ITER website, including a detailed timeline, at the following link: https://www.iter.org

The ITER site in 2020, being built next to the Cadarache facility in Saint-Paul-lès-Durance, in Provence, southern France.  Source: Macskelek via Wikipedia

2.  Timeline for a commercial fusion power plant based on ITER

In December 2018, a National Academy of Sciences, Engineering & Medicine (NASEM) committee issued a report that included the following overview of timelines for fusion power deployment based on previously studied pathways for developing fusion power plants derived from ITER. The timelines for the USA, South Korea, Europe, Japan and China are shown below.

Source: “A Strategic Plan for U.S. Burning
Plasma Research” (NASEM, 2019)

All of the pathways include plans for a DEMO fusion power plant (i.e., a prototype with a power conversion system) that would start operation between 2050 and 2060.  Based on experience with DEMO, the first commercial fusion power plants would be built a decade or more later. You can see that, in most cases, the first commercial fusion power plant is not projected to begin operation until the 2060 to 2070 timeframe.

3. DOE is helping to build a fork in the road

Fortunately, a large magnetic confinement tokamak like ITER is not the only route to commercial fusion power.  However, ITER currently is consuming a great deal of available resources while the promise of fusion power from an ITER-derived power plant remains an elusive 30 years or more away, and likely at a cost that will not be commercially viable.  

Since the commitment was made in the early 2000s to build ITER, there have been tremendous advances in power electronics and advanced magnet technologies, particularly in a class of high temperature superconducting (HTS) magnets known as rare-earth barium copper oxide (REBCO) magnets that can operate at about 90 °K (-297 °F), which is above the temperature of liquid nitrogen (77 °K; −320 °F). These technical advances contribute to making ITER obsolete as a path to fusion power generation.

A 2019 paper by Martin Greenwald describes the relationship of constant fusion gain (Q = Pfusion / Pinput) to the magnetic field strength (B) and the plasma radius (R) of a tokamak device.  As it turns out, Q is proportional to the product of B and R, so, for a constant gain, there is a tradeoff between the magnetic field strength and the size of the fusion device. This can be seen in the comparison between the relative field strengths and sizes of ITER and ARC (a tokomak being designed now), which are drawn to scale in the following chart. 

Contours of constant fusion gain (Q) plotted against magnetic field strength (T, Tesla) and device size (plasma radius in meters): Source: Greenwald (2019)

ITER has lower field strength conventional superconducting magnets and is much larger than ARC, which has much higher field strength HTS magnets that enable its compact design. Greenwald explains, “With conventional superconductors, the region of the figure above 6T was inaccessible; thus, ITER, with its older magnet technology, is as small as it could be.” So, ITER will be a big white elephant, useful for scientific research, but likely much less useful on the path to fusion power generation than anyone expected when they signed the ITER Agreement in 2006.

For the past decade, there has been increasing interest in, and funding for, developing lower cost, compact fusion power plants using any fusion technology that can deliver a useful power generation capability at an commercially viable cost. Department of Energy’s (DOE) Advanced Research Project Agency – Energy (ARPA-E) has recommended the following cost targets for such a commercial fusion power plant:

Overnight capital cost of < US $2 billion and < $5/W

At $5/W, the upper limit would be a 400 MWe fusion power plant.

Since 2014, DOE has created a series of funding programs for fusion R&D projects to support development of a broad range of compact, low-cost fusion power plant design concepts.  This was a significant change for the DOE fusion program, which has been contributing to ITER and a whole range of other fusion-related projects, but without a sense of urgency for delivering the technology needed to develop and operate commercial fusion power plants any time soon.  Now, a small part of the DOE fusion budget is focused on resolving some of the technical challenges and de-risking the path forward sooner rather than later, and thereby improving the investment climate to the point that investors become willing to contribute to the development of small, low-cost fusion power plants that may be able to produce electrical power within the next decade or two.

These DOE R&D programs are administered ARPA-E and the Office of Science, Fusion Energy Sciences (FES).

  • ARPA-E advances high-potential, high-impact energy technologies that are too early for private-sector investment. The ARPA-E fusion R&D programs are named ALPHA, IDEAS, BETHE, TINA and GAMOW. ARPA-E jointly funds the GAMOW fusion R&D program and part of the BETHE program with FES. In addition, the ARPA-E OPEN program makes R&D investments in the entire spectrum of energy technologies, including fusion.
  • FES is the largest US federal government supporter of research that is addressing the remaining obstacles to commercial fusion power.  The FES fusion R&D program is named INFUSE. In addition FES jointly funds GAMOW and part of BETHE with ARPA-E.

Here’s an overview of these DOE programs.

DOE ARPA-E ALPHA program (2015 – 2020)

In 2015, ARPA-E initiated a five-year, $30 million research program into lower-cost approaches to producing electric power from fusion.  This was known as the ALPHA program (Accelerating Low-Cost Plasma Heating and Assembly). The goal was to expand the range of potential technical solutions for generating power from fusion, focusing on small, low-cost, pulsed magneto-inertial fusion (MIF) devices.  

The ARPA-E ALPHA program home page is here: https://arpa-e.energy.gov/technologies/programs/alpha

There were nine program participants in the ALPHA program. Helion Energy ($3.97 million) and MIFTI ($4.60 million) were among the private fusion reactor firms receiving ALPHA awards.  Los Alamos National Laboratory (LANL) received $6.63 million to fund the Plasma Liner Experiment (PLX-α) team, which included the private firm HyperV Technologies Corp.

In 2018, ARPA-E asked JASON to assess its accomplishments on the ALPHA program and the potential of further investments in this field.  Among their findings, JASON reported that MIF is a physically plausible approach to controlled fusion and, in spite of very modest funding to date, some particular approaches are within a factor of 10 of scientific break-even.  JASON also recommended supporting all promising approaches, while giving near-term priority to achieving breakeven (Q ≥ 1) in a system that can be scaled up to be commercial power plant. You can read the November 2018 JASON report here: https://fas.org/irp/agency/dod/jason/fusiondev.pdf

DOE ARPA-E IDEAS program (2017 – 2019)

The ARPA-E IDEAS program (Innovative Development in Energy-Related Applied Science) provides support of early-stage applied research to explore pioneering new concepts with the potential for transformational and disruptive changes in any energy technology. IDEAS awards are restricted to a maximum of $500,000 in funding.  There have been 59 IDEAS awards for a broad range of energy-related technologies, largely to national laboratories and universities.

The IDEAS program home page is here: https://arpa-e.energy.gov/technologies/programs/ideas

There was one fusion-related IDEAS award to the University of Washington ($482 k).

DOE ARPA-E OPEN program (2018)

In 2018, ARPA-E issued its fourth OPEN funding opportunity designed to catalyze transformational breakthroughs across the entire spectrum of energy technologies, including fusion.  OPEN 2018 is a $199 million program funding 77 projects. 

The OPEN 2018 program home page is here: https://arpa-e.energy.gov/technologies/open-programs/open-2018

Four fusion-related projects were funded for a total of about $12 million.  ZAP Energy ($6.77 million), CTFusion ($3.0 million) and Princeton Fusion Systems ($1.1 million) were among the private fusion reactor firms receiving OPEN 2018 awards.

DOE ARPA-E TINA Fusion Diagnostics program (2019 – 2021)

The TINA program established diagnostic “capability teams” to support state-of-the-art diagnostic system construction/deployment and data analysis/interpretation on ARPA-E-supported fusion experiments.  This program awarded $7.5 million to eight teams, primarily from national laboratories and universities.

DOE ARPA-E BETHE program (2020 – 2024)

DOE’s ARPA-E also runs the BETHE program (Breakthroughs Enabling THermonuclear-fusion Energy), which is a $40 million program that aims to deliver a large number of lower-cost fusion concepts at higher performance levels. BETHE R&D is focused in the following areas:

  • Concept development to advance the performance of inherently lower cost but less mature fusion concepts.
  • Component technology development that could significantly reduce the capital cost of higher cost, more mature fusion concepts.
  • Capability teams to improve/adapt and apply existing capabilities (e.g., theory/modeling, machine learning, or engineering design/fabrication) to accelerate the development of multiple concepts.

FES contributes $5 million to BETHE program funding for component technology development. The BETHE program home page is here: https://arpa-e.energy.gov/technologies/programs/bethe

Sixteen research projects were awarded on 7 April 2020. Brief project descriptions are available here: https://arpa-e.energy.gov/sites/default/files/documents/files/BETHE_Project_Descriptions_FINAL.24.20.pdf

ZAP Energy ($1 million) and Commonwealth Fusion Systems ($2.39 million) were among the private fusion reactor firms directly receiving BETHE awards. 

The following awards were made to universities or national laboratories working with teams that include a significant role for a private fusion reactor firm: 

  • University of Washington received $1.5 million for improving IDCD plasma control, which is applicable to their collaborative work with CTFusion on the Dynomak fusion reactor concept.
  • LANL received $4.62 million to fund the Plasma Liner Experiment (PLX-α) team, which includes HyperJet

DOE ARPA-E / FES GAMOW program (2020 – 2024)

Yet another DOE funding program for fusion research is named GAMOW (Galvanizing Advances in Market-Aligned Fusion for an Overabundance of Watts), which is a $29 million program announced in February 2020.  GAMOW is jointly funded and overseen by ARPA-E and FES.  GAMOW program focuses on the following three areas:

  • Technologies and subsystems between the fusion plasma and balance of plant.
  • Cost-effective, high-efficiency, high-duty-cycle driver technologies.
  • Crosscutting areas such as novel fusion materials and advanced in additive manufacturing for fusion-relevant materials and components.

The GAMOW program home page is here: https://arpa-e.energy.gov/technologies/programs/gamow

In September 2020, ARPA-E announced 14 projects, primarily for national laboratory and university participants that were funded under the GAMOW program. Brief project descriptions are available here: https://arpa-e.energy.gov/sites/default/files/documents/files/GAMOW_Project_Descriptions_FINAL_9.2.20.pdf

Princeton Fusion Systems ($1.1 million) was among the private fusion reactor firms receiving GAMOW awards.

DOE FES INFUSE program (2020 – present)

The DOE FES INFUSE program (Innovation Network for Fusion Energy) was created to “accelerate fusion energy development in the private sector by reducing impediments to collaboration involving the expertise and unique resources available at DOE laboratories.” ….”DOE-FES will accept basic research applications focused on innovation that support production and utilization of fusion energy (e.g., for generation of electricity, supply of process heat, etc.)….”

In Fiscal Years 2020 and 2021, the INFUSE program annual budget was $4 million. INFUSE is a cost sharing program with DOE-FES funding 80% of a project’s cost and the award recipient funding the remaining 20%. The DOE-FES INFUSE program home page is here: https://infuse.ornl.gov

So far, there have been three rounds of INFUSE awards.  I think you will find that it is much more difficult to find detailed information on the DOE FES INFUSE awards, which are administered by Oak Ridge National Laboratory (ORNL), than it is to find information on any of the DOE ARPA-E program.  Here’s a brief INFUSE summary.

  • 1st round FY 2020: On 15 October 2019, DOE announced the first INFUSE awards, which provided funding for 12 projects with representation from six private companies partnering with six national laboratories.  The six private firms included:  Commonwealth Fusion Systems (4 awards) and TAE Technologies, Inc. (3 awards)
  • 2nd round FY 2020: On 3 September 2020, DOE announced funding for 10 projects.  The private firms included:  Commonwealth Fusion Systems (3 awards), TAE Technologies, Inc. (1 award), Tokamak Energy, Inc. (UK, 3 awards), and General Fusion Corp. (Canada, 1 award).
  • 1st round FY 2021: On 3 December 2020, DOE announced funding 10 projects in a second round of FY 2021 INFUSE awards. The private firms receiving awards included:  Commonwealth Fusion Systems (1 award), General Fusion Corp. (Canada, 1 award), MIFTI (1 award), Princeton Fusion Systems (1 award), TAE Technologies, Inc. (2 awards), Tokamak Energy, Inc. (UK, 2 awards).

DOE-FES has issued a call for new proposals for FY 2021 INFUSE awards. The closing date for submissions is 26 February 2021.

DOE SBIR and STTR programs

The DOE Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs develop innovative techniques, instrumentation, and concepts that have applications to industries in the private sector, including in the fusion sector. The SBIR / STTR home page is here:  https://www.energy.gov/science/sbir/small-business-innovation-research-and-small-business-technology-transfer

Fusion-related awards are listed here: https://science.osti.gov/sbir/Research-Areas-and-Impact#FES

The DOE grand total

So far, these ARPA-E and FES programs have committed about $127 million in public funds to 77 different projects between 2014 and 2021.  While some of the awards are sizeable ($5 – 6 million), many are very modest awards. The DOE total for all small (non-mainstream) fusion projects over a seven year period is about the same amount as the annual US contribution to the ITER program, which isn’t going lead to a fusion power plant in my lifetime, if ever.

While DOE has been kind enough to create the fork in the road, they do not have the deployable financial resources to push on to the next step of actually building prototypes of commercial fusion power plants in the near term. 

4.  A roadmap for achieving commercial fusion sooner

In 2019 and 2021, the National Academies and DOE-FES, respectively, published the recommendations of committees that were charged with defining the path(s) forward for the US to achieve commercial fusion power.  In both cases, the committee recommended continued support for ITER while urging the US to proceed with a separate national program that encourages and supports public-private partnerships to build compact power plants that produce electricity from fusion at the lowest possible capital cost.  These committee reports are briefly summarized below. 

National Academies: “Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research” (2019)

In December 2018, a National Academy of Sciences, Engineering & Medicine (NASEM) committee issued a report entitled, “A Strategic Plan for U.S. Burning Plasma Research.” 

As noted previously, the NASEM report described the current path forward based on power plants derived largely from ITER technology.  On this path, the first commercial fusion power plant is not projected to begin operation until the 2060 to 2070 timeframe.

The NASEM committee report is very important because it defines an alternate pathway (i.e., the fork in the road) that could deliver fusion power considerably sooner and at much lower capital cost. 

The committee offered the following recommendations:

  • The US should remain an ITER partner.  This is the most cost-effective way to gain experience with burning plasma at the scale of a power plant.  However:
    • Significant R&D is required in addition to ITER to produce electricity from this type of fusion reactor.
    • ITER is too large and expensive to be economically competitive in the US market when compared to other carbon-neutral energy technologies.
  • The US should start a national program of accompanying research and technology leading to the construction of a compact pilot power plant that produces electricity from fusion at the lowest possible capital cost.
    • Emphasize developing innovative, world-leading solutions.
    • Effective application of US near-term R&D investments is critical, as other nations continue to invest in new fusion facilities that advance their own approaches.

You can read the NASEM report here: https://www.nationalacademies.org/our-work/a-strategic-plan-for-us-burning-plasma-research

DOE FES: “Powering the Future – Fusion & Plasmas”  (2021)

In January 2021, DOE FES published a draft report from their Fusion Energy Sciences Advisory Committee (FESAC) entitled “Powering the Future – Fusion & Plasmas.”  This draft report supports the NASEM committee recommendations and concluded that there are two viable paths to commercial fusion power:

  • Partnership in the ITER fusion project is essential for US fusion energy development, as is supporting the continued growth of the private sector fusion energy industry. 
  • Public-private partnerships have the potential to reduce the time required to achieve commercially viable fusion energy. 
  • The fusion pilot plant goal requires “a pivot toward research and development of fusion materials and other needed technology.” Several new experimental facilities were recommended.

You can read the complete draft FESAC report here: https://science.osti.gov/-/media/fes/fesac/pdf/2020/202012/DRAFT_Fusion_and_Plasmas_Report_120420.pdf

As of late January 2021, the FESAC final report was in preparation.   When available, it will be posted here:  http://usfusionandplasmas.org

Funding at the fork in the road

At the fork in the road, the US will be hedging its bets and taking both paths, continuing to support ITER at the current level (about $125 million/year) while building new fusion experimental facilities and trying to place a stronger emphasis on timely development of compact fusion power plants through public-private partnerships as well as infusions of private capital.  

In the years ahead, the DOE FES fusion budget is expected to be essentially flat, with growth at just a modest rate of 2%/year being among the likely range of budget scenarios.  At the same time, FES will attempt to launch several new major fusion R&D facilities and related programs, as recommended by FESAC.

Without a significantly bigger budget authorization from Congress, the FES budget becomes a zero sum game.  To create the budget for any of these new R&D facilities and programs, other part of the FES budget have to lose. In this constrained budget environment, I think FES funding for compact fusion power plant development will find stiff competition and will not be on a growth path.

Recall that ARPA-E’s role is to advance high-potential, high-impact energy technologies that are too early for private-sector investment. When major risk issues for a particular fusion reactor concept have been resolved to an appropriate level, funding from ARPA-E may be redirected to other higher risk matters waiting to be addressed.  

While the NASEM and FESAC reports support public-private partnerships, the sheer magnitude of the funds required (many billions of dollars) to develop several small prototype fusion power plant designs in parallel exceeds DOE’s ability to fund the deals at the same level as the current 80% (DOE) / 20% (private) partnership deals.  The FES annual budget for the past three years has been quite modest: $564 million (FY2019 enacted), $671 million (FY2020 enacted) and $425 million (FY2021 requested).

Making real progress toward deployment of operational fusion power plants will depend on billions of dollars in private / institutional capital being invested in the firms that will design and build the first small commercial fusion power plants.  

I think DOE and the commercial fusion power industry are in a similar position to NASA and the commercial spaceflight industry two decades ago when Blue Origin (Jeff Bezos, 2000) and SpaceX (Elon Musk, 2002) were founded.  At that time, the traditional route to space was via NASA.  Two decades later, it’s clear that many commercial firms and their investors have contributed to building a robust low Earth orbit spaceflight industry that could never have been developed in that short time frame with NASA’s limited budget.  In the next two decades, I think the same type of transition needs to occur in the relationship between DOE and the private sector fusion industry if we expect to reap the benefits of clean fusion power soon.  It’s time for FES and the commercial fusion industry to confirm that they share a vision and a common aggressive timeline for bringing small commercial fusion power plants to the market.  That point doesn’t come across in the FESAC report.

Private and institutional investors already making major investments in the emerging fusion energy market.  As you might expect, some fusion firms have been much more successful than others in raising funds.  You’ll find a summary of publically available funding information on the Fusion Energy Base website here: https://www.fusionenergybase.com/organization/commonwealth-fusion-systems

5. The US Navy also may be building a fork in the road

The Navy has been quietly developing its own concepts for compact fusion power plants.  We’ll take a look at three recent designs. Could the Navy wind up being an important contributor to the development and deployment of commercial fusion power plants? 

6. The race is on to beat ITER with smaller, lower-cost fusion

In this section, we’ll take a look at the status of the following small fusion power plant development efforts, mostly by private companies. 

Collectively, they are applying a diverse range of technologies to the challenge of generating useful electric power from fusion at a fraction of the cost of ITER.  Based on claims from the development teams, it appears that some of the compact fusion reactor designs are quite advanced and probably will be able to demonstrate a net energy gain (Q > 1.0) in the 2020s, well before ITER. 

You’ll find details on these 18 organizations and their fusion reactor concepts in my separate articles at the following links:

7.  Conclusions

There certainly are many different technical approaches being developed for small, lower-cost fusion power plants. Several teams are reporting encouraging performance gains that suggest that their particular solutions are on credible paths toward a fusion power plant. However, as of January 2021, none of the operating fusion machines have achieved breakeven, with Q = 1.0, or better.  It appears that goal remains at least a few years in the future, even for the most advanced contenders.

The rise of private funding and public-private partnerships is rapidly improving the resources available to many of the contenders.  Good funding should spur progress for many of the teams.  However, don’t be surprised if one or more teams wind up at a technical or economic dead end that would not lead to a commercially viable fusion power plant. Yes, I think ITER is heading down one of those dead ends right now.

So, where does that leave us?  The promise for success with a small, lower-cost fusion power plant is out there, and such power plants should win the race by a decade or more over an ITER-derived fusion power plant.  While there are many contenders, which ones are the leading contenders for deploying a commercially viable fusion power plant?

To give some perspective, it’s worth taking a moment to recall the earliest history of the US commercial nuclear power industry, which is recounted in detail for the period from 1946 – 1963 by Wendy Allen in a 1977 RAND report and summarized in the following table.

US fission demonstration power plants. Source: RAND R-2116-NSF

The main points to recognize from the RAND report are:

  • Eight different types of fission reactors were built as demonstration plants and tested. All of the early reactors were quite small in comparison to later nuclear power plants.
  • Some were built on Atomic Energy Commission (AEC, now DOE) national laboratory sites and operated as government-owned proof-of-principle reactors.  The others were licensed by the AEC (now the Nuclear Regulatory Commission, NRC) and operated by commercial electric power utility companies.  These reactors were important for building the national nuclear regulatory framework and the technical competencies in the commercial nuclear power and electric utility industries.
  • In the long run, only two reactor designs survived the commercial test of time and proved their long-term financial viability:  the pressurized water reactor (PWR) and the boiling water reactor (BWR), which are the most common types of fission power reactors operating in the world today.

See RAND report R-2116-NSF for more information of the early US commercial fission reactor demonstration plant programs here: https://www.rand.org/pubs/reports/R2116.html

With the great variety of candidate fusion power plant concepts being developed today, we simply don’t know which ones will be the winners in a long-term competition, except to say that an ITER-derived power plant will not be among the winners.  What we need is a national demonstration plant program for small fusion reactors.  This means we need the resources to build and operate several different fusion power reactor designs soon and expect that the early operating experience will quickly drive the evolution of the leading contenders toward mature designs that may be successful in the emerging worldwide market for fusion power. The early fission reactor history shows that we should expect that some of the early fusion power plant designs won’t survive in the long-term fusion power market, for a variety of reasons.

Matthew Moynihan, in his 2019 article, “Selling Fusion in Washington DC,” on The Fusion Podcast website, offered the following approach, borrowed from the biotech industry, to build a pipeline of credible projects while driving bigger investments into the more mature and more promising programs. Applying this approach to the current hodgepodge of DOE fusion spending would yield more focused spending of public money toward the goal of delivering small fusion power plants as soon as practical. The actual dollar amounts in the following chart can be worked out, but I think the basic principle is solid.

Source: The Fusion Podcast, 12 January 2019

With this kind of focus from DOE, the many contenders in the race to build a small fusion power plant could be systematically ranked on several parameters that would make their respective technical and financial risks more understandable to everyone, especially potential investors.  With an unbiased validation of relative risks from DOE, the leading candidates in the US fusion power industry should be able to raise the billions of dollars that will be needed to develop their designs into the first wave of demonstration fusion power plants, like the US fission power industry did 60 to 70 years ago.

Perhaps Carly Anderson had the right idea when she suggested Fantasy Fusion as a way to introduce some fun into the uncertain world of commercial fusion power development and investment.  You can read her September 2020 article here: https://medium.com/prime-movers-lab/fantasy-fusion-77621cc901e2

If you believe we’re coming into the home stretch, it’s not too late to place a real bet by actually investing in your favorite fusion team(s).  It is risky, but the commercial fusion power trophy will be quite a prize!  I’m sure it will come with some pretty big bragging rights.

8. For more information




DOE ARPA-E IDEAS program (2017 – 2019)




Modern Airships – Part 1

Peter Lobner, updated 8 July 2024 (post-Rev. 6)

1. Introduction

Modern Airships is a three-part document that contains an overview of modern airship and aerostat technology in Part 1 and links in Parts 1, 2 and 3 to more than 275 individual articles on historic and advanced airship designs.  This is Part 1.  Here are the links to the other two parts:

To help you navigate the large volume of material in these three documents, please refer to following indexes. The first index simply lists the article titles in alphabetic order within each Part.

Parts 1 & 2 address similar types of airships and unpowered aerostats. The following airship type index enables you to see all of the airships and aerostats addressed in Parts 1 & 2, grouped by type, with direct links to the relevant articles.

The airships described in Part 3 are relatively exotic concepts in comparison to the more utilitarian and heavy-lift airships that dominate Parts 1 and 2. As shown in the following index, the airships in Part 3 are organized by function rather than airship type, which sometimes is difficult to determine with the information available.

Modern Airships – Part 1 begins with an overview of modern airship and aerostat technology, continues with a graphic table that identifies the airships addressed in this part, and concludes by providing links to more than 100 individual articles on these airships. A downloadable pdf copy of Part 1 is available here:

If you have any comments or wish to identify errors in this document, please send me an e-mail to:  [email protected].

I hope you’ll find the Modern Airships series to be informative, useful, and different from any other single document on this subject.

Best regards,

Peter Lobner

8 July 2024

Record of revisions to Part 1

  • Original Modern Airships post, 26 August 2016: addressed 14 airships in a single post.
  • Expanded the Modern Airships post and split it into three parts, 18 August 2019: Part 1 included 22 linked articles.
  • Part 1, Revision 1, 21 December 2020: Added 15 new articles, split the existing Aeros article into two articles and updated all of the original articles. Part 1 now had 38 articles.
  • Part 1, Revision 2, 3 April 2021: Updated the main text and 10 existing articles, and expanded and reorganized the graphic tables. Part 1 still had 38 articles
  • Part 1, Revision 3, 26 August 2021: Added 34 new articles, split the existing Helistat article into five articles and the Aereon article into two articles, and expanded and reorganized the graphic tables. Also updated 23 existing articles. Part 1 now had 77 articles.
  • Part 1, Revision  4, 12 February 2022: Added 12 new articles, split the existing Airlander article into two updated articles (prototype, production), moved Halo to Part 3, expanded the graphic tables and updated 17 additional existing articles.  A detailed summary of changes incorporated in Part 1 Rev 4 is listed here. Part 1 now had 89 articles.
  • Part 1, Revision  5, 10 March 2022: Added 2 new articles, split rigid & semi-rigid airships in the graphic tables, and updated 58 existing articles. With this revision, all Part 1 linked articles have been updated in February or March 2022. A detailed summary of changes incorporated in Part 1 Rev 5 is listed here. Part 1 now has 91 articles.
  • Part 1, Revision 6, 17 March 2024: This revision includes a major reorganization of Parts 1 & 2 to better aggregate airships and unpowered aerostats by type, with a corresponding reorganization of the graphic tables. Over the past two years, 15 new articles were added to Part 1 and 28 articles were updated. In the final changes for Rev. 6, several articles were moved between Parts 1 & 2. A detailed summary of changes incorporated in Part 1 Rev 6 is listed here. Part 1 now has 107 articles.

Part 1, changes since Rev. 6 (17 March 2024)

New articles:

  • None yet

Updated articles:

  • LTA Research and Exploration – 8 July 2024

2.  Well-established benefits and opportunities, but a risk-averse market

For several decades, there has been significant interest in the use of modern lighter-than-air craft and hybrid airships in a variety of military, commercial and other roles, including:

  • Heavy cargo carriers operating point-to-point between manufacturer and end-user, eliminating inter-modal load transfers enroute
  • Heavy cargo carriers serving remote and/or unimproved sites not adequately served by other modes of transportation
  • Disaster relief, particularly in areas not easily accessible by other means
  • Persistent optionally-manned surveillance platforms for military intelligence, surveillance & reconnaissance (ISR), maritime surveillance, border patrol, search and rescue
  • Passenger airships
  • Commercial flying cruise liner / flying hotel
  • Airship yacht
  • Personal airship
  • Drone carrier
  • High altitude regional communications node

One of the very significant factors driving interest in modern airships is that they offer the potential to link isolated regions with the rest of the world while doing so in a way that should have lower environmental impacts than other transportation alternatives for those regions. This target market for airships exists in more than two-thirds of the world’s land area where more than half the world’s population live without direct access to paved roads and reliable ground transportation.

This matter is described well in a 21 February 2016 article by Jeanne Marie Laskas, “Helium Dreams – A new generation of airships is born,” which is posted on The New Yorker website at the following link: https://www.newyorker.com/magazine/2016/02/29/a-new-generation-of-airships-is-born

In spite of the significant interest and the development of many promising airship designs, an actual worldwide airship cargo and passenger transportation industry has been very slow in developing.  To give you an example of how slow:

  • As of November 2023, other than a modest number of commercially certified blimps used largely as advertising platforms, the Zeppelin NT 07 is the only advanced airship that has been certified and is flying regularly in commercial passenger service. 
  • At the March 2019 Aviation Innovations Conference – Cargo Airships in Toronto, Canada, Solar Ship CEO Jay Godsall proposed an industry-wide challenge to actually demonstrate by July 2021 airships that can move a 3 metric ton (6,614 lb) standard 20 foot intermodal container configured as a mobile medical lab 300 km (186 mi) to a remote location. Godsall noted that this capability would be of great value if it did exist, for example, in support of relief efforts in Africa and other regions of the world.

So in spite of the airship industry having developed many designs capable of transporting 10’s to 100’s of tons of cargo thousands of miles, today there is not a single airship than can transport a 3 metric ton (6,614 lb) payload 300 km (186 mi).

Why has the airship industry been so slow to develop?  The bottom line has been a persistent lack of funding.  With many manufacturers having invested in developing advanced designs in varying levels of detail, the first to secure adequate funding will be able to take the next steps to build and certify a manufacturing facility, build and flight test a full-scale prototype airship, complete the airship type certification process, and start offering a certified airship for sale.

There are some significant roadblocks in the way:

  • No full-scale prototypes are flying:  Many airship firms currently have little more than slide presentations to show to potential investors and customers.  There are few sub-scale airship demonstrators, but no full-scale prototypes.  The airship firms are depending on potential investors and customers making a “leap of faith” that the “paper” airship actually can be delivered. However, this situation will change significantly in the next few years as several airship manufacturers (i.e., LTA Research and Exploration, Flying Whales and Hybrid Air Vehicles) finally complete their full-scale, large airship prototypes and commence flight testing.
  • Immature manufacturing capability:  While the airship industry has been good at developing many advanced designs, some claiming to exist as “construction-ready” plans, few airship firms are in the process of building an airship factory. The industrial scale-up factor for an airship firm to go from the design and engineering facilities existing today to the facilities needed for series production of full-scale airships is huge.  LTA Research and Exploration is one of the few firms with access to modernized large airship hangars (the former Goodyear Airdock in Akron OH and the former Navy airship hangars at Moffett Field, CA) for use as manufacturing facilities. In 2016, Russian airship manufacturer Augur RosAeroSystems proposed building a new factory to manufacture up to 10 ATLANT airships per year. The funding requirement for that factory was estimated at $157 million.  The exact amount isn’t important.  No matter how you look at it, it’s a big number.  Large investments are needed for any airship firm to become a viable manufacturer.
  • Significant financial risk: The amount of funding needed by airship firms to make the next steps toward becoming a viable manufacturer exceeds the amount available from venture capitalists who are willing to accept significant risk. Private equity sources typically are risk averse.  Public sources, or public-private partnerships, have been slow to develop an interest in the airship industry. The French airship firm Flying Whales appears to be the first to have gained access to significant funding from public institutions.  
  • Significant regulatory risk: Current US, Canadian and European airship regulations were developed for non-rigid blimps and they fail to address how to certify most of the advanced airships currently under development.  This means that the first airship manufacturers seeking type certificates for advanced airships will face uphill battles as they have to deal with aviation regulatory authorities struggling to fill in the big gaps in their regulatory framework and set precedents for later applicants.  It is incumbent on the aviation regulatory authorities to get updated regulations in place in a timely manner and make the regulatory process predictable for existing and future applicants.  
  • No airship operational infrastructure:  There is nothing existing today that is intended to support the operation of new commercial airships tomorrow.  The early airship operators will need to develop operating bases, hangar facilities, maintenance facilities, airship routes, and commercial arrangements for cargo and passengers.  While many airship manufacturers boast that their designs can operate from unimproved sites without most or all of the traditional ground infrastructure required by zeppelins and blimps, the fact of the matter is that not all advanced airships will be operating from dirt fields and parked outside when not flying.  There is real infrastructure to be built, and this will require a significant investment by the airship operators.
  • Steep learning curve for potential customers:  Only the operators of the Zeppelin NT have experience in operating a modern airship today.  The process for integrating airship operations and maintenance into a customer’s business work flow has more than a few unknowns.  With the lack of modern airship operational experience, there are no testimonials or help lines to support a new customer.  They’ll have to work out the details with only limited support.  Ten years from now, the situation should be vastly improved, but for the first operators, it will be a challenge.
  • Few qualified pilots and crew:  The airship manufacturers will need to work with the aviation regulatory authorities and develop programs for training and licensing new pilots and crew.  The British airship manufacturer Varialift has stated that one of the roles of their ARH-PT prototype will be to train future pilots.  

This uncertain business climate for airships seems likely to change in the mid-to-late 2020s, when several different heavy-lift and passenger airships are expected to be certified by airworthiness authorities and ready for series production and sale to interested customers. If customers step up and place significant orders, we may be able to realize the promise of airship travel and its potential to change our world in many positive ways.

3. Status of current aviation regulations for airships

As noted previously, current aviation regulations have not kept pace with the development of modern airship technology.  In this section, we’ll take a look at the current regulations.

US Federal Aviation Administration (FAA)

In the US, the FAA’s current requirements for airships are defined in the document FAA-P-8110-2, Change 2, “Airship Design Criteria (ADC),” dated 6 February 1995, which is available here:


The ADC applies to non-rigid, near-equilibrium, conventional airships with seating for nine passengers or less, excluding the pilot, and it serves as the basis for issuing the type certificate required before a particular airship type can enter commercial service in the US.  The limited scope of this current regulation is highlighted by the following definitions contained in the ADC:

  • Airship:  an engine-driven, lighter-than-air aircraft, than can be steered.
  • Non-rigid: an airship whose structural integrity and shape is maintained by the pressure of the gas contained within the envelope.
  • Near-equilibrium: an airship that is capable of achieving zero static heaviness during normal flight operations.

Supplementary guidance for non-rigid, near-equilibrium, conventional airships is provided in FAA Advisory Circular (AC) No. 21.17-1A, “Type Certification – Airships,” dated 25 September 1992, which is available here:


The FAA’s ADC and the associated AC were written for blimps, not for the range of modern airships under development today.  For example, aerostatic lift is only one component of lift in modern hybrid airships, which also depend on powered lift from engines and aerodynamic lift during forward flight.  Hybrid airships are not “lighter-than-air” and cannot achieve zero static heaviness during normal operations, yet they are an important class of airships being developed in several countries.  In addition, almost all modern airships, except blimps, have rigid or semi-rigid structures that enable them to carry heavy loads and mount powerful engines on locations other than the gondola of a non-rigid airship.

On March 12, 2012 the FAA announced that Lockheed Martin Aeronautics submitted an application for type certification for their model LMZ1M (LMH-1), which is “a manned cargo lifting hybrid airship incorporating a number of advanced features.”  The FAA assigned that application to their docket number FAA-2013-0550. 

To address the gap in airship regulations head-on, Lockheed Martin submitted to the FAA their recommended criteria document, “Hybrid Certification Criteria (HCC) for Transport Category Hybrid Airships,” which is a 206 page document developed specifically for the LMZ1M (LMH-1).  The HCC is also known as Lockheed Martin Aeronautics Company Document Number 1008D0122, Rev. C, dated 31 January 2013.  You can download the HCC document and related public docketed items on the FAA website here: 


In November 2015, Lockheed Martin announced that the FAA’s Seattle Aircraft Certification Office had approved the project-specific certification plan for the LMZ1M (LMH-1). At the time Lockheed Martin transitioned their hybrid airship business to AT2 Aerospace in May 2023, their hybrid airship had not yet been type certified.

Germany & Netherlands

Recognizing the absence of an adequate regulatory framework for modern airships, civil aviation authorities of Germany and Netherlands developed supplementary guidance to the European Joint Aviation Requirements (JAR-25) and the FAA’s ADC for a category of airships called “Transport Airships,” which they define as follows:

“The transport category is defined for multi-engine propeller driven airships that have a capacity of 20 or more passengers (excluding crew), or a maximum take-off mass of 15,000 kg or more, or a design lifting gas volume of 20,000 m3 or more, whichever is greater.”

These supplementary requirements are contained in the document  “Transport Airship Requirements” (TAR), dated March 2000, which you will find at the following link: https://www.faa.gov/aircraft/air_cert/design_approvals/airships/airships_regs/media/aceAirshipTARIssue1.pdf

European Union Aviation Safety Agency (EASA)

On 11 February 2021, the European Union Aviation Safety Agency (EASA) proposed a new regulatory framework for the certification of large airships.  The proposed document went through a public review and comment period before the final document was issued on 21 January 2022 as Doc. No. SC GAS, “Special Condition ‘SC GAS’ Gas Airships,” which is available here: https://www.easa.europa.eu/downloads/134946/en

EASA explained their rationale for this special condition document:

“EASA has received applications for the type certification of large Airships but has not yet published Certification Specifications (CS) for these products…… In the absence of agreed and published certification specifications for Airships by EASA…….a complete set of dedicated technical specifications in the form of a Special Condition for Gas Airships has been developed. This Special Condition addresses the unique characteristics of Airships and defines airworthiness specifications that may be used to demonstrate compliance with the essential requirements in Annex II of regulation (EU) 2018/1139 of the European Parliament and Council. That is required before the issuance of the EASA type certificate, as well as for the approval of later changes to type certificate.”

“The Special Condition is a high-level set of objective driven and performance-based requirements. It was developed in close cooperation with the industry working group. The Special Condition addresses two designs, one being a 260,000 m3 rigid equilibrium Airship for cargo operations, the other one a 45,000 m3 non-rigid hybrid Airship for up to 100 passengers. However, the authors believe the SC can be applied to all manned Airships with non-pressurized crew or passenger compartments. It will be subject to EASA Certification Team agreement whether this Special Condition can be deemed sufficient as a Certification Basis, for example unmanned designs are not sufficiently addressed by this proposal. Due to the low number of projects no categories have been established. The different safety levels applicable to specific Airship designs will be addressed through the Means of Compliance (MOC).”

The EASA is ahead of the FAA in terms of having published usable interim regulations for advanced airships.  However, both EASA and FAA regulators are lagging the development of advanced civilian airship designs that may be submitted for type certification in the next decade. The lack of mature regulations for advanced airship designs will increase the regulatory risk for the designers / manufacturers of those airships.

4. Lifting gas

In the US, Europe and Canada, the following aviation regulations only allow the use of non-flammable lifting gas:

  • FAA ADC:  “The lifting gas must be non-flammable.” (4.48)
  • TAR:  “The lifting gas must be non-flammable, non-toxic and non-irritant.” (TAR 893)
  • Canadian Air Regulations:  “Hydrogen is not an acceptable lifting gas for use in airships.” (541.7)

The EASA proposed Special Condition issued on 21 January 2022 creates an opportunity to use flammable lifting gases, subject to the following conditions: 

  • SC GAS.2355 Lifting gas system
    • Lifting gas systems required for the safe operation of the Airship must:
      • withstand all loading conditions expected in operation including emergency conditions
      • monitor and control lifting performance and degradation
    • If the lifting gas is toxic, irritant or flammable, adequate measures must be taken in design and operation to ensure the safety of the occupants and people on the ground in all envisaged ground and flight conditions including emergency conditions.
  • SC GAS.2340 Electrostatic Discharge
    • There must be appropriate electrostatic discharge means in the design of each Airship whose lift-producing medium contains a flammable gas to ensure that the effects of electrostatic discharge will not create a hazard.
  • SC GAS.2325 Fire Protection
    • The design must minimize the risk of fire initiation caused by:
      • Anticipated heat or energy dissipation or system failures or overheat that are expected to generate heat sufficient to ignite a fire;
      • Ignition of flammable fluids, gases or vapors; and
      • Fire propagating or initiating system characteristics (e.g. oxygen systems); and
      • A survivable emergency landing.

Without hydrogen, the remaining practical choices for lifting gas are  helium and hot air. A given volume of hot air can lift only about one-third as much as the same volume of helium, making helium the near-universal choice, with hot air being relegated to a few, small thermal airships and larger thermal-gas (Rozière) airships.

The current high price of helium is a factor in the renewed interest in hydrogen as a lifting gas.  It’s also a key selling point for thermal airships.  Most helium is produced as a byproduct from natural gas production, hence, helium is not “rare.” However, only a very small fraction of helium available in natural gas currently is recovered, on the order of 1.25%.  The remainder is released to the atmosphere. The helium recovery rate could be higher, but is not warranted by the current market for helium.  Helium is difficult to store.  The cost of transportation to end-users is a big fraction of the market price of helium.

Hydrogen provides 10% more lift than helium.  It can be manufactured easily at low cost and can be stored.  If needed, hydrogen can be produced with simple equipment in the field.  This could be an important capability for recovering an airship damaged and grounded in a remote region.  One airship concept described in Modern Airships – Part 3, the Aeromodeller II, is designed for using hydrogen as the lifting gas and as a clean fuel (zero greenhouse gases produced) for its propulsion engines.  A unique feature of this airship concept is an on-board system to generate more hydrogen when needed from the electrolysis of water ballast.

A technique for preventing hydrogen flammability is described in Russian patent RU2441685C2, “Gas compound used to prevent inflammation and explosion of hydrogen-air mixtures,” which was filed in 2010 and granted in 2012. This technique appears to be applicable to an airship using hydrogen as its lifting gas.  You can read the patent at the following link: https://patents.google.com/patent/RU2441685C2/en

The Canadian airship firm Buoyant Aircraft Systems International (BASI) is a proponent of using hydrogen lifting gas.  Anticipating a future opportunity to use hydrogen, they have designed their lifting gas cells to be able to operate with either helium or hydrogen.  

Additional regulatory changes will be required to permit the general use of hydrogen in aviation.  With the growing interest in the use of hydrogen fuel in aviation, it seems only a matter of time before it is approved for use as a lifting gas in commercial airships.

Even with the needed regulatory changes, the insurance industry will have to deal with the matter of insuring a hydrogen-filled airship. 

5.  Types of modern airships and aerostats

The term “aerostat” broadly includes all lighter than air vehicles that gain lift through the use of a buoyant gas. Aerostats include unpowered balloons (tethered or free-flying) and powered airships. The following types of airships are described in the Modern Airships series of documents:  

  • Conventional airships
    • Rigid airships
    • Semi-rigid airships
    • Non-rigid airships (blimps)
  • Variable buoyancy airships
    • Variable buoyancy, fixed volume airships
    • Variable buoyancy, fixed volume, variable vacuum airships
    • Variable buoyancy, variable volume airships
    • Variable buoyancy, hybrid thermal-gas (Rozière) airships
    • Variable buoyancy propulsion airships / aircraft
  • Semi-buoyant hybrid air vehicles
    • Semi-buoyant, hybrid airships
    • Semi-buoyant, airplane / airship hybrids (Dynairship, Dynalifter, Megalifter)
    • Semi-buoyant, helicopter / airship hybrids (helistats, Dynastats, rotostats)
  • Stratospheric airships / High-Altitude Platform Stations (HAPS)
  • Personal gas airships
  • Thermal (hot air) airships
  • Hybrid rocket / balloon (Rockoon) airships
  • Electro-kinetically (EK) propelled airships
  • LTA drones
  • Unpowered aerostats
    • Tethered aerostats (kite balloons)
    • Tethered manned aerostats
    • Tethered LTA wind turbines
    • Tethered heavy lift balloons
    • Hybrid tethered aerostat / free-flying powered airships
    • Free-flying high-altitude balloons 
    • Free-flying manned high-altitude balloons 

5.1  Conventional airships

Conventional airships are lighter-than-air (LTA) vehicles that operate at or near neutral buoyancy. The lifting gas (helium) generates approximately 100% of the lift at low speed, thereby permitting vertical takeoff and landing (VTOL) operations and hovering with little or no lift contribution from the propulsion / maneuvering system.  Various types of propulsors may be used for cruise flight propulsion and for low-speed maneuvering and station keeping. 

Airships of this type include rigid zeppelins, semi-rigid airships and non-rigid blimps.

  • Rigid airships: These airships have a lightweight, rigid airframe with an outer skin that defines their exterior shape. The airframe supports the gondola, engines and payload. Most have atmospheric pressure lifting gas cells located within the rigid airframe. A special case is a metal-clad rigid airship, with a metal hull that is self-supporting at atmospheric pressure, but typically operates with a slightly positive internal pressure.
  • Semi-rigid airships:  These airships have a rigid structural framework (i.e., a keel or an internal framework) that supports loads and is connected via a load distribution system to a flexible, pressure-stabilized envelope that defines the exterior shape and typically contains air ballonets.
  • Non-rigid airships (blimps): These airships have a pressure-stabilized, flexible envelope that defines the exterior shape of the airship and typically contains air ballonets. There is no keel or internal structure. Most loads are attached to the gondola and are transferred via a load distribution system to the envelope.

The LTA Research and Exploration Pathfinder 1 and the Flying Whales LCA60T are examples of conventional rigid airships.

The Zeppelin NT and the SkyLifter are examples of conventional semi-rigid airships.

The Aeros 40D Sky Dragon and the American Blimp Corporation MZ-3A (A-170G) are examples of conventional non-rigid airships (blimps).

After being loaded and ballasted before flight, conventional airships have various means to exercise in-flight control over their aerostatic buoyancy, internal pressure and trim. Buoyancy control is exercised with ballast and lifting gas. Internal pressure is controlled with air ballonets and lifting gas vents. Trim is adjusted with the air ballonets or moveable ballast.

Conventional airships with thrust vectoring propulsors have the ability to operate with some degree of net aerostatic heaviness or lightness that can be compensated for with the dynamic thrust (lift or downforce) from the adjustable propulsors.

Controlling buoyancy with ballast  

Many conventional airships require adjustable ballast (i.e., typically water or sand) that can be added or removed as needed to establish a desired net buoyancy before flight.  Load exchanges (i.e., taking on or discharging cargo or passengers) can change the overall mass of an airship and may require a corresponding ballast adjustment during or after the load exchange. 

In-flight use of fuel and other consumables can change the overall mass of an airship.  The primary combustion products of diesel fuel are water and carbon dioxide.  To reduce the loss of mass from fuel consumption, some airships use a rather complex system to recover water from the engine exhaust.  A modern diesel engine water recovery system being developed for the Aerovehicles AV-10 blimp is expected to recover 60% to 70% of the weight of the fuel burned, significantly reducing the change in airship mass during a long mission.

Some Navy blimps and other long-range airships have had a hoist system that could be used in flight to retrieve water from the ocean or any other body of water to increase the amount of on-board ballast.

If an airship becomes heavy, ballast can be dumped in flight to increase aerostatic buoyancy.

Controlling buoyancy with lifting gas  

The lifting gas inside an airship may be at atmospheric pressure (most rigid airships) or at a pressure slightly greater than atmospheric (semi-rigid and non-rigid airships).  Normally, there is no significant loss (leakage) of lifting gas to the environment.  A given mass of lifting gas will create a constant lift force, regardless of pressure or altitude, when the lifting gas is at equal pressure and temperature with the surrounding air. Therefore, a change in altitude will not change the aerostatic lift.  

However, temperature differentials between the lifting gas and the ambient air will affect the aerostatic lift produced by the lifting gas.  To exploit this behavior, some airships can control buoyancy using lifting gas heaters / coolers to manage gas temperature.  

The lifting gas heaters are important for operation in the Arctic, where a cold-soak in nighttime temperatures may result in the lifting gas temperature lagging behind daytime ambient air temperature.  This temperature differential would result in a loss of lift until lifting gas and ambient air temperatures were equal.

Conversely, operating an airship in hot regions can result in the lifting gas temperature rising above ambient air temperature (the lifting gas becomes “superheated”), thereby increasing buoyancy. To restore buoyancy in this case, some airships have coolers (i.e., helium-to-air heat exchangers) in the lifting gas cells to remove heat from the lifting gas.

As described by Boyle’s Law, pressure (P) and gas volume (V) are inversely proportional at a constant temperature according to the following relationship:  PV = K, where K is a constant.  As an airship ascends, atmospheric pressure decreases.  This means that a fixed mass of lifting gas will expand within the lifting gas cells during ascent, and will contract within the lifting gas cells during descent.  As described previously, this lifting gas expansion and contraction does not affect the magnitude of the aerostatic lift as long as the lifting gas is at equal pressure and temperature with the surrounding air.

If an airship is light and the desired buoyancy cannot be restored with lifting gas coolers, it is possible to vent some lifting gas to the atmosphere to decrease aerostatic lift. Usually there are two types of vents: a manually-operated vent controlled by the pilot and an automatically-operated safety vent designed to protect the envelope from overpressure.

Role of the ballonets

The airship hull / envelope is divided into one or more sealed lifting gas volumes and separate gas volumes called “ballonets” that contain air at ambient, or near-ambient pressure. The ballonets serve as the expansion space that is available for the lifting gas cells as the airship ascends.  

The ratio of the total envelope volume to the total ballonet volume is a measure of the expansion space for the lifting gas and is a key factor in determining the airship’s “pressure altitude.” This is the altitude at which the lifting gas cells are fully expanded, and the ballonets are empty. For example, with an envelope volume of 8,255 m3 (290,450 ft3) and a ballonet volume of 2,000 m3 (71,000 ft3), or about 24% of the envelope volume, a Zeppelin NT semi-rigid airship has a reported maximum altitude of 3,000 m (9,842 ft), with the envelope positive pressure of 5 mbar. With a smaller ballonet volume, the Zeppelin NT would have a lower maximum altitude at the specified internal pressure.

In semi-rigid and non-rigid airships with pressure-stabilized hulls, the ballonets are part of the airship’s pressure control system, which automatically maintains the envelope pressure in a desired range. Pressure control is accomplished by changing the volume of the ballonets. An air induction system draws atmospheric air and delivers it at a slight positive pressure (relative to envelope pressure) to increase ballonet volume. An air vent system will discharge air from the ballonets to the ambient atmosphere. While there is a change in mass during these ballonet operations, it is relatively small and does not significantly affect the aerostatic buoyancy of the airship.

Fore and aft ballonets can be operated individually to adjust the trim (pitch angle) of the airship. Inflating only the fore or aft ballonet, and allowing the opposite ballonet to deflate, will make the bow or stern of the airship slightly heavier and change the pitch angle of the airship without significantly affecting the overall aerostatic buoyancy.  These ballonet operating principles are shown in the following diagrams of a blimp with two ballonets, which are shown in blue.

Blimp with two ballonets (blue).  Top diagram shows airship with both ballonets full for level cruise flight at low altitude. The middle diagram shows the forward ballonet full and the aft ballonet empty, creating a slightly nose-heavy condition for descending flight. The bottom diagram shows the forward ballonet empty and the aft ballonet full, creating a slightly tail-heavy condition for ascending flight. Source:  zeppelinfan.de

5.2  Variable buoyancy airships

Variable buoyancy airships can change their net lift, or “static heaviness,” to become lighter-than-air, neutrally buoyant or heavier-than-air as the circumstances require. Basic characteristics of variable buoyancy airships include the following:

  • Variable buoyancy airships are capable of VTOL operations and hovering, usually with a full load.
  • The buoyancy control system may enable in-flight load exchanges from a hovering airship without the need for external ballast.
  • On the ground, variable buoyancy airships can make themselves heavier-than-air to facilitate load exchanges without the need for external infrastructure or ballast.
  • It is not necessary for a “light” airship to vent the lifting gas to the atmosphere.

Variable buoyancy, fixed volume airships

Variable buoyancy commonly is implemented by adjusting the density of the lifting gas or a ballast gas, and thereby changing the static heaviness of a fixed volume airship.  This also is referred to as density-controlled buoyancy (DCB). For example, a variable buoyancy / fixed volume airship can become heavier by compressing the helium lifting gas or ambient air ballast:

  • Compressing some of the helium lifting gas into smaller volume tanks aboard the airship reduces the total mass of helium available to generate aerostatic lift.
  • Compressing ambient air into pressurized tanks aboard the airship adds mass (ballast) to the airship and thus decreases the net lift.

The airship becomes lighter by venting the pressurized gas tanks:

  • Compressed helium lifting gas is vented back into the helium lifting gas cells, increasing the mass of helium available to generate aerostatic lift.
  • Compressed air is vented to the atmosphere, reducing the mass of the airship and thus increasing net lift.

The Aeros Aeroscraft Dragon Dream and the Varilift ARH-50 are examples of variable buoyancy / fixed volume airships.

Variable buoyancy, fixed volume, variable vacuum airships

Instead of using a low-density gas to generate aerostatic lift, a vacuum airship uses very low-density air (a partial vacuum) to generate lift, which can be controlled by managing the vacuum conditions inside lightweight, fixed volume structures capable of retaining the vacuum.  The key challenge is making the variable vacuum containment and associated systems light enough to generate net lift. Once that has been achieved, then the challenge will be to package that variable buoyancy / variable vacuum system into a functional airship. These challenges have been accepted by Anumá Aerospace and by engineer Ilia Toli.

Variable buoyancy, variable volume airships

Variable buoyancy also can be implemented by adjusting the total volume of the helium envelope without changing the mass of helium in the envelope. 

  • As the size of the helium envelope increases, the airship displaces more air and the buoyant force of the atmosphere acting on the airship increases. Static heaviness decreases.
  • As the size of the helium envelope decreases, the airship displaces less air and the buoyant force of the atmosphere acting on the airship decreases.  Static heaviness increases.

The concept for a variable buoyancy / variable volume airship seems to have originated in the mid-1970s with inventor Arthur Clyde Davenport and the firm Dynapods, Inc. The tri-lobe Voliris airships and the EADS Tropospheric Airship are modern examples of variable buoyancy / variable volume airships.

Variable buoyancy, hybrid thermal-gas (Rozière) airships

This buoyancy control concept was developed and applied in the 1700s in hybrid balloons designed by Jean-François Pilâtre de Rozière.  Such “Rozière” balloons have separate chambers for a non-heated lift gas (hydrogen or helium) and a heated lift gas (air).  This concept has been carried over into airships. With helium alone the airship is semi-buoyant (heavier-than-air).  Buoyancy is managed by controlling the heating and cooling of the air in a separate “thermal volume.” Examples of hybrid thermal (Rozière) airships are the British Thermo-Skyship (circa 1970s to early 1980s), Russian Thermoplane ALA-40 (circa 1980s to early 1990s), and the heavy-lift Aerosmena (AIDBA) “aeroplatform” currently being developed in Russia. All are lenticular (lens-shaped) airships.

Variable buoyancy propulsion airships / aircraft

Back in the 1860s, Dr. Solomon Andrews invented the directionally maneuverable, hydrogen-filled airship named Aereon that used variable buoyancy (VB) and airflow around the airship’s gas envelope to provide propulsion without an engine. 

VB propulsion airships / aircraft fly a repeating sinusoidal flight profile in which they gain altitude as positively buoyant hybrid airships, then decrease their buoyancy at some maximum altitude and continue to fly under the influence of gravity as a semi-buoyant glider. After gradually losing altitude during a long glide, the pilot increases buoyancy and starts the climb back to higher altitude in the next cycle.

The UK’s Phoenix and Michael Walden’s HY-SOAR BAT concept are two examples of variable buoyancy propulsion airships / aircraft.

5.3  Semi-buoyant, hybrid air vehicles

Semi-buoyant, hybrid airships

Hybrid airships are heavier-than-air (HTA) vehicles. The term “semi-buoyant” means that the lifting gas provides only a fraction of the needed lift (typically 60 – 80%) and the balance of the lift needed for flight is generated by other means, such as vectored thrust engines and aerodynamic lift from the fuselage and wings during forward flight.

Sources of lift for a semi-rigid, hybrid airship. 
Source: DoD 2012

Basic characteristics of hybrid airships include the following:

  • This type of airship requires some airspeed to generate aerodynamic lift.  Therefore, it typically makes a short takeoff and landing (STOL).  
  • Some hybrid airships may be capable of limited VTOL operations (i.e., when lightly loaded, or when equipped with powerful vectored thrust engines).
  • Like conventional airships, the gas envelope in hybrid airship is divided into one or more lifting gas volumes and separate ballonet volumes containing ambient air. 
  • Hybrid airships are heavier-than-air and are easier to control on the ground than conventional airships.

There are three types of hybrid airships:  non-rigid, semi-rigid and rigid.  

  • Non-rigid hybrid airships:  This type of hybrid airship has a pressure-stabilized, flexible, multi-layer fabric gas envelope that would collapse if the internal pressure were lost. Catenary curtains inside the gas envelope support a gondola and distribute loads into the upper surfaces of the envelope. Ballonets control the pressure inside the gas envelope and can be used to control pitch angle, as on conventional blimps.  The wide hybrid airships may have separate ballonets on each side of the inflated envelope that can be used to adjust the roll angle.  
  • Semi-rigid hybrid airships: This type of hybrid airship has a substantial load-carrying, rigid structure, which may be a large keel or a more complex rigid framework inside the gas envelope, that is connected via a load distribution system to the flexible, pressurized envelope that defines the exterior shape and contains air ballonets.
  • Rigid hybrid airships:  This type of hybrid airship has a substantial rigid structure that defines the shape of the exterior aeroshell. The “hard” skin of the airship may be better suited for operation in Arctic conditions, where snow loads and high winds might challenge the integrity of a pressure-stabilized gas envelope on a non-rigid or semi-rigid airship.  

The AT2 Aerospace Z1 and the HAV Airlander 10 are examples of large hybrid airships that are under development in 2023. Their propulsion engines are attached directly to reinforced areas of the fabric gas envelope and are supported by localized load distribution systems (i.e., distributed cable stays). Their gas envelopes have no rigid internal structures, and in that respect they resemble blimps.

The Lockheed Martin Aerocraft is an example of a semi-rigid hybrid airship with a substantial, load-carrying, internal rigid structure that enabled the designers to support large propulsion engines in locations that may not otherwise be practical.  The AeroTruck being developed by Russian firm Airship-GP is an example of a rigid hybrid airship. The rigid structure is designed for operating in extreme Arctic conditions and parking outdoors where snow loads and icing may be routine problems. Airship-GP also is developing a more complex variable buoyancy model of the AeroTruck.

Semi-buoyant, airplane / airship hybrids

Semi-buoyant airplane / airship hybrids are heavier-than-air, rigid, winged aircraft that carry a large helium volume to significantly reduce the weight of the aircraft and improve its load-carrying capability.  Aerostatic lift provides a smaller fraction of total lift for a semi-buoyant aircraft, like a Dynalifter, than it does for a semi-buoyant, hybrid airship.

A semi-buoyant airplane / airship hybrids behaves much like a conventional aircraft in the air and on the ground, and is less affected by wind gusts and changing wind direction on the ground than a hybrid airship.

The semi-buoyant airplane / airship hybrids has some flexibility for loading and discharging cargo without having to be immediately concerned about exchanging ballast, except in windy conditions.

The Aereon Corporation’s Dynairship and the Ohio Airships Dynalifter are examples of semi-buoyant airplane / airship hybrids.

Semi-buoyant, helicopter / airship hybrids

There have been many different designs of helicopter / airship hybrids, including helistats, Dynastats and rotostats. Typically, the airship part of the hybrid craft carries the weight of the craft itself and helicopter rotors deployed in some manner around the airship work in concert to propel the craft and lift and deliver heavy payloads without the need for an exchange of ballast.

The Piasecki PA-97-34J and the Boeing  / Skyhook International SkyHook JLH-40 are examples of helistats.

5.4 Stratospheric airships / High Altitude Platform Stations (HAPS)

Stratospheric airships are designed to operate at very high-altitudes, well above the jet stream and in a region of relatively low prevailing winds typically found at altitudes of 60,000 to 75,000 feet (11.4 to 14.2 miles / 18.3 to 22.9 km).  This is a harsh environment where airship materials are exposed to the damaging effects of ultraviolet radiation and corrosive ozone.  These airships are designed as unmanned vehicles.

Applications for stratospheric airships include military intelligence, surveillance and reconnaissance (ISR) missions, civil environmental monitoring / resource management missions, military / civil telecommunications / data relay functions, and research missions such as high-altitude astronomy.  All of these can be long term missions that can last weeks, months or even years.

Typically, the stratospheric airship will operate as a “pseudo-satellite” from an assigned geo-stationary position.  Station keeping 24/7 is a unique challenge.  Using a hybrid electric power system, these airships can be solar-powered during the day and then operate from an energy storage source (i.e., a battery or regenerative fuel cell) at night.  Some propulsion systems, such as propellers that work well at lower altitudes, may have difficulty providing the needed propulsion for station keeping or transit in the very low atmospheric pressure at operating altitude.

The DARPA / Lockheed Martin ISIS airship and the Sceye Inc. high-altitude platform are two examples of stratospheric airships.

5.5 Personal gas airships

Personal airships include a range of small LTA craft, from ultra-light, single seat recreational airships (ULM Class 5) to larger airships with a passenger capacity comparable to a personal automobile. Personal airships typically are conventional non-rigid or semi-rigid airships.  They may be powered by various means, including petrol engine, electric motor, or even human-powered. 

The French firm Airstar has built and flown several ultra-light airships, such as the all-electric Electroplume 250. Bryan Allen’s White Dwarf is an example of a pedal-powered personal airship.

5.6  Thermal (hot air) airships

Thermal airships use hot air as the lifting gas in place of helium or hydrogen. A given volume of hot air can lift only about one-third as much as the same volume of helium.  Therefore, the gas envelope on a thermal airship is proportionally larger than it would be on a comparable airship using helium as the lifting gas. 

The non-rigid GEFA-Flug four-seat AS-105GD/4 and six-seat AS-105GD/6, and the semi-rigid, two-seat Skyacht Personal Blimp are examples of current thermal airships that use propane burners to produce the hot air for lift.  Pitch can be controlled with fore and aft burners.  There are no ballonets.

Advanced concepts for solar-powered thermal airships are described in Modern Airships – Part 3.

5.7 Hybrid rocket / balloon (Rockoon) airships

The term “Rockoon” has been used to refer to a ground-launched, high-altitude balloon that carries a small sounding rocket aloft to be launched in the stratosphere, perhaps 15 to 20 miles (24 to 32 km) above the ground. Starting the rocket’s powered flight at high-altitude enables it to reach a much higher altitude than from a conventional ground launch.

Airship designers Michael Walden (LTAS / Walden Aerospace) and John Powell (JP Aerospace) have applied the rocket / balloon hybrid concept more broadly to produce several diverse design concepts for airships capable of operating in the stratosphere, in near-space, and all the way to Earth orbit.

For more than a decade, JP Aerospace has been developing electric / chemical MHD (magnetohydrodynamic) hybrid plasma engines for use in their planned Trans-atmospheric and Orbital Ascender airships.

5.8 Electro-kinetically (EK) propelled airships

EK propulsion uses electrostatic and/or electromagnetic fields to generate thrust, typically a rather low thrust with currently available hardware.  In principle, EK propulsion could be used in place of conventional propulsion means, such as propellers and turbine engines, particularly on airships that operate in the stratosphere. 

EK propulsion has been demonstrated experimentally with small, neutrally-buoyant airships, such as  Michael Walden’s (LTAS / Walden Aerospace) XEM-1 rigid, hybrid EK drive demonstrator that first flew in 1974, and the graceful, non-rigid b-IONIC Airfish that was developed and flown in 2005 by the German firm Festo.  

5.9 LTA drones

LTA drones are uncrewed airships that may be flown by remote control or by onboard control systems with varying degrees of autonomy.  Such drones are being developed worldwide. Many LTA drones are small, conventional, elliptical or cylindrical hull airships. However, other designs, including twin-hull, spherical, lenticular and inflated delta wing have been developed and flown.  Many are all-electric, and some have a photovoltaic solar array to help increase their range and operational flexibility. 

Two examples of modern, autonomous, all-electric LTA drones are the Cloudline cargo drone developed in South Africa and being operationally tested since mid-2023, and Kelluu’s persistent aerial monitoring drone developed and being tested in Finland, along with an information management infrastructure for rapidly delivering processed data to clients.

5.10 Unpowered aerostats

Unpowered aerostats include tethered and free-flying balloons used in a wide variety of applications. These vehicles are not “airships.”

Tethered aerostats (kite balloons)

Many firms offer tethered aerostats for missions such as persistent surveillance and environmental monitoring, with instruments carried on the aerostat to an operating altitudes ranging from of several hundreds to several thousands of meters. The tether may be a simple steel or composite material cable (i.e., Kevlar), or it may be a powered tether that delivers electrical power to aerostat and payload systems and establishes a secure fiber optic data link between the aerostat and its ground station.

Examples are the T-C350 from the French firm A-NSE and the medium volume tethered aerostat from the Israeli firm Atlas LTA Advanced Technology.

Tethered manned aerostats

Tethered manned aerostats commonly are used in two application, as tourist sightseeing balloons and as parachute training balloons. Both applications require flying at relatively low altitude (305 m / 1,000 ft) with up to 30 tourist passengers or 8 – 10 parachute trainees. Spherical balloons are common for tourist flights.  The latest Lindstrand manned aerostat has a more aerodynamic shape, like many unmanned tethered aerostats, and is able to operate in stronger wind conditions than a spherical manned aerostat.

Tethered LTA wind turbines

Tethered buoyant wind turbines operate at altitudes of hundreds to thousands of feet above the ground, where stronger prevailing winds offer more energy for harvesting than at ground level. These tethered aerostats (kite balloons) carry one or more compact, wind-driven electric power generating systems that deliver power via the tether to a substation on the ground, and then onward to a regional electrical grid. 

Two examples that have been tried, but not (yet) commercialized, are the Altaeros Energies BAT and the Magenn Air Rotor System (MARS).

New, but untried airborne wind turbine systems are being developed in 2023 by Aeerstatica Energy Airships and by AirbineTM  Renewable Energy Systems (ARES).

Tethered heavy lifter balloons

Another tethered aerostat application is as a heavy load lifter. In this application, the aerostat may be tethered at a fixed site to function as an heavy lift crane, replacing a conventional construction crane. The tethered aerostat may be designed for a mobile application, lifting a payload and being towed to a delivery site by a vehicle on the ground, a helicopter or by some other means.

Examples are the German CargoLifter AG CL75-AC Air Crane, which flew in 2002, and AirBarge designed by the successor firm, CL Cargolifter GmbH and Co KGaA.

Hybrid tethered aerostat / free-flying powered airships

Some aerostats are designed to operate on a tether and, on command, detach and continue the mission as a free-flying airship.  This hybrid vehicle can operate on station for a long period of time as an tethered aerostat until something of interest is detected.  Then the vehicle detaches and flies away to provide a closeup investigation at the point of interest. 

Examples are the Sanswire / WSGI Argus One Hybrid aerostat / UAV and the Detachable Airship from a Tether (DATT) being developed by UAV Corp.

Free-flying, high-altitude balloons

Free-flying balloons can provide relatively low-cost access to the stratosphere. Zero-pressure balloons can lift large payloads (up to thousands of kilograms) to altitudes up to about 45,000 meters (147,638 ft / 28.0 miles) on missions lasting up to a week. Superpressure balloons can remain aloft much longer than zero-pressure balloons and can be deployed on missions of several months, but with smaller payloads. Several firms offer stratospheric assess with free-flying balloons, including Airstar Aerospace, Aerostar/TCOM, Zero 2 Infinity and JP Aerospace.

Free-flying, manned, high-altitude balloons

There are many firms developing pressurized passenger capsules to carry “space tourists” to altitudes up to about 40 km (25 miles) under very large stratospheric balloons. These flights will include a couple of hours to view the Earth from maximum altitude. After initial descent under the balloon, most of the capsules return to Earth under a parachute or parafoil with a landing on the ground or in the sea. The balloon typically is not recovered.  Full-scale system test flights are expected to begin in 2024, with initial passenger flights by 2025.

6. How does an airship pick up and deliver a heavy load? 

The term “load exchange” refers to the pickup and delivery of cargo by an airship, with or without an exchange of external ballast to compensate for the mass of cargo being moved on or off the airship.  This isn’t a simple problem to solve.

The problem of buoyancy control

In Jeanne Marie Laskas’ article, Igor Pasternak, CEO of airship manufacturer Worldwide Aeros Corp. (Aeros), commented on the common problem facing all airships when a heavy load is delivered:

“The biggest challenge in using lighter-than-air technology to lift hundreds of tons of cargo is not with the lifting itself—the larger the envelope of gas, the more you can lift—but with what occurs after you let the stuff go. ‘When I drop the cargo, what happens to the airship?’ Pasternak said. ‘It’s flying to the moon.’ An airship must take on ballast to compensate for the lost weight of the unloaded cargo, or a ground crew must hold it down with ropes.”

Among the many current designers and manufacturers of large airships, the matter of maintaining the airship’s net buoyancy within certain limits while loading and unloading cargo and passengers is handled in several different ways depending on the type of airship involved.  Some load exchange solutions require ground infrastructure at fixed bases and/or temporary field sites for external ballast handling, while others require no external ballasting infrastructure and instead use systems aboard the airship to adjust buoyancy to match current needs or provide vectored thrust (or suction) to temporarily counteract the excess buoyancy.  The solution chosen for managing airship buoyancy during a load exchange strongly influences how an airship can be operationally employed and where it can pickup and deliver its payload. 

Additional problems for airborne load exchanges

Several current designers and manufacturers of large airships report that their airships will have the ability to conduct airborne load exchanges of cargo from a hovering airship.  Jeremy Fitton, the Director of SkyLifter, Ltd., described the key issues affecting a precision load exchange executed by a hovering airship as follows:

“The buoyancy management element of (an airborne) load-exchange is not the main control problem for airships. Keeping the aircraft in a geo-stationary position – in relation to the payload on the ground – is the main problem, of which buoyancy is a component.”

The matters of precisely maintaining the airship’s geo-stationary position throughout an airborne load exchange and controlling the heading of the airship and the suspended load are handled in different ways depending on the type of airship involved.  The time required to accomplish the airborne load exchange can be many minutes or much longer, depending on the weight of the cargo being picked up or delivered and the time it takes for the airship to adjust its buoyancy for its new loaded or unloaded condition. Most of the airships offering an airborne load exchange capability are asymmetrical (i.e., conventional “cigar shaped” or hybrid aerobody-shaped) and must point their nose into the wind during an airborne load exchange.  Their asymmetrical shape makes these airships vulnerable to wind shifts during the load exchange. The changing cross-sectional area exposed to the wind complicates the matter of maintaining a precise geo-position with an array of vectoring thrusters. 

During such a delivery in variable winds, even with precise geo-positioning over the destination, the variable wind direction may require the hovering airship to change its heading slightly to point into the wind. This can create a significant hazard on the ground, especially when long items, such as a wind turbine blade or long pipe segment are being delivered.  For example, the longest wind turbine blade currently in production is the GE Haliade-X intended for off-shore wind turbine installations.  This one-piece blade is 107 meter (351 ft) long.  A two degree change in airship heading could sweep the long end of the blade more than three meters (10 feet), which could be hazardous to people and structures on the ground.

Regulatory requirements pertaining to load exchanges

The German / Netherlands “Transport Airship Requirements” (TAR), includes the following requirement for load exchanges in TAR 80,  “Loading / Unloading”:

(c) During any cargo exchange…the airship must be capable of achieving a safe free flight condition within a time period short enough to recover from a potentially hazardous condition.”

Similar requirements exist in the EASA proposed Special Conditions published in February 2021, in SC GAS.2125, “Loading / Unloading.”

These requirements will be a particular challenge for airships designed to execute an airborne load exchange from a hovering airship.

The CargoLifter approach to an airborne load exchange

One early approach for delivering a load from a hovering airship was developed for the CargoLifter CL160.  As described on the Aviation Technology website (https://www.aerospace-technology.com/projects/cargolifter/), the CL160 would have performed an in-flight delivery of cargo as follows:

“The airship hovers at about 100 m above the ground and a special loading frame, which is fixed during flight to the keel of the airship, is then rigged with four cable winches to the ground, a procedure which is to assure that the airship’s lifting gear stays exactly above the desired position. Ballast water is then pumped into tanks on the frame and the payload can be unloaded. The anchor lines are released and the frame is pulled back into the payload bay of the airship.”

In a 2002 test using the heavy-lift CargoLifter CL75 aerostat as an airship surrogate, a 55 metric ton German mine-clearing tank was loaded, lifted and discharged from the loading frame as water ballast was unloaded and later reloaded in approximately the same time it took to secure the tank in the carriage (several minutes).  In this test, the 55 metric tons cargo was exchanged with about 55 cubic meters (1,766 cubic feet, 14,530 US gallons) of water ballast.

The SkyLifter approach to an airborne load exchange

One airship design, the SkyLifter, addresses the airborne load exchange issues with a symmetrical, disc-shaped hull that presents the same effective cross-sectional area to a wind coming from any direction.  With the aid of cycloidal propellers, his airship is designed to move equally well in any direction (omni-directional), simplifying airship controls in changing wind conditions, and likely giving the SkyLifter an advantage over other designs in maintaining a precise geolocation above a site while conducting an airborne load exchange without the need for the system of ground tethers used by the CL160

Source: Skylifter (now Luffships Ltd.)

You’ll find more information on airship load exchange issues in a December 2017 paper by Charles Luffman, entitled, “A Dissertation on Buoyancy and Load Exchange for Heavy Airships (Rev. B)”, which is available at the following link:  https://www.luffships.com/wp-content/uploads/2018/02/buoyancy_and_load_exchange.pdf

7.  The scale of large cargo airships

Some of the advanced airship concepts being developed, especially for future heavy-lift cargo carriers, will result in extremely large air vehicles on a scale not seen since the heyday of the giant zeppelins in the 1930s.  Consider the following semi-rigid hybrid airships shown to scale with contemporary US Air Force fixed-wing cargo aircraft.

Size comparison for hybrid airships sized for various lift applications.  
Source: DoD 2012

8.  Graphic tables

The airships and aerostats reviewed in Modern Airships – Part 1 are summarized in the following set of graphic tables that are organized into the airship type categories listed below: 

  • Conventional airships
    • Rigid airships
    • Semi-rigid airships
    • Non-rigid airships (blimps)
  • Variable buoyancy airships
    • Variable buoyancy, fixed volume airships
  • Semi-buoyant hybrid air vehicles
    • Semi-buoyant, hybrid airships
    • Semi-buoyant, airplane / airship hybrids (Dynairship, Dynalifter, Megalifter)
    • Semi-buoyant, helicopter / airship hybrids (helistats, Dynastats, rotostats)
  • Stratospheric airships / High-Altitude Platform Stations (HAPS)
  • Personal gas airships
  • Hybrid rocket / balloon (Rockoon) airships
  • LTA drones
  • Unpowered aerostats
    • Tethered aerostats (kite balloons)
    • Tethered manned aerostats
    • Tethered heavy lift balloons
    • Free-flying high-altitude balloons
    • Free-flying manned high-altitude balloons 

Within each category, each page of the table is titled with the name of the airship type category and is numbered (P1.x), where P1 = Modern Airships – Part 1 and x = the sequential number of the page in that category.  For example, “Conventional, rigid airships (P1.2)” is the page title for the second page in the “Conventional, rigid airships” category in Part 1.  There also are conventional, rigid airships addressed in Modern Airships – Part 2. Within a category, the airships are listed in the graphic tables in approximate chronological order.

Links to the individual Part 1 articles on these airships are provided in Section 10.  Some individual articles cover more than one particular airship. Have fun exploring!

9. Assessment of near-term LTA market prospects

Among the new airships described in Part 1, the following advanced airship seems to be the best candidate for achieving type certification in the next five years:

  • LTA Research and Exploration (USA): Pathfinder 1 rigid airship, which is expected to make its first flight in 2024. The program appears to be well funded. 

The following airship manufacturers in Part 1 have advanced designs and they seem to be ready to manufacture a first commercial prototype if they can arrange adequate funding: 

  • AT2 Aerospace (USA): Their Z1 hybrid airship formerly was known as the Lockheed Martin LMH-1. In May 2023, Lockheed Martin exited the hybrid airship business without completing type certification and transitioned that business, including intellectual property and related assets, to the newly formed, commercial company ATAerospace.  In June, Straightline Aviation (a former LMH-1 customer) signed a Letter of Intent with ATAerospace, signaling commercial support for the Z1 hybrid airship.  
  • Aeros (USA): It seems that Aeros has been ready for more than a decade to begin type certification and manufacture a prototype of their Aeroscraft ML866 / Aeroscraft Gen 2 variable buoyancy / fixed volume airship.  The firm has reported successful subsystem tests.

Recent changes in European aviation regulations reduce some of the regulatory uncertainty for advanced airship type certification in the EU. The US FAA has not yet published comparable guidance for advanced airships, resulting in continuing regulatory uncertainty in the USA.

The promising airships in Part 1, as listed above, will be competing in the worldwide airship market with candidates identified in Modern Airships – Part 2, which potentially could enter the market in the same time frame. Among the airships described in Part 2, the following advanced airship seems to be the best candidate for achieving type certification in the next five years:

  • Flying Whales (France): The LCA60T rigid cargo airship was significantly redesigned in 2021, which resulted in a considerable schedule delay. In March 2023, Flying Whales reported that they expected to complete construction and flight testing of the first production prototype in the 2024 – 2025 timeframe, followed by EASA certification and start of industrial production in 2026.  The project appears to be well funded from diverse international sources in France, Canada, China and Morocco. Full-scale production facilities are planned in France, China and Canada and commercial airship operating infrastructure is being planned.
  • Hybrid Air Vehicles (UK): The Airlander 10 commercial passenger / cargo hybrid airship is being developed by HAV  based on their experience with the Airlander 10 prototype, which flew from 2016 to 2017. In 2022, Valencia, Spain-based Air Nostrum, which operates regional flights, ordered 10 Airlander 10 aircraft, with delivery scheduled for 2026. Also in 2022, Highlands and Islands Airport (HIAL) sponsored a study for introducing the Airlander 10 in Scotland. In April 2023, the regional UK government of South Yorkshire concluded a financial agreement that is expected to lead to the Airlander 10 being manufactured in Doncaster, in the north of England.  Things are moving in the right direction. However, FutureFlight reported that “the plan cannot proceed unless HAV secures a strategic investor. It needs at least £100 million to begin construction.”

The following airship manufacturers in Part 2 have advanced designs and they seem to be ready to manufacture a first prototype if they can arrange funding: 

  • Aerovehicles (USA / Argentina): They claim their AV-10 non-rigid, multi-mission blimp can carry a 10 metric ton payload and be type certified within existing regulations for blimps. This should provide a lower-risk route to market for an airship with an operational capability that does not exist today.
  • Atlas LTA Advanced Technology (Israel): After acquiring the Russian firm Augur RosAeroSystems in 2018, Atlas is continuing to develop the ATLANT variable buoyancy, fixed volume heavy lift airship.  They also are developing a new family of non-rigid Atlas-6 and -11 blimps and unmanned variants.  However, the development plans and schedules have not yet been made public.
  • BASI (Canada): The firm has a well-developed design in the MB-30T and a fixed-base operating infrastructure design that seems to be well suited for their primary market in the Arctic.
  • Euro Airship (France):  The firm reports having production-ready plans for their rigid airship designs. In June 2023, Euro Airship announced plans to build and fly a large rigid airship known as Solar Airship One around the world in 2026.
  • Millennium Airship (USA & Canada): The firm has well developed designs for their SF20T and SF50T SkyFreighters, has identified its industrial team for manufacturing, and has a business arrangement with SkyFreighter Canada, Ltd., which would become a future operator of SkyFreighter airships in Canada.  In addition, their development plan defines the work needed to build and certify a prototype and a larger production airship.

The 2020s will be an exciting time for the airship industry.  We’ll finally get to see if the availability of several different heavy-lift airships with commercial type certificates will be enough to open a new era in airship transportation. Aviation regulatory agencies need to help reduce investment risk by reducing regulatory uncertainty and putting in place an adequate regulatory framework for the wide variety of advanced airships being developed.  Customers with business cases for airship applications need to step up, place firm orders, and then begin the pioneering task of employing their airships and building a worldwide airship transportation network with associated ground infrastructure.  This will require consistent investment over the next decade or more before a basic worldwide airship transportation network is in place to support the significant use of commercial airships in cargo and passenger transportation and other applications. Perhaps then we’ll start seeing the benefits of airships as a lower environmental impact mode of transportation and a realistic alternative to fixed-wing aircraft, seaborne cargo vessels and heavy, long-haul trucks.

10.  Links to the individual articles

The following links will take you to the individual Modern Airships – Part 1 articles.  The organization of the following list matches the graphic table.

Note that several of these articles address more than one airship design from the same manufacturer / designer and they may be in different categories (i.e., Airship Industries, Ohio Airships, Walden Aerospace). These designs are listed separately in the above graphic tables and in the following index. The links listed below will take you to the correct article.


Conventional, rigid:

Conventional, semi-rigid airships:

Conventional, non-rigid airships (blimps):


Variable buoyancy, fixed volume airships:


Semi-buoyant hybrid airships:

Semi-buoyant airplane / airship hybrids:

Helicopter / airship hybrids:







Tethered aerostats (Kite balloons)

Tethered, heavy lift balloons:

Free-flying, high-altitude balloons:

Free-flying, manned, high-altitude balloons:

  • EosX – stratospheric passenger balloons: Coming in 2024
  • HaloSpace – stratospheric passenger balloons: Coming in 2024
  • Iwaya Giken – stratospheric passenger balloons: Coming in 2024
  • Space Perspective – stratospheric passenger balloons: Coming in 2024
  • StratoFlight – stratospheric passenger balloons: Coming in 2024
  • World View Enterprises Inc – stratospheric passenger balloons: Coming in 2024
  • Zephalto – stratospheric passenger balloons: Coming in 2024
  • Zero 2 Infinity – Bloon stratospheric passenger balloons: Coming in 2024