Tag Archives: Walden Aerospace

Modern Airships – Part 1

Peter Lobner, updated 8 March 2022 (Rev. 5)

1. Introduction

Modern Airships is a three-part document that contains an overview of modern airship technology in Part 1 and links in Parts 1, 2 and 3 to more than 225 individual articles on historic and advanced airship designs.  This is Part 1.  Here are the links to the other two parts:

You’ll find a consolidated Table of Contents for all three parts at the following link.  This should help you navigate the large volume of material in the three documents.

Modern Airships – Part 1 begins with an overview of modern airship technology, continues with a summary table identifying the airships addressed in this part, and concludes by providing links to 91 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:  PL31416@cox.net.

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 March 2022

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.  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. Part 1 now has 91 articles.

Since Rev. 5 was posted, the following additions and updates have been made in Part 1.

New articles:

  • ISL Aeronautical & Space Systems (formerly Bosch Aerospace Inc.) – UAV blimps and tethered aerostats (12 June 2022)

Updated articles:

  • LTA Research and Exploration – rigid airships (24 July 2022)

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

For more than two 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 August 2021, 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, detailed designs, the first to secure adequate funding will be able to take the next steps to build a manufacturing facility and a full-scale prototype airship, complete the airship certification process, and start offering a certified airship for sale.

There are some significant roadblocks in the way:

  • No full-scale prototypes are flying:  The 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.
  • Immature manufacturing capability:  While the airship industry has been good at developing many advanced designs, some existing 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.  Several years ago, 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 early 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:

https://www.faa.gov/aircraft/air_cert/design_approvals/airships/airships_regs/media/aceAirshipDesignCriteria.pdf

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:

https://www.faa.gov/documentlibrary/media/advisory_circular/ac_21-17-1a.pdf

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: 

https://www.regulations.gov/docket/FAA-2013-0550/document

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). Since then, nothing new has been posted on the docket.

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 (Rozier) 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

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 aerostats are described in the Modern Airships series of documents:  

  • Conventional airships
    • Rigid airships
    • Semi-rigid airships
    • Non-rigid airships (blimps)
  • Semi-buoyant hybrid airships 
  • Semi-buoyant hybrid aircraft (Dynairship, Dynalifter, Megalifter)
  • Variable buoyancy airships
    • Variable buoyancy / fixed volume airships
    • Variable buoyancy / variable volume airships
    • Variable buoyancy propulsion airships / aircraft        
  • Helicopter / airship hybrids (helistats, Dynastats, rotostats)
  • Stratospheric airships  
  • Thermal (hot air) airships
  • Hybrid thermal-gas (Rozier) airships
  • Rocket / balloon (Rockoon) hybrid airships
  • Unpowered aerostats

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 (zeppelins): These airships have a lightweight, rigid airframe that defines their exterior shape.  This airframe supports the gondola, engines and payload.  Most have atmospheric pressure lifting gas cells and air ballonets located within the rigid airframe. A special case is a metal-clad rigid airship, where the metal hull is a pressurized lift gas container.
  • Semi-rigid airships:  These airships have a rigid structural framework that supports loads and is connected via a load distribution system to the flexible, pressurized envelope that defines the exterior shape and contains air ballonets.
  • Non-rigid airships (blimps): These airships have a pressurized flexible envelope that defines the exterior shape of the airship. Most loads are attached to the gondola and are transferred via a load distribution system to the envelope.

The Euro Airship DGPAtt 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 SAIC Skybus 80K are examples of conventional non-rigid airships.

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  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 two types of hybrid airships:  semi-rigid and rigid.  

  • Semi-rigid hybrid airships:  These airships have a structural keel or spine to carry loads, and a large, lifting-body shaped inflated fuselage containing the lifting gas cells and ballonets.  Operation of the ballonets to adjust net buoyancy and pitch angle is similar to their use on conventional airships.  These wide hybrid airships may have separate ballonets on each side of the inflated envelope that can be used to adjust the roll angle.  While these airships are heavier-than-air, they generally require adjustable ballast to handle a load exchange involving a heavy load.
  • Rigid hybrid airships:  These airships have a more substantial 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 an inflated fuselage of a semi-rigid airship.  Otherwise, the rigid hybrid airship behavior is similar to a semi-rigid airship. 

The Lockheed-Martin LMH-1 is an example of a semi-rigid hybrid airship.  The AeroTruck being developed by Russian firm Airship-GP is an example of a rigid hybrid airship.

5.3  Semi-buoyant hybrid aircraft

Semi-buoyant aircraft 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 aircraft 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 aircraft 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 aircraft.

5.4  Variable buoyancy airships

Variable buoyancy airships can change their net lift, or “static heaviness,” to become LTA or HTA 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 net lift of a fixed volume airship.  For example, a variable buoyancy / fixed volume airship can become heavier by compressing the helium lifting gas or ambient air:

  • 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 tanks:

  • Compressed helium lifting gas is vented back into the helium lift 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 / 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 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.

5.5  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.

5.6 Stratospheric airships

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.

5.7 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.

5.8  Hybrid thermal-gas (Rozier) airships

This buoyancy control concept was developed and applied in the 1700s in hybrid balloons designed by Jean-François Pilâtre de Rozier.  Such “Rozier” 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 (Rozier) 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.

5.9 Rocket / balloon (Rockoon) hybrid 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.

Michael Walden’s Silver Dart stratospheric airship shuttle (L) and 
W.A.V.E.S. manned sub-orbital rocket / airship vehicle (R).
Source: Walden Aerospace
John Powell’s Mach Glider launched from a high-altitude airship (L) and an Orbital Ascender airship slowly accelerating from the stratosphere into orbit (R). Source: JP Aerospace

5.10 Unpowered aerostats

Unpowered aerostats include tethered and free-flying balloons used in a wide variety of applications.  Many firms offer tethered aerostats for missions such as persistent surveillance and environmental monitoring, with instruments carried on the aerostat to an altitude of several hundreds or thousands of feet (meters), with power and a data link provided via the tether. 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.

A-NSE’s T-C350 tethered aerostat (L) and the Atlas medium volume aerostat (R). Sources: A-NSE & Atlas

Another tethered aerostat application is as a heavy load lifter. In this application, the aerostat is designed to lift a payload and be towed to a delivery site by a vehicle on the ground, a helicopter or by some other means. Examples are the German CargoLifter CL75-AC Air Crane and the Russian aero barge designed by Novosibirsk OKB.

CL75-AC load test (L) and Novosibirsk OKB aero barge concept (R).
Sources:  CargoLifter & Boyko (2001)

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 Hybrid aerostat / UAV and the Detachable Airship from a Tether (DATT) being developed by UAV Corp.

Argus One (L) and DATT (R).
Sources: Sanswire / WSGI & UAV Corp

Yet another application is as a vehicle for access to the stratosphere. JP Aerospace has flown more that 130 civilian stratospheric balloon missions carrying small, low-cost research packages and other payloads.  The firms World View Enterprises, Inc. and Space Perspective are developing very large stratospheric balloons as vehicles to carry “space tourists” to maximum altitude of about 25 miles (40 km) and return them safely to the ground, with flights starting in this decade.

JP Aerospace high altitude balloon, Away Mission 130, 16 July 2020 (L) and rendering of a World View manned tourism balloon (R). Sources: JP Aerospace & World View.

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.  This 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 conducting a precision airborne load exchange.

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. Specific airships in Part 1

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

  • Conventional rigid airships
  • Conventional semi-rigid airships
  • Conventional non-rigid airships (blimps)
  • Variable buoyancy, fixed volume airships
  • Variable buoyancy, variable volume airships
  • Helicopter / airship hybrids
  • Semi-buoyant hybrid aircraft
  • Semi-buoyant hybrid airships
  • Stratospheric airships
  • Thermal (hot air) airships
  • Rocket / balloon (Rockoon) hybrid airships
  • LTA drones
  • Unpowered aerostats

Within each category, each page of the table is titled with the name of the 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, “Stratospheric airships (P1.2)” is the page title for the second page in the “Stratospheric airships” category in Part 1.  There also are stratospheric 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 9.  Some individual articles cover more than one particular airship.

Among the new airships described in Part 1, the following advanced airships seem to be the best candidates 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 2022. The program appears to be well funded. 
  • Lockheed Martin (USA): LMH-1 hybrid airship, which has been in the FAA certification process for several years. However, Lockheed Martin has not reported on its certification progress or its schedule for flying a first prototype.

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

  • Aeros (USA): Aeroscraft ML866 / Aeroscraft Gen 2 variable buoyancy / fixed volume airship
  • Hybrid Air Vehicles (UK): Production prototype of the Airlander 10 hybrid airship
  • Voliris (France): V932 NATAC & SeaBird semi-buoyant, inflated wing airships

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 airship was significantly redesigned in 2021, which resulted in a schedule delay for completing the first prototype until 2024.  However, 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.

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.
  • Aerosmena (AIDBA, Russia): The firm offers the latest designs for heavy-lift hybrid thermal (Rozier) “aeroplatforms,” which use two lift gases: helium and heated air.  The A20 will be the prototype for the entire family of Aerosmena aeroplatform.
  • 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.
  • Egan Airships (USA): PLIMP Model J plane / blimp hybrid based on a flying unmanned prototype.
  • Euro Airship (France):  The firm claims that production-ready drawings exist for their Corsair and the larger DGPAtt.  
  • 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.
  • Solar Ship (Canada): 24-meter Caracal light cargo semi-buoyant airship and the Wolverine medium cargo semi-buoyant aircraft.
  • Varialift (UK):  The factory in France and the ARH-PT prototype are under construction, but the schedule for completing the prototype has slipped, perhaps by three years to 2022, primarily because of tenuous funding. Without a stronger funding stream, the future schedule is unpredictable.

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.

9.  Links to the individual articles

The following links will take you to the 91 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 airships:

Conventional, semi-rigid airships:

Conventional, non-rigid airships (blimps):

Variable buoyancy, fixed volume airships:

Variable buoyancy, variable volume airships:

Helicopter / airship hybrids:

Semi-buoyant hybrid aircraft:

Semi-buoyant hybrid airships:

Stratospheric airships:

Rocket / balloon (Rockoon) hybrid airships:

Thermal (hot air) airships:

LTA drones:

Unpowered Aerostats:

Modern Airships – Part 3

Peter Lobner, updated 18 March 2022 (Rev. 3)

1. Introduction

“Modern Airships” is a three-part document that contains an overview of modern airship technology in Part 1 and links in Parts 1, 2 and 3 to more than 225 individual articles on historic and advanced airship designs.  This is Part 3.  Here are the links to the other two parts:

You’ll find a consolidated Table of Contents for all three parts at the following link.  This should help you navigate the large volume of material in the three documents.

Modern Airships – Part 3 begins with a summary table identifying the airship concepts addressed in this part, and concludes by providing links to 49 individual articles on these airship concepts. A downloadable pdf copy of Part 3 is available here:

If you have any comments or wish to identify errors in these documents, please send me an e-mail to:  PL31416@cox.net.

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

18 March 2022

Record of revisions to Part 3

  • 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 3 included 32 linked articles.
  • Part 3, Revision 1, 21 December 2020: Added 1 new article on Walden Aerospace. Part 3 now had 33 articles
  • Part 3, Revision 2, 8 February 2022: Added 14 new articles, moved over and updated the Halo article from Part 1 and updated 11 of the original articles. Part 3 now had 48 articles.
  • Part 3, Revision 3, 18 March 2022: Added 1 new article, reorganized the graphic table and updated 22 of the original articles. With this revision, all Part 3 linked articles have been updated in February or March 2022. Part 3 now has 49 articles.

2. Specific airship concepts in Part 3

The airships described in Modern Airships – Part 3 are relatively exotic concepts in comparison to the more utilitarian and heavy-lift airships that dominate Parts 1 and 2.  Many of the airship concepts in Part 3 are designed for operation with very low or zero carbon emissions.  

The airship design concepts reviewed in Modern Airships – Part 3 are summarized in the following set of graphic tables.  I’ve grouped these airship concepts based on their applications rather than on their design / type (as in Parts 1 and 2) because those details sometimes are difficult to determine when few graphics and limited descriptions are available.  

  • Cargo & multi-purpose airships
  • Mass transportation airships
  • Flying hotel airships
  • Touring airships
  • Flying yacht airships
  • Autonomous special purpose airships
  • Personal airships
  • Thermal (hot air) airships
  • Biomimetic airships
  • Rocket / airship (Rockoon) hybrids

Within each category, each page of the table is titled with the name of the category and is numbered (P3.x), where P3 = Modern Airships – Part 3 and x = the sequential number of the page in that category.  For example, “Flying hotel airships (P3.2)” is the page title for the second page in the “Flying hotel airships” category in Part 3.  Within each category, the airships are listed in an approximate chronological order.

Except for a few sub-scale models, none of the airship concepts in Part 3 have flown.  A few of these airships look good as concepts, but may be impossible to build.  Nonetheless, all of these relatively exotic concepts point toward an airship future that will benefit from the great creativity expressed by these designers.

Links to the individual Part 3 articles on these airships are provided in Section 3.  Some individual articles cover more than one particular airship.

3. Links to the individual articles

The following links will take you to 49 individual articles.  

Note that a few of these articles address more than one airship design concept from the same designer and these airship concepts may be in different categories (i.e., Avalon Airships, Bauhaus Luftfahrt, Walden Aerospace). Each design concept is listed separately in the above graphic tables and in the following index. The links listed below will take you to the same article.

Cargo & multi-purpose airships

Mass transportation airships:

Flying hotel airships:

Touring airships:

Flying yacht airships:

Remotely-piloted special purpose airships:

Personal airships:

Thermal (hot air) airships:

Biomimetic airships:

Rocket / airship hybrids:

Modern Airships – Part 2

Peter Lobner, updated 10 March 2022 (Rev. 5)

1. Introduction

Modern Airships is a three-part document that contains an overview of modern airship technology in Part 1 and links in Parts 1, 2 and 3 to 230 individual articles on historic and advanced airship designs.  This is Part 2.  Here are the links to the other two parts:

You’ll find a consolidated Table of Contents for all three parts at the following link.  This should help you navigate the large volume of material in the three documents.

Modern Airships – Part 2 begins with a summary graphic table identifying the airships addressed in this part, and concludes by providing links to 91 individual articles on those airships.  A downloadable pdf copy of Part 2 is available here:

Each of the linked articles can be individually downloaded.

If you have any comments or wish to identify errors in these documents, please send me an e-mail to:  PL31416@cox.net.

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

10 March 2022

Record of revisions to Part 2

  • 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 2 included 25 articles
  • Part 2, Revision 1, 21 December 2020: Added 2 new articles on Walden Aerospace. Part 2 now had 27 articles
  • Part 2, Revision 2, 3 April 2021: Added 35 new articles, split the original variable buoyancy propulsion article into three articles, and updated all of the original articles. Also updated and reformatted the summary graphic table.  Part 2 now had 64 articles.
  • Part 2, Revision 3, 9 September 2021:  Updated 7 articles. Added category for “thermal (hot air) airships” and added pages for them in the summary graphic table. Part 2 still had 64 articles.
  • Part 2, Revision 4, 11 February 2022: Added 26 new articles, expanded the graphic tables and updated 12 existing articles. Part 2 now had 90 articles.
  • Part 2, Revision 5, 10 March 2022: Added 1 new article, split rigid & semi-rigid airships in the graphic tables, and updated 52 existing articles. With this revision, all Part 2 linked articles have been updated in February or March 2022. Part 2 now has 91 articles.

Since Rev. 5 was posted, the following additions and updates have been made in Part 2.

New articles:

  • Aere Airships (22 July 2022)
  • China – Hybrid airship for airborne electromagnetic (AEM) surveying (15 June 2022)
  • Strasa.Tech – HAPS platforms (30 May 2022)

Updated articles:

  • Atlas LTA Advanced Technology, Ltd. (2 June 2022)

2. Specific airships in Part 2

The airships reviewed in Modern Airships – Part 2 are summarized in the following set of graphic tables that are organized into the categories listed below: 

  • Conventional rigid airships
  • Conventional semi-rigid airships
  • Conventional non-rigid airships (blimps)
  • Semi-buoyant hybrid airships
  • Semi-buoyant hybrid aircraft
  • Hybrid thermal (Rozier) airships
  • Thermal (hot air) airships
  • Variable buoyancy, fixed volume airships
  • Variable buoyancy, variable volume airships
  • Variable buoyancy propelled airships
  • Stratospheric airships
  • Electro-kinetically (EK) propelled airships
  • LTA drones
  • Unpowered aerostats

Within each category, each page of the table is titled with the name of the category and is numbered (P2.x), where P2 = Modern Airships – Part 2 and x = the sequential number of the page in that category.  For example, “Stratospheric airships (P2.2)” is the page title for the second page in the “Stratospheric airships” category in Part 2.  There also are stratospheric airships addressed in Modern Airships – Part 1.

Links to the individual Part 2 articles on these airships are provided in Section 3.  Some individual articles cover more than one particular airship.

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 airship was significantly redesigned in 2021, which resulted in a schedule delay for completing the first prototype until 2024.  However, 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.

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.
  • Aerosmena (AIDBA, Russia): The firm offers the latest designs for heavy-lift hybrid thermal (Rozier) “aeroplatforms,” which use two lift gases: helium and heated air.  The A20 will be the prototype for the entire family of Aerosmena aeroplatform.
  • 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.  Their development plans and schedules have not yet been made public.
  • BASI (Canada): The firm has a well-developed rigid airship 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 claims that production-ready drawings exist for their Corsair and the larger DGPAtt rigid airships.  
  • 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.
  • Varialift (UK):  The factory in France and the ARH-PT prototype are under construction, but the schedule for completing the prototype has slipped, perhaps by three years to 2022, primarily because of tenuous funding. Without a stronger funding stream, the future schedule is unpredictable.

The promising airships in Part 2, listed above, will be competing in the worldwide airship market with candidates identified in Modern Airships – Part 1, which potentially could enter the market in the same time frame. Among the new airships described in Part 1, the following advanced airships seem to be the best candidates 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 2022. The program appears to be well funded. 
  • Lockheed Martin (USA): LMH-1 hybrid airship, which has been in the FAA certification process for several years. However, Lockheed Martin has not reported recently on its certification progress or its updated schedule for flying a first prototype. 

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

  • Aeros (USA): Aeroscraft ML866 / Aeroscraft Gen 2 variable buoyancy / fixed volume airship.
  • Hybrid Air Vehicles (UK): Production prototype of the Airlander 10 hybrid airship.
  • Voliris (France): V932 NATAC & SeaBird semi-buoyant, inflated wing airships.

For decades, there have been many ambitious projects that intended to operate an airship as a pseudo-satellite, carrying a heavy payload while maintaining a geo-stationary position in the stratosphere on a long-duration mission (days, weeks, to a year or more).  None were successful.  This led NASA in 2014 to plan the 20-20-20 airship challenge: 20 km altitude, 20 hour flight, 20 kg payload.  The challenge never occurred, but it highlighted the difficulty of developing an airship as a persistent pseudo-satellite.  The most promising new stratospheric airship manufacturers identified in Part 2 are:

  • Sceye Inc. (USA):  This small firm is developing and, since 2017, has been flight testing mid-size, multi-mission stratospheric airships. The firm also has built a new headquarters and manufacturing facility in New Mexico. Short-duration stratospheric communications system flight tests were conducted in 2021. A long duration test should be coming soon.
  • Thales Alenia Space (France): The firm is developing the multi-mission Stratobus.  Their latest round of funding from France’s defense procurement agency calls for a full-scale, autonomous Stratobus demonstrator airship to fly by the end of 2023, five years later than another demonstrator that was ordered in the original 2016 Stratobus contract, but not built. Time will tell if Thales Alenia Space can meet the new schedule with the available funding.

China remains an outlier after the 2015 flight of the Yuanmeng stratospheric airship developed by  Beijing Aerospace Technology Co. & BeiHang.  The current status of the Chinese stratospheric airship development program is not described in public documents.

Among the many smaller airships identified in Part 2, the following manufacturers could have their airships flying by the mid 2020s if adequate funding becomes available.

  • Dirisolar (France): The firm has a well-developed design for their five passenger DS 1500, which is intended initially for local air tourism, but can be configured for other missions.  When funding becomes available, it seems that they’re ready to go.
  • A-NSE (France):  The firm offers a range of aerostat and small airships, several with a novel tri-lobe, variable volume hull design.  Such aerostats are operational now, and a manned tri-lobe airship could be flying later in the 2020s.
  • Egan Airships (USA):  The PLIMP Model J drone has already flown. When funding becomes available, their Model J plane / blimp hybrid seems ready to go.
  • Solar Ship (Canada): The firm’s Caracal prototype semi-buoyant, inflated wing airship has already flown successfully but the production version, the 24-meter Caracal, has not yet received CAA or FAA certification.  That basic inflated wing design did not scale up successfully for the Wolverine. Hence, the larger Wolverine has been redesigned as a significantly different semi-buoyant aircraft.  Solar Ship has not published their current development and certification schedules.

There seems to be a proliferation of small LTA drone blimps and other small LTA drone vehicles.  Some were developed initially for military surveillance applications, but all are configurable and could be deployed in a range of interesting applications. Some enterprising LTA drone developers also are developing value-adding applications and are offering information services, rather than simply selling a drone to be operated by a customer.

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.

3. Links to the individual articles

The following links will take you to 91 individual articles that address all of the airships identified in the preceding graphic table.

Note that a few of these articles address more than one airship design from the same manufacturer / designer and they may be in different categories (i.e., Augur RosAeroSystems, Atlas LTA Advanced Technology). These designs are listed separately in the above graphic tables and in the following index. The links listed below will take you to the same article.

Conventional rigid airships:

Conventional semi-rigid airships:

Conventional non-rigid airships (blimps):

Semi-buoyant hybrid airships:

Semi-buoyant plane / airship hybrids:

Variable buoyancy, fixed volume airships:

Variable buoyancy, variable volume airships:

Variable buoyancy propulsion airships:

Hybrid thermal (Rozier) airships:

Thermal (hot air) airships:

Helicopter / airship hybrids:

Stratospheric airships:

Electro-kinetically (EK) propelled airships:

Personal airships:

LTA drones:

Unpowered aerostats:

Riding the Phantom Zephyr

Peter Lobner, updated 21 February 2021

1.  Background

When charged molecules in the air are subjected to an electric field, they are accelerated. When these charged molecules collide with neutral ones, they transfer part of their momentum, leading to air movement known as an “ionic wind.”  This basic process is shown in the following diagram, which depicts a strong electric field between a discharge electrode (left) and a ground electrode (right), and the motion of negative ions toward the ground electrode where they are collected.  The neutral molecules pass through the ground electrode and generate the thrust called the ionic wind.

This post summarizes work that has been done to develop ionic wind propulsion systems for aircraft.  The particular projects summarized are the following:

  • Major Alexander de Seversky’s Ionocraft vertical lifter (1964)
  • Michael Walden / LTAS lighter-than-air XEM-1 (1977)
  • Michael Walden / LTAS lighter-than-air EK-1 (2003)
  • The Festo b-IONIC Airfish airship (2005)
  • NASA ionic wind study (2009)
  • The MIT electroaerodynamic (EAD) heaver-than-air, fixed wing aircraft (2018)

In addition, we’ll take a look at recent ionic propulsion work being done by Electrofluidsystems Ltd., Electron Air LLC and the University of Florida’s Applied Physics Research Group.

2.  Scale model of ion-propelled Ionocraft vertical takeoff lifter flew in 1964

Major Alexander de Seversky developed the design concept for a novel aircraft concept called the “Ionocraft,” which was capable of hovering or moving in any direction at high altitudes by means of ionic discharge. His design for the Ionocraft is described in US Patent 3,130,945, “Ionocraft,” dated 28 April 1964.  You can read this patent here: https://patents.google.com/patent/US3130945A/en

The operating principle of de Seversky’s Ionocraft propulsion system is depicted in the following graphic.

Ion propulsion scheme implemented in the de Seversky Ionocraft. 
Source: Popular Mechanics, August 1964

In 1964, de Seversky built a two-ounce (57 gram) Ionocraft scale model and demonstrated its ability to fly while powered from an external 90 watt power conversion system (30,000 volts at 3 mA), significantly higher that conventional aircraft and helicopters.  This translated into a power-to-weight ratio of about 0.96 hp/pound.  You can watch a short 1964 video of a scale model Ionocraft test flight here: 

Screenshot showing Ionocraft scale model in flight
Screenshot showing ionic wind downdraft under an Ionocraft scale model in flight

De Seversky’s Ionocraft and its test program are described in an article in the August 1964 Popular Mechanics magazine, which is available at the following link:  https://books.google.com/books?id=ROMDAAAAMBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Alexander de Seversky’s one-man Ionocraft concept.
Source: Popular Mechanics Archive, August 1964
Alexander de Seversky’s Ionocraft commuter concept.
Source: Popular Mechanics Archive, August 1964
1969 Soviet concepts for passenger carrying Ionocraft.
Technology for Youth magazine, 1969, Issue 7.

In the 1960s, engineers found that Ionocraft technology did not scale up well and they were unable to build a vehicle that could generate enough lift to carry the equipment needed to produce the electricity needed to drive it.

3.  The first free-flying, ion-propelled, lighter-than-air craft flew in 1977:  Michael Walden / LTAS XEM-1

The subscale XEM-1 proof-of-concept demonstrator was designed by Michael Walden and built in 1974 by his firm, Lighter Than Air Solar (LTAS) in Nevada.  After leaving LTAS in 2005, Michael Walden founded Walden Aerospace where he is the President and CTO, building on the creative legacy of his work with the former LTAS firms.  The Walden Aerospace website is here: http://walden-aerospace.com/HOME.html 

The basic configuration of this small airship is shown in the following photo.  The MK-1 ionic airflow (IAF) hybrid EK drives are mounted on the sides of the airship’s rigid hull.

Source: Walden Aerospace.
Basic configuration of the MK-1 ionic airflow (IAF)
hybrid EK drive. Source: Walden Aerospace.

XEM-1 originally was tethered by cable to an external control unit and later was modified for wireless remote control operation. In this latter configuration, XEM-1 demonstrated the use of a hybrid EK propulsion system in a self-powered, free-flying vehicle.  

Walden described the MK-1 IAF EK drive as follows:  “The duct included a 10 inch ‘bent tip’ 3-bladed prop running on an electric motor to create higher pressures through the duct, making it a ‘modified pressure lifter’…. The duct also had a circular wire emitter, a dielectric separator and a toroidal collector making it a ‘toroid lifter’.”

The later MK-2 and MK-3 IAF EK drives had a similar duct configuration.  In all of these EK drives, the flow of ions from emitter to collector imparts momentum to neutral air molecules, creating usable thrust for propulsion.  You’ll find more information on the MK-1 IAF EK drive and later versions on the Walden Aerospace website here:  http://walden-aerospace.com/Waldens_Patents_files/Walden%20Aerospace%20Advanced%20Technologies%2011092013-2.pdf

The XEM-1 was demonstrated to the Department of Defense (DoD) and Department of Energy (DOE) in 1977 at Nellis Air Force Base in Nevada.  Walden reported:  “We flew the first fully solar powered rigid airship in 1974, followed by a US Department of Defense and Department of Energy flight demonstration in August 1977”…. “ DoD was interested in this work to the extent that some of it is still classified despite requests for the information to become freely available.”

Walden credits the XEM-1 with being the first fully self-contained air vehicle to fly with a hybrid ionic airflow electro-kinetic propulsion system. This small airship also demonstrated the feasibility of a rigid, composite, monocoque aeroshell, which became a common feature on many later Walden / LTAS airships.

4.  The second free-flying, ion-propelled, lighter-than-air craft flew in 2003:  Michael Walden / LTAS EK-1

Michael Walden designed the next-generation EK-1, which was a remotely controlled, self-powered, subscale model of a lenticular airship with a skin-integrated EK drive that was part of the outer surface of the hull.  The drive was electronically steered to provide propulsion in any direction with no external aerodynamic surfaces and no moving parts.

EK-1 aloft in the hanger.  Source: LTAS / Walden Aerospace
EK-1 with a skin-integrated propulsion system moving during hanger test flight in 2003.Source: LTAS / Walden Aerospace
 

In June 2003, LTAS rented a hangar at the Boulder City, NV airport to build and fly the EK-1.  Testing the EK-1 was concluded in early August 2003 after demonstrating the technology to National Institute for Discovery Science (NIDS) board members.

Based on the EK-1 design, a full-scale EK airship would have a rigid, aeroshell comprised largely of LTAS MK-4 lithographic integrated thruster / structure hull panels.  As with other contemporary Walden / LTAS airship designs, the MK-4 panel airship likely would have implemented density controlled buoyancy (DCB) active aerostatic lift control and would have had a thin film solar array on the top of the aeroshell.

Artist’s concept of a MK-4 panel airship.
Source: Walden Aerospace

5.  The third free-flying, ion-propelled, lighter-than-air craft flew in 2005: the Festo b-IONIC Airfish

The Festo b-IONIC Airfish airship was developed at the Technical University of Berlinwith guidance of the firm Festo AG & Co. KG.  This small, non-rigid airship is notable because, in 2005, it became the first aircraft to fly with a solid state propulsion system.  The neutrally-buoyant Airfish only flew indoors, in a controlled environment, at a very slow speed, but it flew.

Airfish. Source:  Festo AG & Co. KG

Some of the technical characteristics of the Airfish are listed below:

  • Length:  7.5 meters (24.6 ft)
  • Span: 3.0 meters (9.8 ft)
  • Shell diameter: 1.83 meters (6 ft)
  • Helium volume:  9.0 m3(318 ft3)
  • Total weight:  9.04 kg (19.9 lb)
  • Power source in tail: 12 x 1,500 mAh lithium-ion polymer cells (18 Ah total)
  • Power source per wing (two wings): 9 x 3,200 mAh lithium-ion polymer cells (28.8 Ah total)
  • High voltage: 20,000 to 30,000 volts
  • Buoyancy:  9.0 – 9.3 kg (19.8 – 20.5 lb)
  • Total thrust:  8 – 10 grams (0.018 – 0.022 pounds) 
  • Maximum velocity: 0.7 meters/sec (2.5 kph; 1.6 mph)

The b-IONIC Airfish employed two solid state propulsion systems, an electrostatic ionic jet and a plasma ray, which Festo describes as follows:

  • Electrostatic ionic jet:  “At the tail end Airfish uses the classic principle of an electrostatic ionic jet propulsion engine. High-voltage DC-fields (20-30 kV) along thin copper wires tear electrons away from air molecules. The positive ions thus created are then accelerated towards the negatively charged counter electrodes (ring-shaped aluminum foils) at high speeds (300-400 m/s), pulling along additional neutral air molecules. This creates an effective ion stream with speeds of up to 10 m/s.”
  • Plasma-ray:  “The side wings of Airfish are equipped with a new bionic plasma-ray propulsion system, which mimics the wing based stroke principle used by birds, such as penguins, without actually applying movable mechanical parts. As is the case with the natural role model, the plasma-ray system accelerates air in a wavelike pattern while it is moving across the wings.”
Airfish.  Source: Festo AG & Co. KG
Airfish.  Source: Festo AG & Co

The Festo b-IONIC Airfish demonstrated that a solid state propulsion system was possible.  The tests also demonstrated that the solid state propulsion systems also reduced drag, raising the intriguing possibility that it may be possible to significantly reduce drag if an entire vessel could be enclosed in a ionized plasma bubble.You’ll find more information on the Festo b-IONIC Airfish, its solid state propulsion system and implications for drag reduction in the the Festo brochure here: https://www.festo.com/net/SupportPortal/Files/344798/b_IONIC_Airfish_en.pdf

You can watch a 2005 short video on the Festo b-IONIC Airfish flight here:

6.  NASA ionic wind study – 2009

A corona discharge device generates an ionic wind, and thrust, when a high voltage corona discharge is struck between sharply pointed electrodes and larger radius ground electrodes.

In 2009, National Aeronautics & Space Administration (NASA) researchers Jack Wilson, Hugh Perkins and William Thompson conducted a study to examine whether the thrust of corona discharge systems could be scaled to values of interest for aircraft propulsion.  Their results are reported in report NASA/TM-2009-215822, which you’ll find at the following link: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100000021.pdf

Key points of the study included:

  • Different types of high voltage electrodes were tried, including wires, knife-edges, and arrays of pins. A pin array was found to be optimum. 
  • Parametric experiments, and theory, showed that the thrust per unit power could be raised from early values of 5 N/kW to values approaching 50 N/kW, but only by lowering the thrust produced, and raising the voltage applied. 
  • In addition to using DC voltage, pulsed excitation, with and without a DC bias, was examined. The results were inconclusive as to whether this was advantageous. 
  • It was concluded that the use of a corona discharge for aircraft propulsion did not seem very practical.”

7.  The first heavier-than-air, fixed-wing, ion-propelled aircraft flew in 2018

On 21 November 2018, MIT researchers reported successfully flying the world’s first heavier-than-air, fixed-wing, ion-propelled (electroaerodynamic, EAD) aircraft.  You can read the paper by Haofeng Xu, et al., “Flight of an aeroplane with solid-state propulsion,” on the Nature website here: https://www.nature.com/articles/s41586-018-0707-9

The design of the MIT EAD aircraft is shown below:

a, Computer-generated rendering of the EAD airplane. 
b, Photograph of actual EAD airplane (after multiple flight trials).

Some of the technical characteristics of this MIT aircraft are listed below:

  • Wingspan: 4.9 meters (16 ft)
  • Total weight: 2.45 kg (5.4 lb)
  • Power source: powered by 54 x 3.7 volt 150 mAh lithium-ion polymer cells (8.1 Ah total)
  • High voltage: 40,000 volts (+ 20,000 volts / – 20,000 volts)
  • Total thrust: 3.2 N, 326 grams (0.718 pounds) 
  • Maximum velocity: 4.8 meters/sec (17.3 kph; 10.7 mph)

In their paper, the MIT researchers reported:

  • “We performed ten flights with the full-scale experimental aircraft at the MIT Johnson Indoor Track…. Owing to the limited length of the indoor space (60 m), we used a bungeed launch system to accelerate the aircraft from stationary to a steady flight velocity of 5 meters/sec within 5 meters, and performed free flight in the remaining 55 meters of flight space. We also performed ten unpowered glides with the thrusters turned off, in which the airplane flew for less than 10 meters. We used cameras and a computer vision algorithm to track the aircraft position and determine the flight trajectory.”
  • “All flights gained height over the 8–9 second segment of steady flight, which covered a distance of 40–45 meters…. The average physical height gain of all flights was 0.47 meters…. However, for some of the flights, the aircraft velocity decreased during the flight. An adjustment for this loss of kinetic energy…. results in an energy equivalent height gain, which is the height gain that would have been achieved had the velocity remained constant. This was positive for seven of the ten flights, showing that better than steady-level flight had been achieved in those cases.”
  • “In this proof of concept for this method of propulsion, the realized thrust-to-power ratio was 5 N/kW1, which is of the order of conventional airplane propulsion methods such as the jet engine.”  Overall efficiency was estimated to be 2.56%.

The propulsion principles of the MIT EAD aircraft are explained in relation to the following diagram in the November 2018 article by Franck Plouraboué, “Flying With Ionic Wind,” which you can read on the Nature website at the following link:  https://www.nature.com/articles/d41586-018-07411-z

The following diagram and explanatory text are reproduced from that article.

  • In Figure a, above: …an electric field (not shown) is applied to the region surrounding a fine wire called the emitter (shown in cross-section). The field induces electron cascades, whereby free electrons collide with air molecules (not shown in the cascades) and consequently free up more electrons. This process produces charged air molecules in the vicinity of the emitter — a corona discharge. Depending on the electric field, negatively or positively charged molecules drift away (red arrows) from the emitter. These molecules collide with neutral air molecules, generating an ionic wind (black arrows). 
  • In Figure b, above: The aircraft uses a series of emitters and devices called collectors, the longitudinal directions of which are perpendicular to the ionic wind. The flow of charged air molecules occurs mainly along the directions (red arrows) joining emitters and collectors. Consequently, the ionic wind is accelerated (black arrows) predominantly in these regions. 

You can view a short video of the MIT EAD aircraft test flights here:  

8.  The future of ionic propulsion for aerospace applications.

If it can be successfully developed to much larger scales, ionic propulsion offers the potential for aircraft to fly in the atmosphere on a variety of practical missions using only ionized air for propulsion.  Using other ionized fluid media, ionic propulsion could develop into a means to fly directly from the surface of the earth into the vacuum of space and then operate in that environment. The following organizations have been developing such systems.

Electrofluidsystems Ltd.

In 2006, the Technical University of Berlin’s Airfish project manager, Berkant Göksel, founded the firm Electrofluidsystems Ltd., which in 2012 was rebranded as IB Göksel Electrofluidsystems.  This firm presently is developing a new third generation of plasma-driven airships with highly reduced ozone and nitrogen oxide (NOx) emissions, magneto-plasma actuators for plasma flow control, and the company’s own blended wing type flying wing products.  You’ll find their website here:  https://www.electrofluidsystems.com

Source: Electrofluidsystems TU Berlin
Advanced plasma-driven aircraft concept. Source:  Electrofluidsystems TU Berlin

MIT researchers are developing designs for high-performance aircraft using ionic propulsion.  Theoretically, efficiency improves with speed, with an efficiency of 50% possible at a speed of about 1,000 kph (621 mph).  You can watch a short video on MIT work to develop a Star Trek-like ion drive aircraft here:  

Electron Air LLC

Another firm active in the field of ionic propulsion is Electron Air LLC (https://electronairllc.org), which, on 6 November 2018, was granted patent US10119527B2 for their design for a self-contained ion powered craft.  Their grid shaped craft is described as follows:

“The aircraft assembly includes a collector assembly, an emitter assembly, and a control circuit operatively connected to at least the emitter and collector assemblies and comprising a power supply configured to provide voltage to the emitter and collector assemblies. The assembly is configured, such that, when the voltage is provided from an on board power supply, the aircraft provides sufficient thrust to lift each of the collector assembly, the emitter assembly, and the entire power supply against gravity.”

The device, as shown in patent Figure 3, consists of a two-layer grid structure with a collector assembly (50), an emitter assembly (70) and peripheral supports (33 to 37).

You can read patent US10119527B2 here: https://patents.google.com/patent/US10119527B2/en?oq=10119527

This patent cites Alexander de Seversky’s Patent 3130945, “Ionocraft.”

You can watch a short (1:22 minute) video of an outdoor tethered test flight of a remotely controlled, self-contained, ion powered, heavier-than-air craft with onboard power at the following link: https://www.youtube.com/watch?v=aX21HCHlgKo

University of Florida, Applied Physics Research Group

In the early 2000s, a Wingless Electromagnetic Air Vehicle (WEAV) was invented by Dr. Subrata Roy, a plasma physicist and aerospace engineering professor at the University of Florida. WEAV is described as a heavier-than-air flight system that can self-lift, hover, and fly using plasma propulsion with no moving components. The laboratory-scale device is six inch (15.2 cm) in diameter.  The basic configuration of the disc-shaped craft is shown in patent 8960595B2 Figure 1.

This research project has been supported by the US Air Force Office of Scientific Research. You’ll find details on WEAV technology in the University of Florida’s 2011 final report at the following (very slow loading) link: https://apps.dtic.mil/dtic/tr/fulltext/u2/a564120.pdf

In this report, the authors describe the technology: “This revolutionary concept is based on the use of an electro-(or magneto) hydrodynamic (EHD/MHD) thrust generation surface that is coated with multiple layers of dielectric polymers with exposed and/or embedded electrodes for propulsion and dynamic control. This technology has the unique capability of imparting an accurate amount of thrust into the surrounding fluid enabling the vehicle to move and react. Thrust is instantaneously and accurately controlled by the applied power, its waveform, duty cycle, phase lag and other electrical parameters. Once the applied power is removed the thrust vanishes.”

The following patents related to WEAV technology have been filed and assigned to the University of Florida Research Foundation Inc.:

These patents do not cite Alexander de Seversky’s Patent 3130945, “Ionocraft.”

9.  More reading on electrodynamic propulsion for aircraft

General

MIT electroaerodynamic aircraft

Ionocraft lifters

WEAV