Category Archives: Aeronautical

Bio-fuel at Less Than Half the Price

Peter Lobner

1.  New process for manufacturing bio-fuel

The Joint BioEnergy Institute (JBEI) is a Department of Energy (DOE) bioenergy research center dedicated to developing advanced bio-fuels, which are liquid fuels derived from the solar energy stored in plant biomass. Such fuels currently are replacing gasoline, diesel and jet fuels in selected applications.

On 1 July 2016, a team of Lawrence Berkeley National Laboratory (LBNL) and Sandia National Laboratories (SNL) scientists working at JBEI published a paper entitled, “CO2 enabled process integration for the production of cellulosic ethanol using bionic liquids.” The new process reported in this paper greatly simplifies the industrial manufacturing of bio-fuel and significantly reduces waste stream volume and toxicity as well as manufacturing cost.

The abstract provides further information:

“There is a clear and unmet need for a robust and affordable biomass conversion technology that can process a wide range of biomass feedstocks and produce high yields of fermentable sugars and bio-fuels with minimal intervention between unit operations. The lower microbial toxicity of recently developed renewable ionic liquids (ILs), or bionic liquids (BILs), helps overcome the challenges associated with the integration of pretreatment with enzymatic saccharification and microbial fermentation. However, the most effective BILs known to date for biomass pretreatment form extremely basic pH solutions in the presence of water, and therefore require neutralization before the pH range is acceptable for the enzymes and microbes used to complete the biomass conversion process. Neutralization using acids creates unwanted secondary effects that are problematic for efficient and cost-effective biorefinery operations using either continuous or batch modes.

We demonstrate a novel approach that addresses these challenges through the use of gaseous carbon dioxide to reversibly control the pH mismatch. This approach enables the realization of an integrated biomass conversion process (i.e., “single pot”) that eliminates the need for intermediate washing and/or separation steps. A preliminary technoeconomic analysis indicates that this integrated approach could reduce production costs by 50–65% compared to previous IL biomass conversion methods studied.”

 Regarding the above abstract, here are a couple of useful definitions:

  • Ionic liquids: powerful solvents composed entirely of paired ions that can be used to dissolve cellulosic biomass into sugars for fermentation.
  • Enzymatic saccharification: breaking complex carbohydrates such as starch or cellulose into their monosaccharide (carbohydrate) components, which are the simplest carbohydrates, also known as single sugars.

The paper was published on-line in the journal, Energy and Environmental Sciences, which you can access via the following link:

http://pubs.rsc.org/en/content/articlelanding/2016/ee/c6ee00913a#!divAbstract

Let’s hope they’re right about the significant cost reduction for bio-fuel production.

2.  Operational use of bio-fuel

One factor limiting the wide-scale use of bio-fuel is its higher price relative to the conventional fossil fuels it is intended to replace. The prospect for significantly lower bio-fuel prices comes at a time when operational use of bio-fuel is expanding, particularly in commercial airlines and in the U.S. Department of Defense (DoD). These bio-fuel users want advanced bio-fuels that are “drop-in” replacements to traditional gasoline, diesel, or jet fuel. This means that the advanced bio-fuels need to be compatible with the existing fuel distribution and storage infrastructure and run satisfactorily in the intended facilities and vehicles without introducing significant operational or maintenance / repair / overhaul (MRO) constraints.

You will find a fact sheet on the DoD bio-fuel program at the following link:

http://www.americansecurityproject.org/dods-biofuels-program/

The “drop in” concept can be difficult to achieve because a bio-fuel may have different energy content and properties than the petroleum fuel it is intended to replace. You can find a Department of Energy (DOE) fuel properties comparison chart at the following link:

http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf

Another increasingly important factor affecting the deployment of bio-fuels is that the “water footprint” involved in growing the biomass needed for bio-fuel production and then producing the bio-fuel is considerably greater than the water footprint for conventional hydrocarbon fuel extraction and production.

 A.  Commercial airline use of bio-fuel:

Commercial airlines became increasingly interested in alternative fuels after worldwide oil prices peaked near $140 in 2008 and remained high until 2014.

A 2009 Rand Corporation technical report, “Near-term Feasibility of Alternative Jet Fuels,” provides a good overview of issues and timescales associated with employment of bio-fuels in the commercial aviation industry. Important findings included:

  • Drop-in” fuels have considerable advantages over other alternatives as practical replacements for petroleum-based aviation fuel.
  • Alcohols do not offer direct benefits to aviation, primarily because high vapor pressure poses problems for high-altitude flight and safe fuel handling. In addition, the reduced energy density of alcohols relative to petroleum-based aviation fuel would substantially reduced aircraft operating capabilities and would be less energy efficient.
  • Biodiesel and biokerosene, collectively known as FAMEs, are not appropriate for use in aviation, primarily because they leave deposits at the high temperatures found in aircraft engines, freeze at higher temperatures than petroleum-based fuel, and break down during storage

You can download this Rand report at the following link

http://www.rand.org/content/dam/rand/pubs/technical_reports/2009/RAND_TR554.pdf

After almost two years of collaboration with member airlines and strategic partners, the International Air Transport Association (IATA) published the report, “IATA Guidance Material for Biojet Fuel Management,” in November 2012. A key finding in this document is the following:

“To be acceptable to Civil Aviation Authorities, aviation turbine fuel must meet strict chemical and physical criteria. There exist several specifications that authorities refer to when describing acceptable conventional jet fuel such as ASTM D1655 and Def Stan 91-91. At the time of issue, blends of up to 50% biojet fuel produced through either the Fischer-Tropsch (FT) process or the hydroprocessing of oils and fats (HEFA – hydroprocessed esters and fatty acids) are acceptable for use under these specifications, but must first be certified under ASTM D7566. Once the blend has demonstrated compliance with the relevant product specifications, it may be regarded as equivalent to conventional jet fuel in most applications.“

You can download this IATA document at the following link:

https://www.iata.org/publications/Documents/guidance-biojet-management.pdf

In 2011, KLM flew the world’s first commercial bio-fuel flight, carrying passengers from Amsterdam to Paris. Also in 2011, Aeromexico flew the world’s first bio-fuel trans-Atlantic revenue passenger flight, from Mexico City to Madrid.

In March 2015, United Airlines (UA) inaugurated use of bio-fuel on flights between Los Angeles (LAX) and San Francisco (SFO). Eventually, UA plans to expand the use of bio-fuel to all flights operating from LAX. UA is the first U.S. airline to use renewable fuel for regular commercial operation.

Many other airlines worldwide are in various stages of bio-fuel testing and operational use.

B.  U.S. Navy use of bio-fuel:

The Navy is deploying bio-fuel in shore facilities, aircraft, and surface ships. Navy Secretary Ray Mabus has established a goal to replace half of the Navy’s conventional fuel supply with renewables by 2020.

In 2012, the Navy experimented with a 50:50 blend of traditional petroleum-based fuel and biofuel made from waste cooking oil and algae oil.   This blend was used successfully on about 40 U.S. surface ships that participated in the Rim of the Pacific (RIMPAC) exercise with ships of other nations. The cost of pure bio-fuel fuel for this demonstration was about $26.00 per gallon, compared to about $3.50 per gallon for conventional fuel at that time.

In 2016, the Navy established the “Great Green Fleet” (GGF) as a year-long initiative to demonstrate the Navy’s ability to transform its energy use.

Great Green Fleet logo          Source: U.S. Navy

The Navy described this initiative as follows:

“The centerpiece of the Great Green Fleet is a Carrier Strike Group (CSG) that deploys on alternative fuels, including nuclear power for the carrier and a blend of advanced bio-fuel made from beef fat and traditional petroleum for its escort ships. These bio-fuels have been procured by DON (Department of Navy) at prices that are on par with conventional fuels, as required by law, and are certified as “drop-in” replacements that require no engine modifications or changes to operational procedures.”

Deployment of the Great Green Fleet started in January 2016 with the deployment of Strike Group 3 and its flagship, the nuclear-powered aircraft carrier USS John C. Stennis. The conventionally-powered ships in the Strike Group are using a blend of 10% bio-fuel and 90% petroleum. The Navy originally aimed for a 50:50 ratio, but the cost was too high. The Navy purchased about 78 million gallons of blended bio-fuel for the Great Green Fleet at a price of $2.05 per gallon.

C.  U.S. Air Force use of bio-fuel:

The USAF has a goal of meeting half its domestic fuel needs with alternative sources by 2016, including aviation fuel.

The Air Force has been testing different blends of jet fuel and biofuels known generically as Hydrotreated Renewable Jet (HRJ). This class of fuel uses triglycerides and free fatty acids from plant oils and animal fats as the feedstock that is processed to create a hydrocarbon aviation fuel.

To meet its energy plan, the USAF plans to use a blend that combines military-grade fuel known as JP-8 with up to 50 percent HRJ. The Air Force also has certified a 50:50 blend of Fisher-Tropsch synthetic kerosene and conventional JP-8 jet fuel across its fleet.

The Air Force Civil Engineer Support Agency (AFCESA), headquartered at Tyndall Air Force Base, Florida is responsible for certifying the USAF aviation fuel infrastructure to ensure its readiness to deploy blended JP-8/bio-fuel.

Solar Impulse 2 Completes the First Around-the-World Flight on Solar Power

Peter Lobner

Solar Impulse 2 completed its around-the-world mission when pilot Bertrand Piccard landed on 26 July 2016 at 00:05 PM UTC (Coordinated Universal Time) in Abu Dhabi, UAE after completing leg 17, which was a 48 hour 7 minute, 2694 km (1674 mile) flight from Cairo, Egypt. This historic mission began on 9 March 2015 from Abu Dhabi and covered more than 42,000 km (26,097 miles) before Solar Impulse 2 returned to its starting point.

Si2 landing at Abu Dhabi 1Source: Solar ImpulseSi2 landing at Abu Dhabi 2Source: Solar ImpulseSi2 landing at Abu Dhabi 3Source: Solar ImpulseSi2 landing at Abu Dhabi 4André Borschberg (l) and pilot Bertrand Piccard (r). Source: Solar Impulse

The Solar Impulse 2 team posted the following message on their website:

 “Taking turns at the controls of Solar Impulse 2 (Si2) – their zero-emission electric and solar airplane, capable of flying day and night without fuel – Bertrand Piccard and André Borschberg succeeded in their crazy dream of achieving the first ever Round-The-World Solar Flight. By landing back in Abu Dhabi after a total of 21 days of flight travelled in a 17-leg journey, Si2 has proven that clean technologies can achieve the impossible.”

Congratulations to pilots Bertrand Piccard and André Borschberg and the entire Solar Impulse 2 team for accomplishing this incredible milestone in aviation history.

Si2 landing at Abu Dhabi 5Source: Solar Impulse

For more information on the historic around-the world mission of Solar Impulse 2, visit the team’s website at the following link:

http://www.solarimpulse.com

Also see my following posts:

  • 23 May 2016:   Solar Impulse 2 is Making its way Across the USA
  • 27 February 2016: Solar Impulse 2 Preparing for the Next Leg of its Around-the-World Journey
  • 3 July 2015: Solar Impulse 2 Completes Record Solo, Non-Stop, Solar-Powered Flight from Nagoya, Japan to Oahu, Hawaii
  • 10 March 2015: Solar Impulse 2 Designed for Around-the-World Flight on Solar Power

Solar Impulse 2 is Making its way Across the USA

Peter Lobner

If you have been reading the Pete’s Lynx blog for a while, then you should be familiar with the remarkable team that created the Solar Impulse 2 aircraft and is attempting to make the first flight around the world on solar power.  The planned route is shown in the following map.

Solar Impulse 2 route map

Image source: Solar Impulse

I refer you to my following posts for background information:

  • 10 March 2015: Solar Impulse 2 Designed for Around-the-World Flight on Solar Power
  • 3 July 2015: Solar Impulse 2 Completes Record Solo, Non-Stop, Solar-Powered Flight from Nagoya, Japan to Oahu, Hawaii
  • 27 February 2016: Solar Impulse 2 Preparing for the Next Leg of its Around-the-World Journey

Picking off where these stories left off in Hawaii, Solar Impulse 2 has made four more flights:

  • 21 – 24 April 2016: Hawaii to Moffett Field, near San Francisco, CA; 2,539 miles (4,086 km) in 62 h 29 m
  • 2 – 3 May 2016: San Francisco to Phoenix, AZ; 692 miles (1,113 km) in 15 h 52 m
  • 12 – 13 May 2016: Phoenix to Tulsa, OK; 976 miles (1,570 km) in 18 h 10 m
  • 21 – 22 May 2016: Tulsa to Dayton, OH; 692 miles (1,113 km) in 16 h 34 m

From the above distances and flight times, the average speed of Solar Impulse 2 across the USA was a stately 43.6 mph (70.2 kph).  Except for the arrival in the Bay Area, I think the USA segments of the Solar Impulse 2 mission have been given remarkably little coverage by the mainstream media.

SI2 flying above the USAImage source: Solar Impulse

Regarding the selection of Dayton as a destination for Solar Impulse 2, the team posted the following:

“On his way to Dayton, Ohio, hometown of Wilbur and Orville Wright, André Borschberg pays tribute to pioneering spirit, 113 years after the two brothers succeeded in flying the first power-driven aircraft heavier than air.

To develop their wing warping concept, the two inventors used their intuition and observation of nature to think out of the box. They defied current knowledge at a time where all experts said it would be impossible. When in 1903, their achievement marked the beginning of modern aviation; they did not suspect that a century later, two pioneers would follow in their footsteps, rejecting all dogmas to fly an airplane around the world without a drop of fuel.

This flight reunites explorers who defied the impossible to give the world hope, audacious men who believed in their dream enough to make it a reality.”

Wright Bros and SI2 pilotsImage source: Solar Impulse.

You can see in the above route map that future destinations are not precisely defined. Flight schedules and specific routes are selected with due consideration for en-route weather.

The Solar Impulse 2 team announced that its next flight is scheduled to take off from Dayton on 24 May and make an 18-hour flight to the Lehigh Valley Airport in Pennsylvania. Following that, the next flight is expected to be to an airport near New York City.

If you haven’t been following the flight of Solar Impulse 2 across the USA, I hope you will start now. This is a remarkable aeronautical mission and it is happening right now. You can check out the Solar Impulse website at:

http://www.solarimpulse.com

If you wish, you can navigate to and sign up for e-mail updates on future flights. Here’s the direct link:

http://www.solarimpulse.com/subscribe

With these updates, you also will be able to access live video feeds during the flights. OK, the videos are mostly pretty boring, but they are remarkable nonetheless because of the mission you have an opportunity to watch, even briefly, in real time.

There’s much more slow, steady flying to come before Solar Impulse 2 completes its around-the-world journey back to Abu Dhabi. I send my best wishes for a successful mission to the brave pilots, André Borschberg and Bertrand Piccard, and to the entire Solar Impulse 2 team.

Landing a Reusable Booster Rocket on a Dime

Updated 18 March 2020

Peter Lobner

There are two U.S. firms that have succeeded in launching and recovering a booster rocket that was designed to be reusable. These firms are Jeff Bezos’ Blue Origin and Elon Musk’s SpaceX.   Their booster rockets are designed for very different missions.

  • Blue Origin’s New Shepard booster and capsule are intended for brief, suborbital flights for space tourism and scientific research. The booster and capsule will be “man-rated” for passenger-carrying suborbital missions.
  • In contrast, SpaceX’s Falcon 9 booster rocket is designed to deliver a variety of payloads to Earth orbit. The payload may be the SpaceX Dragon capsule or a different civilian or military spacecraft. Currently, the Falcon 9 booster and Dragon capsule are not “man-rated” for orbital missions. SpaceX is developing a crewed version of the Dragon capsule that, in the future, will be used to deliver and return crewmembers for the International Space Station (ISS).

Both firms cite a cost advantage of recovering and reusing an expensive booster rocket and space capsule. Let’s see how they’re doing.

Blue Origin

The basic flight profiles of a single-stage, single engine New Shepard booster and capsule are shown in the following diagram. The primary goals of each flight are to boost the capsule and passengers above 62.1 miles (100 km), safely recover the capsule and passengers, and safely recover the booster rocket. You can see in the diagram that the booster rocket and the capsule separate after the booster’s rocket engine is shutdown and they are recovered separately. At separation, the booster and capsule are traveling at about Mach 3 (about 1,980 mph, 3,186 kph). The orientation of the booster rocket is controlled during descent and the rocket engine is restarted once at low altitude to bring the booster to a soft, vertical landing. Both the booster rocket and the capsule are designed for reuse.

Blue-origin-flight-profileSource: Blue Origin

On 23 November 2015, Blue Origin made history when, on its first attempt, the New Shepard booster completed a suborbital flight that culminated with the autonomous landing of the booster rocket near the launch site in west Texas. The capsule landed nearby under parachutes. You can view a video of this historic flight at the following link:

https://www.youtube.com/watch?v=9pillaOxGCo

This same New Shepard booster was launched again on 22 January 2016, completed the planned suborbital flight, and again made an autonomous safe landing. This flight marked the first reuse of a booster rocket.

Again using the same hardware, New Shepard was launched on its third flight and safely recovered on 2 April 2016. On this flight, the rocket engine was re-started at a lower altitude (3,635 feet, 1,107 m) than on the previous flights to demonstrate the fast startup of the engine. The booster rocket made an on-target landing, touching down at a velocity of 4.8 mph (7.7 kph).

New Shepard landing 3Source: Blue Origin

You can view a short video of the third New Shepard flight at the following link:

https://www.blueorigin.com/news/news/pushing-the-envelope#youtubeYU3J-jKb75g

In this video, the view from the capsule at 64.6 miles (104 km) above the Earth is stunning. As the landing of the booster rocket approaches, it is dropping like a stone until the rocket engine powers up, quickly stops the descent, and brings the booster rocket in for an accurate, soft, vertical landing.

So, the current score for Blue Origin is 3 attempts and 3 successful soft, vertical landings in less than 5 months. The same New Shepard booster was used all three times (i.e., it has been reused twice).

Refer to the Blue Origin website at the following link for more information.

https://www.blueorigin.com

SpaceX Falcon 9 (F9R)

The basic flight profile for a two-stage Falcon 9 recoverable booster on an orbital mission is shown in the following diagram. For ISS re-supply missions, the target for the Dragon capsule is in a near-circular orbit at an altitude of about 250 miles (403 km) and an orbital velocity of about 17,136 mph (27,578 kph). The first stage shuts down and separates from the second stage at an altitude of about 62.1 miles (100 km) and a speed of about 4,600 mph (7,400 kph, Mach 7). These parameters are for illustrative purposes only and will vary as needed to meet the particular mission requirements. The second stage continues into orbit with a Dragon capsule or other payload.

The nine-engine first stage carries extra fuel to enable some of the booster rockets to re-start three times after stage separation to adjust trajectory, decelerate, and make a soft vertical landing on an autonomous recovery barge floating in the ocean 200 miles (320 km) or more downrange from the launch site.

The empty weight of the recoverable version of the Falcon 9 first stage (the F9R) is 56,438 pounds (25,600 kg,), which is about 5,511 pounds (2,500 kg) more than the basic, non-recoverable version (V1.1). The added fuel and structural weight to enable recovery of the first stage reduces the payload mass that can be delivered to orbit.

Falcon flight profile to barge landingSource: SpaceX

The autonomous “drone” barge is a very small target measuring about 170 ft. × 300 ft. (52 m × 91 m). It is equipped with azimuthal thrusters that provide precise positioning using GPS position data. The Falcon 9 booster knows where the drone barge should be. The Falcon 9’s four landing legs span 60 ft. (18 m), and all must land on the barge.

SpaceX_ASDSSource: SpaceX

SpaceX made a series of unsuccessful attempts to land on a drone barge before their first successful landing:

  • 10 January 2015: First attempt; hard landing; booster destroyed.
  • 11 February 2015: High seas prevented use of the barge. Instead, the Falcon 9 first stage was flown to a soft, vertical landing in the ocean, simulating a barge landing.
  • 14 April 2015: Second attempt; successful vertical landing but the booster toppled, likely due to remaining lateral momentum.
  • 7 January 2016: Third attempt; successful vertical landing but the booster toppled, likely due to a mechanical failure in one landing leg.
  • 4 March 2016: Fourth attempt, with low fuel reserve and using only three engines; hard landing; booster destroyed.

On 8 April 2016, a Falcon 9 booster was launched from Cape Canaveral on an ISS re-supply mission. The first stage of this booster rocket became the first to make a successful landing on the drone barge downrange in the Atlantic.

A002_C002_0408A9Source: SpaceX

You can view a short video of the Falcon 9 booster landing on the drone barge at the following link:

https://www.youtube.com/watch?v=RPGUQySBikQ

In the video, you will note the barge heaving in the moderate seas. After landing, the 156 foot (47.5 m) tall booster rocket is just balanced on its landing legs. Before the barge can be towed back to port, crew must board the barge and secure the booster. This is done by placing “shoes” over the landing feet and welding the shoes to the deck of the barge. Once back at Cape Canaveral, the booster will be examined and the rocket engine will be test fired to determine if the first stage can be reused.

Previously, on 21 December 2015, SpaceX successfully launched its Falcon 9 booster on an orbital mission and then landed the first stage back on the ground at Cape Canaveral. As shown in the diagram below, this involved a very different flight profile than for a Falcon 9 flight with a landing on the downrange drone barge. For the December 2015 flight, the Falcon 9 first stage had to reverse direction to fly back to Cape Canaveral from about 59 miles (95 km) downrange and then decelerate and maneuver for a soft, vertical landing about 10 minutes after launch.

Blue Origin-Falcon flight profile comparedSource: SpaceX

After recovering the booster, the Falcon 9 was inspected and the engines were successfully re-tested on 15 January 2016, on a launch pad at Cape Canaveral. I could not determine if this Falcon 9 first stage has been reused.

So, the current score for SpaceX is 6 attempts (not counting the February 2015 soft landing in the ocean) and 2 successes (one on land and one on the drone barge) in 15 months.

Refer to the SpaceX website at the following link for more information.

http://www.spacex.com

The bottom line

In the above diagram for the December 2015 Falcon 9 flight, the relative complexity of a typical New Shepard flight profile and the Falcon 9 flight profile with return to Cape Canaveral is clear. The Falcon 9 flight profile for a landing on the small, moving, down-range drone barge is even more complex.

The New Shepard sub-orbital mission is much less challenging than any Falcon 9 orbital mission. Nonetheless, both booster rockets face very similar challenges as they approach the landing site to execute an autonomous, soft, vertical landing.

Both Blue Origin and SpaceX have made tremendous technological leaps in demonstrating that a booster rocket can make an autonomous, soft, vertical landing and remain in a condition that allows its reuse in a subsequent mission. Blue Origin actually has reused their booster rocket and capsule twice, further demonstrating the maturity of reusable rocket technology.

It remains to be seen if this technology actually delivers the operating cost savings anticipated by Blue Origin and SpaceX. I hope it does. When space tourism becomes a reality, the hoped-for cost benefits of reusable booster rockets and spacecraft could affect my ticket price.

18 March 2020 Update:  Four years later

On 6 March 2020, SpaceX launched its 20th commercial resupply services mission (CRS-20) to the International Space Station (ISS).  The successful launch concluded with the 50thsuccessful landing of the first stage of a Falcon 9 launch vehicle.  On this mission, the first stage flew back for a landing at Cape Canaveral in the windiest conditions encountered to date, 25 to 30 mph.  This was the last launch with the original cargo-only version of the Dragon capsule. Subsequent launches will use 2nd-generation Dragon capsules that are roomier and designed to also accommodate astronauts.

About two weeks later, on 18 March 2020, SpaceX launched another successful Falcon 9 mission, for the first time using a first stage that had flown on four prior missions.  The satellite payload was launched into the intended orbit.  However, a malfunction in one of nine first stage engines prevented recovery of the booster rocket.

On 11 December 2019, Blue Origin reported that New Shepard mission NS-12 was successfully completed.  “This was the 6th flight for this particular New Shepard vehicle. Blue Origin has so far reused two boosters five times each consecutively, so today marks a record with this booster completing its 6th flight to space and back.”

Booster reusability has become a reality for SpaceX and Blue Origin, and other firms are following their lead by developing new reusable launch vehicles.  These are encouraging steps toward more economic access to Earth orbit and beyond.  Both SpaceX and Blue Origin have advanced reusable launch vehicle technology significantly in the past four years.  Both soon will begin human space flight using their respective launch vehicles and space capsules.

Synthetic Aperture Radar (SAR) and Inverse SAR (ISAR) Enable an Amazing Range of Remote Sensing Applications

Peter Lobner

SAR Basics

Synthetic Aperture Radar (SAR) is an imaging radar that operates at microwave frequencies and can “see” through clouds, smoke and foliage to reveal detailed images of the surface below in all weather conditions. Below is a SAR image superimposed on an optical image with clouds, showing how a SAR image can reveal surface details that cannot be seen in the optical image.

Example SAR imageSource: Cassidian radar, Eurimage optical

SAR systems usually are carried on airborne or space-based platforms, including manned aircraft, drones, and military and civilian satellites. Doppler shifts from the motion of the radar relative to the ground are used to electronically synthesize a longer antenna, where the synthetic length (L) of the aperture is equal to: L = v x t, where “v” is the relative velocity of the platform and “t” is the time period of observation. Depending on the altitude of the platform, “L” can be quite long. The time-multiplexed return signals from the radar antenna are electronically recombined to produce the desired images in real-time or post-processed later.

SAR principle

Source: Christian Wolff, http://www.radartutorial.eu/20.airborne/pic/sar_principle.print.png

This principle of SAR operation was first identified in 1951 by Carl Wiley and patented in 1954 as “Simultaneous Buildup Doppler.”

SAR Applications

There are many SAR applications, so I’ll just highlight a few.

Boeing E-8 JSTARS: The Joint Surveillance Target Attack Radar System is an airborne battle management, command and control, intelligence, surveillance and reconnaissance platform, the prototypes of which were first deployed by the U.S. Air Force during the 1991 Gulf War (Operation Desert Storm). The E-8 platform is a modified Boeing 707 with a 27 foot (8 meter) long, canoe-shaped radome under the forward fuselage that houses a 24 foot (7.3 meters) long, side-looking, multi-mode, phased array antenna that includes a SAR mode of operation. The USAF reports that this radar has a field of view of up to 120-degrees, covering nearly 19,305 square miles (50,000 square kilometers).

E-8 JSTARSSource: USAF

Lockheed SR-71: This Mach 3 high-altitude reconnaissance jet carried the Advanced Synthetic Aperture Radar System (ASARS-1) in its nose. ASARS-1 had a claimed 1 inch resolution in spot mode at a range of 25 to 85 nautical miles either side of the flight path.  This SAR also could map 20 to 100 nautical mile swaths on either side of the aircraft with lesser resolution.

SR-71Source: http://www.wvi.com/~sr71webmaster/sr_sensors_pg2.htm

Northrop RQ-4 Global Hawk: This is a large, multi-purpose, unmanned aerial vehicle (UAV) that can simultaneously carry out electro-optical, infrared, and synthetic aperture radar surveillance as well as high and low band signal intelligence gathering.

Global HawkSource: USAF

Below is a representative RQ-4 2-D SAR image that has been highlighted to show passable and impassable roads after severe hurricane damage in Haiti. This is an example of how SAR data can be used to support emergency management.

Global Hawk Haiti post-hurricane image123-F-0000X-103Source: USAF

NASA Space Shuttle: The Shuttle Radar Topography Mission (SRTM) used the Space-borne Imaging Radar (SIR-C) and X-Band Synthetic Aperture Radar (X-SAR) to map 140 mile (225 kilometer) wide swaths, imaging most of Earth’s land surface between 60 degrees north and 56 degrees south latitude. Radar antennae were mounted in the Space Shuttle’s cargo bay, and at the end of a deployable 60 meter mast that formed a long-baseline interferometer. The interferometric SAR data was used to generate very accurate 3-D surface profile maps of the terrain.

Shuttle STRMSource: NASA / Jet Propulsion Laboratory

An example of SRTM image quality is shown in the following X-SAR false-color digital elevation map of Mt. Cotopaxi in Ecuador.

Shuttle STRM imageSource: NASA / Jet Propulsion Laboratory

You can find more information on SRTM at the following link:

https://directory.eoportal.org/web/eoportal/satellite-missions/s/srtm

ESA’s Sentinel satellites: Refer to my 4 May 2015 post, “What Satellite Data Tell Us About the Earthquake in Nepal,” for information on how the European Space Agency (ESA) assisted earthquake response by rapidly generating a post-earthquake 3-D ground displacement map of Nepal using SAR data from multiple orbits (i.e., pre- and post-earthquake) of the Sentinel-1A satellite.  You can find more information on the ESA Sentinel SAR platform at the following link:

http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Introducing_Sentinel-1

You will find more general information on space-based SAR remote sensing applications, including many high-resolution images, in a 2013 European Space Agency (ESA) presentation, “Synthetic Aperture Radar (SAR): Principles and Applications”, by Alberto Moreira, at the following link:

https://earth.esa.int/documents/10174/642943/6-LTC2013-SAR-Moreira.pdf

ISAR Basics

ISAR technology uses the relative movement of the target rather than the emitter to create the synthetic aperture. The ISAR antenna can be mounted in a airborne platform. Alternatively, ISAR also can be used by one or more ground-based antennae to generate a 2-D or 3-D radar image of an object moving within the field of view.

ISAR Applications

Maritime surveillance: Maritime surveillance aircraft commonly use ISAR systems to detect, image and classify surface ships and other objects in all weather conditions. Because of different radar reflection characteristics of the sea, the hull, superstructure, and masts as the vessel moves on the surface of the sea, vessels usually stand out in ISAR images. There can be enough radar information derived from ship motion, including pitching and rolling, to allow the ISAR operator to manually or automatically determine the type of vessel being observed. The U.S. Navy’s new P-8 Poseidon patrol aircraft carry the AN/APY-10 multi-mode radar system that includes both SAR and ISAR modes of operation.

The principles behind ship classification is described in detail in the 1993 MIT paper, “An Automatic Ship Classification System for ISAR Imagery,” by M. Menon, E. Boudreau and P. Kolodzy, which you can download at the following link:

https://www.ll.mit.edu/publications/journal/pdf/vol06_no2/6.2.4.shipclassification.pdf

You can see in the following example ISAR image of a vessel at sea that vessel classification may not be obvious to the casual observer. I can see that an automated vessel classification system is very useful.

Ship ISAR image

Source: Blanco-del-Campo, A. et al., http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5595482&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F7361%2F5638351%2F05595482.pdf%3Farnumber%3D5595482

Imaging Objects in Space: Another ISAR (also called “delayed Doppler”) application is the use of one or more large radio telescopes to generate radar images of objects in space at very long ranges. The process for accomplishing this was described in a 1960 MIT Lincoln Laboratory paper, “Signal Processing for Radar Astronomy,” by R. Price and P.E. Green.

Currently, there are two powerful ground-based radars in the world capable of investigating solar system objects: the National Aeronautics and Space Administration (NASA) Goldstone Solar System Radar (GSSR) in California and the National Science Foundation (NSF) Arecibo Observatory in Puerto Rico. News releases on China’s new FAST radio telescope have not revealed if it also will be able to operate as a planetary radar (see my 18 February 2016 post).

The 230 foot (70 meter) GSSR has an 8.6 GHz (X-band) radar transmitter powered by two 250 kW klystrons. You can find details on GSSR and the techniques used for imaging space objects in the article, “Goldstone Solar System Radar Observatory: Earth-Based Planetary Mission Support and Unique Science Results,” which you can download at the following link:

http://echo.jpl.nasa.gov/asteroids/Slade_Benner_Silva_IEEE_Proceedings.pdf

The 1,000 foot (305 meter) Arecibo Observatory has a 2.38 GHz (S-band) radar transmitter, originally rated at 420 kW when it was installed in 1974, and upgraded in 1997 to 1 MW along with other significant upgrades to improve radio telescope and planetary radar performance. You will find details on the design and upgrades of Arecibo at the following link:

http://www.astro.wisc.edu/~sstanimi/Students/daltschuler_2.pdf

The following examples demonstrate the capabilities of Arecibo Observatory to image small bodies in the solar system.

  • In 1999, this radar imaged the Near-Earth Asteroid 1999 JM 8 at a distance of about 5.6 million miles (9 million km) from Earth. The ISAR images of this 1.9 mile 3-km) sized object had a resolution of about 49 feet (15 meters).
  • In November 1999, Arecibo Observatory imaged the tumbling Main-Belt Asteroid 216 Kleopatra. The resulting ISAR images, which made the cover of Science magazine, showed a dumbbell-shaped object with an approximate length of 134.8 miles (217 kilometers) and varying diameters up to 58.4 miles (94 kilometers).

Asteroid image  Source: Science

More details on the use of Arecibo Observatory to image planets and other bodies in the solar system can be found at the following link:

http://www.naic.edu/general/index.php?option=com_content&view=article&id=139&Itemid=474

The NASA / Jet Propulsion Laboratory Asteroid Radar Research website also contains information on the use of radar to map asteroids and includes many examples of asteroid radar images. Access this website at the following link:

http://echo.jpl.nasa.gov

Miniaturization

In recent years, SAR units have become smaller and more capable as hardware is miniaturized and better integrated. For example, Utah-based Barnard Microsystems offers a miniature SAR for use in lightweight UAVs such as the Boeing ScanEagle. The firm claimed that their two-pound “NanoSAR” radar, shown below, weighed one-tenth as much as the smallest standard SAR (typically 30 – 200 pounds; 13.6 – 90.7 kg) at the time it was announced in March 2008. Because of power limits dictated by the radar circuit boards and power supply limitations on small UAVs, the NanoSAR has a relatively short range and is intended for tactical use on UAVs flying at a typical ScanEagle UAV operational altitude of about 16,000 feet.

Barnard NanoSARSource: Barnard Microsystems

ScanEagle_UAVScanEagle UAV. Source: U.S. Marine Corps.

Nanyang Technological University, Singapore (NTU Singapore) recently announced that its scientists had developed a miniaturized SAR on a chip, which will allow SAR systems to be made a hundred times smaller than current ones.

?????????????????????????????????????????????????????????Source: NTU

NTU reports:

“The single-chip SAR transmitter/receiver is less than 10 sq. mm (0.015 sq. in.) in size, uses less than 200 milliwatts of electrical power and has a resolution of 20 cm (8 in.) or better. When packaged into a 3 X 4 X 5-cm (0.9 X 1.2 X 1.5 in.) module, the system weighs less than 100 grams (3.5 oz.), making it suitable for use in micro-UAVs and small satellites.”

NTU estimates that it will be 3 to 6 years before the chip is ready for commercial use. You can read the 29 February 2016 press release from NTU at the following link:

http://media.ntu.edu.sg/NewsReleases/Pages/newsdetail.aspx?news=c7aa67e7-c5ab-43ae-bbb3-b9105a0cd880

With such a small and hopefully low cost SAR that can be integrated with low-cost UAVs, I’m sure we’ll soon see many new and useful radar imaging applications.

How Long Does it Take to Certify a Commercial Airliner?

Peter Lobner

After designing, developing, and manufacturing a new commercial airliner, I’m sure the airframe manufacturer has a big celebration on the occasion of the first flight. The ensuing flight test and ground static test programs are intended to validate the design, operating envelope, and maintenance practices and satisfy these and other requirements of the national certifying body, which in the U.S. is the Federal Aviation Administration (FAA). Meanwhile, airlines that have ordered the new aircraft are planning for its timely delivery and introduction into scheduled revenue service.

The time between first flight and first delivery of a new commercial airliner is not a set period of time. As you can see in the following chart, which was prepared by Brian Bostick (http://aviationweek.com/thingswithwings), there is great variability in the time it takes to get an airliner certified and delivered.

Time to certify an airliner

In this chart, the Douglas DC-9 has the record for the shortest certification period (205 days) with certification in November 1965. The technologically advanced supersonic Concorde had one of the longest certification periods (almost 2,500 days), with authorization in February 1976 to conduct a 16-month demonstration period with flights between Europe and the U.S. before starting regular commercial service.

The record for the longest certification period goes to the Chinese Comac ARJ21 twin-jet airliner, which is the first indigenous airliner produced in China. The first ARJ21 was delivered to a Chinese airline in November 2015. The ARJ is based on the DC-9 and reuses tooling provided by McDonnell Douglas for the licensed production of the MD-80 (a DC-9 variant) in China. I suspect that the very long certification period is a measure of the difficulty in establishing the complete aeronautical infrastructure needed to deliver an indigenous commercial airliner with an indigenous jet engine.

In the chart, compare the certification times for the following similar commercial airliners:

  • Four-engine, single aisle, long-range airliners: Boeing 707 (shortest), Douglas DC-8, Convair CV-880, Vickers VC-10, De Havilland Comet (longest)
  • Three-engine, single aisle, medium range airliners: Boeing 727 (shorter), Hawker Siddeley Trident (longer)
  • Two-engine, single aisle airliners: Douglas DC-9 (shortest), Boeing 737, Boeing 757, Airbus A320, British Aircraft Corporation BAC 1-11, Dassault Mercure, Caravelle (longest)
  • Two-engine, single aisle, short range regional jets: Embraer ERJ 145 (shortest), Bombardier CRJ-100, BAe 146, Fokker F-28, ERJ 170, Bombardier CS Series, Mitsubishi MRJ, Sukhoi Superjet, VFW-614, Comac ARJ21 (longest)
  • Four-engine, wide-body, long-range airliners: Boeing 747, Airbus A340, Airbus A380 (longest)
  • Three-engine, wide-body, long-range airliners: Douglas DC-10 (shorter), Lockheed L-1011 (longer)
  • Two-engine, wide-body airliners: Boeing 767 (shortest), Boeing 777, Airbus 350, Airbus A300, Boeing 787 (longest)

Time is money, so there is tremendous economic value in minimizing the time between first flight and first delivery. The first 16 aircraft at the top of the chart all enjoyed relatively short certification periods. This group, which includes many aircraft that appeared in the 1960s – 70, averaged about 400 days between first flight and first delivery.

More modern aircraft (blue bars in the chart representing aircraft appearing in 2000 or later) have been averaging about 800 days between first flight and first delivery (excluding ARJ21).

Solar Impulse 2 Preparing for the Next Leg of its Around-the-World Journey

Peter Lobner

In my 10 March 2015 post, I provided basic information of the remarkable Solar Impulse 2 aircraft and its mission to be the first aircraft to fly around the world on solar power. On 10 July 2015, I posted a summary of the first eight legs of the around the world flight, which started in Abu Dhabi on 9 March 2015 and ended on 3 July at Kalaeloa, a small airport outside Honolulu, Hawaii.

After arriving in Hawaii, the Solar Impulse team determined that the batteries had been damaged due to overheating on the first day of the Leg 8 flight and would have to be replaced. Solar Impulse reported the following root cause for the overheating:

“Since the plane had been exposed to harsh weather conditions from Nanjing to Nagoya, we decided to do a test flight before leaving for Hawaii. Having to perform a test flight followed by a mission flight had not been taken into account in the design process of the battery system, which did not allow the batteries to cool down in between the two” (flights).

By November 2015, the Solar Impulse engineers had upgraded the design of the whole battery system and integrated a battery cooling system. You can read the details on the Solar Impulse website at the following link:

http://blog.solarimpulse.com/post/133346944960/cool-batteries-solarimpulse

A further delay in starting Leg 9 was caused by the seasonal shortening of daylight hours in the Northern hemisphere. The late autumn and winter daylight hours weren’t long enough to allow the batteries to be fully recharged during the day along the planned route to the U.S. mainland and back to Abu Dhabi.

Solar Impulse 2 routeSource: Solar Impulse

On 26 February 2016, the upgraded Solar Impulse II made a successful “maintenance” flight in Hawaii. The flight lasted 93 minutes, reached an altitude of 8,000 feet (2,400 meters), and included tests of the stabilization and battery cooling systems.

Solar Impulse is planning to restart its around-the-world journey on 20 April 2016.

Solar Impulse composite photo over HawaiiSource: Solar Impulse

You can subscribe to news releases from the Solar Impulse team at the following link:

http://www.solarimpulse.com/subscribe

Virgin Galactic’s SpaceShipTwo is a Step Closer to Operational Commercial Spaceflights from Spaceport America

Peter Lobner

In my 13 April 2015 post, I provided an introduction to three U.S. commercial, suborbital human spaceflight programs. You may recall that Virgin Galactic’s first SpaceShipTwo was destroyed in an in-flight accident on 31 October 2014. The in-flight breakup of SpaceShipTwo resulted from the premature unlocking of the wing, which allowed the wing to move to the high-drag “feathered” position while the ship was accelerating through the transonic region (i.e., not yet supersonic). The pilot was seriously injured and the copilot was killed in this accident. You can find the Executive Summary of the National Transportation Safety Board’s (NTSB’s) accident report at the following link:

http://www.ntsb.gov/investigations/AccidentReports/Pages/AAR1502.aspx

More information from the 28 July 2015 NTSB Board meeting is available at the following link:

http://www.ntsb.gov/news/events/Pages/2015_spaceship2_BMG.aspx

Today, Virgin Galactic unveiled the second SpaceShipTwo at the Mojave Air and Space Port in California. The ship was named, Virgin Spaceship (VSS) Unity by Professor Stephen Hawking, who said in a recorded speech, “I would be very proud to fly on this spaceship.”

VSS_Unity_Reveal Source: Virgin Galactic

The second SpaceShipTwo, which was under construction before the crash of its predecessor, is very similar to the first article, but with the following significant changes:

  • Feathering system: Virgin Galactic reports, “With regard to the accident specifically, we have made one structural change to the vehicle, which is to add a mechanical inhibit to the featherlock system that would prevent that from ever being inadvertently opened at the wrong time in flight.”
  • Rocket fuel: Virgin Galactic switched from a hydroxyl-terminated polybutadiene (HTBP) rubber-based solid fuel to a polyamide (plastic)-based fuel for the rocket motor on the first SpaceShipTwo. For the second SpaceShipTwo, Virgin Galactic announced in October 2015 that it was switching back to HTBP-based fuel.

Virgin Galactic has not yet announced other design and/or operational changes.

Like the first SpaceShipTwo, VSS Unity will go through an extensive test program that starts with “captive carry” flights on the WhiteKnightTwo aircraft.

SpaceShipTwo carriedWhiteKnightTwo carrying SpaceShipTwo; source: Virgin Galactic

The next series of tests include unpowered (gliding) flights after being dropped from WhiteKnightTwo, and finally, powered tests that will validate the flight envelope of SpaceShipTwo. At the conclusion of this testing program, VSS Unity may become the first commercial space vehicle to make regular, suborbital flights with paying passengers.

You can keep track of the progress being made at the Virgin Galactic website at the following link:

http://www.virgingalactic.com

The commercial flights will be conducted from Spaceport America, which is located in the desert east of Truth of Consequences, NM. You can find information of the Spaceport and make arrangements for a tour at the following website.

http://spaceportamerica.com

I visited Spaceport America in October 2015 and found it to be an impressive, but lonely facility, just waiting for the start of regular commercial space missions. The main hanger, shown below, housed only a SpaceShipTwo mockup and the enormous runway was silent.

All that will change after VSS Unity completes its test program and begins the operational phase of commercial human spaceflight in the desert of southern New Mexico. These are exciting times!

Spaceport pic 1

Spaceport pic 2

Spaceport pic 3Source, three photos: Author

The Magnus Effect and its Broad Applications: From Sports to Ballistics to Dam Busting in WW II

Peter Lobner

The Magnus effect occurs when a moving spherical or cylindrical body has a spin. The observed effect is that the moving, spinning body moves away from the intended direction of travel. The spin alters the airflow around the moving body and, by conservation of momentum, generates the Magnus force. In the case of a flying (thrown) backspinnning round body shown below, the Magnus force is a lift.

Sketch_of_Magnus_effectSource: Wikipedia

The Magnus force is named for German physicist Heinrich Gustav Magnus, who described the effect in 1852. Other scientists had described the effect long before Magnus, notably Isaac Newton (in 1672) and British mathematician and ballistic researcher Benjamin Robins (in 1742), but it was Magnus who got the honor.

We can see the Magnus effect at work in sports and in other applications discussed below.

Baseball

The pitcher can impart a spin in a selected direction to throw a curveball, slider or other pitch. Major League Baseball (MLB) uses a system called PITCHf/x, which is installed in every MLB stadium, to track the speed and trajectory of pitched baseballs. The system calculates two values, BRK and PFX, related to the Magnus effect:

  • BRK is a measure of the amount of bend in the trajectory at its greatest distance from a straight line
  • PFX is a measure of the deflection of the baseball due to the spin and drag forces from the path it would have taken under the influence of gravity alone

You can find more information on PITCHf/x at the following links:

https://en.wikipedia.org/wiki/PITCHf/x

and,

http://www.fangraphs.com/library/misc/pitch-fx/

Golf

A backspin on a golf ball creates a lift, as shown in the diagram above, helping to extend the range of the shot. A topspin has the opposite effect, shortening the ball’s trajectory. A spin about a vertical or diagonal axis results in a slice or hook to the right or left, invariably putting the ball into deep grass or some other course hazard. I have trouble visualizing how a golfer imparts a spin about the ball’s vertical or diagonal axis, but apparently it is a lot easier that you might think.

Extreme basketball

Thanks to Dave Groce, who forwarded the following link to a video that demonstrates how the Magnus effect helped a group in Tasmania sink a basketball from the top of a dam.  I have a feeling that there were a lot more basketballs at the bottom of the dam than are shown in the video.

https://www.youtube.com/watch?v=2OSrvzNW9FE

Ballistics

A spinning bullet will encounter a Magnus force if it yaws slightly in flight (i.e., direction of the central axis of the bullet is slightly different than its direction of flight, or velocity vector) or is shot into a crosswind. The direction of the Magnus force will depend on the direction of yaw or crosswind. A sniper shooting at long range needs to consider the Magnus effect.

WW II Dambusters

As reported on the Bomber Command website (http://www.bombercommandmuseum.ca/damsraid1.html):

 “The Dams Raid was conceived in the brilliant mind of Barnes Wallis, an experienced aircraft designer. Wallis had designed the very successful Wellington bomber that had been operational since the beginning of the war and, in his spare time, he searched for weaknesses in the enemy’s industrial infrastructure. The hydroelectric dams of the highly Ruhr Valley became his focus.

He devised a cylindrical, 9,500 pound weapon that could be dropped at low level while rotating backwards at 500 rpm. Released from a height of 60 feet, about 450 yards from the dam, and at a speed of 230 miles per hour, the weapon would then skip along the water (and over any torpedo nets) until it struck the dam wall, the spinning maintaining the weapon’s stability and slowing it down.

The backward rotation would then cause the cylinder to roll down the dam wall where it would explode at a predetermined depth. The wall would be weakened and the great weight of water would cause the dam to collapse.”

Experiments performed by Wallis demonstrated that the Magnus effect gave aerodynamic lift to the bomb and thereby increased the number of bounces before the bomb either struck the dam or stopped bouncing and sank.

p_damsraid1bSource: Bomber Command Museum

There is much more information on Sir Barnes Wallis and the Dams Raid on the Bomber Command website.

For more information, I also recommend the book, “Dam Busters: The True Story of the Inventors and Airmen Who Led the Devastating Raid to Smash the German Dams in 1943,” by James Holland, published by Grove Press, New York, and available in paperback in 2014, ISBN-13: 978-0802122780.

The Complexity of a WW II P-47 Thunderbolt’s Powerplant

Peter Lobner

The P-47 Thunderbolt, built by Republic Aviation, was a powerful WW II fighter that was capable of operating effectively at high-altitude as a long-range bomber escort or at low altitude as a fighter bomber. That tactical flexibility was enabled by its turbocharged Pratt & Whitney Double Wasp R-2800, two-row, 18-cylinder radial engine. A representative P-47D is shown in the following photo.

P-47D_DSC09072Source: Author photo

Basic specifications for a P-47D are listed below (Source: National Museum of the USAF):

  • Engine: One Pratt & Whitney R-2800 radial rated at 2,430 hp
  • Maximum speed: 433 mph
  • Cruising speed: 350 mph
  • Range: Approx. 1,100 miles with drop tanks
  • Ceiling: 42,000 ft.
  • Armament: Eight .50-cal machine guns and 2,500 lbs. of bombs or rockets
  • Span: 40 ft. 9 in.
  • Length: 36 ft. 2 in.
  • Height: 14 ft. 8 in.
  • Weight: 17,500 lbs. maximum

The basic engine installation can be seen in the following illustration of a P-47 without its engine cowling:

P-47 no engine cowlingSource: https://www.flickr.com/photos/wingmanphoto/7166461822/

The R-2800 engine is turbocharged, with the turbocharger, intercooler, and related subsystems all located behind the pilot. There is a lot of intake ductwork needed to get ambient air routed from the main air duct intake immediately under the engine to the turbocharger and intercooler and then back to the carburetors on the engine.

  • The air entering the turbocharger is compressed and, in the process, is heated. This air passes through the intercooler where it is cooled before being directed back to the engine and the carburetors for each of the 18 cylinders.
  • The air entering the intercooler cools the compressed air from the turbocharger’s compressor and then is discharged through exit doors on the sides of the P-47 fuselage, aft of the pilot.

Similarly, there is a lot of exhaust system ductwork needed to collect the exhaust from 18 cylinders into tailpipes and then route it back to drive the turbine section of the turbocharger and then be discharged via the main exhaust on the bottom of the P-47 fuselage.

These basic intake air and exhaust flow paths are shown in the following diagram.

P-47 powewrtrain_DSC_5382 cropSource: National Museum of the USAF

While visiting the National Museum of WW II Aviation in Colorado Springs, CO, I saw the complete P-47 powertrain shown in the following photo. The engine is at the extreme left, the turbocharger is at the extreme right, and the intercooler is at the point where the carburetor air duct (top) converges in a “V” with the main air duct (bottom). The darker exhaust tailpipes flank the main air duct along the bottom of the powerplant.

P-47 powertrain_DSC_7265-66 panoSource: Author photo

From the front, the Pratt & Whitney R-2800 dominates the view in the following photo. The main air duct intake is visible under the engine. The carburetor air duct (top), and the main air duct and darker exhaust tailpipe (bottom) are visible to the left, behind the engine.

P-47 powertrain_DSC_7258Source: Author photo

From the back of the powerplant, the turbocharger dominates the view in the following photo. As shown by the arrows, intake air enters the compressor section of the turbocharger from the top (grey arrow) and exits via the volute (red arrow), headed for the intercooler. The darker exhaust tailpipe can be seen connecting to the turbine secion of the turbocharger (below the red arrow) and exhausting under the turbocharger (yellow arrow).

P-47 powertrain_DSC_7262Source: Author photo

The following photo shows more clearly the connection of the exhaust tailpipes to the turbine section of the turbocharger and the exhaust point from the turbine section (beneath the P-47’s fuselage). Also shown is the intercooler, which is a heat exchanger that receives cool ambient air from the main air intake duct and warm, compressed air from the turbocharger’s compressor discharge (red arrow). After cooling the compressed air headed for the carburetors, the intercooler exhausts through rectangular ducts on the sides of the P-47 (yellow arrow).

P-47 powertrain_DSC_7260Source: Author photo

A better view of the intercooler exhaust duct (one of two) is shown in the following photo.

P-47 powertrain_DSC_7268Source: Author photo

So there you have it. While the P-47 looks bulky , this is largely due to the use of a big radial engine plus all of the ductwork, intercooler and turbocharger hardware packaged inside the fuselage.