Category Archives: Aviation

Paul Allen’s Stratolaunch Aircraft Makes its First Flight, but With an Uncertain Business Plan

Aeronautical, All Posts, Aviation, Engineering, Spacecraft and Missions, , , , , , ,

Peter Lobner, updated 19 March 2020

Background

The firm Northrop Grumman Innovation Systems (formerly Orbital ATK, and before that, Orbital Sciences Corporation)  was the first to develop a commercial, air-launched rocket capable of placing payloads into Earth orbit.  Initial tests of their modest-size Pegasus launch vehicle were made in 1990 from the NASA B-52 that previously had been used as the “mothership” for the X-15 experimental manned space plane and many other experimental vehicles.

Since 1994, Orbital ATK has been using a specially modified civilian Lockheed L-1011 TriStar, a former airliner renamed Stargazer, as a mothership to carry a Pegasus launch vehicle to high altitude, where the rocket is released to fly a variety of missions, including carrying satellites into orbit.  With a Pegasus XL  as its payload (launch vehicle + satellite), Stargazer is lifting up to 23,130 kg (50,990 pounds) to a launch point at an altitude of about 12.2 km (40,000 feet).

Orbital ATK’s Pegasus XL rocket released from Stargazer.  
Source: NASA / http://mediaarchive.ksc.nasa.gov

You can watch a 2015 video celebrating 25 years of Orbital ATK’s Pegasus air-launched rocket at the following link: https://www.youtube.com/watch?v=0L47cpXTzQU

Paul Allen’s firm Stratolaunch Systems Corporation (https://www.stratolaunch.com) was founded in 2011 to take this air-launch concept to a new level with their giant, twin-fuselage, six-engine Stratolaunch carrier aircraft.  The aircraft has a wingspan of 385 feet (117 m), which is the greatest of any aircraft ever built, a length of 238 feet (72.5 m), and a height of 50 feet (15.2 m) to the top of the vertical tails. The empty weight of the aircraft is about 500,000 pounds (226,796 kg).  It is designed for a maximum takeoff weight of 1,300,000 pounds (589,670 kg), leaving about 550,000 pounds (249,486 kg) for its payload and the balance for fuel and crew.  It will be able to carry multiple launch vehicles on a single mission to a launch point at an altitude of about 35,000 feet (10,700 m).  A mission profile for the Stratolaunch aircraft is shown in the following diagram.

Typical air-launch mission profile. Source: Stratolaunch Systems

Stratolaunch rollout – 2017

Built by Scaled Composites, the Stratolaunch aircraft was unveiled on 31 May 2017 when it was rolled out at the Mojave Air and Space Port in Mojave, CA.  Following is a series of photos from Stratolaunch Systems showing the rollout.

Stratolaunch ground tests – 2017 to 2019

Ground testing of the aircraft systems started after rollout. By mid-September 2017, the first phase of engine testing was completed, with all six Pratt & Whitney PW4000 turbofan engines operating for the first time.  The first low-speed ground tests conducted in December 2017 reached a modest speed of 25 knot (46 kph).  By January 2019, the high-speed taxi tests had reached a speed of about 119 knots (220 kph) with the nose wheel was off the runway, almost ready for lift off. Following is a series of photos from Stratolaunch Systems showing the taxi tests.

Stratolaunch first flight

The Stratolaunch aircraft, named Roc, made an unannounced first flight from the Mojave Air & Space Port on 13 April 2019.  The aircraft stayed aloft for 2.5 hours, reached a peak altitude of 17,000 feet (5,180 m) and a top speed of 189 mph (304 kph). The following series of photos show the Stratolaunch aircraft during its first flight.

Source, above two photos:  Stratolaunch Systems
Source:  REUTERS/Gene Blevins/File Photo
Landing at the conclusion of the first flight.   Source:  Stratolaunch Systems

Stratolaunch posted an impressive short video of the first flight, which you can view here:

Stratolaunch family of launch vehicles: ambitious plans, but subject to change

In August 2018, Stratolaunch announced its ambitious launch vehicle development plans, which included the family of launch vehicles shown in the following graphic:

  • Up to three Pegasus XL launch vehicles from Northrop Grumman Innovation Systems (formerly Orbital ATK) can be carried on a single Stratolaunch flight. Each Pegasus XL is capable of placing up to 370 kg (816 lb) into a low Earth orbit (LEO, 400 km / 249 mile circular orbit).
  • Medium Launch Vehicle (MLV) capable of placing up to 3,400 kg (7,496 lb) into LEO and intended for short satellite integration timelines, affordable launch and flexible launch profiles.  MLV was under development and first flight was planned for 2022.
  • Medium Launch Vehicle – Heavy, which uses three MLV cores in its first stage. That vehicle would be able to place 6,000 kg (13,228 lb) into LEO.  MLV-Heavy was in the early development stage.
  • A fully reusable space plane named Black Ice, initially intended for orbital cargo delivery and return, with a possible follow-on variant for transporting astronauts to and from orbit.  The space plane was a design study.

Stratolaunch was developing a 200,000 pound thrust, high-performance, liquid fuel hydrogen-oxygen rocket engine, known as the “PGA engine”, for use in their family of launch vehicles.  Additive manufacturing was being widely used to enable rapid prototyping, development and manufacturing.   Successful tests of a 100% additive manufactured major subsystem called the hydrogen preburner were conducted in November 2018.

Stratolaunch Systems planned family of launch vehicles announced in August 2018.
Source: Stratolaunch Systems

After Paul Allen’s death on 15 October 2018, the focus of Stratolaunch Corp was greatly revised. On 18 January 2019, the company announced that it was ending work on its own family of launch vehicles and the PGA rocket engine. The firm announced, “We are streamlining operations, focusing on the aircraft and our ability to support a demonstration launch of the Northrop Grumman Pegasus XL air-launch vehicle.”    

You’ll find an article describing Stratolaunch Systems’ frequently changing launch vehicle plans in an article on the SpaceNews website here:

https://spacenews.com/stratolaunch-abandons-launch-vehicle-program/

What is the future for Stratolaunch?

Air launch offers a great deal of flexibility for launching a range of small-to-medium sized satellites and other aerospace vehicles. With only the Pegasus XL as a launch vehicle, and with Northrop Grumman having their own Stargazer carrier aircraft for launching the Pegasus XL, the business case for the Stratolaunch aircraft has been greatly weakened.    

Stratolaunch’s main competition:  The Northrop Grumman Stargazer at the Mojave Air and Space Port in January 2019, available for its next Pegasus XL launch mission.  Source: Author’s photo

Additional competition in the airborne launch services business will come in 2020 from Richard Branson’s firm Virgin Orbit, with its airborne launch platform Cosmic Girl, a highly-modified Boeing 747, and its own launch vehicle, known as LauncherOne.  Successful drop tests of LauncherOne were conducted in 2019.  The first launch to orbit is expected to occur in 2020.  You’ll find more information on the Virgin Orbit website here: https://virginorbit.com

An inert LauncherOne rocket falls away from its 747 carrier aircraft in a July 2019 drop test.  Source: Virgin Orbit

Additional competition for small satellite launch services comes from the newest generation of small orbital launch vehicles, like Electron (Rocket Lab, New Zealand) and Prime (Orbix, UK), which are expected to offer low price launch services from fixed land-based launch sites.  Electron is operational now, and achieved six successful launches in six attempts in 2019. Prime is expected to enter service in 2021.  

In the cost competitive launch services market, Stratolaunch does not seem to have an advantage with only the Pegasus XL in its launch vehicle inventory.  Hopefully, they have something else up their sleeve that will take advantage of the remarkable capabilities of the Stratolaunch carrier aircraft.

19 March 2020 Update:  Stratolaunch change of ownership

Several sources reported on 11 October 2019 that Stratolaunch Systems had been sold by its original holding company, Vulcan Inc., to an undisclosed new owner. Two months later, Mark Harris, writing for GeekWire, broke the news that the private equity firm Cerberus Capital Management was the new owner.  It appears that Jean Floyd, Stratolaunch’s president and CEO since 2015, remains in his roles for now. Michael Palmer, Cerberus’ managing director, was named Stratolaunch’s executive vice president. You can read Mark Harris’ report here: https://www.geekwire.com/2019/exclusive-buyer-paul-allens-stratolaunch-space-venture-secretive-trump-ally/

It will be interesting to watch as the new owners reinvent Stratolaunch Systems for the increasingly competitive market for airborne launch services. 

Airbus Delivers its 10,000th Aircraft

Aeronautical, All Posts, Aviation, Commercial aviation, Transportation, , , , , ,

Peter Lobner

Airbus was founded on 18 December 1970 and delivered its first aircraft, an A300B2, to Air France on 10 May 1974. This was the world’s first twin-engine, wide body (two aisles) commercial airliner, beating Boeing’s 767, which was not introduced into commercial service until September 1982. The A300 was followed in the early 1980s by a shorter derivative, the A310, and then, later that decade, by the single-aisle A320. The A320 competed directly with the single-aisle Boeing 737 and developed into a very successful family of single-aisle commercial airliners: A318, A319, A320 and A321.

On 14 October 2016, Airbus announced the delivery of its 10,000th aircraft, which was an A350-900 destined for service with Singapore Airlines.

EVE-1236Source: Airbus

In their announcement, Airbus noted:

“The 10,000th Airbus delivery comes as the manufacturer achieves its highest level of production ever and is on track to deliver at least 650 aircraft this year from its extensive product line. These range from 100 to over 600 seats and efficiently meet every airline requirement, from high frequency short haul operations to the world’s longest intercontinental flights.”

You can read the complete Airbus press release at the following link:

http://www.airbus.com/presscentre/pressreleases/press-release-detail/detail/-9b32c4364a/

As noted previously, Airbus beat Boeing to the market for twinjet, wide-body commercial airliners, which are the dominant airliner type on international and high-density routes today. Airbus also was an early adopter of fly-by-wire flight controls and a “glass cockpit”, which they first introduced in the A320 family.

In October 2007, the ultra-large A380 entered service, taking the honors from the venerable Boeing 747 as the largest commercial airliner.   Rather than compete head-to-head with the A380, Boeing opted for stretching its 777 and developing a smaller, more advanced and more efficient, all-composite new airliner, the 787, which was introduced in airline service 2011.

Airbus countered with the A350 XWB in 2013. This is the first Airbus with fuselage and wing structures made primarily of carbon fiber composite material, similar to the Boeing 787.

The current Airbus product line comprises a total of 16 models in four aircraft families: A320 (single aisle), A330 (two aisle wide body), A350 XWB (two aisle wide body) and A380 (twin deck, two aisle wide body). The following table summarizes Airbus commercial jet orders, deliveries and operational status as of 30 November 2016.

Airbus orders* Includes all models in this family. Source: https://en.wikipedia.org/wiki/Airbus

Boeing is the primary competitor to Airbus. Boeing’s first commercial jet airliner, the 707, began commercial service Pan American World Airways on 26 October 1958. The current Boeing product line comprises five airplane families: 737 (single-aisle), 747 (twin deck, two aisle wide body), 767 (wide body, freighter only), 777 (two aisle wide body) and 787 (two aisle wide body).

The following table summarizes Boeing’s commercial jet orders, deliveries and operational status as of 30 June 2016. In that table, note that the Boeing 717 started life in 1965 as the Douglas DC-9, which in 1980 became the McDonnell-Douglas MD-80 (series) / MD-90 (series) before Boeing acquired McDonnell-Douglas in 1997. Then the latest version, the MD-95, became the Boeing 717.

Boeing commercial order status 30Jun2016

Source: https://en.wikipedia.org/wiki/Boeing_Commercial_Airplanes

Boeing’s official sales projections for 2016 are for 740 – 745 aircraft. Industry reports suggest a lower sales total is more likely because of weak worldwide sales of wide body aircraft.

Not including the earliest Boeing models (707, 720, 727) or the Douglas DC-9 derived 717, here’s how the modern competition stacks up between Airbus and Boeing.

Single-aisle twinjet:

  • 12,805 Airbus A320 family (A318, A319, A320 and A321)
  • 14,527 Boeing 737 and 757

Two-aisle twinjet:

  • 3,260 Airbus A300, A310, A330 and A350
  • 3,912 Boeing 767, 777 and 787

Twin aisle four jet heavy:

  • 696 Airbus A340 and A380
  • 1,543 Boeing 747

These simple metrics show how close the competition is between Airbus and Boeing. It will be interesting to see how these large airframe manufacturers fare in the next decade as they face more international competition, primarily at the lower end of their product range: the single-aisle twinjets. Former regional jet manufacturers Bombardier (Canada) and Embraer (Brazil) are now offering larger aircraft that can compete effectively in some markets. For example, the new Bombardier C Series is optimized for the 100 – 150 market segment. The Embraer E170/175/190/195 families offer capacities from 70 to 124 seats, and range up to 3,943 km (2,450 miles).  Other new manufacturers soon will be entering this market segment, including Russia’s Sukhoi Superjet 100 with about 108 seats, the Chinese Comac C919 with up to 168 seats, and Japan’s Mitsubishi Regional Jet with 70 – 80 seats.

At the upper end of the market, demand for four jet heavy aircraft is dwindling. Boeing is reducing the production rate of its 747-8, and some airlines are planning to not renew their leases on A380s currently in operation.

It will be interesting to watch how Airbus and Boeing respond to this increasing competition and to increasing pressure for controlling aircraft engine emissions after the Paris Agreement became effective in November 2016.

Status of Ukraine’s Giant Transport Aircraft: Antonov An-124 and An-225

Aeronautical, All Posts, Aviation, Commercial aviation, Military technology, , , ,

Peter Lobner, updated 26 September 2023

Historically, the Antonov Design Bureau was responsible for the design and development of large military and civil transport aircraft for the former Soviet Union. With headquarters and production facilities in and around Kiev, this Ukrainian aircraft manufacturing and servicing firm is now known as Antonov State Company. The largest of the jet powered transport aircraft built by Antonov are the four-engine An-124 and the even larger six-engine An-225.

An-124 Ruslan (NATO name: Condor)

The An-124 made its first flight in December 1982 and entered operational service in 1986. This aircraft is a counterpart to the Lockheed C-5A, which is the largest U.S. military transport aircraft. A comparison of the basic parameters of these two aircraft is presented in the following table.

An-124 vs C-5A_Aviatorjoedotnet

Source: aviatorjoe.net

As you can see in this comparison, the An-124 is somewhat larger than the C-5A, which has a longer range, but at a slower maximum speed.

The An-124 currently is operated by the Russian air force and also by two commercial cargo carriers: Ukraine’s Antonov Airlines and Russia’s Volga-Dnepr Airlines. The civil An-124-100 is a commercial derivative of the military An-124. The civil version was certified in 1992, and meets all current civil standards for noise limits and avionic systems.

In their commercial cargo role, these aircraft specialize in carrying outsized and/or very heavy cargo that cannot be carried by other aircraft. These heavy-lift aircraft serve civil and military customers worldwide, including NATO and the U.S. military. I’ve seen an An-124s twice on the tarmac at North Island Naval Station in San Diego. In both cases, it arrived in the afternoon and was gone before sunrise the next day. Loading and/or unloading occurred after dark.

An-124_RA-82028_09-May-2010

An-124-100. Source: Wikimedia Commons

As shown in the following photo, the An-124 can retract its nose landing gear and “kneel” to facilitate cargo loading through the raised forward door.

An-124_ramp down

An-124-100. Source: Mike Young / Wikimedia Commons

The following diagram shows the geometry and large size of the cargo hold on the An-124. The built-in cargo handling equipment includes an overhead crane system capable of lifting and moving loads up to 30 metric tons (about 66,100 pounds) within the cargo hold. As shown in the diagram below, the cargo hold is about 36.5 meters (119.7 feet) long, 6.4 meters (21 feet) wide, and the clearance from the floor to the ceiling of the cargo hold is 4.4 meters (14.4 feet). The installed crane hoists may reduce overhead clearance to 3.51 meters (11.5 feet).

An-124-diagram_tcm87-4236

An-124-100 cargo hold dimensions. Source: aircharterservice.com

An-124_takeoff

An-124-100. Source: aircharterservice.com

Production of the An-124 was suspended following the Russian annexation of Crimea in 2014 and the ongoing tensions between Russia and Ukraine. In spite of repeated attempts by Ukraine to restart the An-124 production line, it appears that Antonov may not have the resources to restart An-124 production. 

An-225 Mriya

The An-225 was adapted from the An-124 and significantly enlarged to serve as the carrier aircraft for the Soviet space shuttle, the Buran. The relative sizes of the An-124 and An-225 are shown in the following diagram, with a more detailed comparison in the following table.

An-124 & 225 planform comparison

An-124 & -225 comparison. Source: Airvectors.com

An-124 & 225 comparison

An-124 & -225 comparison. Source: aviatorjoe.net

The only An-225 ever produced made its first flight in December 1988. It is shown carrying the Buran space shuttle in the following photo.

AN-225 & Buran

An-225 carrying Buran space shuttle. Source: fcba.tumblr.com

After the collapse of the Soviet Union in 1991 and the cancellation of the Buran space program, the An-225 was mothballed for eight years until Antonov Airlines reactivated the aircraft for use as a commercial heavy-lift transport. In this role, it can carry ultra-heavy / oversize cargo weighing up to 250 metric tons (551,000 pounds).

An-225 gear down

An-225 Mriya. Source: AntonovAn-225 gear up

In 2016, it appeared that the giant An-225 was about to enter series production after Antonov and Aerospace Industry Corporation of China (AICC) signed a deal on 30 August 2016 for An-225 production in China. At the time, it was expected that the first new An-225 could be produced in China as early as in 2019. A Chinese An-225 would modernize and greatly expand China’s military and civil airlift capabilities.  While it isn’t clear how that airlift capability would be employed, it certainly will improve China’s ability to deliver heavy machinery, bulk material, and many personnel anywhere in the world, including any location in and around the South China Sea that has an adequate runway.  

26 September 2023 update

In late February 2022, the An-225 was destroyed by invading Russian forces at the Hostomel Airport near Kyiv, where the giant aircraft was undergoing regular maintenance intended to support its continued operational use into the 2030s. 

Source: Oleksii Samsonov / KCSA via The Moscow Times

Source: Oleksii Samsonov via Aero Times

A second unfinished airframe of the An-225, originally intended for ground testing, still exists at an unspecified location.  That second airframe, plus serviceable parts salvaged from the original An-225, would form a starting point for building another flyable AN-225.

Time will tell if an An-225 can be rebuilt.  I hope we’ll see Mriya fly again.

For more information

Video

Modern Airships

Aeronautical, All Posts, Aviation, Commercial aviation, Military technology, Transportation

This August 2016 post, which included links to 14 articles on specific historic and modern  airships, was replaced in August 2019.

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

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

Best regards,

Peter Lobner

August 2019

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

Aeronautical, All Posts, Aviation, , ,

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

Aeronautical, All Posts, Aviation, Engineering, ,

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.

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

Aeronautical, All Posts, Aviation, Power Generating Technology - Alternate,

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

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

Aeronautical, All Posts, Aviation, , , , , , , ,

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.