Electra Tests Hybrid-Electric Propulsion System

MIflyer

1st Sergeant
4,520
6,853
May 30, 2011
Cape Canaveral
From Avweb:

"Electra.aero announced last week that it has successfully completed a fully integrated test of its hybrid-electric propulsion system. According to the company, the technology was developed for its nine-passenger electric short takeoff and landing (eSTOL) aircraft concept. Propulsion system testing was conducted at Electra's facility in Switzerland.

"Tightly coupling airframe and propulsion systems is the hallmark of Electra's unique and scalable approach to providing net-zero emissions for regional and transport-category aircraft by 2050," said JP Stewart, Electra vice president and general manager. "Electra's eSTOL aircraft uses this patent-pending technology for the urban and regional aircraft market, allowing a reduction of the 5 billion tons of CO2 created by inefficient ground transport in personal cars every year."

"Electra says its hybrid system, which is currently being integrated into the company's demonstrator aircraft, uses "a combination of high-power battery packs and a turbogenerator to power eight electric motors and propellers." For its nine-passenger hybrid eSTOL design, Electra is targeting a 400-NM range, 2,500-pound payload and 175-knot cruise speed. The company is participating in initiatives including NASA's Advanced Air Mobility (AAM) National Campaign and the U.S. Air Force's Agility Prime program."
Screenshot 2022-09-13 at 14-23-37 Electra Tests Hybrid-Electric Propulsion System - AVweb.png
 

Jabberwocky

Staff Sergeant
1,230
437
Jul 24, 2005
Japan
Heart Aerospace, which is Swedish, also made an electric aircraft announcement in the last few days.

They've revised their HS-19 19-seat design into a 30-seat design.

At the moment, they're targeting 200 km range (with allowances and reserves) for all electric (battery only) operation, 400 km for hybrid electric operation and 800 km for reduced passenger capacity hybrid electric operation. First flight scheduled for 2026. Entry into service by 2028.

Air Canada just became a shareholder, and ordered 30 aircraft. United Airlines and Mesa Air Group have also taken shareholdings and have provisional orders for 100 aircraft each. LoI have been signed with Braathens, Sounds Air, Icelandair and SAS.

There's a lot of money outside of aerospace investing in Heart as well. Bill Gates' investment vehicle has pumped some money in, as have a bunch of European investment funds (state and private) focused on clean transport/environmental initiatives.
 

MIflyer

1st Sergeant
4,520
6,853
May 30, 2011
Cape Canaveral
Those engines do look nifty, but that airframe sure could do with some work
The Structures engineers are quite pleased and the Maintenance folks are positively ecstatic. The Cargo people are very happy that storage areas are easily accessible and that all passengers will have a window. The Aerodynamics guys have looked at it and concluded they are not involved.
 

J_P_C

Senior Airman
563
1,295
Feb 21, 2010
Warsaw
how it sounds: hybrid propulsion - we are converting chemical bonds energy stored in fuel through mechanical means to electrical energy to convert it in mechanical energy - is anyone see some imperfection in this??? nah for sure we are far from being "socially insane".....
 

J_P_C

Senior Airman
563
1,295
Feb 21, 2010
Warsaw
The Structures engineers are quite pleased and the Maintenance folks are positively ecstatic. The Cargo people are very happy that storage areas are easily accessible and that all passengers will have a window. The Aerodynamics guys have looked at it and concluded they are not involved.
Sir let me congratulate to you this brilliant! summary....
 

nuuumannn

Major
9,749
8,321
Oct 12, 2011
Nelson
The Structures engineers are quite pleased and the Maintenance folks are positively ecstatic. The Cargo people are very happy that storage areas are easily accessible and that all passengers will have a window. The Aerodynamics guys have looked at it and concluded they are not involved.

:laughing3: Brilliant!
 

MIflyer

1st Sergeant
4,520
6,853
May 30, 2011
Cape Canaveral
how it sounds: hybrid propulsion - we are converting chemical bonds energy stored in fuel through mechanical means to electrical energy to convert it in mechanical energy
Several years ago someone came up with a hybrid drone that used electric motors for VTOL but flew conventionally once aloft. That makes some sense. Charging the batteries to provide additional power required for takeoff and landing is directly analogous to the electric motors used in hybrid automobiles, which are used as "afterburners" to give otherwise excessively puny engines adequate performance. They have also gone to using hybrid locomotives as switch engines in RR yards, since they can power them from batteries and use a large diesel pickup truck engine to charge the batteries that starts and stops automatically as required rather than running a much larger diesel engine 24/7 for moving RR cars short distances.

But how this concept applies to an aircraft with a 2500 mile range, with electric motors as the only propulsion, and powered by a internal combustion engine, I do not think I understand.
 

nuuumannn

Major
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8,321
Oct 12, 2011
Nelson
There are a few companies toying with the concept at the moment, some of them more fanciful than others, but it's an idea that is gaining traction. One concept relies of hydrogen as a fuel, with small electric motors being retrofitted into the nacelles in place of the gas turbines in turbo prop airliners. Here's Universal Hydrogen's concept for Dash 8s and ATRs:


MagniX Aero's electric motors:

 

J_P_C

Senior Airman
563
1,295
Feb 21, 2010
Warsaw
Several years ago someone came up with a hybrid drone that used electric motors for VTOL but flew conventionally once aloft. That makes some sense. Charging the batteries to provide additional power required for takeoff and landing is directly analogous to the electric motors used in hybrid automobiles, which are used as "afterburners" to give otherwise excessively puny engines adequate performance. They have also gone to using hybrid locomotives as switch engines in RR yards, since they can power them from batteries and use a large diesel pickup truck engine to charge the batteries that starts and stops automatically as required rather than running a much larger diesel engine 24/7 for moving RR cars short distances.

But how this concept applies to an aircraft with a 2500 mile range, with electric motors as the only propulsion, and powered by a internal combustion engine, I do not think I understand.
i've spend last 12 months working in project initially assumed hybrid propulsion - so far conclusion is that applicability of this idea is limited to aircrafts up to around 100-120 kg MTOW, only because of distributed propulsion application - like UHP drones. Going bigger is bad idea due pretty bad mass gain and hopeless battery performance.
 

MIflyer

1st Sergeant
4,520
6,853
May 30, 2011
Cape Canaveral
I did a study for Kennedy Space Center on the probability of failure of composite pressure vessels. I found that a high pressure (3600 PSI) Compressed Natural Gas tank capable of holding the same energy as 10 gal of gasoline weighs 100 lb, empty, and is about 3 ft long and 18 inches long; full of CNG, the tank weighs about 150 lb.

For a tank holding compressed hydrogen gas, the same figures apply to a tank capable of holding the energy equivalent of 2 gallons of gasoline.

CNG is an entirely feasible off-the-shelf technology for automobiles and offers some advantages over gasoline as an energy source, such as lower costs and better safety, as well some disadvantages. But its hard to see how it could be successfully applied to aircraft; batteries are even worse when it comes to energy density.
 

J_P_C

Senior Airman
563
1,295
Feb 21, 2010
Warsaw
I did a study for Kennedy Space Center on the probability of failure of composite pressure vessels. I found that a high pressure (3600 PSI) Compressed Natural Gas tank capable of holding the same energy as 10 gal of gasoline weighs 100 lb, empty, and is about 3 ft long and 18 inches long; full of CNG, the tank weighs about 150 lb.

For a tank holding compressed hydrogen gas, the same figures apply to a tank capable of holding the energy equivalent of 2 gallons of gasoline.

CNG is an entirely feasible off-the-shelf technology for automobiles and offers some advantages over gasoline as an energy source, such as lower costs and better safety, as well some disadvantages. But its hard to see how it could be successfully applied to aircraft; batteries are even worse when it comes to energy density.
interesting - one of my colegues is working on H2 tank project right now - made of CFRP - your calcs were relatad to tank made of metallic materials? By the way - LNG cars are pretty popular here in Poland - this is fairly easy to handle technology.
 

MIflyer

1st Sergeant
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6,853
May 30, 2011
Cape Canaveral
No, the concern was for composite technology tanks, such as fiberglass or carbon fiber, not metal, although some use metal liners. KSC had a tank fail and then they began to wonder just how failure prone they are. Theoretically they last for thousands of years, but the question is "What is the reality?" As it turned out a the Defense Technical Info Service had a contractor try to do a study on the subject but the industry flat out refused to cooperate. So I had to do an intelligence gathering operation rather than just a study. And I found data that enabled you to estimate the probability of failure, much of it based on actual news reports associated with failures. When a tank blows up and takes off someone's foot, it is hard to cover up the incident. The big factor is ENVIRONMENTAL in nature. When someone spills sulfuric acid on the surface of a composite tank it may just look like a little discoloration but the end result may well be catastrophic. Aside from that, some tanks have a service life and you exceed that at your peril.

Probably the best approach is to use a titanium liner, overwrap it with carbon fiber composite, and then put a layer of fiberglass atop that. The fiberglass is not as strong as the carbon fiber but is much more forgiving to environmental conditions; it protects the carbon fiber.

And in terms of safety, the tanks are designed to automatically vent their contents if the temperature exceeds a certain value. When they vent, the fuel goes up rapidly and any fire tends to take place away from the vehicle, not pooling on the ground as liquid fuels do. There was one incident where someone screwed up installing a tape deck in CNG powered shuttle bus and it stared and electrical fire one night when the bus was in garage. The fire resulted in the CNG tank venting and the gas going up to the ceiling, where it was ignited by a sparking light. Only burn marks on the ceiling resulted, repairable by just some paint. If it had been gasoline or diesel powered buses in that garage the tape deck fire probably would have blown the whole building off the map.

And as for the "bomb" aspect of the pressure tanks, they are so robust that any vehicular mishap that ruptures the tank will prove to be fatal to the people involved anyway.
 

J_P_C

Senior Airman
563
1,295
Feb 21, 2010
Warsaw
No, the concern was for composite technology tanks, such as fiberglass or carbon fiber, not metal, although some use metal liners. KSC had a tank fail and then they began to wonder just how failure prone they are. Theoretically they last for thousands of years, but the question is "What is the reality?" As it turned out a the Defense Technical Info Service had a contractor try to do a study on the subject but the industry flat out refused to cooperate. So I had to do an intelligence gathering operation rather than just a study. And I found data that enabled you to estimate the probability of failure, much of it based on actual news reports associated with failures. When a tank blows up and takes off someone's foot, it is hard to cover up the incident. The big factor is ENVIRONMENTAL in nature. When someone spills sulfuric acid on the surface of a composite tank it may just look like a little discoloration but the end result may well be catastrophic. Aside from that, some tanks have a service life and you exceed that at your peril.

Probably the best approach is to use a titanium liner, overwrap it with carbon fiber composite, and then put a layer of fiberglass atop that. The fiberglass is not as strong as the carbon fiber but is much more forgiving to environmental conditions; it protects the carbon fiber.

And in terms of safety, the tanks are designed to automatically vent their contents if the temperature exceeds a certain value. When they vent, the fuel goes up rapidly and any fire tends to take place away from the vehicle, not pooling on the ground as liquid fuels do. There was one incident where someone screwed up installing a tape deck in CNG powered shuttle bus and it stared and electrical fire one night when the bus was in garage. The fire resulted in the CNG tank venting and the gas going up to the ceiling, where it was ignited by a sparking light. Only burn marks on the ceiling resulted, repairable by just some paint. If it had been gasoline or diesel powered buses in that garage the tape deck fire probably would have blown the whole building off the map.

And as for the "bomb" aspect of the pressure tanks, they are so robust that any vehicular mishap that ruptures the tank will prove to be fatal to the people involved anyway.
I think your analysis could be extremely interesting for the guys who are working on H2 tank project here - is it publicly available? any chance to take detailed look on it?
 

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