Ok, since 900kts, 8 passengers, 7200 nm for less then $99,000 might be stretching things, a little...

How about something achievable: Hydrogen Fuel Cell Electric Aircraft?

I've been looking at the Toyota Mirai FCEV. The current model is 180hp, and I think the weight and size of the fuel cell and controls are reasonable and could fly. The fuel tanks are lightweight composites as well. The range probably won't be that good for a variety of reasons. One of the new generation of aeromotive electric motors designed to drive a propeller would be the cherry on top.

I think it would work as a practical demonstration.

Some sort of simple airframe suitable to the rest of the demonstration...

Anyone feel like chipping in a kickstarter for it?

I’m in. I think this is the only sort of useable electric airplane we are going to see for a long time. Something like a Pipistrel Sinus would be a good airframe.

ZeroAvia

Groundbreaking airframes happen when there’s a new propulsion technology and someone builds an airplane around it. Of course, lots of duds happened the same way, when the propulsion tech did not meet expectations.

I don’t know enough about hydrogen fuel cells to know which direction this would go. But these kinds of experiments are the way aviation moves forward.

Fuel cells are a good possibility, but hydrogen is not a good fuel choice. Low density, high danger, expensive.

Its very difficult to store hydrogen for long periods of time.

I could just barely imagine a Hydrogen powered large airliner. The plane is big enough that large liquid hydrogen tanks are not crazy, and since it flies daily, fuel-boiloff is not a big problem.

It would have to look very different from a conventional airliner - the tanks would be very large - but the fuel weight very low - probably end up with very high altitude operation.

I don't know if fuel cells can reach the required power density, but hydrogen turbines or piston engines will work.

Other than storage, hydrogen is an excellent fuel: fantastic energy density, no deposits, doesn't burn too hot, if stored as cryogenic, provides a lot of engine cooling etc.

Of course this only makes sense when virtually all electric generation is non-carbon.

There are Mirai cars all over the place here in California, a good number of hydrogen fill stations. There's even one at Harris Ranch, enabling easy driving between the SF Bay area to the LA area where Toyota is also marketing the Mirai.

The storage tanks, fuel cell and controls are actually pretty reasonable in size and weight.

I'm aware of ZeroAvia, I think they are the ones that had a fuel-cell powered PA46 crash not long ago.

H2 is ~triple the energy density (MJ/kg) of dino distillates.

Raptor has a head start on you. Try and catch up!

there are folks working on this....some are hydrogen generators driving electric motors....and others are hydrogen powered engines.

https://www.ainonline.com/aviation-news ... port-crash

http://cafe.foundation/blog/going-big-a ... -hydrogen/

http://sustainableskies.org/wp-content/ ... x662-1.jpg

Unfortunately, storing it is a problem.

As a low pressure gas, it take ENROMOUS space, think Hindenburg.

As a high pressure gas, it takes very heavy cylinders to handle the high pressure.

As a liquid, it requires cryogenic handling and it boils off sitting around, so you only fuel just before use (like rockets). Any fuel left over evaporates before next flight. Also, the process of turning it into a liquid uses a LOT of energy.

95% of hydrogen produced today comes from fossil fuel, with a lot of CO2 released, so not exactly changing the basic problem.

Saying hydrogen is high energy density but ignoring the storing problems is like saying electric motors are high power density and ignoring the batteries. The whole system has to be considered.

Mike C.

Unfortunately, storing it is a problem.

As a low pressure gas, it take ENROMOUS space, think Hindenburg.

As a high pressure gas, it takes very heavy cylinders to handle the high pressure.

As a liquid, it requires cryogenic handling and it boils off sitting around, so you only fuel just before use (like rockets). Any fuel left over evaporates before next flight. Also, the process of turning it into a liquid uses a LOT of energy.

95% of hydrogen produced today comes from fossil fuel, with a lot of CO2 released, so not exactly changing the basic problem.

Saying hydrogen is high energy density but ignoring the storing problems is like saying electric motors are high power density and ignoring the batteries. The whole system has to be considered.

Mike C.

Interesting stuff with some very difficult - maybe “unsolvable” issues (for airplanes). There will be some alternate ideas but people keep trying to translate ground and water based technologies into airplanes. It is a heavy lift - pun intended! The act of lifting and maintaining an object in “thin” air takes a lot of extra energy and changes the math.

HP in a car is absolutely irrelevant in translating to planes - 180 HP is a max usable while average usage is 25% or less - say 45 HP. An airplane takes 70 to 80% of max HP so about a 3X fuel usage. People look at them as equivalent - not even close. Also, ability to carry extra weight - batteries, hp tanks, etc - is wide open for ground based vehicles - not so in planes.

Energy density per KG for H2 is also pretty irrelevant - even at 4X advantage per weight - the best you can do with liquid hydrogen is get to a 14X volume differential (at -423 degrees) vs gasoline - thus about a 4X penalty vs gasoline on a volume basis. Weight is important but volume density is the key for H2 - specific density of 0.07.

A couple of outher fun aspects - Liquid H2 is stored at - 423 degrees F and will reach 25,000 PSI in a closed system if constrained and warmed to ambient. Obviously, would be vented to atmosphere or hangar - so what could go wrong??? Finally, anyone who has worked with H2 knows that it is a bugger to keep where you want it - little bitty / slippery molecule at high pressure always looking to escape.

Hydrogen, battery, hybrid are all viable technologies in certain applications but we are a long way from the physics and math working out for airplanes. Readily available funding from a number of sources - government (you and I), higher ed (government again, you and I) and “guilty” corporations (higher prices, you and I) will keep these projects rolling.

Hydrogen has very high energy density per mass and very low energy density per volume. Its really annoying.

I think cryogenic storage is the only one that has any hope for aircraft use, but its still really high volume, and doesn't scale well to small tanks.

If you could fill the tanks just before engine start, then the boil off isn't a problme because it goes directly to running the engine - but then you would need to offload at the destination. Also need to keep the tanks cold.

Its just an awkward fuel to deal with - probably only really useful for upper stage rockets (beyond LEO)





H2 is ~triple the energy density (MJ/kg) of dino distillates.

Composite tanks in the Toyota Mirai....


https://www.compositesworld.com/news/to ... evelopment

402 mile range in the Mirai with 3 composite tanks. Seems do-able.