Hydrogen-powered jet planes?

Question

Background information:

1. Space shuttle's main engines (not the boosters) are hydrogen-powered.

2. There are (experimental) hydrogen-powered cars which actually burn hydrogen instead of gasoline (I'm not talking fuel cells, but hydrogen-based combustion engines!).

Considering that, would it be possible to have jet planes using hydrogen instead of kerosene? Would the re-design costs for the engines be prohibitively high? Would keeping the hydrogen liquid be too expensive at the airports and maybe impossible in the plane tanks? Would it be too dangerous, because of hydrogen's high inflammability?

If not, why is no-one working on that? Why is there development on cleaner cars, but not airplanes?

Answer 1

The main problem of hydrogen is bulk, and second, its cryogenic nature -- it need to be chilled to -252 C (-423 F) to be in liquid form.
First, the bulk issue. Liquid hydrogen takes about 4 times the volume of hydrocarbon fuel for the same amount of energy. Since long range airplane have fuel filling all of the wing, replacing jet fuel by hydrogen would mean filling the fulelage as well, leaving no room for the passenger or cargo, unless you are willing to have a much enlarged fuselage, or external tanks. But enlarged fuselage or external tanks would create more drag, so would need more powerfuel engines using more fuel. Hydrogen cars are easier to achieve because a car range is in the order of 300 to 400 km. Long range airplane can go 16000 km (about 9000 miles); and they need proportionally much more fuel than cars; up to half their maximum take off weight can be fuel.
Then you have the issue of the cold. A rocket can get by because it will remain in the atmosphere just a few minutes before reaching orbit -- and even then, the insulation of the external tank of the space shuttle has proven problematic as we all know. But a long range airplane can be in the air for 14 hours or more, sometime flying in the rain and snow, imagine how much ice from condensation it would accumulate in the period. So thick insulation would be needed, adding even more to the bulk.
Companies ARE studying hydrogen fueled airplanes, but until a good solution to the above mentioned problems is found, they will remain purely in the research stage.

Answer 2

There are a number of challenges - some of which are highlighted by yourself in your question. However if there's a good idea that's not being applied you can be sure that the reason comes down to economics - and bingo! that's the reason here. The production of hydrogen is still much more expensive than the production of aviation-gas (a petroleum product). I believe in motor cars your cost per kilometer (or mile) goes up by a factor of about 8 if you have a hydrogen engine. I assume it would be similar for aeroplanes, but that's just a guess. But, you also have to ask yourself why you want hydrogen rather than fossil fuel. I'm guessing your answer is "because it doesn't pollute". Right? Well, no. You see you need to produce the Hydrogen first. Hydrogen is "made" by spliting water into Hydrogen and Oxygen. This is done using a lot of electricity. The production of electricity often comes at the cost of its own pollution. Oil, gas and coal fired power stations are bad for the evironment. Nuclear is very contentious but is definitely not pollution free. So, in summary, Hydrogen is ACTUALLY not a pollution free energy source AND it's still very expensive.

Answer 3

Hydrogen should be viewed as an energy storage system rather than a fuel. It does not occur naturally, it has to be made either by stripping the carbon out of methane or electrolyizing water. That consumes energy. It then has to be compressed into either a cryogenic liquid or a metal hydride, still under pressure, this liberates large amounts of energy as heat which cannot be used for propulsion.

I have never yet heard a compelling case for hydrogen, it is being pursued because of rhetoric rather than sensible engineering.

So yes, producing and storing it is a huge issue.

Yes, burning hydrogen is very easy, no problem what so ever. That's not the issue.

If I was betting the planet I'd be investing a hell of a lot more in fusion research, without a cheap and plentiful source of energy we are heading for horses and bicycles... unless climate change kills us first.

Answer 4

The earliest German jets did use hydrogen. It didn't prove very good. Safety is a major concern -- remember the Hindenberg. Storage requires too much weight for efficient use on an aircraft. The tanks are just too heavy.

Another issue with hydrogen is that the atoms are so small that they can actually pass through the walls of any storage container, even solid steel. The process is slow, but does lead to significant losses over time.

Lastly, although hydrogen is very efficient as a fuel, the cost of producing it is excessive. Unless electricity is available for well below a penny per KWh, it's cost is too high.

Answer 5

Lets just wait until we get the car down right now. Once they perfected the combustion engine for Hydrogen, they`ll most likely move on to boats, trains, and airplane. Truly I don`t want to be travel back to America with an engine that doesn`t have all the glitches worked out yet.

Answer 6

Actually I e-mailed Boeing about this and got this response: This is both feasible and would be done via a subsidiary of Boeing Corp. This was I suspect in reaction to any lawsuits from production of untested technology. However I think that this is the future of energy as other technologies bring Hydrogen to a more practical medium.

Answer 7

Probably the cost of extensive testing, but why fix what ain't broke.