Hacker News Reader

Comment by unpolloloco | Hacker News Reader

It's not a stupid fuel in cases where you need massive amounts of energy and can't spare the weight... Like rockets and... rockets

View on HN

Not even rockets. Lose too much from the low density leading to a larger structure and isolation required to handle it as a liquid, and not freeze the oxygen. Meaning worse performance than the pure numbers would imply. Not to mention cost of handling it.

Case in point, SpaceX going larger rocket with less efficient kerosene first and now methane to increase efficiency and reduce soot, while still keeping everything simpler than hydrogen.

Yes, I concede it's a good engineering solution there. Especially when you also need water!

If you’re burning hydrogen to power a rocket, you don’t get to keep the exhaust. If, on the other hand, you use hydrogen and oxygen to power a fuel cell, keep the water, and use the power output to power an ion thruster or similar device, I suspect you end up with worse overall results than simply using a rocket and carrying some water.

Apollo used fuel cells to good effect. Their constraints lined up perfectly - they already needed oxygen tanks, and a supply of water, and they didn't have li-ion batteries back then either. Also, the weight cost of the fuel cells themselves amortizes nicely when you need power for an entire week - and hydrogen is light. And once it had been used, the water was flushed, saving further weight. The big downside to batteries is they weigh the same empty and full.

More importantly, aircraft.

Maybe airplanes and boats?

Reply on news.ycombinator.com