SomeDEGuy t1_j82locf wrote

New models from 80s, with an upgrade a decade ago.

We have a limited number of planes that can do flybys at extremely high altitude.

Plus, if we did have a secret plane that could do it, we'd not want to reveal that and just use a u2, sinces it's flight performance is fairly well known.


SomeDEGuy t1_iy8l90q wrote

Noise shouldn't be a huge difference, as its still burning material to force an object through air at speed.

Hydrogen is more energy dense per pound, but has some storage issues that would have to be figured out for safety. Storing a compressed gas like hydrogen is significantly more dangerous than the same mass of jet fuel. It's a good test, though, and helpful to explore new methods.