[minor_nitwit]

Ok, these guys claim to have invented a great engine, really just the pre-cooler. Why are they trying to build a plane instead of licensing it to others? That seems to be several orders of magnitude more difficult and increases the likelihood of failure.

[imaginenore]

Do you know any Mach 5 planes?

[jschwartzi]

Does he know of anyone in the tightly-regulated airline industry who would be crazy enough to build a completely new airframe and engine around a currently-experimental precooler?

[foobarian]

And using LH2 and LOX as fuel? With 3g acceleration? :-)

[aragot]

At that speed, I wonder what accidents will look like. I respect this technology as totally serious but in case of accident the NTSB may just delegate the investigation to a Darwin prize:

Is the plane sensitive to slight variations, like a few people walking in the alley? Since at Mach 5 we can expect a 5000K temperature for the dislocated parts [1], will the pieces completely burn and disintegrate before falling back to Mach 1, effectively acting as a MH370 at each accident, by design? Can we at least have a video of that on 9gag? Or will we have to search a 5,000-km radius if we have a 20minutes uncertainty for the accident window?

[1] http://en.m.wikipedia.org/wiki/Atmospheric_entry#Shock_layer...

[marcosdumay]

With LH2 and LOx as fuel-oxidizer, whatever are the consequences of speed, they'll be over a completely pulverized ex-airplane, not over entire parts.

Also, with that to speed, I wonder how big a runway this thing would need. It would probably operate on a completely separated airport, faw away from cities.

[madaxe_again]

Sure. The X-51. http://en.wikipedia.org/wiki/Boeing_X-51

[imaginenore]

You might as well have linked to an ICBM page.

X-51 is unmanned, and hasn't flown at mach 5 for longer than 4 minutes.

[madaxe_again]

It is however a winged craft with an air breathing engine, commonly known as "a plane".