(no subject)

[inahandbasket]

brain fart that I need to let out...

So there's a lot of chatter lately about resurrecting/creating Jules Verne's old spaceship launching cannon - essentially a big gun on/in the ground that shoots objects into space.
(See this boingboing post for some more info and jump-off links.)

The major issue is one of friction and heat, namely any projectile moving through low atmosphere at enough speed to hit orbit would burn up well before it got there.

So here's a thought.
Let's use the big gun to launch a projectile, but instead of full velocity at exiting the muzzle you make the projectile a SCRAMjet. It'll leave the gun at well above Mach5, trigger the SCRAMjet engine, and roar vertically into orbit, accelerating the whole way. The momentum it's got should coast it through the upper atmosphere where the air's too thin for the SCRAMjet to function, perhaps needing a small booster for the last push to orbit.

Comments

[komos.livejournal.com]

Would you have the same heat issues if you were to use a railgun or some other electromagnetic setup rather than chemical explosives and mechanical pistons? Or do we just need frictionless surfaces?

[inahandbasket]

the issue's actually air friction. Escape velocity from earth's surface is roughly 7 miles per second, which is how fast the projectile would have to be moving when it left the barrel of the gun.
Dat's a lotta air friction. ^_^

[komos.livejournal.com]

I was thinking that might be the problem. Frictionless surfaces it is.

'Course, I'm still opting for a space elevator and solar sailers.