Space/Science — HabitableZone

Space/Science » in reply to The Rutan tourist vehicles are NOT space launchers

Difficulty of space travel
dtb — (archived)

About ten years ago I had a summer internship at the RAND Corporation, and had an office just down the hall from Mert Davies, the father of planetary mapping. I hate to say, I had no idea back then who he was.

Anyway, I recall one day I found waiting on the laser printer a draft essay Mert had printed, from another RAND guy I think, making the point that as a rule of thumb the difficulty and thus expense of aerospace vehicles went up with the kinetic energy involved. Meaning that Earth orbit, at 30+ times the speed of a 747, is about 1,000 times as "difficult". The guy made the point that as you got faster and faster, your vehicle had to handle vastly different flight modes, plus the rocket equation meant you had less and less mass to deal with all those requirements, etc. Bottom line being that it was nuts to use subsonic commercial air travel as a model of space launch.

Heck, even the Concorde was much, much more expensive and fragile than a C-130 Hercules carrying the same passenger load at 1/4th the speed. That wasn't due to design flaws in the Concorde. With our current propulsion technology at least you can build a 300mph plane with hugely excess structural strength and lots of redundancy. If you want to haul that load at Mach 2.2, you end up with a fragile system that can fail catastrophically just from hitting a small piece of debris on a runway (a piece that would *not* have caused an accident with a subsonic jetliner).

Likewise, Spaceship Two won't have anywhere near the flight rate or safety margin of a Learjet. And as Nick points out, the leap from Spaceship Two to orbit is huge -- it's closer to the Lear than the Shuttle.

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