Re: Remember those jet backbacks?
>So I did some number-crunching.
And two backpack-cylinders made of
>such material, each cylinder 30 inches-long,
>6-inches in diameter, containing air at
10,000psi, would combined hold just over
>50Ibs of compressed-air. And, theoretically, all that compressed-air
>could generate an "average" of over 660Ibs[3,000N] of thrust for 600
>seconds, unlike the 30-40 seconds of thrust for that jet backpack
>invented in 1961.
Sorry, you crunched the number wrong.
Cold gas thrusters for compressed air have an Isp of around 70. 50 pounds of air would give you 3500 pound-seconds of thrust, or around 20 seconds of flight for a lightweight pilot.
John Carmack
www.armadilloaerospace.com