starship-design: Yikes!

[wharton@physics.ucla.edu (Ken Wharton)]

>>dP/dM = c {n(1+2A)^0.5 -1}/A
>
>Is dP/dM equal to P/M ?

Yes - Since E cancels you can make it as small as you want.  And my P is
really delta P; the change in momentum of the ship.

>Mo=9.38Mf
>
>We both forgot the Logarithm! (did you lure me into that?)
>This really makes the mass-ratios dramatic for low efficiencies...
>(This also clarifies my doubts about the apparent low ratios.)

Yes, that's my mistake.  So now, for a 10% efficiency, you need a sail/ship\
ratio of 10^26!!  Yikes and a half.  Did someone say they could turn beamed
power into electricity at a 90% or better conversion?  So all we need is a
way to turn electricity into a perfect beam with a 60% efficiency.  Otherwise
we'll have to sign off on this idea...

Damn logarithm.

Ken