Re: starship-design: Drag

[KellySt@aol.com]

In a message dated 10/1/97 4:28:27 AM, TLG.van.der.Linden@tip.nl wrote:

>Kelly you wrote:
>
>>I'm not sure, but I think we gave up on using interstellar media for drag?
>> Probably their just isn't enough of it to be worth using.  Anyone
remember?
>
>You may determine it yourself:
>
>A     = effective scoop surface (m^2)
>v     = ship's velocity (m/s)
>rho   = density of space (kg/m^3)
>Mship = Ship's mass including scooping system (kg)
>Mdot  = Total scooped mass per second (kg/s)
>
>Mdot = A*v*rho
>
>Resulting deceleration = 2*Mdot*v/Mship            (F*t=p=m*v and F=M*a)
>
>
>Note that the deceleration is only valid for the velocity that you use. The
>deceleration will likely decrease when you loose speed, unless your scoop
>starts working better at lower speeds.
>This may actually happen, since for lower ship speeds the to-be-scooped
>particles have more time to reach the scoop mouth and thus may be scooped
>from further away.
>
>If you find a small deceleration for the initially high velocities, then
>that most likely means that you won't slow down in time. The only thing you
>may then try is increasing the effective scoop area. You might you should
>remember that it will take a long time to slow down to velocities that might
>have a better deceleration.
>
>
>Timothy
>
>P.S. Would you mind mailing me the density of the interstellar medium once
>again?


Who me?  Last guess I had was in the paper in LIT about RAm Scoops.  Even
then G.E.S. and I were pretty sure we were just guess at the interstellar
densities.  Estimates range from A hydrogen atome per every couple cubic
centimeters, to Thousands of times that weight in carbon molecules.

Kelly