Re: rocket motion

[brian whatcott <inet@INTELLISYS.NET>]

I'm sure I must be misunderstanding Barlow's rocket model.
Barlow draws a limited conclusion concerning
a model of rocket propulsion of a rather unusual kind
i.e with continually increasing thrust) - the conclusion
being that in this case the rocket accelerates.
(His last sentence, starting, "Apparently...")

To which I respond...."and a rocket with constant
or diminishing thrust also accelerates!"

I would appreciate a further clarification of
 Barlow's position.

Brian

At 10:24 12/16/99 EST5EDT, you wrote:
> Gang:
>
> Do you like solving already solved problems?  Sometimes
> they are fun.  I made two assumptions about rocket
> motion;  (a) the rocket throws out mass linearly; and (b)
> the relative velocity of the rocket with respect to the
> exhaust is constant.   If we let v be the relative velocity
> of the rocket with respect to the exhaust,  m be the
> initial mass of the rocket and fuel, and a be the rate at
> which the mass of rocket and fuel decreases; then we can
> calculate the distance the rocket has moved with reference
> to some origin in outer space with respect to a time
> parameter.
>
> My result is:
>
>        x(t) = (mv/a){(1 - at/m)ln(1 - at/m) + at/m}
>
> Apparently, its speed continues to increase as long as the
> rocket motors will continue throwing out the mass so that
> the relative velocity is constant and the decrease of the
> mass of the rocket-fuel part of the system is linear. WBN
> Barlow Newbolt
> Department of Physics and Engineering
> Washington and Lee University
> Lexington, VA 24450
>
> Young man if I could remember the names of all of
> these particles I would have become a botanist
>                        Enrico Fermi
> Telephone and Phone Mail:  540-463-8881
> Fax: 540-463-8884
> e-mail: NewboltW@madison.acad.wlu.edu
brian whatcott <inet@intellisys.net>
Altus OK