Re: Rocket action

[brian whatcott <inet@INTELLISYS.NET>]

At 19:28 12/1/99 -0600, you wrote:
> I remember, but don't know from where, hearing that a rocket can go no
> faster forward than the exhaust gases leave the exhaust nozzle.  Is this
> correct?  If so, can someone explain the whys and wherefores to a simple
> high school teacher like me.  Thanks in advance.
>
> Greg Kifer
> Olathe North High School
> Olathe, KS  66061


A propellor driven plane needs to accelerate the mass flowing through its
blades to provide thrust. If the air was initially stationary to a ground
observer, it will be moved backwards. From the plane's perspective,
the efflux is moving backwards at a higher velocity than the plane is
moving forwards.

 A rocket provides its own gas, and any rear directed acceleration of mass
 in a vacuum provides a thrust force.

So it seems to me that the propellor model is closer to Greg's description
 than a rocket model.


brian whatcott <inet@intellisys.net>
Altus OK