[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: The actual running Archie paper...




John V Jackson wrote:

> Rockets push against their propellant which is initially travelling at their
> speed.  Jets push against the air which is travelling backwards relative to
> them.  In order to gain some forward impulse a jet has to push the air
> backwards in an absolute sense; a rocket can enjoy a forward impulse even
> though the exhaust gases might theoretically be moving in the same direction
> as the vehicle.

John, no offense - but this isn't how rockets and jets work.  Both work by
ejecting a mass rearward at a significant velocity.  Neither push against
anything behind them, or against their own propellant, and in fact both will
work more effectively if they are exhausting into a vacuum.  I designed and used
a jet thrust exhaust augmentation system for a prop driven plane we flew in the
Denver-Oshkosh cross-country air race two years ago, and could send you some of
the math if you wish.  And also some references by others in regard to the same
subject, and pointing out the same fallacy, which is quite commonly made.

But we are drifting away from dinosaurs, so probably should continue this
off-list.
Jim