Re: helicopter not equal rocket

[Stefan Jeglinski <jeglin@4PI.COM>]

> That very nearly says that anything adhering to Newton's laws is a reaction
> engine.  IMHO that definition is too broad to be usable.  Under such a
> definition, sure, helicopters are reaction engines, but the point I was
> making about the physics remains:  machine guns don't exhibit translational
> lift.  Using a machine-gun model to explain induced drag is bad physics.


John,

I think I understand much better the points that you have made in
several threads, but I have a nagging concern that I hope can be
answered so I can close out my particular issue with this topic.
Sorry to nitpick.

Regardless of the precise mechanism regarding translational lift, for
example, it is not clear to me in the end whether you claim that the
idea of "air being thrown downward" is not the mechanism for lift. I
don't think so but I'm not sure (it's hard to weed through all the
responses and counter-responses).

Perhaps translational lift, for example, leads to more air being
thrown down, and this adds to the overall lift. Or are you saying
that there is a new mechanism at work that is wholly unrelated to air
being thrown downward? Alternatively, perhaps it is a pressure
argument. Regardless of the exact mechanism, could the concept of
translational lift lead to a resulting pressure differential that can
be cast as a force on the wing? Whether it actually does or not, or
whether the subject is even translational lift, is not important to
me as much as understanding whether you are introducing force
concepts that have nothing to to with pressure differentials or air
being thrown down.

To use an analogy from my field, solid state physics, I might take on
the discussion of conductivity by electrons, or conductivity by
holes, or conductivity by polarons. And I might say that the
properties of each are quite different and that the conductivity of
polarons absolutely cannot be explained by considering the electron
alone. But I would never say that the conductivities in all three
cases are not ultimately due to electrons.

Back to lift, I agree that the basic reaction engine (rocket) concept
could not possibly -explain- translational lift (or induced drag, to
cite another challenge), but if translational lift leads to more air
being thrown down for example, one might say that translational lift
leads to a greater "efficiency" of the reactive wing principle (that
is, the idea that lift is a reaction to the wing throwing air down,
regardless of the gory details).

OK? :-)


Stefan Jeglinski