"Don French" wrote in message
om...
The law of inertia has nothing to do with this? It has everything to
do with it.

No, it doesn't. Inertia is a very tiny component of the overall physics
problem.

[...]
In this case, if you dropped anything at all out of that rocket at
Mach 9.5, it would contine to move at Mach 9.5 forever unless acted
upon.

There IS something acting upon it. Air resistance, which is VERY
significant at that speed, even with the relatively low air density.

The jet would never have to fire its engines and it would
maintain Mach 9.5 if it weren't for the effect of air friction, the
unbalanced force.

So you DO understand that there is air friction. Amazing.

In a vacuum, the thrust required to accelerate from
Mach 0.5 to 1.0 is exactly the same force required to accelerate from
Mach 9.5 to Mach 10.0.

We are not talking about a situation in a vacuum.

I see part of the problem.

No, you don't.

You, like many non-technical people, think
that inertia is only something to overcome.

What an odd statement. Inertia is simply inertia. It's not defined by what
one does to it.

Inertia is as much about
the difficulty in slowing something down as it speeding something up.

Is not speeding something up a matter of "overcoming inertia"?

For what it is worth, there isn't a lot of air at 100,000 feet. If I
am not mistaken, the density of air at 100,000 feet is 1/400 the air
density at 5000 feet.

I don't have the exact density numbers in front of me, but you are certainly
mistaken about your method of calculating the air density at that altitude,
as well as your assumption as to just how significant drag is at that speed
and altitude.

The frictionless scenario is the starting point for understanding the
problem.

Unfortunately, you don't seem to be able to get past that starting point.

Once you undersand that the plane would fly at the rocket's
speed without an engine if there were no air resistance, you can limit
the problem to analyzing the power it takes to overcome friction.

I already understand that, and have been trying to point out all along that
the issue is "the power it takes to overcome friction". How nice of you to
finally show up at this party.

[...] It makes
the achievement of the scramjet more impressive than I thought.
Thanks for educating me.

You are quite amusing. You spend the better part of a post insinuating that
I don't know my physics, and then bury a "mea culpa" in the middle,
admitting that all along you did not have your facts straight. That's rich.

Well, I wasn't trying to personalize my statement

Of course you were...you started out accusing me of never having taken high
school physics. It doesn't get much more personal than that.

and I don't think you really needed to either.

Needed to? No...probably not. Still, it seemed quite appropriate in
context (and still does).

My statement is in fact true. Less and
less people have a grasp of physics these days.

I don't dispute that claim. I think it's ironic coming from you though.

In point of fact, I
have a very old bachelor's degree in physical chemistry, which is not
physics per se, but I did study mechanics, if not fluid dynamics.

And so? Are you trying to say that you should have known better? I'm a bit
lost as to what your point in describing your studies is.

Pete