Chris:
I''ve no idea what Breedlove is doing.
My impression is that he is really pretty much outside the lsr "mainstream"
(like Noble & Green?). He's a Californian, so perhaps somebody else on the
list has info.
Perhaps we will have to disagree about the relative difficulty of the
technical problems-- but allow me to try?
If you are familiar with the equations-- assume any practical frontal area
and an achievable Cd, then calculate how much thrust is required to reach
750 mph. If you are using pure thrust (i.e., a jet or a rocket) that's
pretty much all there is to it-- buy a jet with that must thrust, and
work-out the aero to keep it on the ground-- before and after the shock-wave
hits.
If you are talking about wheel-driven, you must think of the (same) thrust
as coming from the drive tires, and provide an engine and drivetrain that
will deliver that thrust at top speed. And you also have to do the aero to
keep this version on the ground, just like the "thrust" version. But there
is a further complication: you need to provide enough traction to actually
deliver all that thrust to the salt (or dirt, or whatever); otherwise, all
you do is waste your power. I can find no evidence that the CoF at
Bonneville EVER gets any higher than about 0.75, so the downward force
(weight and aero) on the drive tires becomes a limiting factor. I think
that the wheel-driven vehicles that have already been driven over about
350mph have probably carried many times the (tire) design downforce on their
drive tires. The chance of disaster is probably as high for every run that
Tom Burkland makes as it was for Andy Green going transonic.
Surely you understand that "the sound barrier" is a myth. That was proven
in-- what-- 1949--? Sure, it's a little more complicated with a ground
vehicle, because you will have a sudden change in the downforce vector. But
Noble's team didn't really do anything very sophisticated to deal with that,
now did they? They just calculated the "up"-force from the shockwave, and
adjusted their aerodynamics to offset it. (If the wheel-drivens ever get to
that speed, the shock-wave will present an even bigger problem-- loss of
traction/ wheelspin tendancy. The ultimate traction control--?)
Again, not meaning to put-down what Noble and Green accomplished-- it was
incredible. Their deed stands as a monument to the abilities (and courage)
of those involved, and to mankind, in general. I am very proud of them.
Just trying to demonstrate why I personally am more interested in
wheel-driven.
Russ, #1226B
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