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**David Kazdan**

Stubby:

Right, that was my point...

David

Stubby wrote:
Note. Slugs are a mass measurement whereas pounds are a force. There
is not a simple ratio because it depends on how strong gravity is. Of
course the shuttle has accelerations that are quite different than we
encounter on the face of the Earth!

There was a famous story of gold shippers that moved quantities of gold
from San Francisco to Anchorage in the 1800s. Of course they carefully
measured the gold before and after, presumably using a spring scale
rather than a balance. The bankers concluded a little bit of gold was
being lost from every shipment. After a lot of finger-pointing, they
identified the difference in gravity as the source of the difference.

Dudley Henriques wrote:
Bear with me David. I've been away from this stuff for a long while :-))

Rho for SSL is 0.002378 slugs/cu ft. Mass in slugs is the weight in
lbs/32.2
For high performance flight test dealing with uncompressible airflow;
for density (slugs ft3) for mass airflow (slugs/sec)

"David Kazdan" wrote in message
t...
Dudley:

Isn't dynamic pressure expressed in pressure units, pounds per
square inch (or SI, Pascals: newtons/sq. meter)? Mass density, which
you mention later, is in slugs/cu.in or cu.ft (or SI, Kg/cu.meter).

Thanks for all your good posts, I've learned a lot from them over
the years.

David

Dudley Henriques wrote:
"Danny Deger" wrote in message
...
Why does the shuttle throttle to 3 Gs on ascent?

Danny Deger
As the shuttle ascends, the dynamic pressure (in slugs/sq.in)
increases as the square of the velocity. The shuttle is throttled
back to 65% thrust to avoid over stress at a speed computed under
what is called critical q.
As the shuttle ascends, it is ascending into lower air density
(which of course transfers into a lowering dynamic pressure). The
throttling back takes the shuttle through a transition area during
the ascent that ends as the lowering air density meets the
parameters that allow throttle up. This I believe occurs at about 35
to 37K.
The point where lowering air density meets the ability to throttle
up again is the max q for the shuttle. (Max q meaning maximum
dynamic pressure)
After reaching max q, the shuttle is go for throttle up as the
increasing velocity past max q will never exceed the structural
limitations of the shuttle due to it's entrance into lower air
density that doesn't have the ability to overstress the structure.
Hope this helps a bit.
Dudley Henriques