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