Why does the shuttle throttle on ascent?

The shuttle actually throttles back twice during ascent. The first time
is at max Q. This is not a 3 G situation for the vehicle. After the
solids are dropped, the shuttle again throttles back in the last 30
seconds or so before main engine cut-off, so as to not exceed 3 G's of
forward acceleration when the fuel is almost gone. Whether this is due
to a structural or other reason, I'm not sure. But structural makes the
most sense for several reasons, weight being the primary one.

Bud


Jim wrote:
Thanks Danny, I had a good belly laugh from that one.
Jim
wrote in message
ps.com...

Danny Deger wrote:
Why does the shuttle throttle to 3 Gs on ascent?

Danny Deger

Because structurally the shuttle vehicle is only stressed for 3 g's. If
they didn't throttle back in the late stages of the ascent when the
fuel is almost gone and the vehicle is light, it would exceed this
level of acceleration. Since the engines are liquid fueled, they can
hold full thrust until the fuel is gone.

Bud

wrote in message
oups.com...
The shuttle actually throttles back twice during ascent. The first time
is at max Q. This is not a 3 G situation for the vehicle. After the
solids are dropped, the shuttle again throttles back in the last 30
seconds or so before main engine cut-off, so as to not exceed 3 G's of
forward acceleration when the fuel is almost gone. Whether this is due
to a structural or other reason, I'm not sure. But structural makes the
most sense for several reasons, weight being the primary one.

Bud

The answer is:
So Navy fighter pilots can fly the shuttle :-)

Danny Deger

snip

Danny Deger wrote:
wrote in message
oups.com...
The shuttle actually throttles back twice during ascent. The first time
is at max Q. This is not a 3 G situation for the vehicle. After the
solids are dropped, the shuttle again throttles back in the last 30
seconds or so before main engine cut-off, so as to not exceed 3 G's of
forward acceleration when the fuel is almost gone. Whether this is due
to a structural or other reason, I'm not sure. But structural makes the
most sense for several reasons, weight being the primary one.

Bud

The answer is:
So Navy fighter pilots can fly the shuttle :-)

Danny Deger

snip

I read that. Nice double meaning. However I think Navy pilots get to 9
G's like AF Raptor pilots do. I was just explaining to the ones that
thought the max Q issue was 3 G's, which it is not.

Bud


Danny Deger wrote:
wrote in message
oups.com...
The shuttle actually throttles back twice during ascent. The first time
is at max Q. This is not a 3 G situation for the vehicle. After the
solids are dropped, the shuttle again throttles back in the last 30
seconds or so before main engine cut-off, so as to not exceed 3 G's of
forward acceleration when the fuel is almost gone. Whether this is due
to a structural or other reason, I'm not sure. But structural makes the
most sense for several reasons, weight being the primary one.

Bud

The answer is:
So Navy fighter pilots can fly the shuttle :-)

Danny Deger

snip

wrote in message
ups.com...
I read that. Nice double meaning. However I think Navy pilots get to 9
G's like AF Raptor pilots do. I was just explaining to the ones that
thought the max Q issue was 3 G's, which it is not.


This is true. Two different times to throttle on ascent for 2 different
reasons.

Danny Deger