Why does the shuttle throttle on ascent?

On Wed, 10 Jan 2007 19:45:06 -0600, Henry Spencer wrote
(in article ):

(The other is also related to thinner air: rocket engines are more efficient

with less back pressure.

My undergraduate propulsion prof would be gagging at your use of the
term "back pressure" Henry. He used to almost spit and fume when
someone let it slip. :-p

--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

In article ,
Herb Schaltegger wrote:
(also related to thinner air: rocket engines are more efficient
with less back pressure.

My undergraduate propulsion prof would be gagging at your use of the
term "back pressure" Henry...

This is the difference between someone whose idea of an unsophisticated
audience is upper-year engineering students, and someone who's actually
had practice writing for, and talking to, non-captive audiences. :-)

Is "back pressure" strictly correct? Arguably not, although the issue is
more complicated than it looks (for one thing, ambient pressure at the
nozzle exit isn't necessarily the same as ambient pressure elsewhere on
the engine, which in turn isn't necessarily the same as ambient pressure
on the vehicle -- rocket exhausts can be powerful ejector pumps). But it
*is* what you say if you want to give the right general impression to an
audience that doesn't care to hear the rigorous details.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

"Henry Spencer" wrote in message
...
In article ,
Herb Schaltegger wrote:
(also related to thinner air: rocket engines are more efficient
with less back pressure.

My undergraduate propulsion prof would be gagging at your use of the
term "back pressure" Henry...

This is the difference between someone whose idea of an unsophisticated
audience is upper-year engineering students, and someone who's actually
had practice writing for, and talking to, non-captive audiences. :-)

Is "back pressure" strictly correct? Arguably not, although the issue is
more complicated than it looks (for one thing, ambient pressure at the
nozzle exit isn't necessarily the same as ambient pressure elsewhere on
the engine, which in turn isn't necessarily the same as ambient pressure
on the vehicle -- rocket exhausts can be powerful ejector pumps). But it
*is* what you say if you want to give the right general impression to an
audience that doesn't care to hear the rigorous details.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |


In a similar way that the term "centrifugal force" is generally despised by
experts, but for most people it's quite a good way to describe the
sensations they experience.

On Thu, 11 Jan 2007 21:37:33 -0600, Henry Spencer wrote
(in article ):

In article ,
Herb Schaltegger wrote:
(also related to thinner air: rocket engines are more efficient
with less back pressure.

My undergraduate propulsion prof would be gagging at your use of the
term "back pressure" Henry...

This is the difference between someone whose idea of an unsophisticated
audience is upper-year engineering students, and someone who's actually
had practice writing for, and talking to, non-captive audiences. :-)

Is "back pressure" strictly correct? Arguably not, although the issue is
more complicated than it looks (for one thing, ambient pressure at the
nozzle exit isn't necessarily the same as ambient pressure elsewhere on
the engine, which in turn isn't necessarily the same as ambient pressure
on the vehicle -- rocket exhausts can be powerful ejector pumps). But it
*is* what you say if you want to give the right general impression to an
audience that doesn't care to hear the rigorous details.


I know what you're saying Henry. It's just that every time I hear
"back pressure" in terms of rocket or gas turbing engines, I still to
this day have the mental image of Prof. Wilkerson standing at the
blackboard, closing his eyes as if in pain and squeezing his hand so
hard the chalk snaps . . . ;-)

--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

"Herb Schaltegger" wrote in
message .com...

I know what you're saying Henry. It's just that every time I hear
"back pressure" in terms of rocket or gas turbing engines, I still to
this day have the mental image of Prof. Wilkerson standing at the
blackboard, closing his eyes as if in pain and squeezing his hand so
hard the chalk snaps . . . ;-)

He only snapped chalk? You're lucky.

I had a Latin teacher that would throw it... very quickly... at the
blackboard behind your head.

THAT got your attention.



--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

"Greg D. Moore (Strider)" wrote in message
news:TeMph.13533
"Herb Schaltegger" wrote in

I know what you're saying Henry. It's just that every time I hear
"back pressure" in terms of rocket or gas turbing engines, I still to
this day have the mental image of Prof. Wilkerson standing at the
blackboard, closing his eyes as if in pain and squeezing his hand so
hard the chalk snaps . . . ;-)

He only snapped chalk? You're lucky.

I had a Latin teacher that would throw it... very quickly... at the
blackboard behind your head.

Why would your Latin get upset when you mentioned "back pressure"? g

"Steve Foley" wrote in message
news:8mMph.7617$GL.3332@trndny06...
"Greg D. Moore (Strider)" wrote in
message news:TeMph.13533
"Herb Schaltegger" wrote in

I know what you're saying Henry. It's just that every time I hear
"back pressure" in terms of rocket or gas turbing engines, I still to
this day have the mental image of Prof. Wilkerson standing at the
blackboard, closing his eyes as if in pain and squeezing his hand so
hard the chalk snaps . . . ;-)

He only snapped chalk? You're lucky.

I had a Latin teacher that would throw it... very quickly... at the
blackboard behind your head.

Why would your Latin get upset when you mentioned "back pressure"? g

Because we were conjugating it properly. Geesh :-)

Greg D. Moore (Strider) wrote:

He only snapped chalk? You're lucky.

I had a Latin teacher that would throw it... very quickly... at the
blackboard behind your head.

THAT got your attention.



The nuns were fond of throwing erasers _at_ your head, and some of them
were made partially of wood.

Pat

On Fri, 12 Jan 2007 22:12:42 -0600, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:



Greg D. Moore (Strider) wrote:

He only snapped chalk? You're lucky.

I had a Latin teacher that would throw it... very quickly... at the
blackboard behind your head.

THAT got your attention.



The nuns were fond of throwing erasers _at_ your head, and some of them
were made partially of wood.

Was your head one of those? It would explain much.