Ares I thrust vector control?

Is this the right group for the Constellation project, btw?

Probably not been reading the right information, but one
question I have been wondering for some time is:
How do you aqquire thrust vector contol -steering simply - of the upcoming
Ares rocket using a modified solid rocket booster, when there is no
gimbal of the nozzle, like there is e.g. on the SSME and most other LPRE?
Not actually seen this mentioned, but I'm sure some engineers did think of
it :-)

Bjørn Sørheim

On Nov 29, 6:03 pm, "Bjørn Sørheim"
wrote:
Is this the right group for the Constellation project, btw?

Probably not been reading the right information, but one
question I have been wondering for some time is:
How do you aqquire thrust vector contol -steering simply - of the upcoming
Ares rocket using a modified solid rocket booster, when there is no
gimbal of the nozzle, like there is e.g. on the SSME and most other LPRE?
Not actually seen this mentioned, but I'm sure some engineers did think of
it :-)

Bjørn Sørheim

The shuttle boosters and Ares first stage have gimbaling nozzles. The
shuttle boosters provide most of the control until they are jettisoned
and then the SSME's take over

http://spaceflight1.nasa.gov/shuttle...rb/thrust.html

Never really did understand solid thrust control. Certainly you have no real
control over how the fuel burns inside as far as I can see, save the shaping
of the solid fuel inside, so thrust vectoring just with nozzles must be a
bit rough and ready, its certainly not a smooth ride.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
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wrote in message
...
On Nov 29, 6:03 pm, "Bjørn Sørheim"
wrote:
Is this the right group for the Constellation project, btw?

Probably not been reading the right information, but one
question I have been wondering for some time is:
How do you aqquire thrust vector contol -steering simply - of the upcoming
Ares rocket using a modified solid rocket booster, when there is no
gimbal of the nozzle, like there is e.g. on the SSME and most other LPRE?
Not actually seen this mentioned, but I'm sure some engineers did think of
it :-)

Bjørn Sørheim

The shuttle boosters and Ares first stage have gimbaling nozzles. The
shuttle boosters provide most of the control until they are jettisoned
and then the SSME's take over

http://spaceflight1.nasa.gov/shuttle...rb/thrust.html

"Brian Gaff" wrote in message
.uk...
Never really did understand solid thrust control. Certainly you have no
real control over how the fuel burns inside as far as I can see, save the
shaping of the solid fuel inside, so thrust vectoring just with nozzles
must be a bit rough and ready, its certainly not a smooth ride.

You can't control the level of thrust in most solids. But the large ones
like you find on Titan III/IV and the shuttle have thrust vector control
systems. I believe some of the ones in Titan used liquid injection in the
nozzle (which is why you see a tank on the side of the SRB).

The shuttle SRB's actually gimbal the nozzle (much like a liquid fuel
engine). You can imagine the engineering challenges involved in creating a
nozzle joint that actually holds together.

I'm not sure how Ariane-5's boosters do thrust vector control.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

"Jeff Findley" wrote in message
...
You can't control the level of thrust in most solids.

I meant to say you can't *actively* control the level of thrust in most
solids. The thrust versus time profile is determined by the shape of the
grain of the propellant.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

On Nov 30, 10:48 am, "Brian Gaff" wrote:
Never really did understand solid thrust control. Certainly you have no real
control over how the fuel burns inside as far as I can see, save the shaping
of the solid fuel inside, so thrust vectoring just with nozzles must be a
bit rough and ready, its certainly not a smooth ride.

Not really. "Thrust vectoring" is just pointing the thrust vector.
By gimbaling the nozzle, it just changes the direction of the thrust.
Much like a water nozzle with a swivel. The magnitude of the thrust
is unchanged.

skrev i melding
...
On Nov 30, 10:48 am, "Brian Gaff" wrote:
Never really did understand solid thrust control. Certainly you have no
real
control over how the fuel burns inside as far as I can see, save the
shaping
of the solid fuel inside, so thrust vectoring just with nozzles must be
a
bit rough and ready, its certainly not a smooth ride.

Not really. "Thrust vectoring" is just pointing the thrust vector.
By gimbaling the nozzle, it just changes the direction of the thrust.
Much like a water nozzle with a swivel. The magnitude of the thrust
is unchanged.

Why was thrust vector control included in the first place on the SRBs for
the shuttle system?
There are separation motors to remove them when they have burnt out, and the
SSMEs supply the thrust vector control for the shuttle/tank/SRBs.
It seems to me this is just adding unnecessary complexity to the system.

Bjørn Sørheim

"Bjørn Sørheim" wrote in message
...
Why was thrust vector control included in the first place on the SRBs for
the shuttle system?
There are separation motors to remove them when they have burnt out, and
the
SSMEs supply the thrust vector control for the shuttle/tank/SRBs.
It seems to me this is just adding unnecessary complexity to the system.

Actually, I don't believe that the SSME's have enough thrust and gimbaling
in order to steer the stack when the SRB's are firing. The Titan III/IV
SRB's also had thrust vectoring.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

On Nov 30, 3:06 pm, "Jeff Findley"
wrote:
"Bjørn Sørheim" wrote in message

...

Why was thrust vector control included in the first place on the SRBs for
the shuttle system?
There are separation motors to remove them when they have burnt out, and
the
SSMEs supply the thrust vector control for the shuttle/tank/SRBs.
It seems to me this is just adding unnecessary complexity to the system.

Actually, I don't believe that the SSME's have enough thrust and gimbaling
in order to steer the stack when the SRB's are firing. The Titan III/IV
SRB's also had thrust vectoring.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

Just a clarification. The Titan III/IV 1st stage core engines were
not firing during the SRM burns. Hence the term "Stage 0" for the
SRM's. The SRM's had to have TVC.


But you are correct in that the SSME's do not have enough control
authority for the whole stack

wrote:



But you are correct in that the SSME's do not have enough control
authority for the whole stack

I suspect you're wrong for the three engine "nominal" case, the SSME's
probably do have enough control authority. The pitching moment on the
Shuttle is large, and currently handled by the SRBs, but I suspect it is
still within the gimbal range of the SSMEs. You would actually have to run
the numbers to make this statement. Nominally, Roll would be the biggest
problem, and in particular the SAR, not as much roll rate acceleration.

Of course, when engines start to fail, then control authority would be a
problem and would be a design consideration. Aborts were probably the
determining factor.

--
Craig Fink
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