|
Author
|
Topic: Shuttle SRB gimballing: How is it done?
|
Atlantis
Member Posts: 111
From: Cullman, AL
Registered: Dec 2007
|
posted 11-01-2011 08:46 PM
   
At my university, we're working on a balloon-launched rocket project and part of that involves figuring out how to steer a solid fuel rocket. How do the gimbals on the shuttle srbs work and does anyone know of any technical drawings that may be useful? |
Cozmosis22
Member Posts: 968
From: Texas * Earth
Registered: Apr 2011
|
posted 11-03-2011 03:25 PM
Am not aware of any gimbal effect with the solid rocket nozzles? Think the SRBs were light up and GO! |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-03-2011 04:06 PM
The SRB's use a hydraulic system similar to the orbiter's. There is a flex joint between the nozzle and motor casing. Not an easy task for amateurs. Look at fluid injection, vanes or jetavator. |
Atlantis
Member Posts: 111
From: Cullman, AL
Registered: Dec 2007
|
posted 11-03-2011 08:42 PM
quote:
Originally posted by Jim Behling:
Look at fluid injection, vanes or jetavator.
That's what I said to the guy that's over the project.
|
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
|
posted 11-04-2011 04:09 PM
There are two hydraulic power units (HPUs) and two hydrazine powered APUs located in the SRBs to control the nozzle gimbling through a pair of servo actuators. Each unit primarily drives one actuator, but a single HPU can drive both (albeit at a slower rate). The mechanism is located in the aft skirt region of the SRB. They can control yaw, pitch and tilt relative to what the rate gyros indicate and do a pretty good job. In 136 flights (if you count the Ares 1-X launch) those systems have never failed to my knowledge. Of course, systems like these were first developed for solid fueled ICBMs, such as the Minuteman series (and the Polaris and Trident missles used by the Navy).The vane system is what the Germans did for the V-2 and the Redstone booster, which had control vanes placed in the path of the rocket exhaust to steer it (the nozzle didn't move). |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-04-2011 04:51 PM
The APU on the SRB's is called an HPU. There are not two of each on the booster. Minuteman series first used nozzles that moved on only one axis. Polaris used jetavators. Hydraulic power was provided by solid propellant gas generators. Both used fluid injection for upper stages. |
Atlantis
Member Posts: 111
From: Cullman, AL
Registered: Dec 2007
|
posted 11-05-2011 12:02 AM
Thanks for the info, guys! |
Ben
Member Posts: 1896
From: Cape Canaveral, FL
Registered: May 2000
|
posted 11-05-2011 12:10 PM
quote:
Originally posted by Cozmosis22:
Am not aware of any gimbal effect with the solid rocket nozzles? Think the SRBs were light up and GO!
Nearly all of the shuttle's steering during the fist two minutes of flight are the SRB nozzles' gimbaling. |
Cozmosis22
Member Posts: 968
From: Texas * Earth
Registered: Apr 2011
|
posted 11-05-2011 12:15 PM
Thanks! Hmmm, sure isn't noticeable to the naked eye. The pre-ignition main engines gimbal check was always a beautiful sight to see. |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-05-2011 11:19 PM
quote:
Originally posted by Cozmosis22:
The pre-ignition main engines gimbal check was always a beautiful sight to see.
The SRB's do the same thing after T-25 seconds.
|
music_space
Member Posts: 1179
From: Canada
Registered: Jul 2001
|
posted 11-06-2011 08:27 PM
quote:
Originally posted by Jim Behling:
The SRB's do the same thing after T-25 seconds.
Then, how come we never got to see this on the engineering video recordings? Wasn't this an important procedure to record? |
Cozmosis22
Member Posts: 968
From: Texas * Earth
Registered: Apr 2011
|
posted 11-06-2011 09:05 PM
quote:
Originally posted by music_space:
Then, how come we never got to see this on the engineering video recordings?
I am guessing that the nozzles were hidden by the aft skirts of the SRBs and they didn't want to put a camera kit down underneath the launch platform?On this personal photo of the business end of an expended shuttle solid I put a red arrow where the gimballing occurs?  |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
|
posted 11-09-2011 03:35 AM
quote:
Originally posted by Jim Behling:
The APU on the SRB's is called an HPU. There are not two of each on the booster.
My reference comes from the space shuttle news reference press guide first issued in the late 1970s (I got it at Space Camp in 1985 as part of my camp pack). The information pretty much matches up word for word with what is found on this web page.Is it possible the design was simplified to a single unit over time (as a weight saving measure perhaps)? |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-09-2011 10:47 AM
From your link: There are two self- contained, independent HPUs on each SRB. Each HPU consists of an auxiliary power unit, fuel supply module, hydraulic pump, hydraulic reservoir and hydraulic fluid manifold assembly. Your words: There are two hydraulic power units (HPUs) and two hydrazine powered APUs Which would mean 4 APUs per booster. |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-09-2011 11:14 AM
quote:
Originally posted by music_space:
Then, how come we never got to see this on the engineering video recordings? Wasn't this an important procedure to record?
No, neither was SSME gimbaling. There just happened to be video of SSME gimbaling because it was there to look at other events.There is sufficient telemetry to monitor both gimbaling events. |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
|
posted 11-09-2011 11:15 AM
quote:
Originally posted by Cozmosis22:
On this personal photo of the business end of an expended shuttle solid I put a red arrow where the gimballing occurs?
The joint is actually submerged in the motor. |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
|
posted 11-09-2011 12:48 PM
Ahhh, so the APU is PART of the HPU. That makes sense.Funny enough, my google search turned up some band on Youtube called SRB and they have a song called "Hydraulic Power Unit". Search for it if you dare as it is an "acquired" taste (and the vibe of the group will not exactly appeal to everyone). |
advertisement