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#220
by
rsp1202
on 03 Jan, 2006 19:58
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#221
by
Rocket Guy
on 03 Jan, 2006 20:28
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Actually, the SSMEs put out almost the same flame...you just cannot see it due to the SRBs light drowning it out. Take a Delta 4 launch with SRBs and you don't see thje RS-68 flaime either.
Take a look at side-angle Shuttle photos and you can see the long flame from the main engines; top one here:
http://www.launchphotography.com/STS114launch.html
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#222
by
FransonUK
on 03 Jan, 2006 20:35
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Very nice picture, and one of yours Ben?
Don't let me near a camera, I always take shots with people's eyes apparently becoming red!
So what's coming out of the SRBs? Apparently it's a secret mix? I know it's been described as like rubber eraser filings in a cement mix type formula when poured into the segments?
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#223
by
nacnud
on 03 Jan, 2006 23:48
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OK heres a question.
Is there a good overview of how the orbiter copes with thermal issues anywhere?
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#224
by
Rocket Guy
on 04 Jan, 2006 03:18
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Nah, its on spaceflight.nasa.gov in the Shuttle reference section. It's basically Aluminum powder as the fuel, ammonia perchlorate as the oxidizer, and a polymer glue holding it together.
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#225
by
Jonesy STS
on 05 Jan, 2006 09:34
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Ben - 3/1/2006 10:18 PM
Nah, its on spaceflight.nasa.gov in the Shuttle reference section. It's basically Aluminum powder as the fuel, ammonia perchlorate as the oxidizer, and a polymer glue holding it together.
Just what every growing boy needs....
Why is it that when the SRBs light up, they don't shoot off and rip themselves free of the rest of the stack?
Only two points where they are linked with the ET, are they made of someone amazingly strong?
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#226
by
SimonShuttle
on 05 Jan, 2006 10:11
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The whole thing is less stress because the SSMEs are firing at 104 per cent, but yeah I'm sure the attach points are made of strong stuff. They have to explode the bolts to seperate, for instance.
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#227
by
Jonesy STS
on 05 Jan, 2006 13:24
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Ok, still an imbalance of about 5.5 million lbs of thrust pounding up the side of you, taking the million pounds you've got from the SSMEs. Really can't work out why the SRB attach points don't rip out of the side of the ET or SRB when the SRBs are fired.
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#228
by
Mark Max Q
on 08 Jan, 2006 18:30
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Jonesy STS - 5/1/2006 8:24 AM
Ok, still an imbalance of about 5.5 million lbs of thrust pounding up the side of you, taking the million pounds you've got from the SSMEs. Really can't work out why the SRB attach points don't rip out of the side of the ET or SRB when the SRBs are fired.
Good question.
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#229
by
psloss
on 08 Jan, 2006 18:43
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Mark Max Q - 8/1/2006 2:30 PM
Jonesy STS - 5/1/2006 8:24 AM
Ok, still an imbalance of about 5.5 million lbs of thrust pounding up the side of you, taking the million pounds you've got from the SSMEs. Really can't work out why the SRB attach points don't rip out of the side of the ET or SRB when the SRBs are fired.
Good question.
Google is your friend -- at least for now. Here's a good answer (I think):
http://groups.google.com/group/sci.space.shuttle/msg/fdcd9837c09b784d?hl=en&
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#230
by
Orbiter Obvious
on 09 Jan, 2006 00:47
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Does the launch pad have heat resistant tiles on it I think I've seen some on the two mini towers that holds the bdy of the aft in place before launch.
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#231
by
Super George
on 09 Jan, 2006 03:05
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Yes, I've seen this. They are viewable on the MLPs even without a Shuttle on board. I've not see any TPS tiles though, will have to look through videos.
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#232
by
Hotol
on 09 Jan, 2006 06:48
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Yes, there's a line of TPS on both of the pillars that old on to the aft of the orbiter on the pad.
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#233
by
Rocket Guy
on 09 Jan, 2006 17:14
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The 'pillars' are not holding the aft. The are just umbilical towers and provide access to areas around the aft in the event of inspections or repairs. The last two umbilicals are attached here, just below the OMS pods. You can see them pull away in the view of the SSMEs at T-0.
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#234
by
Jamie Young
on 11 Jan, 2006 00:08
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Moving on from that, when the stack rolls forward and back, do these umbilicals flex with the stack? Or are they pipes that have some slack?
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#235
by
possum
on 12 Jan, 2006 00:23
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The thrust imbalance between the SRB's, ET and Shuttle is carried by the ET forward thrust beam. It runs through the ET from SRB to SRB. The attach points are very strong, made of Inconel I believe, as are a lot of high stress parts. Not really that hard to believe if you think about 2.75 million lbs. shear on each side it would take a 3.5 inch diameter shaft made of material capable of 150,000 psi in shear to take that load.
The two "mini-towers" on the MLP are called Tail Service Masts (TSM) and they are the LOX and LH2 umbilicals that fuel the vehicle prior to lift-off. The LOX and LH2 go into the Orbiter aft propulsion piping and into the ET and is drained back through the same piping to the engines during launch. The TSM's are attached while in the VAB and they are designed to remain attached to the Oribiter with significant movement, not just during rollout but also during main engine buildup prior to SRB ignition. The TSM's must remain attached until the SSME's are at full thrust and the SRB's iginite (they actually separate "in flight") because if the SSME's shut down before reaching full thrust, you have to be able to drain the ET and safe the vehicle.
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#236
by
Jamie Young
on 12 Jan, 2006 00:42
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rmathews3 - 11/1/2006 7:23 PM
The two "mini-towers" on the MLP are called Tail Service Masts (TSM) and they are the LOX and LH2 umbilicals that fuel the vehicle prior to lift-off. The LOX and LH2 go into the Orbiter aft propulsion piping and into the ET and is drained back through the same piping to the engines during launch. The TSM's are attached while in the VAB and they are designed to remain attached to the Oribiter with significant movement, not just during rollout but also during main engine buildup prior to SRB ignition. The TSM's must remain attached until the SSME's are at full thrust and the SRB's iginite (they actually separate "in flight") because if the SSME's shut down before reaching full thrust, you have to be able to drain the ET and safe the vehicle.
Thanks, that explains why they are on the MLP, so they can keep the Shuttle steady from the point of mating to launch. Seems obvious now, but sometimes you need someone to tell you!
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#237
by
Orbiter Obvious
on 12 Jan, 2006 01:54
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rmathews3 - 11/1/2006 7:23 PM
The two "mini-towers" on the MLP are called Tail Service Masts (TSM)
Great, I'll add that to Chris' list for new people.
STS = Space Transportation System
ET = External Tank
OV = Orbiter Vehicle (such as OV-103 is Discovery, 04 is Atlantis, O5 is Endeavour)
SRB = Solid Rocket Booster
OMS = Orbital Maneuvering System
RCS = Reaction Control System
MPL = Mobile Launch Platform (Rides on the Crawler Transporter, Shuttle Stack goes on top of the MLP).
VAB = Vehicle Assembly Building
MECO = Main Engine Cut Off
SSME = Space Shuttle Main Engine
MAF = Michoud Assembly Facility
MSFC = Marshall Space Flight Center
KSC = Kennedy Space Center
RLV = Reusable Launch Vehicle
LOX = Liquid Oxygen
LH2 = Liquid Hyrogen
ECO = Engine Cut Out (sensor)
TSM = Tail Service Masts
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#238
by
possum
on 12 Jan, 2006 11:27
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Jamie Young - 11/1/2006 7:42 PM
Thanks, that explains why they are on the MLP, so they can keep the Shuttle steady from the point of mating to launch. Seems obvious now, but sometimes you need someone to tell you!
The TSM's don't really keep the Shuttle steady, if fact, you don't want them to impart any loads into the Shuttle structure. The Shuttle stack is supported entirely from the base of the SRB's, with the Shuttle cantilevered off the side of the ET. The TSM attachment "floats" with the Shuttle as is sways back and forth. In fact, when the SSME's are building thrust prior to SRB ignition, the Shuttle stack is flexed forward and when it rocks back to vertical, the SRB's are fired. The TSM's must stay attached to the Shuttle during this "twang" of rocking back and forth. If you look at the video of the STS-105 launch on page 5 of the FTP video collection, you can see the aft end of the Shuttle lift up more than a foot when the engines ignite, this translates into 30 inches of movement at the tip of the ET. If you look real close, you can see the TSM umbilical plate attached to the Shuttle right next to the OMS pod and when the stack rocks back and the SRB's ignite, the umbilical plate disappears into the TSM in the blink of an eye.
By the way, those "sparklers" you see during SSME ignition are called Radially Outward Firing Initiators (ROFI's) and they are there to ignite any unburned hydrogen coming out of the SSME's during startup, otherwise hydrogen gas could build up in pockets of dead air in the aft area and explode.
The TSM's are attached to the Shuttle to provide services, the main service being LOX and LH2 fill and drain. There are also many electrical and fluid services going through the umbilical plate. The mating plate is about 3 feet wide by 4 feet tall and it has numerous quick disconnects (QD's) for fluids and electrical services. Many things go through this interface including all of the software commanding up until T-31 seconds when control of the countdown is handed off to the Shuttle. If the launch team wants to stop the countdown, the commands go through this interface. That is another reason why these umbilicals are attached until the SRB's are ignited and there's no stopping the launch. All the critical interfaces between the ground and the flight vehicle go through the TSM's. And since there are 2 TSM's, there are redundant services going through each TSM so that if one inadvertently disconnects prematurely, you still have the critical commanding capability through the other one.
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#239
by
psloss
on 12 Jan, 2006 11:53
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Regarding the tail service masts, there are good OTV engineering cameras on the MLP "deck" that usually focus on the T-0 umbilicals that run from them into the orbiter; as you note the twang effect is very noticeable there.
I believe the hydrogen burn igniters start at T-10 seconds and stop at T-0 (don't know if that's at depletion or not); what's interesting about that is the last cutoff on the pad (STS-68) was initiated so close to T-0 (at -1.9 sec.), that the igniters stopped before the shutdown sequence was completed.
There have also been a few cases where a hold was called after the igniters started but before the engine start commands were sent (STS-93 being one example; another would be the first STS-26 FRF attempt).
