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#1340
by
MechTech
on 05 Oct, 2008 00:29
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Speaking of loaded tanks. Is the pad cleared of personnel during tanking? It seams to me that there is extra danger during the tanking process. Then after tanking I assume only people needed to load the crew into the orbiter would be needed. I have seen the video of the disaster of the large Russian booster.
Danny
Yes, pad is cleared for ET tanking ops. The only ones at the pad after tanking is the OCC, FIT and FLT CRW.
Red Crew "might" be also called to the pad, but only if a problem comes about
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#1341
by
Ronsmytheiii
on 05 Oct, 2008 00:39
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This may not be the perfect fit for Shuttle Q&A, but why was Chandra launched on the shuttle rather than a Titan IV? Titan was built to IUS payloads, and after Challenger i thought that those type of missions (flying just to deploy a upperstage/satellite combo) were frowned upon?
The only thing I could think of was that Chandra had a larger volume than a DSP satellite, however I dont know.
There were many reasons, one was that the USAF only bought one T-IV for NASA
Not having a ride would be important, but still chandra seems so have been an unneccessary risk to a flight crew and instead should have on on an ELV in one form.
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#1342
by
rdale
on 05 Oct, 2008 01:50
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Why was Chandra a risk?
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#1343
by
Ronsmytheiii
on 05 Oct, 2008 05:00
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Why was Chandra a risk?
not that is was a risk more than any other shuttle flight, but the fact that the crew were tasked to do a mission which should be much more effective and cheaper on an ELV
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#1344
by
rdale
on 05 Oct, 2008 12:14
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That's not the only IUS that flew after Challenger though...
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#1345
by
psloss
on 05 Oct, 2008 12:26
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That's not the only IUS that flew after Challenger though...
No, but I don't think Titan 4 was "available" for, say, Magellan/Galileo/Ulysses. Or TDRS-C and D.
Jim can correct/elaborate, but it sounds like cost was a primary reason. (Not just buying the launcher, but setting aside some/all of the integration work with Shuttle might have been a factor.)
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#1346
by
Analyst
on 05 Oct, 2008 14:11
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A Titan 4 was not cheap. For NASA, using STS was maybe cheaper. Keep in mind the variable costs of a Shuttle launch are quite low. In the late 1990ies the Shuttle flight rate was quite low, the fixed costs there anyway.
Analyst
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#1347
by
C5C6
on 05 Oct, 2008 17:04
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hi, just wondered...doesn't the SRBs have a maximum operating time, and after period they have to be de-stacked?? could this affect STS-125??
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#1348
by
Webhamster
on 07 Oct, 2008 02:46
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I have a question about STS-400 that I haven't found an answer for...
Since the Hubble orbit is so high, IF STS-400 was needed, would Atlantis lower it's orbit prior to the rendezvous or would STS-400 go all the way up to Hubble range to get them?
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#1349
by
ChrisGebhardt
on 07 Oct, 2008 03:52
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hi, just wondered...doesn't the SRBs have a maximum operating time, and after period they have to be de-stacked?? could this affect STS-125??
Each SRB segment has a shelf-life of, last I heard or read, 5.5 years. However, I have not heard or read that this is even under discussion for the STS-125 delay. Also, remember that this was a discussion during the whole STS-117 hail incident. Furthermore, a static test firing of an SRB was conducted at the Utah testing grounds that involved SRB segments passed the 5.5 year shelf-life. From what I read, there were no adverse affects or anomalies noted during that test firing.
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#1350
by
ChrisGebhardt
on 07 Oct, 2008 03:54
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I have a question about STS-400 that I haven't found an answer for...
Since the Hubble orbit is so high, IF STS-400 was needed, would Atlantis lower it's orbit prior to the rendezvous or would STS-400 go all the way up to Hubble range to get them?
No. The STS-400 (or 401 mission depending on the orbiter) rescue vehicle would rendezvous with Atlantis in the 360nautical mile orbit Atlantis was launched to. Atlantis would not lower her orbit for the rescue mission rendezvous.
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#1351
by
Mike_1179
on 07 Oct, 2008 17:51
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I have a question about STS-400 that I haven't found an answer for...
Since the Hubble orbit is so high, IF STS-400 was needed, would Atlantis lower it's orbit prior to the rendezvous or would STS-400 go all the way up to Hubble range to get them?
No. The STS-400 (or 401 mission depending on the orbiter) rescue vehicle would rendezvous with Atlantis in the 360nautical mile orbit Atlantis was launched to. Atlantis would not lower her orbit for the rescue mission rendezvous.
Also remember, the LON will have an empty payload bay. There's no heavy stuff going uphill so there is extra APM to make it to the 360 nm orbit.
Also, if you remember your orbital mechanics (who could forget) it's quicker to rendenvous with an object that is in a higher orbit. LON will launch when the plane of STS-125's orbit is in line with KSC, regardless of where STS-125 is in that orbit. STS-125 could be right on top of KSC or could be on the either side of the Earth, but you have to launch near that in-plane time to have enough fuel to get to them.
So now you've launched into the same plane, but how do you catch them. The answer is with orbital height. The higher an orbit is, the higher its energy but the slower its relative velocity. If LON launches in-plane but is at the same orbital height, she'll never catch STS-125, they will be going the same speed around the Earth.
To catch her, LON will be in a lower (faster) orbit. With LON going faster around the Earth, she'll eventually catch-up to STS-125 and then can raise her orbit and dock. So to get a larger difference in speed, you want to have a larger difference in orbital heights. If STS-125 were too low, then LON would have to be in an orbit so low that it would be affected by atmospheric drag. If the orbits are too close in height, then the game of catch-up takes too long.
One more thing, there's more risk of MMOD in lower orbits, so higher is also a bit safer.
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#1352
by
shuttlefan
on 07 Oct, 2008 18:06
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It was mentioned earlier in this thread that STS-82 in 1997 was the highest altitude the shuttle ever went to. Do the main engines fire longer to get it that high or do the OMS engines fire more often?
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#1353
by
Webhamster
on 07 Oct, 2008 18:19
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I have a question about STS-400 that I haven't found an answer for...
Since the Hubble orbit is so high, IF STS-400 was needed, would Atlantis lower it's orbit prior to the rendezvous or would STS-400 go all the way up to Hubble range to get them?
No. The STS-400 (or 401 mission depending on the orbiter) rescue vehicle would rendezvous with Atlantis in the 360nautical mile orbit Atlantis was launched to. Atlantis would not lower her orbit for the rescue mission rendezvous.
Also remember, the LON will have an empty payload bay. There's no heavy stuff going uphill so there is extra APM to make it to the 360 nm orbit.
Also, if you remember your orbital mechanics (who could forget) it's quicker to rendenvous with an object that is in a higher orbit. LON will launch when the plane of STS-125's orbit is in line with KSC, regardless of where STS-125 is in that orbit. STS-125 could be right on top of KSC or could be on the either side of the Earth, but you have to launch near that in-plane time to have enough fuel to get to them.
So now you've launched into the same plane, but how do you catch them. The answer is with orbital height. The higher an orbit is, the higher its energy but the slower its relative velocity. If LON launches in-plane but is at the same orbital height, she'll never catch STS-125, they will be going the same speed around the Earth.
To catch her, LON will be in a lower (faster) orbit. With LON going faster around the Earth, she'll eventually catch-up to STS-125 and then can raise her orbit and dock. So to get a larger difference in speed, you want to have a larger difference in orbital heights. If STS-125 were too low, then LON would have to be in an orbit so low that it would be affected by atmospheric drag. If the orbits are too close in height, then the game of catch-up takes too long.
One more thing, there's more risk of MMOD in lower orbits, so higher is also a bit safer.
Good stuff, thanks. I remembered hearing that Hubble was pretty much the limit for shuttle ops and a documentary (When We Left Earth?) about STS-31 being at about half-fuel by the time they got there which is why I asked. Especially if they burn more fuel to get into position for the crew transfer. I temporarily forgot about the lack of payload which
would save fuel.
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#1354
by
mark147
on 07 Oct, 2008 19:23
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One more thing, there's more risk of MMOD in lower orbits, so higher is also a bit safer.
You sure about that?
I thought for STS-125, they planned to lower one side of the orbit as soon as they've released hubble to reduce MMOD risk while they do the late inspections. That would suggest that there's a lower MMOD in a lower orbit than Hubble's orbit.
Unless it's that being in an elliptical orbit helps for some reason?
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#1355
by
Jorge
on 07 Oct, 2008 19:33
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It was mentioned earlier in this thread that STS-82 in 1997 was the highest altitude the shuttle ever went to. Do the main engines fire longer to get it that high or do the OMS engines fire more often?
Also answered earlier in this thread.
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#1356
by
Jorge
on 07 Oct, 2008 19:35
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One more thing, there's more risk of MMOD in lower orbits, so higher is also a bit safer.
You sure about that?
I thought for STS-125, they planned to lower one side of the orbit as soon as they've released hubble to reduce MMOD risk while they do the late inspections. That would suggest that there's a lower MMOD in a lower orbit than Hubble's orbit.
You are correct. MMOD risk is worse in higher orbits, because there's not enough drag to make the debris decay.
If LON is declared prior to the orbit adjust (OA), the rescue will be performed at HST's altitude (300 nmi). If LON is declared after the OA, the rescue will need to be performed in the elliptical post-OA orbit. Which will do a number on launch windows and rendezvous targeting, but it can be done.
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#1357
by
STS Tony
on 10 Oct, 2008 21:20
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During Challenger's Abort ATO, the footage records the loop mentioning a good fuel dump. How do they dump fuel? Is there a valve in the ET to allow for this?
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#1358
by
psloss
on 10 Oct, 2008 21:27
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#1359
by
NavySpaceFan
on 11 Oct, 2008 00:03
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Question about the ACTS/TOS satellite launched by DISCOVERY's crew during STS-51. Reading all the information available, it sounds like the ACTS tested technology that was later used by companies like DirectTV and Dish Network for small, home-based ground stations. Is this an accurate statement?
