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#1380
by
neilh
on 22 Oct, 2010 18:33
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(wasn't sure if this should go in Q&A or be a separate thread)
This is more of a historical shuttle Q, but when/why was the decision made to go with hydrogen for the Space Shuttle instead of kerosene? Would it have made any sense to use the F-1 engines instead of developing the SSMEs? Would the F-1's have been able to survive being next to the SRBs?
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#1381
by
ugordan
on 22 Oct, 2010 18:47
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I'd think the F-1 would better fit the SRB role than SSME, i.e. a configuration mirroring that of Buran. As it stands, a really high Isp engine was needed in order to have 1.5 stage to orbit so SSME was kind of a no-brainer.
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#1382
by
Jorge
on 22 Oct, 2010 18:48
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(wasn't sure if this should go in Q&A or be a separate thread)
This is more of a historical shuttle Q, but when/why was the decision made to go with hydrogen for the Space Shuttle instead of kerosene?
Performance. Kerosene is better for first stages due to density and T/W, but for the rest of the climb to orbit hydrogen is more efficient.
Would it have made any sense to use the F-1 engines instead of developing the SSMEs?
No. It might have made sense to use the F-1 engines instead of the SRBs, though.
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#1383
by
neilh
on 22 Oct, 2010 19:05
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(wasn't sure if this should go in Q&A or be a separate thread)
This is more of a historical shuttle Q, but when/why was the decision made to go with hydrogen for the Space Shuttle instead of kerosene?
Performance. Kerosene is better for first stages due to density and T/W, but for the rest of the climb to orbit hydrogen is more efficient.
Would it have made any sense to use the F-1 engines instead of developing the SSMEs?
No. It might have made sense to use the F-1 engines instead of the SRBs, though.
Gotcha, thanks! My mind was totally drawing a blank and forgot that after the SRBs and hydrogen SSMEs, there aren't any other stages.
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#1384
by
sfxtd
on 22 Oct, 2010 20:33
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Perhaps loudness is measured in the far field, then an "equivalent loudness at a notional 1M" is calcuated as 180dB?
That is the process, even for normal audio applications.
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#1385
by
MP99
on 23 Oct, 2010 14:12
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Thanks.
Cheers, Martin
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#1386
by
dbscars2
on 27 Oct, 2010 15:53
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Going to my first launch for STS-133, but am curious how much wind speed it takes for them to cancel a launch? 13 hours in a car is bad enough, but to have it cancelled when I get there due to wind would be worse!
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#1387
by
brahmanknight
on 27 Oct, 2010 17:43
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Is there a particular reason why the Spacehab modules were flat on the top rather than being rounded like Spacelab?
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#1388
by
Jim
on 27 Oct, 2010 21:19
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Is there a particular reason why the Spacehab modules were flat on the top rather than being rounded like Spacelab?
To allow for an EVA path in case the doors don't close. Also to allow viewing of the payloads behind the module.
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#1389
by
Ford Mustang
on 29 Oct, 2010 08:22
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Can anyone enlighten me to the issue just before STS-117 launched around the T-35 second mark?
On the net, you can hear something about "ET Helium Inject Delta P #2 .. (pao talking) .. We are go"
Was this the ET pressurization issue that was noted a few days after launch?
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#1390
by
GoForTLI
on 29 Oct, 2010 09:29
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Can anyone enlighten me to the issue just before STS-117 launched around the T-35 second mark?
On the net, you can hear something about "ET Helium Inject Delta P #2 .. (pao talking) .. We are go"
Was this the ET pressurization issue that was noted a few days after launch?
There's discussion
here on L2. Does that help?
I recall loving Norm Knight's reaction and response on the Ascent Flight Control Team Video Replay.
ETA: The issue that was discussed just outside of AUTO SEQUENCE START was an ET Helium Inject delta-P #2 issue (was not a LCC violation).
From the SSP MER Problem Summary for STS-117, at approximately 3 minutes 30 seconds after launch, there was a LH2 pressure transducer that went off-scale high instantly on the SSME in the #3 position.
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#1391
by
Ford Mustang
on 29 Oct, 2010 10:22
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Thanks for that, TLI. Answered my questions. Was going through my old footage and heard that, it cropped up my curiosity.
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#1392
by
GoForTLI
on 29 Oct, 2010 11:21
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Before the recent STS-133 OV-103 ROMS XFEED flange issue, I wasn't familiar with the term AHC. In what applications are AHCs (Air Half-Couplings) typically used on the vehicles? How do they differ from other types of connectors?
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#1393
by
GoForTLI
on 30 Oct, 2010 04:26
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Before the recent STS-133 OV-103 ROMS XFEED flange issue, I wasn't familiar with the term AHC. In what applications are AHCs (Air Half-Couplings) typically used on the vehicles? How do they differ from other types of connectors?
Just watched the STS-133 Pre-Countdown Status Briefing with NTD Jeff Spaulding, and from his context I take it that "Air Half" just refers to the portion of the connection that is on the vehicle, as opposed to the GSE. I guess that makes sense.
(Maybe it should be called a Space Half-Coupling?
)
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#1394
by
dave k
on 30 Oct, 2010 13:40
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#1395
by
robertross
on 30 Oct, 2010 15:43
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Here I go, posting a question in the shuttle Q&A thread...
anik just posted in the ISS thread that there will be no re-boost of the ISS from Discovery because of the DAM performed earlier in the week.
Q: Does this allow Discovery to gain a few more seconds in the launch window as it won't need as much reserve propellant from the OMS engines? Or is all that factored in ahead of time and they would only use whatever mass margin was left in the mission to aid in re-boost?
Obviously the amount of launch window gained is minimal in the grand scheme of things.
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#1396
by
steveS
on 30 Oct, 2010 23:56
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Due to STS-133 launch shift from Nov.1 to Nov. 3, the launch had been brought forward by about 1 hour. Does it mean a reduce mission time? or due to orbital mechanics, the landing will be 1 hour more than planned (mission duration does not reduce/increase regardless of the liftoff time change)?.
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#1397
by
craigcocca
on 31 Oct, 2010 06:01
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In Chris' recent article about the history of space shuttle Discovery, I was reminded that she launched six times in 12 months in 1984 and 1985. Similarly, Atlantis launched on her two opening missions back to back in October and November 1985. Clearly times were different back then, as NASA was attempting to ramp up the launch rate and politics were driving the push to launch a single orbiter as frequently as mentioned above.
So my question for those of you who were around back then: how much different was an Orbiter processing flow back then versus now? Ignoring the obvious answer about the mountains of paperwork that now have to be done that weren't an issue in '85, can someone speak to the pace, pressure, stress level, etc that were present during the processing flows back then? How much maintenance was being deferred to future flows, as opposed to the present-day behavior of trying to launch the vehicle in "pristine" condition every time?
As an example, Atlantis landed on 51-J at EAFB on 10/7/85, and was flown back to KSC on 10/11/85. The vehicle was in the OPF from 10/11/85 to 11/8/1985 (28 days), before being rolled over for mating, and then was hard down at the pad four days later. Two weeks later, the vehicle was launched. Seems like barely enough time to pull out the SSMEs, install three new ones, and launch...
--Craig
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#1398
by
Jim
on 31 Oct, 2010 11:12
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there were two full shifts and a partial third shift with large amounts of overtime. the mountains of paper were the same back then and well as flying them in a "pristine" condition. Just had more people and money.
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#1399
by
psloss
on 31 Oct, 2010 12:46
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Seems like barely enough time to pull out the SSMEs, install three new ones, and launch...
Didn't always do that; different spares/logistics situation back then. The engines came out in that case, but after the post-firing inspections, maintenance, and retesting, they went back in the same orbiter and flew on that ship's next flight. (Same thing for some other orbiters and engine sets at the time.)
