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#2940
by
alk3997
on 15 Aug, 2013 13:10
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The shuttle was suborbital at the time of ET sep for the specific reason of ET disposal.
I understand that...so would this have been a longer main engine burn (was there enough prop for that) or OMS?
Now you are getting more into flight design. Assuming we're talking about a superlightweight tank, that was about 57,500 lbs dry mass. That was close to the limit for a due east (28.45 inclination) low orbit payload mass, after all of the performance enhancements. But, I'm not sure that matters (see below). We just didn't fly many due east missions after all of the performance enhancements.
So, it probably would have required a reduced cabin stowage and no OMS assist burn (since the payload bay was empty and save the prop for OMS-2) and probably other things I'm not thinking about off the top of my head.
What may have been a problem was that the payload bay was empty during launch. That would have violated a number of rules for minimum payload amounts. cg was one and I believe we would have broken some max dynamic pressure rules. Could those have been solved by tweaking the flight profile? I don't know - you would have to have designed some ascent profiles to see.
At the same time, the MECO targets should have been easy to hit but the OMS-2 targets would have been the difficult ones. How much penalty would there have been during an OMS-2 burn with having an extra 57,500 pounds attached in a below the cg position?
So, based on payload weight limits you probably could have taken the tank to orbit. But, how the flight would have been designed would have been an interesting challenge. There was only so much prop in the ET, so a greater SSME burn time during nominal (you still have to protect for RTLS) would not have been an option and also would not have helped OMS-2 but other flight design items would have been tweaked if it were do-able and only then would you know the answer to your question.
BTW, a few of our simulators allowed you to land with the ET attached since it was just a mass model (not a physical model). Kind of amusing the first time you tried it.
Andy
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#2941
by
DMeader
on 15 Aug, 2013 22:44
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Thanks very much....that's all very interesting and touches on things I was wondering about.
I was also thinking about the CG issues this would entail. Could the Shuttle even maneuver properly in orbit with the ET attached?
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#2942
by
alk3997
on 16 Aug, 2013 02:03
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Maneuvering would not have been a problem (I don't think). We maneuvered the Station stack without any problems (with some DAP changes). Station has far more mass.
OMS burn loss would have been interesting. Also how much payload would have had to be added just to move the cg and fix the other constraints. Combine the ET + added payload + orbiter for the mass at OMS-2. Don't know the answer there.
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#2943
by
Overflow
on 24 Aug, 2013 23:37
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Now here's a personal one for you, Jim. How do you know so much about the Shuttle off the top of your head?
http://forum.nasaspaceflight.com/index.php?topic=24176.0
(That is one place to start, but there are others.)
This is so cool!! Thank you SO much for posting this! (And thank you Jim for taking them of course)
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#2944
by
baldusi
on 25 Aug, 2013 01:42
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This is sort of an historical question. I understand that the concept while developing the STS was to be the definitive LEO transport. But I think that LEO stations was an integral part of the program. Since space stations require a Crew Evacuation Vehicle, was Shuttle specified from the beginnings to 30 days in space or was that the fall out of the limited development budget? Once they set that limit, did they assumed that the rate of launch was such that they could have always at least one shuttle or was the CEV a necessary development from the beginnings?
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#2945
by
Fequalsma
on 25 Aug, 2013 19:06
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Anyone know the depth of the two ET umbilical wells on the orbiter?
See the diagram in my Reply #2828 on: 01/31/2013 03:04 AM on page 189.
F=ma
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#2946
by
mogso
on 31 Aug, 2013 12:26
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QUESTION: somebody has drawings of a seat of the commander of the Shuttle. (The front, behind, below views, etc.) Thanks
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#2947
by
ZachS09
on 04 Sep, 2013 00:11
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When it comes to shuttle launching, you can see the shuttle do the roll-to-heads-up maneuver thru the ET cam. For night launches such as STS-116, STS-123, STS-126, STS-128, and STS-130, which direction do the shuttles roll? I believe it's the GUIDANCE officer's choice.
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#2948
by
psloss
on 04 Sep, 2013 00:48
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When it comes to shuttle launching, you can see the shuttle do the roll-to-heads-up maneuver thru the ET cam. For night launches such as STS-116, STS-123, STS-126, STS-128, and STS-130, which direction do the shuttles roll? I believe it's the GUIDANCE officer's choice.
No, that was the onboard (automated) guidance. That was discussed here in (sort of) real-time on several ascents (STS-132 comes to mind, since the CDR called down that he 'got it'). I'm sure the pros can elaborate, but I'll see if I can find a couple of old posts.
STS-132 -- start here, and continue in chronological order:
http://forum.nasaspaceflight.com/index.php?topic=21594.msg589222#msg589222STS-122:
http://forum.nasaspaceflight.com/index.php?topic=11773.msg239557#msg239557There's also a great ascent/aborts procedures handbook on L2 that goes into some technical detail.
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#2949
by
mkirk
on 04 Sep, 2013 02:01
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When it comes to shuttle launching, you can see the shuttle do the roll-to-heads-up maneuver thru the ET cam. For night launches such as STS-116, STS-123, STS-126, STS-128, and STS-130, which direction do the shuttles roll? I believe it's the GUIDANCE officer's choice.
No, that was the onboard (automated) guidance. That was discussed here in (sort of) real-time on several ascents (STS-132 comes to mind, since the CDR called down that he 'got it'). I'm sure the pros can elaborate, but I'll see if I can find a couple of old posts.
STS-132 -- start here, and continue in chronological order:
http://forum.nasaspaceflight.com/index.php?topic=21594.msg589222#msg589222
STS-122:
http://forum.nasaspaceflight.com/index.php?topic=11773.msg239557#msg239557
There's also a great ascent/aborts procedures handbook on L2 that goes into some technical detail.
Yep, it's all up to on board guidance (i.e. the General Purpose Computers).
All I'd like to add is that guidance is trying to achieve a roll angle of 0 degrees (heads up, wings level) and will roll the shortest distance to get there from the 180 degree (heads down, wings level) attitude the shuttle is in prior to the start of the maneuver. Even theough the attitude errors are quite small, the starting attitude prior to RTHU (roll to heads up) is never exactly 180.000, so whichever wing tip happens to be closest to the targeted 0 degree objective, that is the direction the stack will roll.
Mark Kirkman
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#2950
by
DaveS
on 04 Sep, 2013 04:10
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Does anyone know the diameters of the OME heatshields? I taalking about the truncated cones that covers the actual engine assy of the OMEs, where they attach to the actual OMS pods.
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#2951
by
iskyfly
on 11 Sep, 2013 19:10
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In a non malfunction scenario, do the ssme's always gimball together or are there times when one needs to be gimballed "out of sync" with the others?
If there is an engine malfunction requiring it to be shutdown, does it still gimball when the other engines gimball?
Thans!
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#2952
by
iskyfly
on 11 Sep, 2013 19:13
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As a programmer I am fascinated and amazed by flight computers.
In regards to the GPC's, has there ever been a fault during a mission that was attributed to a software bug?
Thanks!
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#2953
by
Jim
on 11 Sep, 2013 19:43
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In a non malfunction scenario, do the ssme's always gimball together or are there times when one needs to be gimballed "out of sync" with the others?
For roll control, there will be differential gimbaling.
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#2954
by
iskyfly
on 11 Sep, 2013 19:53
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Some time ago I posted a youtube video of sts-123 launch from inside the cockpit. There was a C&W alarm that sounded. The video is gone
Anybody know where I can find it? Thanks!
http://forum.nasaspaceflight.com/index.php?action=profile;u=14524;area=showposts;start=30"bias in the PC booster" 1:47
what does that mean?
whats with the counting right after liftoff?
also, is that a C&W alarm going off at 3:09 ?
also, compared to the handful of cabin vids ive seen this crew seems more vocal about their emotions ("i love you guys"), and more excited in their tone of voice (engine ig and liftoff) than others.
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#2955
by
psloss
on 11 Sep, 2013 20:03
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Some time ago I posted a youtube video of sts-123 launch from inside the cockpit. There was a C&W alarm that sounded. The video is gone Anybody know where I can find it? Thanks!
Web search: "sts-123 launch cockpit"
(Not the same clip, but from the same source, NASA TV.)
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#2956
by
mkirk
on 12 Sep, 2013 02:08
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Some time ago I posted a youtube video of sts-123 launch from inside the cockpit. There was a C&W alarm that sounded. The video is gone Anybody know where I can find it? Thanks!
http://forum.nasaspaceflight.com/index.php?action=profile;u=14524;area=showposts;start=30
"bias in the PC booster" 1:47
what does that mean?
whats with the counting right after liftoff?
also, is that a C&W alarm going off at 3:09 ?
also, compared to the handful of cabin vids ive seen this crew seems more vocal about their emotions ("i love you guys"), and more excited in their tone of voice (engine ig and liftoff) than others.
Box is referring to a "bias in the PC ducer" (which stands for chamber pressure transducer). Throttle/Power settings for the Space Shuttle Main Engines (SSMEs) and Orbital Maneuvering System (OMS) Engines are displayed to the crew in percent of chamber pressure. For example the nominal full power setting during ascent for the SSMEs is 104.5% of the rated thrust level. I don't recall the details from this flight, so I am not sure which engine indication had a bias or why it had a bias. Both the SSME and OMS PC indications are on the same display page - which is where he seems to be pointing as he reminds the MS2 Mike Foreman (who was the flight engineer and would also be scanning these instruments) of the biased indicator.
As for the counting; I am just guessing it is Dom's technique for maintaining situational awareness - I think he is counting up from about the T+4 second point where the crew confirmed the engines had actually throttled up to 104.5% (from the 100% used for engine start) to the point where he is expecting to see guidance initiate the roll program.
The caution and warning alarm was a series of fault messages related to the Left RCS (reaction control system). These were cauased by a failure of a dedicated signal conditioner (DSC) card.
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#2957
by
Specifically-Impulsive
on 13 Sep, 2013 20:28
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As a programmer I am fascinated and amazed by flight computers.
In regards to the GPC's, has there ever been a fault during a mission that was attributed to a software bug?
Thanks!
There have been a few. The last one I remember was on STS-126. Here is a writeup:
http://nsc.nasa.gov/SFCS/SystemFailureCaseStudyFile/Download/11
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#2958
by
iskyfly
on 14 Sep, 2013 16:48
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Thank you Jim, psloss, mkirk and S-I for your replies.
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#2959
by
iskyfly
on 14 Sep, 2013 16:54
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I am looking for a "primer" on open loop vs closed loop guidance.
Why doesn't the shuttle use closed loop from launch all the way up?
Thanks!
Anybody know where I can find it? Thanks!