Author Topic: Shuttle Q&A Part 5  (Read 1535210 times)

Offline mkirk

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Re: Shuttle Q&A Part 5
« Reply #3780 on: 01/24/2023 02:50 pm »
Mark: thanks for the answer. It was something that had been on my mind on and off again for a few years. In my mind up until now was that the "north" that the MCC PAO stated was in relation to the orbiter coordinate system where "north" was +X.

Another DPS question: Did MM104 OMS-1 MNVR EXEC take in account the additional dV of the MPS propellant dump when calculating the dV targets?


Yes, but not directly in the OMS 1 Targets, but in how the orbiter achieved the desired Targets.

The OMS 1 Burn was conducted using a “closed loop” guidance scheme known as PEG 4 (powered explicit guidance).  PEG 4 was trying to achieve specific vertical and horizontal velocity changes (Delta V) over a certain point above the earth.  Closed loop guidance meant the orbiter knew where it was at the start of the burn (state vector at the time of ignition) and where it wanted to be (state vector at the end of the burn).  During the burn, sensed accelerations (i.e. IMU data) were used to update the current state vector - this was then compared to the desired OMS cutoff conditions.

On a “Standard Insertion”  mission like STS-1, the “Automatic” MPS Dump started at OMS 1 Ignition.  If I recall correctly, the Dump contributed about 10 to 11 feet per second of Delta V. 
Btw, the rule of thumb was that 2 fps of Delta V contributed 1 nautical mile to the Perigee Altitude (Hp).

So, if the Dump occurred as planned during the OMS 1 Burn, the continuously updated OMS cutoff conditions needed to achieve the desired target conditions, would occur slightly earlier than if the Dump was not taking place.



(Someone like Jorge - if he still lurks within these threads - would probably be able to give you a much better explanation.)


Mark Kirkman
“NASA Space Shuttle Hugger”
« Last Edit: 01/24/2023 02:50 pm by mkirk »
Mark Kirkman

Offline John2375

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Re: Shuttle Q&A Part 5
« Reply #3781 on: 01/27/2023 07:58 pm »
Thanks, Mark -  I understand what you’re saying and it especially makes sense when determining runway 17 vs 23, for example. And I know sometimes at KSC they’d accept  a little tailwind component so the sun angle wasn’t a factor.
I was just curious about my example of STS-36: runway 23 vs 22- the winds component would be similar, sun angle as well, and the previous flight STS-32 used 22.

Also- STS-37 had some issues with the upper level winds not being as forecast on the HAC. Eileen  Collins writes in her book that STS-63 had stronger winds on the HAC than they excepted.. we’re there any other flights you know of that had to do some good piloting to get the orbiter to the runway?!

Offline John2375

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Re: Shuttle Q&A Part 5
« Reply #3782 on: 02/21/2023 07:47 pm »
https://www.americaspace.com/2021/01/03/stopping-the-shuttle-remembering-the-drag-chute-30-years-on/

First paragraph.. references a landing that “almost bounced…” ? Any idea which flight that refers to?

Offline penguin44

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Re: Shuttle Q&A Part 5
« Reply #3783 on: 02/22/2023 02:07 am »
Either the final landing test of Enterprise or sts-3 perhaps

Offline John2375

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Re: Shuttle Q&A Part 5
« Reply #3784 on: 02/23/2023 02:14 pm »
most likely- and certainly STS-51D for the seized brakes/blown tire (why didn’t the orbiter have nose wheel steering from the get-go?

STS-91 kind of bounced, not hard but there are 2 distinct main gear  touchdowns ..

Offline Nicolas PILLET

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Re: Shuttle Q&A Part 5
« Reply #3785 on: 06/03/2023 02:01 pm »
I've seen this replica in storage in Steven F. Udvar-Hazy Center two months ago. Someone knows from which display model it comes ?
Nicolas PILLET
Kosmonavtika : The French site on Russian Space

Offline AS_501

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Re: Shuttle Q&A Part 5
« Reply #3786 on: 07/18/2023 11:14 pm »
I'm curious about one aspect of the radiators inside the payload bay doors.  When the orbiter was flying on its own (i.e. not docked to Mir or ISS), was the payload bay oriented away from the Sun as often as possible to minimize Solar heating of the radiators?  When the bay was facing the Sun, did the radiators lose some of their cooling efficiency?  I'm not well versed in the underlying physics of the radiators.
Thx
Launches attended:  Apollo 11, ASTP (@KSC, not Baikonur!), STS-41G, STS-125, EFT-1, Starlink G4-24, Artemis 1
Notable Spacecraft Observed:  Echo 1, Skylab/S-II, Salyuts 6&7, Mir Core/Complete, HST, ISS Zarya/Present, Columbia, Challenger, Discovery, Atlantis, Dragon Demo-2, Starlink G4-14 (8 hrs. post-launch), Tiangong

Offline Jorge

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Re: Shuttle Q&A Part 5
« Reply #3787 on: 07/19/2023 02:28 am »
I'm curious about one aspect of the radiators inside the payload bay doors.  When the orbiter was flying on its own (i.e. not docked to Mir or ISS), was the payload bay oriented away from the Sun as often as possible to minimize Solar heating of the radiators?  When the bay was facing the Sun, did the radiators lose some of their cooling efficiency?  I'm not well versed in the underlying physics of the radiators.
Thx

The TL; DR answer is that soon after the start of the program the "free-flight" attitude standardized on payload bay toward Earth with one wing pointed at the velocity vector. Later in the program the standard was payload bay to Earth, tail to velocity vector.

Long answer: It was a balance between thermal, comm, and orbital debris concerns. On early flights it was learned that pointing one axis of the Orbiter at the sun for too long caused too much of a thermal imbalance between the sunlit and shaded sides, resulting in difficulty closing the payload bay doors before deorbit. Payload bay to Earth maintained thermal balance for closing the doors while still providing adequate heat rejection through the radiators. Once TDRSS was available, wing to velocity vector (therefore nose out of plane) ensured that at least one S-band antenna (arranged around the nose) was pointed at a TDRS satellite for near-continuous comm. Later, when orbital debris became more of a concern, tail to velocity vector was chosen to shield the cabin from MMOD. By this time TDRS-Z was available to mitigate the comm loss due to S-band blockage "off the tail".
JRF

Offline John2375

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Re: Shuttle Q&A Part 5
« Reply #3788 on: 07/20/2023 12:50 pm »
I’ve tried searching but to no avail;  I recall somewhere on here, there was a dramatic photo of the forward fire team “caught” outside their bunker during launch.. I think the story was that a hold was called for T-31 so they went outside.. then the hold was cancelled and they didn’t have time to get back inside..  there was talk on here of which launch it was but idk if it was ever determined ?

Offline Thorny

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Re: Shuttle Q&A Part 5
« Reply #3789 on: 07/21/2023 05:54 pm »
I’ve tried searching but to no avail;  I recall somewhere on here, there was a dramatic photo of the forward fire team “caught” outside their bunker during launch.. I think the story was that a hold was called for T-31 so they went outside.. then the hold was cancelled and they didn’t have time to get back inside..  there was talk on here of which launch it was but idk if it was ever determined ?

I'm not sure if it was ever identified as to which mission it was, but here is the photo...

https://www.thedrive.com/content-b/message-editor%2F1642726676274-lzajden.jpeg?auto=webp&optimize=high&quality=70&width=1440
« Last Edit: 07/21/2023 05:57 pm by Thorny »

Offline joncz

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Re: Shuttle Q&A Part 5
« Reply #3790 on: 07/21/2023 06:07 pm »

I'm not sure if it was ever identified as to which mission it was, but here is the photo...

https://www.thedrive.com/content-b/message-editor%2F1642726676274-lzajden.jpeg?auto=webp&optimize=high&quality=70&width=1440

Quote
Yes, the carrier vehicle is outside the pad's perimeter fence. This was M-113/Hard Top One's astronaut rescue vehicle and team (I think Unit #HE-704-080) on station at A/B 4, just under a mile from the shuttle on Pad B, during the launch of STS-26/Discovery in Sept. 1988. I think the photo seen is one that had been autographed by one of the 12-member astronaut pad rescue teams that Bob had gotten from me long ago.

From http://www.collectspace.com/ubb/Forum29/HTML/001965.html

Offline DaveS

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Re: Shuttle Q&A Part 5
« Reply #3791 on: 09/23/2023 07:08 am »
Can someone with a bit more knowledge than me, explain how the PLBD NO-GO diagram is supposed to be read in terms of the position assessment outlined in the STS-1 Post Insertion checklist? Crippen reported that it was "Position 1A" that was determined during the PLBD latch and cycle tests.
« Last Edit: 09/23/2023 07:09 am by DaveS »
"For Sardines, space is no problem!"
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"We're rolling in the wrong direction but for the right reasons"
-USA engineer about the rollback of Discovery prior to the STS-114 Return To Flight mission

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