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#3700 by DaveS on 01 Sep, 2020 15:03
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Dumb question: what prevented the Shuttle's SRB's from filling with water and sinking after ocean impact? Were balloons used?
No balloons. The SRBs were naturally buoyant. The first task in SRB recovery was to install a Diver Operated Plug (DOP) that would allow the booster to switch from from the vertical splashdown orientation to the horizontal tow orientation by "de-watering" the boosters, IE by pumping out the water from the inside. That caused the boosters to rise until they fell over and were ready for the tow back to Port Canaveral. -
#3701 by Proponent on 01 Sep, 2020 17:03
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So the boosters naturally floated in a vertical, nozzle-down orientation after splashdown?
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#3702 by DaveS on 01 Sep, 2020 17:17
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So the boosters naturally floated in a vertical, nozzle-down orientation after splashdown?
Yes. Their natural orientation the water was vertical as they then were just water-filled steel tubes. -
#3703 by Fequalsma on 01 Sep, 2020 20:19
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They were partially filled with water after splashdown. The trapped air was what made them buoyant in "spar mode". After the Diver-Operated Plug was installed, and the SRB de-watered, they were towed back in "log mode".
F=maSo the boosters naturally floated in a vertical, nozzle-down orientation after splashdown?
Yes. Their natural orientation the water was vertical as they then were just water-filled steel tubes. -
#3704 by DaveS on 20 Sep, 2020 19:44
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Could someone detail the "standard" set ascent Performance Enhancements used in the latter half of the program?
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#3705 by usn_skwerl on 10 Oct, 2020 01:00
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I can't seem to find it, but I'm curious about the orbiter's tire pressures?
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#3706 by Hobbes-22 on 10 Oct, 2020 06:58
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340 psi (main gear) and 300 psi (nose gear). (from an article on the Nasa site that's no longer there, unfortunately).
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#3707 by AnalogMan on 10 Oct, 2020 10:41
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There are slightly different pressures given in the Shuttle Crew Operations Manual (from 2008):
Prior to launch tires are inflated with nitrogen as follows:
Nose landing gear 350 psi (rated for max load of 45,000 lbs per tire and 217 knots max landing speed, can be reused once)
Main landing gear 370 psi (rated for max load of 132,000 lbs per tire and 225 knots max landing speed, life of one landing only)
Manual can be downloaded here (1161 pages, 41.2MB):
https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf -
#3708 by maia125 on 11 Oct, 2020 22:26
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I've learned that when Entreprise was at Pad 39-A, her External Tank was filled "through Enterprise’s mock Main Propulsion System – with hundreds of thousands of gallons of Liquid Hydrogen and Liquid Oxygen. Source: https://www.nasaspaceflight.com/2012/04/space-shuttle-enterprise-the-orbiter-that-started-it-all/
Does anybody know more about this "mock Main Propulsion System"? Did Enterprise had External Tank umbilicals?
Thanks in advance.
Edit: corrections. -
#3709 by DaveS on 12 Oct, 2020 17:07
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I've learned that when Entreprise was at Pad 39-A, her External Tank was filled "through Enterprise’s mock Main Propulsion System – with hundreds of thousands of gallons of Liquid Hydrogen and Liquid Oxygen. Source: https://www.nasaspaceflight.com/2012/04/space-shuttle-enterprise-the-orbiter-that-started-it-all/
There was none. Enterprise only had fake SSME nozzles made from cast iron. The only umbilicals that Enterprise ever had were for interfacing with the SCA during the ALTs. She didn't ever have any T0 umbilical panels on her aft engine compartment where the TSMs on the then unfinished MLP-1 would have interfaced with the orbiter. As far as I know, Enterprise's check out of KSC was all mechanical in nature, very similar to the so called Facility Checkouts she did in the mid-80's of Vandenberg's shuttle facilities.
Does anybody know more about this "mock Main Propulsion System"? Did Enterprise had External Tank umbilicals?
Thanks in advance.
Edit: corrections.
I have attached a photo taken during the rollout of the LOX TSM showing that the area in question on Enterprise is void of any umbilicals extending from the TSM. So they couldn't have loaded any cryos at the pad, it was physically impossible.
I've also attached a photo of the same TSM and area of Columbia taken during the STS-1 rollout showing the umbilicals in place.
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#3710 by Hog on 12 Oct, 2020 17:44
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If they could load no cryogens, how/when were the "beanie cap" requirements first noticed?
https://www.nasaspaceflight.com/2012/04/space-shuttle-enterprise-the-orbiter-that-started-it-all/
"She was then rolled out to launch pad 39A on 1 May 1979. During rollout, Enterprise was driven at various speeds to measure and note the various vibration strains on the fully-mated Shuttle stack. This was used to determine an optimal rollout speed for operational Space Shuttle missions.
Once at the pad, Enterprise helped validate launch pad procedures – with her biggest test and benefit to the ground processing operations coming during the full-up Wet Countdown Dress Rehearsal when she helped simulate External Tank fueling operations for launch.
During the test, Enterprise’s ET was filled – through Enterprise’s mock Main Propulsion System – with hundreds of thousands of gallons of Liquid Hydrogen and Liquid Oxygen.
During this time, the venting capabilities of the gaseous hydrogen vent line/system were tested.
However, something quite disturbing was discovered during this test – ICE was building up at the top of the External Tank where the gaseous oxygen was being allowed to vent directly from the tank.
This posed a significant problem as ice was already understood to be a serious hazard to the Shuttle orbiter’s Thermal Protection System tiles and panels.
With the maiden voyage of the Shuttle just under two years away, NASA needed a solution to this newly-discovered problem."
Interesting. Hmm. -
#3711 by DaveS on 12 Oct, 2020 18:05
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If they could load no cryogens, how/when were the "beanie cap" requirements first noticed?
Probably through model testing, not using Enterprise.
Interesting. Hmm. -
#3712 by maia125 on 13 Oct, 2020 00:04
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Thank you all for your answers. Maybe they found a way to fill the ET bypassing Enterprise and TSM.If they could load no cryogens, how/when were the "beanie cap" requirements first noticed?
Probably through model testing, not using Enterprise.
Interesting. Hmm. -
#3713 by DaveS on 13 Oct, 2020 00:17
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That would be a no-go as the pad cryo facilities tie into the cryo lines on the exterior of the MLP which enter the MLP on Side 1 (south side when it is at the pad) and is routed up through the TSMs. And the fill/drain of the ET is where the orbiter is mated to it (aft structure), so they're blocked off when the orbiter is mated to it.
Thank you all for your answers. Maybe they found a way to fill the ET bypassing Enterprise and TSM.If they could load no cryogens, how/when were the "beanie cap" requirements first noticed?
Probably through model testing, not using Enterprise.
Interesting. Hmm. -
#3714 by maia125 on 13 Oct, 2020 00:37
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Would it be possible to route the LH2 and LOX plumbing through Aft Fuselage Access Doors? But since you said that Enterprise didn't have ET propellant umbilicals, it would be no use.
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#3715 by jbirdav8r on 13 Oct, 2020 16:01
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I believe the ET used for the Enterprise facilities verification at KSC was a boilerplate. I think it was likely the same ET that was used in the MGVT program at Marshall. It only had a notional LOX feedline, no pressurization lines, and I don't even think it had any LH2 feedline at all...maybe a stub. Importantly, I don't even think it had any foam insulation. Even if you could fill it, it wouldn't be a very good idea.
There would be opportunities to catch the LOX vent ice issues in real-world tests. Importantly, the Main Propulsion Test Article (MPTA) tests at NSTL (later Stennis). The MPTA had an actual, functioning, insulated external tank that was filled and drained through an actual orbiter aft compartment. Whether or not such an issue was identified in the tests, I don't know, but it was possible.
I think the article you've referenced is just incorrect.
As an aside, MPTA-098 still exists...at least as of several years ago. I was walking through the Space and Rocket Center back lawn in Huntsville and came across it, sitting on the dirt like an old utility shed. There wasn't any signage or anything. What a piece of hardware! You could get close enough to touch it, and probably crawl into it (no, I didn't). The external tank from those tests holds the "Pathfinder" mockup, also there in Huntsville.
Edit to add: Two photos. One is Enterprise stacking ops in the VAB. The other is stacking for the MGVT at Marshall. I'm almost positive it's the same tank.
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#3716 by AnalogMan on 13 Oct, 2020 19:09
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An article from NASA also says that the Enterprise stack was used for cryogenic tests on the ET:
"Roll out to Launch Pad 39A occurred on May 1, and again KSC employees and their families were invited to view the event. With Enterprise mated to its ET and SRBs perched on the MLP, a total mass of about 11 million pounds, and riding atop the Mobile Transporter, technicians drove the stack at varying speeds to determine the optimum velocity to minimize vibration stress on the vehicle. The rollout process took about eight hours to complete. Once at the pad, engineers used Enterprise to conduct fit checks and to validate launch pad procedures. The most critical step was a countdown demonstration test during which the ET was filled with super-cold liquid hydrogen and liquid oxygen. A significant discovery that ice built up at the top of the ET during this process led to the addition of the gaseous oxygen vent hood (familiarly known as the “beanie cap”) to the launch pad facility and a procedure to retract it just a few minutes before liftoff. This prevented the dangerous buildup of ice during the countdown and was perhaps Enterprise’s greatest contribution as a test vehicle during its time at the launch pad."
https://www.nasa.gov/feature/40-years-ago-space-shuttle-enterprise-rolls-to-the-pad -
#3717 by maia125 on 13 Oct, 2020 22:17
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It seems that we have contradictory information. I found an article on collectspace.com (http://www.collectspace.com/news/news-020817a-michoud-tornado-shuttle-external-tank.html) that says that the External Tank used with Enterprise at KSC was the same that was used on the Mated Vertical Ground Vibration Test performed at Marshall. The ET in question was the "ET-GVTA" (external tank-ground vibration test article):Quote
ET-GVTA was one of the first three external tanks that was manufactured at Michoud. Built to represent a flight article, it was not covered in insulating foam like those that would later launch to space, but was painted white.
"ET-GVTA played a critical role in the early testing for the space shuttle," said Dennis Jenkins, the author of the new book, "Space Shuttle: Developing an Icon, 1972-2013" and a former project manager for the space shuttle program. "It was the subject of several iconic photos."
First used with the prototype orbiter Enterprise for a series of vibration tests at NASA's Marshall Space Flight Center in Alabama, ET-GVTA helped establish the bending modes and nodal crossing points to validate various analyses and locate the rate gyros and accelerometers used by the flight control system.
It was then moved to the Kennedy Space Center in Florida for a series of facility verification tests, culminating with it being paired with two solid rocket boosters and mounted to Enterprise in the Vehicle Assembly Building and moving to Launch Complex 39A for the first time.
ET-GTVA was subsequently shipped back to Louisiana for its possible refurbishment into a flight tank, but that did not happen. Instead, it was disassembled and its liquid oxygen and liquid hydrogen tanks, as well as its interstage, were put into storage, eventually being parked outside Building 103, the facility's main manufacturing building.
Photo credits: Dennis Jenkins.
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#3718 by psloss on 13 Oct, 2020 23:44
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There would be opportunities to catch the LOX vent ice issues in real-world tests. Importantly, the Main Propulsion Test Article (MPTA) tests at NSTL (later Stennis). The MPTA had an actual, functioning, insulated external tank that was filled and drained through an actual orbiter aft compartment. Whether or not such an issue was identified in the tests, I don't know, but it was possible.
ET-MPTA was delivered to NSTL in September, 1977, and had gone through several initial tanking cycles and firing tests through 1978 while mated with MPTA-098 in the B-2 Test Stand. (Those MPTA tests continued into early 1981.)
What may be getting conflated is the testing of GOX vent system designs that began in the LETF in late Summer of 1979.
Unfortunately, it's harder to find contemporaneous information to connect the proverbial dots since this history significantly predates the WWW.
There's an NTRS paper from 1982 that talks about development of the GOX vent system but doesn't provide background how the issue came up originally. -
#3719 by woods170 on 14 Oct, 2020 16:58
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If they could load no cryogens, how/when were the "beanie cap" requirements first noticed?
https://www.nasaspaceflight.com/2012/04/space-shuttle-enterprise-the-orbiter-that-started-it-all/
"She was then rolled out to launch pad 39A on 1 May 1979. During rollout, Enterprise was driven at various speeds to measure and note the various vibration strains on the fully-mated Shuttle stack. This was used to determine an optimal rollout speed for operational Space Shuttle missions.
Once at the pad, Enterprise helped validate launch pad procedures – with her biggest test and benefit to the ground processing operations coming during the full-up Wet Countdown Dress Rehearsal when she helped simulate External Tank fueling operations for launch.
During the test, Enterprise’s ET was filled – through Enterprise’s mock Main Propulsion System – with hundreds of thousands of gallons of Liquid Hydrogen and Liquid Oxygen.
During this time, the venting capabilities of the gaseous hydrogen vent line/system were tested.
However, something quite disturbing was discovered during this test – ICE was building up at the top of the External Tank where the gaseous oxygen was being allowed to vent directly from the tank.
This posed a significant problem as ice was already understood to be a serious hazard to the Shuttle orbiter’s Thermal Protection System tiles and panels.
With the maiden voyage of the Shuttle just under two years away, NASA needed a solution to this newly-discovered problem."
Interesting. Hmm.
Emphasis mine.
Don't know where Chris G. (the author of the linked NSF article) got this from but it is a load of incorrect.
Enterprise never had a mock Main Propulsion System. Neither was a tanking test ever performed with Enterprise, while sitting on the pad:Quote from: Dennis R. JenkinsDuring April 1979, OV-101 was mated to a pair of inert solid rocket boosters and the ET (serial number 2) scheduled to be used on STS-1. The stack was transported atop MLP #1 to Pad 39A on 1 May 1979. During almost three months at the pad, Enterprise would help verify that maintenance platforms mated to the vehicle in the correct locations, and that crew escape procedures worked properly. On 23 July 1979, Enterprise was rolled back to the VAB to be demated from the SRBs and ET.
Dennis R. Jenkins is generally recognized as THE expert on Space Shuttle history. The mere fact that his description of Enterprise's stint at LC-39A does not mention any tanking test is clear evidence that such rumoured tanking test never took place.
And when one contemplates other evidence, it becomes clear that such a rumoured tanking test did indeed never take place.
On L2 are several high resolution images available of Enterprise, including the area where the main connections to the STA and ET are. Particularly that image shows very clearly that there is NO hookup for the LOX feedline present. NO hookup for the LH2 feedline either. Other images on L2 show the interior of Enterprise's aft area. Again no feedlines for LOX or LH2. Publically available images of Enterprise show clearly that there are no hookups for the TSMs present on Enterprise. And high resolution images of Enterprise's rollout (again in L2) to LC-39A again clearly show that the TSM umbilicals were NOT hooked up to Enterprise's aft section.
There is also other circumstantial evidence that points to Enterprise not having a mock Main Propulsion System. Dennis R. Jenkins points out that Enterprise was again used as a facilities checkout vehicle at Vandenburg pad SLC-6 in 1985. He also notes that in early 1986 OV0192 (Columbia) was scheduled to arrive at SLC-6 "to conduct tanking tests".
Why would Vandenberg need Columbia for tanking tests? The answer is simple: because Enterprise does not contain the systems necessary to conduct a tanking test.
It is correct that NASA, in 1979, became aware of the ice build-up issue around the GOX vent. But this was due to tanking tests on ground-test articles of the ET, likely the MPTA-ET tests at Stennis. Those tests took place with a tanking test-article of the ET, connected to the Main Propulsion Test Article (MPTA) and had a functioning GOX vent. It was likely those tests that resulted in the recognition of the problem which led to the late development of the GOX vent arm.
The discovery of this problem was in fact so late into development that the GOX vent arm was not ready in time to support STS-1 as originally intended. Problems with the GOX vent seals during tanking tests and the FRF eventually led to the GOX vent hood being used in an "umbrella" mode only for STS-1, providing heated GN2 to prevent ice buildup. The GOX was allowed to escape in the air around the ET.Not until STS-2 did the GOX vent arm become operational as intended.