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Space Forum / Shuttle / April 2005Shuttle Rocket Booster Foam
Exactly what does the foam do? Is it insulating the shuttle from the tank? Thanks! cc > Exactly what does the foam do? Is it insulating the shuttle from the > tank? No, it insulates the very cold liquid oxygen (LOX) and liquid hydrogen (LH2) in the big external tank (ET) from the temperature of the surrounding air. The insulation on the tank has nothing to do with the solid rocket boosters (SRB's) on either side of the tank, nor does it have anything to do with the orbiter proper... unless a piece falls off on the way up and hits the orbiter as happened with Columbia. > Thanks! Gazebo! > cc  SignatureChuck Stewart "Anime-style catgirls: Threat? Menace? Or just studying algebra?" >> Exactly what does the foam do? Is it insulating the shuttle from the >> tank? > > No, it insulates the very cold liquid oxygen (LOX) > and liquid hydrogen (LH2) in the big external tank (ET) > from the temperature of the surrounding air. Yes, an necessary function on the ground. > The insulation on the tank has nothing to do with the > solid rocket boosters (SRB's) on either side of the > tank, nor does it have anything to do with the orbiter > proper... unless a piece falls off on the way up and > hits the orbiter as happened with Columbia. Yes, large impacts can damage the heat shield. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com > Exactly what does the foam do? Is it insulating the shuttle from the tank? Nop. The tank is filled with unpressurized liquid hydrogen and liquid oxygen. At sea level pressure, those two really really really want to evaporate real fast. Evaporation needs heat to happen. By insulating the tank, it starves the liquids from the heat they need to evaporate, thus reducing loss of fuel due to evaporation. And it also reduces the amount of outdoors humidity that condendates onto the tank surface due to the cold generated by the fuel wanting to evaporate. Condensation freezes and forms ice which falls off in chunks during liftoff which can damage the shuttle. >> Exactly what does the foam do? Is it insulating the shuttle from the tank? > [quoted text clipped - 8 lines] > Condensation freezes and forms ice which falls off in chunks during > liftoff which can damage the shuttle. There are other ways to isnulate the tank while it's on the ground, to reduce boiling of hydrogen, condesation, keep it cold, chunk size. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com > Exactly what does the foam do? It falls off the tank during ascent. > Is it insulating the shuttle from the tank? No, the shuttle doesn't need any insulating from the tank. The Shuttle is covered with tiles that are great insulators. So the bottom of the Shuttle is covered with a great insulator, as good or better than the insulation on the tank. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com > Exactly what does the foam do? Is it insulating the shuttle from the > tank? The foam on the external tank (ET) performs three functions: 1) Protect the ET from aerodynamic heating during ascent. 2) Prevent ice formation on the exterior of the ET. 3) Minimize ET propellant boiloff. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. >> Exactly what does the foam do? Is it insulating the shuttle from the >> tank? > > The foam on the external tank (ET) performs three functions: > > 1) Protect the ET from aerodynamic heating during ascent. A small subset of the larger group called insulation on the Tank. Taking all the insulation required prelaunch to orbit is overkill. Take a look at page 123 of CAIB report, notice all the charring on the external tank for STS-7 (Figure 6.1-2). Compare that to STS-112 (Figure 6.1-3) there's no charring. It's really debatable as what is protecting what. Is the foam protecting the huge heat sink, or is the huge heat sink protecting the foam? Why does the STS-112 tank look so much clean as compared to the STS-7 tank? There is less insulation on the STS-112's tank, so surface of the foam is being cooled by the huge heat sink. Better yet, look at the ET presentation. http://www.caib.us/events/public_hearings/20030407/present_et.html Page 1, ET foam's purpose. Page 15, Aerodynamic Heating, look the very limited acreage called hot spots. Page 20, STS-26 ET in orbit picture, lots of charring Ditto Page 21, STS-32R, Page 22... Page 26, A chart of effort to reduce ET debris. STS-87, ET#-89, was the precipitating event that caused the ET group to finally make a change that started to reduce debris. The EPA mandated changes had made the debris situation worst. What changes were made to improve the debris situation. The chart says, "Reduced foam thickness" and "incorporated ?verri? holes". After this change, look at the ET in orbit picture on page 32 (STS-112), what a difference the reduced foam thickness has made with respect to charring. The few aerodynamic hot spots (Page 15) are still visibly charred, but all the excess foam on the tank is really pretty, looks like it just rolled out of the factory. The foam is definitely being protected by the huge heat sink that the tank is. And then there is Page 51, a really good chart showing foam thicknesses and what it's there for. A lot of it's for ice/frost and entry heating. It shows the Ascent Heating area's too, but the picture on page 32 is probably best illustration of were and how big the ascent hot spots are. Really not that much insulation acreage. > 2) Prevent ice formation on the exterior of the ET. A prelaunch function. > 3) Minimize ET propellant boil off. A prelaunch function. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com > The foam is definitely being protected by the huge heat sink > that the tank is. You obviously don't understand heat transfer (specifically thermal conductivity) if you've decided that a thermal sink of cryogens underneath an insulator will reduce surface charring on the opposite face . . . I'd suggest you study more aerodynamics, too, and consider variables such as stack trajectory and rotation when comparing charring of the ET insulation. SignatureHerb Schaltegger, GPG Key ID: BBF6FC1C "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." - Benjamin Franklin, 1759 <http://www.individual-i.com/> >>> Exactly what does the foam do? Is it insulating the shuttle from the >>> tank? [quoted text clipped - 11 lines] > what. Is the foam protecting the huge heat sink, or is the huge heat > sink protecting the foam? Reduce the thickness of the foam, the R value goes down and more heat flows. Conversely, it could be thought of as cold flowing the opposite direction. The inner cold aluminum side of the tank becomes slightly warmer, and the outside, the foam surface of the tank becomes slightly colder. The rate of flow has increased. So the foam is being actively cooled by conduction through the insulation. Prettier tank pictures in orbit, but colder on the ground too and possibly more ice. > Why does the STS-112 tank look so much clean as compared to the STS-7 > tank? There is less insulation on the STS-112's tank, so surface of the [quoted text clipped - 12 lines] > > Ditto Page 21, STS-32R, Page 22... Anybody have any other pictures of the ET after the decrease in thickness of insulation? Seems only STS-112's picture is in the ET presentation. > Page 26, A chart of effort to reduce ET debris. STS-87, ET#-89, was the > precipitating event that caused the ET group to finally make a change [quoted text clipped - 15 lines] > probably best illustration of were and how big the ascent hot spots are. > Really not that much insulation acreage. Page 56, peak aero heating during ascent for the ET is at around 100 seconds. So, the tank is still pretty full at peak heating. Also, interesting is that the "TPS cell burst" builds up after the loads on the foam begin to decrease. >> 2) Prevent ice formation on the exterior of the ET. > [quoted text clipped - 3 lines] > > A prelaunch function. 4) Entry Heating 5) RTLS Heating SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com >>> 2) Prevent ice formation on the exterior of the ET. >> [quoted text clipped - 7 lines] > > 5) RTLS Heating I'm obviously missing something here. In cases 4 and 5, why should you worry what happens to the ET? It's on its way to re-entry and planned destruction. SignatureRemove spam and invalid from address to reply. >>>> 2) Prevent ice formation on the exterior of the ET. >>> [quoted text clipped - 5 lines] >> >> 4) Entry Heating Entry heating has to do with debris footprint. As the ET reenters the atmosphere, delaying the time at which it ruptures and breaks up will reduce the footprint size. On the earlier Shuttle launches, the ET had a valve to tumble it. It was taken off at some point in the program. http://groups-beta.google.com/groups?q=et+tumble+valve+group:sci.space.*&start=0 &scoring=d&num=10&hl=en&lr=&as_drrb=q&as_mind=1&as_minm=1&as_miny=1981&as_maxd=3 0&as_maxm=4&as_maxy=2005&safe=off& Also, it's important during a TAL entry. TAL MECO and Entry are very close together. So immediately after TAL MECO and the ET separation, there is a separation burn to give the Orbiter enough clearance so that when the ET ruptures, none of the debris will impact the Orbiter. So rupture time is important. Getting the separation burn off on time, is important too. Eileen Collins actually had a real flight software failure in this critical time period during a simulation prior to STS-93, a really big deal in the flight software community. An RCS jet got stuck "on" after ET separation and the separation burn. http://groups-beta.google.com/group/sci.space.shuttle/msg/8467efa316cc3b22?hl=en <quote> And if you think an RCS jet can't get stuck "on", just ask the commander of STS-114. She had an RCS jet get stuck "on" during a critical portion of a TAL a simulation. It was a valid problem with the onboard flight software, not a simulation funny. The problem had been there for many years, it just had not manifested itself before. http://groups-beta.google.com/group/sci.space.shuttle/msg/097afd6be0bf712e?hl=en >> 5) RTLS Heating With RTLS the problem is with flying backwards in the atmosphere heating the bottom of the ET. > I'm obviously missing something here. In cases 4 and 5, why should you > worry what happens to the ET? It's on its way to re-entry and planned > destruction. Is President Reagan's offer for a free ET in orbit still good? If so, I still want my ET without all that foam on it. That way it won't be so messy when I cut it up to build my Mars Transfer Vehicle out of it. The ET is kind of like a LEO in situ resource, that NASA still thinks of as trash. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com >>>> 2) Prevent ice formation on the exterior of the ET. >>> [quoted text clipped - 11 lines] > worry what happens to the ET? It's on its way to re-entry and planned > destruction. RTLS = Return To Launch Site 4 and 5 describe an abort scenario in which the Shuttle literally turns under power to return to the vicinity of the Cape. The ET insulation is necessary to minimize propellant boiloff under these unusual conditions. There's probably additional heat load since it may be flying at a lower altitude. Under these _extreme_ circumstances, the ET would not break up and be destroyed by reentry heating, and would impact in the Atlantic somewhere off Florida. After separation from the orbit, the ET might well break up due to aerodynamic loads, however. Of course, this has never been attempted. --Damon >>>>> 2) Prevent ice formation on the exterior of the ET. >>>> [quoted text clipped - 18 lines] > >Of course, this has never been attempted. "I don't need to practice bleeding" comes to mind. Thanks to both of you. I had forgotten -if I ever knew - that they turn around still attached to the ET. Thank you to everyone for answering this question for me. I just never could find a good basic explanation when searching the web. I appreciate it! cc > Exactly what does the foam do? Is it insulating the shuttle from the > tank? > > Thanks! > > cc |
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