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#1
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Dynamic re-entry profile ?
Right now, the properties of the pre-determined re-entry profile are well
known and the shuttle's guidance computer is well programmed to handle it, allowing shuttle to de-orbit at the right time and reach the runway vicinity at the right altitude/speed. They even know prior to de-orbit burn the target runway. Fairly routine stuff. Ok, lets say that there was a problem with tiles and that they decided to attempt a very different re-entry profile to protect the damaged side (at the expense of other areas). Could the re-entry program be modified with a new re-entry profile while the shuttle is in orbit ? Could the guidance computers be programmed to perform the initial/different re-entry which would bring the shuttle to a random location at a specific altitude and more or less random speed, at which point ground could decide which runway to target and re-load the computers with the necessary info to reach that runway ? Or are time constraints such that they would really need to program the full re-entry in advance without any time to change anything once re-entry interface has been reached ? Is knowledge of re-entry aerodynamics such that NASA could quickly simulate a very different re-entry profile yielding information that would allow NASA to program the guidance computers to de-orbit at the right time and perform whatever manoeuvers (skips, turns etc) and bring the shuttle out of re-entry interface at the right location and altitude to allow landing at the right runway ? |
#2
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Dynamic re-entry profile ?
Adam Darren wrote:
Ok, lets say that there was a problem with tiles and that they decided to attempt a very different re-entry profile to protect the damaged side (at the expense of other areas). Could the re-entry program be modified with a new re-entry profile while the shuttle is in orbit ? Well for a start, they already fly the best profile available, so even if you could reprogram inflight, there is nothing better to run. Could the guidance computers be programmed to perform the initial/different re-entry which would bring the shuttle to a random location at a specific altitude and more or less random speed, at which point ground could decide which runway to target and re-load the computers with the necessary info to reach that runway ? I don't think so, IIRC it's one program that does the whole approach. You could likely fly manual though. Thanks, David |
#3
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Dynamic re-entry profile ?
Ok, lets say that there was a problem with tiles and that they decided to attempt a very different re-entry profile to protect the damaged side (at the expense of other areas). Well for a start, they already fly the best profile available, so even if you could reprogram inflight, there is nothing better to run. Not true. Columbia was flying a hot profile to attemot to warm its tires.after its long cold soak in space. Without the pictures we dont have enough info to ever know exactly if the crew could of been saved. |
#4
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Dynamic re-entry profile ?
Not sure but I seem to recall someone saying Orlando International had the
capability to allow the shuttle to land. The most easterly runway is extremely long I assume in case an unusually large alligator, 60 feet or so, decided to sun itself on the shuttle landing strip and refused to leave. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#5
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Dynamic re-entry profile ?
"Adam Darren" wrote in message
Ok, lets say that there was a problem with tiles and that they decided to attempt a very different re-entry profile to protect the damaged side (at the expense of other areas). I don't believe there's really much of a predictable capability to do this; the black side of the orbiter gets hot - the grey areas get really hot, and the white areas aren't supposed to get very hot. ;-) Aerodynamics, control, and thermal constraints dictate the attitude the orbiter flies at during entry. "Protecting" a damaged area - even if theoretically possible - would likely involve flying in an un-trimmed state and require constant jet firings and also possibly put other areas of the vehicle over their allowable design temperatures and creating more (and possibly worse) problems. Could the re-entry program be modified with a new re-entry profile while the shuttle is in orbit ? There are three parameters that are very important at EI (entry interface): energy (altitude and speed), REI (range at entry interface), and the angle at EI. REI and the angle at EI have to be within a specific range and are dependent on many things including vehicle weight, etc. The shuttle's entry conditions have been adjusted over the years, as I recall, to result in the most benign entry possible. There has been some discussion about decresing the angle at EI *slightly* and increasing the REI *slightly* in order to provide a lower *peak* temperature, but that would result in greater tile backface temperatures - there's always a tradeoff. I have seen other papers that purport to lower the temps even further, but they are only theoretical and have not been tested or evaluated in any way. Could the guidance computers be programmed to perform the initial/different re-entry which would bring the shuttle to a random location at a specific altitude and more or less random speed, at which point ground could decide which runway to target and re-load the computers with the necessary info to reach that runway ? If I am not mistaken, if the drag was greater than expected and the orbiter for some reason could not make the planned site, the orbiter could be retargeted to another site that was reacheable. The crew would need to know exactly which site was best for them, though, and potential landing sites are not that common. I think with upcoming software releases there are about 90 runways that will be in the orbiters database. Selecting the right one will be made easier with software that I am involved in testing right now. See http://www.spacecoretech.org/coretech2002/ssa.html. There are some papers hosted there that explain the capabilities of SAFM: 1) Onboard Determination of Vehicle Glide Capability for Shuttle Abort Flight Management (SAFM) 2) Shuttle Flight Abort Management (SAFM) - Application Overview This new application is possible due to the capabilities provided as part of the CAU program. [Another poster in a separate thread has claimed that the MEDS displays and/or CAU is somehow responsible or related to the demise of Columbia because of "improperly spent funds", but I find this claim to be without merit and misguided]. You might find the above documents to be an interesting read. Jon |
#6
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Dynamic re-entry profile ?
Jon Berndt wrote:
"Adam Darren" wrote in message Ok, lets say that there was a problem with tiles and that they decided to attempt a very different re-entry profile to protect the damaged side (at the expense of other areas). I don't believe there's really much of a predictable capability to do this; the black side of the orbiter gets hot - the grey areas get really hot, and the white areas aren't supposed to get very hot. ;-) Aerodynamics, control, and thermal constraints dictate the attitude the orbiter flies at during entry. "Protecting" a damaged area - even if theoretically possible - would likely involve flying in an un-trimmed state and require constant jet firings and also possibly put other areas of the vehicle over their allowable design temperatures and creating more (and possibly worse) problems. Could the re-entry program be modified with a new re-entry profile while the shuttle is in orbit ? There are three parameters that are very important at EI (entry interface): energy (altitude and speed), REI (range at entry interface), and the angle at EI. REI and the angle at EI have to be within a specific range and are dependent on many things including vehicle weight, etc. The shuttle's entry conditions have been adjusted over the years, as I recall, to result in the most benign entry possible. There has been some discussion about decresing the angle at EI *slightly* and increasing the REI *slightly* in order to provide a lower *peak* temperature, but that would result in greater tile backface temperatures - there's always a tradeoff. I have seen other papers that purport to lower the temps even further, but they are only theoretical and have not been tested or evaluated in any way. They could reduce the EI flight path angle further and pick a little extra payload by changing the initial roll at EI to 180 degrees. Essentially, grabbing a hold of the atmosphere and pulling themselves deeper into it. Payload would be slightly increased because the deorbit burn delta-V requirements would be reduced. Additionally, if they had realtime heating sensors in the wing, there is probably a small window where the Orbiter could abort the entry. Too much heat in the wing, roll to heads up, raise perigee slightly and apply a patch to the Orbiter and try again. Although this might come at the cost of a little payload, as more OMS/RCS FPR would be required. Craig Fink |
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