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SLS booster test
In article , says...
Jeff Findley wrote: Yup. The vibrations go from subsonic, bone shaking, vibrations, through the audible sound range. In other words, they're *loud*. So, if you are the US Government launching a billion dollar satellite to do top secret stuff, would you want it shaken and blasted with noise for the first two minutes of flight? Weren't at least a few classified satellite missions flown with Shuttle? http://www.airspacemag.com/space/sec...318554/?no-ist suggests there were something like 11 of them. Yes, and since they were classified, we currently have no idea how much money it cost to qualify those payloads to fly on the shuttle. But I'm sure that they had to be put on shaker tables inside acoustic chambers to simulate the launch environment. After testing, any parts or assemblies which had issues would need to be "beefed up" and the test re-run. Eventually these documents will be declassified, and we'll be able to read about how hard (or easy) it was to qualify these payloads for shuttle launch. For now, all I have is vague anecdotal evidence that it was not at all fun to qualify some parts of these payloads. But there are technical papers on the vibration issue that are not classified. For example at http://ntrs.nasa.gov/, search for: Vibration Isolation for Launch of a Space Station Orbital Replacement Unit Document ID: 20100042181 From the abstract of the above document: Random vibration testing of one ORU to equivalent Space Shuttle launch levels revealed that its qualification and acceptance requirements were exceeded. An isolation system was designed to mitigate the structure- borne launch vibration environment. To protect this ORU, the random vibration levels at 50 Hz must be attenuated by a factor of two and those at higher frequencies even more. Design load factors for Shuttle launch are high, so a metallic load path is needed to maintain strength margins. Isolation system design was performed using a finite element model of the ORU on its carrier with representative disturbance inputs. Iterations on the modelled to an optimized design based on flight proven SoftRide MultiFlex isolators. Component testing has been performed on prototype isolators to validate analytical predictions. Right from the abstract, "Design load factors for Shuttle launch are high". And in this case, a special vibration isolation system had to be designed for the ORU or "orbital replacement unit" due to this fact. So, engineering cost went up and launch mass increased for this ORU due to the vibrations from the SRBs. Again, large segmented solids are not at all ideal for a launch vehicle. SLS increases the SRB size from 4 segments (used on the shuttle) to 5 segments. There will surely be an increase in vibrations due to this change. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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