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#11
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Capsule for new space initiative
Charles Buckley:
Anvil wrote: What should be reused from Apollo is the outer shape of the capsule and it's associated aero-thermodynamic data. *snip* Even if they reuse the Apollo shape and config, there is enough of an argument that there will be a radically different density variation that the thermal loading figures might be off by quite a bit. IIRC, thermal loading is a combination of aspect ratio and wing loading. With wing loading being the greater portion of the equation. You change the density of the capsule by using lightweight materials and shrinking the avionics systems and you are essentially designing a new thermal environment that would have to be analysed from scratch. ----- The shape was developed using mathematical models, small physical models in a plasma wind tunnel, and empirical data gathered from flights. The shape and it's properties are very much like selecting an airfoil shape for a wing. It has coefficients of lift and drag along with properties specific to ballistic reentry. Still I would like to keep about the same size and weight but a size change is within college level design study scale. My worry is that even with lighter weight materials and avionics the tendency will be a heavier capsule. So what to do. Someone will have to play the part of a goal tender and fend off add-ons and what-ifs. Another items that should be considered, but are contrary to space launch systems is leaving instrumentation and panel space for the future and carrying ballast. That last one will go over well, but planning from the start to have a weigh margin and a simple method to adjust the center of gravity is prudent. One team will come out lighter than expected another will be heavy but they will be on opposite sides of the balance. Next lets publish our capsule as a standard. Shape, weight range, cg location, all connections and physical interfaces, voltages and power available, radio frequencies and telemetry signals... It is unrealistic to assume another country would build a compatible capsule or module in the near future, however it is best to start early, build, and rebuild any standard (assuming space faring is in our future). |
#12
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Capsule for new space initiative
Nick Maclaren:
A mere year's delay and factor of 3 overrun is pretty good under those conditions - there are lots of examples that have been much worse .... ----- Agreed, but I am lucky to be in established industry. Space related start-ups are marginally funded buy investors who are not infinitely patient. They are lucky if they get funding, much less one shot with one customer. Missing your launch date and running out of cash by first one-third of your program adds you to the list of where are they now (interesting technology never developed). The question might be: If they knew, it would take five more years and cost four times what they thought on their first guess, would they have been able to attract investors? customers? |
#13
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Capsule for new space initiative
Abrigon Gusiq wrote: I remember a "joke" once, that if the Wright brothers had done their famous flight today, it would never have gotten of the ground, due to OSHA/EPA, and other regulations. As well as enviromental and other fun rules.. Remember they were in an area with alot of birds, some likely indangered.. As well as to ask for someone other than one of the brothers to fly it, if the pilot died, the family might sue. The inspiration for this might of been a short story Mark Twain wrote about a German shipping inspector getting a look at Noah's Ark, which broke more than a few regulations. Pat |
#15
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Capsule for new space initiative
In article ,
Space Cadet wrote: ...Even the Apollo guys would have done things differently if they'd had to do it again -- many decisions made in haste turned out to be less than ideal. Henry, do you have specific examples of somethings the Apollo guys would have done differently? Just off the top of my head... The CM heatshield turned out to be grossly overbuilt. The specs were fixed at a time when they didn't have enough data and they knew it, so they consciously erred on the side of safety. A slightly larger-diameter CM would have permitted better reentry L/D -- they simply didn't have enough *room* inside to offset the center of mass as much as they'd originally intended. The CSM size was fixed based on ideas about the diameter of Saturn upper stages which were obsolete almost as soon as the decision was made. The rounded corner arose likewise, but a sharp corner (like Mercury and Gemini) improves the aerodynamics substantially. CSM manufacturing and testing would have been greatly eased by a more Gemini-like design approach, with removable upper-heatshield panels, and equipment accessible from the outside rather than the inside. Apollo repeated many of Mercury's mistakes because its basic design was fixed before Gemini established that there was a better way. The SM engine was sized to lift the CSM off the lunar surface, because the mode decision wasn't final then. A redesign would have had a smaller engine, or possibly several still-smaller ones (removing the single point of failure). Serious consideration would have been given to solar arrays instead of fuel cells. Solar cells improved dramatically between the time when Apollo's basic design was fixed and the time when it started flying. (Soyuz, designed only a few years after Apollo, is solar-powered.) Similarly, serious consideration would have been given to LOX/LH2 propulsion for LOI and descent (although storable fuels might have been retained for ascent and return as a precaution). That's another technology which looked very raw and untrustworthy in 1961 but matured dramatically while Apollo was going from concept to flight. More resources would have been invested in making the computer bigger and faster, because software could replace other items of hardware. (Some of this happened during the Block I - Block II transition, and a redesign would have done more of it.) Braking rockets for land touchdown would have been reconsidered. Some work was done on them for Apollo, early on, and they have advantages. A copy of the Skylab toilet would have been fitted. (There was a plan to test it on Apollo 14, in fact, but Shepard vetoed it.) The Apollo baggies simply did not work terribly well, resulting in a lot of wasted time and less-than-ideal sanitation, especially when somebody was ill. The LM landing gear was another overdesigned piece of gear, thanks to uncertainties about both the lunar surface and the astronauts' ability to fly to a gentle touchdown. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
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