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#21
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![]() Jorge R. Frank wrote: [...] And therein lies the rub: we will never progress to the point where we can "do" wings unless we build more vehicles *with* wings. Well, we can do that with X-43-like programs -- send up some 6 meter models, and UAV them back to the ground, and count how many pieces you get. Meantime, capsules can be used for transport and to help evolve the internal systems (e.g., LSS, RCS, exo-atmospheric guidance software, Bose-Einstein Consendate Gyros, ...). I will be interested in seeing what Mr Rutan comes up with. Ray Schmitt and Kim Keller have indicated that some recent progress in TPS might make a small winged vehicle easier. We'll see. You can be sure that the sexiness of winged vehicles will keep people trying to do it until it can be done well, even if it isn't a continuous development line. /dps |
#22
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On 2005-04-27, Jorge R. Frank wrote:
"Jeff Findley" wrote in : Actually, this is easier to do than you think. The ET is very nearly in orbit when the shuttle releases it. If you redesign the system so that the ET and orbiter are one vehicle, then you get a *far* less dense vehicle for reentry, which reduces heating loads *considerably*. This also eliminates the shedding foam problem. It does introduce other problems, of course. With stubby wings and a fuselage mostly consisting of empty tanks, such a vehicle would be much more difficult to land in any kind of crosswind. That in turn greatly restricts landing opportunities. That was considered a much more serious problem in the 70s due to lack of maturity of fly-by-wire control, but even today it's not a clear tradeoff. The Shuttle is also small enough to be shipped by air; anything which was significantly larger would pose greater problems as far as shipping from alternate landing sites to the launch site goes. Not really a killer, but a logistical headache if you want to keep up a good flight rate. A rough guess says a week or two shipment time for an orbiter too large to be flown. Of course, such a beast would be more likely to have been designed to have flight capacity under its own power, which renders this a bit moot... -- -Andrew Gray |
#24
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![]() "Jorge R. Frank" wrote in message ... "Jeff Findley" wrote in : Actually, this is easier to do than you think. The ET is very nearly in orbit when the shuttle releases it. If you redesign the system so that the ET and orbiter are one vehicle, then you get a *far* less dense vehicle for reentry, which reduces heating loads *considerably*. This also eliminates the shedding foam problem. It does introduce other problems, of course. With stubby wings and a fuselage mostly consisting of empty tanks, such a vehicle would be much more difficult to land in any kind of crosswind. That in turn greatly restricts landing opportunities. That was considered a much more serious problem in the 70s due to lack of maturity of fly-by-wire control, but even today it's not a clear tradeoff. True, it does introduce problems in crosswinds, if you assume you're restricted to winged vehicles. Personally, given the success with all but one of the DC-X landings (which failed due to a ground processing error on a prototype vehicle which lacked redundancy), I'd consider using a powered vertical landing. With a vertically landing vehicle, you can deal with crosswinds in a fundamentally different way. Note that large helicopters deal with crosswinds in a different way than large fixed wing aircraft. The shuttle runway at KSC is 15,000 feet long by 300 feet wide (not counting the asphalt overruns and shoulders). If you made this circular (for a VTVL vehicle), you'd have a circular landing pad with a diameter of about 2400 feet. That seems like a pretty big landing area for a vertical lander. In an emergency, you can put down a vertical lander on just about any firm, flat surface and not have it tip over. Landing an empty VTVL vehicle on water in an emergency, where you accept the fact that is going to tip over and possibly damage the vehicle, may be survivable for the crew. It's got to be more survivable than landing a shuttle orbiter on water with something heavy in the payload bay (like an MPLM). Jeff -- Remove icky phrase from email address to get a valid address. |
#25
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![]() "Andrew Gray" wrote in message . .. The Shuttle is also small enough to be shipped by air; anything which was significantly larger would pose greater problems as far as shipping from alternate landing sites to the launch site goes. Not really a killer, but a logistical headache if you want to keep up a good flight rate. A rough guess says a week or two shipment time for an orbiter too large to be flown. Of course, such a beast would be more likely to have been designed to have flight capacity under its own power, which renders this a bit moot... Reusable VTVL vehicles could be designed to have a self ferry capability. Jeff -- Remove icky phrase from email address to get a valid address. |
#26
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![]() "Jorge R. Frank" wrote in message ... "snidely" wrote in oups.com: But note that the problems with capsules are due to *details* of the design, and many critics of the Shuttle claim that some important problems it has are due to the *fundamanetals* of the design (wings, complicated SSMEs, big solids). I would argue that Soyuz 1 was not a "detail"; parachutes are pretty fundamental to almost all capsule designs. Also the Soyuz where the OM didn't detach properly. And I believe there was a separate incident where it began its reentry nose down, exposing the least protected face to the heat of re-entry. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
#27
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"snidely" wrote:
Derek Lyons wrote: [...] Two out of six (?) Soyuz-TMA flights have now had significant problems. There have been no calls for investigations, no musings on the problems the Soviets may be having with training, software developments, or QA. Prima facie evidence that the all-singing mentality is deeply ingrained. Well, I call for Soyuz investigations just as often as I call for Shuttle investigations, so I'm entirely consistent. Not in these groups you don't. (Not unless you are JimO or rk posting under another name.) Also, there is a self-selection process in these news groups, in that the majority of readers are from the US, with a large population of other "western" countries (including Australia). This means that we don't have a large population of Hallerski's and Doeski's to provide the negative voice. Utter bull****. That the majority of the posters are 'western' does nothing to prevent a proper and open eyed examination of the history of Soyuz. It's equally bull**** that bBo and Doe provide anything other than noise. We do, however, have Jim Oberg's insights, and we have spent a lot of time discussing the problems with programs that used capsules (usually in s.s.h). We've spent a lot of time discussing the details of the problems. We've spent zero time discussing the implications of those problems. I lean to a capsule these days not because I think capsules are perfect, or because I am deluded they have a flawless record. I don't think they are as beautiful as the Shuttle, and they certainly don't do much (in any design I can refer to) for handling downmass. My vote switched because wings make reentry a hard problem. Once we have progressed to where we can do wings and still have a good reentry solution, then I expect the new designs to reflect that, and for us to be able to do more than we can now. And how exactly do we progress to 'doing wings and having a reentry solution' unless we *do wings in the first place*? D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#28
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"Jeff Findley" wrote:
I lean to a capsule these days not because I think capsules are perfect, or because I am deluded they have a flawless record. I don't think they are as beautiful as the Shuttle, and they certainly don't do much (in any design I can refer to) for handling downmass. My vote switched because wings make reentry a hard problem. Once we have progressed to where we can do wings and still have a good reentry solution, then I expect the new designs to reflect that, and for us to be able to do more than we can now. Actually, this is easier to do than you think. The ET is very nearly in orbit when the shuttle releases it. If you redesign the system so that the ET and orbiter are one vehicle, then you get a *far* less dense vehicle for reentry, which reduces heating loads *considerably*. You also get a vehicle with much higher parasitic loads due to the large amounts of structure required. You also have problems caused by the fact that the acreage of TPS is far greater, even if it can be less robust. NASA dropped the all in one for some very good reasons. This also eliminates the shedding foam problem. As does moving the insulation internal to the tank. D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#29
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"Jeff Findley" wrote:
Personally, given the success with all but one of the DC-X landings (which failed due to a ground processing error on a prototype vehicle which lacked redundancy), I'd consider using a powered vertical landing. With a vertically landing vehicle, you can deal with crosswinds in a fundamentally different way. Note that large helicopters deal with crosswinds in a different way than large fixed wing aircraft. Ask any architect who has worked on skyscrapers on the problems wind causes. It's not an easy problem. In an emergency, you can put down a vertical lander on just about any firm, flat surface and not have it tip over. ROTFLMAO. So long as it's firm, flat, and heavily reinforced. Otherwise, it cracks under the weight. Landing an empty VTVL vehicle on water in an emergency, where you accept the fact that is going to tip over and possibly damage the vehicle, may be survivable for the crew. It's got to be more survivable than landing a shuttle orbiter on water with something heavy in the payload bay (like an MPLM). 'Got to be more survivable'? Try figuring the loads the cabin will take after falling 200 feet. Try figuring the weight that will be required to brace against this. (Of course all my criticisms are based on the likely size of a vehicle with a useful payload.) D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#30
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![]() "Derek Lyons" wrote in message ... "Jeff Findley" wrote: This also eliminates the shedding foam problem. As does moving the insulation internal to the tank. Which results in an increased mass for the ET because the aluminum alloy used (like most metals) gets stronger as you lower the temperature. Also, you'd better make sure that you don't have internal shedding of insulation, since your SSME turbopumps surely wouldn't fare well if they started ingesting chunks of foam. Jeff -- Remove icky phrase from email address to get a valid address. |
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