#21
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ruzicka wrote:
It'll be interesting to see if those cost numbers stay the same or change, once (if) the United Launch Alliance merges the two launch vehicle lines into one company. Since the 1990s, the reported price of an EELV launch has increased by roughly 50%. (So that a Delta IV Heavy probably costs $220-250 million now, etc). The new Alliance hopes to save perhaps $100 million per year. With a projected launch rate of eight per year and an average per-launch cost of, say, $120 million each, a $100 million cut in costs would result in a 10% price drop - if the Alliance partners decided to pass the savings on to their customer(s). But the ugly truth is that the partners have lost billions launching these new rockets, so the cost savings will probably go toward bottom-line repair rather than toward launch price cuts. - Ed Kyle |
#22
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Henry Vanderbilt wrote:
Another possibility: For longer missions, launch two four-man CEV's with three aboard each, dock them to each other in orbit, then operate them as a dual-redundant unit with a bit of extra elbow room. Which eliminates the need to fly a six-man CEV with attendant new larger-than-EELV-heavy booster every time you rotate Station crew. (Might as well still be flying Shuttle; it'll end up costing about as much per flight.) Henry Sounds easy, simple and efficient, but ignores some practicalities of CEV design. IF you go with a standard capsule shape, that means the docking mechanism is going to end up at the bow of the capsule, as every 'docking' capsule so far launched has done. Have you heard of a design that does not do a bow-forward docking? with the exception of a winged shape like lockheed's that would clearly not be intebded for lunar or other than LEO travel, I just don't see it. Now you have two small capsules docked end-to-end, with heatshields on either end. There's no reasonable way to dock to anything else that allows personnel access, like a space station, a lunar orbiter, an L-1 station, or, most importantly for the near term, a lunar lander. You've created a dead-end system, useful for transport of 4 or 8 personnel. And not much else, unless you're willing to go to ISS-type gigantic modular vehicle assembly. Perhaps that's possible if you're willing to ignore the architecture of the 'Constellation' program that's been put forward to this point, or if you're willing to limit yourself to 4 people. I just don't see that happening, and obviously now neither does Mike Griffen. Tom |
#23
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Henry Spencer wrote:
awake at all times. Given modern technology, there's no need to have somebody sitting there watching gauges -- computers do that better than humans -- and if there *is* some reason for continuous equipment monitoring, at least on the Moon, it can be done from Earth. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | I'll take the point about no need for gauge watchers, but my point about redundancy during EVAs on lunar or other planetary surfaces stands. In addition, the point about long duration, far away missions being different than the method of Apollo or ISS. Also, six people allows for better division of skills. |
#24
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Tom Cuddihy wrote:
Henry Vanderbilt wrote: Another possibility: For longer missions, launch two four-man CEV's with three aboard each, dock them to each other in orbit, then operate them as a dual-redundant unit with a bit of extra elbow room. Which eliminates the need to fly a six-man CEV with attendant new larger-than-EELV-heavy booster every time you rotate Station crew. (Might as well still be flying Shuttle; it'll end up costing about as much per flight.) Henry Sounds easy, simple and efficient, but ignores some practicalities of CEV design. IF you go with a standard capsule shape, that means the docking mechanism is going to end up at the bow of the capsule, as every 'docking' capsule so far launched has done. Have you heard of a design that does not do a bow-forward docking? with the exception of a winged shape like lockheed's that would clearly not be intebded for lunar or other than LEO travel, I just don't see it. Hmm. Didn't they look at a Gemini design with a hatch through the heatshield? Regardless, nose-first docking is hardly a law of nature - look at how Shuttle docks, for instance. Now you have two small capsules docked end-to-end, with heatshields on either end. There's no reasonable way to dock to anything else that allows personnel access, like a space station, a lunar orbiter, an L-1 station, or, most importantly for the near term, a lunar lander. You've created a dead-end system, useful for transport of 4 or 8 personnel. And not much else, unless you're willing to go to ISS-type gigantic modular vehicle assembly. You can prove anything impossible if allowed to burden it with arbitrary assumptions. You can design to dock nose-to-nose, side-to side, back-to-back should you so choose - you're starting with a clean sheet of paper. You can also carry a small multi-port docking adapter for longer/more complex missions and put together arbitrarily complex clusters - look at Mir in its later days. There seems to be an institutional terror of orbital assembly at NASA, but as the other Henry points out, they'll need to do it sooner or later, so it might as well be sooner and save considerable money on big new booster developments. Perhaps that's possible if you're willing to ignore the architecture of the 'Constellation' program that's been put forward to this point, or if you're willing to limit yourself to 4 people. I just don't see that happening, and obviously now neither does Mike Griffen. Ah, now we're wandering from "what's possible and makes sense" to "what might Mike Griffin do given his constraints". I'm not trying to guess what he might do yet - he's shown himself willing to deep-six some of his constraints already. I'm just pointing out some of the benefits of not assuming "the approach so far" is the only possible way. We'll see soon enough what NASA actually goes for. Meanwhile, this is more nested-quotes than I usually do. Ta! Henry Vanderbilt |
#25
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Henry Vanderbilt wrote:
Hmm. Didn't they look at a Gemini design with a hatch through the heatshield? Regardless, nose-first docking is hardly a law of nature - look at how Shuttle docks, for instance. No, but if you do other than nose-first docking you're now loking at a bigger heatsheild and thus a bigger vehicle because the heat shield has to protect the docking mechanism, which if it's going to fit people through comfortably, and probably at a minimum in a spacesuit, requires at least a meter wide hatch. You can prove anything impossible if allowed to burden it with arbitrary assumptions. You can design to dock nose-to-nose, side-to side, back-to-back should you so choose - you're starting with a clean sheet of paper. You can also carry a small multi-port docking adapter for longer/more complex missions and put together arbitrarily complex clusters - look at Mir in its later days. Can you design such a thing as a small, multi-port docking adapter? Now you're talking about lofting a Unity node along with the CEV. That's exactly the parasitic type of mass you want to avoid. There seems to be an institutional terror of orbital assembly at NASA, but as the other Henry points out, they'll need to do it sooner or later, so it might as well be sooner and save considerable money on big new booster developments. Why will NASA need to do it sooner or later? That sounds suspiciously like the reasoning used to fund ISS, "to develop technologies required..." yuck. Perhaps that's possible if you're willing to ignore the architecture of the 'Constellation' program that's been put forward to this point, or if you're willing to limit yourself to 4 people. I just don't see that happening, and obviously now neither does Mike Griffen. Ah, now we're wandering from "what's possible and makes sense" to "what might Mike Griffin do given his constraints". I'm not trying to guess what he might do yet - he's shown himself willing to deep-six some of his constraints already. I'm just pointing out some of the benefits of not assuming "the approach so far" is the only possible way. We'll see soon enough what NASA actually goes for. Henry Vanderbilt True. |
#26
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In article .com,
Tom Cuddihy wrote: Another possibility: For longer missions, launch two four-man CEV's with three aboard each, dock them to each other in orbit, then operate them as a dual-redundant unit with a bit of extra elbow room... Sounds easy, simple and efficient, but ignores some practicalities of CEV design. IF you go with a standard capsule shape, that means the docking mechanism is going to end up at the bow of the capsule, as every 'docking' capsule so far launched has done. Have you heard of a design that does not do a bow-forward docking? Su the Russian TKS -- qualified for manned flight but never flown manned because its program got canceled -- had a pressurized service module, reached via a heatshield hatch, with a docking assembly on the rear. (TKS is gone, but its service module lives on: the Mir add-ons, and the Zarya module which started ISS, were derivatives of it.) Now you have two small capsules docked end-to-end, with heatshields on either end. There's no reasonable way to dock to anything else that allows personnel access, like a space station, a lunar orbiter... Sure there is: put it in the *middle*. Docking the two capsules doesn't weld them together. To dock them to something else, separate them and have them dock separately. (Assuming, that is, that you'd even bother docking them together if they were then going to dock to something else.) Alternatively, one of them goes up with an extra component tucked underneath for launch (like ASTP's docking module): a lightweight multi-port docking hub. Not a big heavy expensive module, mind you, just a simple light shell with several docking ports. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#27
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In article .com,
Tom Cuddihy wrote: ...if you do other than nose-first docking you're now loking at a bigger heatsheild and thus a bigger vehicle because the heat shield has to protect the docking mechanism... Bear in mind that bigger doesn't necessarily mean heavier. Heatshield mass scales very strongly with the *mass* of the capsule, but almost not at all with its *size*. If you need a capsule with enough room inside for a docking assembly, it's no big deal, if you can restrain yourself from filling any further empty space with more equipment. The only real limitation is that a capsule substantially bigger than the top diameter of the launcher is a headache. (A *little* bigger is fine; "hammerhead" payload fairings, mildly wider than the launcher top, are common.) By the way, *why* does the docking mechanism have to go inside the heatshield? TKS's didn't. For that matter, Soyuz's doesn't (it's on the orbital module, not the reentry module). which if it's going to fit people through comfortably, and probably at a minimum in a spacesuit, requires at least a meter wide hatch. What *have* you been drinking? The Apollo CM/LM tunnel was about 75cm in diameter, and was passable to a suited astronaut (as witness Dave Scott's stand-up EVA in the LM docking hatch on Apollo 15). Can you design such a thing as a small, multi-port docking adapter? Now you're talking about lofting a Unity node along with the CEV. Hardly. The ASTP docking module -- only two ports, but with a *lot* more equipment than you'd need for this -- weighed only 2t fully loaded. There seems to be an institutional terror of orbital assembly at NASA, but as the other Henry points out, they'll need to do it sooner or later, so it might as well be sooner... Why will NASA need to do it sooner or later? Because we're not talking about a one-shot program here. The missions will get bigger. They will outgrow *any* fixed-size launcher eventually; the only question is when. Either you keep developing newer and bigger launchers every few years -- which is very expensive, since you don't really recover your investment on launcher N before starting on N+1 -- or you start using orbital assembly at some point. And once you concede that *eventually* you will need orbital assembly, it becomes clear that the sooner you start, the better. Note that even Apollo used orbital assembly, in a small way. Why the paranoid fear of it? -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#28
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"Henry Vanderbilt" wrote in message
... Hmm. Didn't they look at a Gemini design with a hatch through the heatshield? Regardless, nose-first docking is hardly a law of nature - look at how Shuttle docks, for instance. Actually, the USAF re-flew a Gemini capsule that they had modified to this design. It was launched on top of a "boilerplate" MOL and performed a successful re-entry. In the USAF Museum in Dayton, OH, you can see a Blue Gemini on display (unflown) with the same hatch in the heat shield design. Note also that the Russians (then Soviets), flew their TKS capsule with a similar hatch in the heat shield. Although this design was never flown manned, I believe that there weren't any problems with the hatch in the heat shield during test flights. There are also several hatches in the bottom of the shuttle's heat shield. Most notable are the three large ones for the landing gear and two smaller ones which go over the connections to the ET (i.e. the 17" diameter LOX and LH2 lines). Failure of any of these hatches would very likely mean another Columbia like disaster. So while hatches in the heat shield may not be a designer's first choice, the technology has existed since the Gemini days to make this work. Jeff -- Remove icky phrase from email address to get a valid address. .. |
#29
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"Henry Spencer" wrote in message
... What *have* you been drinking? The Apollo CM/LM tunnel was about 75cm in diameter, and was passable to a suited astronaut (as witness Dave Scott's stand-up EVA in the LM docking hatch on Apollo 15). Interesting. I don't remember ever reading about this, but a quick web search confirms that this was indeed done in order to take pictures of the site: http://www.fukuoka-edu.ac.jp/~kanami...15.htm#standup Can you design such a thing as a small, multi-port docking adapter? Now you're talking about lofting a Unity node along with the CEV. Hardly. The ASTP docking module -- only two ports, but with a *lot* more equipment than you'd need for this -- weighed only 2t fully loaded. Indeed. The ASTP docking module contained quite a bit of equipment, including O2 and N2 tanks mounted outside its pressure vessel. This was due to the different pressures and gas mixtures used by Soyuz and Apollo. However, if you're docking two spacecraft with sea level pressure adn gas mixtures (as is used today by Soyuz, the shuttle, and ISS), then you don't need all of this equipment. Here's a couple of links to information on the ASTP docking module, if anyone is interested: http://www.astronautix.com/craft/apoodule.htm http://www.hq.nasa.gov/office/pao/Hi...apol_soyuz.htm Jeff -- Remove icky phrase from email address to get a valid address. .. |
#30
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In article ,
Jeff Findley wrote: ...The Apollo CM/LM tunnel was about 75cm in diameter, and was passable to a suited astronaut (as witness Dave Scott's stand-up EVA in the LM docking hatch on Apollo 15). Interesting. I don't remember ever reading about this, but a quick web search confirms that this was indeed done in order to take pictures of the site: http://www.fukuoka-edu.ac.jp/~kanami...15.htm#standup It was Scott's idea, based on the geology training: when you arrive at a new site, the first thing you do is find a high spot and take a look around. In addition to the photography, it let him pick out a good spot for the ALSEP, and confirm that there wasn't going to be a problem with driving in certain areas which had originally been considered doubtful. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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