#11
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In article . com,
"kert" wrote: So why exactly is launching six astronauts in one vehicle better than launching three astronauts in two vehicles at the same time ? Since when has putting all eggs in one basket, or launcher in this case, become a wise practice ? I think the assumption is that one basket is dramatically cheaper than two. Whether that assumption is true, I don't know, though I can well imagine it might be. One way, you get economies of scale in the launcher itself, though the other way, you get some economies of scale in the launch rate. I can't guess which would dominate. ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#12
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Tom Cuddihy wrote:
kert wrote: So why exactly is launching six astronauts in one vehicle better than launching three astronauts in two vehicles at the same time ? Since when has putting all eggs in one basket, or launcher in this case, become a wise practice ? -kert Congress has made it pretty clear during the past two shuttle explosions that loss of astronaut life is NOT acceptable. If one of the two four person launches failed, ALL missions would be on hold. Just think about it. If you launch two three person crews to orbit, where they have to transfer to a 6-person lunar CEV, you need to have launched 3 vehicles to LEO just to get the crew in a CEV. IF each of the four person CXVs is 15 tons, and the lunar CEV is still 30 tons, you still have to launch 60 tons to LEO to get the passengers into a 30 ton CEV. If, on the other hand, you launch one 30 ton CEV, it can be launched from earth with all the passegers on board. Doesn't that make a lot more sense? 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 |
#13
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"Mike Chan" wrote in message
oups.com... Douglas Holmes wrote: "Jim Kingdon" wrote in message news There's one expected this afternoon. I assume this is the one: http://www.nasa.gov/home/hqnews/2005...ontractor.html In a nutshell, they picked two contractors to compete for a down-selection in 2006 (which is sooner than had been previously planned). Moving up the down-selection has been widely reported for some months now. Is that what was expected or is there more? The most interesting line for me was: NASA's Vision for Space Exploration calls for the CEV to carry up to six astronauts beyond low-Earth orbit soon after the Space Shuttle is retired in 2010, and then on to the moon as early as 2015. When did the CEV become a SIX man vehicle? Helps explain the size increase from 20 to 30 tons. Seems like it had gone to crew size of 4 back when it would be good if an EELV smaller than D-IVH can serve as the launcher. Now it seems it has gone to 6 so that even a D-IVH can't serve as the launcher. Not exactly. About a third of the weight is fuel. With only enough fuel for an ISS missions it would drop down to just over 20 tons. Which both can carry. With dual or quad rl-10s, depending on weight, both can also launch the larger version. |
#14
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Joe Strout wrote:
In article . com, "kert" wrote: So why exactly is launching six astronauts in one vehicle better than launching three astronauts in two vehicles at the same time ? Since when has putting all eggs in one basket, or launcher in this case, become a wise practice ? I think the assumption is that one basket is dramatically cheaper than two. Whether that assumption is true, I don't know, though I can well imagine it might be. One way, you get economies of scale in the launcher itself, though the other way, you get some economies of scale in the launch rate. I can't guess which would dominate. No, not only launch rate. With smaller vehicle you can (potentially) get flexibility, economic savings and redundancy in picking the launcher itself as well. IOW larger vehicle makes sense if you look at given vehicle/launcher combination in isolation, ignoring the existing launch market. -kert |
#15
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Douglas Holmes wrote:
The most interesting line for me was: then on to the moon as early as 2015. What's the latest on how the CEV crew is supposed to land on the moon, be sustained for however long they're going to stay doing whatever they're going to be doing, and get back to earth? |
#16
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kert wrote:
Joe Strout wrote: In article . com, "kert" wrote: So why exactly is launching six astronauts in one vehicle better than launching three astronauts in two vehicles at the same time ? Since when has putting all eggs in one basket, or launcher in this case, become a wise practice ? I think the assumption is that one basket is dramatically cheaper than two. Whether that assumption is true, I don't know, though I can well imagine it might be. One way, you get economies of scale in the launcher itself, though the other way, you get some economies of scale in the launch rate. I can't guess which would dominate. No, not only launch rate. With smaller vehicle you can (potentially) get flexibility, economic savings and redundancy in picking the launcher itself as well. IOW larger vehicle makes sense if you look at given vehicle/launcher combination in isolation, ignoring the existing launch market. -kert being able to put everthing up in one throw has been the the norm for the last several decades, during the end of the the gemini program the plan was to use several launches to get to the moon. if you used the gemini big transport 2 crew + 7 passengers, (16,000 kg + 4,000 kg launch escape tower) you would need the Delta iv (cost 140 mill '99) you would still have 4,000 kg of unused cargo to iss. if you where using the origianl gemini a crew of 2, (2,000 kg) using the same atlas v 401 (cost 77 mill '98) you would get 2 to iss and 10,000 kg of unused cargo to iss. while one would assume that with the gemini big the unused cargo mass could be stowed aboard, while with the original gemini, anouther modual would be required, possibly something simular to the shuttles extenetd duration or fuel pallets could make use of the extra avaliable launch mass. but that doesn't address the problems of where to park or transfer systems. if you where going to the moon then you need to fuel and resupply launches for the cev as well. a kg/dollar comaprison 4 - atlas v 401 - 48,000 kg - 308 million, just for boosters 2 - delta iv - 46,000 kg - 280 million, just for boosters |
#17
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In article .com,
Tom Cuddihy wrote: Personally, I do think that makes a lot of sense. With 4 people, it's tough to come up with a sustainable work/rest schedule. Why? Work 8 hours, relax/eat/etc. 8 hours, sleep 8 hours. Apollo had a crew of 3 because it was supposed to run three shifts. Very early, they figured out that this doesn't work in a modest-sized spacecraft. You want everybody sleeping at the same time. There's no particular reason *not* to put everybody on the same schedule. Unless you're doing something tricky like driving a pressurized rover nonstop over long distances, there's no particular need to have somebody 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 | |
#18
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Atlas 401 has a nice substitute called Proton, available via ILS. So
when there's a problem with one launcher, you can use another, from the same supplier. Dunno whether Proton would be any cheaper. Assuming it isnt, i'd say even paying that 10% extra is still reasonable price for such redundancy. -kert |
#19
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"Ed" wrote in message
oups.com... kert wrote: Joe Strout wrote: In article . com, "kert" wrote: So why exactly is launching six astronauts in one vehicle better than launching three astronauts in two vehicles at the same time ? Since when has putting all eggs in one basket, or launcher in this case, become a wise practice ? I think the assumption is that one basket is dramatically cheaper than two. Whether that assumption is true, I don't know, though I can well imagine it might be. One way, you get economies of scale in the launcher itself, though the other way, you get some economies of scale in the launch rate. I can't guess which would dominate. No, not only launch rate. With smaller vehicle you can (potentially) get flexibility, economic savings and redundancy in picking the launcher itself as well. IOW larger vehicle makes sense if you look at given vehicle/launcher combination in isolation, ignoring the existing launch market. -kert being able to put everthing up in one throw has been the the norm for the last several decades, during the end of the the gemini program the plan was to use several launches to get to the moon. if you used the gemini big transport 2 crew + 7 passengers, (16,000 kg + 4,000 kg launch escape tower) you would need the Delta iv (cost 140 mill '99) you would still have 4,000 kg of unused cargo to iss. if you where using the origianl gemini a crew of 2, (2,000 kg) using the same atlas v 401 (cost 77 mill '98) you would get 2 to iss and 10,000 kg of unused cargo to iss. while one would assume that with the gemini big the unused cargo mass could be stowed aboard, while with the original gemini, anouther modual would be required, possibly something simular to the shuttles extenetd duration or fuel pallets could make use of the extra avaliable launch mass. but that doesn't address the problems of where to park or transfer systems. if you where going to the moon then you need to fuel and resupply launches for the cev as well. a kg/dollar comaprison 4 - atlas v 401 - 48,000 kg - 308 million, just for boosters 2 - delta iv - 46,000 kg - 280 million, just for boosters 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. |
#20
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the price of the delta was if you where buying a dozen, the stated
price is 170 million for just one, so for occasional use you can move more mass for less with the single price quoted for the atlas. What is interesting is that the cev is supposed to have a 700 day life cycle, given that iss is suposed to last 20 years from launch. iss will be a destination for meny years to come, if the soyez is 60 mill plus the booster cost, it is less than the cost of the delta iv for transfering a couple of specialists. the 3 seat soyez at 7,000 kg would have 5,000 kg unused cargo on the atlas, i doubt that anyone could build a 2 seat gemini b (4,000 kg) for less than a soyez, and keep it up to the current crew volume demands of nasa. |
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