#121
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On Tue, 10 May 2005 12:45:08 -0500, Reed Snellenberger wrote
(in article ): The assembly of the Mars ship wouldn't be all that different than the ISS assembly process, when you think about it. Actually, you would hope very much that it would require less EVA assembly and ideally none. The need for EVA on ISS is the result of a number of design decisions that hopefully will not be repeated for an interplanetary spacecraft as opposed to an LEO station. -- Herb Schaltegger, GPG Key ID: BBF6FC1C "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." - Benjamin Franklin, 1759 http://www.individual-i.com/ |
#122
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"Frank Scrooby" wrote:
[ an updated Apollo] The design is already proven, just update the parts you can't get anymore or know you can safely replace with something better. The problem is... The design you propose *isn't* already proven beyond the aerodynamics. You are going to end up replacing virtually every interior component, which means you incur the (very non trivial) costs of testing, qualification, and integration. You'll have to re-do virtually all of the interior structure, which will also have to be designed and verified. I know reviving a 40 year old design is not as sexy (and probably not as lucrative) as designing and building a new vehicle, The problem is... You aren't reviving an old design. In practice you are designing a totally new vehicle that happens to have the same moldline. Maybe NASA should get its money back if its contractors fail to perform ;-). Isn't that the way it works in the REAL WORLD. Only if you define 'real world' to exclude 'activities that do occur in the real world, and are high risk, high payoff'. Get ISS (and NASA) and alternative, safe and expandable crew and cargo delivery system and then start thinking about how to extend it's usefulness to lunar missions. Thats a sure and certain way to make the craft *more* expensive, not less. D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#123
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#124
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On Tue, 10 May 2005 16:08:10 -0500, Rand Simberg wrote
(in article ): It came down to value for the money. Shuttle-C was constrained to the same diameter as the Orbiter payload bay, and pretty much the same volume (though I think that the payload could have been eighty feet, instead of sixty). That meant that it would save very few assembly flights to SSF, and waste much of its lift capacity because it was volume rather than mass limited. Actually, you're incorrect about this. Few if any of the U.S./European/Japanese segment for ISS have been truly volume limited. They've all been mass-limited, especially at the inclination chosen for ISS. The U.S. modules were reduced in length from 40 racks to 24 and even then they had to be launched on semi-outfitted. These decisions were made well before the change to the ISS orbital inclination. Had Shuttle-C and OTV been available, fully-outfitted 40-rack modules could have been launched to the "proper" SSF inclination, saving many logistical and operational headaches, not the least of which have been the UF flights necessary to outfit the modules after launch. Breaking out of this constraint would have meant major mods to the RSS and LC-39, which were verboten because it had to continue to support Shuttle flights. That was why it never happened. See above. -- Herb Schaltegger, GPG Key ID: BBF6FC1C "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." - Benjamin Franklin, 1759 http://www.individual-i.com/ |
#125
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Pat Flannery wrote:
The lifting body design gives the vehicle great cross range, which is said to be in the interests of safety, and to avoid water landings. Given the present administration's desire for military space control, one can wonder if the great cross range requirement had a similar origin to that of the Shuttle's, with its delta wings- something the military wants for a military derivative of the CEV. Presumably the designers lack your propensity to see a conspiracy around every corner and an equal propensity to blame every ill on the current administration. Equally presumably they have done what many have not - studied the Shuttle's operations and noted the flexibility that a wider cross range allows in landing windows and abort opportunities. Admitting the last requires many space enthusiasts to think outside of the box - and to admit to themselves three things that are Heresy to every Right Thinking space enthusiast; 1) That the military requirements may have provided (whatever the cost) a useful capability. 2) That the dinosaurs have actually thought about what makes a spacecraft useful. And 3) we can learn something from the Shuttle other than "two legs bad, four legs good". D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#126
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Pat Flannery wrote:
Rand Simberg wrote: Or subcool the propellants and insulate the tanks properly... Still, how long would one have to get it all stuck together? Days or weeks? The Soviet's did a stage (Block D) that used an insulation sunshade for it LOX/Kerosene propellant on Proton-Zond and N-1: http://www.myspacemuseum.com/l1s_2.jpg But do we have any experience with this sort of thing? The closest we came was the canceled Shuttle boosted Centaur stage. Of course... we shouldn't try *anything* we don't have experience with. We might depart from the One True Path as shown by the mighty Apollo, blessed be His Name. D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#127
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#128
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On Tue, 10 May 2005 10:27:06 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: Not if a replacement part can go up on another cheap (something that heavy lift will never be at planned usage rates) ) launch. There's an old saying about eggs and baskets... I was concerned about the cost of the parts themselves- which could be more than the rocket that carries them. Could be, but it's still better than losing an entire mission with a single loss, and you can pay for a lot of lost pieces with the development cost savings for the unneeded HLLV. The big problem is needing replacements for ones that may get lost during launch. With our unmanned planetary missions we have many times used dual spacecraft in case one was lost for some reason. If you have to build a complete back-up modular Mars ship that will be expensive; the other concern is the launch window- can you get the replacement component for the lost one up and docked while the launch window is still open? If you put enough slack in the schedule. If not, launch windows to Mars occur relatively frequently. This discussion presupposes much more routine capability to get things into orbit (as well as doing orbital assembly) than we have today. Developing that kind of capability would have much greater long-term value for our prospects in space than a heavy lifter. |
#129
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On Tue, 10 May 2005 10:36:58 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: Of course you should have backups for all the parts. It's not like you're only going to go once. To Mars? With all that entails? There'll be a very long time interval between the first manned flight for the prestige factor and the second one...for whatever reason it is done. If it's going to be flags and footprints, as you imply, then we shouldn't do it at all. It would be nutty to go to Mars at all if only a flight or two is intended. Remember the Bush administration suggested a manned flyby flight of Mars with no manned landing- which is about the nuttiest, most pointless thing I ever heard suggested in the field of spaceflight outside of the Soviet Voskhod test EVA by a dog. :-) Not necessarily. It's a lot easier to do a mission to Phobos for an initial mission than it is to land on the planet, and a lot of good science could still result. |
#130
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Herb Schaltegger wrote:
On Tue, 10 May 2005 12:45:08 -0500, Reed Snellenberger wrote (in article ): The assembly of the Mars ship wouldn't be all that different than the ISS assembly process, when you think about it. Actually, you would hope very much that it would require less EVA assembly and ideally none. The need for EVA on ISS is the result of a number of design decisions that hopefully will not be repeated for an interplanetary spacecraft as opposed to an LEO station. I've actually been pleasantly surprised at how little EVA work has been required for the station (apart from the truss components, which are unlikely to be used in a ship). The CBM design seems to have worked out very well... Since they won't be going up in the Shuttle, it will be a lot simpler to pre-install the armor & EVA handholds on the ground. I imagine the biggest demand for EVAs during the trip would be to change out the (inevitable) interstellar solar wind, gas, & micrometeorite experiments... -- Reed Snellenberger GPG KeyID: 5A978843 rsnellenberger-at-houston.rr.com |
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