#141
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On Tue, 10 May 2005 11:46:28 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: But in the case of the Shuttle-derived one, we already have most of the cost covered in the development arena. A lot of it, but not "most," particularly if they go with an in-line design (which would make a lot more sense). It would be better- but the perfect is the enemy of the good enough; and the side cargo pod is a lot simpler from the design viewpoint. But sufficiently limited in its diameter as to make the thing probably unworthy of building (one of the reasons that Shuttle-C never happened). Nope. It's a new launch system, using existing propulsion elements. And this doesn't take into account the additonal (relative to using EELV) standing army needed to support it and its pads. It will still have heavy fixed annual costs, even if they're lower than Shuttle. Actually, it would be 2/3rds a stock shuttle stack, with the new motor/cargo pod stuck on the side- and yes, the long term costs are high, but this is something that can be done fairly quickly with things on hand. And they do seem to be in a rush about all this. Too much so, in my opinion. The only payloads that exist in sufficient volume to justify high flight rates of anything are humans. They're unlikely to go on a Chinese-made rocket, unless there's no domestic alternative. They don't generate much long term income for the companies that launch them, unlike a comsat. That remains to be seen. If they want to do Mars missions with their boosters, more power to them. It will bankrupt them to no useful purpose, just as Cheng He's treasure fleet did. What, pray tell, will be the difference if we do it with _our_ boosters? Nothing, actually, except that, unlike the Chinese, we can afford to waste money on such things. |
#142
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On Tue, 10 May 2005 11:34:02 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: Rand Simberg wrote: That's why it's important to build the infrastructure necessary to make it affordable to privately fund it. Heavy lift definitely doesn't do that. Flyin' to Mars ain't like dusting crops, boy! :-) Bill Gates could probably afford to finance the whole kit and kaboodle right now if he felt like it... but he hasn't done it yet. If he did, I'd hope that he'd be smart enough not to do it with heavy lifters. Elon Musk, who wants very much to go to Mars, seems to understand this... |
#143
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Herb Schaltegger wrote:
On Tue, 10 May 2005 13:53:14 -0500, Reed Snellenberger wrote (in article ): 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... If you only knew how many headaches the CBM's were to design from a mechanical and fluid/electrical standpoint! There are so many connectors that had to be run through the vestibules you wouldn't believe how hard it was to get them all to fit and still meet the various micro-g/on-orbit human factors design requirements. It's NOT simply a matter of "plug-in the module and let's go!" It's more like, "Plug in the module, pressurize the vestibule, draw a sample of the vestibule atmosphere to ensure nothing nasty got in there. Test the sample for several of the most likely nasties. Open the first hatch. Connect a whole hell of a lot of fluid and power/data jumpers, draw samples of the next module's own atmosphere. Test those samples for a much wider variety of nasties due to contamination, off-gassing and/or out-gassing. Open that hatch." Repeat this process for as many modules as necessary. If the modules are not internally pressurized, you'll have to design and implement a series of automated power/data/fluid connecting devices for each module. The more heavily instruments and interconnected you wish each module to be, the more complicated the interface mechanisms become and the more failure mechanisms there will be. I can believe that the CBMs were a design challenge (and a half). And I've read online copies of the checklists for connecting modules that went into the process in *excruciating* (and very interesting) detail. (incidentally, does anyone have a link to that again -- I think it used to be at spaceref.com, but it's been a while...) But the thing is... even if you're willing to endure the design & weight overhead of purely automated interconnects (with the liklihood that you'll need to have the excruciating procedure in your hip pocket for when the automated procedure craps out), you're still going to have to do all of those testing steps *anyway*. And once you're done -- you're done. I can't remember hearing about any problems with the CBM-based connection in the U.S. segments since they were installed. Of course, there are only two of the hard-connected CBM joints installed at this point (Node 1-Lab, Node 1-Airlock) -- I'm not counting the MPLM or PMA joints... -- Reed Snellenberger GPG KeyID: 5A978843 rsnellenberger-at-houston.rr.com |
#144
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On Tue, 10 May 2005 16:56:32 GMT, in a place far, far away, Reed
Snellenberger made the phosphor on my monitor glow in such a way as to indicate that: Rand Simberg wrote: 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. This also assumes that the partially-assembled craft can withstand an extended delay if a serious problem with the booster surfaces. That's not an assumption--it's a design requirement... Even if you plan to launch consumables at the very end of the assembly sequence, you need to provide for (for example) sufficient delta-v to provide for maintaining the assembly's orbit. At some point, an interplanetary craft being assembled orbitally needs to be considered a "self-propelled" space station, and manned accordingly. I've no problem with that. You don't think that a Mars ship will be "manned accordingly"? |
#145
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"Pat Flannery" wrote in message ... You are going to end up with a lot of launches if you try to do it with anything smaller than some of the proposed souped-up Delta IV heavy variants from the viewpoint of crew life support requirements alone. Seriously? The last time I remember looking into this, it took surprisingly little mass to keep a person alive for a day. In this article there is a chart for this: http://www.space.gc.ca/asc/eng/educa...system-edu.asp Their conclusion of nearly 25 kg per person per day is absolutely silly. They budget nearly 7 kg for clothes washing, but disposable clothes, as they use on ISS, would weigh less than washing clothes and reusing them. They also budget 13 kg for "urine flush". What's up with that? I seriously doubt you need that much water per day in order to vent urine out to vaccuum. If you take those silly values off, you're left with about 5 kg per person per day. You could sustain a crew of four for two years for about 15,000 kg. Since a Delta IV Heavy can loft 23,000 kg to LEO, you'd only need a single launch to get a cargo module containing your consumables into LEO. I'd hardly call that "a lot" and I hardly think it justifies a "souped-up Delta IV Heavy variant". Besides, consumables (O2, H2O, food, fuel, oxidizer, and etc), are easier to launch in smaller pieces than people. ;-) Seriously though, we really didn't need a rocket the size of Saturn V to get us to the moon if we'd adopted Earth Orbit Rendezvous instead of Lunar Orbit Rendezvous. Why would we need a launch vehicle approaching that size today? Jeff -- Remove icky phrase from email address to get a valid address. |
#146
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"Rand Simberg" wrote in message .. . On Tue, 10 May 2005 14:28:12 -0500, in a place far, far away, Herb Schaltegger made the phosphor on my monitor glow in such a way as to indicate that: If you only knew how many headaches the CBM's were to design from a mechanical and fluid/electrical standpoint! Yes, it's a shame that all of the effort/millions invested in this didn't go instead into decent EVA equipment. Unless we plan on exploring the Moon and Mars from inside the lander, you'd think that better EVA hardware would be a long term goal of the Moon/Mars program. Canceling the development of better space suits for the space station program, and then subsequently spending quite a bit of time, effort, and money trying to reduce EVA time, seems to have been a very short sighted decision. Jeff -- Remove icky phrase from email address to get a valid address. |
#147
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On Tue, 10 May 2005 18:36:47 -0500, Rand Simberg wrote
(in article ): On Tue, 10 May 2005 14:28:12 -0500, in a place far, far away, Herb Schaltegger made the phosphor on my monitor glow in such a way as to indicate that: On Tue, 10 May 2005 13:53:14 -0500, Reed Snellenberger wrote (in article ): 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... If you only knew how many headaches the CBM's were to design from a mechanical and fluid/electrical standpoint! Yes, it's a shame that all of the effort/millions invested in this didn't go instead into decent EVA equipment. Once again your one sentence reply ignores everything of substance. The CBMs were designed the way they were in response to a set of specific design requirements. Perhaps you don't realize that? Alternatively, you do realize that, and you realize as well that advanced EVA equipment was considered and then cut from separate portions of the budget, and you realize as well that the current EVA equipment is sufficient for most purposes, and you realize as well that the U.S./European/Japanese segments of ISS were designed for EVA assembly using current EVA equipment which works just fine for those purposes. Of course, that makes for a much less pithy one-sentence reply though, doesn't it? -- 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/ |
#148
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"Derek Lyons" wrote in message ... h (Rand Simberg) wrote: Assuming that the cheap booster is available in a reasonable time frame, and a complete second set of hardware is sitting around checked out and ready to go in a reasonable timeframe. You mean like how we had a *complete* backup Skylab along with a *complete* backup Saturn V? We also had backup CSM's and Saturn IB's for all of the Skylab missions and for ASTP. If you stop and think about it, having backup hardware isn't that expensive if you're talking about a *sustained* program where you're going to have many missions. The backup hardware for mission 1 just becomes the flight hardware for mission 2 and so forth and so on. If you accept that your last mission may fail, you don't need a backup for that mission at all. Now the question becomes, if you've got a launch success rate that's fixed at 95% or so, would you prefer to have more or less launches required for a mission? Now you need to know more, like do you really want to fly your missions on time? If so, what percentage of hardware loss can you absorb for a single mission and still expect to fly your next mission on time? Jeff -- Remove icky phrase from email address to get a valid address. |
#149
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On Tue, 10 May 2005 18:35:44 -0500, Rand Simberg wrote
(in article ): On Tue, 10 May 2005 14:30:42 -0500, in a place far, far away, Herb Schaltegger made the phosphor on my monitor glow in such a way as to indicate that: 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. I'm referring to Shuttle-C, not Orbiter. And if you'd actually read my post you'd see that your typically snarky one-liner is a non sequitur. You're bitching that Shuttle-C is volume limited, just like an STS orbiter No, I'm pointing out that Shuttle-C is volume limited, *unlike* an STS orbiter. Go back and re-read your own posts. You're not making any sense. and I'm pointing out that Station modules have been mass-limited, not volume limited so your argument that Shuttle-C is deficient due to volume limits is irrelevant. It would seem that your argument is the one that's irrelevant. The point is that Shuttle-C would not have reduced the number of assembly flights enough to make it worth the money, which (one more time) is why it wasn't built. No, *I* stated it wasn't built due to money, in response to your comment that volume limitations (irrelevant volume limits, by the way) were a main reason (which they were not). -- 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/ |
#150
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"Pat Flannery" wrote in message ... Rand Simberg wrote: 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. After the amount of time it would take to get to Mars and back is considered, getting that close and not landing would be pathetic. Tell that to the crews of Apollo 8 and Apollo 10. Jeff -- Remove icky phrase from email address to get a valid address. |
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