#41
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On Mon, 09 May 2005 13:17:46 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: Also if we go over to a unmanned system, we don't have to meet the stringent requirements for SRB safety, so we can probably reuse more SRB segments. So we don't care if we lose a billion-dollar payload? Or the price of relaunching? This notion of reliability being of no relevance for unmanned systems gets tiresome. |
#42
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On Mon, 09 May 2005 14:49:40 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: Or subcool the propellants and insulate the tanks properly... Still, how long would one have to get it all stuck together? Days or weeks? Months, by some analyses. 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? Not that I'm aware of, at least operationally, but there's been a lot of technology development in this area. The closest we came was the canceled Shuttle boosted Centaur stage. Which wasn't designed for long-duration storage. |
#43
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On Mon, 09 May 2005 15:09:50 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in such a way as to indicate that: If we actually intend to do a manned Mars mission we are going to need a heavy lift vehicle of some sort, Many believe this. That doesn't render it a fact. |
#44
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On Mon, 09 May 2005 15:00:31 -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: So we don't care if we lose a billion-dollar payload? Or the price of relaunching? This notion of reliability being of no relevance for unmanned systems gets tiresome. Not to the same degree... for a manned launch you want around 99+% reliability if at all possible; for unmanned you can settle for 95%-97% (like most operational expendable rockets have) and realize that the loss of a couple in 100 launches will be more than offset by the money you save in not having to design and build to quite the high standards required to get to 99+%. It's where those last few percentage points start coming into play that you run into lots of added dollars- and extra equipment weight to overbuild things to make critical things redundant. Which cuts into your payload weight, and therefore ups your launch price per pound for large numbers of launches. That's an interesting theoretical argument, but in practice, what do you think that Thiokol would do differently in manufacturing a motor for an unmanned launch that they do for a manned one? |
#45
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On Mon, 9 May 2005 11:41:59 -0400, in a place far, far away, "Scott
Hedrick" made the phosphor on my monitor glow in such a way as to indicate that: "Henry Spencer" wrote in message ... Generally speaking, you cannot get a truly low-cost process by paring bits off a high-cost one. It ought to be a good way to use any leftover tanks and SRBs, rather than using them as museum pieces. Only if the development costs don't swamp any potential cost savings... I don't see how spending the money to develop a new vehicle that can only be flown a few times because it's using up a finite amount of leftover parts can make any kind of sense. |
#46
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Pat Flannery wrote: Ed Kyle wrote: (An aside - I once watched a hydrogen fire burning on Pad 39A after an abort. The flames licked right up the side of the orbiter (Discovery I think it was - with crew on board and ET fueled) discoloring the exterior. It burned for awhile and was more than a little uncomfortable to watch). Does anyone have more info on this incident? It was STS-41D (first flight of Discovery) on June 26, 1984, after an "RSLS" abort. Crew was: Henry W. Hartsfield, Jr., Commander Michael L. Coats, Pilot Judith A. Resnik, Mission Specialist 1 Steven A. Hawley, Mission Specialist 2 Richard M. Mullane, Mission Specialist 3 Charles D. Walker, Payload Specialist 1 Discovery didn't get off the ground until September. Here is a link with a description. The fire burned for 20 minutes! "http://yarchive.net/space/shuttle/launch_abort.html" - Ed Kyle |
#47
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Phil Fraering wrote: On Mon, 09 May 2005 11:53:20 -0700, Ed Kyle wrote: ...Both Delta IV and Atlas V have the same problems when it comes to CEV adaptation. Neither can handle a projected 20 ton CEV without core booster augmentation, (solid or liquid strap-on boosters). But NASA is either going to have to live with this or go shuttle-derived. I don't see the U.S. government (at least not the current one) coming up with the billions it will take to develop a new, more powerful core rocket just to launch CEV a few times a year. - Ed Kyle This is my second try at posting this. To me this brings to mind another question: Does the CEV need to be twenty tons? Soyuz was designed in the 60's and weighs seven metric tons. Kliper, proposed as a Soyuz replacement, but able to carry up to six, is projected to weigh 13-15 tons, but its propulsion system will not be recovered (Lockheed has proposed to make the CEV hardware recoverable). NASA has listed the maximum liftoff mass of CEV, including escape systems and fairings that would not go into orbit, to be 20 tons. CEV doesn't have to weigh that much, of course. - Ed Kyle |
#48
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" wrote in
message ups.com... the DIV has to fly an odd trajectory (due to structural concerns) that means that there are points in the ascent when abort is *not* survivable. Is that bad? Seems to me that it happens to STS as well. |
#49
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On Mon, 9 May 2005 16:55:21 -0500, Phil Fraering wrote
(in article ): I think at one point in the mid-90's we were discussing this here, and it came up that over the decade previous to then, the space insurance industry had gone bankrupt. TWICE. Before you start feeling too bad for any segment of the insurance industry, realize that there's something called "reinsurance" and it's there for just such an eventuality. If the "space insurance industry" (*) has "gone bankrupt" (**) it's because they weren't charging high enough premiums to cover their losses and couldn't make up the shortfall in the financial markets. (*) There's no such animal; they major world insurers are all arms, tentacles and pseudopods of a handfull of multinational conglomerates. (**) "Bankrupt" is not the right term for the financial services industry, at least not how it's commonly used in everyday speech. Typically, insurance concerns which have liabilities exceeding assets go into "receivership." -- 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/ |
#50
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Pat Flannery wrote:
The problem here is that you need a minimum of four EELV launches to land a man on the Moon if the LockMart design is chosen: If they put people on the moon again, I'll bet some of them will be women. cue debate about extra costs involved in providing more privacy than was available to Apollo crew -- Semper in faecibus sumus, sole profunditas quae variat. |
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