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"Heavy lift: examining the requirements"
Taylor Dinerman's article in "The Space Review" this morning raised some
questions for me. 1) It did not appear that the question of infrastructure support was addressed in the article - only the need for heavy lift. A shuttle derived heavy lift vehicle keeps getting mentioned, but the part that seems to be ignored is the cost of the supporting workforce, maintaining productions lines, etc. I haven't yet seen any plausible situation requiring an HLV to be launched at regular and frequent intervals that might justify the need for an HLV. Am I missing something? 2) The idea of using an SRB for a CEV launcher was gently dismissed in the article with the argument that the SRBs are inherently less safe than liquid boosters. Having fired successfully 225 out of 226 times, and with the single failure (SRB burnthrough) being an abortable failure in the CEV (possibly even an ATO?), I'd suggest that the SRB has earned some respect. Regardless, the heavy lift forms of the Delta and Atlas that were mentioned also use SRBs, no? Multiple ones? Now, which launcher might be more reliable? Jon |
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"Rand Simberg" wrote in message
The issue with solids on a manned vehicle isn't the reliability so much as the ability to shut them down in an abort. Yes, but that's the case with all of the strap-ons used by Atlas and Delta, isn't it? That is, none of them can be shut down. So, what makes a Heavy Atlas or Delta better than an SRB on that account? Jon |
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Rand Simberg wrote:
Heavy Delta doesn't use solids. According to AvWeek (2/21) (_not_ referring to the Delta IV Heavy, here): "Any Medium launcher options for CEV would, however, have to be equipped with more solid rocket boosters than have been flight tested on either the new Atlas or Delta vehicles. For example, the Atlas V 551/552 medium vehicle with five solids or the Delta IV Medium with six would be needed to satisfy the minimum performance required to launch the 20-metric-ton CEV." Also, the graphic accompanying the AvWeek article, and copied in Dinerman's TSR article, the heaviest lift versions of the Delta IV heavy _appear_ to feature strap-on solid boosters. The point I was trying to make addressed this paragraph in his article: "While the SRBs have had a pretty good safety record since the Challenger disaster, they are still inherently less safe than a liquid-fueled, and thus controllable, rocket. It has been proposed for both the Delta 4 Medium and for the SRB-derived CEV launch systems that they have an escape tower similar to the ones used on the Mercury, Gemini, and Apollo capsules. Such a tower will, in any case, be a part of any baseline CEV design. A manned system deserves a more robust, multilayered set of safeguards." I'm not quite sure I agree with his initial statement above that the SRBs have (merely) a "pretty good safety record since" Challenger - they have _all_ achieved mission targets. [I also wonder if there are ways to effectively terminate thrust in an appropriate way should the need arise in an abort.] Considering that (according to the original article in TSR about SRBs used for a CEV launcher) the concept has the support of some in the astronaut office, and that strap-on SRBs would be used anyway to supplement an Atlas or Delta Medium launcher for CEV (according to AvWeek, above), I feel that Dinerman shouldn't have blown off the concept so casually. Again: which one is safer, a single STS SRB as a first stage, or a Delta IV or Atlas Medium with several strap-on SRBs? Jon |
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March 7, 2005
Another laughable op-ed from Space Review. There is only one credible heavy lift launch vehicle architecture : seven SSMEs on a straight stack, with the cryogenic tank going to orbit with a second stage, and the engine module returning to the vicinity of the launch site in once around near SSTO. Anything else is folly. Thomas Lee Elifritz http://elifritz.members.atlantic.net |
#5
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On Mon, 7 Mar 2005 07:29:16 -0600, in a place far, far away, "Jon S.
Berndt" jsb.at.hal-pc-dot.org made the phosphor on my monitor glow in such a way as to indicate that: 2) The idea of using an SRB for a CEV launcher was gently dismissed in the article with the argument that the SRBs are inherently less safe than liquid boosters. Having fired successfully 225 out of 226 times, and with the single failure (SRB burnthrough) being an abortable failure in the CEV (possibly even an ATO?), I'd suggest that the SRB has earned some respect. Regardless, the heavy lift forms of the Delta and Atlas that were mentioned also use SRBs, no? Multiple ones? Now, which launcher might be more reliable? Atlas yes, Delta no. I don't believe that the Atlas solids are multi-segment, but I'm not sure. The issue with solids on a manned vehicle isn't the reliability so much as the ability to shut them down in an abort. |
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On Mon, 7 Mar 2005 08:32:08 -0600, in a place far, far away, "Jon S.
Berndt" jsb.at.hal-pc-dot.org made the phosphor on my monitor glow in such a way as to indicate that: "Rand Simberg" wrote in message The issue with solids on a manned vehicle isn't the reliability so much as the ability to shut them down in an abort. Yes, but that's the case with all of the strap-ons used by Atlas and Delta, isn't it? That is, none of them can be shut down. So, what makes a Heavy Atlas or Delta better than an SRB on that account? Heavy Delta doesn't use solids. As to Atlas, that's going to become an issue if it's to be used as a CEV launcher. |
#7
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On 7 Mar 2005 08:22:38 -0800, in a place far, far away, "Jon S.
Berndt" made the phosphor on my monitor glow in such a way as to indicate that: Again: which one is safer, a single STS SRB as a first stage, or a Delta IV or Atlas Medium with several strap-on SRBs? Probably the former, though they're both terrible launchers for putting people into orbit. |
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Jon S. Berndt wrote:
... Considering that (according to the original article in TSR about SRBs used for a CEV launcher) the concept has the support of some in the astronaut office, and that strap-on SRBs would be used anyway to supplement an Atlas or Delta Medium launcher for CEV (according to AvWeek, above), I feel that Dinerman shouldn't have blown off the concept so casually. The overall reliability record is good for solid boosters, but when they've gone, they've gone nasty in a hurry. I'm thinking of the Titan 34D in 1986, of a Titan 4 in the early 90s, and of the Delta II during the late 90s and a Delta during the late 70s. These all ended in big detonations. That is why incorporating them into manned launchers is so difficult. Again: which one is safer, a single STS SRB as a first stage, or a Delta IV or Atlas Medium with several strap-on SRBs? Single SRB is statistically more reliable. But is it safer? Probably. On the other hand, an argument can be made that neither SRB or EELV with solids would be safer than an all-liquid system. The problem with this editorial is that it starts out arguing for a new heavy-lifter, but ends up talking about whether solid boosters should be used for manned launches. It would have been better to keep the two topics separate. Few will argue that solids shouldn't be used for unmanned, heavy-lift launchers. That discussion is about how big heavy-lifters should be - or whether they're needed at all. The solids-for-humans question is an entirely different problem. The astronaut office is going to have a say in this one. Right now, if sounds like the majority is saying "no". It could be that we already have the heavy launcher (EELV Heavy - just augmenting a little can get it up to 30 tons to LEO) but that a new or derived all-liquid Medium is needed to boost the 20 ton-ish CEV. It could be a matter of adding a second RS-68 or RD-180 to the EELV boosters. - Ed Kyle |
#9
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Jon S. Berndt wrote:
Taylor Dinerman's article in "The Space Review" this morning raised some questions for me. ... I'd suggest that the SRB has earned some respect. Regardless, the heavy lift forms of the Delta and Atlas that were mentioned also use SRBs, no? Multiple ones? Now, which launcher might be more reliable? In addition to the flight safety issues that make solids a bigger challenge for human launches, there is a perhaps more important ground safety issue. Accidents on the ground have killed far more people than have died in space missions. The presence of "live" SRBs in the VAB has added cost to the shuttle program due to safety limitations, for example. A worst-case fear has long been the unlikely-but-not- impossible case of an SRB lighting up within the VAB during processing. - Ed Kyle |
#10
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"Rand Simberg" wrote in message .. . On Mon, 7 Mar 2005 07:29:16 -0600, in a place far, far away, "Jon S. Berndt" jsb.at.hal-pc-dot.org made the phosphor on my monitor glow in such a way as to indicate that: 2) The idea of using an SRB for a CEV launcher was gently dismissed in the article with the argument that the SRBs are inherently less safe than liquid boosters. Having fired successfully 225 out of 226 times, and with the single failure (SRB burnthrough) being an abortable failure in the CEV (possibly even an ATO?), I'd suggest that the SRB has earned some respect. Regardless, the heavy lift forms of the Delta and Atlas that were mentioned also use SRBs, no? Multiple ones? Now, which launcher might be more reliable? Atlas yes, Delta no. I don't believe that the Atlas solids are multi-segment, but I'm not sure. The issue with solids on a manned vehicle isn't the reliability so much as the ability to shut them down in an abort. Atlas V SRB's are not segmented and have fixed nozzles. Murray Anderson |
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