kraisee - 17/4/2006 9:38 PMQuoteedkyle99 - 17/4/2006 9:59 PMWhat about a crew launcher sized for a 25 tonne to LEO payload (mass injected into LEO) powered by only 3 RS-68s with a J-2X upper stage? 430 tonnes of propellant in an ET-diameter, but shorter-than-ET, Stage 1 with a 490 tonne gross. 90 tonnes propellant in Stage 2 with a 100 tonne gross. Or so. (Maybe Stage 2 works as a TLI stage in a bigger launcher.) The whole deal weighs about 620 tonnes at liftoff with a 1.44 T/W ratio. - Ed KyleCost for developing a whole new large-scale first stage is prohibative.There is a sound reason for trying this with the core of CaLV due to cost savings, but not to develop a whole new stage.Ross.
edkyle99 - 17/4/2006 9:59 PMWhat about a crew launcher sized for a 25 tonne to LEO payload (mass injected into LEO) powered by only 3 RS-68s with a J-2X upper stage? 430 tonnes of propellant in an ET-diameter, but shorter-than-ET, Stage 1 with a 490 tonne gross. 90 tonnes propellant in Stage 2 with a 100 tonne gross. Or so. (Maybe Stage 2 works as a TLI stage in a bigger launcher.) The whole deal weighs about 620 tonnes at liftoff with a 1.44 T/W ratio. - Ed Kyle
kraisee - 18/4/2006 3:07 AMAnd the 3-RS-68 engine'd version Ed mentions is basically just a Delta-IV Heavy in a slightly different "package".It certainly wouldn't be able to loft an EDS stage, so you'd have to use something like the current D-IV Heavy upper stage and man-rate it - so at that point why not just use the Heavy as it is and save yourself a lot of extra costs duplicating it all over again.Probably should mention that it isn't anywhere near as safe as the CLV either...Ross.
edkyle99 - 18/4/2006 1:17 PMAs for safety, the ESAS report listed the LOC probability of the ET-based designs to be nearly 1/1000 - about 15-20 times safer than the current U.S. human launch system, though only half as safe as the CLV. But do any of us really believe those numbers?
BogoMIPS - 18/4/2006 2:44 PMQuoteedkyle99 - 18/4/2006 1:17 PMAs for safety, the ESAS report listed the LOC probability of the ET-based designs to be nearly 1/1000 - about 15-20 times safer than the current U.S. human launch system, though only half as safe as the CLV. But do any of us really believe those numbers? Given the different ways that a liquid rocket can fail catastrophically compared to a solid rocket, I think the safety numbers of a purely-solid first stage are not unreasonable. Whether they are truly 1/1600 or whatever, who knows, but with a proper escape system, it does look a heckuvalot safer than a liquid first stage.
edkyle99 - 18/4/2006 2:17 PMAs for safety, the ESAS report listed the LOC probability of the ET-based designs to be nearly 1/1000 - about 15-20 times safer than the current U.S. human launch system, though only half as safe as the CLV. But do any of us really believe those numbers? - Ed Kyle
kraisee - 18/4/2006 4:07 PMI can't find any hard-fact data on a direct comparison between solid and liquid rocket engine reliability.I assume the ESAS figures are all based on some fact-based analysis from somewhere. It certainly seems to indicate that the SRB's are significantly less likely to fail than comparable liquid engined first stages, but I have personally never seen any analysis which offers conclusions one way or the other.Without hard-data, we're actually all just reduced to making guesses on here. I'd like to have some real facts to work with instead of just the usual supposition.So, does anyone out there have real hard data on comparing these things accurately which can be released for us to all examine?Ross.
kraisee - 18/4/2006 1:07 PMI can't find any hard-fact data on a direct comparison between solid and liquid rocket engine reliability.I assume the ESAS figures are all based on some fact-based analysis from somewhere. It certainly seems to indicate that the SRB's are significantly less likely to fail than comparable liquid engined first stages, but I have personally never seen any analysis which offers conclusions one way or the other.Without hard-data, we're actually all just reduced to making guesses on here. I'd like to have some real facts to work with instead of just the usual supposition.So, does anyone out there have real hard data on comparing these things accurately which can be released for us to all examine?Ross.
kraisee - 18/4/2006 3:07 PMI can't find any hard-fact data on a direct comparison between solid and liquid rocket engine reliability.I assume the ESAS figures are all based on some fact-based analysis from somewhere. It certainly seems to indicate that the SRB's are significantly less likely to fail than comparable liquid engined first stages, but I have personally never seen any analysis which offers conclusions one way or the other.Without hard-data, we're actually all just reduced to making guesses on here. I'd like to have some real facts to work with instead of just the usual supposition.So, does anyone out there have real hard data on comparing these things accurately which can be released for us to all examine?Ross.
gladiator1332 - 18/4/2006 7:04 PMDo solids have a history of exploding?I belive the reason why many question the solid first stage is the memory of Challenger. That is something that NASA will have to constantly face, I can't remember a Shuttle launch where I haven't let out a sigh of relief after the SRBs fall away. Even though the cause of Challenger was fixed, the SRBs are still thought of as dangerous.
BogoMIPS - 18/4/2006 9:44 PMThe two Titan 34D failures you cite are both cases where an SRM failure was alongside a liquid rocket. The strap-on SRM failures you cite are along the same lines as well. Once the solid's failure causes the liquid rocket to fail, you've got both explosions happening, so limiting analysis to one seems tough.Any good resources on the 'net about the 34D-9 failure? I'd like to learn more about this, so I'm not talking out my exhaust nozzle right now. ;)As long as we don't start looking at sticking the CEV atop the CaLV, the comparison of these systems to CLV, to me, doesn't seem 100% fair. I will agree that solid motors can fail spectacularly, just as liquids can. The question is how likely will that be, and how survivable is it when it happens?I need to do some more research on failures of launches with of linear (i.e. no strap-on/parallel engines), solid-only first stages. I haven't done enough reading to be sure, but other than ICBMs, I can't think of many other systems that have used that configuration previously.
BogoMIPS - 18/4/2006 8:44 PMThe two Titan 34D failures you cite are both cases where an SRM failure was alongside a liquid rocket. The strap-on SRM failures you cite are along the same lines as well. Once the solid's failure causes the liquid rocket to fail, you've got both explosions happening, so limiting analysis to one seems tough.Any good resources on the 'net about the 34D-9 failure? I'd like to learn more about this, so I'm not talking out my exhaust nozzle right now. As long as we don't start looking at sticking the CEV atop the CaLV, the comparison of these systems to CLV, to me, doesn't seem 100% fair. I will agree that solid motors can fail spectacularly, just as liquids can. The question is how likely will that be, and how survivable is it when it happens?I need to do some more research on failures of launches with of linear (i.e. no strap-on/parallel engines), solid-only first stages. I haven't done enough reading to be sure, but other than ICBMs, I can't think of many other systems that have used that configuration previously.
kraisee - 20/4/2006 3:16 PMWhat were the actual causes for the two failures you mention?Specifically, are the Shuttle SRB's susceptible to similar failures due to common/similar designs?Ross.
kraisee - 20/4/2006 2:16 PMWhat were the actual causes for the two failures you mention?Specifically, are the Shuttle SRB's susceptible to similar failures due to common/similar designs?Ross.