There are no reasonable alternatives for this vehicle except an air-start SSME.This thread should be in the Ares-I section.Ross.
For it's stated mission (seems to be short on payload even for that), but I'm curious: What does 5seg + ACES-41 do? Or could it manage ACES-71? I'm not suggesting it's a good idea, just wondering.
Quote from: William Barton on 10/27/2009 10:23 amFor it's stated mission (seems to be short on payload even for that), but I'm curious: What does 5seg + ACES-41 do? Or could it manage ACES-71? I'm not suggesting it's a good idea, just wondering.It drops into the Ocean somewhere short of the European/African coastline because it doesn't have *close* to the necessary thrust required to get it into orbit from the point where that first stage places it (in velocity/altitude terms).Also, ACES-41 is lighter, so the First Stage acceleration and Max-Q would get significantly worse too.J-2X is actually underpowered for this configuration and in order to pick up correct acceleration levels after FS jettison, you would require 12 RL-10B-2's to match its thrust levels.Ross.
Hmmm... Perhaps using an SRB as a first stage in an inline rocket is not such a great idea, if it places such extreme requirements on the 2nd stage.If only this could have been predicted.
Quote from: Lars_J on 10/27/2009 03:46 pmHmmm... Perhaps using an SRB as a first stage in an inline rocket is not such a great idea, if it places such extreme requirements on the 2nd stage.If only this could have been predicted. I know, if only someone had made mention of it sooner, and prepared a complete, well thought out program that could stand on it's own to replace this concept....
Non-starter. The gravity losses from carrying RP1 instead of LH2 would be huge.
The astonishment of seeing "real" Constellation hardware on the launch pad, imediately balanced by "wow, this thing is sure ugly.
Quote from: Archibald on 10/27/2009 04:05 pmThe astonishment of seeing "real" Constellation hardware on the launch pad, imediately balanced by "wow, this thing is sure ugly.Beauty is in the eye of the beholder. - Ed Kyle
Quote from: edkyle99 on 10/27/2009 04:24 pmQuote from: Archibald on 10/27/2009 04:05 pmThe astonishment of seeing "real" Constellation hardware on the launch pad, imediately balanced by "wow, this thing is sure ugly.Beauty is in the eye of the beholder. - Ed KyleOr not. Behold: "The Corndog."
Quote from: Antares on 10/27/2009 03:35 pmNon-starter. The gravity losses from carrying RP1 instead of LH2 would be huge.1) The original ATK inline concepts included a J-2S powered LH2 upper stage able to lift 16-18 tonnes to LEO and a kerosene upper stage loaded with 113 tonnes of propellant able to lift 13 tonnes to LEO, both on top of 4-segment boosters.2) would not be able to lift as much mass to orbit as Ares I.
Quote from: edkyle99 on 10/27/2009 04:18 pmQuote from: Antares on 10/27/2009 03:35 pmNon-starter. The gravity losses from carrying RP1 instead of LH2 would be huge.1) The original ATK inline concepts included a J-2S powered LH2 upper stage able to lift 16-18 tonnes to LEO and a kerosene upper stage loaded with 113 tonnes of propellant able to lift 13 tonnes to LEO, both on top of 4-segment boosters.1) And look at how well the performance predictions of subsequent ATK inline concepts have turned out
Quote from: Antares on 10/27/2009 03:35 pmNon-starter. The gravity losses from carrying RP1 instead of LH2 would be huge.1) The original ATK inline concepts included a J-2S powered LH2 upper stage able to lift 16-18 tonnes to LEO and a kerosene upper stage loaded with 113 tonnes of propellant able to lift 13 tonnes to LEO, both on top of 4-segment boosters.
Quote from: Antares on 10/27/2009 08:27 pm1) And look at how well the performance predictions of subsequent ATK inline concepts have turned outNot bad, actually. Subsequent studies showed that a four-segment booster topped by a J-2S powered second stage would have been able to lift *more* than 18 tonnes - as much as 20-ish tonnes - to the CEV insertion orbit.
1) And look at how well the performance predictions of subsequent ATK inline concepts have turned out
Quote from: edkyle99 on 10/27/2009 08:59 pmQuote from: Antares on 10/27/2009 08:27 pm1) And look at how well the performance predictions of subsequent ATK inline concepts have turned outNot bad, actually. Subsequent studies showed that a four-segment booster topped by a J-2S powered second stage would have been able to lift *more* than 18 tonnes - as much as 20-ish tonnes - to the CEV insertion orbit.I really wish you had a badge, Ed, so we could dispense with these arguments.
Expensive yes Im sure, but more expensive than all the subsequent 5 segment / J2-X teeth gnashing?
But even the original "stick" still had the SSME airstarted second stage, right? So while the concept may have looked simple back then, the whole 2nd stage should have seemed problematic from the beginning...
I hope this isn't too naive a question but here goes:Are there any parallel staged upperstages?If something like the stick or direct is still suffering from considerable gravity losses on the second stage, is there any reason why this couldn't be improved in the same way that boosters on parallel staged first stage help fight gravity losses and reduce the size of the sustainer engines.Why isn't this technique also used for second-stages and upperstages?
Quote from: gin455res on 10/28/2009 12:12 pmI hope this isn't too naive a question but here goes:Are there any parallel staged upperstages?If something like the stick or direct is still suffering from considerable gravity losses on the second stage, is there any reason why this couldn't be improved in the same way that boosters on parallel staged first stage help fight gravity losses and reduce the size of the sustainer engines.Why isn't this technique also used for second-stages and upperstages?Yes, there have been parallel, or cluster, upper stages. The first U.S. satellite, Explorer 1, was boosted to orbit by a spinning cluster of relatively small solid rocket motors.For a liquid upper stage, the easier approach would be to add another engine. Alternative Crew Launch Vehicle designs with upper stages powered by two J-2S engines were studied during ESAS. The designs allowed much more second stage propellant, which increased LEO payload by 2 to 4 tonnes. - Ed Kyle