Quote from: marsavian on 06/24/2009 09:44 pmNone of the ESAS TLI claims have proved accurate including Ares V which has had to be enlarged considerably from the SSME Classic to what they have now and it still comes up short so you can't rely on ESAS. Ares V classic wasn't dumped because of a performance deficit (it probably would have worked pretty well), it was dumped on a supposed cost of engine basis. So, NASA picked less efficient engines, and then wondered why making Ares V bigger and bigger wasn't having the desired effect... it didn't help any that upgrades to the RS-68 weren't hitting their performance targets (per Ross statements), or that the core stage was too heavy for the crawlerway.
None of the ESAS TLI claims have proved accurate including Ares V which has had to be enlarged considerably from the SSME Classic to what they have now and it still comes up short so you can't rely on ESAS.
Quote from: marsavian on 06/24/2009 09:44 pmI don't know for sure what the real (as opposed to supposed) motivation was for dumping Space Shuttle Main Engines, Space Shuttle External Tanks (or at least very close approximations), and Space Shuttle SRBs from vehicles that were supposed to be Space Shuttle derived, but replacing them with unbuilt (hence needed development), untested (hence unknown performance), and unproven (hence unknown reliability) hardware sure has made the whole process a lot more complicatedQuoted for truth. Perhaps that post should have been mailed to the Augustine Commission
I don't know for sure what the real (as opposed to supposed) motivation was for dumping Space Shuttle Main Engines, Space Shuttle External Tanks (or at least very close approximations), and Space Shuttle SRBs from vehicles that were supposed to be Space Shuttle derived, but replacing them with unbuilt (hence needed development), untested (hence unknown performance), and unproven (hence unknown reliability) hardware sure has made the whole process a lot more complicated
That's a pretty concise summary of the situation. As I've argued before, RS-68 and J-2X are disappointing engines whose development has come at the cost of fielding much more promising engines such as RS-84 and RL-60. Delta IV will probably be the first and last vehicle to use RS-68, and J-2X (aka Vulcain reinvented for the NIH-afflicted) will probably never fly.
I agree. But until this data is made public, or at least shows itself in some documented form, there is no way to alert the panel. Telling them you heard water-cooler talk that NASA did another review of Direct is not going to help. You need to have the documents from NASA and the ESAS documents right there to show them side by side, and ask where the missing 15 tons went.
Quote from: marsavian on 06/24/2009 09:44 pmNone of the ESAS TLI claims have proved accurate including Ares V which has had to be enlarged considerably from the SSME Classic to what they have now and it still comes up short so you can't rely on ESAS. Ares V classic wasn't dumped because of a performance deficit (it probably would have worked pretty well), it was dumped on a supposed cost of engine basis. So, NASA picked less efficient engines, and then wondered why making Ares V bigger and bigger wasn't having the desired effect... it didn't help any that upgrades to the RS-68 weren't hitting their performance targets (per Ross statements), or that the core stage was too heavy for the crawlerway.Ares I on the other hand, was dumped because the upper stage engine supposedly couldn't be made to air start, so they picked a less efficient engine, made the first stage bigger, and wondered why making the thing bigger wasn't having the desired effect... it didn't help any that the J-2X design was having a hard time hitting its performance targets (again, per Ross' statements), or that the first stage was too long to avoid resonance with the upper stage.I don't know for sure what the real (as opposed to supposed) motivation was for dumping Space Shuttle Main Engines, Space Shuttle External Tanks (or at least very close approximations), and Space Shuttle SRBs from vehicles that were supposed to be Space Shuttle derived, but replacing them with unbuilt (hence needed development), untested (hence unknown performance), and unproven (hence unknown reliability) hardware sure has made the whole process a lot more complicated
And I think NASA is sorta coming to their senses on this. Shannon stated in his presentation that making the SSME expendable was not as bad as they first thought. I believe he went as far to say that it was just a "myth" that the SSME was too expensive to just throw away. It is good that Direct came to this conclusion a bit earlier than NASA. So far Ares V is sticking with the RS-68, but I could see that changing if the panel is going to stick with the current plan.
It was because it couldn't deliver a 45mT lander.p13-14http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070002798_2007001569.pdf
Edit: I just made such a chart; see attached (page 2). Don't look too closely at the ISPs; Merlin and SSME have relatively poor vacuum ISP because as first-stage engines they are optimized for sea-level ISP. The fuels aren't shown explicitly on the chart but the ISP indicates the fuel.
Which reminds me -- I just heard that NASA has gone and produced a new "Analysis" into DIRECT 3.0 in which the same old BS is apparently doing the rounds -- yet again.While I've only heard a few details, they're b*tching about the pmf being something which NASA is unable to build (yeah, we know that, which is precisely why we want Industry to handle that element because of their much greater experience instead, duh!).
Quote from: kraisee on 06/24/2009 09:19 pmWhich reminds me -- I just heard that NASA has gone and produced a new "Analysis" into DIRECT 3.0 in which the same old BS is apparently doing the rounds -- yet again.While I've only heard a few details, they're b*tching about the pmf being something which NASA is unable to build (yeah, we know that, which is precisely why we want Industry to handle that element because of their much greater experience instead, duh!).Ross, I honestly do admire you Chuck and the rest of the team for putting up with this for around 3 years now. In order to have an honest comparision of the benefits of each system its necessary to come to a simple agreement that yes DIRECT (a 2-launch architerure) can do the same job as the Ares 1.5 launch architecture. Maybe a 2-launch architecture will cost more than the DIRECT team says, maybe Ares I is theoretically safer, or maybe we really do need a monster cargo launch vehicle for Mars and other missions. However, as long as NASA management can reduce this to a my expert said vs their expert said (and by the way who is their expert) they can essentially freeze the conversation in place and avoid doing the really important comparisions or asking the important questions about what is the most effective way to return to the moon and push mankinds presence further into space.Don't give up the fight, it should be self evident to anyone who has looked at the all of the various shuttle derived architectures proposed over the years that an SDLVs are excellent for launching payloads ranging from 50 mt to around 130 mt without too much in the way of extensive rengineering of the basic components, and Jupiter or something very similiar to it can launch 110 mt like the team claims and ergo send the required mass through TLI. The fact that NASA upper management seems so intent on dismissing the obvious just shows that they really do understand how weak their claims are that Ares is the safest, simplest, least costly, quickest and best way to meet the nations stated exploration goals, and that if the firewall is breached there will simply be no way to justify Ares based on the really important questions dealing with the cost and performance of potential exploration architectures.PS Although I am basically just a civil/environmental engineer, and not an aerospace or rocket guy by any stretch of the word I can say I do admire NASA a great deal and if not for Apollo and the Shuttle would have probably have pursued a career in accounting something else just as dreadfull. I just have a problem when a leaderships collective pride in their solution blinds them from allowing an honest assesment of that solution or alternatives.John
Cool stuff, thanks for the chart. If I may make a humble suggestion though, change the specific impulse scale to 250-500, maybe in major increments of 15, minor of 5 to give it more fidelity. I would also add the RL-10A-4-2 and J-2X.
Quote from: kraisee on 06/24/2009 09:19 pmWhich reminds me -- I just heard that NASA has gone and produced a new "Analysis" into DIRECT 3.0 in which the same old BS is apparently doing the rounds -- yet again.While I've only heard a few details, they're b*tching about the pmf being something which NASA is unable to build (yeah, we know that, which is precisely why we want Industry to handle that element because of their much greater experience instead, duh!).That seems pretty weak. If rebuttals of Direct are no longer about performance, safety or cost, I think they're out of ideas. If that's all they have, they're just dragging their heels, and I would lose a lot of faith in the Augustine Commission if they didn't see that.We can't get that built, or we *won't* get that built. Seems pretty subjective to me.
Quote from: cixelsyD on 06/25/2009 02:27 amQuote from: kraisee on 06/24/2009 09:19 pmduh!).subjective to me....isn't that what they told those two guys from Ohio who had that crazy flying machine idea?
Quote from: kraisee on 06/24/2009 09:19 pmduh!).subjective to me.
duh!).
It really seems like a DIRECT/ULA alliance would be the best way to counter NASA's FUD about upper stage pmf.The alliance should propose a common upper stage (5m Centaur with 45 mT GLOW) to be used on Atlas/Delta (expended after ascent) and Jupiter (fueled EDS).With this common upper stage as the EDS, J-130 puts a 25 mT spacecraft through TLI. With L2 rendezvous, both CEV and LSAM are less than 25 mT through TLI.ULA needs a new upper stage to get the most out of their existing first stages. DIRECT needs a new upper stage to get out of earth orbit. NASA can't develop these upper stages, but ULA can.So tell ULA that if NASA chooses DIRECT for lunar missions, they'll get funding to develop the 5m Centaur they've been wanting, but they need to convince NASA that it doesn't violate the laws of physics.
Which reminds me -- I just heard that NASA has gone and produced a new "Analysis" into DIRECT 3.0 in which the same old BS is apparently doing the rounds -- yet again.While I've only heard a few details, they're b*tching about the pmf being something which NASA is unable to build (yeah, we know that, which is precisely why we want Industry to handle that element because of their much greater experience instead, duh!).And they're trying to depict the architecture as only being able to send a 29mT lander through TLI.