I'm not sure we reached a consensus vis-a-vis the full-length tank and the pre-burn.
Quote from: Robotbeat on 07/14/2010 10:31 pmI'm not sure we reached a consensus vis-a-vis the full-length tank and the pre-burn.Preburn is only an option, the rocket will take off in any case. The performance loss from the shrunk tank just does not add up to me.
Quote from: Downix on 07/14/2010 10:41 pmQuote from: Robotbeat on 07/14/2010 10:31 pmI'm not sure we reached a consensus vis-a-vis the full-length tank and the pre-burn.Preburn is only an option, the rocket will take off in any case. The performance loss from the shrunk tank just does not add up to me.Does it make sense to lengthen the tank, then?My point is that there's an optimization step that needs to be done, here. We shouldn't just ignore it. For the CCBs, yes, we are just going to live with whatever they're filled to, but the tank is undergoing such drastic changes that we really should consider what the optimal tank size would be.
We can discuss growth options as well in here, set a long distance goal, and figure out the steps to get there.The other thread had one discussion topic, how would AJAX impact EELV evolution.It helps to understand Atlas evolution:Phase I, new upper stage, called ACESPhase II switch to 5 m core with 2 RD-180.Phase III new 8.4m core.
Preburning will never be accepted. There is no such thing as a full length (or "unmodified") ET for this application. Both ends of the ET will be heavily modified, so make the right size.There is nothing to gained by keeping it the same length/volume as the shuttle. Don't touch the CCB's or don't preburn, you will lose support.Neither preburn nor partially filling of tanks are acceptable engineering solutions.
I hope someone can clarify this for me. The loads and the load paths for the ET have completely changed, even when compared to Jupiter. So I assume the ET/core is being completely redesigned and tested from top to bottom. OK, there may be a few parts reused from the Shuttle ET. But I guess I don't understand why changing the length is an issue unless it effects the CCBs.
Quote from: martin hegedus on 07/15/2010 04:26 amI hope someone can clarify this for me. The loads and the load paths for the ET have completely changed, even when compared to Jupiter. So I assume the ET/core is being completely redesigned and tested from top to bottom. OK, there may be a few parts reused from the Shuttle ET. But I guess I don't understand why changing the length is an issue unless it effects the CCBs.1. Its not a totall redesign. There are modifications but its not a brand new ET (like for example larger diameter).2. In theory length changes aren't a huge deal, but you have to watch out for preformance hits, fuel consumption issues (don't forget that 4th SSME), and ESPECIALLY changes to the load path ABOVE AND BEYOND the changes expected when going from the STS ET to the AJAX core.There are already load path changes, why add more?
A basic question. From what I understand from previous posts is that the CCB will need to be human rated. To do that Chuck said that a sensor package will need to be added to the RD180. Will the engine need to be modified for the addition of this package? Does this constitute a change to the CCB? Will any other sensors need to be added to the CCB for human rating, such as in the tank? Will any other changes need to be made to the CCB for human certification?
Quote from: martin hegedus on 07/15/2010 04:07 amA basic question. From what I understand from previous posts is that the CCB will need to be human rated. To do that Chuck said that a sensor package will need to be added to the RD180. Will the engine need to be modified for the addition of this package? Does this constitute a change to the CCB? Will any other sensors need to be added to the CCB for human rating, such as in the tank? Will any other changes need to be made to the CCB for human certification?Adding an Emergency Detection System is a change, but a planned change that ULA intends to add to all CCBs leaving the factory, so that there won't have to be different versions of the CCB for crewed vs unmanned launches.The details of what's required can be found in these two docs:http://www.ulalaunch.com/site/docs/publications/AtlasEmergencyDetectionSystem.pdfhttp://www.ulalaunch.com/site/docs/publications/HumanRatingAtlasVandDeltaIV.pdfNASA awarded ULA a $6.7 million Commercial Crew Development (CCDev) Program contract in February to start some basic design/definition work on the EDS for the Atlas and Delta.http://www.nasa.gov/centers/johnson/pdf/463224main_United%20Launch%20Alliance%20and%20Amendment.pdfOf course if an Atlas or AJAX is flown with a crewed-capsule, there will be the additional requirement of a LAS...for AJAX and Orion the sensible starting point would be OSC's work on the Ares I LAS.
Quote from: FinalFrontier on 07/15/2010 04:29 amQuote from: martin hegedus on 07/15/2010 04:26 amI hope someone can clarify this for me. The loads and the load paths for the ET have completely changed, even when compared to Jupiter. So I assume the ET/core is being completely redesigned and tested from top to bottom. OK, there may be a few parts reused from the Shuttle ET. But I guess I don't understand why changing the length is an issue unless it effects the CCBs.1. Its not a totall redesign. There are modifications but its not a brand new ET (like for example larger diameter).2. In theory length changes aren't a huge deal, but you have to watch out for preformance hits, fuel consumption issues (don't forget that 4th SSME), and ESPECIALLY changes to the load path ABOVE AND BEYOND the changes expected when going from the STS ET to the AJAX core.There are already load path changes, why add more? No disrespect, but I guess I disagree, in the sense that the design should be approached as a total redesign, even if the radius and some parts are reused. In my personal experience, it is under appreciating (for lack of better words) changes which cause failures. So I'm not sure how much time and money not changing the length of the core would save.