Quote from: kraisee on 06/01/2009 03:05 pmAnd no, the LOX tank is sized to precisely the same capacity as the current ET's Ogive tank.We do still have an option to increase the capacity of both the LOX and LH2 tanks by ~7-9% (in the same way as NLS was going to), but right now, mostly for simplicity sake, we have simply chosen not to mess around with altering the capacities. We can close all performance requirements comfortably without it.I find it sad if the easy tankage structure changes that give lots of performace per kg of structure are not done when the hard ones are done. Why design a long engine thrust structure when you can elongate the LH2 tank and design a smaller thrust structure? What is the additional design work with making the LOX barrel section a little longer when you anyway redesign the tank for inline launch?The only engineering reason for not doing this that I can think of is if you add to much tankage mass and no longer hit the sweet spot for the 3 SSME verison.I find the political reason weak, who cares if the fuel load is aprox 8% larger when it looks the same on the pretty pictures? If you are that sensitive about looks you ought to have made the thrust structure design more expensive buy having two versions to center the mid engine. That would of course be a bad redesign from a system cost perspective.Starting out in the "high end" of the tankage volume and mass sweet spot ought to be beneficial for future engine upgrades of the SSME:s or SRB:s.
And no, the LOX tank is sized to precisely the same capacity as the current ET's Ogive tank.We do still have an option to increase the capacity of both the LOX and LH2 tanks by ~7-9% (in the same way as NLS was going to), but right now, mostly for simplicity sake, we have simply chosen not to mess around with altering the capacities. We can close all performance requirements comfortably without it.
Quote from: OV-106 on 06/02/2009 06:13 pmIt'll be 30 years in April 2011, not 40. I knew I should've taken off my shoes before attempting that calculation...
It'll be 30 years in April 2011, not 40.
what % thrust are SSMEs being run at?given no re-use could they be pushed higher?
What is the maximum power level the SSMEs could be run at,considering that they will not be reused?
Unfortunately, the report also states that the failure rates when running at 109% thrust are significantly worse, with a critical engine failure (not a safe shutdown)rate of 1 in every 20 flights.
Quote from: dlapine on 06/02/2009 09:02 pmUnfortunately, the report also states that the failure rates when running at 109% thrust are significantly worse, with a critical engine failure (not a safe shutdown)rate of 1 in every 20 flights.Well, if that report was published in '93, then it probably didn't take into account a lot of the upgrades (such as to the high-pressure turbo pumps and main combustion chamber) that have gone into the engines since then.
One of the best 'alternative' mission profiles which we have been able to confirm so far is that of using the EDS to perform the LOI as well as the TLI.Because the lander doesn't have to perform the LOI, it results in a lander which is considerably smaller and lighter than the current CxP design. This solves almost all of the Altair's height/stability issues and might even allow the thing to fit inside an 8.4m PLF again too. At this size and mass the LSAM & CEV will *easily* fit on a J-130, thus improving both costs and safety for each mission. Also by having multiple engines on an RL-10-powered EDS you get high Isp and a great deal of engine-out capability for the LOI as well, which is nice.With this profile we're seeing about 10% extra payload mass to the Lunar surface as well -- and that's the real point.Ross.
Also, perhaps the easiest way to use the excess CLV capacity is to launch the EDS to an elliptical orbit and use the excess CLV performance to launch the LSAM and CEV to the same elliptical orbit. Less prop is available for TLI but this is more than compensated by the lower dV required.
I may be wrong, but I think that circular orbits have the nice property that you can do the second launch every time the orbit is over your head, while elliptical orbits offer much less launch opportunities.
Any word when we will get to see the full ISDC presentation? Or better yet, the new Direct 3.0 "proposal" with new costs and schedules?
That's a 'difficult' proposition, to say the least, but is not completely unprecedented. Here is an image showing Gemini 12 lifting off from LC-19 at the same time as an Atlas Agena lifts off from LC-14 a few miles away. This was done specifically to enable a docking between the two spacecraft in LEO.
My biggest worry is that the review panel does not go right to the source for information with regards to Direct. If they rely on numbers and data put out by NASA, then I fear it will not be a true Direct review. Already their are rumors that Hawes has already tried to block any non-Contractors from providing official testimony information to the panel. From what I have read on here, Hawes will also provide data and analysis for the panel. I don't see him painting a pretty picture for Direct.Either we cross our fingers and hope the panel sees through the bull, or hopefully the Team gets their shot to present to the panel so they can hear it straight.