NASA's new moon plans lots of questions.

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barrykirk

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I"ve got a lot of questions about the new NASA moon plans. What I'm trying to figure out is there another configuration that might be cheaper.<br /><br /><br />I'll start with the Heavy lift cargo launch vehicle.<br /><br />2 SRB extended from 4 sections to 5 sections.<br />5 SSME on an extended shuttle fuel tank.<br /><br />My questions:<br /><br />1) Are the SRB boosters re-usable like the shuttle SRBs? Or to put it another way, do they seperate at about the same velocity and altitude as the shuttle SRBs?<br /><br />2) Looks to me like the 5 SSME with extended shuttle fuel tank goes all the way to LEO. On the old shuttle the fuel tank was disposible, but we got the 3 SSME back. With this system do we lose 5 SSME for every launch?<br /><br />3) How expensive are SSMEs?<br /><br />4) If the SSME is very expensive, would it be possible to build a heat shield/re-entry section just for the SSME and not the tank? How much payload would we lose by doing that?<br /><br />5) Does it make any sense to go to 4 SRB instead of 2? How much would that increase the payload? Would it increase the velocity / altitude of SRB seperation to the point where they are no longer re-usuable?<br /><br />6) How much cheaper would the core engines be if they burned LOX/RP1 instead of LOX/LH2? In other words, Saturn V first stage style engines? Would that drop the payload? Could that be compensated by going to 4 SRBs?<br /><br /><br />And for the Crew Launch Vehicle.<br /><br />1 SRB and 1 SSME<br /><br />1) So, it looks like we lose another SSME for each launch?<br /><br />Hey, I just thought of a use for an actual lifting body shuttle. Would it be possible to gather up all of these SSME engines from multiple launches and return them to earth in the cargo bay of an old style shuttle? Just a thought.
 
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nacnud

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<font color="yellow">1) Are the SRB boosters re-usable like the shuttle SRBs? Or to put it another way, do they seperate at about the same velocity and altitude as the shuttle SRBs? <br /><br /><font color="white">Yes Griffin mentioned the 4 section single stick SRB could be reused, dunno about the 5 section one. My SWAG is the separation events are at similar velocities for STS and the new vehicles.<br /><br /><font color="yellow">2) Looks to me like the 5 SSME with extended shuttle fuel tank goes all the way to LEO. On the old shuttle the fuel tank was disposible, but we got the 3 SSME back. With this system do we lose 5 SSME for every launch? <br /><br /><font color="white">Yes<br /><br /><font color="yellow">3) How expensive are SSMEs? <br /><br /><font color="white">I can’t recall but if you search the site Shuttle_Guy has given the cost before, I think a throw away SSME is about $40M<br /><br /><font color="yellow">4) If the SSME is very expensive, would it be possible to build a heat shield/re-entry section just for the SSME and not the tank? How much payload would we lose by doing that? <br /><br /><font color="white">You could but I don’t think it would be cheaper, even in the long run.<br /><br /><font color="yellow">5) Does it make any sense to go to 4 SRB instead of 2? How much would that increase the payload? Would it increase the velocity / altitude of SRB seperation to the point where they are no longer re-usuable? <br /><br /><font color="white">To keep the seportation velocity and altitude the same a 4 SRB vehicle would need 10 SSME and a payload of 250 tonnes, I don’t think that is practical, or needed, for a while.<br /><br /><font color="yellow">6) How much cheaper would the core engines be if they burned LOX/RP1 instead of LOX/LH2? In other words, Saturn V first stage style engines? Would that drop the payload? Could that be compensated by going to 4 SRBs?<br /><br /><font color="white">It would drop the payload due to the loss of ISP, there are already the high performance SSME, I think th</font></font></font></font></font></font></font></font></font></font></font></font>
 
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nexium

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If we are making five or ten trips to the moon, including unmanned test flights, something like the new moon plans are much cheaper and will get us to the moon sooner than designing new sub systems. For 100 manned flights to the moon, we save big money with new designs, provided NASA works smarter than they have in recent decades.<br />I did not know shuttle SRBs were reusable. Is it producing a sizable payload penilty? The refurbishing and recovery cost is what percentage of the cost of building new SRBs?<br />Adding a heat shield, and keeping the heat shield properly oriented during re-entry is doable, but very costly with some pay load penity. Perhaps worse, if an SSME makes a soft landing on a children's hospital instead of where it should land, great PR damage is done. Controlled re-entry does increase risk at least slightly. RP1 is less costly than H2 = hydrogen but there is a payload penalty.<br />Gathering up SSMEs is a bit like gathering up the beer cans that boaters throw over board. It can be done, but costs far more than the beer cans/SSMEs are worth. Neil
 
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barrykirk

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Just as a point of comparison, I'll be comparing the SSME to the Merlin 1 engine from spacex.<br /><br />Thrust in vacuum:<br />Merlin 1 : 92,000 LB<br />SSME: 512,300 LB<br /><br />ISP in vacuum:<br />Merlin 1: 304 seconds<br />SSME : 452 seconds<br /><br />Thrust to weight:<br />Merlin 1: 96 to 1<br />SSME: 66 to 1<br /><br />Cost per engine:<br />Merlin 1: Unknown, but I'm guessing less than $2 million<br />SSME: approximatly $40 million.<br /><br />Spacex is advertising a launch cost of $5.9 million for an entire falcon 1 rocket which uses a merlin 1 rocket engine in the first stage and an entire second stage and that cost includes launching range fees.<br /><br />So, the SSME generates 6 times the thrust but costs 20 times as much. It is much less efficient when it comes to fuel usage, but it makes up for that in the following ways.<br /><br />1) 50% higher thrust to weight ratio... So, replacing 5 SSME with 30 Merlin 1 would give the same thrust but with signficantly lower engine mass. <br /><br />2) RP-1 is much denser than Hydrogen so the fuel tank can be smaller, lighter. The fuel lines can be smaller diameter also which saves even more weight.<br /><br />3) RP-1 can be stored at room temperature, LH-2 needs to be super cooled. So their is a space, weight savings in insulation.<br /><br />4) LH-2 tanks need to be built to higher standards than RP-1 cause LH-2 leaks from the smallest crack, but RP-1 is really viscus.<br /><br />So with the Merlin engine, the engines are cheaper and the fuel tank is cheaper and lighter. These are important things to consider for components that are used once and thrown away.
 
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barrykirk

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Looks like a cross posted with you Shuttle_RTF... I was going on $40 million per SSME.... Well $20 million per SSME changes things a lot.<br /><br />Do you know if that is the current cost, or the cost if we start mass producing them?<br /><br />The other question I have is this.<br /><br />If we add 2 more SRB bringing the total to 4, this should increase the velocity at SRB seperation. At what velocity do thermal issues make it difficult or impossible to reuse the SRBs?
 
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kane007

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<font color="yellow">How expensive are the SSMEs?</font><br /><br />Found that early post of shuttle_guys he has used a figure of $240m for 6 engines, which I calculate at $40m for each throwaway. But I have heard some lower figures.<br /><br /><font color="red">DO NO HARM</font>/safety_wrapper>
 
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