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Hi, I was just reading about the different Shuttle C, Z, and Ares proposals for various derivations of the Moon Mars initive and I was wondering how complicated would it be to add two more mounting points to the external tank so that there was one mounted every 90 degrees. Also is there any major configuration problem if such a design were used to mount an engine pod directly under the tank. Assuming such a configuration was possible do you think that 200 tonnes to LEO is possible? Possibly 250 with the proposed new 5 segment boosters?
Thanx all in advance!
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The problem with large numbers of SRBs is the reliability of all those rockets working properly. For 4 rockets, it is the operational reliability to the fourth power.
On the other hand, the Delta rockets have shown that large numbers of SRBs can be done well.
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I suspect the stress on the vehicle at maximum dynamic pressure (Max-Q) would be too great. Unless the extra SRB's can be staged; lit after the first two SRB's have been spent? Perhaps longer-burning 6,7 or 8 segment SRB's are the better route?
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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I suspect the stress on the vehicle at maximum dynamic pressure (Max-Q) would be too great. Unless the extra SRB's can be staged; lit after the first two SRB's have been spent? Perhaps longer-burning 6,7 or 8 segment SRB's are the better route?
You make an excelent point. Not only would extra segments get around the Max-Q problem but I suspect it would be a much simpler and cheaper project then modifying the external tank and the associated fuel lines for the engine pod.
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I'd like to note that making SRBs much bigger than the Shuttle 5-segment heavy duty motors will probably get problematic... i'm wary enough about using them on manned vehicles at all. See Titan-IV HLV. This would also not avoid the need for engine plumbing changes most likly.
Smaller SRBs like those on Delta and a lesser extent Atlas-V can be made reliable because of their small size and early burnout, it isn't practical to make a multi-burn ignition booster, but it might be possible to make one with a different thrust regieme... difficult though, and would risk fuel damage I bet.
And that would be alot of thrust too... the tank would have to be redesigned and strengthend I imagine.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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IIRC, the Delta IV uses 9 SRBs with 6 of them firing from the ground. When those 6 burn out, the 1st stage liquid fires and the remaining 3 SRBs light off.
The other thing too is that SRBs have lousy Isp values. That's not too big of a problem in the initial portion of the flight when you're at low speeds. However, when your velocity starts going up, SRBs give proportionally less and less payback. Boosting the total vehicle mass eventually requires really huge SRBs or beefed up liquid stages to take up the slack in the later stages of thrusting.
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This topic was also fixed for artifacts and shifting
Was searching for the SRB topic which had the oscillation but it may have faded into the crash to be lost....
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