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#61
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Multiple Engines???
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#62
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Multiple Engines???
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#63
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Multiple Engines???
Unfortunately, this is more like a boosted SSTO than a TSTO; staging at
only Mach 3, the upper stage is doing almost all of the work. I believe the study's focus was specifically a no-TPS glide-return-to-base 1st stage for a LHOx TSTO. |
#64
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Multiple Engines???
Unfortunately, this is more like a boosted SSTO than a TSTO; staging at
only Mach 3, the upper stage is doing almost all of the work. I believe the study's focus was specifically a no-TPS glide-return-to-base 1st stage for a LHOx TSTO. |
#65
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biamese (was Multiple Engines???)
The fixed proportion of stage sizes constrains the staging point to a
specific value around Mach 3-4. My calculations optimise around 2,200 m/sec - Mach 8+? Bimese requires crossfeed. ... Crossfeed ... is quite complex. Ah, yes. ... the crossfeed flow be shut down and the feed system switch to the internal tanks while the engines keep running. Ah, no. Crossfeed to the next stage's tanks, not its engines. (This implies the pump-fed type.) A true bimese configuration forces the duplication of wholly unnecessary systems on the two stages. So don't do "true biamese". Use the same components where feasible, and simpler/deleted substitutes where it makes engineering sense. Some parts will be overbuilt, but the devil's in the details. An optimally designed orbiter can get by with a T/W of 1 or less at staging. Therefore, forcing commonality puts more engines on the orbiter than it really needs. I'll trade optimality for the ability to abort-to-launch from the pad. For more on this subject, see "Selection of Lockheed Martin's Preferred TSTO Configurations for the Space Launch Initiative" paper number IAC-02-V.4.03 from the 2002 World Space Congress Where can I download a copy? |
#66
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biamese (was Multiple Engines???)
The fixed proportion of stage sizes constrains the staging point to a
specific value around Mach 3-4. My calculations optimise around 2,200 m/sec - Mach 8+? Bimese requires crossfeed. ... Crossfeed ... is quite complex. Ah, yes. ... the crossfeed flow be shut down and the feed system switch to the internal tanks while the engines keep running. Ah, no. Crossfeed to the next stage's tanks, not its engines. (This implies the pump-fed type.) A true bimese configuration forces the duplication of wholly unnecessary systems on the two stages. So don't do "true biamese". Use the same components where feasible, and simpler/deleted substitutes where it makes engineering sense. Some parts will be overbuilt, but the devil's in the details. An optimally designed orbiter can get by with a T/W of 1 or less at staging. Therefore, forcing commonality puts more engines on the orbiter than it really needs. I'll trade optimality for the ability to abort-to-launch from the pad. For more on this subject, see "Selection of Lockheed Martin's Preferred TSTO Configurations for the Space Launch Initiative" paper number IAC-02-V.4.03 from the 2002 World Space Congress Where can I download a copy? |
#67
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biamese (was Multiple Engines???)
"David Shannon" wrote in message om... An optimally designed orbiter can get by with a T/W of 1 or less at staging. Therefore, forcing commonality puts more engines on the orbiter than it really needs. I'll trade optimality for the ability to abort-to-launch from the pad. One possibility that seems obvious is to have OMS pods that fit the same slots as main engines. The unit used as booster has X engines with no OMS pods, while the orbiter unit has X-1 engines plus the OMS pod. If it is a designed in feature, weight and balance could be similar for both modes without divergence of design or dead weight of non functional systems. |
#68
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biamese (was Multiple Engines???)
"David Shannon" wrote in message om... An optimally designed orbiter can get by with a T/W of 1 or less at staging. Therefore, forcing commonality puts more engines on the orbiter than it really needs. I'll trade optimality for the ability to abort-to-launch from the pad. One possibility that seems obvious is to have OMS pods that fit the same slots as main engines. The unit used as booster has X engines with no OMS pods, while the orbiter unit has X-1 engines plus the OMS pod. If it is a designed in feature, weight and balance could be similar for both modes without divergence of design or dead weight of non functional systems. |
#69
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biamese (was Multiple Engines???)
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#70
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biamese (was Multiple Engines???)
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