Author Topic: Current Status - Simplification!  (Read 7391 times)

Offline Mogster

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Re: Current Status - Simplification!
« Reply #20 on: 11/19/2009 01:20 PM »
Good thread, answered some questions I was too embarrassed to ask..... :)

Offline William Barton

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Re: Current Status - Simplification!
« Reply #21 on: 11/19/2009 01:26 PM »
Jupiter: Shuttle 8.4m external tank (with modifications), Shuttle SSMEs, Shuttle 4-segment SRBs.

That's a tad bid deceptive. The Direct core stage is 8.4m, and could be built with SWLT toolings, but it is really a new stage with completely new load paths. In comparison, the Sidemount HLV literally uses a Shuttle external tank.

Ross says that this isn't actually possible, sidemount has 2x loads or more, and thus the tank will need to be redesigned for it too.

I think that's specific to the SD-HLV being proposed. If you want something that can be swapped out for the orbiter without redesigning anything else, it will probably look like Shuttle-C, which is basically a wingless, TPS-less, unmanned expendable Orbiter (extra payload comes from what's left off).

Offline robertross

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Re: Current Status - Simplification!
« Reply #22 on: 11/19/2009 01:35 PM »
Jupiter: Shuttle 8.4m external tank (with modifications), Shuttle SSMEs, Shuttle 4-segment SRBs.

That's a tad bid deceptive. The Direct core stage is 8.4m, and could be built with SWLT toolings, but it is really a new stage with completely new load paths. In comparison, the Sidemount HLV literally uses a Shuttle external tank.

Ross says that this isn't actually possible, sidemount has 2x loads or more, and thus the tank will need to be redesigned for it too.

I think that's specific to the SD-HLV being proposed. If you want something that can be swapped out for the orbiter without redesigning anything else, it will probably look like Shuttle-C, which is basically a wingless, TPS-less, unmanned expendable Orbiter (extra payload comes from what's left off).

No it isn't. In a lunar application, the EDS fits into the payload shroud, along with the cargo mass. All that extra mass apparently sits further out than the orbiter does, especially the mass of the shroud, and seriously affects the center of gravity of the unit, effectively requiring a strengthened external tank.

How much this gets affected for a LEO unit only to ISS, it would depend.
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Offline Analyst

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Re: Current Status - Simplification!
« Reply #23 on: 11/19/2009 02:29 PM »
There is no need to enclose the whole EDS in a fairing. It could serve as its own fairing, with the payload on top in a real fairing. There is no need to talk fairing diameters again.

And there is no need to repeat points for DIRECT ad infinitum. It has advantages and disadvantages, like any other solution has.

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Offline William Barton

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Re: Current Status - Simplification!
« Reply #24 on: 11/19/2009 02:38 PM »
There is no need to enclose the whole EDS in a fairing. It could serve as its own fairing, with the payload on top in a real fairing. There is no need to talk fairing diameters again.

And there is no need to repeat points for DIRECT ad infinitum. It has advantages and disadvantages, like any other solution has.

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That was my perception as well. In the previous response, I was purely addressing the why's of the weights and stresses, obviously not suggesting launching an EDS inside a Shuttle-C cargo bay. In my 2004 essay, I suggested mounting the EDS in a thrust-frame, above the SSME/OMS pod, similar to the thrust frame that was used in the 1970s to test the stresses placed on the ET by the SSMEs in the first place. I don't know that it could really be made to work that way, since I'm not an engineer, but it's hard to imagine this configuration placing much more stress on the ET than hanging a rocketplane the size of an airliner off its side. The real advantage sidemount has over in-line, when it comes to SDV, is, it looks superficially plausible to the hundreds of lawyers who will be voting whether or not to imbue it with taxpayer money. And why should they listen to advice from rocket scientists about it? That's what they got the first time, and it hasn't exactly worked out well.

Offline yg1968

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Re: Current Status - Simplification!
« Reply #25 on: 11/19/2009 05:00 PM »
If you follow the logic of the Augustine committee, there is no money to operate a HLV before 2020 even if it could be ready before that time. As far as servicing the ISS and LEO, they would rather use the commercial crew option and neither Ares I, sidemount or Direct qualifies as commercial in their mind.   So which one of these options can be ready the fastest is irrelevant.
« Last Edit: 11/19/2009 05:03 PM by yg1968 »

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