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#120
by
TrueGrit
on 27 Sep, 2007 22:47
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DeltaIV upperstage is an evolution of that designed for Delta III... The single RL10 was the best choice to meet the reference missions (GSO commercial) the Delta III was designed against. Another engine would increase the cost of the rocket and hurt the reliability, for little gain. And there is no in production option other than RL10... Is that simple enough. Low Earth might be the target for all you space hobbiest, but those of us in the buissness know the money is to be made in GSO.
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#121
by
Propforce
on 27 Sep, 2007 23:05
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tnphysics - 27/9/2007 3:30 PM
Okay. Why didn't the Delta IV developers go with a wider twin engine upper stage?
They could. But not enough sales to justify the "upgrade".
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#122
by
tnphysics
on 27 Sep, 2007 23:06
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I know... but the Delta IV and Delta III upper stages are too small even for GTO missions. Just look at the Atlas V and the WBC.
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#123
by
Jim
on 27 Sep, 2007 23:15
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tnphysics - 27/9/2007 7:06 PM
I know... but the Delta IV and Delta III upper stages are too small even for GTO missions. Just look at the Atlas V and the WBC.
They are correctly sized for GTO
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#124
by
tnphysics
on 27 Sep, 2007 23:54
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Then why is Atlas going to the WBC?
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#125
by
Jim
on 28 Sep, 2007 02:11
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tnphysics - 27/9/2007 7:54 PM
Then why is Atlas going to the WBC?
Atlas is not going to the WBC. That is just a study. WBC is a way of increasing performance without upsetting too many ground interfaces.
This is system engineering. Not everything is optimized for flight performance, cost is always the driver
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#126
by
TrueGrit
on 28 Sep, 2007 20:15
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Too small for GSO? Guess the most capable rocket in the US inventory isn't enough :sigh:
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#127
by
tnphysics
on 28 Sep, 2007 20:28
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Jim - 27/9/2007 10:11 PM
tnphysics - 27/9/2007 7:54 PM
Then why is Atlas going to the WBC?
Atlas is not going to the WBC. That is just a study. WBC is a way of increasing performance without upsetting too many ground interfaces.
This is system engineering. Not everything is optimized for flight performance, cost is always the driver
I was mixed up. Sorry.
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#128
by
tnphysics
on 01 Oct, 2007 01:27
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Why won't the AUS be built?
It will if the WBC flies on Atlas and SpaceX fails.
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#129
by
Jim
on 01 Oct, 2007 01:33
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tnphysics - 30/9/2007 9:27 PM
Why won't the AUS be built?
It will if the WBC flies on Atlas and SpaceX fails.
There are requirements for AUS or WBC
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#130
by
Nick L.
on 01 Oct, 2007 01:50
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tnphysics - 30/9/2007 9:27 PM
Why won't the AUS be built?
It will if the WBC flies on Atlas and SpaceX fails.
Again, not enough payloads in the weight range to spread the costs. It will cost a lot to develop the AUS. You need to finish developing the MB-60 engine, new tankage, possibly new interstages, fairings, guidance system changes, a lot of work needs to be done. Delta IV Heavy already outperforms every other rocket out there right now (Ariane 5 ECA is the next most powerful), and they can't even find enough payloads for it! There are just not enough payloads that heavy. And Boeing/ULA can't compete with Ariane on costs so no commercial dice either.
If WBC flies (which is HIGHLY unlikely, see above), there will be no need to develop the AUS; they will have already saturated the market, there are that few payloads out there that take advantage of the extra capability. SpaceX doesn't have an LV, currently available or planned, that can even match Delta IV Heavy (F9-Heavy has less performance to LEO and GTO than D-IVH).
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#131
by
kevin-rf
on 01 Oct, 2007 02:01
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Isn't ULA now talking about a combined AUS and WBC for both Delta IV and Atlas V called ACES? At least they have it in there power point responding to NASA's ISS Cargo RFI (
http://www.ulalaunch.com/docs/publications/ULA/ISS_Cargo_RFI_Final_09062007.pdf ).
Interesting how closely matched the Delta IV Heavy and Atlas V Heavy performance is based on ULA's numbers in the just mentioned .pdf. Only a 200 kg difference.
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#132
by
Jim
on 01 Oct, 2007 11:06
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Jim - 30/9/2007 9:33 PM
tnphysics - 30/9/2007 9:27 PM
Why won't the AUS be built?
It will if the WBC flies on Atlas and SpaceX fails.
There are requirements for AUS or WBC
I meant no requirements
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#133
by
hyper_snyper
on 02 Oct, 2007 02:31
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I probably know the answer to this but I'm going to ask it anyway to be sure.
D-IVH roll control... is it through gas generator exhaust like all the other Delta IVs or is through outboard CBC engine gimballing?
How would each compare wrt to roll authority?
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#134
by
Nick L.
on 02 Oct, 2007 02:54
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hyper_snyper - 1/10/2007 10:31 PM
I probably know the answer to this but I'm going to ask it anyway to be sure.
D-IVH roll control... is it through gas generator exhaust like all the other Delta IVs or is through outboard CBC engine gimballing?
How would each compare wrt to roll authority?
The Delta IV PPG says that Heavy roll control is by differential gimbaling of the outboard engines. I suspect that the central CBC still has the turbopump exhaust vectoring, for roll control after the strap-on CBCs are jettisoned.
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#135
by
tnphysics
on 04 Oct, 2007 00:09
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I hope that the AUS is eventually built.
It would allow a 3-launch lunar architecture.
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#136
by
Jim
on 04 Oct, 2007 00:34
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It won't be
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#137
by
tnphysics
on 08 Oct, 2007 23:56
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How much would it increase the LEO payload?
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#138
by
TrueGrit
on 09 Oct, 2007 19:33
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#139
by
tnphysics
on 18 Oct, 2007 00:49
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Why dosen't the Delta IV US use the RL-10C, which has more thrust?
This would help the heavy dramatically.
It does have less Isp.