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#100
by
Danderman
on 04 Aug, 2011 20:49
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As for a "thicker" Centaur, *rockets aren't Legos*, you can't just "thicken" a Centaur.
yes, it can. The skin gage for it and the old Atlas were changed at will to suit mission requirements in the past
"Thickening the skin" of the Centaur won't help support > 20,000 lbs payload weight.
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#101
by
Danderman
on 04 Aug, 2011 20:50
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Jim or any expert,
How does the 421 configuration (2 engine Centaur and 1 solid) help you? Is it more payload to orbit?
I am not an expert, but the 2nd engine helps mitigate gravity losses during early stages of Centaur flight.
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#102
by
mmeijeri
on 04 Aug, 2011 20:54
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"Thickening the skin" of the Centaur won't help support > 20,000 lbs payload weight.
Why not?
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#103
by
kevin-rf
on 04 Aug, 2011 20:59
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They are also using dual-engine Centaur on all man-rated Atlas Vs for LOC/LOM and redundancy reasons I believe. Extra engine in case one doesn't fire at all on staging.
Raised eyebrow... I suspect if an RL-10 fails for any reason, the other will be shut down and an abort will occur. It is better to cut ones losses and safely recover the crew than push a bad situation and risk a LOM.
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#104
by
Xplor
on 04 Aug, 2011 20:59
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I'm no expert but...
How does the 421 configuration (2 engine Centaur and 1 solid) help you? Is it more payload to orbit?
It's 412 - PLF size, number of solids, number of engines on Centaur
The benefit is payload to orbit. The 5m PLF weighs more and the Dual Engine Centaur has higher thrust meaning it sacrifices the ability to push things beyond LEO in exchange for pushing more to LEO. The solid is just for extra thrust in the first ~75 seconds of flight.
Both the second RL10 and SRB increase performance to LEO. The second RL10 also provides additional upper stage thrust allowing the trajectory to be depressed enhancing abort options.
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#105
by
Robotbeat
on 04 Aug, 2011 21:03
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They are also using dual-engine Centaur on all man-rated Atlas Vs for LOC/LOM and redundancy reasons I believe. Extra engine in case one doesn't fire at all on staging.
Raised eyebrow... I suspect if an RL-10 fails for any reason, the other will be shut down and an abort will occur. It is better to cut ones losses and safely recover the crew than push a bad situation and risk a LOM.
Disagree. By pushing the button, you GUARANTEE loss of mission (LOM). If an engine goes out but the remaining one is capable of getting you to orbit, better not to abort. LAS systems aren't designed to be terribly safe when activated... they only are used incredibly rarely and only have a survival probability design of around 90%. Launch abort is NOT without risks!
If the other engine goes, THEN press the button.
If you abort the first time you have engine trouble, Shuttle would've likely aborted instead of completed the mission at a lower orbit once or twice. Other missions, too.
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#106
by
Lee Jay
on 04 Aug, 2011 21:03
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They are also using dual-engine Centaur on all man-rated Atlas Vs for LOC/LOM and redundancy reasons I believe. Extra engine in case one doesn't fire at all on staging.
Raised eyebrow... I suspect if an RL-10 fails for any reason, the other will be shut down and an abort will occur. It is better to cut ones losses and safely recover the crew than push a bad situation and risk a LOM.
You mean LOC? An abort guarantees LOM.
An abort with a single RL-10 could potentially be safer than a LAS abort. LAS aborts carry risks too.
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#107
by
Xplor
on 04 Aug, 2011 21:04
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Any Atlas V-4XX vehicle has a weight constraint of 20,000 lbs, regardless of how many Centaur engines or strap-ons are used. Its a structural constraint.
To remove the constraint, Atlas V-5XX is used, as the payload fairing can support the additional weight. However, the Boeing capsule will not use a 5xx series Atlas.
How Boeing is going to get around that constraint is a mystery to me.
While Atlas 4XY was only qualified to 20,000 lbs as part of the Atlas V development it can actually cary substantially more mass, both structurally and for performance reasons.
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#108
by
FinalFrontier
on 04 Aug, 2011 21:04
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This is excellent news! The most reliable launcher wins out again, glad to hear they made this choice. Cannot wait to see cst 100 fly.
Big win for US HSF in general here.
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#109
by
mmeijeri
on 04 Aug, 2011 21:06
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Disagree. By pushing the button, you GUARANTEE loss of mission (LOM). If an engine goes out but the remaining one is capable of getting you to orbit, better not to abort. LAS systems aren't designed to be terribly safe when activated... they only are used incredibly rarely and only have a survival probability design of around 90%. Launch abort is NOT without risks!
If the other engine goes, THEN press the button.
I'm not sure, but I think I've seen our experts say thrust vectoring capability would be insufficient to deal with an engine-out situation.
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#110
by
Robotbeat
on 04 Aug, 2011 21:07
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Disagree. By pushing the button, you GUARANTEE loss of mission (LOM). If an engine goes out but the remaining one is capable of getting you to orbit, better not to abort. LAS systems aren't designed to be terribly safe when activated... they only are used incredibly rarely and only have a survival probability design of around 90%. Launch abort is NOT without risks!
If the other engine goes, THEN press the button.
I'm not sure, but I think I've seen our experts say thrust vectoring capability would be insufficient to deal with an engine-out situation.
Yes, but we were talking about the case where engine-out is a viable capability.
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#111
by
kevin-rf
on 04 Aug, 2011 21:11
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I'm not sure, but I think I've seen our experts say thrust vectoring capability would be insufficient to deal with an engine-out situation.
Yes, but we were talking about the case where engine-out is a viable capability.
Can you point me to where in the announcement they said they would be adding enough vectoring for the DEC to continue on a single engine?
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#112
by
Herb Schaltegger
on 04 Aug, 2011 21:12
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"Thickening the skin" of the Centaur won't help support > 20,000 lbs payload weight.
In a monocoque or semi-monocoque structure, the skin is very much structural. In aircraft, that skin is often only a few thousands of an inch thick.
So in a nutshell, yes it can.
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#113
by
douglas100
on 04 Aug, 2011 21:14
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Raised eyebrow... I suspect if an RL-10 fails for any reason, the other will be shut down and an abort will occur. It is better to cut ones losses and safely recover the crew than push a bad situation and risk a LOM.
I think that's right. In the past, if only one RL 10 lit the Centaur became uncontrollable. See
http://www.thespacereview.com/article/1321/1 I'm assuming that would be the same for a dual engined Centaur with Atlas V. In which case definite loss of mission.
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#114
by
psloss
on 04 Aug, 2011 21:16
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#115
by
Robotbeat
on 04 Aug, 2011 21:18
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I'm not sure, but I think I've seen our experts say thrust vectoring capability would be insufficient to deal with an engine-out situation.
Yes, but we were talking about the case where engine-out is a viable capability.
Can you point me to where in the announcement they said they would be adding enough vectoring for the DEC to continue on a single engine?
I assumed that's what you were referring to. If there's no engine-out capability, obviously it goes without saying that you would abort if an engine fails.
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#116
by
peter-b
on 04 Aug, 2011 21:19
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Capsule made by Boeing to launch on launcher made by Boeing!
In other news, the Pope is Catholic. I don't think anybody should have been surprised by this decision.
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#117
by
renclod
on 04 Aug, 2011 21:21
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...
LAS systems aren't designed to be terribly safe when activated...
However an upper stage abort would not require activation of full thrust LAS.
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#118
by
Robotbeat
on 04 Aug, 2011 21:22
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...
LAS systems aren't designed to be terribly safe when activated...
However an upper stage abort would not require activation of full thrust LAS.
It's still not terribly safe. If engine-out capability is available, better to take advantage of it. Keep the abort as a last resort.
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#119
by
mmeijeri
on 04 Aug, 2011 21:24
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Capsule made by Boeing to launch on launcher made by Boeing!
Made by ULA, which is
co-owned by Boeing. And Atlas used to be built by Lockheed Martin, not Boeing. I think Boeing still has exclusive marketing rights to Delta for commercial clients and Lockheed Martin has the same rights for Atlas.