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#20
by
USFdon
on 18 May, 2014 18:34
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Interesting that the Delta IV User's Guide shows what appears to be a dual RL-10 upper stage under future enhancements (though doesn't go into detail about it).
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#21
by
Rocket Science
on 18 May, 2014 21:27
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#22
by
PahTo
on 19 May, 2014 00:10
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Good stuff--thanks! Over the years I've seen references and inferences [EDIT: in NSF] to info contained therein, but I don't think I've read that report before (and I need to re-read a few times). The citations/profiles of the contributors at the end are great.
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#23
by
Lee Jay
on 19 May, 2014 00:28
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IIRC there is also the issue of NASA's 1.4 structures margin.
"Fixing" that takes you back to the drawing board for a new vehicle in many ways.
"Fixing" that can be changing the nonsense of 1.4 to 1.25
What makes it "nonsense"? I'm imagining an answer like "if it can be trusted with billion dollar payloads...." or "as long as the vehicles have abort capability...." but I'm curious as to your thoughts, Jim.
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#24
by
Jim
on 19 May, 2014 00:46
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IIRC there is also the issue of NASA's 1.4 structures margin.
"Fixing" that takes you back to the drawing board for a new vehicle in many ways.
"Fixing" that can be changing the nonsense of 1.4 to 1.25
What makes it "nonsense"? I'm imagining an answer like "if it can be trusted with billion dollar payloads...." or "as long as the vehicles have abort capability...." but I'm curious as to your thoughts, Jim.
Have you ever heard of a vehicle failure due to a component that was overloaded?
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#25
by
Lee Jay
on 19 May, 2014 00:47
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IIRC there is also the issue of NASA's 1.4 structures margin.
"Fixing" that takes you back to the drawing board for a new vehicle in many ways.
"Fixing" that can be changing the nonsense of 1.4 to 1.25
What makes it "nonsense"? I'm imagining an answer like "if it can be trusted with billion dollar payloads...." or "as long as the vehicles have abort capability...." but I'm curious as to your thoughts, Jim.
Have you ever heard of a vehicle failure due to a component that was overloaded?
No, but I have probably 1% of the historical knowledge you do. Is that your argument? That historical data seems to indicate that 1.25 is sufficient? If so, that would seem to have statistical merit if the history supports it.
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#26
by
Jim
on 19 May, 2014 01:04
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Have you ever heard of a vehicle failure due to a component that was overloaded?
No, but I have probably 1% of the historical knowledge you do. Is that your argument? That historical data seems to indicate that 1.25 is sufficient? If so, that would seem to have statistical merit if the history supports it.
[/quote]
1.4 vs 1.25 is really an emotional issue
This is a good read
http://www.amazon.com/Space-Systems-Failures-Satellites-Exploration/dp/0387215190
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#27
by
Lee Jay
on 19 May, 2014 01:10
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Okay, from a conceptual/emotional point of view...
There are two general ways to deal with failure - safe life, and fail safe.
Safe life is about making it so it won't fail.
Fail safe is about making it safe even when it fails.
Airliners are exceptionally safe, mostly because of the later (fail safe). A whole bunch of things have to go wrong for an airliner to fail, because most failures are fail-safe.
If the vehicles have a proven, well-designed, high reliability abort system (a system in the fail safe category), I'd be happy with less safe life type margin.
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#28
by
sdsds
on 19 May, 2014 04:00
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Have you ever heard of a vehicle failure due to a component that was overloaded?
While it didn't lead to a mission failure, the attached photo is of a booster that was nominally supposed to be reusable. That's a structural component that "failed" during a mission. Sure, it was exposed to off-nominal stresses. But that's why we leave the extra structural margin in the designs even when it is proven to be unnecessary in the nominal case.
(I know. You weren't asking me!
)
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#29
by
Lee Jay
on 19 May, 2014 13:08
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Have you ever heard of a vehicle failure due to a component that was overloaded?
While it didn't lead to a mission failure, the attached photo is of a booster that was nominally supposed to be reusable. That's a structural component that "failed" during a mission. Sure, it was exposed to off-nominal stresses. But that's why we leave the extra structural margin in the designs even when it is proven to be unnecessary in the nominal case.
(I know. You weren't asking me! )
It didn't fail during ascent, it failed impacting the water after chute failure. This would not have endangered any crew being carried.
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#30
by
Joel
on 19 May, 2014 14:35
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Is there an educated guess on how long a Delta IV human-rating could take? Assuming silly rules such as 1.25 vs. 1.4 are waivered.
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#31
by
savuporo
on 19 May, 2014 18:54
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If we have this thread, lets have it from the horses mouth.
http://enu.kz/repository/2009/AIAA-2009-6729.pdfThe Delta IV has ample performance to support the existing Orion vehicle, without Black Zones. The Delta IV can support a mid-2014 Crewed IOC, which is superior to Orion launch alternatives. The proposed 37A pad is a look-alike counterpart to the existing 37B pad with low development risk. Human rating the Delta is a relatively modest activity, with the addition of an Emergency Detection System, an array of relatively small redundancy and safety upgrades, both in the vehicle and the engines that are minor compared to the original development of the Delta IV.
Maybe they were optimistic.
Same quote in here :
https://info.aiaa.org/tac/SMG/STTC/White%20Papers/ULA-Innovation-March-2010.pdf?origin=publication_detail
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#32
by
simonbp
on 19 May, 2014 23:10
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Is there an educated guess on how long a Delta IV human-rating could take? Assuming silly rules such as 1.25 vs. 1.4 are waivered.
This Aerospace Corp. report (which was posted above) covers the important issues:
http://www.nasa.gov/pdf/377875main_081109%20Human%20Rated%20Delta%20IV.pdfUsing the Ares I standards for human-rating, neither the first stage nor second stage engine are ready for human flights. They assumed the first stage would need "RS-68B HR", which was the version being developed for Ares V, while the second stage would need either J-2X or a cluster of RL-10As. Either way, these are things that would take nearly as long to develop as the new hydrocarbon engine that Congress wants...
Rather interestingly, that report also mentions the possibility of a Delta IV H with
no upper stage. They claim this is sufficient to get an Orion to ISS (but not if it had a lunar SM). If human-rating the RS-68A is not difficult, then a Delta IV H with no upper stage could the quickest route to launching CST-100 or DreamChaser (but not exactly cheap per flight).
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#33
by
jongoff
on 19 May, 2014 23:34
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IIRC there is also the issue of NASA's 1.4 structures margin.
"Fixing" that takes you back to the drawing board for a new vehicle in many ways.
"Fixing" that can be changing the nonsense of 1.4 to 1.25
Especially seeing as how the Shuttle ETs had margins of only 1.15 in some areas...
~Jon
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#34
by
the_roche_lobe
on 19 May, 2014 23:52
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Rather interestingly, that report also mentions the possibility of a Delta IV H with no upper stage. They claim this is sufficient to get an Orion to ISS (but not if it had a lunar SM).
I wonder if that would allow the core stage to be used in partial thrust all the way - making it a real sustainer stage?
Anyway, as you say, still sounds expensive! And whats the mission again?
P
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#35
by
edkyle99
on 19 May, 2014 23:55
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Note that the 2009 Aerospace Corp report also said that the current Atlas 5 Centaur RL10 engine was not human rated. Nonetheless, two commercial crew entrants are proposing its use.
- Ed Kyle
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#36
by
Joel
on 20 May, 2014 11:18
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Rather interestingly, that report also mentions the possibility of a Delta IV H with no upper stage. They claim this is sufficient to get an Orion to ISS (but not if it had a lunar SM). If human-rating the RS-68A is not difficult, then a Delta IV H with no upper stage could the quickest route to launching CST-100 or DreamChaser (but not exactly cheap per flight).
Maybe combine this with booster flyback? A core will fly exactly three times, twice as side booster and once as center core. Combined with no upper stage, that might make it more affordable per flight.
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#37
by
rpapo
on 20 May, 2014 13:02
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Rather interestingly, that report also mentions the possibility of a Delta IV H with no upper stage. They claim this is sufficient to get an Orion to ISS (but not if it had a lunar SM). If human-rating the RS-68A is not difficult, then a Delta IV H with no upper stage could the quickest route to launching CST-100 or DreamChaser (but not exactly cheap per flight).
Maybe combine this with booster flyback? A core will fly exactly three times, twice as side booster and once as center core. Combined with no upper stage, that might make it more affordable per flight.
Are you confusing Delta Heavy with Falcon Heavy?
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#38
by
Zed_Noir
on 20 May, 2014 13:30
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Note that the 2009 Aerospace Corp report also said that the current Atlas 5 Centaur RL10 engine was not human rated. Nonetheless, two commercial crew entrants are proposing its use.
- Ed Kyle
Both of the commercial crew entries are using the unflown duo Centaur version for their missions, not the single Centaur version currently use with the Atlas V.
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#39
by
baldusi
on 20 May, 2014 13:40
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Note that the 2009 Aerospace Corp report also said that the current Atlas 5 Centaur RL10 engine was not human rated. Nonetheless, two commercial crew entrants are proposing its use.
- Ed Kyle
Both of the commercial crew entries are using the unflown duo Centaur version for their missions, not the single Centaur version currently use with the Atlas V.
It's a performance issue. Single RL10 is puny for LEO. If you look at the presentation, dual engine Centaur has by far the worst risk profile. It needs the two engines and any failure would mean LOM, thus, worst performance. A 4 engine US would only need two, and thus could tolerate a lot of propulsion failures. BTW, the Aerospace Corp paper was done assuming Ares I human rating process. Which has been (luckily) deprecated. As Jim said, is not about inflating specs to say "thus it is safer". It's about looking into actual failure modes and probabilities and minimizing overall risk. And let the contractor make their decisions as long as they hit the risk probabilities!
)