-
#40
by
Prober
on 20 May, 2014 14:01
-
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.
define: unflown duo Centaur do you know the history?
-
#41
by
edkyle99
on 20 May, 2014 14:02
-
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.
I'm talking about the engine itself, not the stage.
Again, from the report:
"
Both RL10 variants (Delta 4 and Atlas 5 versions) currently do not meet the
structural requirements outlined in NASA-STD-5012. It is possible that design modifications could achieve these requirements, but substantial modifications to the engine appear likely. One concept developed to achieve these requirements is to perform the first hot-fire at current thrust levels to cold work the engine components in question, followed by trimming the engine to a lower thrust level that would meet the standard. The drawback to this approach is the loss of available thrust to the second stage. In order to mitigate this problem, a cluster of four thrust-derated RL10s could be considered."
- Ed Kyle
-
#42
by
PahTo
on 20 May, 2014 14:14
-
Does the RL-10C-1 offer the noted modifications to make the engine more palatable, or are they simply stream-lined manufacturing processes to reduce overall cost?
Which is more likely: two engine Centaur (or perhaps more accurately, two engine 4 meter upper stage) or the 5 meter 1/2/4 engine upper stage posited by ULA per ACES? To read the 2009 ULA report, they make it sound like human rating is relatively easily attainable...
-
#43
by
kevin-rf
on 20 May, 2014 14:30
-
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.
define: unflown duo Centaur do you know the history?
I believe the history is only the single engine Centaur transitioned from hydraulic steering to electric steering. The work to transition Dual Engine Centaur (DEC) from hydraulic to electric has not yet been completed. Thus while hydraulic DEC's have been flying since the start of the program, the electric DEC has not yet flown.
-
#44
by
Prober
on 20 May, 2014 14:32
-
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.
define: unflown duo Centaur do you know the history?
I believe the history is only the single engine Centaur transitioned from hydraulic steering to electric steering. The work to transition Dual Engine Centaur (DEC) from hydraulic to electric has not yet been completed. Thus while hydraulic DEC's have been flying since the start of the program, the electric DEC has not yet flown.
that's a fair point.
-
#45
by
baldusi
on 20 May, 2014 14:50
-
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.
define: unflown duo Centaur do you know the history?
I believe the history is only the single engine Centaur transitioned from hydraulic steering to electric steering. The work to transition Dual Engine Centaur (DEC) from hydraulic to electric has not yet been completed. Thus while hydraulic DEC's have been flying since the start of the program, the electric DEC has not yet flown.
that's a fair point.
Yes, but sort of a technicality. The electromecanical TVC has been proven time and again on the Atlas V, and the hydraulic dual Centaur flew a lot. In fact, the human rated Centaur will fly with Common Avionics that, while having a lot of Atlas V inheritance, will be a new development. But it will include the EDS and thus get a lot of flight history.
Thus, for whoever it needs to, the Common Avionics and RL10C-1/2 seem to be human rated. RS-68A is almost there. And the Common Booster Core is based on the (5,4), thus, it should have good margins for a (4,2). If SLS had human rated the DIVUS, then Crewed Delta IV would have been a very easy task.
-
#46
by
Antares
on 20 May, 2014 14:55
-
"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.
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
But isn't everything really a structural failure (unless, obviously, it's software or electrical)? That additional 15% protects for the random defects that aren't caught by normal QA. I'm not saying a perfectly good, existing vehicle at 1.25 needs to be 1.4; but a clean-sheet vehicle designed to 1.4 will be more robust to escapes, at the expense of weight, cost and performance.
*Possible* failures that could have been stopped with 15% more margin: Delta 269, Delta 241, AC-62, K-11, and the 3 Titan failures in the 80s.
-
#47
by
Antares
on 20 May, 2014 15:05
-
Does changing to 1.25 change much in the calculations of probabilities for LOM and LOC? I've always been amazed at the odds that get calculated for something as complex as a launch vehicle. I reminds me of the odds that Mr. Spock always quoted to Kirk when he couldn't possibly have enough information to make a reasonable calculation. It seems to me that a history of performance is a better indicator.
NASA reliability predictions are crap. They are not absolute (1 in X) and yet they are treated as such. They are a relative measure of perceived design simplicity and perceived QA practices. NASA has never published its statistical inputs to these methods. Perfectly good vehicles are held as less reliable by methods not subject to public scrutiny. They are at best a Pareto tool to suggest where the weak points in a design are, yet the answers are entirely subject to the perceived risk values arbitrarily assigned to the components. There's no validation of those risk values.
See Jeff Greason's retort to Joe Fragola's testimony during the Augustine Committee.
-
#48
by
PahTo
on 20 May, 2014 16:03
-
...
Thus, for whoever it needs to, the Common Avionics and RL10C-1/2 seem to be human rated. RS-68A is almost there. And the Common Booster Core is based on the (5,4), thus, it should have good margins for a (4,2). If SLS had human rated the DIVUS, then Crewed Delta IV would have been a very easy task.
I was under the impression the RL-10C-2 is out of consideration for human rating due to the extensible nozzle.
And wasn't SLS looking to HR the iCPS (based on the 5 meter DCSS)? I guess what I'm trying to pin down (and per thread topic) aren't we really talking about the Delta-IV M 4 (+x) here--the 4 meter cryo upper stage? No need for D-IV H (thus 5 meter upper stage) for commercial crew.
-
#49
by
baldusi
on 20 May, 2014 16:22
-
...
Thus, for whoever it needs to, the Common Avionics and RL10C-1/2 seem to be human rated. RS-68A is almost there. And the Common Booster Core is based on the (5,4), thus, it should have good margins for a (4,2). If SLS had human rated the DIVUS, then Crewed Delta IV would have been a very easy task.
I was under the impression the RL-10C-2 is out of consideration for human rating due to the extensible nozzle.
And wasn't SLS looking to HR the iCPS (based on the 5 meter DCSS)? I guess what I'm trying to pin down (and per thread topic) aren't we really talking about the Delta-IV M 4 (+x) here--the 4 meter cryo upper stage? No need for D-IV H (thus 5 meter upper stage) for commercial crew.
You are right that RL10C-2 isn't human ratable without some significant nozzle redesign. But you can always put an RL10C-1 and eat the performance difference. I understand that ULA will try to move to Common Centaur, which would solve the upper stage issue for Delta IV.
But while SLS was paying for iCPS human rating, it would have made more sense to human rate the (5,2) than the (4,2). Since they have dropped that requirement (for now), I would go with Common Centaur for the upper stage.
-
#50
by
notsorandom
on 20 May, 2014 17:27
-
...
Thus, for whoever it needs to, the Common Avionics and RL10C-1/2 seem to be human rated. RS-68A is almost there. And the Common Booster Core is based on the (5,4), thus, it should have good margins for a (4,2). If SLS had human rated the DIVUS, then Crewed Delta IV would have been a very easy task.
I was under the impression the RL-10C-2 is out of consideration for human rating due to the extensible nozzle.
And wasn't SLS looking to HR the iCPS (based on the 5 meter DCSS)? I guess what I'm trying to pin down (and per thread topic) aren't we really talking about the Delta-IV M 4 (+x) here--the 4 meter cryo upper stage? No need for D-IV H (thus 5 meter upper stage) for commercial crew.
You are right that RL10C-2 isn't human ratable without some significant nozzle redesign. But you can always put an RL10C-1 and eat the performance difference. I understand that ULA will try to move to Common Centaur, which would solve the upper stage issue for Delta IV.
But while SLS was paying for iCPS human rating, it would have made more sense to human rate the (5,2) than the (4,2). Since they have dropped that requirement (for now), I would go with Common Centaur for the upper stage.
Is using the Centaur on the Delta IV something that has ever been talked about by ULA?
-
#51
by
Jim
on 20 May, 2014 17:39
-
Is using the Centaur on the Delta IV something that has ever been talked about by ULA?
common upperstage
-
#52
by
PahTo
on 20 May, 2014 17:50
-
Is using the Centaur on the Delta IV something that has ever been talked about by ULA?
common upperstage
Not to be confused with ACES, which is notionally a common 5 meter upper stage...
Right?
-
#53
by
Lars_J
on 20 May, 2014 18:12
-
Is using the Centaur on the Delta IV something that has ever been talked about by ULA?
common upperstage
Will this common upper stage retain the current Centaur tank diameter, or will it be scaled up to 4m or at least Atlas V booster diameter?
-
#54
by
starsilk
on 20 May, 2014 20:31
-
Is using the Centaur on the Delta IV something that has ever been talked about by ULA?
common upperstage
not to be a party pooper or anything, but how is this plan for 'common avionics', 'common upperstage' etc consistent with having two redundant vehicles? I was under the impression that the whole point was to have two dissimilar vehicles which can accomplish (almost) the same task, in case one (cough, cough) has some sort of problem?
-
#55
by
simonbp
on 20 May, 2014 20:43
-
It doesn't, but then maintaining two different RL-10 upper stages with two different versions of RL-10 doesn't make a lot of economic sense, either.
Does anyone have a performance estimate for a Delta Medium/Medium+ with a dual engine Common Centaur?
-
#56
by
TrueGrit
on 20 May, 2014 22:47
-
Just to give some perspective... The Aerospace report from NASA wasn't received well from the industry in general. I would caution relying upon its conclusions as solid and only us it to gain light into the challenges to be faced. One only needs to look at the lack of consistent logic of the apparent RL10 chamber pressure problem vs. that hasn't been a problem for the commercial crew program.
-
#57
by
Lobo
on 20 May, 2014 22:51
-
While Delta IV certainly -could- launch commercial crew, I highly doubt it every would, for a few reasons.
1) Atlas V is the mostly likely EELV to carry commercial crew. I think a domestic replacement for RD-180 is more likely than Atlas V being retired and commercial crew flying on Delta IV, if there's an inturruption in access to Russian engines. If there's not, plans will proceed as usual.
2) F9 is a very likely candidate to carry commercial crew IMO, even if Atlas stays around with Russian engines. As Dr. Sowers pointed out, F9 lags behind Atlas V in BLEO performance due to their propellant choices. However, those propellant choices make it optimized for LEO performance. Commercial crew will go to LEO, so it's really the LV of choice for such a mission, even if SpaceX does not get the commercial crew contract. DC and CST-100 are both deisgned to be LV neutral, and SpaceX will gladly take SNC or Boeing's money to provide launches. Besides, NASA seems to like launching their astroanuts from their launch complex, and F9 can do that, where EELV's cannot. (without a MLP and VAB high bay, etc.)
Not to mention F9 will likley be cheaper than Atlas or Delta, even if fully expendable. Moreso if it reuses the booster.
-
#58
by
baldusi
on 20 May, 2014 22:55
-
Lobo, I agree, but this is the Delta IV for Commercial Crew thread.
-
#59
by
Lobo
on 20 May, 2014 23:27
-
Lobo, I agree, but this is the Delta IV for Commercial Crew thread.
I know...just explaining why it's an unlikley scenario, IMO. So it's on topic when discussing if Delta IV carrying commercial crew is a possibility.
Physically? Yes. Practically? No. and expained why I felt that way.
It was physically capable of taking Orion to the ISS for CxP, but we see how that worked out. ;-)