Author Topic: Safety analysis of HLVs vs. Ares I by NASA (from July 29, 2009 presentation)  (Read 17176 times)

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
Not sure if that has ever been discussed, but I looked at that one Cx presentation again that compares Ares I to various HLVs with a detailed LOM and LOC analysis.

Interestingly enough, the by far best choice after Ares I according to that analysis is the side-mounted directly-shuttle derived vehicle. DIRECT vehicles aren't in that analysis, but various EELV proposals are and Ares V is. Ares V is determined to be the least safe option.

In light of the "Dual Ares V Lite" options with crew on an Ares V Lite, I wonder how this analysis fits into it. Especially Ares V's extremely high LOM number due to "Loss of control during Frist Stage burn" is kind of worrisome.

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 7206
  • A spaceflight fan
  • London, UK
  • Liked: 806
  • Likes Given: 900
I would expect that a NASA-originated Ares-I safety analysis might be somewhat over-optimistic and slanted to support the vehicle of record.  Remember that NASA are somewhat wary of admitting that there are huge safety question-marks over the design (accoustic vibration and abort fratricide come to mind). 

I would suggest that the dangers of Ares-V-Lite and, by extension, any in-line D-SDLV, are probably somewhat exaggerated in seriousness by the method of analsys.  NASA's analysis seems to be that every possible problem with a vehicle is a mark against it vs. Ares-I (which is assumed to be very nearly without any significant failure modes) irrespective of how likely such a fault is.  So, you have a situation where every possible failure mode of a given system is counted as a likely LOM and possibly even LOC, even if there is almost no history whatsoever of that happening with the stated item in question.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline Downix

  • Senior Member
  • *****
  • Posts: 7082
  • Liked: 22
  • Likes Given: 1

In light of the "Dual Ares V Lite" options with crew on an Ares V Lite, I wonder how this analysis fits into it. Especially Ares V's extremely high LOM number due to "Loss of control during Frist Stage burn" is kind of worrisome.

I am in agreement here, it does make me worry, and has me thinking that NASA is, infact, aware of the base heating issue, and is worried about it as well.

At points I sometimes wonder if NASA management is intentionally setting itself up to fail.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 6
  • Likes Given: 0
Does side-mounting the engines almost completely remove any possible thrust imbalance issues? Because that's what these slides seem to imply.

I would like to know more about why Ares V suffers from such large thrust imbalance issues. It is fairly clear why a 3 core, 3 engine EELV would have thrust imbalance issues if one engine failed, but it is not very obvious to me why a single core design like Ares V is worse than a 3 core ELLV!
John

Offline Downix

  • Senior Member
  • *****
  • Posts: 7082
  • Liked: 22
  • Likes Given: 1
Does side-mounting the engines almost completely remove any possible thrust imbalance issues? Because that's what these slides seem to imply.

I would like to know more about why Ares V suffers from such large thrust imbalance issues. It is fairly clear why a 3 core, 3 engine EELV would have thrust imbalance issues if one engine failed, but it is not very obvious to me why a single core design like Ares V is worse than a 3 core ELLV!
It is partly due to an issue called ¨base heating¨, in short the RS-68 engine design, with its ablative nozzle, will overheat and fail before the first stage has finished reaching the required altitude.  One engine fails, your design goes imbalanced, loss of mission.

There is a very good post on this issue here:

http://forum.nasaspaceflight.com/index.php?topic=18139.msg494391#msg494391
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 6
  • Likes Given: 0
Base heating doesn't have anything directly to do with controllability under engine out conditions. The only relevance that base heating might have to controllability under engine out conditions is if base heating is driving engine layout to a point where the engines are spaced so widely that the core becomes uncontrollable. Quite frankly, if that is true then the engine layout is absurd.

Name another vehicle with a single core and >= 4 engines that becomes uncontrollable when one engine fails... I bet you can't!
John

Offline jml

  • Full Member
  • **
  • Posts: 280
  • Liked: 0
  • Likes Given: 0
There's gotta be more going on in these charts when it comes to "Loss of control during First Stage burn" that what's been discussed here so far.

The really perplexing question is why does side mount with 3 SSME have such a lower risk of "Loss of control during First Stage burn" than in-line Ares V with 6 RS-68B? One would think that side-mount aerodynamic loads would be more challenging than in-line, but that doesn't seem to be the basis of this metric.

Is the newer ablative-nozzle RS-68 with much less flight history so much riskier, or is the greater number of engines (and their arrangement) so much riskier? In either case, you'd kinda think that those metrics would be captured under the constrained and unconstrained engine failure risk components.

Does this metric measure perhaps measure something non-engine related like the avionics and control mechanisms needed to maintain stable flight through max-Q?

Is it a measure of 'abort black zones'? (not likely, cause those would be LOC issues more than LOM issues)

Or what exactly is it?

Base heating doesn't have anything directly to do with controllability under engine out conditions. The only relevance that base heating might have to controllability under engine out conditions is if base heating is driving engine layout to a point where the engines are spaced so widely that the core becomes uncontrollable. Quite frankly, if that is true then the engine layout is absurd.

Name another vehicle with a single core and >= 4 engines that becomes uncontrollable when one engine fails... I bet you can't!

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10560
  • Liked: 807
  • Likes Given: 40
I want to know *why* the In-Line SD-HLLV is missing from the analysis.

The answer would likely be quite revealing.

My guess is that they either wanted to try to pretend it doesn't exist (first they ignore you...) or that perhaps they were afraid to show the figures because it competes a little too well with Ares-I (...then the fight you...).

I would like to know which is true.

Ross.
« Last Edit: 11/05/2009 05:43 pm by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline dougkeenan

I want to know *why* the In-Line SD-HLLV is missing from the analysis.

The answer would likely be quite revealing.

My guess is that they either wanted to try to pretend it doesn't exist (first they ignore you...) or that perhaps they were afraid to show the figures because it competes a little too well with Ares-I (...then the fight you...).

I would like to know which is true.

Ross.

While we're waiting, did this chart affect your mood earlier?

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17939
  • Westphal, Nova Scotia
  • Liked: 659
  • Likes Given: 7688
There's gotta be more going on in these charts when it comes to "Loss of control during First Stage burn" that what's been discussed here so far.

The really perplexing question is why does side mount with 3 SSME have such a lower risk of "Loss of control during First Stage burn" than in-line Ares V with 6 RS-68B? One would think that side-mount aerodynamic loads would be more challenging than in-line, but that doesn't seem to be the basis of this metric.

Is the newer ablative-nozzle RS-68 with much less flight history so much riskier, or is the greater number of engines (and their arrangement) so much riskier? In either case, you'd kinda think that those metrics would be captured under the constrained and unconstrained engine failure risk components.


What's interesting is the 1st stage burn. Look at EELV vs. Ares V, they are almost identical. Why? The chose D4H, not Atlas V, so it is the RS-68 engine and/or the control method. That's where we concentrate.

Using this figure, we can make an even better argument for Direct, using side-mount as a comparison due to engines.

Offline Mark S

  • Senior Member
  • *****
  • Posts: 2284
  • Dallas, TX
  • Liked: 396
  • Likes Given: 80
I want to know *why* the In-Line SD-HLLV is missing from the analysis.

The answer would likely be quite revealing.

My guess is that they either wanted to try to pretend it doesn't exist (first they ignore you...) or that perhaps they were afraid to show the figures because it competes a little too well with Ares-I (...then the fight you...).

I would like to know which is true.

Ross.

NASA has done everything in its power to discredit, ignore, bad-mouth, insult, and fight DIRECT since its inception.

Only a true competitor would engender such enmity.  If DIRECT was as bad as they say, it never would have been included in the Augustine analyses (such as it was).

And those charts were generated by NASA, not Aerospace Corp.  So of course they left DIRECT/inline/NLS off.  "La la la, I can't hear you..."

Mark S.

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10560
  • Liked: 807
  • Likes Given: 40
While we're waiting, did this chart affect your mood earlier?

Nope.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline Blackout

  • Member
  • Posts: 96
  • Liked: 36
  • Likes Given: 1
I don't know how NASA scored these but I suspect that the more engines you have the worse the LOM and LOC numbers are (for NASA purposes of course, not reality).  That would explain why Ares V scored the worst if it is true.

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
I want to know *why* the In-Line SD-HLLV is missing from the analysis.

The answer would likely be quite revealing.

My guess is that they either wanted to try to pretend it doesn't exist (first they ignore you...) or that perhaps they were afraid to show the figures because it competes a little too well with Ares-I (...then the fight you...).

I would like to know which is true.

Ross.

NASA has done everything in its power to discredit, ignore, bad-mouth, insult, and fight DIRECT since its inception.

Only a true competitor would engender such enmity.  If DIRECT was as bad as they say, it never would have been included in the Augustine analyses (such as it was).

And those charts were generated by NASA, not Aerospace Corp.  So of course they left DIRECT/inline/NLS off.  "La la la, I can't hear you..."

Mark S.

This isn't new information (I said it's from a July 29 presentation). I just wanted to highlight that NASA will have a rather big problem in justifying a switch from Ares I to something like Ares V Lite Dual launch in light of the analysis they have done just recently.

I mean, their analysis says Ares V's LOC numbers are only about 2 to 3 times better than Shuttle. That's a farcry from where Cx aims to be. Having said that, unless they go back to their LOM/LOC analysis and say "oh well, it wasn't correct back then, everything is different now", they won't be able to back up their decision to move away from Ares I to a Ares V Dual Lite scenario.

Whether their high "Loss of Control during First Stage failure" LOM and LOC numbers are due to RS-68B or not is another question, the odd thing is, side-mount doesn't have that kind of high LOM and LOC numbers, it has a big problem for "Contained engine failure stage 1" but that's probably more of an engineering challenge than an actual problem at the end.

Offline MP99

This isn't new information (I said it's from a July 29 presentation). I just wanted to highlight that NASA will have a rather big problem in justifying a switch from Ares I to something like Ares V Lite Dual launch in light of the analysis they have done just recently.

I mean, their analysis says Ares V's LOC numbers are only about 2 to 3 times better than Shuttle. That's a farcry from where Cx aims to be. Having said that, unless they go back to their LOM/LOC analysis and say "oh well, it wasn't correct back then, everything is different now", they won't be able to back up their decision to move away from Ares I to a Ares V Dual Lite scenario.

Whether their high "Loss of Control during First Stage failure" LOM and LOC numbers are due to RS-68B or not is another question, the odd thing is, side-mount doesn't have that kind of high LOM and LOC numbers, it has a big problem for "Contained engine failure stage 1" but that's probably more of an engineering challenge than an actual problem at the end.

Launch risk is a tiny percentage of total mission risk.

If additional mass on the CLV launch allows redundant systems to be added to, or added back to, Orion then maybe total pLOC can be reduced.

cheers, Martin
« Last Edit: 11/07/2009 06:36 am by MP99 »

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0

Launch risk is a tiny percentage of total mission risk.


That's not entirely correct. A. It depends on the mission and B. it of course depends on the LOC numbers of the vehicle you are using.

STS LOC numbers appear to be unacceptable. Right now they are 1:65 for the whole mission (although the mission is LEO only and only involves one docking) and 1:130 for ascent (launch risk equivalent).

If your vehicle has a risk of LOC on ascent of 1:3000 and you are doing a complicated mission (e.g. extended lunar stay or Mars mission), thn your vehicle ascent risk is probably only a fraction of the mission risk. However, once you get down to the numbers NASA's analysis above quotes (LOM being about 1:150 for Ares V and LOC about 1:400 if not less) and we are talking about less complicated missions, ascent becomes a significant part of the overall LOC risk and thus unacceptable.

There is a reason why NASA is aiming for at least one magnitude better LOC numbers for Ares I compared to the Shuttle.
« Last Edit: 11/07/2009 06:50 am by alexSA »

Offline meiza

  • Expert
  • Senior Member
  • *****
  • Posts: 3067
  • Where Be Dragons
  • Liked: 5
  • Likes Given: 3
Seems the LOC number doesn't care if there's a liquid or solid underneath. It matters a lot in case of an abort!

Offline MP99


Launch risk is a tiny percentage of total mission risk.


That's not entirely correct. A. It depends on the mission and B. it of course depends on the LOC numbers of the vehicle you are using.

<snipped>

If your vehicle has a risk of LOC on ascent of 1:3000 and you are doing a complicated mission (e.g. extended lunar stay or Mars mission), thn your vehicle ascent risk is probably only a fraction of the mission risk.

Yes, poor wording on my part.

I was specifically referring to the 1:3000 Ares I LOC compared to the target Lunar Sortie mission LOC from the CARD (ref [Ex-0011-05], if you have access).

Jupiter's LOC is better than 1:1000, which would not require a large improvement in other areas to maintain the same overall Sortie mission risk.


Quote
However, once you get down to the numbers NASA's analysis above quotes (LOM being about 1:150 for Ares V and LOC about 1:400 if not less)

A LOC of 1:400 would, indeed, be a different matter.

cheers, Martin

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0

Jupiter's LOC is better than 1:1000, which would not require a large improvement in other areas to maintain the same overall Sortie mission risk.


LOC numbers are hard to come up with in most cases and at the end they mostly turn out to be wrong.

Anyways, according to NASA's analysis, Jupiter's LOC will probably not be much better than Ares V's LOC numbers. Why should they be? The vehicles' architecture is fairly similar - 2 SRBs, one main cryogenic core tank, multiple core engines, one upper stage with one or several upper stage engines.

In any event, my point still is - if NASA were to look at an Ares V Lite Dual architecture seriously, they would have to go back and look at their analysis and say "oh, doesn't apply or we got that wrong back then" OR they would have to acknowledge that their new way forward is a lot less safe (which would be a big political problem).

Offline MP99

These are figures from DIRECT_Summary_v2.0.2.pdf (ie RS-68) and http://www.launchcomplexmodels.com/Direct/documents/DIRECT_ISDC_2009.pdf (DIRECT 3.0, ie SSME - 2nd & 3rd image).

cheers, Martin

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
These are figures from DIRECT_Summary_v2.0.2.pdf (ie RS-68) and http://www.launchcomplexmodels.com/Direct/documents/DIRECT_ISDC_2009.pdf (DIRECT 3.0, ie SSME - 2nd & 3rd image).

cheers, Martin

I cannot say anything about LOM and LOC numbers for Jupiter vehicles, but the numbers for Ares I and V as well as the Shuttle numbers look very wrong indeed. They are so completely different from the numbers NASA engineering teams have come up with after pretty long analysis, I just can't take them for real.

Is there any more detailed data anywhere on how the DIRECT team arrived for the LOM and LOC figures for Ares I and V? Maybe a detailed probability risk approach as outlined in the first post to this thread?

Offline jml

  • Full Member
  • **
  • Posts: 280
  • Liked: 0
  • Likes Given: 0
These are figures from DIRECT_Summary_v2.0.2.pdf (ie RS-68) and http://www.launchcomplexmodels.com/Direct/documents/DIRECT_ISDC_2009.pdf (DIRECT 3.0, ie SSME - 2nd & 3rd image).

cheers, Martin

I cannot say anything about LOM and LOC numbers for Jupiter vehicles, but the numbers for Ares I and V as well as the Shuttle numbers look very wrong indeed. They are so completely different from the numbers NASA engineering teams have come up with after pretty long analysis, I just can't take them for real.

Is there any more detailed data anywhere on how the DIRECT team arrived for the LOM and LOC figures for Ares I and V? Maybe a detailed probability risk approach as outlined in the first post to this thread?

Dude, you're kidding, right? Guess who came up with DIRECT's numbers and what methodology they used, and what other vehicles those folks do LOM/LOC numbers for as part of their day job in Alabama. Hint - it wasn't Ross or Chuck or the Metschans who came up with these numbers. You need to do some reading in the Direct threads to understand the history of this.

Of course, you might also try to understand Jeff Greason's words about the usefulness of PRA's on paper rockets.

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0

Dude, you're kidding, right? Guess who came up with DIRECT's numbers and what methodology they used, and what other vehicles those folks do LOM/LOC numbers for as part of their day job in Alabama. Hint - it wasn't Ross or Chuck or the Metschans who came up with these numbers. You need to do some reading in the Direct threads to understand the history of this.

I am not sure if you realize that there are more than 60 engineers (people who are allegedly working or have worked on DIRECT) in the US spaceflight program?

Fact remains fact. The difference of LOM and LOC numbers presented is so glaringly different, an explanation would be nice. And the fact is, NASA did provide a detailed overview of how they derived their estimates, and I haven't seen anything remotely comparable in detail by the DIRECT team. Sorry to say, but compared to NASA's published detailed analysis, their numbers for Ares I and Ares V look like having been just picked out of a hat.

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 6
  • Likes Given: 0
I am a bit dubious about the Jupiter LOC statistics -- the Jupiter rockets have more engines than Ares I therefore LOC ought to be worse (although the high max Q could come into play etc.). However at the same time there have been so many different LOC figures for Ares I from 1 in ~1200 to above 3000 that it's pretty clear that NASA has no idea how safe Ares I is; complaining that the LOC/LOM figures don't match NASA's current values isn't fair as NASA has changed methodologies. I don't have any issues with the Ares I/V numbers though.

I'm not sure why you are complaining about the Shuttle figures, I've heard everything from 1 in 64 to 1 in 240. Although ISS means that LOM => LOC doesn't necessarily hold (in practice I don't think this will actually improve figures very much though).
« Last Edit: 11/08/2009 09:12 am by madscientist197 »
John

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 6
  • Likes Given: 0
NASA did provide a detailed overview of how they derived their estimates

Point of interest: If you look at the ESAS appendicies it is clear that some of the probabilities were essentially picked out of a hat -- a reflection of the prejudices of the authors. The engine failure analysis was surprisingly shallow (in the case of the RD-180, literally imagined!)
« Last Edit: 11/08/2009 09:08 am by madscientist197 »
John

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
However at the same time there have been so many different LOC figures for Ares I from 1 in ~1200 to above 3000 that it's pretty clear that NASA has no idea how safe Ares I is; complaining that the LOC/LOM figures don't match NASA's current values isn't fair as NASA has changed methodologies.

I have never seen a NASA estimate for the current Ares I architecture of 1: 1200. NASA has been consistently in the 1:3000 area according to their analysis.

Quote
I'm not sure why you are complaining about the Shuttle figures, I've heard everything from 1 in 64 to 1 in 240. Although ISS means that LOM => LOC doesn't necessarily hold (in practice I don't think this will actually improve figures very much though).

Pinpointing Shuttle LOM and LOC figures isn't possible. That's why NASA always provides a range of probability for those figures. If however someone were to use a specific figure in a graph, it should be the historical figures provided. That would be 1 in 64 for ascent (if foam shedding damage is considered an ascent event) or 1 in 128. But it shouldn't be an arbitrary number like 1 in 200.

Anyways, I just said that it's quite odd that DIRECT comes up with LOM and LOC numbers for Ares I and Ares V which are (in aggregate) nearly a magnitude apart from the one's the dedicated NASA team who did a detailed analysis came up with (interestingly enough Ares I figures are up to a factor of 3 lower, while Ares V figures are up to a factor 4 higher).

Offline Analyst

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 4
  • Likes Given: 20
All this LOM/LOC ex ante predictions are much more an art than a science. Allowing very different opinions to enter into it. It may be useful in comparing different vehicles designs as long as you use the same methology. But even this is still a kind of art. You have to assume things, which has to be based on something. On what? ...

The only LOM/LOC numbers worth the paper they are written on are the ex post ones. Sorry for the guys who calculate these things.

Which makes the whole thread a lot less interesting.

Analyst

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17939
  • Westphal, Nova Scotia
  • Liked: 659
  • Likes Given: 7688
However at the same time there have been so many different LOC figures for Ares I from 1 in ~1200 to above 3000 that it's pretty clear that NASA has no idea how safe Ares I is; complaining that the LOC/LOM figures don't match NASA's current values isn't fair as NASA has changed methodologies.

I have never seen a NASA estimate for the current Ares I architecture of 1: 1200.

I have & can back up his statement. It's on a presentation somewhere...

Offline Antares

  • ABO^2
  • Senior Member
  • *****
  • Posts: 5181
  • Done arguing with amateurs
  • Liked: 371
  • Likes Given: 228
The only LOM/LOC numbers worth the paper they are written on are the ex post ones. Sorry for the guys who calculate these things.

Even then, they a still only comparative (and suitable for where to focus upgrade efforts).  They are never predictive or absolute.  They only account for random hardware failures, not for process failures which dominate real-life.
« Last Edit: 11/08/2009 03:16 pm by Antares »
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
However at the same time there have been so many different LOC figures for Ares I from 1 in ~1200 to above 3000 that it's pretty clear that NASA has no idea how safe Ares I is; complaining that the LOC/LOM figures don't match NASA's current values isn't fair as NASA has changed methodologies.

I have never seen a NASA estimate for the current Ares I architecture of 1: 1200.

I have & can back up his statement. It's on a presentation somewhere...

If you find it at some point, I would appreciate if you could post it here.

Thanks.

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
I do find some of the safety claims they make for Ares I dubious at best.
None of the hardware has flown so until then any calculations are at best an educated guess.

Other issues I have is the assumption a passively stable reentry vehicle that must shed a SM is naturally going to be much safer then one with active guidance but under goes no configuration changes for reentry.
Real world data Shuttle vs Soyuz during reentry seems to suggest the opposite.
Guidance and control systems have been proven to be so reliable that they probably would not even contribute to 1% of LOC/LOM events.
Every time you fly on an airliner you are trusting your life to the exact same type of technology to work and to continue working even with multiple failures.

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17939
  • Westphal, Nova Scotia
  • Liked: 659
  • Likes Given: 7688

If you find it at some point, I would appreciate if you could post it here.

Thanks.

Not the one I'm looking for, as it is 1:1200 for LOM, but considering the state of things, it's definitely a good read for what might be things to come...

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17939
  • Westphal, Nova Scotia
  • Liked: 659
  • Likes Given: 7688
Here's another one of those 'theoretical' models on safety numbers. Here we see the 'steep learning curve' of a new SRB, from first flight of an SRB to post-Challenger. AFAIK, a 5-segment is a new motor. If they go with disposable cores, then they lose the safety numbers.

EDIT: see page 15.
« Last Edit: 11/08/2009 04:42 pm by robertross »

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17939
  • Westphal, Nova Scotia
  • Liked: 659
  • Likes Given: 7688
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Offline Analyst

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 4
  • Likes Given: 20
The only LOM/LOC numbers worth the paper they are written on are the ex post ones. Sorry for the guys who calculate these things.

Even then, they a still only comparative (and suitable for where to focus upgrade efforts).  They are never predictive or absolute.  They only account for random hardware failures, not for process failures which dominate real-life.

I second this. Nothing predicts the future, nor is anything absolute.

Analyst

Offline Analyst

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 4
  • Likes Given: 20
Other issues I have is the assumption a passively stable reentry vehicle that must shed a SM is naturally going to be much safer then one with active guidance but under goes no configuration changes for reentry.
Real world data Shuttle vs Soyuz during reentry seems to suggest the opposite.
Guidance and control systems have been proven to be so reliable that they probably would not even contribute to 1% of LOC/LOM events.
Every time you fly on an airliner you are trusting your life to the exact same type of technology to work and to continue working even with multiple failures.

Yup. I think the same.

And now lets talk about parachute deploy, which is claimed to be a non issue (and you don't need wings!). Some dead Soyuz crewmembers, the Apollo 15 crew and the Ares 1-X first stage may think different.

Analyst

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0
Some dead Soyuz crewmembers,

Which ones would that be.

Komarov died because of a faulty pressure sensor. The main chute failure was just a consequence of the sensor failure.

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6404
  • Liked: 529
  • Likes Given: 67
Some dead Soyuz crewmembers,

Which ones would that be.

Komarov died because of a faulty pressure sensor. The main chute failure was just a consequence of the sensor failure.

I'm sure that made a big difference to Komarov. The point is that the pressure sensor is part of the overall chute deployment system and if it fails the whole thing fails.
JRF

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6807
  • Lafayette/Broomfield, CO
  • Liked: 3987
  • Likes Given: 1681
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Even if there were 4 launches per year, over 50 years you would have 200 launches.  I really doubt that with a 100% turnover of all the engineering staff over that time (at least once), various supplier changes as companies come and go, etc, that you're really going to be able to avoid accidents caused by loss of institutional knowledge. 

And that's assuming that somehow the rookie NASA team designing Ares-I is going to be able to pull of delivering a vehicle that is 8x more reliable than any other ELV that has flown...

~Jon
« Last Edit: 11/10/2009 03:39 pm by jongoff »

Offline William Barton

  • Senior Member
  • *****
  • Posts: 3487
  • Liked: 8
  • Likes Given: 0
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Even if there were 4 launches per year, over 50 years you would have 200 launches.  I really doubt that with a 100% turnover of all the engineering staff over that time (at least once), various supplier changes as companies come and go, etc, that you're really going to be able to avoid accidents caused by loss of institutional knowledge. 

And that's assuming that somehow the rookie NASA team designing Ares-I is going to be able to pull of delivering a vehicle that is 8x more reliable than any other ELV that has flown...

~Jon

It might be interesting to speculate on how R-7 escaped that fate. There can't be too many original enginneers left on the team since the early 1950s.

Offline Downix

  • Senior Member
  • *****
  • Posts: 7082
  • Liked: 22
  • Likes Given: 1
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Even if there were 4 launches per year, over 50 years you would have 200 launches.  I really doubt that with a 100% turnover of all the engineering staff over that time (at least once), various supplier changes as companies come and go, etc, that you're really going to be able to avoid accidents caused by loss of institutional knowledge. 

And that's assuming that somehow the rookie NASA team designing Ares-I is going to be able to pull of delivering a vehicle that is 8x more reliable than any other ELV that has flown...

~Jon

It might be interesting to speculate on how R-7 escaped that fate. There can't be too many original enginneers left on the team since the early 1950s.
Constant use, constant training, constant flights.

Same reason why you can still get a car built today when Fords original workers all are dead or retired.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6807
  • Lafayette/Broomfield, CO
  • Liked: 3987
  • Likes Given: 1681
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Even if there were 4 launches per year, over 50 years you would have 200 launches.  I really doubt that with a 100% turnover of all the engineering staff over that time (at least once), various supplier changes as companies come and go, etc, that you're really going to be able to avoid accidents caused by loss of institutional knowledge. 

And that's assuming that somehow the rookie NASA team designing Ares-I is going to be able to pull of delivering a vehicle that is 8x more reliable than any other ELV that has flown...

~Jon

It might be interesting to speculate on how R-7 escaped that fate. There can't be too many original enginneers left on the team since the early 1950s.

As Downix suggested, high flight rate helps keep people trained.  But as it is, they did have several near failures in recent years that could've turned fatal quite easily.

~Jon

Offline alexSA

  • Full Member
  • *
  • Posts: 129
  • Liked: 0
  • Likes Given: 0

As Downix suggested, high flight rate helps keep people trained.  But as it is, they did have several near failures in recent years that could've turned fatal quite easily.


These were problems with the spacecraft, not with the LV.

The LV is a rather solid one, the Soyuz spacecraft has always been a flawed one - both fatal in-flight accidents were due to manufacturing errors on the Soyuz spacecraft, not on the LV.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 37440
  • Cape Canaveral Spaceport
  • Liked: 21450
  • Likes Given: 428

As Downix suggested, high flight rate helps keep people trained.  But as it is, they did have several near failures in recent years that could've turned fatal quite easily.


These were problems with the spacecraft, not with the LV.
 

No, there have been booster problems in the last ten years, see Foton.

Offline William Barton

  • Senior Member
  • *****
  • Posts: 3487
  • Liked: 8
  • Likes Given: 0
I think I know where I had seen this...it was from a Direct thread.

I can't copy & paste on this stupid thing, but do a search on here for:
Ares 1:2000

There are two related. One is on the Direct thread #2, and describes how NASA changed the rules, the other has a chart made by Direct.

Again, it's all theoretical. A 1:2000 could have a failure at launch #3, and nothing for the remaining 1997 launches. Are we going to make 2000 launches with the same vehicle? Never.

Even if there were 4 launches per year, over 50 years you would have 200 launches.  I really doubt that with a 100% turnover of all the engineering staff over that time (at least once), various supplier changes as companies come and go, etc, that you're really going to be able to avoid accidents caused by loss of institutional knowledge. 

And that's assuming that somehow the rookie NASA team designing Ares-I is going to be able to pull of delivering a vehicle that is 8x more reliable than any other ELV that has flown...

~Jon

It might be interesting to speculate on how R-7 escaped that fate. There can't be too many original enginneers left on the team since the early 1950s.
Constant use, constant training, constant flights.

Same reason why you can still get a car built today when Fords original workers all are dead or retired.

Outsourcing overseas helps too. After Motorola ceased production, there were no longer any workers in the US who could manufacture TVs, but there were still plenty of TVs in the stores.

Offline William Barton

  • Senior Member
  • *****
  • Posts: 3487
  • Liked: 8
  • Likes Given: 0

As Downix suggested, high flight rate helps keep people trained.  But as it is, they did have several near failures in recent years that could've turned fatal quite easily.


These were problems with the spacecraft, not with the LV.
 

No, there have been booster problems in the last ten years, see Foton.

Interesting that it's been in recent years. Everybody suddenly get a gold watch ten years ago? More likely to do with political and economic changes since 1989.

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0