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#2200
by
sivodave
on 22 Aug, 2011 13:15
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Hi all.
This time a question about the SSME: how did they get built? I meant, which is the process flow for which they are finally assembled? How long does it last?
Any idea where I can get good information on this? Maybe Rocketdyne itself?
Thanks
Davide
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#2201
by
DarkenedOne
on 22 Aug, 2011 15:02
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
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#2202
by
Jim
on 22 Aug, 2011 15:23
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
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#2203
by
Wepush
on 22 Aug, 2011 15:38
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Build of the engine components takes years, five or six for some.
Engine assembly, after all the parts are built, can be completed in as little as a month, but usually happened over something closer to six months, while other work was being done too.
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#2204
by
DarkenedOne
on 22 Aug, 2011 17:01
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
Why is the inspection necessary. Practically all other rockets seem to do fine without it.
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#2205
by
Jim
on 22 Aug, 2011 17:25
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
Why is the inspection necessary. Practically all other rockets seem to do fine without it.
Because it is manrated and post flight inspection is one of the ways to ensure that there are no bad trends.
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#2206
by
sivodave
on 22 Aug, 2011 19:18
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[quote+Webpush]Build of the engine components takes years, five or six for some.
Engine assembly, after all the parts are built, can be completed in as little as a month, but usually happened over something closer to six months, while other work was being done too. [/quote]
Hi webpush. Thanks for the reply. I was also interested in knowing, roughly the assembly sequence, from the first two elements assembled together to the last one at engine completion. Is there any document around about this?
Thanks
Davide
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#2207
by
wolfpack
on 23 Aug, 2011 17:00
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
If the flight manifest had ever achieved anywhere near the original goal of 50 flights per year, then recovery was the best option. Cheaper to refurbish a rotating set of, say, 12 booster pairs than to buy 100 of them each year. Of course, that never happened.
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#2208
by
JayP
on 23 Aug, 2011 17:10
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
If the flight manifest had ever achieved anywhere near the original goal of 50 flights per year, then recovery was the best option. Cheaper to refurbish a rotating set of, say, 12 booster pairs than to buy 100 of them each year. Of course, that never happened.
Actually, it's the opposite. With a higher flight rate, The per flight recovery costs (SRB ship opperations, disassembly and shipping the segments, refurbishing them, etc.) would be the same, but the cost of producing segments from scratch would decrease somewhat as economies of scale began to apply. Reusability as a cost saver was always a misguided concept.
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#2209
by
baldusi
on 23 Aug, 2011 17:21
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
If the flight manifest had ever achieved anywhere near the original goal of 50 flights per year, then recovery was the best option. Cheaper to refurbish a rotating set of, say, 12 booster pairs than to buy 100 of them each year. Of course, that never happened.
If post flight inspection was a fundamental requirement of human rating, and if those where the big cost of recovery, I would be tempted to think that it couldn't be lowered by bigger scale of production as easily as manufacturing. May be someone could enlighten me?
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#2210
by
JayP
on 23 Aug, 2011 17:36
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If post flight inspection was a fundamental requirement of human rating, and if those where the big cost of recovery, I would be tempted to think that it couldn't be lowered by bigger scale of production as easily as manufacturing. May be someone could enlighten me?
Post flight inspection was never a "fundamental requirement of human rating" of a launch vehicle. In the case of the STS SRBs, they were originally designed for recovery. Analysis done after several years of flying showed that the cost of recovering and refurbishing was about the same as building new hardware for flight and had the ADDED benefit of providing an opportunity to study hardware that had flown to establish a family history(especially since the hardware in question had experienced a catostrophic failure - This was after 51L). Given that, the question of paying for redesigning and recertificating the booster as expendables was not viable.
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#2211
by
baldusi
on 23 Aug, 2011 17:42
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If post flight inspection was a fundamental requirement of human rating, and if those where the big cost of recovery, I would be tempted to think that it couldn't be lowered by bigger scale of production as easily as manufacturing. May be someone could enlighten me?
Post flight inspection was never a "fundamental requirement of human rating" of a launch vehicle. In the case of the STS SRBs, they were originally designed for recovery. Analysis done after several years of flying showed that the cost of recovering and refurbishing was about the same as building new hardware for flight and had the ADDED benefit of providing an opportunity to study hardware that had flown to establish a family history(especially since the hardware in question had experienced a catostrophic failure - This was after 51L). Given that, the question of paying for redesigning and recertificating the booster as expendables was not viable.
Is any public documentation available on this subject?
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#2212
by
wolfpack
on 23 Aug, 2011 17:45
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The Shuttle uses SRB that are recoverable. The Ares I and V were to use extended versions of these SRBs. What I have been wondering is whether or not recovery of these SRB is cost effective? Are it cheaper to recover them than it is to simply use expendables, and if so how much cheaper? Lastly if it is more cost-effective than why are they not used by any other launch vehicles today?
This question has been asked before, so feel free to just give me a link if you do not want to fully explain it to me.
Recovery is not for cost but for post flight inspection.
If the flight manifest had ever achieved anywhere near the original goal of 50 flights per year, then recovery was the best option. Cheaper to refurbish a rotating set of, say, 12 booster pairs than to buy 100 of them each year. Of course, that never happened.
If post flight inspection was a fundamental requirement of human rating, and if those where the big cost of recovery, I would be tempted to think that it couldn't be lowered by bigger scale of production as easily as manufacturing. May be someone could enlighten me?
If post flight inspection were a requirement of human rating, then the darn things should have been decertified in 1984! Ignoring the blowby evidence shows that that wasn't the case.
IMO, an edict from on high that never again shall solids be used in human spaceflight would be a good thing. Maybe we could get some funding for stacking the remaining casings and letting RSO have some fun on the 4th of July!
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#2213
by
Jim
on 23 Aug, 2011 18:58
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Post flight inspection was never a "fundamental requirement of human rating" of a launch vehicle.
It is for segmented solids
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#2214
by
alk3997
on 23 Aug, 2011 22:17
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...
If post flight inspection were a requirement of human rating, then the darn things should have been decertified in 1984! Ignoring the blowby evidence shows that that wasn't the case.
IMO, an edict from on high that never again shall solids be used in human spaceflight would be a good thing. Maybe we could get some funding for stacking the remaining casings and letting RSO have some fun on the 4th of July!
You realize, of course, that the RSRMs were one of the most reliable part of the vehicle by retirement? It's really an engineering question - would you rather have a part that has less chance of failure but if it fails there are no benign modes (most catastrophic). Or, would you rather have a part that has more chance of failure but the failure modes range from benign to catastrophic. Liquids engines have many more moving parts and many more ways of failing than segmented solids.
Of course, cost factors into this discussion as well. Environmental also factors in (those who have been "lucky" enough to breathe the air around 39A/B after a launch can tell you what SRB exhaust mixed with water is like). But, a blanket statement condemming solids doesn't do anyone any good.
Andy
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#2215
by
vsrinivas
on 23 Aug, 2011 22:57
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In one of the ALT videos, the one where GPC 2 sync is lost, what is 'Go for mode 203'?
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#2216
by
DaveS
on 24 Aug, 2011 00:38
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What is the distance between each "bay" of the orbiter payload bay?
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#2217
by
wolfpack
on 24 Aug, 2011 01:17
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#2218
by
alk3997
on 24 Aug, 2011 01:55
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...
If post flight inspection were a requirement of human rating, then the darn things should have been decertified in 1984! Ignoring the blowby evidence shows that that wasn't the case.
IMO, an edict from on high that never again shall solids be used in human spaceflight would be a good thing. Maybe we could get some funding for stacking the remaining casings and letting RSO have some fun on the 4th of July!
You realize, of course, that the RSRMs were one of the most reliable part of the vehicle by retirement? It's really an engineering question - would you rather have a part that has less chance of failure but if it fails there are no benign modes (most catastrophic). Or, would you rather have a part that has more chance of failure but the failure modes range from benign to catastrophic. Liquids engines have many more moving parts and many more ways of failing than segmented solids.
Of course, cost factors into this discussion as well. Environmental also factors in (those who have been "lucky" enough to breathe the air around 39A/B after a launch can tell you what SRB exhaust mixed with water is like). But, a blanket statement condemming solids doesn't do anyone any good.
Andy
A bit sour? 
Liquids are proven, and can be shut down prior to failure by well designed avionics software. Solids are awesome for cargo into LEO. I just wouldn't use them for HSF. A failing solid is a bomb. A failing liquid is probably only going to send turbopump shrapnel tangentially away from its axis of rotation.
Not sour one bit - I don't have a pony in this race.
However, you might want to go back and look at the history of liquid engine failures before stating that they fail benignly. There are many examples of one engine taking out another. Either type of engine/motor (solid or liquid) carries risk or else we would have never needed to put in many of the Shuttle contingency modes. To dismiss one type without analyzing the risk of the other is not good program management or engineering. I'd also point out that we had 5 pad aborts and 1 ATO, each of which was caused by a shutdown of an SSME (contained SSME failure - even if it was just a sensor). There were hazards with each abort but crew and vehicle survived. There was 1 failure of the SRM (prior to being redesigned) and obviously we know that result. However, the 51F ATO could have easily ended up as a loss of vehicle had a second engine also shutdown (which it came very close to doing).
There are some liquid engine failures that occur so fast that not even the best avionics can prevent the issue (such as a fuel manifold that ruptures very quickly).
Again, if you would like to dismiss an entire technology because of one (yes catastrophic) failure 25 years ago, then you're dismissing a valuable booster. Seems silly to me, but that's your choice.
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#2219
by
Jim
on 24 Aug, 2011 02:51
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Liquids do fail benignly. They give enough notice to abort.
As for valuable technology, SRB is not, we can do without.
The rest of your points are actually in favor of liquids and especially, your use of 51-F. The engine "failure" was benign. And if there was another engine shutdown, crew loss would not be due to the engines, but to the program for not having an intact abort system.
