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Thought Experiment: Man Rating OmegA
by
JEF_300
on 05 Nov, 2018 19:54
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This idea popped into my brain and now I need answers. If, for whatever reason, it was decided in the next few years to attempt to man-rate Omega, what would that look like? How well suited is Omega to lofting crews? What would be the major roadblocks? How might these roadblocks be solved?
Edited to add note: Try to think like an engineer, not a critic. This thread is NOT about whether or not Omega should be man-rated. It's is a mental an engineering challenge to figure out what would be required to man-rate it.
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#1
by
JonathanD
on 05 Nov, 2018 20:07
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Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.
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#2
by
ncb1397
on 05 Nov, 2018 20:42
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Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.
Doesn't seem to be a problem with escape systems on fighter jets carrying solid ordnance. And the SRBs stayed remarkably intact during Challenger when the liquid fuel tank exploded. OmegA is a four stage design including boosters, meaning each stage doesn't have to be built for minimal dry weight and maximum velocity contribution compared to 1/2/3 stage designs. The Shuttle SRBs being over-engineered vs the ET is why they stayed together and the ET didn't.
So, one modification for man-rating would be making sure the new segments are as strong as the older steel casings even though there is no re-use.
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#3
by
vaporcobra
on 05 Nov, 2018 21:12
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It's a horrible, terrible, wildly unsafe idea. We should all be thankful that Ares I was cancelled after just one flight - performing crew launches with an all-solid boost stage is about as close to testing fate as one can get, even after you solve the problem that solids (at least Shuttle-style formulations) produce vibrations (technically thrust oscillations) strong enough to kill or maim astronauts.
NASA's solution was quite literally giant shock absorbers, which gives one a sense of just how stupid an all-solid boost stage on a crewed rocket really is.
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#4
by
TomH
on 06 Nov, 2018 01:38
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Well, if you went with the OmegaA Heavy S1 (Castor 1200 and six GEM 63s), wouldn't you simply have a very souped up S1 for the Ares I?
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#5
by
ChrisWilson68
on 06 Nov, 2018 01:51
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Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.
Doesn't seem to be a problem with escape systems on fighter jets carrying solid ordnance. And the SRBs stayed remarkably intact during Challenger when the liquid fuel tank exploded. OmegA is a four stage design including boosters, meaning each stage doesn't have to be built for minimal dry weight and maximum velocity contribution compared to 1/2/3 stage designs. The Shuttle SRBs being over-engineered vs the ET is why they stayed together and the ET didn't.
So, one modification for man-rating would be making sure the new segments are as strong as the older steel casings even though there is no re-use.
Watch this video of the Delta 2 failure in 1997:
Fighter jets aren't using the solid ordinance as their primary propulsion, so it's not a comparable situation. If a casing lets go while a booster is firing, the effect is very much different from what happens if a fighter jet explodes and the missiles under the wing burn in the fire.
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#6
by
IanThePineapple
on 06 Nov, 2018 02:06
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Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.
I mean SLS will have two giant SRBs for the first 2 minutes or so of its flight...
Not saying OmegA is better, just a potential issue with SLS
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#7
by
JEF_300
on 06 Nov, 2018 02:16
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So what things could you do to fix the solid-exhaust v/s parachute problem?
1. Require a more powerful abort system, that can propel the spacecraft further from the vehicle.
2. Require some sort of mechanism to extinguish the motors. *
3. Set a rule that only spacecraft without parachutes, like Dreamchaser, can fly on Omega
* Very difficult and expensive, but NASA engineers in the 70s thought it was possible
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#8
by
ChrisWilson68
on 06 Nov, 2018 02:44
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So what things could you do to fix the solid-exhaust v/s parachute problem?
1. Require a more powerful abort system, that can propel the spacecraft further from the vehicle.
2. Require some sort of mechanism to extinguish the motors. *
3. Set a rule that only spacecraft without parachutes, like Dreamchaser, can fly on Omega
* Very difficult and expensive, but NASA engineers in the 70s thought it was possible
It's not solid exhaust that's the issue. It's burning pieces of a solid boost that has blown itself apart that is the issue. So extinguishing the motor is not an option.
Please see the video upthread of the 1997 Delta 2 explosion.
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#9
by
jaxon9182
on 06 Nov, 2018 03:08
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Solids get a bad rap but they don't deserve it, if Challenger was scrubbed and didn't end up exploding solids would be viewed differently. Oscillations are a problem, but far from insurmountable, the burning fuel flying everywhere is the big issue with a solid core stage. The LAS for Orion is capable of safely launching Orion away from an exploding SRB, and would work (obviously with some modifications) on OmegA. It was designed for Ares 1, and they haven't changed it for SLS. The other thing to consider would be launching Dreamchaser, SNC still wants to fly crew on it, they could launch the cargo version on OmegA first, and it doesn't have a LAS so they're probably screwed if the rocket blows up in such a manner anyway. Solid motor hate is far to prevalent
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#10
by
vaporcobra
on 06 Nov, 2018 03:52
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Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.
I mean SLS will have two giant SRBs for the first 2 minutes or so of its flight...
Not saying OmegA is better, just a potential issue with SLS
It was also a massive, glaring safety issue with Shuttle every time it launched. STS-51L was singlehandedly caused by the fact that solids cannot be shut down after ignition (horrific QA and bureaucratic/political inertia were just a couple sparks).
Several key senior personnel involved in the program are on record stating how the worst possible thing that could theoretically happen at launch was either an asymmetrical solid ignition or an abort where SSMEs were forced into shutdown after solid ignition. Either would have been death sentences. Solid boosters were also responsible for most of Shuttle's "black zones" during lunch.
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#11
by
JEF_300
on 06 Nov, 2018 04:09
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So what things could you do to fix the solid-exhaust v/s parachute problem?
1. Require a more powerful abort system, that can propel the spacecraft further from the vehicle.
2. Require some sort of mechanism to extinguish the motors. *
3. Set a rule that only spacecraft without parachutes, like Dreamchaser, can fly on Omega
* Very difficult and expensive, but NASA engineers in the 70s thought it was possible
It's not solid exhaust that's the issue. It's burning pieces of a solid boost that has blown itself apart that is the issue. So extinguishing the motor is not an option.
Please see the video upthread of the 1997 Delta 2 explosion.
I've seen that video before, a few times actually, and while it is incredibly interesting, I don't see how it's relevant.
A truck covered in propellant on earth =/= A reentry rated capsule falling through a cloud of propellant in the air
While it certainly seems like something that would be problematic, the only issue I've seen raised in official reports is the issue of solid exhaust destroying parachutes. Exhaust isn't normally that big a deal. However, my understanding is that solid propellant, certainly the shuttle mix, burns unevenly. The result is that some of it is still burning in the air.
As was said above, the shuttle SRBs were overengineered, and never had a structural failure. So exhaust was the only way solid fuel escaped the booster. This is probably why NASA and ATK have never worried about an exploding SRB.
Of course, these new Common Booster Segments are carbon composite rather than steal, and might be at more risk. So maybe it is a relevant point. And that's before even mentioning Omega's strap-on SRBs.
Let's say these new carbon composite boosters do have the potential to fail in such a manner. How should that risk be dealt with? Is it really any worse than the exhaust itself anyway? It certainly seems like it would be, but how much worse?
Edit: Wouldn't the Atlas-Starliner, which also launches with strap-on boosters, have similar problems? Anyone know of any investigation into that?
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#12
by
RonM
on 06 Nov, 2018 05:07
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So what things could you do to fix the solid-exhaust v/s parachute problem?
1. Require a more powerful abort system, that can propel the spacecraft further from the vehicle.
2. Require some sort of mechanism to extinguish the motors. *
3. Set a rule that only spacecraft without parachutes, like Dreamchaser, can fly on Omega
* Very difficult and expensive, but NASA engineers in the 70s thought it was possible
It's not solid exhaust that's the issue. It's burning pieces of a solid boost that has blown itself apart that is the issue. So extinguishing the motor is not an option.
Please see the video upthread of the 1997 Delta 2 explosion.
The answer is a LAS. There is no solid-exhaust vs parachute problem because the LAS moves the crewed vehicle to a safe distance before deploying the parachutes.
For example, Orion on SLS.
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#13
by
Steven Pietrobon
on 06 Nov, 2018 05:28
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Sigh. They don't make wooden stakes like they used to.
The similar Ares-I caused a lot of grief in the space community. It was basically an all-new design that effectively delayed crewed access to space for the US. A lighter weight capsule with Atlas-V was a far superior solution that is now finally being realised with CST-100. Anyone designing a crewed system in my opinion would be nuts to fly on OmegA with its all solid first and second stage, when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
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#14
by
JEF_300
on 06 Nov, 2018 05:41
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... Anyone designing a crewed system in my opinion would be nuts to fly on OmegA with its all solid first and second stage, when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
I agree. There's a reason I prefaced the title with "Thought Experiment"
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#15
by
Steven Pietrobon
on 06 Nov, 2018 05:57
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I agree. There's a reason I prefaced the title with "Thought Experiment"
The problem is the large distances travelled by the burning propellant when the stage explodes. Computer simulations showed a high probability of the descending capsule in the burning debris field from an exploding booster on Ares I. This may still be a problem with SLS and Atlas V. They haven't shown their simulations so we can only hope that it is not a problem. They may instead be relying on the low probability of an exploding booster.
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#16
by
john smith 19
on 06 Nov, 2018 08:12
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Solids get a bad rap but they don't deserve it, if Challenger was scrubbed and didn't end up exploding solids would be viewed differently.
Welcome to the forum.
I'd certainly agree solids make great weapon systems. As for Challenger it
did happen, and BTW an independent safety assessment made by (IIRC) McDonald Douglas during Shuttle design reckoned if anything would go wrong, it was in the SRB segment joints. Which is exactly where it did go wrong.
Oscillations are a problem, but far from insurmountable, the burning fuel flying everywhere is the big issue with a solid core stage. The LAS for Orion is capable of safely launching Orion away from an exploding SRB, and would work (obviously with some modifications) on OmegA. It was designed for Ares 1, and they haven't changed it for SLS. The other thing to consider would be launching Dreamchaser, SNC still wants to fly crew on it, they could launch the cargo version on OmegA first, and it doesn't have a LAS so they're probably screwed if the rocket blows up in such a manner anyway. Solid motor hate is far to prevalent
Vibration you can (maybe) handle. Building it on one piece simplifies a lot of issues
but there is no know way to
shut them down Some of the Atlas and Deltas have several smallish SRB's and jettisoned them over time, but these huge lumps of explosive can't do that.
SRB's on Shuttle were driven by the budget. SRB's on SLS were driven by politics. They need a shed load of QC in mfg and ultimately cannot be proof fired. If a short firing (of the actual SRBs you're going to fly) were possible what would it prove? There are no faults in the pour? Or no faults that you have
found?If people can be persuaded OmegAs vibration profile won't shake their payloads to bits and it can establish a track record then it should establish a market (if it's not ruinously expensive), as NASA's Scout rocket did before it.
But carrying people? I think not.
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#17
by
Fequalsma
on 06 Nov, 2018 09:06
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John Smith can you provide a reference for this MCDAC safety assessment? There was a LONG list of CRIT 1 /1R items that could go wrong with the Shuttle system. An assertion that the SRB joints would be THE cause of anything going wrong sounds suspiciously like Monday morning quarterbacking on their part.
F=ma
BTW an independent safety assessment made by (IIRC) McDonald Douglas during Shuttle design reckoned if anything would go wrong, it was in the SRB segment joints. Which is exactly where it did go wrong.
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#18
by
ncb1397
on 06 Nov, 2018 13:06
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when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
The SRBs had one failure out of 270 SRBs flown. How is Falcon 9 with 2 upper stage failures in 62 flights safer? Atlas V is safe, but Vulcan and New Glenn? That is highly debateable. It seems like liquid propulsion gets put in the safe category by default in your list and solids go the other way even though it was the explosion of the ET (caused by the SRB), not the SRBs directly that caused Challenger to break up.
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#19
by
Rocket Science
on 06 Nov, 2018 13:17
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Fratricide Report from the 45th Space Wing
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#20
by
Prettz
on 06 Nov, 2018 13:34
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How does sending astronauts up on Omega help slash the costs of getting to space?
There's your thought experiment.
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#21
by
edkyle99
on 06 Nov, 2018 13:54
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This idea popped into my brain and now I need answers. If, for whatever reason, it was decided in the next few years to attempt to man-rate Omega, what would that look like? How well suited is Omega to lofting crews? What would be the major roadblocks? How might these roadblocks be solved?
Edited to add note: Try to think like an engineer, not a critic. This thread is NOT about whether or not Omega should be man-rated. It's is a mental an engineering challenge to figure out what would be required to man-rate it.
The Common Booster Segments would have to be "man rated". This is a process that would have to occur anyway if they were ever to be used by SLS, which seems to be a long range plan. The fact that Omega will fly from LC 39 would help, since the Orion/SLS ground processing infrastructure would be there already.
The biggest challenge would probably be adapting or modifying the Orion launch escape system to an Omega launch. Omega would fly a substantially different ascent profile than SLS - different velocities and different altitudes, etc..
And which Omega would be required? Heavy? Would strap-on GEM-63XL boosters be allowed? (They're presumably going to be used for CST-100 if it transitions to Vulcan.) Etc.
Re: the cost question. If SLS were to fall by the wayside, an EELV-Heavy would be the only option for Orion. If Omega wins an EELV-2 slot, it would have to be considered along with whichever other launch vehicle wins EELV-2 work. Right now those other alternatives would be Vulcan Heavy (with its numerous strap on GEM-63XL solids) or New Glenn.
- Ed Kyle
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#22
by
JonathanD
on 06 Nov, 2018 15:06
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The SRBs had one failure out of 270 SRBs flown.
Not true. It had one failure that resulted in catastrophic loss of vehicle and crew, but leading up to Challenger there were many instances of blow by and erosion of the primary joint seal. That is not what they were designed for, and continued acceptance of this failure mode was a big part of the procedural cause of the disaster.
How is Falcon 9 with 2 upper stage failures in 62 flights safer?
Being able to abort during all phases of the flight makes it significantly safer from a design standpoint. That doesn't mean the vehicle couldn't have, or had, other unrelated design issues.
Atlas V is safe, but Vulcan and New Glenn? That is highly debateable. It seems like liquid propulsion gets put in the safe category by default in your list and solids go the other way.
That is because solids, with their tendency for violent vibrations, lack of shutdown capability, and negative impact on abort scenarios due to the nature of flaming chunks of solid rocket fuel, don't mix well with humans. I think they were a poor choice for Shuttle, and remain a poor choice for SLS. It's a deep irony, that with all the money we would wind up eventually spending on the Shuttle program, that solid rocket motors were chosen for lower up-front cost considerations.
even though it was the explosion of the ET (caused by the SRB), not the SRBs directly that caused Challenger to break up.
...
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#23
by
Tulse
on 06 Nov, 2018 15:13
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I would have thought that solids don't literally explode, and thus might cause less of an issue for aborts than liquid fuelled rockets. Wouldn't shrapnel from a RUD be more likely to hit a top-of-stack crew vehicle from a liquid-fuelled failure? Is there some other issue with failure modes in solids?
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#24
by
JonathanD
on 06 Nov, 2018 15:26
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I would have thought that solids don't literally explode, and thus might cause less of an issue for aborts than liquid fuelled rockets. Wouldn't shrapnel from a RUD be more likely to hit a top-of-stack crew vehicle from a liquid-fuelled failure? Is there some other issue with failure modes in solids?
One of the reasons Thiokol engineers didn't initially think the SRBs were involved in the Challenger disaster is precisely because they did not see them explode. When the casing fails, as it did in the Delta II video posted earlier in the thread, they absolutely explode. Liquid fuels tend to conflagrate quickly. As for shrapnel danger, that's a potential in any significant event, but the capsule should be designed to withstand some impact, consistent with MMOD resistance, etc. And that risk should be much lower by the time the parachute is deployed.
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#25
by
JonathanD
on 06 Nov, 2018 16:10
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The answer is a LAS. There is no solid-exhaust vs parachute problem because the LAS moves the crewed vehicle to a safe distance before deploying the parachutes.
For example, Orion on SLS.
That's a large assumption. Not to get conspiratorial, but one wonders if a contributing factor to the lack of an in-flight abort test for commercial crew being a requirement is reluctance to see a negative test result that could be tied to the use of the solids that NASA knew would be strapped to the side of the Atlas V. Such a test result could result in further scrutiny of the SLS architecture, for which they certainly are not going to do an in-flight abort test. That SpaceX is electing to perform one voluntarily is an interesting spice in the stew.
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#26
by
Lars-J
on 06 Nov, 2018 17:02
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when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
The SRBs had one failure out of 270 SRBs flown. How is Falcon 9 with 2 upper stage failures in 62 flights safer? Atlas V is safe, but Vulcan and New Glenn? That is highly debateable.
Liquid engines and stages certainly can (and do) fail, but their failure modes are far generally more benign. And they can be turned off.
It seems like liquid propulsion gets put in the safe category by default in your list and solids go the other way even though it was the explosion of the ET (caused by the SRB), not the SRBs directly that caused Challenger to break up.
And now you went off the deep end...
So you are blaming the Challenger loss on the ET even though it was the SRB that was the root failure point? You just lost all credibility in this argument.
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#27
by
MattMason
on 06 Nov, 2018 17:12
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Others have said it with more words. I'll express it in two.
Black zones.
The black zone is the part of a flight profile is where aborts simply aren't possible. The Shuttle had several, particularly the 2-minute SRB burn. An OmegA crewed vehicle would be one long black zone that would give the Commercial Crew safety bureaucrats apoplexy.
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#28
by
ncb1397
on 06 Nov, 2018 17:26
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when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
The SRBs had one failure out of 270 SRBs flown. How is Falcon 9 with 2 upper stage failures in 62 flights safer? Atlas V is safe, but Vulcan and New Glenn? That is highly debateable.
Liquid engines and stages certainly can (and do) fail, but their failure modes are far generally more benign. And they can be turned off.
An example would be good. The "failure mode" of the 1998 Delta II was the activation of the flight termination system. It was designed to do that to the booster. In a manned system, the flight termination system won't be activated right away, which is why the Challenger SRBs didn't explode and kill the crew, the ET exploded and killed the crew. It was exactly the opposite of what you said, the SRBs failed, but they did so benignly as far as damaging the crew vehicle. There was no large SRB explosion that destroyed/damaged orbiter, there was a large liquid fuel explosion that did.
If Challenger had liquid boosters and the boosters did this:
The ET would have likely failed just the same. And as seen in the recent Soyuz failure, liquid boosters are also capable of impacting the core and destroying it, which is what the SRB on challenger did.
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#29
by
edkyle99
on 06 Nov, 2018 17:34
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An OmegA crewed vehicle would be one long black zone that would give the Commercial Crew safety bureaucrats apoplexy.
Not with a properly designed escape system.
- Ed Kyle
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#30
by
ncb1397
on 06 Nov, 2018 17:50
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An OmegA crewed vehicle would be one long black zone that would give the Commercial Crew safety bureaucrats apoplexy.
Not with a properly designed escape system.
- Ed Kyle
Worse comes to worse, if you were super worried about this, it would require a 4 second abort motor accelerating the capsule to ~850 ft/s vs 3 seconds and 650 ft/s currently. That gives you much more margin over the speed and trajectory of SRB debris. But the current system it seems is designed to essentially get above the debris and then deploy parachutes, thus lowering the ballistic coefficient way below any debris (i.e. the debris falls quicker than the capsule). There is only raining down of SRB fragments if the fragments are above the capsule at parachute deployment. If that was the case, you are in the debris field already.
That would explain the 90 degree U-turn from horizontal to vertical in this (50 seconds in the video):
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#31
by
envy887
on 06 Nov, 2018 18:18
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An OmegA crewed vehicle would be one long black zone that would give the Commercial Crew safety bureaucrats apoplexy.
Not with a properly designed escape system.
- Ed Kyle
Worse comes to worse, if you were super worried about this, it would require a 4 second abort motor accelerating the capsule to ~850 ft/s vs 3 seconds and 650 ft/s currently. That gives you much more margin over the speed and trajectory of SRB debris. But the current system it seems is designed to essentially get above the debris and then deploy parachutes, thus lowering the ballistic coefficient way below any debris (i.e. the debris falls quicker than the capsule). There is only raining down of SRB fragments if the fragments are above the capsule at parachute deployment. If that was the case, you are in the debris field already.
The chutes are deployed using drogues. The drogues are also nylon. If the drogues are melted, the chutes won't deploy. So you can't deploy the chutes in a SRB debris field in order to lower the ballistic coefficient and float above the debris.
Also, the debris will have a widely varying range of ballistic coefficients, since they are of roughly constant density but widely varying size. There's no guarantee the capsule would slow faster than the smaller debris.
The only way to mitigate that risk is for the LAS to pull the capsule clear the debris field completely, before popping the drogues.
The Titan 20A threw debris ~7900 ft radially (in every direction... going "up" gives you no advantage) at up to 600 fps. If you have a 250 fps velocity advantage from the LAS (850 vs 600 fps), you need about 32 seconds to exit that debris field before you can deploy the drogues. You probably need about the same about of time to coast to apogee and slow subsonic.
Like Ed said, you need a properly designed abort system. It could be done.
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#32
by
Lars-J
on 06 Nov, 2018 19:04
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Like Ed said, you need a properly designed abort system. It could be done.
Of course it could be done. But then you also end up with an absurdly large launch escape system like Orion - or worse.
Just because it can be done does not mean it is the optimal or practical solution. Which applies equally well to the idea that spawned this thread. Man-rating OmegA - possible but not practical when there are superior alternatives.
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#33
by
John Santos
on 06 Nov, 2018 19:22
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when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
The SRBs had one failure out of 270 SRBs flown. How is Falcon 9 with 2 upper stage failures in 62 flights safer? Atlas V is safe, but Vulcan and New Glenn? That is highly debateable.
Liquid engines and stages certainly can (and do) fail, but their failure modes are far generally more benign. And they can be turned off.
An example would be good. The "failure mode" of the 1998 Delta II was the activation of the flight termination system. It was designed to do that to the booster. In a manned system, the flight termination system won't be activated right away, which is why the Challenger SRBs didn't explode and kill the crew, the ET exploded and killed the crew. It was exactly the opposite of what you said, the SRBs failed, but they did so benignly as far as damaging the crew vehicle. There was no large SRB explosion that destroyed/damaged orbiter, there was a large liquid fuel explosion that did.
If Challenger had liquid boosters and the boosters did this:
The ET would have likely failed just the same. And as seen in the recent Soyuz failure, liquid boosters are also capable of impacting the core and destroying it, which is what the SRB on challenger did.
This is wrong in many ways. Challenger had no LES and was not destroyed by the ET conflagration (not an explosion), but was forced into a non-aerodynamic orientation and the airflow (well above Mach 1) ripped it apart. LRBs have no failure mode similar to the Challenger SRB failure mode (a combustion chamber or engine bell leak could not directly impinge on the ET or the attachment struts because the engines are below the ET and struts), but some other failure (similar to the Soyuz MS-10 failure) could cause a booster to collide with and rupture the ET. However, there would have been much more time to react. The boosters would be shut down before separation, not driving at full thrust through the ET, and like Soyuz, the SSMEs would have shut down and allowed an orderly separation of the orbiter, which would have either ditched or attempted an RTLS abort. Probably unsuccessfully, which is why an LES is good. (Close to liftoff, even with non-exploding but detached or out of control LRBs, the orbiter wouldn't be above its stall speed and would be doomed by any booster failure. LES is good!)
An SRB joint failure could just as easily cut into the orbiter as the ET, possibly destroying a wing or the tail or the heat shield or rupturing the LOX/LH2 fuel cell tanks, or the N2O2/Hydrazine OMS tanks, or the SRB blowtorch could have pointed the other way. (In that case the reduced, asymmetric thrust would have still caused an abort, but it might have been survivable.) Just because the SRBs didn't directly destroy the orbiter doesn't let them off the hook in any way.
A Dragon 2 (or any other crewed vehicle with an LES) would have survived the AMOS-6 failure.
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#34
by
RonM
on 06 Nov, 2018 20:01
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The answer is a LAS. There is no solid-exhaust vs parachute problem because the LAS moves the crewed vehicle to a safe distance before deploying the parachutes.
For example, Orion on SLS.
That's a large assumption. Not to get conspiratorial, but one wonders if a contributing factor to the lack of an in-flight abort test for commercial crew being a requirement is reluctance to see a negative test result that could be tied to the use of the solids that NASA knew would be strapped to the side of the Atlas V. Such a test result could result in further scrutiny of the SLS architecture, for which they certainly are not going to do an in-flight abort test. That SpaceX is electing to perform one voluntarily is an interesting spice in the stew.
Um, yeah, what you wrote would be a conspiracy. Let's try not going there.
Man rating OmegA might not be a good idea for several reasons, but all this concern trolling about melting parachutes is ridiculous. An Orion-class LAS might be too expensive to be practical for a commercial vehicle, but technically it would work.
In the unlikely scenario that Congress kept funding Orion after cancelling SLS, OmegA could be an option for Orion.
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#35
by
obi-wan
on 06 Nov, 2018 20:50
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I would have thought that solids don't literally explode, and thus might cause less of an issue for aborts than liquid fuelled rockets. Wouldn't shrapnel from a RUD be more likely to hit a top-of-stack crew vehicle from a liquid-fuelled failure? Is there some other issue with failure modes in solids?
Solid motors certainly do "explode", although most failures you see are officially termed "deflagrations" (increase in burning area (like a crack in the grain)-->increase in pressure-->increase in burning rate-->additional pressure spike and continue until the pressure vessel ruptures. That's the kind of failure the fratricide analysis talks about. However, all solids also have the potential for a detonation-mode failure, where some combination of grain shape and failure configuration (e.g., two or more parallel cracks with the right spacing) causes a supersonic detonation wave which cooks off almost all of the propellant at once. Your LAS won't help you at all because the detonation follows the source by milliseconds, and you won't be able to initiate the abort before the RUD occurs.
Every propellant has its own DDT (deflagration-detonation transition) conditions. The propellants used in SRBs are resistant to it, so it's not talked about much. (NASA must assume the likelihood of detonation-mode failure is zero to come up with the LOC numbers they use.) But DDT onset is accentuated by larger motor sizes, and they don't come much larger than the five-segment motors we're talking about. Even before Challenger, I sweated every shuttle launch until SRB sep. (worse afterwards...)
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#36
by
JEF_300
on 06 Nov, 2018 20:58
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I'm still curious about whether the lack of parachutes on Dreamchaser makes it an option. Does anyone have information on Dreamchaser aborts?
There's more to man-rating a vehicle than a good LES. For instance, while Ares I and Omega have some obvious similarities, I imagine they're G-force plots would look very different. How high will the G's go on an Omega launch? I would assume the extra staging will translate to lower G's, but perhaps it's counter-intuitive.
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#37
by
MATTBLAK
on 06 Nov, 2018 20:59
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There is simply NO need to manrate OmegA. There are plenty of 'manrated' boosters either in existence or about to be. End of story. I do think OmegA should be optimised to lift the biggest payloads possible as a cargo or satellite launcher. And if it succeeds or fails on it's own merits/drawbacks; let the market decide...
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#38
by
JEF_300
on 06 Nov, 2018 21:17
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There is simply NO need to manrate OmegA. There are plenty of 'manrated' boosters either in existence or about to be. End of story. I do think OmegA should be optimised to lift the biggest payloads possible as a cargo or satellite launcher. And if it succeeds or fails on it's own merits/drawbacks; let the marker decide...
Yes, man-rating Omega would be potentially dangerous.
Yes, man-rating Omega would be expensive.
Yes, man-rating Omega would be pointless.
But none of those things are the point of this thread. I just thought it would be fun to think through what would be required to man-rate Omega, that's all. If it helps, you can imagine this is a hypothetical where SpaceX and ULA and Blue Origin have all suddenly gone bankrupt without warning.
As far as I'm concerned, any discussion of whether Omega
should be man-rated is off topic.
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#39
by
Rocket Science
on 06 Nov, 2018 21:38
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I'm still curious about whether the lack of parachutes on Dreamchaser makes it an option. Does anyone have information on Dreamchaser aborts?
There's more to man-rating a vehicle than a good LES. For instance, while Ares I and Omega have some obvious similarities, I imagine they're G-force plots would look very different. How high will the G's go on an Omega launch? I would assume the extra staging will translate to lower G's, but perhaps it's counter-intuitive.
SNC is on record stating that Crew DC has zero back zones on Atlas V... YMMV
http://www.americaspace.com/2014/11/17/snc-outlines-challenges-and-opportunities-for-landing-dream-chaser-at-public-airports/Pad abort similar to HL-20
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#40
by
freda
on 06 Nov, 2018 22:31
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Hmmm... interesting. A related curious thought pops into my mind, for discussion: Man-rating Ares solid booster verses man-rating the OmegA solid booster:
Are there differences to consider? Similarities?
For that matter, could the existing (Shuttle + SLS) SRB segment booster (already man-rated) replace the OmegA booster?
You can probably tell I am in no way an expert in this topic
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#41
by
john smith 19
on 06 Nov, 2018 22:32
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Every propellant has its own DDT (deflagration-detonation transition) conditions. The propellants used in SRBs are resistant to it, so it's not talked about much. (NASA must assume the likelihood of detonation-mode failure is zero to come up with the LOC numbers they use.) But DDT onset is accentuated by larger motor sizes, and they don't come much larger than the five-segment motors we're talking about. Even before Challenger, I sweated every shuttle launch until SRB sep. (worse afterwards...)
"Resistant" to DDT is not the same as impossible.
I found it interesting that the burn rate for these motors is around 0.34"/sec while those for the Sprint ABM (possibly the highest performing solid prop vehicle ever built) was more like 40"/sec (with experimental motors hitting more like 50"/sec. Unfortunately this seems to have often been just before they went to a full on explosion).
IIR NASA looked at ways to shut big solids down but concluded they'd tear the Shuttle stack apart with shock loads. Blowing the tail cone off and blowing holes in the top end of the pressure vessel seemed to be involved.
An interesting question would be do you want full shut down? Could lowering it's forward thrust, while blowing some of its exhaust out the front end (through inter stage blow out panels?) be good enough to separate a rogue stage or booster?
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#42
by
TomH
on 07 Nov, 2018 05:46
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In the unlikely scenario that Congress kept funding Orion after cancelling SLS, OmegA could be an option for Orion.
Falcon Heavy and New Glenn could as well, sans solids. And they are partly reusable.
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#43
by
Zed_Noir
on 07 Nov, 2018 10:41
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For launch abort. The Original Dragon 2 LES concept with superDracos with additional SuperDracos installed in the trunk might work on top of the OmegA after blowing out the seams of the Castor motors. Presuming that the SuperDracos is activated prior to unzipping the Castors.
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#44
by
envy887
on 07 Nov, 2018 15:41
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In the unlikely scenario that Congress kept funding Orion after cancelling SLS, OmegA could be an option for Orion.
To what end? Orion is a (not-too)deep-space vehicle. Omega is too small to lift it much beyond LEO. And unlike ULA with Vulcan ACES, NGIS has no plans to implement refueling which would allow Omega to send Orion to TLI or beyond.
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#45
by
JonathanD
on 07 Nov, 2018 16:45
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So to summarize the thought experiment of "what would be required to put crew on OmegA" :
1) Significantly enhanced LES in order to ensure safe clear of debris field
2) Extensive testing of vibrations/oscillations due to complete reliance on solid rocket motors in initial stages and potential redesign of upper stage with additional dampening
3) A spacecraft that is either developed specifically for OmegA or an existing spacecraft that is adapted, with some potential redesign work.
...and perhaps most importantly...
4) A reason to do it. With two commercial crew providers coming online plus Orion/SLS, it would be incredibly difficult to justify funding Steps 1-3 above.
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#46
by
Hog
on 07 Nov, 2018 17:27
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when there are far safer alternatives that are or will be flying (Falcon 9, Falcon Heavy, Atlas V, Vulcan and New Glenn).
The SRBs had one failure out of 270 SRBs flown. How is Falcon 9 with 2 upper stage failures in 62 flights safer? Atlas V is safe, but Vulcan and New Glenn? That is highly debateable.
Liquid engines and stages certainly can (and do) fail, but their failure modes are far generally more benign. And they can be turned off.
An example would be good. The "failure mode" of the 1998 Delta II was the activation of the flight termination system. It was designed to do that to the booster. In a manned system, the flight termination system won't be activated right away, which is why the Challenger SRBs didn't explode and kill the crew, the ET exploded and killed the crew. It was exactly the opposite of what you said, the SRBs failed, but they did so benignly as far as damaging the crew vehicle. There was no large SRB explosion that destroyed/damaged orbiter, there was a large liquid fuel explosion that did.
If Challenger had liquid boosters and the boosters did this:
The ET would have likely failed just the same. And as seen in the recent Soyuz failure, liquid boosters are also capable of impacting the core and destroying it, which is what the SRB on challenger did.
This is wrong in many ways. Challenger had no LES and was not destroyed by the ET conflagration (not an explosion), but was forced into a non-aerodynamic orientation and the airflow (well above Mach 1) ripped it apart. LRBs have no failure mode similar to the Challenger SRB failure mode (a combustion chamber or engine bell leak could not directly impinge on the ET or the attachment struts because the engines are below the ET and struts), but some other failure (similar to the Soyuz MS-10 failure) could cause a booster to collide with and rupture the ET. However, there would have been much more time to react. The boosters would be shut down before separation, not driving at full thrust through the ET, and like Soyuz, the SSMEs would have shut down and allowed an orderly separation of the orbiter, which would have either ditched or attempted an RTLS abort. Probably unsuccessfully, which is why an LES is good. (Close to liftoff, even with non-exploding but detached or out of control LRBs, the orbiter wouldn't be above its stall speed and would be doomed by any booster failure. LES is good!)
An SRB joint failure could just as easily cut into the orbiter as the ET, possibly destroying a wing or the tail or the heat shield or rupturing the LOX/LH2 fuel cell tanks, or the N2O2/Hydrazine OMS tanks, or the SRB blowtorch could have pointed the other way. (In that case the reduced, asymmetric thrust would have still caused an abort, but it might have been survivable.) Just because the SRBs didn't directly destroy the orbiter doesn't let them off the hook in any way.
A Dragon 2 (or any other crewed vehicle with an LES) would have survived the AMOS-6 failure.
With STS, once the SSME's have been shutdown, a Return To Launch Site abort is an impossibility. Their thrust is required for the Powered Pitch Around(PPA) maneuver(planned to be performed with 2% propellants in tank). The best case scenario would entail dropping the ET as quickly as possible and attempting to get the Orbiter into a glide for bailout. I'm not sure what would be possible so far as dropping an ET without purging the propellants or getting into a glide orientation without dumping any OMS propellants. Both of these activities are part of the RTLS abort.
Post Challenger the 2 and 3 engine out black zones were much reduced with the reinforced ET, Orbiter attach hardware.
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#47
by
envy887
on 07 Nov, 2018 18:13
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So to summarize the thought experiment of "what would be required to put crew on OmegA" :
1) Significantly enhanced LES in order to ensure safe clear of debris field
2) Extensive testing of vibrations/oscillations due to complete reliance on solid rocket motors in initial stages and potential redesign of upper stage with additional dampening
3) A spacecraft that is either developed specifically for OmegA or an existing spacecraft that is adapted, with some potential redesign work.
...and perhaps most importantly...
4) A reason to do it. With two commercial crew providers coming online plus Orion/SLS, it would be incredibly difficult to justify funding Steps 1-3 above.
Orion should meet 1-3 above, since SLS going sideways would generate an even worse debris cone than Omega.
Whether it actually does? I would love to see that study. I hope it exists.
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#48
by
JonathanD
on 07 Nov, 2018 18:25
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Orion should meet 1-3 above, since SLS going sideways would generate an even worse debris cone than Omega.
Whether it actually does? I would love to see that study. I hope it exists.
It's kind of a waste of Orion to put it on a rocket that's only going to get it to LEO. And I recall all the modifications they had to do to Ares 1-X to compensate for vibrations. SLS Core stage will help dampen things for SLS, but on OmegA there may be additional work done on the upper stage to account for that.
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#49
by
RonM
on 07 Nov, 2018 18:48
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In the unlikely scenario that Congress kept funding Orion after cancelling SLS, OmegA could be an option for Orion.
To what end? Orion is a (not-too)deep-space vehicle. Omega is too small to lift it much beyond LEO. And unlike ULA with Vulcan ACES, NGIS has no plans to implement refueling which would allow Omega to send Orion to TLI or beyond.
I'm thinking about what Congress might do, not what we think would be good ideas.
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#50
by
JEF_300
on 07 Nov, 2018 20:10
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Keeping mind that this is a bad idea; canceling SLS and flying Orion on Omega doesn't eliminate deep space as a destination, it just means that you need to use some sort of Earth Orbit Rendezvous architecture to get there.
If anyone knows anything about how well Omega's G levels and trajectory fit a manned spaceflight, I'm certainly curious. I know Boeing is buying the two engine centaur on CST-100 launches for a flatter trajectory, so how flat is Omega's trajectory?
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#51
by
groundbound
on 07 Nov, 2018 21:01
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There is simply NO need to manrate OmegA. There are plenty of 'manrated' boosters either in existence or about to be. End of story. I do think OmegA should be optimised to lift the biggest payloads possible as a cargo or satellite launcher. And if it succeeds or fails on it's own merits/drawbacks; let the market decide...
This. One of the riskiest things about regular old OmegA is that it might end up fatally cost-uncompetitive by the time it flies. Loading the costs of man-rating onto it makes that risk worse.
There are uncountable potential rocket designs that are technically feasible if you spend enough money but pointless to discuss because of the cost. I would not include OmegA in that pantheon, but that is not a "problem" that needs to be solved.
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#52
by
envy887
on 08 Nov, 2018 14:22
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Keeping mind that this is a bad idea; canceling SLS and flying Orion on Omega doesn't eliminate deep space as a destination, it just means that you need to use some sort of Earth Orbit Rendezvous architecture to get there.
If anyone knows anything about how well Omega's G levels and trajectory fit a manned spaceflight, I'm certainly curious. I know Boeing is buying the two engine centaur on CST-100 launches for a flatter trajectory, so how flat is Omega's trajectory?
Trajectory shouldn't be a problem. Solids produce lots of thrust and have short burn times, so it will get to the first two staging velocities quickly. The 3rd stage is a dual-engine RL-10 according to the marking artwork, so its trajectory should be comparable to DEC.
One of the few advantages of Ares-1 was its short and flat ascent trajectory.
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#53
by
edkyle99
on 09 Nov, 2018 02:36
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One of the riskiest things about regular old OmegA is that it might end up fatally cost-uncompetitive by the time it flies. Loading the costs of man-rating onto it makes that risk worse.
Omega won one of the most recent three EELV-2 contracts, so it wasn't uncompetitive in that race. Vulcan Centaur uses three different propellant combinations and propulsion contractors compared to two for Omega (one of them in-house), so it should be able to compete on that basis. New Glenn is a giant, weighing nearly 1,400 tonnes even for the smallest payloads, compared to 440 tonnes for Omega 500 (Medium), so there is potential to compete even when New Glenn recovers its first stage.
- Ed Kyle
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#54
by
Coastal Ron
on 09 Nov, 2018 03:20
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One of the riskiest things about regular old OmegA is that it might end up fatally cost-uncompetitive by the time it flies. Loading the costs of man-rating onto it makes that risk worse.
Omega won one of the most recent three EELV-2 contracts, so it wasn't uncompetitive in that race.
I don't think you understood the question, since the USAF contract was not intended to find low-cost launch providers (or high cost ones for that matter), it was to find qualified launch providers. It's not up to the government to ensure the bidders have the financial wherewithal to find a foothold in the future launch market.
Vulcan Centaur uses three different propellant combinations and propulsion contractors compared to two for Omega (one of them in-house), so it should be able to compete on that basis. New Glenn is a giant, weighing nearly 1,400 tonnes even for the smallest payloads, compared to 440 tonnes for Omega 500 (Medium), so there is potential to compete even when New Glenn recovers its first stage.
None of that is related to operational costs.
Not only that, regardless how much New Glenn costs Jeff Bezos has the financial ability to support Blue Origin forever, meaning that they can charge normal prices for government contracts (GAO rules demand accurate pricing), but sell commercial launches at cost to essentially buy market share. In such a case both ULA and NGIS would have a harder time gaining any commercial contracts in order to spread their operational costs across more launches.
Higher cost, along with questionable safety, would make OmegA an unlikely choice for human-rating - for any customer.
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#55
by
edkyle99
on 09 Nov, 2018 14:40
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I don't think you understood the question, since the USAF contract was not intended to find low-cost launch providers (or high cost ones for that matter), it was to find qualified launch providers. It's not up to the government to ensure the bidders have the financial wherewithal to find a foothold in the future launch market.
The intent of EELV-2 (soon to be renamed NSSLP) is to enable "commercially viable" launch services that can also meet USAF/NRO/etc. launch requirements. If it isn't commercially viable, it isn't going to win. Omega won an LSA, so it is still in the game.
… regardless how much New Glenn costs Jeff Bezos has the financial ability to support Blue Origin forever, meaning that they can charge normal prices for government contracts (GAO rules demand accurate pricing), but sell commercial launches at cost to essentially buy market share. In such a case both ULA and NGIS would have a harder time gaining any commercial contracts in order to spread their operational costs across more launches.
The US should base its national defense strategy on the idea that one guy will bankroll his program forever?
Higher cost, along with questionable safety, would make OmegA an unlikely choice for human-rating - for any customer.
You keep saying that Omega has higher costs and questionable safety. Why? What is your basis for those assertions? If Northrop Grumman is winning LSA money, they surely must be meeting some requirements for cost and safety.
- Ed Kyle
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#56
by
M129K
on 09 Nov, 2018 17:19
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I'm wondering: do we actually have LEO payload figures for Omega? I haven't been able to find any so far. It's great and all if it might hypothetically be used to launch Orion, but if it can't get the ~27 tonne capsule with its heavy LES into LEO the discussion becomes pretty moot.
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#57
by
envy887
on 09 Nov, 2018 22:47
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...If Northrop Grumman is winning LSA money, they surely must be meeting some requirements for cost and safety.
Safety of a crew capsule during or after a launch failure is certainly not a USAF requirement for EELV.
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#58
by
envy887
on 09 Nov, 2018 22:48
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I'm wondering: do we actually have LEO payload figures for Omega? I haven't been able to find any so far. It's great and all if it might hypothetically be used to launch Orion, but if it can't get the ~27 tonne capsule with its heavy LES into LEO the discussion becomes pretty moot.
I'm pretty sure they would need the XL version with several solid strap-on to get Orion the LEO. The Delta IV Heavy is iffy for Orion to LEO, and the XL has similar performance to DIVH.
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#59
by
ChrisWilson68
on 09 Nov, 2018 22:57
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I don't think you understood the question, since the USAF contract was not intended to find low-cost launch providers (or high cost ones for that matter), it was to find qualified launch providers. It's not up to the government to ensure the bidders have the financial wherewithal to find a foothold in the future launch market.
The intent of EELV-2 (soon to be renamed NSSLP) is to enable "commercially viable" launch services that can also meet USAF/NRO/etc. launch requirements. If it isn't commercially viable, it isn't going to win. Omega won an LSA, so it is still in the game.
… regardless how much New Glenn costs Jeff Bezos has the financial ability to support Blue Origin forever, meaning that they can charge normal prices for government contracts (GAO rules demand accurate pricing), but sell commercial launches at cost to essentially buy market share. In such a case both ULA and NGIS would have a harder time gaining any commercial contracts in order to spread their operational costs across more launches.
The US should base its national defense strategy on the idea that one guy will bankroll his program forever?
Higher cost, along with questionable safety, would make OmegA an unlikely choice for human-rating - for any customer.
You keep saying that Omega has higher costs and questionable safety. Why? What is your basis for those assertions? If Northrop Grumman is winning LSA money, they surely must be meeting some requirements for cost and safety.
There's no evidence the Air Force did, or had any intent to, any sort of evaluation of eventual commercial viability, at this early stage.
Indeed, the evidence strongly suggests that they ignored cost and gave money to every company that had a launch vehicle similar to what the Air Force expects from an EELV. The only company that didn't get money was SpaceX, but that's because their vehicles that are in the EELV class (Falcon 9 and Falcon Heavy) are already in production use and don't need any more development money. BFR isn't what the Air Force was asking for, it's a very different vehicle.
When everyone who had a vehicle like what the Air Force asked for on offer got money, it's really a case that there were no losers. If there are no losers, winning doesn't mean very much. And it certainly doesn't mean that Omega will be cost-competitive.
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#60
by
Coastal Ron
on 10 Nov, 2018 02:39
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The intent of EELV-2 (soon to be renamed NSSLP) is to enable "commercially viable" launch services that can also meet USAF/NRO/etc. launch requirements. If it isn't commercially viable, it isn't going to win.
How was "commercial viable" determined? What criteria did they use?
When I look at the "Statement Of Objectives" that is part of the RFQ, I only see the following:
3.0 Programmatics
The following activities shall be conducted to allow the Government to gain insight and understanding of the development effort:
...
3. Business case analysis or updates to previously submitted business case analysis that examines the commercial competitiveness of the launch system under development against projected market conditions.
All they require is an examination, and we don't know what criteria they used to determine the minimum requirements.
For the Statement Of Objectives that one sentence was the only mention of the word "market", and I see no mention of "market" in the RFP itself. And nowhere is the word "viable" used.
And to the point ChrisWilson68 made, in the RFQ it states that their intent was to award three contracts for development, and that is what they did. Mission accomplished!
So I see no evidence that supports your supposition that the OmegA must be commercially viable because it was awarded a contract.
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#61
by
edkyle99
on 10 Nov, 2018 14:09
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#62
by
Coastal Ron
on 10 Nov, 2018 15:31
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"“These awards are central to the Air Force goal of two domestic, commercially viable launch providers that meet National Security Space requirements,” said Lt. Gen. John Thompson, the Air Force’s Program Executive Officer for Space and SMC commander."
Remember they currently have four candidates (SpaceX plus the three awarded this contract), and they will be eliminating one of the three awarded this contract before transitioning to the operational phase of the program. Only the final two need to be "
commercially viable", meaning one that has been awarded this current contract doesn't need to be yet.
In other words, they are more focused on the hardware elements first that can meet their launch requirements, then in the down-select phase they will validate that a launcher is "
commercially viable".
And certainly none of the launchers in this contract have yet to demonstrate that they are "commercially viable", but out of the three NGIS has the hardest road to commercial viability:
New Glenn - Already has 4 commercial customers signed up for 8 flights, and it's owner has the financial resources to pursue the commercial market without making a profit.
Vulcan - Replaces the current workhorses for high value government launches, meaning ULA has a mature workforce and existing assets to support not only government customers, but commercial ones too.
OmegA - No existing facilities for EELV launchers, no existing customers, and no customers have yet to sign up for future launches.
Northrop Grumman is a very capable company, and no doubt they can get OmegA to fly safely.
But just because something works doesn't mean customers will want it - especially when we are at a historic moment in history for reusable rockets, and the OmegA could be amongst the last expendable rockets built. Tides of history can be difficult to swim against...
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#63
by
brickmack
on 10 Nov, 2018 17:49
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What about more of a direct Ares I clone? Castor 1200 plus a single large liquid second stage powered by BE-3Us. If you could do it with only 2 stages, 1 liquid, that'd be at least a bit less comically unsafe. Ares I's vibration issues were from the unfortunately matched frequency of the booster and the large upper stage. Composite booster structures might change that, and the upper stage could be proportionally smaller (both because of the much higher performance booster (lower dry mass, higher fueled mass, higher ISP) and the likely higher ISP of BE-3U than J-2X)
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#64
by
edkyle99
on 10 Nov, 2018 19:41
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... comically unsafe. …
People keep saying this as if it were true. The solids=unsafe assumption is largely based on one failed launch 32 years ago that would have been survivable if the crew of that flight had a launch escape system.
- Ed Kyle
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#65
by
Coastal Ron
on 10 Nov, 2018 20:26
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... comically unsafe. …
People keep saying this as if it were true. The solids=unsafe assumption is largely based on one failed launch 32 years ago that would have been survivable if the crew of that flight had a launch escape system.
The Shuttle Orbiter vehicle never had provisions for an LES that would rescue the entire crew of an operational mission in such a situation.
As to whether any vehicle of any type could survive such a failure, all we know is that the USAF was concerned about solid fuel thrown from an exploding SRM interacting with and melting the parachutes of an Orion spacecraft.
Because unlike liquid-fueled rockets, solid-fuel has a much wider range of danger when dispersed from an explosion.
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#66
by
JEF_300
on 10 Nov, 2018 21:15
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What about more of a direct Ares I clone? Castor 1200 plus a single large liquid second stage powered by BE-3Us. If you could do it with only 2 stages, 1 liquid, that'd be at least a bit less comically unsafe. Ares I's vibration issues were from the unfortunately matched frequency of the booster and the large upper stage. Composite booster structures might change that, and the upper stage could be proportionally smaller (both because of the much higher performance booster (lower dry mass, higher fueled mass, higher ISP) and the likely higher ISP of BE-3U than J-2X)
The only real change there is the removal of a staging event, at the cost of a massive efficiency decrease. So the question would be if that's worth it. The "comically unsafe" solid is still there. And how many spaceflight failures can be attributed to staging anyway?
Although I have been playing with the idea of a vacuum optimized LE-7A upper stage recently...
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#67
by
JonathanD
on 11 Nov, 2018 04:00
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... comically unsafe. …
People keep saying this as if it were true. The solids=unsafe assumption is largely based on one failed launch 32 years ago that would have been survivable if the crew of that flight had a launch escape system.
- Ed Kyle
I disagree. I find the Delta II incident in 1997 a much more concerning situation. In the Challenger disaster, the SRBs did not explode until the range triggered the charges. In the Delta II '97 situation, IIRC it was a casing failure which resulted in the spectacularly bad hailstorm of flaming solid rocket motor debris. Hopefully a launch escape system could clear that aerial minefield, but it's a dramatically different scenario than a conflagration of liquid fuel.
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#68
by
edkyle99
on 11 Nov, 2018 15:11
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... comically unsafe. …
People keep saying this as if it were true. The solids=unsafe assumption is largely based on one failed launch 32 years ago that would have been survivable if the crew of that flight had a launch escape system.
- Ed Kyle
I disagree. I find the Delta II incident in 1997 a much more concerning situation. In the Challenger disaster, the SRBs did not explode until the range triggered the charges. In the Delta II '97 situation, IIRC it was a casing failure which resulted in the spectacularly bad hailstorm of flaming solid rocket motor debris. Hopefully a launch escape system could clear that aerial minefield, but it's a dramatically different scenario than a conflagration of liquid fuel.
From
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000094557.pdf(My underlines.)
"1. Delta II Explosion Event
The Delta II rocket was launched from Launch Complex 17 (LC-17) at CCAFS at 1628 UTC on 17 January 1997. It exploded 12.5 seconds after liftoff at a height of approximately 438 meters. Figure 1 shows a photograph of the explosion.
This initial explosion destroyed only the first stage and the boosters and produced a large cloud extending from the ground upward. The Delta II is a three-stage liquid-propellant vehicle with nine solid-propellant strap-on booster motors.
The second and third stages and payload survived the initial explosion and continued upward to about 760 meters at 22.4 seconds. Destruct signals were sent at this point, and the exploding second-stage formed a buoyant cloud that …."
The payload actually remained largely intact until it impacted the ground, causing the satellite propellants to explode and the Star motor to blast a big crater in the ground. The spectacular first big explosion was mostly the result of the automatic abort system detecting the failing SRM and, as a result, automatically destroying the boosters and first stage. (It should have destroyed the entire vehicle, but that's another story...)
The still-intact upper stages and payload with fairing are clearly visible in this video at about the 1:38 mark.
- Ed Kyle
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#69
by
envy887
on 12 Nov, 2018 12:29
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... comically unsafe. …
People keep saying this as if it were true. The solids=unsafe assumption is largely based on one failed launch 32 years ago that would have been survivable if the crew of that flight had a launch escape system.
- Ed Kyle
I disagree. I find the Delta II incident in 1997 a much more concerning situation. In the Challenger disaster, the SRBs did not explode until the range triggered the charges. In the Delta II '97 situation, IIRC it was a casing failure which resulted in the spectacularly bad hailstorm of flaming solid rocket motor debris. Hopefully a launch escape system could clear that aerial minefield, but it's a dramatically different scenario than a conflagration of liquid fuel.
From https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000094557.pdf
(My underlines.)
"1. Delta II Explosion Event
The Delta II rocket was launched from Launch Complex 17 (LC-17) at CCAFS at 1628 UTC on 17 January 1997. It exploded 12.5 seconds after liftoff at a height of approximately 438 meters. Figure 1 shows a photograph of the explosion. This initial explosion destroyed only the first stage and the boosters and produced a large cloud extending from the ground upward. The Delta II is a three-stage liquid-propellant vehicle with nine solid-propellant strap-on booster motors. The second and third stages and payload survived the initial explosion and continued upward to about 760 meters at 22.4 seconds. Destruct signals were sent at this point, and the exploding second-stage formed a buoyant cloud that …."
The payload actually remained largely intact until it impacted the ground, causing the satellite propellants to explode and the Star motor to blast a big crater in the ground. The spectacular first big explosion was mostly the result of the automatic abort system detecting the failing SRM and, as a result, automatically destroying the boosters and first stage. (It should have destroyed the entire vehicle, but that's another story...)
The still-intact upper stages and payload with fairing are clearly visible in this video at about the 1:38 mark.
- Ed Kyle
Payload fairings and pressure-fed stages are reasonably robust (see: AMOS-6). Nylon parachutes are not. That the payload, Delta K 2nd stage, and STAR-48 survived the Delta II failure doesn't mean much for crew.
The LES on a large solid LV needs to clear a ~3-mile diameter volume that is moving in roughly the same direction and speed as the launch vehicle before it disintegrated.
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#70
by
edkyle99
on 12 Nov, 2018 21:56
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Payload fairings and pressure-fed stages are reasonably robust (see: AMOS-6). Nylon parachutes are not. That the payload, Delta K 2nd stage, and STAR-48 survived the Delta II failure doesn't mean much for crew.
The LES on a large solid LV needs to clear a ~3-mile diameter volume that is moving in roughly the same direction and speed as the launch vehicle before it disintegrated.
An escape and clean parachute phase would have been possible on a Delta 241 type failure because it failed at low velocity, and on STS-51L because the SRBs remained intact for a long period of time. The melted parachute issue was raised by Cape Air Force personnel, based on an assessment of the Titan 4A-20 failure, about only a certain portion of the Ares 1 ascent phase, where velocities and drag, etc., aligned just the wrong way. The solution for future vehicles, and there is one, would be more escape system delta-V and/or a diverging flight path, etc..
At the time, by the way, NASA managers questioned the validity of the Air Force conclusions. I'm not sure how it all turned out, but I believe that there would be a solution or solutions for our hypothetical non-Ares 1 future vehicle.
- Ed Kyle
So you are blaming the Challenger loss on the ET even though it was the SRB that was the root failure point? You just lost all credibility in this argument.
