Author Topic: Thought Experiment: Man Rating OmegA  (Read 7031 times)

Offline Prettz

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Re: Thought Experiment: Man Rating OmegA
« Reply #20 on: 11/06/2018 01:34 PM »
How does sending astronauts up on Omega help slash the costs of getting to space?

There's your thought experiment.

Offline edkyle99

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Re: Thought Experiment: Man Rating OmegA
« Reply #21 on: 11/06/2018 01:54 PM »
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   
« Last Edit: 11/06/2018 02:19 PM by edkyle99 »

Offline JonathanD

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Re: Thought Experiment: Man Rating OmegA
« Reply #22 on: 11/06/2018 03:06 PM »
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.

...
« Last Edit: 11/06/2018 03:10 PM by JonathanD »

Offline Tulse

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Re: Thought Experiment: Man Rating OmegA
« Reply #23 on: 11/06/2018 03:13 PM »
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?

Offline JonathanD

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Re: Thought Experiment: Man Rating OmegA
« Reply #24 on: 11/06/2018 03:26 PM »
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.

Offline JonathanD

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Re: Thought Experiment: Man Rating OmegA
« Reply #25 on: 11/06/2018 04:10 PM »
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.

Offline Lars-J

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Re: Thought Experiment: Man Rating OmegA
« Reply #26 on: 11/06/2018 05:02 PM »
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...  :o 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.
« Last Edit: 11/06/2018 05:03 PM by Lars-J »

Offline MattMason

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Re: Thought Experiment: Man Rating OmegA
« Reply #27 on: 11/06/2018 05:12 PM »
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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Offline ncb1397

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Re: Thought Experiment: Man Rating OmegA
« Reply #28 on: 11/06/2018 05:26 PM »
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.

Offline edkyle99

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Re: Thought Experiment: Man Rating OmegA
« Reply #29 on: 11/06/2018 05:34 PM »
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

Offline ncb1397

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Re: Thought Experiment: Man Rating OmegA
« Reply #30 on: 11/06/2018 05:50 PM »
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):



« Last Edit: 11/06/2018 05:53 PM by ncb1397 »

Offline envy887

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Re: Thought Experiment: Man Rating OmegA
« Reply #31 on: 11/06/2018 06:18 PM »
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.

Offline Lars-J

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Re: Thought Experiment: Man Rating OmegA
« Reply #32 on: 11/06/2018 07:04 PM »
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.

Offline John Santos

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Re: Thought Experiment: Man Rating OmegA
« Reply #33 on: 11/06/2018 07:22 PM »
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.

Offline RonM

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Re: Thought Experiment: Man Rating OmegA
« Reply #34 on: 11/06/2018 08:01 PM »
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.

Offline obi-wan

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Re: Thought Experiment: Man Rating OmegA
« Reply #35 on: 11/06/2018 08:50 PM »
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...)

Re: Thought Experiment: Man Rating OmegA
« Reply #36 on: 11/06/2018 08:58 PM »
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.

Online MATTBLAK

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Re: Thought Experiment: Man Rating OmegA
« Reply #37 on: 11/06/2018 08:59 PM »
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...
« Last Edit: 11/07/2018 12:07 AM by MATTBLAK »
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Re: Thought Experiment: Man Rating OmegA
« Reply #38 on: 11/06/2018 09:17 PM »
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.
« Last Edit: 11/06/2018 09:18 PM by JEF_300 »

Offline Rocket Science

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Re: Thought Experiment: Man Rating OmegA
« Reply #39 on: 11/06/2018 09:38 PM »
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
« Last Edit: 11/06/2018 09:51 PM by Rocket Science »
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