Author Topic: Thought Experiment: Man Rating OmegA  (Read 7642 times)

Thought Experiment: Man Rating OmegA
« on: 11/05/2018 07:54 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.
« Last Edit: 11/06/2018 08:47 am by JEF_300 »

Online JonathanD

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Re: Thought Experiment: Man Rating OmegA
« Reply #1 on: 11/05/2018 08:07 pm »
Aside from flaming hunks of solid rocket booster burning holes in your parachutes and killing your astronauts, sounds great.

Online ncb1397

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Re: Thought Experiment: Man Rating OmegA
« Reply #2 on: 11/05/2018 08:42 pm »
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.
« Last Edit: 11/05/2018 08:48 pm by ncb1397 »

Online vaporcobra

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Re: Thought Experiment: Man Rating OmegA
« Reply #3 on: 11/05/2018 09:12 pm »
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.

Online TomH

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Re: Thought Experiment: Man Rating OmegA
« Reply #4 on: 11/06/2018 01:38 am »
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?
« Last Edit: 11/06/2018 01:39 am by TomH »

Offline ChrisWilson68

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Re: Thought Experiment: Man Rating OmegA
« Reply #5 on: 11/06/2018 01:51 am »
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.

Offline IanThePineapple

Re: Thought Experiment: Man Rating OmegA
« Reply #6 on: 11/06/2018 02:06 am »
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

Re: Thought Experiment: Man Rating OmegA
« Reply #7 on: 11/06/2018 02:16 am »
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
« Last Edit: 11/06/2018 02:17 am by JEF_300 »

Offline ChrisWilson68

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Re: Thought Experiment: Man Rating OmegA
« Reply #8 on: 11/06/2018 02:44 am »
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.

Offline jaxon9182

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Re: Thought Experiment: Man Rating OmegA
« Reply #9 on: 11/06/2018 03:08 am »
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
« Last Edit: 11/06/2018 03:10 am by jaxon9182 »

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Re: Thought Experiment: Man Rating OmegA
« Reply #10 on: 11/06/2018 03:52 am »
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.

Re: Thought Experiment: Man Rating OmegA
« Reply #11 on: 11/06/2018 04:09 am »
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?
« Last Edit: 11/06/2018 04:30 am by JEF_300 »

Offline RonM

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Re: Thought Experiment: Man Rating OmegA
« Reply #12 on: 11/06/2018 05:07 am »
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.

Offline Steven Pietrobon

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Re: Thought Experiment: Man Rating OmegA
« Reply #13 on: 11/06/2018 05:28 am »
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).
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Re: Thought Experiment: Man Rating OmegA
« Reply #14 on: 11/06/2018 05:41 am »
... 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"
« Last Edit: 11/06/2018 05:41 am by JEF_300 »

Offline Steven Pietrobon

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Re: Thought Experiment: Man Rating OmegA
« Reply #15 on: 11/06/2018 05:57 am »
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.
« Last Edit: 11/06/2018 06:12 am by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online john smith 19

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Re: Thought Experiment: Man Rating OmegA
« Reply #16 on: 11/06/2018 08:12 am »
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.
Quote from: jaxon9182
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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Offline Fequalsma

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Re: Thought Experiment: Man Rating OmegA
« Reply #17 on: 11/06/2018 09:06 am »
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.

« Last Edit: 11/06/2018 09:08 am by Fequalsma »

Online ncb1397

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Re: Thought Experiment: Man Rating OmegA
« Reply #18 on: 11/06/2018 01:06 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. 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.
« Last Edit: 11/06/2018 01:13 pm by ncb1397 »

Offline Rocket Science

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Re: Thought Experiment: Man Rating OmegA
« Reply #19 on: 11/06/2018 01:17 pm »
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