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SRBs, LESs, Ejection Seats & 100% Oxygen Atmosphere (split from SpaceX Discussion)


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20 hours ago, sevenperforce said:

wonder why they didn't install thrust termination on the Shuttle SRBs. The first flights had ejection seats which would have saved the crew (or at least the crew with the ejection seats) in the event of a failure early in launch, but the SRB plumes would have cooked them, so it wasn't actually a survivable option. Unzipping the SRBs also would have cooked the ejecting crew. Thrust termination vents would have been the only survivable abort. I doubt it would have been a mass budget problem.

Still not survivable. The shuttle, especially in the early days, had huge “black zones,” where any kind of failure requiring an abort would be LOCV, either due to reentry stress on the orbiter or lack of thrust/control. Remember, at launch the boosters gave 90% of the stack’s thrust, until the orbiter/ET combo could accelerate itself, even “shutting off” the boosters would be LOCV.

The pilot/commander on those first few flights of Columbia pretty much knew if anything went wrong while the boosters were burning they were boned. Oddly enough, that part never changed with “operational” flights. :huh:

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1 hour ago, sevenperforce said:

I wonder why they didn't install thrust termination on the Shuttle SRBs. The first flights had ejection seats which would have saved the crew (or at least the crew with the ejection seats) in the event of a failure early in launch, but the SRB plumes would have cooked them, so it wasn't actually a survivable option. Unzipping the SRBs also would have cooked the ejecting crew. Thrust termination vents would have been the only survivable abort. I doubt it would have been a mass budget problem.

The justification on my mind is cartoonish, but fits perfectly with Shuttle logic: the additional vens and pyros would only increase the risks on a normal flight.

You know, the one supposed to happen once a fortnight.

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2 hours ago, CatastrophicFailure said:

Still not survivable. The shuttle, especially in the early days, had huge “black zones,” where any kind of failure requiring an abort would be LOCV, either due to reentry stress on the orbiter or lack of thrust/control. Remember, at launch the boosters gave 90% of the stack’s thrust, until the orbiter/ET combo could accelerate itself, even “shutting off” the boosters would be LOCV.

Why? If the crew eject safely, it shouldn’t matter if the vehicle cannot sustain flight for very long.

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2 hours ago, CatastrophicFailure said:

Still not survivable. The shuttle, especially in the early days, had huge “black zones,” where any kind of failure requiring an abort would be LOCV, either due to reentry stress on the orbiter or lack of thrust/control. Remember, at launch the boosters gave 90% of the stack’s thrust, until the orbiter/ET combo could accelerate itself, even “shutting off” the boosters would be LOCV.

The pilot/commander on those first few flights of Columbia pretty much knew if anything went wrong while the boosters were burning they were boned. Oddly enough, that part never changed with “operational” flights. :huh:

The first four Columbia missions flew with operational ejection seats for use in a LOV contingency abort. However, since they were only good for the first 100 seconds of ascent (due to altitude issues) and the boosters don't burn out until after that, any ejection would have launched the crew into the booster fire trail, which would have been unacceptably toasty. 

The only thing that would have made a contingency abort survivable would have been ejection seats combined with thrust termination on the SRBs. STS-5 and after had no ejection seats, of course, so booster thrust termination would have been LOCV. The one exception would have been a booster thrust shortfall somewhere between 90 and 120 seconds, the brief period during which the orbiter had just enough thrust to maintain acceleration but the SRBs had not yet separated. If one of the boosters experienced a thrust shortfall without actively breaking apart during this period, then conceivably they could have terminated thrust on both boosters and separated early, then completed a RTLS abort. 

Still rather limited utility.

1 hour ago, DDE said:

The justification on my mind is cartoonish, but fits perfectly with Shuttle logic: the additional vens and pyros would only increase the risks on a normal flight.

You know, the one supposed to happen once a fortnight.

The Shuttle was never more than an experimental launch system.

3 minutes ago, Ozymandias_the_Goat said:

Why? If the crew eject safely, it shouldn’t matter if the vehicle cannot sustain flight for very long.

Technically there are black zones within which even an ejection is not survivable because the crew would hit the atmosphere moving too fast to open chutes. That's one reason why the Dreamliner will launch on a never-before-used Atlas N22 with two RL-10s on the Centaur; the extra thrust on the Centaur means the first stage trajectory is less lofted. With a single Centaur, the first stage has to kick straight up to keep the apogee high enough to permit circularization, but an abort during first-stage boost ends up with an unacceptably high entry angle, even for a full capsule.

But yeah, I think @CatastrophicFailure misunderstood that I was talking about ejection seats.

Edited by sevenperforce
"fire trail" not "fire trial" which I suppose has similarity
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I didn't see the ejection seats on Shuttle having any actual utility during liftoff (any changes to the SRBs included) at all. I saw them as an alternative to ditching assuming the Orbiter was already at least gliding. Any thrust termination on Shuttle  SRBs would have had to also maintain a pretty delicate aerodynamic balance, or the thing gets torn apart, anyway, possibly before any ejection. It also strikes me that SRB failures have to be up there for risks, anyway, and they tend to fail like Challenger and that Delta II (?) launch from the 90s (burn throughs).

 

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9 minutes ago, tater said:

I didn't see the ejection seats on Shuttle having any actual utility during liftoff (any changes to the SRBs included) at all. I saw them as an alternative to ditching assuming the Orbiter was already at least gliding. Any thrust termination on Shuttle  SRBs would have had to also maintain a pretty delicate aerodynamic balance, or the thing gets torn apart, anyway, possibly before any ejection. It also strikes me that SRB failures have to be up there for risks, anyway, and they tend to fail like Challenger and that Delta II (?) launch from the 90s (burn throughs).

The real utility for the ejection seats was in the gliding approach if something major had gone wrong during the Enterprise tests.

Putting people on a rocket with solids is just a bad idea all around. SLS and Atlas V N22 included.

I'd wager decent money that if the SRBs could have had thrust termination between 90 and 120 seconds, they could have been separated a few seconds early without LOV. 

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I've heard that it's now thought that ejecting from Gemini at almost any flight state would have been fatal too.  Of the spacecraft that have been designed with ejection seats (Vostok, Gemini, the initial Shuttle flights), all we know for sure is that the Vostok seat works on recovery.

What I have wondered with the Shuttle is with what was learned about Challenger post-explosion, could it have been designed with the crew cabin as a survival pod.  Not quite like say the F-111 escape pod but something designed to withstand breakup of the launch vehicle and been aerodynamically stable.  And survived landing.  That would all be a tall order to design into the airframe without demanding more ship mass for it.  And it likely would have had a low expectation of utility and crew survival.  But damnit, some of the Challenger crew almost certainly survived until the cabin impact with the ocean.  I still wish something better could have been done.

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Just now, Jacke said:

I've heard that it's now thought that ejecting from Gemini at almost any flight state would have been fatal too.  Of the spacecraft that have been designed with ejection seats (Vostok, Gemini, the initial Shuttle flights), all we know for sure is that the Vostok seat works on recovery.

Gemini: They were mostly for landing in the paraglider thing, but the paraglider was replaced with a parachute and the  ejection seats were retained, as they had been extensively tested and there were a few scenarios where they might be useful, because the Titan II exploded differently from SRBs or something. But the testing was done with the capsules pressurized with nitrogen. After soaking in pure oxygen for hours before launch, if an ejection seat was used, it may have spread rapidly and cooked the astronauts alive.

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13 minutes ago, Jacke said:

I've heard that it's now thought that ejecting from Gemini at almost any flight state would have been fatal too.  Of the spacecraft that have been designed with ejection seats (Vostok, Gemini, the initial Shuttle flights), all we know for sure is that the Vostok seat works on recovery.

 

See the top pinned comment in this video about the Gemini ejection system.

https://www.youtube.com/watch?v=5IRdZjjq1Ik

 

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2 hours ago, sevenperforce said:

That's one reason why the Dreamliner will launch on a never-before-used Atlas N22 with two RL-10s on the Centaur

@tater summed it up better, but I would be very interested in seeing an Atlas strapped to a Dreamliner.  :sticktongue:

Spoiler

As long as no one’s on board.

Boeing_787_N1015B_ANA_Airlines_(27611880

 

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1 hour ago, Ultimate Steve said:

Gemini: They were mostly for landing in the paraglider thing, but the paraglider was replaced with a parachute and the  ejection seats were retained, as they had been extensively tested and there were a few scenarios where they might be useful, because the Titan II exploded differently from SRBs or something. But the testing was done with the capsules pressurized with nitrogen. After soaking in pure oxygen for hours before launch, if an ejection seat was used, it may have spread rapidly and cooked the astronauts alive.

 

1 hour ago, Reactordrone said:

See the top pinned comment in this video about the Gemini ejection system.

https://www.youtube.com/watch?v=5IRdZjjq1Ik

 

Yes, it's safer to be over top of an exploding rocket if it has hypergolic propellants.  I think it's because they can't mix prior to burning as any contact leads to burning, so the explosion progresses differently.  Still, it's a bad place to be.

And that's the video I watched to hear about the pure-oxygen threat to Gemini ejection.  Although there was a fatality in the Vostok ejection seat design and testing, it used an oxygen-nitrogen mix and at least worked for the 6 people and several animal missions.  Shuttle also had oxygen-nitrogen.  And yup, Gemini was initially planned to use the Rogallo paraglider wing and thus its ejection seats.  But in a pure-oxygen atmosphere.

Ejections from aircraft have had a number of injuries (including a pilot just in street clothes who barely survived ejecting at just over Mach 1), but Vostok itself had a clean record.  Still, it's likely really good no one did try to eject from Gemini.

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1 hour ago, Jacke said:

I've heard that it's now thought that ejecting from Gemini at almost any flight state would have been fatal too.  Of the spacecraft that have been designed with ejection seats (Vostok, Gemini, the initial Shuttle flights), all we know for sure is that the Vostok seat works on recovery.

What I have wondered with the Shuttle is with what was learned about Challenger post-explosion, could it have been designed with the crew cabin as a survival pod.  Not quite like say the F-111 escape pod but something designed to withstand breakup of the launch vehicle and been aerodynamically stable.  And survived landing.  That would all be a tall order to design into the airframe without demanding more ship mass for it.  And it likely would have had a low expectation of utility and crew survival.  But damnit, some of the Challenger crew almost certainly survived until the cabin impact with the ocean.  I still wish something better could have been done.

Successful chute deployment would have been the challenging part. I think they decided against the "cabin capsule" approach primarily because there was no way to build in large enough abort motors for a 0-0 abort, but it still would have been better than nothing in a Challenger situation. They would have needed to bake in detcord all around the crew cabin (which then becomes a hazard on its own) and pack chutes in a way that they would be protected during vehicle disintegration but still be able to pop during descent. Ridiculously difficult problem.

 

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49 minutes ago, sevenperforce said:

Successful chute deployment would have been the challenging part. I think they decided against the "cabin capsule" approach primarily because there was no way to build in large enough abort motors for a 0-0 abort, but it still would have been better than nothing in a Challenger situation. They would have needed to bake in detcord all around the crew cabin (which then becomes a hazard on its own) and pack chutes in a way that they would be protected during vehicle disintegration but still be able to pop during descent. Ridiculously difficult problem.

In some ways, the design of the Shuttle was somewhat doomed when the budget got cut (about 1969 or so) and NASA could no longer entertain a fully reusable Shuttle on a fully reusable crewed booster craft.  The semi-reusable design they settled on was just what could be done.  And of course it needed the big wings for the DoD cross-range requirement for a Vandenberg once-around launch.  Which it never did.

The shear amount of refit required for the Shuttle also did in the launch schedule and cost expectations.  As mentioned, in many ways it was always an experimental craft.  And I do believe a lot was learned about what could be done and what shouldn't be done.

Edited by Jacke
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1 hour ago, CatastrophicFailure said:

@tater summed it up better, but I would be very interested in seeing an Atlas strapped to a Dreamliner.  :sticktongue:

  Hide contents

As long as no one’s on board.

Boeing_787_N1015B_ANA_Airlines_(27611880

 

Don’t forget to not include an engine shutdown button, and to keep the press directly onboard the launcher airplane.

main-qimg-7b3f241507086b69e6fb1f34d88913

Only a Kryptonian would save you then.

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1 hour ago, Jacke said:

In some ways, the design of the Shuttle was somewhat doomed when the budget got cut (about 1969 or so) and NASA could no longer entertain a fully reusable Shuttle on a fully reusable crewed booster craft.  The semi-reusable design they settled on was just what could be done.  And of course it needed the big wings for the DoD cross-range requirement for a Vandenberg once-around launch.  Which it never did.

The shear amount of refit required for the Shuttle also did in the launch schedule and cost expectations.  As mentioned, in many ways it was always an experimental craft.  And I do believe a lot was learned about what could be done and what shouldn't be done.

It is a good learning experience, yes, but at the cost of too many lives.

The crossrange requirement was pathetic.

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10 hours ago, sevenperforce said:

I wonder why they didn't install thrust termination on the Shuttle SRBs.

Because Thiokol's SRBs are the perfectly reliable wave of the future, don't you know?

Also that it would've doomed the crew for most of the SRB duration, as RTLS was outright impossible until the Shuttle obtained enough energy to not just crash back down. It'd only be useful in the last segment of the SRB burn.

6 hours ago, sevenperforce said:

Putting people on a rocket with solids is just a bad idea all around. SLS and Atlas V N22 included.

It's not the safest thing in the world, but a lot of the risks involved in SRB use are strongly mitigated in the SLS and Atlas V/Starliner combination.

Both have a functional launch abort system to get astronauts off the stack. Neither has the crew cabin too perilously close to the SRBs.

Furthermore, for the Atlas V, the SRBs are relatively small compared to the booster core. This means that if there is some major problem, the liquid engines can shut down, and the core stack TWR will not be too high even with the SRBs burning, giving the Starliner more time to escape and separate from any wee little "fragments of still-burning SRB exhaust". This also gives a liquid-only TWR of almost 1.0 at launch, meaning sudden loss of SRB thrust does not immediately mean fall-back-to-the-ground except in the first seconds of flight. They're also well-proven designs, and I think they're monolithic, without the multi-segment joints of the SLS boosters.

2 hours ago, sevenperforce said:

The crossrange requirement was pathetic.

Remember: the Shuttle was thought to be a wonderful vehicle that would be the future of space travel. NASA thought it was invincible. Why not add in cross-range capability? We landed people on the freaking Moon!

Then reality ensued.

4 hours ago, Jacke said:

And that's the video I watched to hear about the pure-oxygen threat to Gemini ejection.  Although there was a fatality in the Vostok ejection seat design and testing, it used an oxygen-nitrogen mix and at least worked for the 6 people and several animal missions.  Shuttle also had oxygen-nitrogen.  And yup, Gemini was initially planned to use the Rogallo paraglider wing and thus its ejection seats.  But in a pure-oxygen atmosphere.

I'm not convinced the pure-oxygen cabin would be a huge threat in event of an ejection. Sure, they would've been followed out by a good old blast of oxygen... that would very quickly dissipate. Probably slightly less safe than the originally-tested 80% nitrogen atmosphere, but the dangers of a 1-atmosphere oxygen partial pressure are easy to overstate: the astronauts would be removing themselves from said environment with much haste.

(also, it's a pet peeve of mine when people speak of the dangers of a pure oxygen environment. It's not the purity that's the issue: I'm pretty sure the ISS runs at 100% oxygen at 0.22 atm. It's having 1 full atmosphere partial pressure of oxygen that gets stuff extra-flammable).

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6 minutes ago, Starman4308 said:

Furthermore, for the Atlas V, the SRBs are relatively small compared to the booster core. This means that if there is some major problem, the liquid engines can shut down, and the core stack TWR will not be too high even with the SRBs burning, giving the Starliner more time to escape and separate from any wee little "fragments of still-burning SRB exhaust". This also gives a liquid-only TWR of almost 1.0 at launch, meaning sudden loss of SRB thrust does not immediately mean fall-back-to-the-ground except in the first seconds of flight. They're also well-proven designs, and I think they're monolithic, without the multi-segment joints of the SLS boosters.

I would think the most likely SRB failure mode has them blowing up the liquid tank.

 

7 minutes ago, Starman4308 said:

Remember: the Shuttle was thought to be a wonderful vehicle that would be the future of space travel. NASA thought it was invincible. Why not add in cross-range capability? We landed people on the freaking Moon!

Then they never used this 1 orbit landing capability, right? Grrr.

 

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1 minute ago, tater said:

I would think the most likely SRB failure mode has them blowing up the liquid tank.

And, like many such failures, that boils down to "does the LES work?"

LRBs aren't immune to blowing up their own tanks either, though those can be shut down early if the need arises. Either way, it's probably a mission-abort scenario where the LES probably needs to work.

Nothing's perfect, but I'm pretty sure the SRBs of today aren't quite as terrible of an idea as the original Shuttle SRBs... and they're certainly being used in a safer context (i.e. there's an LES).

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7 minutes ago, Starman4308 said:

And, like many such failures, that boils down to "does the LES work?"

LRBs aren't immune to blowing up their own tanks either, though those can be shut down early if the need arises. Either way, it's probably a mission-abort scenario where the LES probably needs to work.

Nothing's perfect, but I'm pretty sure the SRBs of today aren't quite as terrible of an idea as the original Shuttle SRBs... and they're certainly being used in a safer context (i.e. there's an LES).

Yeah, absolutely better, no question.

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21 minutes ago, Starman4308 said:

Because Thiokol's SRBs are the perfectly reliable wave of the future, don't you know?

The thing about Thiokol's SRBs that still gets me is they're designed with the intersegment joint open side facing up.  The Titan III SRB's (designed and built by United Aircraft, later UTC) had their joints' open end facing down.  Which to me only makes sense.

https://en.wikipedia.org/wiki/UA120

And for crew rating, "Thrust-termination capability, necessary for manned rockets such as the Space Shuttle or Manned Orbiting Laboratory, was to be provided by two pyrotechnically triggered ports on the forward closure, which when opened would allow for the non-propulsive venting of exhaust gasses."

 

Quote

I'm not convinced the pure-oxygen cabin would be a huge threat in event of an ejection. Sure, they would've been followed out by a good old blast of oxygen... that would very quickly dissipate. Probably slightly less safe than the originally-tested 80% nitrogen atmosphere, but the dangers of a 1-atmosphere oxygen partial pressure are easy to overstate: the astronauts would be removing themselves from said environment with much haste.

(also, it's a pet peeve of mine when people speak of the dangers of a pure oxygen environment. It's not the purity that's the issue: I'm pretty sure the ISS runs at 100% oxygen at 0.22 atm. It's having 1 full atmosphere partial pressure of oxygen that gets stuff extra-flammable).

Ah, no.  5 hours soaked in pure oxygen and still being in it is just massively more flammable.  There's Nick Lane's book _Oxygen_ which contains a whole lot about how oxygen is that way and how it's shaped our planet and biology.  2 atmospheres of pure oxygen is fatal within 24 to 48 hours.  And you die the same way that massive radiation kills, by the increased level of reactive oxygen free radicals like the superoxide and hydroxyl radicals that just swamps the body's cells' ability to get rid of them and repair the damage they cause.

Edited by Jacke
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12 minutes ago, Jacke said:

Ah, no.  5 hours soaked in pure oxygen and still being in it is just massively more flammable.  There's Nick Lane's book _Oxygen_ which contains a whole lot about how oxygen is that way and how it's shaped our planet and biology.  2 atmospheres of pure oxygen is fatal within 24 to 48 hours.  And you die the same way that massive radiation kills, by the increased level of reactive oxygen free radicals like the superoxide and hydroxyl radicals that just swamps the body's cells' ability to get rid of them and repair the damage they cause.

Does oxygen absorb significantly into things like fabric? I'd imagine the local partial O2 pressure would drop tremendously in the seconds after ejection, going from 1 atm to local atmospheric conditions (potentially very low in upper atmosphere).

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1 hour ago, Starman4308 said:

It's not the safest thing in the world, but a lot of the risks involved in SRB use are strongly mitigated in the SLS and Atlas V/Starliner combination.

Both have a functional launch abort system to get astronauts off the stack. Neither has the crew cabin too perilously close to the SRBs.

Did they do something since the Ares I about the SRB fragments melting parachutes?

http://images.spaceref.com/news/2009/fratricide.report.pdf

EDIT: Atlas V might have different SRBs, but I understood SLS SRBs to be virtually identical to Ares I ones.

Edited by Mad Rocket Scientist
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1 hour ago, Starman4308 said:

Does oxygen absorb significantly into things like fabric? I'd imagine the local partial O2 pressure would drop tremendously in the seconds after ejection, going from 1 atm to local atmospheric conditions (potentially very low in upper atmosphere).

I couldn't find good references to be sure about this, but I'd say from the experiences of the hazards of pure oxygen, I'd not assume a particular mechanism of accident would remove the threat that fast.

For example, there are a greater range of flammable mixtures with methane as the proportion of oxygen goes up.

https://en.wikipedia.org/wiki/Flammability_diagram

And there's a large number of advised safety precautions when dealing with any oxygen enriched atmosphere.  Take a gander at some in this report, including the one where hydrocarbon vapour settled on the inside of an oxygen line ruptured the line just from igniting from the heating of the oxygen caused by closing a valve.

https://www.airproducts.com/~/media/Files/PDF/company/safetygram-33.pdf

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2 hours ago, Starman4308 said:

I'm pretty sure the ISS runs at 100% oxygen at 0.22 atm.

No, it doesn’t. If only because Russians are involved.

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