Abort options for Starship and Starship/SuperHeavy

[Lee Jay]

In my opinion, the real challenge will be making starship itself hardened so that it doesn’t have any failures itself. I think it’s totally pluasible for a sufficiently designed starship to abort from a failed super heavy booster.

Perhaps, but it's not plausible to design something, "so that it doesn’t have any failures itself" unless you use it so little that you stop using it before it fails.  Given sufficient trials, everything will eventually have some sort of failure.

...which applies also to launch abort systems.

Which would be relevant except that failures are reasonably assumed to be independent.

[TheRadicalModerate]

Yeah, but single digit milliseconds is also faster than a dedicated LAS would work anyway.

Kinda depends on the shock from the initial explosion, which wasn't huge.  If you listen to the (distance-delayed) audio, the really big explosion is when the second stage collapsed into the first stage. 

The fireball isn't really the problem.  It's the shock that's the problem.  If the D2 could survive the first smaller shock, it probably would have been far enough away to survive the big shock.

I don't mean to imply that Amos 6 would certainly have been survivable with escape.  But it would have been a lot closer to survivable than it looked, and might have been actually survivable, if there'd been a D2 in place instead of a payload fairing.

There's no getting around the fact that the Starship upperstage has to be significantly hardened to achieve the safety required. And you can't "abort from an abort" (unless we're prepared for absurdities...).

What do you mean by "hardened"?  That the crew has to survive hitting the ground at terminal speed?  That the entire Starship has to be able to survive a shock overpressure of 1-2bar?  That all conceivable failure paths that lead to a large-scale methalox explosion on the Starship itself have to be closed off?

As for aborting from an abort:  Of course that's absurd.  But it's also absurd trying to pretend that an escape system needs anywhere near the reliability of the primary system to significantly improve the overall crew survivability.

Starship is a long Dragon with more propellant.

I can't tell if you're joking here.  If you mean a Starship with lousy T/W for escape, long interval between warning and separation, no parachutes, a propulsion and tankage system that's more exposed to shrapnel and heat pulse, and no way to land safely off of the chopsticks, then yeah, it's exactly like a long Dragon with more propellant.

[clongton]

All this whining and nitpicking the dangers associated with a hot fire abort make me just cringe. It seems to me we have 2 choices, and ONLY 2 choices.
1. Quit altogether trying to launch people on a rocket because we're too scared of getting hurt -or-
2. Acknowledge that launching people on rockets will never ever, ever, ever be safe. So do the best we can to mitigate whatever we can, accept the risks, suck it up, and get on the rocket and fly.

[Lee Jay]

All this whining and nitpicking the dangers associated with a hot fire abort make me just cringe. It seems to me we have 2 choices, and ONLY 2 choices.
1. Quit altogether trying to launch people on a rocket because we're too scared of getting hurt -or-
2. Acknowledge that launching people on rockets will never ever, ever, ever be safe. So do the best we can to mitigate whatever we can, accept the risks, suck it up, and get on the rocket and fly.

That just isn't so.

There are ways to design rockets to be safer than the design of Starship, and there are practical and proven abort options for various stages of flight.

[volker2020]

All this whining and nitpicking the dangers associated with a hot fire abort make me just cringe. It seems to me we have 2 choices, and ONLY 2 choices.
1. Quit altogether trying to launch people on a rocket because we're too scared of getting hurt -or-
2. Acknowledge that launching people on rockets will never ever, ever, ever be safe. So do the best we can to mitigate whatever we can, accept the risks, suck it up, and get on the rocket and fly.

I think we have 3 groups here:
 a) people that are upset about Airline Like Point to Point Starship connections and the risk assessment of this, arguing that it should not be two or more magnitudes more risky to fly from a to b.
 b) people assuming that a abort system is a must have, since it might improve chances of survival and feel it necessary.
 c) people that for various reasons don't want Starship to succeed in any way.
I think it is impossible to get the risk ratios, before the ship has even started. I started a discussion about hot staging an launch abort a while ago. My main concern, that 6 gigantic blow torches would concentrate there energie on 81 squaremeter of 4mm thick steel, with tons of liquid methane just below. I tried a little math on the problem to find out, if you could start the engines in a confined space, to see how much energy could be confined before the methane tank ruptures. I am still not convinced it could work, but it is really a tricky problem. What I am sure about is, that at some point SpaceX will put this question to a test, and either decide that blowdoors or an interstage with enough shielding can keep the tank save until Starship is away, or decide that it does now work, and start with another migrations. But if it works or not is really not important. Because the only important question is, how many errors can not be migrated and cause the lost of human life and is this number higher than what people using this system are willing to risk. Any risk we put on here is artificial. If people had not taken risks, we would neither cross the oceans or started flying, and the same will be true for reaching space.
 

[clongton]

All this whining and nitpicking the dangers associated with a hot fire abort make me just cringe. It seems to me we have 2 choices, and ONLY 2 choices.
1. Quit altogether trying to launch people on a rocket because we're too scared of getting hurt -or-
2. Acknowledge that launching people on rockets will never ever, ever, ever be safe. So do the best we can to mitigate whatever we can, accept the risks, suck it up, and get on the rocket and fly.

That just isn't so.

There are ways to design rockets to be safer than the design of Starship, and there are practical and proven abort options for various stages of flight.

You are obviously in the option 2 camp, as am I. I agree with your assessment of Starship's safety potential but that wasn't my point. Starship will never be as safe to fly as an airline - ever - and my point was to identify the potential risks, eliminate what you can, mitigate what's left as much as possible, then accept what's left and then just get on board and fly it.

Every human spacecraft that has ever been built is handled this way.

[TheRadicalModerate]

That just isn't so.

There are ways to design rockets to be safer than the design of Starship, and there are practical and proven abort options for various stages of flight.

You are obviously in the option 2 camp, as am I. I agree with your assessment of Starship's safety potential but that wasn't my point. Starship will never be as safe to fly as an airline - ever - and my point was to identify the potential risks, eliminate what you can, mitigate what's left as much as possible, then accept what's left and then just get on board and fly it.

Almost everybody on the thread is in the option 2 camp.  But I don't believe you can just get on board and fly it until it hits some valid estimation for an acceptable pLOC, which will vary depending on the application.  My guesses:

- Private informed-risk groups of ~12:  pLOC < 5E-3
- NASA crews:  pLOC < 3.7E-3
- Informed-risk groups of ~100: pLOC < 1E-4
- Common carrier groups of ~100: pLOC < 1E-7

All of these likely have somewhat more stringent rules for launch and EDL.

I also don't think you're dividing the opinions correctly.  If I were doing a poll, I'd put forth the following propositions:

1) Starship can never be human rated.

2) Starship can only be human rated with the addition of an escape system that can separate the crew from the larger Starship, both for launch and EDL.  Such a system will limit crew size to ~12 with informed risk and permanently preclude its use as a common carrier.

3) Starship architecture can be human rated as-is, up to NASA-ish standards, by maturing the architecture, getting lots of empirical data, and eventually applying probabilistic risk assessment to refine the architecture.  Crew size could then be ~100 with informed risk, for LEO and BEO transport.  But it will never be rated up to FAA common carrier standards.

4) Starship can eventually be matured to be a common carrier, which would allow point-to-point passenger service for non-informed-risk groups of ~100.

Personally, I'd vote for option #2 if the time horizon is before the end of the decade, and maybe option #3 if SpaceX feels it can wait 10-15 years before flying humans.

Time is a big factor here.  I believe that there are missed opportunities if SpaceX can't crew-rate by 2030, and 2028 would be a lot better.  That's why I'm an "escape" advocate; they can implement escape with less flight data, and higher probabilities for the loss of the vehicle.

"Escape" is just one more nose design.  If, later on, the data supports it, they can replace it with a "passenger" nose.

[TheRadicalModerate]

I started a discussion about hot staging an launch abort a while ago. My main concern, that 6 gigantic blow torches would concentrate there energie on 81 squaremeter of 4mm thick steel, with tons of liquid methane just below. I tried a little math on the problem to find out, if you could start the engines in a confined space, to see how much energy could be confined before the methane tank ruptures. I am still not convinced it could work, but it is really a tricky problem.

None of this helps with landing.  So even if you wind up being able to hot-stage (and I think you're defining the hardest problem correctly), you still don't have an adequately safe solution without an escape mechanism.

[Lee Jay]

Personally, I'd vote for option #2 if the time horizon is before the end of the decade, and maybe option #3 if SpaceX feels it can wait 10-15 years before flying humans.

I agree.

[InterestedEngineer]

I started a discussion about hot staging an launch abort a while ago. My main concern, that 6 gigantic blow torches would concentrate there energie on 81 squaremeter of 4mm thick steel, with tons of liquid methane just below. I tried a little math on the problem to find out, if you could start the engines in a confined space, to see how much energy could be confined before the methane tank ruptures. I am still not convinced it could work, but it is really a tricky problem.

None of this helps with landing.  So even if you wind up being able to hot-stage (and I think you're defining the hardest problem correctly), you still don't have an adequately safe solution without an escape mechanism.

Do you mean landing after a hot abort away from the booster, or some other landing scenario?

[clongton]

Very few people are thinking of a picture as big as Elon Musk is thinking.
They are desperately trying to find a way to rationalize shrinking HIS vision down to THEIR size because they can't think that big, instead of looking at what he says he is going to do and trying to visualize how he can do THAT. For example, when he says there will be scores of people onboard Starship as crew, that's not code for 12. He means scores of people, all at once. For example, the Dear Moon mission won't use Dragons to meet Starship in LEO. The entire complement will launch on Starship from the ground, all at once.  Remember NASA is **NOT** the be all, do all of what people are and are not allowed to do. As grateful as he is for NASA saving SpaceX from extinction in the beginning, he does not need and will never ask for NASA's permission to do anything. Remember he was building Starship way before NASA invented Artemis. He was doing it with his own money and had absolutely no intention of going to the moon at all. Starship is not being built for NASA. It never was. People tend to forget that. Right from the beginning he said he intended to fly Starship from the ground fully crewed for Mars missions. He has no intention of using Falcon/Dragon to fly the Starship crew into orbit, piecemeal, to meet Starship. Falcon/Dragon is going away. Elon said so. He plans to launch Starship fully crewed from the ground, because Falcon/Dragon won't even exist any more. The future of SpaceX human spaceflight is Starship, and only Starship. Again, Elon said so. Dragon will be a fond memory. Starship will launch - from the ground - fully crewed. If that scares anyone, well they're probably in the majority because, like I said up front, very few people seem able to even comprehend a vision as big as his. Perhaps a vision re-think is in order.

[TheRadicalModerate]

I started a discussion about hot staging an launch abort a while ago. My main concern, that 6 gigantic blow torches would concentrate there energie on 81 squaremeter of 4mm thick steel, with tons of liquid methane just below. I tried a little math on the problem to find out, if you could start the engines in a confined space, to see how much energy could be confined before the methane tank ruptures. I am still not convinced it could work, but it is really a tricky problem.

None of this helps with landing.  So even if you wind up being able to hot-stage (and I think you're defining the hardest problem correctly), you still don't have an adequately safe solution without an escape mechanism.

Do you mean landing after a hot abort away from the booster, or some other landing scenario?

Both.  All landing scenarios require a flip maneuver.  If that maneuver fails, the crew dies.

[InterestedEngineer]

I started a discussion about hot staging an launch abort a while ago. My main concern, that 6 gigantic blow torches would concentrate there energie on 81 squaremeter of 4mm thick steel, with tons of liquid methane just below. I tried a little math on the problem to find out, if you could start the engines in a confined space, to see how much energy could be confined before the methane tank ruptures. I am still not convinced it could work, but it is really a tricky problem.

None of this helps with landing.  So even if you wind up being able to hot-stage (and I think you're defining the hardest problem correctly), you still don't have an adequately safe solution without an escape mechanism.

Do you mean landing after a hot abort away from the booster, or some other landing scenario?

Both.  All landing scenarios require a flip maneuver.  If that maneuver fails, the crew dies.

several mitigations:

1.  Do flip at high enough altitude that something else can be done
2.  Do flip over water.  The failed flip  (SN9) hit at 50m/sec, which is survivable in water if tail or belly hits
3.  Do flip at high enough altitude to use backup parachutes.   Slow to < 50m/sec into water

All these take additional mass, but mass is something SpaceX can easily trade for safety, they have mass to burn for human rating.

[Lee Jay]

2.  Do flip over water.  The failed flip  (SN9) hit at 50m/sec, which is survivable in water if tail or belly hits

And it doesn't explode into a fireball like SN9 did.

Surviving anything other than a perfect landing would be shear luck.

[TheRadicalModerate]

The future of SpaceX human spaceflight is Starship, and only Starship. Dragon will be a fond memory. Starship will launch - from the ground - fully crewed. If that scares anyone, well they're probably in the majority because, like I said up front, very few people seem able to even comprehend a vision as big as his. Perhaps a vision re-think is in order.

Elon's vision needs to survive federal regulation.  Congress is in receipt of a document that recommends that the moratorium of FAA regulation of spaceflight be allowed to expire this October.  It's not clear if that will happen, but it's coming soon enough that it will affect crewed operation of Starship. Do you really think that SpaceX being reckless with human spaceflight safety will force the FAA to under-regulate them?

There's a way to get from where we are to Elon's vision, but it'll require a bit more patience, and it'll require looking squeaky clean from a PR standpoint.  Groups of 12 will work fine for 10-15 years, because nobody's sending scores of people to Mars any time soon.

So they start with an escapable system.  It'll be more than adequate for all cislunar tasks.  It'll allow SpaceX to gain experience with the system (hundreds if not thousands of flights) with adequately low pLOCs.  If there's a fatal accident, SpaceX will look like the responsible actor that I'm pretty sure they want to be--but the appearance is just as important as the actual fact.

A system like this is perfectly capable of feeding crew up for the first Mars missions, which will of course be incredibly high-risk operations, and will have pLOC regulations modified accordingly.

Then... we'll see.  At the very least, SpaceX will be able to launch Mars-bound crews with regulations that suit the risk.  More likely, they'll learn so much about Starship that they'll be able to modify the architecture to improve its safety, and really get to the goal of launching scores of people under whatever regulations the FAA promulgates.

I think Elon's Kool-Aid tastes really good too.  But it's important not to let yourself be... over-served.

[Robotbeat]

Quit trying to make a separate abort system happen. It’s not gonna happen. Spending billions to develop a separate abort system will only lock you into a fundamentally less safe approach that relies on dangerous, rarely used subsystems instead of fundamental safety. And leaves you defenseless on Mars and the Moon. Far better to invest in intrinsic safety and flight reliability.

[chopsticks]

All these take additional mass, but mass is something SpaceX can easily trade for safety, they have mass to burn for human rating.

Yep exactly. Like extra mass for a proper abort system. Plenty of mass and volume to work with for that.

[Robotbeat]

All these take additional mass, but mass is something SpaceX can easily trade for safety, they have mass to burn for human rating.

Yep exactly. Like extra mass for a proper abort system. Plenty of mass and volume to work with for that.

Why would SpaceX want to expose astronauts to the extra risk of such a system?

The risk of a pRoPeR abOrT sYStEm (on a NOMINAL admission) is higher than would ever be acceptable for airline flight.

[chopsticks]

All these take additional mass, but mass is something SpaceX can easily trade for safety, they have mass to burn for human rating.

Yep exactly. Like extra mass for a proper abort system. Plenty of mass and volume to work with for that.

Why would SpaceX want to expose astronauts to the extra risk of such a system?

The risk of a pRoPeR abOrT sYStEm (on a NOMINAL admission) is higher than would ever be acceptable for airline flight.

Extra risk? I would say that the extra risk is just winging it and expecting that everything is going to work out. Plus if Starship is reliable without any triggered aborts, they can surely make such an abort system that much safer as well, even if they never have to use it. If they're able to make 33 raptor engines work together, they can surely make a reliable abort system.

I hope that Starship is successful however it ends up being designed, but there's another aspect of this all that shouldn't be overlooked. If crewed starship (as currently planned as we know it without an abort system) suffers LOC (or multiple), there's a good chance that the regulators could get involved and might require such a system. I'm not predicting that this will happen, but I think it's worth bearing in mind.

Also think of this: most military aircraft have ejection seats, though rarely used. Should we just stop putting them in airplanes because they add additional complexity?

[chopsticks]

On a side note - I would love to be a fly on the wall at certain moments at SpaceX. Elon Musk occasionally makes comments about "internal debates", I bet there are people at SpaceX having some of these same discussions. There are probably lots of different opinions there as well.. I wish I could hear some of them!