Abort options for Starship and Starship/SuperHeavy

[InterestedEngineer]

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land.

It's the 'abort to some place not a normal landing spot with a QD' that is the problem.

Another reason to favor a water landing.  Cools down the hot end almost immediately.  Disperses the outgassing into humid windy air.

[eriblo]

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land.

It's the 'abort to some place not a normal landing spot with a QD' that is the problem.

Another reason to favor a water landing.  Cools down the hot end almost immediately.  Disperses the outgassing into humid windy air.

There is unlikely to be anything hot enough to ignite methane on a landed Starship.

[maquinsa]

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land.

It's the 'abort to some place not a normal landing spot with a QD' that is the problem.

Another reason to favor a water landing.  Cools down the hot end almost immediately.  Disperses the outgassing into humid windy air.

There is unlikely to be anything hot enough to ignite methane on a landed Starship.

Please remind that to SN10 

[chopsticks]

The trucks don’t have super thick walls, there’s plenty of boiloff. Starship will have more but it could use a similar strategy.

I did a bit of reading on tanker trucks and it looks like they may be required to have a holding time of 5 days (no venting). https://unece.org/DAM/trans/doc/2011/wp29grpe/LNG_TF-02-06e.pdf

This is a far cry from Starship, at least from what we can tell. It vents a lot to keep from blowing up. Just look at the intentional press to destruction tank tests that were carried out in the past. It didn't take long at all for them to rupture after the valves were shut.

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land. 

What methane and lox is left is very little in comparison to what the tanks can hold, but it is still quite a bit - a whole truckload (if that's what it is) would still make pretty big bang - certainly enough to destroy the vehicle and potentially kill the crew I think. Just look at the fireballs that the failed landings of the SN tests made. And if it lands on a landing pad, where does the QD come from? Something is going to have to approach the Starship and connect to it. Question is, could this be done robotically (what sort of robot?) or would there have to be a "red team" everytime it lands to hook it up manually? It's pretty normal to try to avoid going near to a pressurized rocket (humans) and for this to be a routine practice sounds a bit dubious and risky to me. Not to mention that the engines will be hot and an easy source of ignition for any stray methane gasses.

I agree that 30 minutes is a reasonable time to wait to disembark, but can the vehicle be safed on the pad in this amount of time? Until it's safed, the vehicle is in an potentially dangerous situation where it's still pressurized with explosive methane that needs to be drained, but not enough propellant to try to re-land. I would think that pad abort capability would be a requirement until it's been safed. After it's been safed, the crew disembarks, until then the abort system remains active.

IF current practices used in tanker trailers or such as Robotbeat is suggesting could be implemented into Starship, the vehicle could remain pressurized with low enough boiloff not to matter. This would in theory work fine - the crew could disembark nearly immediately after landing (maybe wait a bit for the engines to cool) with the tanks still pressed. Not a great deal of risk of tank rupture if the prop is kept cool. However, all of this insulation seems like it would add quite a bit of extra mass. Are cryo-coolers an option?

[chopsticks]

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land.

It's the 'abort to some place not a normal landing spot with a QD' that is the problem.

Another reason to favor a water landing.  Cools down the hot end almost immediately.  Disperses the outgassing into humid windy air.

There is unlikely to be anything hot enough to ignite methane on a landed Starship.

As long as there's methane, there's always a risk of ignition. The hot engines are such an example. Even some static or spark from the environment can pose a risk. RE: the explosion on B7's spin prime test.

[eriblo]

When the Starship lands, it will have very little methane or lox left.  Like someone said, maybe a truck load.  A QD could be attached and the liquid methane drained into one or two trucks.  Oxygen could be vented.  Since there would be very little methane left, it shouldn't take long to drain. 

The engines probably would need to be cooled down to avoid an accidental flash point.  30 minutes shouldn't be that long a wait to deboard.  A truck with a lifting enclosed lift platform could allow the crew or passengers to deboard, lower and drive away. 

Abort is another thing.  Maybe the Starship can ignite the engines quick enough to separate from the booster in case it needed to, then fly back to a safe spot to land.

It's the 'abort to some place not a normal landing spot with a QD' that is the problem.

Another reason to favor a water landing.  Cools down the hot end almost immediately.  Disperses the outgassing into humid windy air.

There is unlikely to be anything hot enough to ignite methane on a landed Starship.

As long as there's methane, there's always a risk of ignition. The hot engines are such an example. Even some static or spark from the environment can pose a risk. RE: the explosion on B7's spin prime test.

Yes, of course. It has been proven again and again that the assumption of no ignition source is never good enough to get away with having explosive mixtures.

It was more a comment on the assumption that the engines are hot enough to ignite methane in air which is unlikely to be true even when operating and especially not after they have shut down.

[sebk]

Survivable re-entry emergencies would be stuff like when one of the fins seized and controls are now very limited and surviving hypersonic portion takes priority and let's worry about landing spot once the vehicle is transsonic.

And at this point you have no idea what the cross range capacity is and very little time to find out.  There will not be a lot of choices, the automation needs to pick one of the less awful ones PDQ.

Yes, you have about 20km diameter circle to chose landing spot from. Not great, not hopeless.

20km seems generous.  Falcon-9 landings go transsonic at about 8 km altitude.  Can it do a 45° glide?  Are the numbers for SS very different?  Also some of your controls have failed, your cross range may be close to zero, or in an unexpected direction.

Starship is supposed to transition to subsonic around 22-24km up. So says Cape Starship EA and so say various materials released by SpaceX. Also, Starship has about 0.5:1 glide ratio, it demonstrated flying forward during Sn-8 - Sn-15 test campaign. So 10km radius / 20km diameter seems plausible

[TheRadicalModerate]

Why do airplanes evacuated after crash landings with a decently large chunk of fuel on board?

That's totally different. Liquid kerosene is stable at atmospheric pressure and density, cryogenic methane and oxygen are not. The tanks they are in have to be vented to prevent them from exploding, very much not the case with kerosene.

And gaseous methane + oxygen living next door to each other is just way more explody than jet fuel.

It's this second point that's the important one.  If there's any kind of fire on landing, the chances of it becoming an explosion are extremely high.  Aircraft passengers evacuate from burning airplanes not only because Jet-A is fairly stable but also because evacuating through flaming wreckage has a lower chance of burning to death than sitting in an aluminum airframe soaked in burning jet fuel.

None of this is important for Starship.  If there's a fire, it doesn't really matter if you're sitting in the cabin waiting to be blown to smithereens or running away when you're blown to smithereens.

All that said, if you successfully land in a cow pasture somewhere and you're stable, then I suspect that you can develop a venting algorithm that reduces the chance of a big deflagration event, even if it takes a long time.  You're no longer optimizing for reduced valve wear and tear.  Lots of little vents are now better than fewer big vents.  Even if some of them cause deflagrations, they may be small enough to survive.  (Of course, now the cow pasture itself is on fire, which isn't particularly good.)

However, it's mostly the "stable" part that I question--and not just in the cow pasture.  There are so many different pathological ways to be off-nominal that getting the hell away from the whole mess via escape seems essential.

[Lee Jay]

However, it's mostly the "stable" part that I question--and not just in the cow pasture.  There are so many different pathological ways to be off-nominal that getting the hell away from the whole mess via escape seems essential.

A guy I know had a flame out in a classic plane (one of my favorites) and landed in a dead-flat farm.  It still destroyed the plane because there were irrigation ditches in the farm and he hit one, tearing off the landing gear and starting a fire.

He got out okay but the plane burned to the ground.

[darkenfast]

How about a vent that includes an igniter? It wouldn't run all the time, of course, just enough to keep the pressure under control until other methods can be hooked up. Alternate venting/burning methane with venting LOX.

[chopsticks]

How about a vent that includes an igniter? It wouldn't run all the time, of course, just enough to keep the pressure under control until other methods can be hooked up. Alternate venting/burning methane with venting LOX.

In other words, a built in flare stack? I think Hopper had this, no?

[InterestedEngineer]

How about a vent that includes an igniter? It wouldn't run all the time, of course, just enough to keep the pressure under control until other methods can be hooked up. Alternate venting/burning methane with venting LOX.

In other words, a built in flare stack? I think Hopper had this, no?

Still trying to figure out what the worry is.

Starship and Booster vent methane all the time 10s of meters up in the air, with no special provision for burning it off.

As long as there's a wind, it's fine.

The OLM deflagration happened because there was no wind in a semi-enclosed area.

[docmordrid]

>
I haven't seen any drawings or sketches of legs that are wider than the base of the vehicle,
>

Published by SpaceX and NASA (crop)

[chopsticks]

How about a vent that includes an igniter? It wouldn't run all the time, of course, just enough to keep the pressure under control until other methods can be hooked up. Alternate venting/burning methane with venting LOX.

In other words, a built in flare stack? I think Hopper had this, no?

Still trying to figure out what the worry is.

There are a few issues. Since this is a thread about abort capability, the issue is with crew and ground personnel. Humans don't normally approach a pressurized rocket (other than slightly pressurized to maintain structual integrity), especially not one that is pressurized with actual propellant, "red team" notwithstanding.

With F9, the crew board and get situated. The propellant load begins and the abort system is armed. Basically, as long as there is propellant on board, abort is armed. Correct me if I'm wrong on this point but I think this is how it goes. With Starship, abort capability would need to be accounted for after landing as well since you have to do the same thing in reverse. And since people can't or don't approach a fuelled vehicle, there will have to be some sort of solution for detanking without humans around, based on current practices. This gets tricky if it doesn't land on the chopsticks. And if Starship is designed with no abort capability but lands on a landing pad, it's even more sketchy because the crew will likely have to wait inside until the vehicle is safed. At any point during this time there is a risk of an explosion, and with no abort capability the crew is going to have a bad day if something goes wrong.

Even with a built-in flare stack, I don't think people in charge of safety ops would be very excited about crew or GSE personnel milling around a pressurized Starship venting LOX and burning methane (or venting it).

Starship and Booster vent methane all the time 10s of meters up in the air, with no special provision for burning it off.

But there aren't people hanging around when it's doing this.

[Rakrov]

If the main tanks are empty and only have 1 or 2 bar of pressure for structural stability you could vent all prop that is left in the headers  lets say 3t(10% of the fuel) into the main tank without having to vent anything outside.

[edzieba]

How about a vent that includes an igniter? It wouldn't run all the time, of course, just enough to keep the pressure under control until other methods can be hooked up. Alternate venting/burning methane with venting LOX.

In other words, a built in flare stack? I think Hopper had this, no?

Still trying to figure out what the worry is.

There are a few issues. Since this is a thread about abort capability, the issue is with crew and ground personnel. Humans don't normally approach a pressurized rocket (other than slightly pressurized to maintain structual integrity), especially not one that is pressurized with actual propellant, "red team" notwithstanding.

With F9, the crew board and get situated. The propellant load begins and the abort system is armed. Basically, as long as there is propellant on board, abort is armed. Correct me if I'm wrong on this point but I think this is how it goes. With Starship, abort capability would need to be accounted for after landing as well since you have to do the same thing in reverse. And since people can't or don't approach a fuelled vehicle, there will have to be some sort of solution for detanking without humans around, based on current practices. This gets tricky if it doesn't land on the chopsticks. And if Starship is designed with no abort capability but lands on a landing pad, it's even more sketchy because the crew will likely have to wait inside until the vehicle is safed. At any point during this time there is a risk of an explosion, and with no abort capability the crew is going to have a bad day if something goes wrong.

Even with a built-in flare stack, I don't think people in charge of safety ops would be very excited about crew or GSE personnel milling around a pressurized Starship venting LOX and burning methane (or venting it).

Starship and Booster vent methane all the time 10s of meters up in the air, with no special provision for burning it off.

But there aren't people hanging around when it's doing this.

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

[TheRadicalModerate]

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

But nobody's doing "disembark with prop still onboard after an emergency landing".

[Robotbeat]

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

But nobody's doing "disembark with prop still onboard after an emergency landing".

Everyone would do that. You don’t wait for the hypergols to be sucked out before you get out.

Orion splashed down and had ammonia boiling off still, and they waited hours for that to finish boiling off before recovering it, but in an emergency, they wouldn’t wait.

[chopsticks]

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

So what makes F9 different in this regard? Is it the load and go that is more risky? It appears that Starship will also be load and go.

[edzieba]

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

But nobody's doing "disembark with prop still onboard after an emergency landing".

They do, for the all of three cases of emergency landings that have occurred (all Soyuz). No RCS prop is dumped as part of the abort, just like all the nominal landings where RCS prop remains on-board.

Other than Falcon 9's 'load and go', all other crew launch systems (both cryogenic and hypergolic) load propellants first, then have crew and ground teams approach the active vehicle for boarding.

So what makes F9 different in this regard? Is it the load and go that is more risky? It appears that Starship will also be load and go.

F9 has to out of necessity, or it would have to give up the use of subchilled propellants. The theory behind the 'load first' COOPS is that you load propellants, let everything pressurise and settle down, and then let people approach; the idea being that the loading process itself is the riskiest part.