Author Topic: Abort options for Starship and Starship/SuperHeavy  (Read 251992 times)

Offline Robotbeat

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #600 on: 12/14/2022 09:58 pm »
There are conceivable ways to do this with crewed Starship by topping up subchilled propellants in a recirculating loop. Or they just allow the propellant to warm up during the hour or whatever it takes for the crew to get settled. Once in orbit, the depot can dispense subchilled propellants. (They can be subchilled by just reducing the ullage pressure… potentially all the way to vacuum… or they can active cooling.)
« Last Edit: 12/14/2022 10:07 pm by Robotbeat »
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Offline chopsticks

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #601 on: 12/14/2022 10:10 pm »
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".

Or even "after a nominal landing", assuming landing legs are used for crewed flights.

The only solution I can think of is having the vehicle "self-safe" somehow, but I don't know what silver bullet would be.

Some thoughts:

Would a small amount (how much and how much would it weight?) of insulation on the inside of the tanks work for this? To allow for say a few hours of hold time without venting and not too much of an increase in tank pressure?

Potential ops (assuming no pad abort capability) :

SS lands > Vents close > Crew disembarks > Crew leaves area > GSE equipment (truck or something) approaches and drains residual prop.

This scenario would require insulation or some way of preventing boiloff for some time. The self-safing capability (however it works) is crucial here, otherwise you could end up with a scenario where you are stuck inside with increasing tank pressure and a limited time to evacuate using a inflatable slide or such.

No abort capability here still seems to be more dangerous than before launch when the fuel/drain lines are all still hooked up and everything has been green-lit for crew and personnel access.

If pad abort is an option, you could maybe get away with not having extra insulation, but the vehicle would still need to be externally safed somehow.

Even a chopsticks landing would be a bit weird. Would the SS just be suspended in midair and the QD arm connect to it like that? Up until this point, being able to pad abort would be a nice-to-have.

Offline chopsticks

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #602 on: 12/14/2022 10:15 pm »
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.

The difference here though is that RCS prop isn't cryogenic and doesn't want to expand like crazy. That's the issue with Starship.

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.

Thanks, that makes sense.

Offline InterestedEngineer

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #603 on: 12/14/2022 10:43 pm »
Let's do a little math on methane venting.

Assuming the Starship is floating horizontally after an abort.

Assume a 3m/sec wind.

assume the vent distance is 9m, with an average width of 3m.

That's 27x3x3 = 243 cubic meters of fresh air per second over that vent area.

The maximum allowable methane concentration before ignition can occur is 5%.

243*.05 = 12 cubic meters of gaseous methane vented per second. 

12 cubic meters of gaseus methane weighs in at 8kg.

1 hour is 30t of methane.  That's more methane than should remain in main and header tanks.

The above is a very pessimistic calculation.   I suspect all the remaining methane can be vented in 15 minutes safely, especially if there's more than one vent along the length of the Starship.

Contrast this to 1 second of 33 engines methane output underneath the OLM.  About 1 second at a flow rate of 100kg/sec for each engine.  There was no wind.

33 * 100kg = 3300kg of methane or 5000 cubic meters of gaseous methane. underneath the OLM which is about 1000 cubic meters.  No wonder it went boom.

TL;DR - the worry about venting the excess methane is a non-problem on a water landing where all heat sources are snuffed out and the vent rate keeps the concentration below ignition point.

Offline Robotbeat

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #604 on: 12/15/2022 12:09 am »
Or just flare it off.
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Online DanClemmensen

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #605 on: 12/15/2022 12:27 am »
Or just flare it off.
Yep. A flare generates its own wind, so the flame is not directly touching the material of the orifice. The entrained air blows the flame away from the orifice.

Offline Robotbeat

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #606 on: 12/15/2022 12:41 am »
Or just flare it off.
Yep. A flare generates its own wind, so the flame is not directly touching the material of the orifice. The entrained air blows the flame away from the orifice.
And it can be a tube.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline chopsticks

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #607 on: 12/15/2022 03:16 am »
Let's do a little math on methane venting.

Assuming the Starship is floating horizontally after an abort.

Assume a 3m/sec wind.

assume the vent distance is 9m, with an average width of 3m.

That's 27x3x3 = 243 cubic meters of fresh air per second over that vent area.

The maximum allowable methane concentration before ignition can occur is 5%.

243*.05 = 12 cubic meters of gaseous methane vented per second. 

12 cubic meters of gaseus methane weighs in at 8kg.

1 hour is 30t of methane.  That's more methane than should remain in main and header tanks.

The above is a very pessimistic calculation.   I suspect all the remaining methane can be vented in 15 minutes safely, especially if there's more than one vent along the length of the Starship.

Contrast this to 1 second of 33 engines methane output underneath the OLM.  About 1 second at a flow rate of 100kg/sec for each engine.  There was no wind.

33 * 100kg = 3300kg of methane or 5000 cubic meters of gaseous methane. underneath the OLM which is about 1000 cubic meters.  No wonder it went boom.

TL;DR - the worry about venting the excess methane is a non-problem on a water landing where all heat sources are snuffed out and the vent rate keeps the concentration below ignition point.

I'm not referring to water landings or even necessarily emergency landings. Just regular landings and the safety concerns surrounding them, and why you'll probably want pad abort capability. Why did it take crews hours to approach SN15 after it landed?

It's not just the venting of methane, it's the combination of that possibility and the fact that the vehicle remains pressurized (with propellant).

Offline Robotbeat

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #608 on: 12/15/2022 03:38 am »
It took hours for crew to recover Artemis I's Orion, too, because they were waiting for ammonia to boil off. (Ammonia is also explosive... and otherwise hazardous as well.)
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Offline InterestedEngineer

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #609 on: 12/15/2022 04:56 am »

I'm not referring to water landings or even necessarily emergency landings. Just regular landings and the safety concerns surrounding them, and why you'll probably want pad abort capability. Why did it take crews hours to approach SN15 after it landed?

It's not just the venting of methane, it's the combination of that possibility and the fact that the vehicle remains pressurized (with propellant).

Regular landings - attach QDR, drain and replace nitrogen.  Don't even need to 100% replace.

Non-optimal chopstick landings where the QDR doesn't fit for some reason -  Vent into wind just like on water.  They are very high, tons of volume of fresh air to dilute into.

Why did it take hours to approach SN15?  Any number of reasons.  Unsure about tank integrity   The days before they decided to use vents as RCS, thus having lower venting volumes.   Draining methalox out of the old Raptor-1s w/ no purge capability.   Probably others I haven't thought of.
« Last Edit: 12/15/2022 04:57 am by InterestedEngineer »

Offline Anguy

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #610 on: 03/01/2023 05:32 pm »
I did not read whole thread, but I think the best option is proven capsule with parachute and ablative heat shield. But while some proposed to put it inside the ship, I would let it ride on top of the ship. Dragon trunk can be attached to ring situated on the surface around the conical section just above the fins, with the tip of the ship hidden inside the trunk. When on orbit Dragon would detach and dock to the side of the SS or wherever the hatch will be and the crew will transfer inside. For descent humans would ALWAYS use capsule, SS lands automatically.

The advantages are the ability to use abort during whole ascent, even from orbit, relatively little new development, (all you actually need is redesigned Starship nose able to carry the Dragon and survive reentry), can be used on vanilla Starships with headers in the nose even on cargo versions. (for example to resupply space station ship can carry Dragon on top and cargo modules in payload bay).

Of course it is limited to 4-7 people currently, maybe up to 12 if bigger capsule is developed, but that's enough for typical exploration/servicing missions.


Offline Robotbeat

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #611 on: 03/01/2023 07:51 pm »
Too expensive to be used regularly so it’ll never be any safer than current systems. Starship may become cheap enough that it can be used hundreds or thousands of times more frequently than current systems, which overcomes the safety advantage of a separate abort system. It’d be safer while being orders of magnitude cheaper.
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Offline InterestedEngineer

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #612 on: 04/20/2023 09:23 pm »
With proper software, an early BECO and separation would allow Starship to abort to a suborbital flight and land downrange on a prepared tower or pad (e.g. Florida).

in fact w/o cargo abort-to-orbit would have been possible today (mass ratio of 11).   So another abort "option" is excess fuel on Starship allowing abort-to-orbit.

This would allow aborts on excessive Booster engine outs and other damage such as to the steering system.

But it's far too early to program such scenarios.  So today we got the automated FTS instead.
« Last Edit: 04/20/2023 09:24 pm by InterestedEngineer »

Offline Asteroza

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #613 on: 04/21/2023 01:11 am »
With proper software, an early BECO and separation would allow Starship to abort to a suborbital flight and land downrange on a prepared tower or pad (e.g. Florida).

in fact w/o cargo abort-to-orbit would have been possible today (mass ratio of 11).   So another abort "option" is excess fuel on Starship allowing abort-to-orbit.

This would allow aborts on excessive Booster engine outs and other damage such as to the steering system.

But it's far too early to program such scenarios.  So today we got the automated FTS instead.

If the SH is having trouble though, you won't get the twist throw of a normal separation though, so escape separation will be very soviet style with the Starship raptors lighting up while still contained within the interstage area. Hope the larger panel area between grid fins can blow out...

Offline InterestedEngineer

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #614 on: 04/21/2023 01:33 am »
With proper software, an early BECO and separation would allow Starship to abort to a suborbital flight and land downrange on a prepared tower or pad (e.g. Florida).

in fact w/o cargo abort-to-orbit would have been possible today (mass ratio of 11).   So another abort "option" is excess fuel on Starship allowing abort-to-orbit.

This would allow aborts on excessive Booster engine outs and other damage such as to the steering system.

But it's far too early to program such scenarios.  So today we got the automated FTS instead.

If the SH is having trouble though, you won't get the twist throw of a normal separation though, so escape separation will be very soviet style with the Starship raptors lighting up while still contained within the interstage area. Hope the larger panel area between grid fins can blow out...

Cutting out the engines one one side would cause a rotation.

The stability is fragile enough that it's not too hard to cause a rotation.

Offline Jim

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #615 on: 04/21/2023 01:52 am »
With proper software, an early BECO and separation would allow Starship to abort to a suborbital flight and land downrange on a prepared tower or pad (e.g. Florida).

in fact w/o cargo abort-to-orbit would have been possible today (mass ratio of 11).   So another abort "option" is excess fuel on Starship allowing abort-to-orbit.

This would allow aborts on excessive Booster engine outs and other damage such as to the steering system.

But it's far too early to program such scenarios.  So today we got the automated FTS instead.

No.  Doesn’t work for Florida launches. No down range land mass.  Can’t say abort to abort was feasible.  The stage was already under performing

Offline sanman

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #616 on: 04/21/2023 04:17 am »
No.  Doesn’t work for Florida launches. No down range land mass.  Can’t say abort to abort was feasible.  The stage was already under performing

Jim is it feasible for flight computers to shut off engines diametrically opposite to ones that flamed out, in order to increase thrust symmetry and control authority? Would that have been useful in today's flight test?

Offline Lars-J

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #617 on: 04/21/2023 04:30 am »
No.  Doesn’t work for Florida launches. No down range land mass.  Can’t say abort to abort was feasible.  The stage was already under performing

Jim is it feasible for flight computers to shut off engines diametrically opposite to ones that flamed out, in order to increase thrust symmetry and control authority? Would that have been useful in today's flight test?

Certainly, that was the N-1 method of compensating. But then you double your thrust loss making a bad day even worse. 3 engines alone might be survivable in an abort-to-orbit scenario. Forcing another 3 engines to turn off would not be, they have margin but not that much margin.

Offline sebk

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #618 on: 04/21/2023 08:45 am »
With proper software, an early BECO and separation would allow Starship to abort to a suborbital flight and land downrange on a prepared tower or pad (e.g. Florida).

in fact w/o cargo abort-to-orbit would have been possible today (mass ratio of 11).   So another abort "option" is excess fuel on Starship allowing abort-to-orbit.

This would allow aborts on excessive Booster engine outs and other damage such as to the steering system.

But it's far too early to program such scenarios.  So today we got the automated FTS instead.

No.  Doesn’t work for Florida launches. No down range land mass.  Can’t say abort to abort was feasible.  The stage was already under performing

Well, the upper stage is supposed to have about 6.4km/s dV. It should be enough to RLTS from any point in booster flight (BECO is about 1.5 to 2.0km/s downrange velocity. So 2km/s to cancel it out which leaves 4.4km/s for return from ~2x the BECO downrange but well above sea level vertically (likely well into space in fact) -- this should be enough, with performance to spare.

Of course only works if the upper stage is still all-right.

Offline Garrett

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Re: Abort options for Starship and Starship/SuperHeavy
« Reply #619 on: 05/05/2023 02:40 pm »
Bringing this discussion over from the SS first flight discussion thread:
AFTS is still necessary for a crewed vehicle. Shuttle flew with an FTS system, initially for both the SRBs and ET, later just for the SRBs after the decision was made to remove charges from the ET rather than to implement a selective destruct system that would allow firing of the ET charges to be inhibited (after removal, aborts after SRB separation would be via comms to terminate the SSME thrust, or in case of comms failure the FTS command from the range would illuminate a RANGE SAFETY indicator for the crew to manually terminate SSME thrust. Loss of control by the crew would leave no FTS options). Termination of the SRBs (or the ET when charges were present) would have as a near-certainly mean loss of crew.
Just because Starship may be flying 1000 tonnes of propellant with people on top, does not mean that is is not still flaying 1000 tonnes of propellant. Keeping that big explosive tank away from population centres must trump the lives of any crew on board. FTS would be only one of the many risks accepted by any spaceflight participants.

Dragon flights has AFTS on booster, 2nd stage. Yes?
Is there AFTS on dragon? I don't think so. It does have a load of hypergolic fuel but probably is not a huge risk to population on the ground.

Obviously with super heavy and starship we have combined 2nd stage with dragon so it is different.


Dragon is a ballistic load during all the launch phases. It does not ignite any engines until well after orbit insertion.
SS is the second stage to orbit, so once it lights its engines (in a nominal or off-nominal event), they need a reliable way to shut them down.
During an abort scenario, I would imagine the SS would be full of fuel and too heavy to land, right? There would then be no option but to dump fuel before an emergency landing (in the ocean?). Maybe this fuel dump could replace the AFTS, as it would disable the possibility of SS reaching a populated area under engine power? Then the much smaller header tanks would be used for the emergency landing.
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