Abort options for Starship and Starship/SuperHeavy

[Robotbeat]

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.)

[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.

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.

[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.

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.

[InterestedEngineer]

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.

[Robotbeat]

Or just flare it off.

[DanClemmensen]

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.

[Robotbeat]

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.

[chopsticks]

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).

[Robotbeat]

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.)

[InterestedEngineer]

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.

[Anguy]

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.

[Robotbeat]

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.