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how do you catch and "safe" a Starship?
by
DanClemmensen
on 16 Dec, 2023 14:27
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You can catch a SH (booster) and put it on the OLM to empty the tanks. However, the Starhip is not intended tobe set down on the OLM. Will they hold it up high enough to use the SQD arm?
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#1
by
Robotbeat
on 16 Dec, 2023 14:40
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You can catch a SH (booster) and put it on the OLM to empty the tanks. However, the Starhip is not intended tobe set down on the OLM. Will they hold it up high enough to use the SQD arm?
Catch the ship and place it on a SH, which steadies it so the SQD can attach to it.
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#2
by
sdsds
on 16 Dec, 2023 18:55
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
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#3
by
sdsds
on 16 Dec, 2023 19:05
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Overloading this thread topic a bit [note to mods: okay to delete if deemed inappropriate]:
One can imagine a somewhat smaller SH booster, sized just large enough to relaunch a Tanker ship with zero payload into a westbound trajectory from VSFB in California on a return trip to Texas or Florida. The smaller booster would have VSFB and an appropriately downsized launch tower as its home base.
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#4
by
Robotbeat
on 16 Dec, 2023 19:16
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
I don't think that's necessary. They have 2 near-flight-ready boosters right now that have already been cryo tested multiple times, B12 is largely complete, B13 is being imminently stacked (like any moment?), plus like 2 to 4 more in various stages of assembly (at least a thrust puck has been found for B18 as of 6 months ago at Starbase).
You do need to make sure to use a Booster that is compatible with the ship. Might as well be the booster it launched on.
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#5
by
jimothytones
on 21 Dec, 2023 00:10
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I'm curious if the safing aspect of this might be a non-issue. Falcon boosters landing on bare pads and downrange recovery ships don't appear to require any consumable hookups to be made approachable, and the early Ship flight test articles seemed at least intended to follow a similar strategy. Fully cryogenic propellants and autogenous pressurization certainly add an extra layer to this over kersosene fuel and helium pressurant, but I'd be surprised if there were no active work being done to make Starship vehicles ~self-safing~ (unsure if this is a real rocketry term) to the fullest extent possible. They are after all intended to ultimately land on unprepared surfaces within Earth's atmosphere, if the USAF Rocket Cargo proposal is to be seriously pursued.
How much inert gas would a Starship need to carry in order to displace residual methane (and oxygen?) and maintain internal pressure sufficient for structural stability? Can remaining methane be vented or should/can an onboard provision for flaring it be added in a safe location? Does the oxygen need to be entirely displaced, or can it be vented down to a safe pressure and maintained there if methane is fully removed?
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#6
by
Robotbeat
on 21 Dec, 2023 01:23
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Starship has about 1500t of propellant when full, about 3.7 O:F ratio, so about 320t of methane. Given the density of methane, that’s about 485, let’s call it 500 cubic meters. The ullage pressure is around 6 bar, and the density of nitrogen is about 1.2kg/m^3 at 1bar, so about 7kg/m^3, or 3.5 tonnes of nitrogen. Plus the tanks, of course. But expanding that much nitrogen will cool it off, requiring more gas for the same pressure. On the other hand, 3bar is probably enough pressure for safing, so let’s say those cancel out. Let’s call it 7 tons including tanks and plumbing. That’s for the methane tank.
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#7
by
DanClemmensen
on 21 Dec, 2023 03:02
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A Starship HLS can sit in NRHO for 100 days, or on the lunar surface for 30 or more days, or transit to Mars for a year, or sit on Mars surface for two years, or act as a Depot indefinitely. Given all this, why do we need to "safe" it immediately when it is caught on Earth? It should be able to take care of itself as we move it after we catch it.
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#8
by
chopsticks
on 21 Dec, 2023 03:20
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I'm curious if the safing aspect of this might be a non-issue. Falcon boosters landing on bare pads and downrange recovery ships don't appear to require any consumable hookups to be made approachable, and the early Ship flight test articles seemed at least intended to follow a similar strategy. Fully cryogenic propellants and autogenous pressurization certainly add an extra layer to this over kersosene fuel and helium pressurant, but I'd be surprised if there were no active work being done to make Starship vehicles ~self-safing~ (unsure if this is a real rocketry term) to the fullest extent possible. They are after all intended to ultimately land on unprepared surfaces within Earth's atmosphere, if the USAF Rocket Cargo proposal is to be seriously pursued.
How much inert gas would a Starship need to carry in order to displace residual methane (and oxygen?) and maintain internal pressure sufficient for structural stability? Can remaining methane be vented or should/can an onboard provision for flaring it be added in a safe location? Does the oxygen need to be entirely displaced, or can it be vented down to a safe pressure and maintained there if methane is fully removed?
F9 is fine because it can just vent LOX as necessary. RP1 is not cryogenic and does not need to be kept cool. Starship with methane is different though and should be safed as soon as possible because you don't want to be venting methane into the environment. (And if you don't vent it, it will explode the tank.) It's a heavy greenhouse gas (bad for the environment) and probably a bit more risky in terms of a fire/explosion hazard to vent it in atmosphere.
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#9
by
chopsticks
on 21 Dec, 2023 03:27
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A Starship HLS can sit in NRHO for 100 days, or on the lunar surface for 30 or more days, or transit to Mars for a year, or sit on Mars surface for two years, or act as a Depot indefinitely. Given all this, why do we need to "safe" it immediately when it is caught on Earth? It should be able to take care of itself as we move it after we catch it.
Because to take care of itself it has to vent methane gas which is bad.
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#10
by
DanClemmensen
on 21 Dec, 2023 03:57
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A Starship HLS can sit in NRHO for 100 days, or on the lunar surface for 30 or more days, or transit to Mars for a year, or sit on Mars surface for two years, or act as a Depot indefinitely. Given all this, why do we need to "safe" it immediately when it is caught on Earth? It should be able to take care of itself as we move it after we catch it.
Because to take care of itself it has to vent methane gas which is bad.
Why does it need to immediately vent methane? Upon landing the tank is not in thermal equilibrium and will probably experience "ullage collapse" unless heat is actively added.
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#11
by
Zed_Noir
on 21 Dec, 2023 23:31
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You can catch a SH (booster) and put it on the OLM to empty the tanks. However, the Starhip is not intended tobe set down on the OLM. Will they hold it up high enough to use the SQD arm?
Catch the ship and place it on a SH, which steadies it so the SQD can attach to it.
Simpler just to set the ship onto a travel stand on SPMT transporters. Then move the ship next to a service tower with some sort of SQD arm and maybe rotating lattice enclosure sections.
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#12
by
Robotbeat
on 22 Dec, 2023 00:08
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You can catch a SH (booster) and put it on the OLM to empty the tanks. However, the Starhip is not intended tobe set down on the OLM. Will they hold it up high enough to use the SQD arm?
Catch the ship and place it on a SH, which steadies it so the SQD can attach to it.
Simpler just to set the ship onto a travel stand on SPMT transporters. Then move the ship next to a service tower with some sort of SQD arm and maybe rotating lattice enclosure sections.
How is that simpler than just putting it right where it needs to be and a place which already has a SQD?
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#13
by
etudiant
on 22 Dec, 2023 00:35
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A Starship HLS can sit in NRHO for 100 days, or on the lunar surface for 30 or more days, or transit to Mars for a year, or sit on Mars surface for two years, or act as a Depot indefinitely. Given all this, why do we need to "safe" it immediately when it is caught on Earth? It should be able to take care of itself as we move it after we catch it.
Because to take care of itself it has to vent methane gas which is bad.
If methane must be vented, there needs to be a flaring provision. One methane explosion is quite enough for the program.
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#14
by
chopsticks
on 22 Dec, 2023 03:24
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A Starship HLS can sit in NRHO for 100 days, or on the lunar surface for 30 or more days, or transit to Mars for a year, or sit on Mars surface for two years, or act as a Depot indefinitely. Given all this, why do we need to "safe" it immediately when it is caught on Earth? It should be able to take care of itself as we move it after we catch it.
Because to take care of itself it has to vent methane gas which is bad.
Why does it need to immediately vent methane? Upon landing the tank is not in thermal equilibrium and will probably experience "ullage collapse" unless heat is actively added.
Heat from the atmosphere would be enough to cause a pressure increase sufficient that some venting or pressure management would be needed though, right? And since ullage collapse is a bad thing during the landing burn, is it guaranteed to occur everytime? IANARS but it seems a bit risky to rely on ullage collapse to prevent the need for venting to atmosphere. Lighting the methane as it's being vented like a flare stack I guess would work, but it's probably better to avoid venting it at all just due to additional fire risk. It might also get in the way of unloading people if that becomes a thing.
I think setting a landed ship on top of a booster is a possibility, but there will probably still be some amount of methane gas here and there around the ship (possibly some residual gas in the engine bay) so placing it on top of the booster right away might not be ideal. Of course it may not be an issue if there's a purge system.
I wonder if there will eventually be some kind of transport stand next to the OLM with hookups to drain the propellant. Such a stand would allow for basic hookups to pressurize the tanks during transport as well (which is done now) and would be connected to the tank farm to offload the propellant after landing. And since it is a transport stand, the ships can be transported back to the build site on the same stand for refurbishments, checkouts, and payload integration.
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#15
by
gio
on 22 Dec, 2023 04:06
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Make a land version of the drone ship
Land and choose whether to take you to the tower/bay
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#16
by
Zed_Noir
on 22 Dec, 2023 11:55
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You can catch a SH (booster) and put it on the OLM to empty the tanks. However, the Starhip is not intended to be set down on the OLM. Will they hold it up high enough to use the SQD arm?
Catch the ship and place it on a SH, which steadies it so the SQD can attach to it.
Simpler just to set the ship onto a travel stand on SPMT transporters. Then move the ship next to a service tower with some sort of SQD arm and maybe rotating lattice enclosure sections.
How is that simpler than just putting it right where it needs to be and a place which already has a SQD?
Removes the possibility of mishaps from propellant remnants coming out of the Starship and the business end of the Starship is still quite hot from the landing burn. Plus there is no need for a stand in Super Heavy of some sort on the OLM. Could be the same travel stand on SPMTs that is use for Starship stacking.
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#17
by
ulm_atms
on 22 Dec, 2023 12:29
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
So how is SS suppose to be firing its engines for a precise catch with SH sitting basically right next to it getting blasted by SS getting caught? I don't understand how there could be a SH sitting on the OLM while SS is coming in for a catch. I don't see enough room.
Now a dedicated launch and dedicated catch tower I could see working well.
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#18
by
Crispy
on 22 Dec, 2023 15:35
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
So how is SS suppose to be firing its engines for a precise catch with SH sitting basically right next to it getting blasted by SS getting caught? I don't understand how there could be a SH sitting on the OLM while SS is coming in for a catch. I don't see enough room.
Now a dedicated launch and dedicated catch tower I could see working well.
Is it any different to being blasted by SS during staging?
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#19
by
chopsticks
on 22 Dec, 2023 15:55
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
So how is SS suppose to be firing its engines for a precise catch with SH sitting basically right next to it getting blasted by SS getting caught? I don't understand how there could be a SH sitting on the OLM while SS is coming in for a catch. I don't see enough room.
Now a dedicated launch and dedicated catch tower I could see working well.
Is it any different to being blasted by SS during staging?
It's different because the plume from SS impinging on SH during hot staging hits directly on the heatshield. Burning next to a SH will likely kick up a bunch of debris that will hit the SH on the OLM.
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#20
by
Robotbeat
on 24 Dec, 2023 06:00
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As indicated in prior replies, set the Ship down on a SH booster. Eventually this could be a flight-ready booster and the Ship could refill and fly again. Nearer term, the SH used could be a sacrificial battleship test article, or other somewhat obsolete booster not intended for flight.
So how is SS suppose to be firing its engines for a precise catch with SH sitting basically right next to it getting blasted by SS getting caught? I don't understand how there could be a SH sitting on the OLM while SS is coming in for a catch. I don't see enough room.
Now a dedicated launch and dedicated catch tower I could see working well.
It hovers to the side.