Author Topic: SpaceX Chopsticks  (Read 16471 times)

Offline Hamish.Student

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SpaceX Chopsticks
« on: 10/12/2022 02:58 am »
A new thread to concentrate discussion of the chopsticks to a central location; so they don't get lost among other discussions in other threads. 
 
My first question is: How long do people think it will be until Chopstick operations are "routine" enough to no longer require pad clear for lifts?

Secondly: Will the Chopsticks ever become 100% automated? Or will they always be controlled by crew?
« Last Edit: 10/12/2022 02:58 am by Hamish.Student »

Offline Greg Hullender

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Re: SpaceX Chopsticks
« Reply #1 on: 10/12/2022 04:11 pm »
Can someone explain why this chopsticks system isn't completely insane? It seems to me that it's a super expensive construct that's apt to be destroyed if it fails to catch the booster or Starship even one time. Or is there some reason to believe it's either a) cheap and fast to replace b) robust against exploding rockets c) unlikely to ever fail?

And what are the benefits? Does it really make it that much easier to stack the stages and iterate launches? Is there some other benefit, other than eliminating landing legs? (And how big a benefit is that?)

I'm sure this has been discussed at length elsewhere, but it would seem that a thread aimed at putting all the discussion in one place ought to start with an explanation of "why chopsticks." :-)

Online matthewkantar

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Re: SpaceX Chopsticks
« Reply #2 on: 10/12/2022 04:28 pm »
I am not sure how to assess the risk, but the payoffs are huge.
-take the weight of landing gear+hard points +propellant to lift landing gear+propellant to decelerate landing gear, then add it to the boosters deltaV.
-no need for equipment to move/mount booster.
-no landing gear maintenance, no need to stow it or monitor or analyze it.
-having the launch facility stack and catch is doing things at once with the same equipment.

Offline Hamish.Student

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Re: SpaceX Chopsticks
« Reply #3 on: 10/13/2022 05:16 am »
And what are the benefits? Does it really make it that much easier to stack the stages
Yes. It removes some of the wind limits when lifting with a crane. The structure is rigid when lifted, so no humans are needed to pull on lines. When used solely for stacking stages as an alternative to a crane, it's a very ingenious idea. 
 
« Last Edit: 10/13/2022 07:19 am by Hamish.Student »

Offline Hog

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Re: SpaceX Chopsticks
« Reply #4 on: 10/13/2022 03:10 pm »
With the gaseous venting that precedes all lifts, pad clear requirements may never go away.

Paul

Offline Jim

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Re: SpaceX Chopsticks
« Reply #5 on: 10/13/2022 03:53 pm »

My first question is: How long do people think it will be until Chopstick operations are "routine" enough to no longer require pad clear for lifts?


Anyways will be a requirement.

Offline InterestedEngineer

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Re: SpaceX Chopsticks
« Reply #6 on: 10/14/2022 03:20 am »

My first question is: How long do people think it will be until Chopstick operations are "routine" enough to no longer require pad clear for lifts?


Anyways will be a requirement.

As always, your one liners are wrong.

Already wrong, in this case, as yesterday they had Starship on the chopsticks with men on lifts poking around at the QD.

Offline alugobi

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Re: SpaceX Chopsticks
« Reply #7 on: 10/14/2022 03:50 am »
Sticks were connected, but the ship was stacked, no?

Offline Nomadd

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Re: SpaceX Chopsticks
« Reply #8 on: 10/14/2022 04:14 am »
Sticks were connected, but the ship was stacked, no?
No. The sticks were holding the ship several feet above the booster while people were working on the interface.
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Offline meekGee

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Re: SpaceX Chopsticks
« Reply #9 on: 10/14/2022 04:38 am »

My first question is: How long do people think it will be until Chopstick operations are "routine" enough to no longer require pad clear for lifts?


Anyways will be a requirement.

As always, your one liners are wrong.

Already wrong, in this case, as yesterday they had Starship on the chopsticks with men on lifts poking around at the QD.
Basically even large-structure construction crane lifts, which have a much higher probability of a mishap, require at most that people not be underneath unless they have to.

This thing is 100x safer, always does the same job, and is basically a cargo elevator.

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...
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Offline geza

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Re: SpaceX Chopsticks
« Reply #10 on: 10/14/2022 04:59 am »

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...

If the booster must be pressurized for stacking, then it should remain pressurized while Starship remains stacked, shouldn't be? Does it mean that people are not supposed to walk around while stacked?

Offline lykos

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Re: SpaceX Chopsticks
« Reply #11 on: 10/14/2022 10:06 am »
Isn't it pressurized when it is transported? With all the people arround!
When pressure isn't over 1 atm and done with nonexpl. gas, where is the problem?

Offline meekGee

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Re: SpaceX Chopsticks
« Reply #12 on: 10/14/2022 01:30 pm »

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...

If the booster must be pressurized for stacking, then it should remain pressurized while Starship remains stacked, shouldn't be? Does it mean that people are not supposed to walk around while stacked?
Yes, but the lift adds the risk of dropping the ship or colliding or whatever was imagined upthread, and so a pressurized booster is more dangerous.

I still think it'll be normal operations at some point, but I also think once the booster is there and you're loading a ship, there won't be a lot of people there anyway.
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Online oldAtlas_Eguy

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Re: SpaceX Chopsticks
« Reply #13 on: 10/14/2022 05:24 pm »

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...

If the booster must be pressurized for stacking, then it should remain pressurized while Starship remains stacked, shouldn't be? Does it mean that people are not supposed to walk around while stacked?
Yes, but the lift adds the risk of dropping the ship or colliding or whatever was imagined upthread, and so a pressurized booster is more dangerous.

I still think it'll be normal operations at some point, but I also think once the booster is there and you're loading a ship, there won't be a lot of people there anyway.
A positive pressure of a non explosive gas such as nitrogen is a safety factor for humans around it than a danger. So long as the positive pressure amount gains the needed structural integrity without increasing risk of structural failure creating a lowering risk of danger from a structural failure. Having that pressure can give the humans around the area that added extra time to get away from the vehicle as it does a slow collapse vs a faster one. The Atlas always had a positive pressure and humans crawled around around it all the time including non-worker visitors that walked up to and put their hands on the vehicle skin. It is as Nomad mentioned the movement of the vehicle that is a clear the area event and was so for the old Atlas as well except the horizontal road travel which was in a special hard frame but uncovered. Sort of like the vertical road transport of the SH or SS that just needs to make sure that the area around is clear (or mostly clear-restricted access) if it topples over. It is not going to explode just toss some pieces a few meter out from where it impacts mostly due to the fall and less about the pressurization.

Online DanClemmensen

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Re: SpaceX Chopsticks
« Reply #14 on: 10/14/2022 05:41 pm »
Sort of like the vertical road transport of the SH or SS that just needs to make sure that the area around is clear (or mostly clear-restricted access) if it topples over. It is not going to explode just toss some pieces a few meter out from where it impacts mostly due to the fall and less about the pressurization.
It's a question of scale. An SH is 234 feet tall. Depending on your conversion factor, that's about as tall as a 20-story building. If it topples it can hit you if you are within 234 feet of it even if it's sitting on the ground and does not throw any debris. In contrast with a building, it will topple as a unit, especially if a bit of pressure helps it retain its structural integrity.

Online oldAtlas_Eguy

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Re: SpaceX Chopsticks
« Reply #15 on: 10/14/2022 06:17 pm »
Sort of like the vertical road transport of the SH or SS that just needs to make sure that the area around is clear (or mostly clear-restricted access) if it topples over. It is not going to explode just toss some pieces a few meter out from where it impacts mostly due to the fall and less about the pressurization.
It's a question of scale. An SH is 234 feet tall. Depending on your conversion factor, that's about as tall as a 20-story building. If it topples it can hit you if you are within 234 feet of it even if it's sitting on the ground and does not throw any debris. In contrast with a building, it will topple as a unit, especially if a bit of pressure helps it retain its structural integrity.
Safety risks analysis is always case driven. For each case there may be a different pressure range that optimizes safety. Remember that unpressurized the risks are deemed higher because SpaceX attaches a crane to the top to put the vehicle in "stretch" to increase the structural integrity and general safety level. Else humans are not allowed to work around the vehicle and especially inside the tank. At some point during the stacking of the vehicle the optimal pressure for safety goes above ambient. Which requires some method to get the safety levels to be around the vehicle during its construction up to minimum required safety levels. Usually done by a overhead crane attachment at the top.

Road trip has many additional risks above just structural failure: topples due to balance capability failure of the transport. due to unexpected wind gust, unexpected road condition, unexpected oscillations. The general note here is that increased structural strength can provide extra mitigation of topple due to requiring the topple to lift the mass of the conveyance off the ground vs collapsing the vehicle at just above the thrust structure.

Offline meekGee

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Re: SpaceX Chopsticks
« Reply #16 on: 10/14/2022 06:43 pm »

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...

If the booster must be pressurized for stacking, then it should remain pressurized while Starship remains stacked, shouldn't be? Does it mean that people are not supposed to walk around while stacked?
Yes, but the lift adds the risk of dropping the ship or colliding or whatever was imagined upthread, and so a pressurized booster is more dangerous.

I still think it'll be normal operations at some point, but I also think once the booster is there and you're loading a ship, there won't be a lot of people there anyway.
A positive pressure of a non explosive gas such as nitrogen is a safety factor for humans around it than a danger. So long as the positive pressure amount gains the needed structural integrity without increasing risk of structural failure creating a lowering risk of danger from a structural failure. Having that pressure can give the humans around the area that added extra time to get away from the vehicle as it does a slow collapse vs a faster one. The Atlas always had a positive pressure and humans crawled around around it all the time including non-worker visitors that walked up to and put their hands on the vehicle skin. It is as Nomad mentioned the movement of the vehicle that is a clear the area event and was so for the old Atlas as well except the horizontal road travel which was in a special hard frame but uncovered. Sort of like the vertical road transport of the SH or SS that just needs to make sure that the area around is clear (or mostly clear-restricted access) if it topples over. It is not going to explode just toss some pieces a few meter out from where it impacts mostly due to the fall and less about the pressurization.
I have no problem with people next to a pressure tank, for all the reasons you stated.

I have no problem with the safety of the chopsticks - they will be much safer than any crane op.

I only added that during motion, when there's some non-zero chance of Starship hitting SH, then the stored energy in SH can add risk, if the skin is punctured.

Overall though, I'm fully with those thinking that Chipstick lifts will not require a "pad clear".
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Online oldAtlas_Eguy

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Re: SpaceX Chopsticks
« Reply #17 on: 10/14/2022 06:52 pm »

The only issue I see is that the booster is pressurized when the ship is lifted, but this again probably just means don't hang around the pad for no reason...

If the booster must be pressurized for stacking, then it should remain pressurized while Starship remains stacked, shouldn't be? Does it mean that people are not supposed to walk around while stacked?
Yes, but the lift adds the risk of dropping the ship or colliding or whatever was imagined upthread, and so a pressurized booster is more dangerous.

I still think it'll be normal operations at some point, but I also think once the booster is there and you're loading a ship, there won't be a lot of people there anyway.
A positive pressure of a non explosive gas such as nitrogen is a safety factor for humans around it than a danger. So long as the positive pressure amount gains the needed structural integrity without increasing risk of structural failure creating a lowering risk of danger from a structural failure. Having that pressure can give the humans around the area that added extra time to get away from the vehicle as it does a slow collapse vs a faster one. The Atlas always had a positive pressure and humans crawled around around it all the time including non-worker visitors that walked up to and put their hands on the vehicle skin. It is as Nomad mentioned the movement of the vehicle that is a clear the area event and was so for the old Atlas as well except the horizontal road travel which was in a special hard frame but uncovered. Sort of like the vertical road transport of the SH or SS that just needs to make sure that the area around is clear (or mostly clear-restricted access) if it topples over. It is not going to explode just toss some pieces a few meter out from where it impacts mostly due to the fall and less about the pressurization.
I have no problem with people next to a pressure tank, for all the reasons you stated.

I have no problem with the safety of the chopsticks - they will be much safer than any crane op.

I only added that during motion, when there's some non-zero chance of Starship hitting SH, then the stored energy in SH can add risk, if the skin is punctured.

Overall though, I'm fully with those thinking that Chipstick lifts will not require a "pad clear".
Thanks for your position clarification. So we are in agreement. Good engineering and risk assessments generally make a safer work environment. The right amount of extra pressure above ambient+use of a hard structure Chopsticks vs a soft structure crane results in a situation that is safe enough for personnel performing general work around the vehicle as long as no vehicle movement is in process.
« Last Edit: 10/14/2022 06:53 pm by oldAtlas_Eguy »

Offline Jim

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Re: SpaceX Chopsticks
« Reply #18 on: 10/15/2022 03:21 pm »

As always, your one liners are wrong.

Already wrong, in this case, as yesterday they had Starship on the chopsticks with men on lifts poking around at the QD.

Wrong again on both points as usually.   "Pad clear" doesn't mean all personnel.   It means all non essential personnel. 
That is basic work knowledge.  It applies to spacecraft fueling, lifts of fueled spacecraft, lifts of large hardware, etc.  BDA clears are usually when going into launch vehicle people propellant loading and that clears all personnel.
« Last Edit: 10/15/2022 03:29 pm by Jim »

Offline Alvian@IDN

Re: SpaceX Chopsticks
« Reply #19 on: 10/15/2022 03:44 pm »

As always, your one liners are wrong.

Already wrong, in this case, as yesterday they had Starship on the chopsticks with men on lifts poking around at the QD.

Wrong again on both points as usually.   "Pad clear" doesn't mean all personnel.   It means all non essential personnel. 
That is basic work knowledge.  It applies to spacecraft fueling, lifts of fueled spacecraft, lifts of large hardware, etc.  BDA clears are usually when going into launch vehicle people propellant loading and that clears all personnel.
Well the pad is cleared even for SpaceX employees as well when the chopsticks is lifting. No humans seen anywhere

And the vehicle lifting by crane even like B4 & S20's first full stack (which is categorized as "lifts of large hardware" in your words) does not do the same pad clearing, hence other posters question of whether it will be required indefinitely
« Last Edit: 10/15/2022 03:47 pm by Alvian@IDN »
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