Author Topic: The fascinating problem of the starship landing legs  (Read 384670 times)

Offline volker2020

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Re: The fascinating problem of the starship landing legs
« Reply #1120 on: 09/29/2023 05:30 am »
Have been doing some more work on this concept to simplify and clarify. First thing I wanted to accomplish was going to an all electrical system (Tesla motors) without hydraulics. Second thing is to make the system more active to the conditions which includes; a method where the ground below each foot pad can be analyzed before touch down and the legs can be adjusted so that the vehicle lands almost perfectly level. Any residual difference being nulled out with springs. Significantly lowered the overall size of the structures which had the added benefit of keeping the legs out of the gimbal range of the Sea level raptors completely. Not an engineer so clearly there are optimizations still to be done as well as a full structures analysis.

I think they are totally over engineered. Starship Lunar Version will most like land exactly at the place they want to land or not at all. So the job of the legs is to be as cheap as possible, while doing the job of landing at a perfect spot, long analyzed before to be suiting.
If you would prepare to land on an unknown place or maybe an emergency landing somewhere on earth it might be worth to hedge against the odds of an uneven surface, but I believe that the modus operandi on moon will be either you get to the right spot or you scrap the mission.

Offline geza

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Re: The fascinating problem of the starship landing legs
« Reply #1121 on: 09/29/2023 08:11 am »
Have been doing some more work on this concept to simplify and clarify. First thing I wanted to accomplish was going to an all electrical system (Tesla motors) without hydraulics. Second thing is to make the system more active to the conditions which includes; a method where the ground below each foot pad can be analyzed before touch down and the legs can be adjusted so that the vehicle lands almost perfectly level. Any residual difference being nulled out with springs. Significantly lowered the overall size of the structures which had the added benefit of keeping the legs out of the gimbal range of the Sea level raptors completely. Not an engineer so clearly there are optimizations still to be done as well as a full structures analysis.

I think they are totally over engineered. Starship Lunar Version will most like land exactly at the place they want to land or not at all. So the job of the legs is to be as cheap as possible, while doing the job of landing at a perfect spot, long analyzed before to be suiting.
If you would prepare to land on an unknown place or maybe an emergency landing somewhere on earth it might be worth to hedge against the odds of an uneven surface, but I believe that the modus operandi on moon will be either you get to the right spot or you scrap the mission.

I like it. A crewed landing can be aborted on Moon, but not on Mars. Also, I prefer to have a possibility for emergency landing away from the launch tower here on Earth. So I am happy to see a way of leg adjusting. It can be used for post landing verticalization. Sure, one have to assess whether the extra complication and failure points worth it, or not.

Online eriblo

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Re: The fascinating problem of the starship landing legs
« Reply #1122 on: 09/29/2023 11:49 am »
Scanning the ground for each leg like that is likely unfeasible and unnecessary. You can probably get a decent idea from higher up and once closer the plumes will be busy obscuring and modifying the topography.

If you have active control over the legs you just extend them and let each retract with some small resistance until they all make contact. Then you ramp it up to get the desired braking. This compensates for the topography and any differences in surface compression without any prior knowledge.
« Last Edit: 09/29/2023 11:50 am by eriblo »

Offline Barley

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Re: The fascinating problem of the starship landing legs
« Reply #1123 on: 09/29/2023 05:03 pm »
I like it. A crewed landing can be aborted on Moon, but not on Mars. Also, I prefer to have a possibility for emergency landing away from the launch tower here on Earth. So I am happy to see a way of leg adjusting. It can be used for post landing verticalization. Sure, one have to assess whether the extra complication and failure points worth it, or not.
A good landing is one you can walk away from.
A great landing is where you can use the vehicle again.

In an emergency you should be more than happy with a good landing.
In a non-emergency you should land where you planned, on flat stable ground.


Offline Ionmars

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Re: The fascinating problem of the starship landing legs
« Reply #1124 on: 09/29/2023 05:32 pm »
Scanning the ground for each leg like that is likely unfeasible and unnecessary. You can probably get a decent idea from higher up and once closer the plumes will be busy obscuring and modifying the topography.

If you have active control over the legs you just extend them and let each retract with some small resistance until they all make contact. Then you ramp it up to get the desired braking. This compensates for the topography and any differences in surface compression without any prior knowledge.
I think this is a good approach. To amplify, the resistance setting for each leg would be M/L where M is the total mass of the vehicle on a given planet and L is the number of landing legs. Then each leg would be extended toward the surface until it detects the correct resistance setting, regardless of how far each leg is extended.

Variable leg extensions would reflect the variations in the surface under the vehicle. If variations in leg extensions cannot result in a level/vertical landing, you have a bad surface.


Offline Pheogh

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Re: The fascinating problem of the starship landing legs
« Reply #1125 on: 09/29/2023 06:35 pm »
I must be out of my mind but I have decided to embark on learning SolidWorks? in order to get this model into a form that can be sim'd. Unless someone in community is interested in partnering with me to do this work?

Offline mikelepage

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Re: The fascinating problem of the starship landing legs
« Reply #1126 on: 10/02/2023 07:33 am »
Looking at the rear elonerons on ship 25 again, they look to be about 4 meters wide, which - compared to many of the designs on this thread - would be a nice wide stance if landing legs could be attached to them. Back in the BFR days there were lots of three-legged landing leg designs that made use of the fins as load paths.

Of course there are only two elonerons now. It would be fun to split each of them in two to make an "x-wing" structure. Have an windward and leeward component to each, of which the first has all the heat shield tiles etc as we see today, and the second is literally just the shell of a flap and a second landing leg structure that flies in the leeward side of the first during EDL. Both pivot from the same midline during all flap maneuvers, and then as the swoop is finishes and the starship is vertical, they split off from each other and deploy their landing legs.

Offline lykos

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Re: The fascinating problem of the starship landing legs
« Reply #1127 on: 10/02/2023 11:29 am »
HLS has no flaps/elonerons/whatsoever
In general an old idea which was given up early
« Last Edit: 10/02/2023 11:31 am by lykos »

Offline Jimmy Murdok

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Re: The fascinating problem of the starship landing legs
« Reply #1128 on: 10/04/2023 09:21 pm »
I must be out of my mind but I have decided to embark on learning SolidWorks? in order to get this model into a form that can be sim'd. Unless someone in community is interested in partnering with me to do this work?

If you use Onshape I can help you. Much more collaborative and also my daily tool. It’s like transitioning from Word to GDocs a decade ago. Fully online and with a much more consistent workflow. You can get a free account.

Offline Nomadd

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Re: The fascinating problem of the starship landing legs
« Reply #1129 on: 10/06/2023 06:45 am »
 I imagine this has been covered, but I don't know where and have been restricted to a smartphone for 5 months and whatever other lame excuse I haven't thought of yet.

 Will they need legs for initial Ship recoveries?

 It's going to be a while before Starship is allowed to re-enter over cities, so what are the options for recovering early models? Are there orbits from the Cape that would allow them to come in over water? Legs and remote landing sites? Booster like return to launch pad flights after re-entry? How far do they fly between the re-entry burn and landing?
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline rsdavis9

Re: The fascinating problem of the starship landing legs
« Reply #1130 on: 10/06/2023 12:43 pm »
I imagine this has been covered, but I don't know where and have been restricted to a smartphone for 5 months and whatever other lame excuse I haven't thought of yet.

 Will they need legs for initial Ship recoveries?

 It's going to be a while before Starship is allowed to re-enter over cities, so what are the options for recovering early models? Are there orbits from the Cape that would allow them to come in over water? Legs and remote landing sites? Booster like return to launch pad flights after re-entry? How far do they fly between the re-entry burn and landing?

I was thinking legs for first SS(starship upper stage) landing/recovery.
But listening to IAC 2023 talk it sounded like Musk thinks that first get SS reentry and landing consistent in the water then go to catching.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline billh

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Re: The fascinating problem of the starship landing legs
« Reply #1131 on: 10/06/2023 04:53 pm »
I imagine this has been covered, but I don't know where and have been restricted to a smartphone for 5 months and whatever other lame excuse I haven't thought of yet.

 Will they need legs for initial Ship recoveries?

 It's going to be a while before Starship is allowed to re-enter over cities, so what are the options for recovering early models? Are there orbits from the Cape that would allow them to come in over water? Legs and remote landing sites? Booster like return to launch pad flights after re-entry? How far do they fly between the re-entry burn and landing?

I was thinking legs for first SS(starship upper stage) landing/recovery.
But listening to IAC 2023 talk it sounded like Musk thinks that first get SS reentry and landing consistent in the water then go to catching.
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.

Offline Barley

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Re: The fascinating problem of the starship landing legs
« Reply #1132 on: 10/06/2023 06:06 pm »
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.
If catching is hard it can be tested with suborbital launches.  It really doesn't need much beyond SN8.  The question may if they can build a cheap expendable catcher.

Offline mikelepage

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Re: The fascinating problem of the starship landing legs
« Reply #1133 on: 10/10/2023 03:33 am »
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.
If catching is hard it can be tested with suborbital launches.  It really doesn't need much beyond SN8.  The question may if they can build a cheap expendable catcher.

Maybe not even expendable. Going forward there will be advantages when it comes to point-to-point, to designing a "small" catcher towers dedicated to catching/launching Starship only. Being able to land in relatively close to cities, at sites where no superheavy will ever take off from, may make spaceports significantly more palatable to city councils/regulatory bodies, and most places in the US. are within a 1000-2000km Starship hop of Boca Chica or KSC. 

I'd always assumed point to point would be the thing that made SpaceX bite the bullet and build substantial landing legs, but maybe the only starships that have legs will be designed for significantly lower-gravity environments.

Offline Lampyridae

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Re: The fascinating problem of the starship landing legs
« Reply #1134 on: 11/16/2023 02:18 pm »
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.
If catching is hard it can be tested with suborbital launches.  It really doesn't need much beyond SN8.  The question may if they can build a cheap expendable catcher.

Maybe not even expendable. Going forward there will be advantages when it comes to point-to-point, to designing a "small" catcher towers dedicated to catching/launching Starship only. Being able to land in relatively close to cities, at sites where no superheavy will ever take off from, may make spaceports significantly more palatable to city councils/regulatory bodies, and most places in the US. are within a 1000-2000km Starship hop of Boca Chica or KSC. 

I'd always assumed point to point would be the thing that made SpaceX bite the bullet and build substantial landing legs, but maybe the only starships that have legs will be designed for significantly lower-gravity environments.

I was thinking that what makes Australia a good suborbital spaceport location is the sheer amount of terrain you could put a pad in (or crash a booster). Top up with propellant, do a short suborbital hop back to the main launch centre. Bother no-one except some kangaroos.

Offline Nevyn72

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Re: The fascinating problem of the starship landing legs
« Reply #1135 on: 11/17/2023 04:05 am »
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.
If catching is hard it can be tested with suborbital launches.  It really doesn't need much beyond SN8.  The question may if they can build a cheap expendable catcher.

Maybe not even expendable. Going forward there will be advantages when it comes to point-to-point, to designing a "small" catcher towers dedicated to catching/launching Starship only. Being able to land in relatively close to cities, at sites where no superheavy will ever take off from, may make spaceports significantly more palatable to city councils/regulatory bodies, and most places in the US. are within a 1000-2000km Starship hop of Boca Chica or KSC. 

I'd always assumed point to point would be the thing that made SpaceX bite the bullet and build substantial landing legs, but maybe the only starships that have legs will be designed for significantly lower-gravity environments.

I was thinking that what makes Australia a good suborbital spaceport location is the sheer amount of terrain you could put a pad in (or crash a booster). Top up with propellant, do a short suborbital hop back to the main launch centre. Bother no-one except some kangaroos.

You would be wrong there, we can't even put up so much as an umbrella without 3 years of planning approvals... 

Offline Lampyridae

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Re: The fascinating problem of the starship landing legs
« Reply #1136 on: 11/17/2023 08:22 am »
They will try to catch the booster first. If they are already successful at that by the time they want to land Starship back at the launch site, I suspect they will skip the legs and go straight to Mechazilla.
If catching is hard it can be tested with suborbital launches.  It really doesn't need much beyond SN8.  The question may if they can build a cheap expendable catcher.

Maybe not even expendable. Going forward there will be advantages when it comes to point-to-point, to designing a "small" catcher towers dedicated to catching/launching Starship only. Being able to land in relatively close to cities, at sites where no superheavy will ever take off from, may make spaceports significantly more palatable to city councils/regulatory bodies, and most places in the US. are within a 1000-2000km Starship hop of Boca Chica or KSC. 

I'd always assumed point to point would be the thing that made SpaceX bite the bullet and build substantial landing legs, but maybe the only starships that have legs will be designed for significantly lower-gravity environments.

I was thinking that what makes Australia a good suborbital spaceport location is the sheer amount of terrain you could put a pad in (or crash a booster). Top up with propellant, do a short suborbital hop back to the main launch centre. Bother no-one except some kangaroos.

You would be wrong there, we can't even put up so much as an umbrella without 3 years of planning approvals... 

True. They won't even be able to use the deluge system because their neighbours will dob them in for hosepipe use...

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