Catching Starship's upper stage

[catdlr]

Oh God, here we go again.

Let's see how many forms of landing has been discussed so far...

Hear, hear!

Plus Musk already announced they would attempt to catch the upper stage on IFT-8, if IFT-7 goes well (link here).

So why would we continue to discuss other options when when we know they plan to catch the upper stage?

Dave, good afternoon; it started here.

https://forum.nasaspaceflight.com/index.php?topic=61662.msg2644171#msg2644171

[Dave G]

Dave, good afternoon; it started here.

https://forum.nasaspaceflight.com/index.php?topic=61662.msg2644171#msg2644171

Yes, I read that post.

But 5 days ago, Musk said "SpaceX will attempt to catch the ship with the tower" on IFT-8 (link here).

For me, it seems somewhat pointless to discuss landing options when we know SpaceX plans to catch the ship.

[catdlr]

Dave, good afternoon; it started here.

https://forum.nasaspaceflight.com/index.php?topic=61662.msg2644171#msg2644171

Yes, I read that post.

But 5 days ago, Musk said "SpaceX will attempt to catch the ship with the tower" on IFT-8 (link here).

For me, it seems somewhat pointless to discuss landing options when we know SpaceX plans to catch the ship.

Dave, I tried some fun to quiet our energetic minds. Back to chopstick catching, soon to be an Olympic event.

[wannamoonbase]

Oh my, didn't I poke the bear.

I was just suggesting that if they are precise enough to catch a ship in mid air, they are precise enough to land over an open circle.

Also, the base of the ship is strong enough to handle the mating of the full stack, so it could handle the load of landing.  Serving a single 9 meter diameter foot pad.  (Best part is no part and using what you already have on the vehicle)

I know they are going for the chopsticks, I think they'll do it too.  How many attempts, changes and additions to the ship need to be made, we shall see.

SpaceX has thousands of staff churning out ideas, they know what they are doing (most times)

[catdlr]

Oh my, didn't I poke the bear.

I was just suggesting that if they are precise enough to catch a ship in mid air, they are precise enough to land over an open circle.

Also, the base of the ship is strong enough to handle the mating of the full stack, so it could handle the load of landing.  Serving a single 9 meter diameter foot pad.  (Best part is no part and using what you already have on the vehicle)

I know they are going for the chopsticks, I think they'll do it too.  How many attempts, changes and additions to the ship need to be made, we shall see.

SpaceX has thousands of staff churning out ideas, they know what they are doing (most times)

I agree wannamoonbase. 

Indeed, we have yet to see a designer. You would think that Ship 26, which just yesterday met its fate, could have been used as a demo ship to test a design on the pad. But no. 
Our prying eyes keep scanning for a clue somewhere, somehow.

Tony

[Eka]

Oh my, didn't I poke the bear.

I was just suggesting that if they are precise enough to catch a ship in mid air, they are precise enough to land over an open circle.

Also, the base of the ship is strong enough to handle the mating of the full stack, so it could handle the load of landing.  Serving a single 9 meter diameter foot pad.  (Best part is no part and using what you already have on the vehicle)

I know they are going for the chopsticks, I think they'll do it too.  How many attempts, changes and additions to the ship need to be made, we shall see.

SpaceX has thousands of staff churning out ideas, they know what they are doing (most times)

I agree wannamoonbase. 

Indeed, we have yet to see a designer. You would think that Ship 26, which just yesterday met its fate, could have been used as a demo ship to test a design on the pad. But no. 
Our prying eyes keep scanning for a clue somewhere, somehow.

Tony

Well, what if the hole has a non rigid mounted grid....

I was writing this up as a reply to another post a few days ago, and took it to a document.

Abort to landing on the skirt idea sounds fine to me.
https://x.com/elonmusk/status/1379876450744995843

Could even be the norm if the landing area was designed right. Have a spring loaded and dampened grid of deluge cooled slats the ship lands on. The exhaust goes between the slats into a flame trench. The whole grid needs to move and be stabilized as a unit, and tilted to meet the skirt. This is due to the very low clearance to the engine bells, and rigidity of the skirt. To make it more palatable structure wise have the aft end of the skirt have 6 equally spaced areas that are lower than the rest of the skirt edge, replaceable, well braced to take the load when landing. They need to be long enough in circumference to sit on at least 2 of the slats in both directions when diagonal. Greater length allows more places to use a toe "jack" to lift the Starship. Plus these leg stubs keep the engine bells further off the ground. They would provide a very good load path for launch loads so the in between areas can be opened up more for exhaust escape during hot staging. In a real pinch, the ship could then more easily land on any flat cement pad, spalling expected.

I was planning on the hole with grid in it would be 2X to 3X diameter of Starship. The issue is the larger it is, the further the edges must move up and down to adjust to the landing Starship.

Negatives would be increased strength and bracing needed in the skirt to handle landing loads. I expect they may be higher than the loads during launch. Well, maybe. The weight of a Starship fully loaded with fuel and payload is easily over 2X the return weight of a fuel spent Starship with full payload coming in for landing.

On an off shore space port. Similar grid landing pads could be used, but be on an arm that extends out over the ocean. On my pre catch offshore platform design I used similar but fixed grid landing pads on the arms. In a later design they retracted into a detanking bay. From there the ship would be moved into the central hangar for processing. The platform would have many more detanking bays than launch pads so if a Starship or booster needs work to detank properly it can be worked on in a detanking bay out of the elements, protected from other launch and landing operations, and not pollute the main hangar with propellants.

On Mars, similar grid landing pads could be made, but use liquid carbon dioxide for cooling. The first few could be shipped to Mars. The rest made from steel made from mined iron, etc.

A transporter could be designed to drive out on the slats, and pick up a Starship by it's bottom lip in the areas between the slats. It then can deliver the Starship to detanking, and integration facilities.

It needs more flushing out, and is a bit off topic for this thread.

[Dave G]

https://twitter.com/mcrs987/status/1860147910979301491

TheSpaceEngineer
@mcrs987
You can't really do that with an actuator in the middle there. Maybe I'm mistaken but you absolutely cannot just do it booster style. Extremely crude drawing but it gets the point across

A hinge requires a slot opening.

Why not a simple push-out, moving inside a load bearing sleeve, and the sleeve connects to the body the same way the current pin does?

The pin doesn't have to have exactly the shape they use right now.

Yes, push-out pins could work.

I suspect some previous posters suggesting flip-out catch pins may have assumed they would internally anchor to the stringers in the ship's side, rather than attaching to the dome like the booster.

[Dave G]

Our prying eyes keep scanning for a clue somewhere, somehow.

The render below (previously posted by StraumliBlight) seems like a clue, especially since they removed the TPS tiles in this exact area on the last test flight (IFT-6).

You would think that Ship 26, which just yesterday met its fate, could have been used as a demo ship to test a design on the pad. But no. 

The render seems to show ship v2.  If I remember correctly, the internal v2 domes are much higher than v1. So if the catch pins are internally connected to the top dome, is it possible the first catch attempt will use a v2 ship ?

[meekGee]

https://twitter.com/mcrs987/status/1860147910979301491

TheSpaceEngineer
@mcrs987
You can't really do that with an actuator in the middle there. Maybe I'm mistaken but you absolutely cannot just do it booster style. Extremely crude drawing but it gets the point across

A hinge requires a slot opening.

Why not a simple push-out, moving inside a load bearing sleeve, and the sleeve connects to the body the same way the current pin does?

The pin doesn't have to have exactly the shape they use right now.

Yes, push-out pins could work.

I suspect some previous posters suggesting flip-out catch pins may have assumed they would internally anchor to the stringers in the ship's side, rather than attaching to the dome like the booster.

Whichever way, there has to be some local distribution structure, some spars or what not.

I'm saying that this structure would connect the outer sleeve/bushing to the ship.

Meanwhile, however, I've been considering failure modes.  On the one hand, a solid pin is a monster and is very difficult to damage.  On the other hand, any damage would create difficulty in sliding the pin through the bushing.  On the gripping hand, it's very difficult to damage the pin while it's inside the bushing. If it went in, it'll also gonma come out. Most likely.

It's not the lightest of solutions, but overall it may not be too heavy and simplicity does count.

Clearly they'll pop it out and back in a few times before launch.

[rsdavis9]

You can also flip sideways instead of up and down. Sideways you don't have the large torque on the hinge pins.

[dondar]

https://twitter.com/mcrs987/status/1860147910979301491

TheSpaceEngineer
@mcrs987
You can't really do that with an actuator in the middle there. Maybe I'm mistaken but you absolutely cannot just do it booster style. Extremely crude drawing but it gets the point across

strange drawing. It is illogical to make hinge mechanism in such way even for much smaller vehicles. Hinges are horrible load absorbers.

 Just make free loaded full size rotating pin, which is restricted when erected by the reinforced ship skin (to take most of the load). If to introduce lock pins for erected position, the hinge mechanism has to support only weight of the pin. Or one can make cup formed reinforced structure around hinge (see Soyuz stage separation mechanism for working example) to restrict movement and absorb rest of the load forces.

[Dave G]

https://twitter.com/mcrs987/status/1860147910979301491

strange drawing. It is illogical to make hinge mechanism in such way even for much smaller vehicles. Hinges are horrible load absorbers...

I suspect the one on the left, labeled "rigid (booster style)" doesn't have any moving hinges, and uses a rigid internal connection to the dome plus connects with the stringers/hoops of the outer skin for added strength.

For catching the ship, if the landing pins stick out like the ones the booster, then the ship pins may melt during reentry.

The attached render below (previously posted here) seems to show some type of door right where we'd expect a catch pin to be. The render shows TPS tiles over this area, but the last test flight (IFT-6) removed the tiles right in this area and below it.

So assuming these (obviously uncertain) clues are pointing us in the right direction, if we follow that path, the question is: How will the pin move out from behind the door?  Will it swing out vertically? Horizontally? Or will it push out?

Over on X, someone posted a GIF showing how the ship catch pin might swing out vertically (link here, also attached), and that prompted some questions about load bearing over there.

[spacenut]

SpaceX will probably make catching work.  However, I do like the idea of landing on a milk stool grid pad using the bottom skirt.  They are going to have to put landing legs on the Mars ships as well as the lunar ships putting stress on the bottom anyway, so why not just land.  A grid pad does allow some lateral slack on landing.  More so than two catch pins.  Also, if human rated, it seems to me to be a safer alternative.  The milk stool grid landing pad could be right next to the launch pad for re-stacking. 

[Dave G]

link here

[JamesH65]

So assuming these (obviously uncertain) clues are pointing us in the right direction, if we follow that path, the question is: How will the pin move out from behind the door?  Will it swing out vertically? Horizontally? Or will it push out?

I think Push. Easy enough to have a rack/pinion to extend the pin, and easier than hinges to make strong enough. Also a smaller opening to protect with a heat shield.

[Nescio Erucis]

So assuming these (obviously uncertain) clues are pointing us in the right direction, if we follow that path, the question is: How will the pin move out from behind the door?  Will it swing out vertically? Horizontally? Or will it push out?

I think Push. Easy enough to have a rack/pinion to extend the pin, and easier than hinges to make strong enough. Also a smaller opening to protect with a heat shield.

I wonder, would it be possible that the pin is threaded and simply spins in order to retract/emerge? I'm trying to think of the most failure-proof mode of pushing out the pin.

[RobLynn]

If they're intending to do one more ocean landing of starship Spacex could set up a platform with an oversized meat-hook and skewer starship with lateral translation into the hook penetrating the cargo bay at landing to keep the engines and heat shield out of the water for detailed post flight inspection.

A large array of compliant curved vacuum pads say 4 x 10m tall to suck onto non-shielded side of tank section would also be an option requiring no additional hardware on starship.  Silicone rubber skirt to such a vacuum pad can handle short period of 2-300°C.

[xvel]

that's not how physics works

[dondar]

https://twitter.com/mcrs987/status/1860147910979301491

strange drawing. It is illogical to make hinge mechanism in such way even for much smaller vehicles. Hinges are horrible load absorbers...

I suspect the one on the left, labeled "rigid (booster style)" doesn't have any moving hinges, and uses a rigid internal connection to the dome plus connects with the stringers/hoops of the outer skin for added strength.

For catching the ship, if the landing pins stick out like the ones the booster, then the ship pins may melt during reentry.

The attached render below (previously posted here) seems to show some type of door right where we'd expect a catch pin to be. The render shows TPS tiles over this area, but the last test flight (IFT-6) removed the tiles right in this area and below it.

So assuming these (obviously uncertain) clues are pointing us in the right direction, if we follow that path, the question is: How will the pin move out from behind the door?  Will it swing out vertically? Horizontally? Or will it push out?

Over on X, someone posted a GIF showing how the ship catch pin might swing out vertically (link here, also attached), and that prompted some questions about load bearing over there.

on the left is the drawing of the actual hook on booster. a real thing.

Melting is "a thing with many variables". They can make it thick enough, they can use high temperature alloys etc. they can use air-dynamic tricks to deflect plasma etc.

Hinge can be employed safely with few restrictions, it is just at no circumstances can be where it is drawn.
it should be placed far inside (not to be under load), there should be provisions to redistribute load in the extended/deployed position. It can be locking pins (see big artillery pieces), it can be geometric traps (See Soyuz) etc. etc. etc.
Movable hatch door covering hook is not an issue by itself as well, (see Shuttle etc.), just extra cost. Swinging is better than pushing. You have more choice for pin geometry, it is easier to counter angular forces.

Shortly the issue with "OMG what to do with the catch pins for Starship" is overblown. It is traceable solvable problem.

[tenkendojo]

https://twitter.com/StarshipGazer/status/1861052693445575136

Humm I wonder these new hardwares on the launch tower chopsticks are for catching the upperstage? The black pad with serrated edges could be for catching some kind of pins. The white pad may be for preventing the upperstage from rolling like a firebatton after the catch, as the pins will be likely installed past the "plasma-line" of the upperstage hull to avoid heattiles. This would also explain why the black pad is protruding further out.