New transport table & Possible catch sequence

[brice]

The new booster transport table (see RGV Aerial Photography, Episode 13 on YouTube) may be intended as part of the catch sequence.

I've long wondered how the chopsticks would reorient a catch for stacking. Mechanically they don't seem to have this ability. Musk once joked about "tank treads" on top, but there doesn't seem to be room for an active surface on top of the chopstick rails. Here's what I'm envisioning based on what can be seen now. The sequence I describe allows for a lot of slop in the catches. Windy days, low fuel, etc. Whereas stacking relies on the precision of the tow-ball geometry.

1. Pre-catch prep involves retracting the two tow-ball devices that engage the hard points on ships. The tow-balls probably can be stowed below the rail level, so the rails are clear for the catch.
2. Make the catch. Booster flips grid fins upside down and fins land on rubber covered rails. Impact is dampened by giant shock absorbers not yet installed. (See my prev post linked at end.) Ship is caught by fins. The rubber pads on the rails protect the TPS tiles from damage.
3. Since the rails cannot reorient the ship / booster, the chopsticks must lower them to the ground to be properly oriented for re-stacking.
4. The new booster transport table has two arms that can reach up and grab guide points on the booster. This will allow a quick transfer from the chopsticks. An SPMT would position the table under the booster, chopsticks then lower it, the table arms reach up and grab the booster, guiding it into the retaining ring, and finally the 20 hydaulic clamps engage the booster ring. I expect there will be a similar transport table built for ships, with vertical guide arms to facilitate quick transfers from the chopsticks after catches.
5. SPMT reorients booster/ship so hard points line up with the tow-ball lift points on the chopsticks. The booster has similar hard points below the grid fins. There appear to be four hard points on booster 4, every 90 degrees. Maybe part of an earlier design choice that will disappear on newer boosters.
6. Chopsticks lift boosters in the same way it has lifted ship 20, by the hard points, using the tow-balls.
7. Final stacking alignment is done by moving the two tow-balls on the rails. Since they are ball and socket joints, the tow-balls can be shifted laterally in opposite directions to achieve a twisting motion of the booster / ship. The range of motion is small, but allows precise control of both position and angle before docking. During the night stacking before Musk's presentation I'm pretty sure I saw a twist motion in addition to the swinging of the chopsticks and the latteral (radial) shifting from the tow-balls.

This sequence matches what has already been demonstrated by the chopsticks. Maybe a future redesign will allow the chopsticks to reorient catches directly. Or maybe future catching will engage the hard points directly, but that kind of precision seems far away. I mean, why build giant arms if you think you can align a hovering booster's hard points with tiny (relatively) tow-balls?

I think SpaceX has intentionally decoupled catching from stacking. It's just too difficult to give the chopsticks the ability to directly reposition a catch. Too many degrees of freedom, and too many ways to damage the ship / booster with such heavy machinery. Tank treads would rip apart the ship fins if the ship needed rotation to reorient. Especially if a rubber surface was used to protect the tiles. SPMTs are cheap!


Attached is crop from today's live stream showing the chopstick rails and their parallelogram linkages. See my prev post about Shock Absorbers for Chopsticks:

https://forum.nasaspaceflight.com/index.php?topic=56018.0