Shock Absorbers for Chopsticks...

[brice]

I've been curious about how the chopsticks will handle impact loads when catching boosters and ships. It looks to me like the chopsticks are designed for shock absorbers that haven't been installed yet. I'll explain below. Has anyone heard anything about this? The supplier might be Taylor Devices. Just a guess.

...About the need for shock absorbers...

We've seen how slow the chopsticks move, so active speed matching is not going to happen during the catch. The brakes on the drawworks could be loosened to allow some travel on impact, but that sounds risky. The latest render of a booster catch (Musk's presentation) showed a booster hovering between the chopsticks before engine cut off. But even with perfect control there will be shock loads on contact. The chopsticks probably can't be damaged, but the boosters & ships will have load limits. (One of the genius aspects of catching boosters & ships like this is that most of the loads will be in tension not compression. Steel is much stronger under tension, so there will be less chance of damage compared to the risks of crush damage from a hard landing on solid ground. Falcon legs contain shock absorbers.)

To protect boosters and ships there will need to be some sort of shock absorbtion built into the chopsticks. They will be giant monsters like the ones used on bridges or in seismic protection of buildings. In other industries they are called isolators, or dampers, or crane buffers.

...Chopsticks are waiting for them:

It looks to me like the chopsticks are designed for shock absorbers. The two long rectangular rails are connected to the tubular structures by parallelogram linkages. This means they are intended to move vertically a small distance. I reviewed the pics of their construction, and it looks like the rectangular rails are not welded to the tubular structures. They appear to be attached only by the parallelogram linkages.

Right now they are resting on brackets. I think this is their home position. Imagine the two rectangular rails are lifted up a few feet by giant shock absorbers. After impact they would settle gracefully onto these home position brackets.

See attached pics. These are 2 crops of this reddit pic: https://i.redd.it/7lq0ygnu5r581.jpg plus a crop of a bocachicagal construction pic (via nsf?) I lost the link to.

You can see thick vertical plates on the vertical tubes below the rails. They each have single through holes to mount something. These could be mount points for the shock absorbers. I imagine the top ends of the shock absorbers would be welded directly to the bottom of the rectangular rails. Large dampers might hang from these mount points, while "smaller" ones might fit between the holes and the rails. The dampers could be custom designs, which might explain the delay.

The top of both rectangular rails look to me like they are waiting for giant rubber pads. There are short steel "walls" that surround the top edges which could hold pads in place. Rubber pads would be taller than these walls. It might be the kind of indestructible rubber that holds up elevated highways. (Next time you're under an overpass, look at the point where the roadway touches the support columns. Often there are black rubber pads supporting the whole thing.) Or it might house an array of air bladders like what's used in the suspension of air ride trucks and buses. Industrial air bladders can be very durable. Again maybe something custom.

I'm imagining that the booster grid fins would flip over 180 degrees so the smooth sides contact the rubber-topped rails on the chopsticks. The latest render showed the booster caught by the fins. It's unclear to me what are the catch points on ships. Perhaps there will be a fixture added at a later date? Or perhaps the fins are actually strong enough to handle the impact loads without damage. But what about the TPS tiles?

...Possible supplier of shock absorbers...

Taylor Devices makes the kinds of shock absorbers that might fit the chopsticks. They have done work for NASA and have lots of aerospace experience. They do bridge dampers and seismic building isolators. They make "crane buffers" to catch runaway overhead cranes in steel mills (like runaway train arrestors at the ends of tracks). Big stuff for heavy loads.

They have special damper technology that used to be military restricted, now declassified. "Originally developed for NASA in the 1960s, fluid viscous dampers have successfully transitioned into the civil engineering community." Seems like a perfect fit for a radical one of a kind crazy project like catching starships.

Here are some links into their site:

https://www.taylordevices.com/industries/aerospace-defense/

https://www.taylordevices.com/industries/structural/

https://www.taylordevices.com/products/crane-buffers/

Space Technology Hall of Fame Inductee:

https://www.spacefoundation.org/2016/06/02/how-taylor-devices-seismic-dampers-save-lives/