Elon Musk Says SpaceX Considered Using Giant Bouncy Castle or Net to Catch Starship

SpaceX considered using a big net or an inflatable cushion to catch its Starship spacecraft, Elon Musk revealed on Tuesday.

The SpaceX CEO discussed the unorthodox landing method in a Twitter thread, in which he was asked about how future versions of the Starship SN prototypes would be improved.

Space content creator Everyday Astronaut asked Musk whether the SpaceX team had considered removing Starship's landing gear and, using the weight this would save, replacing the gear with extra flaps that would slow the spacecraft down enough to be caught in "the world's largest and most ridiculous net?"

Starship’s belly flop terminal velocity is already only like 75 m/s... what if... remove the 30 tones of landing prop, add 10 more tones of flaps, get that down to like 50 m/s and just use the world’s largest and most ridiculous net? 😂🤷‍♂️

— Everyday Astronaut (@Erdayastronaut) March 10, 2021

Musk replied this would have been possible, but suggested it would not have saved enough weight to have made the landing method worthwhile.

He said: "Yeah, we talked about that internally. Could just have it land on a big net or bouncy castle. Lacks dignity, but would work. But, optimized landing propellant is only ~5 percent of dry mass, so it's not a gamechanger."

Musk suggested future Starships would not necessarily have to land themselves on the ground, though, and instead could be caught mid-air by towers.

The SpaceX head has already said this is how the company plans to land the Starship's booster, which has not yet reached the flight-ready prototype stage.

"We're going to try to catch the Super Heavy Booster with the launch tower arm, using the grid fins to take the load," Musk tweeted in December in reply to another user.

We’re going to try to catch the Super Heavy Booster with the launch tower arm, using the grid fins to take the load

— Elon Musk (@elonmusk) December 30, 2020

On Tuesday, he said SpaceX may use the same method to catch the ship as well.

SN11, the next prototype launch, will land itself normally. SpaceX engineers have been photographed testing out the landing legs on the spacecraft ahead of take-off. It is unclear when this launch will be, but the prototype is currently on the launch pad.

SpaceX has so far launched three Starship SN prototypes to high altitude, but landing them appears to be difficult. All of these high-altitude prototypes have blown up on landing, though the launch appears to have gone well in all cases.

SpaceX did not immediately explain why SN10 blew up several minutes after touching down, nor why it appeared to have landed slightly off-kilter.

Musk has now suggested the ship came down slightly too hard because the engine was low on thrust, "probably due to partial helium ingestion from fuel header tank."

SN10 engine was low on thrust due (probably) to partial helium ingestion from fuel header tank. Impact of 10m/s crushed legs & part of skirt. Multiple fixes in work for SN11.

— Elon Musk (@elonmusk) March 9, 2021

He said helium had been put into the fuel header tanks to prevent something called ullage collapse, which results when liquid sloshing around in a fuel tank ends up lowering the pressure in that tank.

Starship prototype
A prototype of Starship seen at the SpaceX's Texas launch facility on September 28, 2019. SpaceX plans to eventually use Starship for Mars missions. Loren Elliott/Getty