SpaceX may try to catch a falling rocket with a launch tower

To build a fully reusable launch system for its Starship interplanetary vehicle, SpaceX had to solve a myriad of technical challenges, such as slowing down the massive spacecraft as it re-enters Earth’s atmosphere at near orbital speeds.

But perhaps the biggest challenge – as always, with rockets – is pretty mundane: its mass. The goal with a rocket is to build the lightest vehicle possible with the most performance. In theory, it sounds simple. But in practice, containing volatile liquids at high pressure is anything but simple. And with a fully reusable launch system, SpaceX has the added challenge of building vehicles that can withstand the rigors of launch, operate in a vacuum, and then roar back into the atmosphere to land at pressures at the level of. the sea.

The need to build light, strong and adaptable vehicles sometimes leads to interesting design choices. At the end of 2020, SpaceX founder Elon Musk took to his favorite social network, Twitter, to share one of them with his followers. “We will try to grab the Super Heavy Booster with the launch tower arm, using the fins on the grid to pick up the charge,” he said. The Super Heavy rocket, likely to have around 28 Raptor engines, will launch Starship into Earth orbit.

At first glance, it sounds foolish. How to catch a falling rocket with the launch tower? And why would you risk the precious launch infrastructure trying to land a huge rocket right above?

One answer is mass. The first stage of the company’s Falcon 9 rocket uses four large carbon fiber and aluminum landing legs to stabilize the vehicle as it lands. Although made of these lightweight materials, the combined mass of the four landing legs is still around 2 tons. The legs of the much larger Super Heavy thruster would probably have to be several times the size, perhaps in the range of 5-10 metric tons.

Who needs legs?

It would also be more efficient. If SpaceX can design a launch tower arm, or a pair of arms, to grab the Super Heavy booster, it could be moved around the launch pad pretty quickly. Such a rocket could then – and it would take years of refinement and experimentation – to be rapidly inspected, refueled and relaunched. Maybe even in an hour, Musk said.

It is not known if this is even possible. But in theory, a Super Heavy booster could descend under the power of a subset of its 28 engines, come very close to a hover, and the launch tower arms could extend to grab the booster. It sounds like a pretty crazy maneuver, but a few years ago sending an autonomous drone into the Atlantic Ocean to catch falling rockets.

It remains to be seen if this all works. SpaceX has tried a lot of things in the past when it comes to rockets just to dismiss these ideas. This is one of the keys to success for Musk and his leadership style. It asks its employees to do things that are nearly impossible, like building a fully reusable orbital launch system. And then it gives them the freedom to experiment and, sometimes, to fail.

This idea seems crazy enough to work.