To create a fully reusable launch system for its interplanetary Starship vehicle, SpaceX had to address a number of technical challenges, such as slowing down a large spacecraft as it re-enters Earth’s atmosphere at nearby orbital speeds.
But perhaps the biggest challenge – as always, with rockets – is quite physical: its set. The goal with rockets is to build the lightest vehicle possible with the highest impact. In theory, that sounds easy. But in practice, having volatile liquids at high pressures is nothing easy. And with a fully reusable launch system, SpaceX has the added challenge of building vehicles that can withstand the rigors of launching, perform in a vacuum, and then return to sea-surface pressure by screaming from the atmosphere.
The need to create light, robust and adaptable vehicles sometimes leads to interesting design choices. In late 2020, SpaceX founder Elon Musk took to his favorite social network, Twitter, to share with his followers. “We will try to grab the super heavy booster by the hand of the loading tower, using grid fins to carry the load.” He said. The super heavy rocket, which is expected to have about 28 Raptor engines, will allow the starship to enter Earth orbit.
At first blush, these sounds Crazy. How do you catch a falling rocket with a launching tower? And why would you risk valuable launch infrastructure by trying to land a giant rocket over it?
One answer is collective. The company’s first phase of the Falcon 9 rocket uses four large landing legs made of carbon fiber and aluminum to stabilize the vehicle as it descends. Despite being made of this light material, the combined mass of the four landing feet is still about 2 metric tons. Legs for very large super heavy boosters often need to be enlarged, perhaps on the order of 5 to 10 metric tons.
Who needs legs?
It will be even more efficient. If the SpaceX can build a launch tower arm or a pair of weapons to catch a super heavy booster, it can quickly return to the launch mount. After such a rocket – and it requires years of refinement and experimentation – will be quickly inspected, renewed and re-launched. Maybe within an hour, Kasturi said.
It is not clear whether this is possible. But in theory, a super-heavy booster could descend under the power of its 28-engine subset, come very close to the hover, and reach out from the Lower Tower to grab the Braber Stir. This may sound like a crazy maneuver, but a few years ago an autonomous drone sent a ship into the Atlantic Ocean to catch a falling rocket.
It remains to be seen whether all this works. SpaceX has tried many things in the past in terms of rockets to refute these ideas. This is one of the keys to the success of Musk and his leadership style. It tells its employees to perform almost impossible tasks – such as a complete reusable orbital system. And then it gives them the freedom to experiment and sometimes fail.
The idea seems to be crazy enough to make it work.