Why is catching the SpaceX booster in mid-air considered much better and more advanced than just landing it in some launchpad ?
In: Planetary Science
SpaceX have had some issues with their attempts at landing a rocket on a landing pad. The landing legs have to be very light because the weight margins of the rocket is already very tight and any mass in the landing legs will reduce the payload mass. Some customers have been paying SpaceX to not outfit their Falcon 9 rockets with landing legs so their satellites will fit, a full rocket is cheaper then a few extra tons of cargo to space. The light legs have collapsed in some landings. Building the legs stronger would make them heavier. Especially for the Starship rocket the legs would have to be very strong and heavy.
The second issue is that the landing pad have issues with the rocket exhaust. During a landing the rockets shoot out a huge amount of supersonic plasma directed straight at the pad. This can melt steel and even make concrete explode. For launches they raise the rocket up a bit and also carefully position it over a trench with a flame deflector made of steel and covered in water. But this is a hazard for the landing legs. And even then the launch pads is regularly damaged by flying pieces of the pad, a few times this have damaged the launching rocket as well. So this is a much bigger issue when the rocket is coming towards the pad instead of away and when the rocket comes much closer to the pad then during launch.
The “chopsticks” is an attempt at overcoming these issues. Firstly all the landing structure is on the ground and can be built very strong without sacrificing any payload mass. And secondly it can catch the rocket at a significant height above the pad so that there will be less damage and so that the rocket will not be hit by any debris.
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