It's difficult to overstate how important the milestone of catching the booster is. Now we have a reusable rocket an order of magnitude larger than anything we've had before, and the cost of kg to orbit just nosedived.
Second stage reuse seems the far more challenging problem. Other companies should have reusable boosters soon but if significant amounts of Starship continue to ablate on the way down they could be faced with a disposable Starship competing with smaller and cheaper second stages that are well sized for typical payloads. We already knew boosters can be flown back to launch sites reliably with high accuracy. We don't k…
Supposedly they’re working on both a reusable and cost optimised non-reusable second stage at the same time. And they don’t really know yet which one will end up being cheaper.
You also see this kind of thinking with Rocket Labs neutron rocket. Where they focus on making the reusable booster do more, while making the second stage smaller, cheaper and simpler.
I think if it wasn’t for the rocket engine this wouldn’t be a question at all. The tank doesn’t have much value. It’s just a thin shell and probably a fraction of the cost of the fuel.
So I’m thinking, perhaps the optimal solution is something like this: the bottom part of the second stage with the engines separates, and a small engine and fuel tanks places the engines in a stable orbit. The tank itself is deorbited and burns up.
At some point later something like the Starship collects several second stage engines and deorbits them safely to be reused.
Or perhaps just the engines can be immediately deorbited with an inflatable heat shield and parachutes.
