> Second stage reuse seems the far more challenging problem.
Sure, SpaceX has been doing first stage reuse for a long time now. But they have demonstrated landing the second stage successfully at sea twice now with the same sort of smoothness that they demonstrated once for the booster before they then caught the booster on the first real try.
A partial list of unbelievably hard things that SpaceX has so far made seem easy:
- building a rocket from scratch
- landing Falcon 9 boosters
- landing Falcon 9 boosters *reliably*
- 3x weekly launch cadence (Falcon)
- the bellyflop manoeuver
- mass manufacturing(!) a rocket engine
- catching the booster
- simulated landings of the ship
Catching the booster is really just like landing a Falcon 9 booster w/o legs, but clearly much harder.
Anyways, if they can do all those things then it's pretty clear that they can catch-land the ship.
There's still a huge list of crazy-difficult things that SpaceX say they want to do that are hard to believe are possible, except for the fact that SpaceX has already done so many unbelievably difficult things already.
They have a history of pursuing solvable problems and abandoning those that were not working out or had better alternatives. Parachute recovery of the booster was abandoned in favor of propulsive landings. Catching fairings was abandoned for water proofing. Proposed Falcon and Dragon variants were abandoned as was Dragon propulsive landing. They abandoned carbon fiber construction and multiple concepts for Starship/Heavy.
The tiles in combination with ablative materials and the insane robustness of a steel vehicle is sufficient to get Starship through re-entry and soft land in the ocean. We know ceramic thermal tiles worked on Shuttle and X37B and presumably will on Dreamchaser so while the success was an awesome achievement it wasn't unlikely given time to refine their methods.
SpaceX are limited by the properties of real materials, not their ambitions, and we still don't know if rapidly reusability is possible with ceramic tiles or if their fragility will require inspections and refurbishment. They can't do it with ablatives and there aren't many other options. I am optimistic but also realistic about the difficulties of what they are attempting. Sometimes risky projects run into brick walls and you don't know what is possible until you try.
If the ceramic tiles aren't working out, I think they could try transpiration cooling (previously planned for Starship) or a metallic heat shield (was planned for VentureStar). Or some combination. There seem to be quite a few options.
I would say they are there. Sure, they're having some burn through on the flaps, but they managed to hit their virtual landing spot anyways, and if they caught a slightly damaged ship they could study that damage better, repair it, and refurbish the ship.
But I imagine that by IFT6 they'll have nailed the flap burn through problem.
They can't have burn through like that and achieve the kind of rapid reuse Starship needs to be useful outside low to mid Earth orbit, to go outside of there it requires a large number of flights to refuel the one Starship that will go on to Moon/Mars. Without the ability to refuel for Moon or beyond trips Starship is trapped in LEO/MEO because it's hauling around so much extra mass for it's own reusability.
IMO a better use for it might be to ferry up large pieces of purpose built craft with less excess dry weight. A single reusable Starship launch can put the entire mass of the Apollo craft needed to make it from LEO to the Moon and back into LEO. Put a craft in two launches and dock it in orbit and you've got a huge capability to put a lot of mass onto the moon and still use the cheap cost to orbit Super Heavy gives.
They landed an earlier version of the second stage on the ground a few times as well. It's the atmospheric reentry from orbital velocity that currently necessitates the safety of a splashdown: they're not going to risk bringing a damaged and potentially uncontrollable vessel down over land, even if they could nail the landing with an undamaged ship.
Sure, SpaceX has been doing first stage reuse for a long time now. But they have demonstrated landing the second stage successfully at sea twice now with the same sort of smoothness that they demonstrated once for the booster before they then caught the booster on the first real try.
A partial list of unbelievably hard things that SpaceX has so far made seem easy:
Catching the booster is really just like landing a Falcon 9 booster w/o legs, but clearly much harder.Anyways, if they can do all those things then it's pretty clear that they can catch-land the ship.
There's still a huge list of crazy-difficult things that SpaceX say they want to do that are hard to believe are possible, except for the fact that SpaceX has already done so many unbelievably difficult things already.