Comment by modeless | Hacker News Reader

Comment by modeless | Hacker News Reader

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Nitpick: the booster does not achieve orbit. If it did it would need a heat shield like the upper stage.

What's new in Starship? Rapid turnaround. Catching the returning rocket with the launch tower. A durable heat shield that needs zero refurbishment for back-to-back flights. The sheer number of engines on the first stage and the volume of engine production needed for that. Orbital refueling. The landing flip maneuver.

There is a lot of new stuff in Starship, and not all of it is proven yet. Personally I think the biggest remaining risk is the heat shield. I'm no expert, but my speculation is that there will be several reentry failures, and refurbishment will limit turnaround speed for a long time. I've also heard a lot of people saying that orbital refueling will be very difficult. I'm also worried that landing failures will wreck the ground support equipment. And I think it's very unlikely that the reliability of the whole system can ever be good enough for the airliner-like earth-to-earth passenger service that SpaceX has proposed.

All that said, I'm very much in agreement with the article that NASA needs to radically change their future plans, because while Starship is not completely proven, it is clearly derisked to the point where it's going to be revolutionary, even if some of the above risks prevent the total potential from being realized. HLS was the first time NASA showed that they realize this, but they are still doing tons of stuff outside HLS that makes little sense in a Starship world.

Rapid turnaround is not demonstrated. Nor is it even, in fact, planned, in any real sense. I.e., to be clear, there is no evidence that they have any idea how to achieve rapid turnaround of a Starship orbiter.

(Superheavy is a different story.)

All this turns on the design of the heat-shield tiles. Those we have seen are basically the same as on the shuttle. Each individual tile needs a great deal of personal attention before and after each use, including squirting in some goo that will boil off on the next flight. Many will need to be replaced, each flight.

So, turn-around time is weeks, minimum. More probably a month or two, or three.

It is conceivable that a future version of Starship will have a heat shield that needs less attention. Maybe a fabric shroud in place of tiles, over most of the hull, will turn out to be practical. If that happens, it might get possible to turn around a re-entered Starship faster. But that will require entirely new development not obviously begun.

I will be happy to be proved wrong.

Despite all of the above, even without quick turnaround or even re-usability, Starship is obviously overwhelmingly superior in every conceivable way to Artemis/Ares. NASA has the unenviable chore of trying to unload that turkey on some commercial contractor to get out from under the obligation to pour ever more treasure down its gaping maw, endlessly. If NASA succeeds in selling it at a penny on the dollar to Marietta, and leaving Marietta to try to find someone, anyone willing to pay for even a single hull, we can all breathe a sigh of relief.

I don't think that the heat shield is the same as the shuttle's. The tiles are tougher and attached in a different way, and the underlying steel structure can stand more heat than the shuttle's aluminum could.

Orbital refueling is required for HLS and depends on rapid turnaround so SpaceX and NASA must have some confidence that it can be achieved without a radical redesign.

There are differences from the shuttle's tiles, but they are much more similar than different.

Rapid turnaround seems at this stage more an aspiration than a designed feature. It was the same with the shuttle. In that case it was never achieved at all, even with decades of experience.

Turnaround and reuse are desirable, particularly to minimize cost, but not strictly necessary for a successful mission.

The tiles on Starship are much more uniform than on the Space Shuttle, so they are cheaper to produce and less complex to replace.

That mainly affects cost, not turnaround time. And there are anyway many unique tiles, particularly around fins and on the nose cone.

Even for some reason Starship can not return in its early development, it still triumphs SLS by a wide, wide margin.

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