Rocket Lab Neutron rocket

[adiggs]

And when SpaceX goes for exotic and modern over old/mundane, its revolutionary and industry leading and leaving everyone in the past, right?

Of course!

 

[Ben W]

So I’m a bit annoyed at both Relativity and Scott Manley for dissing stainless steel. Manley even gets the reason for stainless steel wrong, he said it was for fast iteration. The real reason SpaceX is using steel is that Starship is fully reusable, unlike Neutron. That means, unlike Neutron, Starship re-enters the atmosphere at 25,000 kph. Steel allows a far smaller heat shield to be used, and doesn't even need it on the leeward side of Starship. Anyways, just wanted to get that off my chest.

That explains why Starship has to be SS. But it's possible that Super Heavy might still benefit from using composites, since its entry profile is much tamer. Obviously the fast iteration and low cost of SS is important for its own sake during the development phase, but once the booster achieves high reliability and reusability, the cost of materials and construction becomes less of a factor. At that point, one wonders what the "platonic ideal" booster might be, in terms of lifetime cost/kg to orbit.

 

[Cosmacelf]

That explains why Starship has to be SS. But it's possible that Super Heavy might still benefit from using composites, since its entry profile is much tamer. Obviously the fast iteration and low cost of SS is important for its own sake during the development phase, but once the booster achieves high reliability and reusability, the cost of materials and construction becomes less of a factor. At that point, one wonders what the "platonic ideal" booster might be, in terms of lifetime cost/kg to orbit.

Good point about Super Heavy. I do recall Elon mentioning that one of the problems SpaceX had with Falcon 9 was mating the carbon fiber interstage with the rest of the rocket since they were made of different materials, and thus had different expansion rates at various temperatures (cryogenic to hot from flight).

 

[bxr140]

one wonders what the "platonic ideal" booster might be, in terms of lifetime cost/kg to orbit.

Top level trades like "what material" are never self-evident, and they're highly dependent upon the criteria against which the trade is analyzed so there's not really one answer to the question. In nothing-new-under-the-sun news, it really depends on how the mission values price vs schedule vs performance vs reliability.

From a literal "cost/kg to orbit" question (which, to telegraph the point, is only part of Starship's mission), it would be hard to argue against some combination of aluminum and carbon composite.

Also true is that for the Starship mission it would be hard to argue against heavy use of steel.

Though, change some parameters in the aspirational Starship mission (like, not so many units/flights) and its possible/likely Aluminum would take the top spot.

 

[Grendal]

Though, change some parameters in the aspirational Starship mission (like, not so many units/flights) and its possible/likely Aluminum would take the top spot.

Which is why Starship/SH design has changed multiple times. The rocket equation is a mean bastard. It's only a percentage point or two from the greatest rocket ever created to something that just doesn't work.

The difference with Falcon 9 and Starship/SH is that F9 had to launch to make money. Modifications and iterations happened while launches were happening. The manufacturing and production lines were grown over time. Starship/SH is being improved and designed while the workhorse F9 continues to do the work. Elon is as focused on the manufacturing and production just as much as the design, if not more so.