[sobellian]

The space program stalled because pouring national wealth into gigantic single-use rockets was unsustainable. They tried with Shuttle but the material science wasn't there yet (heck it might not be even now, it doesn't seem that they've really nailed down the heat shield on Starship yet).

[dotnet00]

I don't think Shuttle's issue was that the material science wasn't there. The issue was the way the design was constrained, and the general aerospace culture at the time (that only began to change with "New Space").

Shuttle's heatshield would've been much less dangerous if it wasn't facing a giant ice and insulation covered external tank (like, if it was mounted on top of a booster), but the Air Force's demand for crossrange forced giant wings, which forced the lower mounting position.

They could've iterated on heat shield designs, particularly with attachment mechanisms, but every mission had to carry people, so you couldn't risk it, and anyway, the industry culture was already set in the "even the simplest things must cost large amounts of money and time" stage.

One of the key points that I feel a lot of people miss is that Starship is pretty much the first program actually doing the flight testing needed to understand the engineering requirements for an efficient fully reusable heatshield. They don't have much prior art to look at for tile spacing, mounting mechanisms, metal tiles or transpiration cooling. The fundamental materials haven't changed a lot, but we can see over test flights that SpaceX are figuring things out.

In the early days they used to lose tiles all the time, even after just pressure testing IIRC. Nowadays they may barely lose any tiles on static fire tests. Similarly, tile loss on reentry has decreased greatly, and we've gone from seeing plasma leaving the fins barely attached, to the latest test, where the fins were pretty much fully intact.

[sobellian]

I'd say material science since the only non-ablative material we can use is too brittle compared to a normal fuselage. I really hope they succeed but it's a pretty fundamental problem to have unanswered this deep into the program development (and gating Artemis no less). Also hard to judge their progress without the data their heat shield team is getting, see https://x.com/mcrs987/status/1978183753114505496 for example. It's great that they can tolerate loss of vehicle & have better margins due to the steel fuselage but for Artemis and Mars they need to solve it or they'll be burning up hardware fast, literally.

[jjk166]

The issue with the shuttle wasn't the material science. It was designed around a mission profile of servicing spy satellites, which at the time had film which needed to be developed. The defense department gave NASA requirements which could only be satisfied by moving the orbiter to the side of the rocket, dramatically increasing potential damage to the thermal tiles and making crew escape basically impossible. This was all justified by the incredibly large number of flights that the shuttle would fly to service these satellites, and the money the defense department would pay for these missions. The shuttle was screwed late in production when digital camera technology allowed for spy satellites that didn't need regular servicing, eliminating most of the demand for the shuttle and rendering the infrastructure designed for it unsustainable.

[fluoridation]

Wait, TV signals weren't unknown in the '80s and '90s. Why were they using film instead of TV cameras?

[Veedrac]

Au contraire, the space program stalled because pouring national wealth into gigantic space projects was _too_ sustainable. The idea that NASA has had a lack of funding is a myth. The problem has long been them spending it ineffectively.

[vlovich123]

> because pouring national wealth into gigantic single-use rockets was unsustainable

You mean what SpaceX does as a matter of course and proved you make it cheap just through scale and iteration?

[sobellian]

SpaceX uses flight proven boosters. The rockets aren't quite as gigantic nor as single-shot as the Saturn V. Also, they launch satellites into LEO for commercial reasons. It's quite a different beast from lobbing LEMs at the moon where the money is essentially lit on fire.