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The advantage of steel is the tiles don't have to be as thick and heavy. I don't think they ever claimed it doesn't need a heat shield. HLS is the Starship tha

The advantage of steel is the tiles don't have to be as thick and heavy. I don't think they ever claimed it doesn't need a heat shield. HLS is the Starship that never re-enters you're asking for. The problem is it needs refueling in orbit after launch to get anywhere, with 10+ tanker launches required. For that to be practical you need reusable tankers. So you still need a reusable heat shield to get beyond Earth orbit even if your crew vehicle isn't coming back. Also Starlink is the funding source for Starship, and Starlink will benefit a lot from second stage reusability for Earth launches as well.

api 1y ago
For no heat tiles I am thinking of the original idea of transpiration cooling, which I suppose ended up too complex or itself too heavy. I didn’t know it was 10+ tanker launches. Is it because only a small amount of the tanker’s fuel payload is actually delivered? That makes the whole thing look less useful for going anywhere past orbit. Still useful, but less of a step change from what we have now. Maybe it’d be better to spend the whole budget on inertial confined fusion research instead. Get that working and you can really go somewhere.
- modeless 1y ago
  They are still testing transpiration cooling for potential use in areas of super high heating but I think they decided a long time ago that the mass penalty of transpiration cooling was much higher than that of ceramic tiles. Nobody knows the true number of tanker launches yet but it's going to be a lot. The ship holds ~1500 tons of propellant and payload capacity to LEO is ~150 tons, so 10 is probably a decent first guess. Less if it doesn't need to be full, more if there are a lot of losses in the process. But 10 isn't so bad if everything is reusable. It's a different way of thinking about launches. What we really need is a propellant factory somewhere other than Earth. That sounds easier than fusion rockets.

api 1y ago

For no heat tiles I am thinking of the original idea of transpiration cooling, which I suppose ended up too complex or itself too heavy. I didn’t know it was 10+ tanker launches. Is it because only a small amount of the tanker’s fuel payload is actually delivered? That makes the whole thing look less useful for going anywhere past orbit. Still useful, but less of a step change from what we have now. Maybe it’d be better to spend the whole budget on inertial confined fusion research instead. Get that working and you can really go somewhere.

modeless 1y ago
They are still testing transpiration cooling for potential use in areas of super high heating but I think they decided a long time ago that the mass penalty of transpiration cooling was much higher than that of ceramic tiles. Nobody knows the true number of tanker launches yet but it's going to be a lot. The ship holds ~1500 tons of propellant and payload capacity to LEO is ~150 tons, so 10 is probably a decent first guess. Less if it doesn't need to be full, more if there are a lot of losses in the process. But 10 isn't so bad if everything is reusable. It's a different way of thinking about launches. What we really need is a propellant factory somewhere other than Earth. That sounds easier than fusion rockets.