Your comment mixes a few kernels of truth with incorrect premises, false information and wild speculation.
>> Stainless steel was specifically chosen so that starship wouldn't need a heat shield and would survive re-entry with transpiration cooling.
Not really, no. When SpaceX switched to stainless steel in 2019, Musk simultaneously described using ceramic hex tiles on the windward side. They showed hex-tile testing publicly in March 2019. Tiles were not an afterthought added later because transpiration "failed". Musk did initially discuss transpiration/regenerative cooling concepts for hot spots (stuff like a double wall, or fluid-cooled steel skin) but this was framed as in addition to tiles, not as a full replacement.
>> Additionally, at the time much hooplah was made about stainless steel being cheaper and more formable which would reduce production costs. This is just nonsense.
It is not. In 2019, carbon fiber was $135/kg with 35% scrap (so effective cost was $200/kg) vs. $3/kg for stainless steel. That's a two orders of magnitude difference in raw materials.
300-series stainless (301/304L) is widely used precisely because it is formable (301 work-hardens to high strength) and readily weldable (304L). That doesn't make it effortless but it's still much easier to work with than aerospace aluminum-lithium, which requires specialized friction-stir welding and tight process control.
>> The increased weight required them to reduce safety features
This is just conjecture. There's no evidence that Starship has reduced safety features to compensate for stainless steel + heat shield weight.
> ot really, no. When SpaceX switched to stainless steel in 2019, Musk simultaneously described using ceramic hex tiles on the windward side. They showed hex-tile testing publicly in March 2019. Tiles were not an afterthought added later because transpiration "failed". Musk did initially discuss transpiration/regenerative cooling concepts for hot spots (stuff like a double wall, or fluid-cooled steel skin) but this was framed as in addition to tiles, not as a full replacement.
Starship was switched to stainless steel in 2018. It was originally supposed to have an all-metallic heat shield. Ceramic heat shields for critical areas were added months later in march 2019, only in July of 2019 did the windward ceramic heat shield get added, which was after the starhopper prototype had flown and several more prototypes were already being built, and transpiration was still in active development at the time. Transpiration cooling was not dropped until 2020. The heat shield has been steadily growing since then, with the addition of more tiles to cover a larger area and an ablative underlayment to provide more protection to the underlying steel.
> It is not. In 2019, carbon fiber was $135/kg with 35% scrap (so effective cost was $200/kg) vs. $3/kg for stainless steel. That's a two orders of magnitude difference in raw materials.
And what did aluminum cost at the time? Yes stainless is cheap compared to the most expensive alternative, that does not make it cheap.
> 300-series stainless (301/304L) is widely used precisely because it is formable (301 work-hardens to high strength) and readily weldable (304L).
Work hardening is bad for formability.
> it's still much easier to work with than aerospace aluminum-lithium, which requires specialized friction-stir welding and tight process control.
Lithium aluminum is an exotic aluminum alloy. You would use an alloy like 7005 which is weldable.
> There's no evidence that Starship has reduced safety features to compensate for stainless steel + heat shield weight.
That is what reduced margin means. Every rocket has less safety features than it would if weight were not an issue. The more weight increases, the more everything has to give to still remain capable of completing the mission. IFT 9's failure was due to Starship relying on autogenous supercharging to save weight. No one can say how much better starship would be if it had more margin, but it undoubtedly would be better.
>> Stainless steel was specifically chosen so that starship wouldn't need a heat shield and would survive re-entry with transpiration cooling.
Not really, no. When SpaceX switched to stainless steel in 2019, Musk simultaneously described using ceramic hex tiles on the windward side. They showed hex-tile testing publicly in March 2019. Tiles were not an afterthought added later because transpiration "failed". Musk did initially discuss transpiration/regenerative cooling concepts for hot spots (stuff like a double wall, or fluid-cooled steel skin) but this was framed as in addition to tiles, not as a full replacement.
>> Additionally, at the time much hooplah was made about stainless steel being cheaper and more formable which would reduce production costs. This is just nonsense.
It is not. In 2019, carbon fiber was $135/kg with 35% scrap (so effective cost was $200/kg) vs. $3/kg for stainless steel. That's a two orders of magnitude difference in raw materials.
300-series stainless (301/304L) is widely used precisely because it is formable (301 work-hardens to high strength) and readily weldable (304L). That doesn't make it effortless but it's still much easier to work with than aerospace aluminum-lithium, which requires specialized friction-stir welding and tight process control.
>> The increased weight required them to reduce safety features
This is just conjecture. There's no evidence that Starship has reduced safety features to compensate for stainless steel + heat shield weight.