Not to mention the damn test rocket looks like a real 1950's rocketship! Robert A. Heinlein would be proud.
https://www.popularmechanics.com/space/ ... ess-steel/
If you look at the properties of a high-quality stainless steel, the thing that isn’t obvious is that at cryogenic temperatures, the strength is boosted by 50 percent...
...See, here’s the other benefit of steel: It has a high melting point. Much higher than aluminum, and although carbon fiber doesn’t melt, the resin gets destroyed at a certain temperature. So typically aluminum or carbon fiber, for a steady-state operating temperature, you’re really limited to about 300 degrees Fahrenheit. It’s not that high. You can take little brief excursions above that, maybe 350. Four hundred, you’re really pushing it. It weakens. And there are some carbon fibers that can take 400 degrees Fahrenheit, but then you have strength knockdowns.
But steel, you can do 1500, 1600 degrees Fahrenheit...
...Oh, and I forgot to mention: The carbon fiber is $135 a kilogram, 35 percent [is] scrap, so you’re starting to approach almost $200 a kilogram. The steel is $3 a kilogram.