Elon Musk made the decision to use stainless steel instead of carbon fiber/epoxy materials for his Starship.
Stainless steel properties:
- Very ductile, very tough. No fracture issues
- that at cryogenic temperatures, the strength is boosted by 50 percent.
- it’s obviously cheap, it’s obviously fast.
- It has a high melting point. 1600 degrees Fahrenheit.
Elon Musk also proposed a transpirational heat shield:
“You just need, essentially, [a stainless-steel sandwich]. You flow either fuel or water in between the sandwich layer, and then you have [very tiny] perforations on the outside and you essentially bleed water [or fuel] through them … to cool the windward side of the rocket.” – SpaceX CEO Elon Musk.
All in all, this would appear to be the perfect application for Hexaflex.
Hexaflex can be fabricated from a continuous sheet of stainless steel that has been die cut with a repeating geometric design, creased and folded concertina style in upon itself to make a double sided core material that is flexible, able to vent, exhibits good bend and shear strength and has a large surface bonding area rendering it suitable in the construction of lightweight sandwich panels.
A transpirational heat shield must be able:
- to efficiently join inner and outer shell surfaces with stringers
- to provide a clear interstitial space, allowing fluids to flow through its structure
- to be formed into compound curvatures
- to serve double duty as structure
Expanding on the concept of thermal protection systems, Hexaflex panels can be arranged in multi-layers or plies in order to create storage for different gasses or liquids.
