We propose an alternative heatshield design for SpaceX’s Starship. It solves the problem of how to efficiently make a heatshield core material made of steel alloy that can be formed into double asymmetric curvatures without distortion and which has an interstitial space to hold either fuel or water in between the sandwich layers.

SpaceX’s Starship could enter through Mars' and Earth's atmospheres at 19,000 mph. At such speeds, parts of the ship's underbelly could be exposed to temperatures of about 2,700 degrees Fahrenheit. Starship needs a heat shield that will "bleed" liquid during landing to cool off the spaceship and prevent it from burning up in the atmospheres of Mars and Earth.

“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.

A transpiration 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

The core 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, and has good bend and shear strength.

The ability of a Hexaflex panel to serve double duty as a structural component opens up the possibility of making the entire rocket skin from Hexaflex panels. They can be stacked in multi-layers or plies in order to create alternative storage for gasses liquids or rocket fuel.