THE ULTIMATE REUSABLE HEAT SHIELD FOR MARS:
MATECH’s 5000F C/ZrOC TPS offers the ultimate in reusability. While LEO returns don't require 5000F capabilities, this ability guarantees 3000F performance for hundreds of safe missions. Reusability is the key to mission affordability. For more ambitious missions, Lunar return and Mars return, MATECH C/ZrOC is absolutely imperative!
According to a very recent press release [1] and article in CompositesWorld [2] by Grace Nehls, Sierra Space has selected a layer of C/SiC ceramic matrix composite (CMC) on top of light-weight and highly insulative silica-based tiles, modelled after Space Shuttle tiles. For the lower heat flux of LEO return, this may be a viable heat shield solution.
As Damond Benningfield wrote for the Smithsonian Magazine, for LEO return, “the tiles exposed to reentry temperatures of up to 2,300 degrees Fahrenheit [3].” Benningfield also stated “Tiles are too brittle to attach to the orbiter directly.” This underscores two inherent challenges to the very light-weight and highly porous silica-based Space Shuttle heat shield tiles. They are not high temperature capable enough for Lunar or Mars return, and they are also fragile and weak.
For more aggressive mission requirements, such as Mars return, envisioned by SpaceX, what worked for the Space Shuttle simply won’t work. Consider the fact that the reentry velocities for LEO return are much lower than Lunar and Mars return [4, 5]. “The atmospheric entry interface velocity upon return from the Moon is approximately 11.1 km/s (36,500 ft/s; 40,100 km/h; 24,900 mph) whereas the more common spacecraft return velocity from low Earth orbit (LEO) is approximately 7.8 km/s (25,649 ft/s; 28,000 km/h; 17,000 mph) [5, 6].”
Mars return velocity is much higher at 12.5 km/sec (41,104 ft/s; 44,800 km/h; 27,200 mph). To date, no reusable non-ablative heat shield has ever been demonstrated for either Lunar or Mars return. Yet, this is EXACTLY what Elon Musk is seeking. In his tweet of November 19, 2024, Elon Musk wrote “The biggest technology challenge remaining for Starship is a fully & immediately reusable heat shield. Being able to land the ship, refill propellant & launch right away with no refurbishment or laborious inspection. That is the acid test [7].” He’s absolutely right.
MATECH has the solution for Starship. In the figure below, under identical conditions and a surface temperature of nearly 5000F, C/SiC CMC is compared to MATECH C/ZrOC CMC. The difference in ablation is dramatic [8]. Under very extreme heat flux conditions at AFRL’s LHMEL facility, the ablation rate of fully dense C/SiC is 100 times higher than MATECH C/ZrOC. This is exactly what Starship needs. MATECH’s C/ZrOC can be artfully combined with existing materials to produce a composite structure that is extremely high temperature capable, reusable, mechanically tough, light weight, and highly insulative, thereby meeting all of Starship’s Lunar and Mars return requirements.