Musk teases Starship in round of Twitter posts

Jason Rhian

Among a deluge of Tesla and The Boring Company tweets, SpaceX’s founder, CEO and chief rocket designer Elon Musk teased the latest about the Big Falcon Rocket “Starship.”

Although keeping the original name for the Big Falcon Rocket might have generated controversy in what goes into naming a rocket (the meaning behind the “F” sparked some debate), Musk’s latest tweets have touched onto something far more substantial — what this new rocket will be comprised of.

In the case of the newly-dubbed Starship itself, that material appears to be stainless steel. While the stainless steel is nothing new, having been invented in 1913 by Henry Brearly. Musk noted the positive aspects of the material in a Dec. 24, 2018 tweet: “Usable strength/weight of full hard stainless at cryo is slightly better than carbon fiber, room temp is worst, high temp is vastly better.”

So what type of paint has Musk selected to cover the massive new vehicle? None. “Skin will get too hot for paint. Stainless mirror finish. Maximum reflectivity.”

When it comes to the temperatures a vehicle encounters when it re-enters Earth’s atmosphere (NASA’s now-retired fleet of shuttle orbiters encountered extremes of up to 3,000 degrees Fahrenheit / 1,649 degrees Celsius), it is critical its shielding be up to the job. For this task, it appears Starship might use a regeneratively-cooled heat shield.

The heat tiles used on NASA’s fleet of space shuttles (designed and built by Rockwell International) were designed to last for the planned life of each orbiter — 100 missions. The shuttle also used thermal blankets and other systems and procedures to reduce the stress of interfacing with the atmosphere.

Heat shields used on past spacecraft have been mostly single-use. Ablative heat shields for example burned away, taking the heat with it. This type of protective system was used on NASA’s Mercury, Gemini and Apollo spacecraft.

Musk discussed using regeneratively-cool protection Starship by stating: “Leeward side needs nothing, windward side will be activity cooled with residual (cryo) liquid methane, so will appear liquid silver even on hot side.”

SpaceX has benefited from materials developed by NASA for thermal protection. The most obvious being PICA-X which is a derivative of NASA’s Phenolic Impregnated Carbon Ablator (PICA) heat shield.

Just as was done on NASA’s shuttle, Starship’s rocket engines will have to be protected during the critical period of reentry. Musk appeared to be considering the matter in a tweet on Christmas in response to questions he was asked: “No, Raptors must be shielded during atmospheric entry. Although, maybe not …” Musk said that three raptor engines would be used for the test “hopper” flights which could take place as early as 2019.

Starship is a vehicle that has undergone several design changes which prompted a question regarding how late design changes appear to be enabling the company to produce Starship more quickly. Musk said he’d address how this process works sometime in the March/April time frame. He also claimed these changes could provide a 60 percent chance that Starship could be in orbit as early as 2020.

As was noted by Tech Explorist’s Amit Malewar, the Big Falcon Rocket system would use a 219-foot (67 meters) tall rocket booster that Musk has referred to as the “Super Heavy.”

Video posted on YouTube by Scott Manley