SANTA FE, N.M. – SpaceX chief executive Elon Musk said a redesigned test vehicle for the company's next generation reusable launch system could be ready for the first flights early next year.
In a tweet early on December 24th, Musk posted a two-part photo of the initial test article, a conical section next to a cylindrical landing gear. "Stainless steel starship," he wrote.
Stainless steel vessels pic.twitter.com/rRoiEKKrYc
– Elon Musk (@elonmusk) December 24, 2018
Starship is the new name, announced by Musk last month, of the top stage or "spacecraft" of the next generation launch system, formerly known as Big Falcon Rocket, or BFR. The lower reinforcement stage is now called "super heavy".
The company has been working on a Starship test article for low-altitude flight testing at the company's launch site in southern Texas in development. This test article, nicknamed the "hopper" would have the same diameter of nine feet as the full-scale vehicle of the vehicle, but it would not be so loud.
The company submitted a request to the Federal Communications Commission on November 19, seeking an experimental license to support communications with the funnel during future flights. SpaceX said it planned a combination of low-lying, no-more than 500-foot high-altitude flights arriving at 5,000 meters from the Texas site. The company did not release a timeline for in-app flights, but said it expects to need the license for two years.
Musk and other company officials said that hopper flights will begin in late 2019. However, Musk tweeted on December 22 that he expected flights to begin early next year. "I will make a full technical presentation of the Starship after the test vehicle we are building in Texas fly, so hopefully in March / April," He wrote.
The recent series of Musk tweets has also confirmed a change in the materials that will be used to build the vehicle. The original plans, which go back to projects submitted in 2016 and 2017, required the use of carbon composite materials, which are lightweight but have high strength. Earlier this month, though, Musk said that SpaceX had switched to a "heavy metal" for use in the vehicle.
This metal, he said, is stainless steel, in particular a family of alloys called the 300 Series, known for maintaining its strength at high temperatures. Although it is heavier than carbon composites, Musk said stainless steel offered "a little better" performance from strength to weight at cryogenic temperatures., needed for the vehicle's liquid oxygen propellant tanks, and was "much better" at high temperatures. He recognized that the steel was worse than the carbon compound at room temperature.
A stainless steel surface of the vehicle, he added, would require "much smaller" thermal protection, but would also not be painted. "The skin will get too hot for the paint" he tweeted. "Stainless steel mirror finish. Maximum reflectivity. "
The test funnel will be powered by three of the company's Raptor methane / liquid oxygen engines. These engines, in which the company has been working for several years with some financial support from the US Air Force, have undergone project changes as well. "Radically redesigned Raptor ready to fire next month" he tweeted, not making such changes.
He noted that SpaceX has developed a "super-light" for the Raptor, called the SX500, designed to handle oxygen-rich hot gas at pressures up to 12,000 pounds per square inch. "Almost any metal turns into a flare under these conditions" He wrote, adding that the company's foundry to produce this alloy is "almost fully operational". This casting "allows for quick interaction in the Raptor".