Update: Raptor roars on SpaceX’s Texas test stand
SpaceX’s next-generation rocket engine, dubbed Raptor, was briefly fired on a test stand. The test comes just days after company CEO and Founder Elon Musk revealed photos of the engine on Twitter.
Raptor is designed to consume liquid methane and liquid oxygen and will be used to power SpaceX’s Starship spacecraft and Super Heavy rocket.
“First firing of Starship Raptor flight engine!” Musk tweeted the evening of Feb. 3, 2019. “So proud of great work by [the SpaceX] team!”
— Elon Musk (@elonmusk) February 4, 2019
The test, which lasted for only several seconds, took place at the company’s test facility in McGregor, Texas. Musk said the engine is initially being designed to produce 200 metric tons of thrust and will be common across both the 180-foot (55-meter) tall Starship and 207-foot (63-meter) tall Super Heavy rocket, which is expected to have seven and 31 Raptor engines, respectively.
The commonality was done to ensure a faster development time for the vehicles. Once operational, vacuum-optimized and sea-level-optimized versions of Raptor will be made with greater efficiencies, according to Musk.
Update Feb. 4, 2019: According to SpaceX’s Instagram account, the two-second test fire produced about 116 metric tons of force, which the company said was the highest thrust ever from a SpaceX engine—it was only at about 60 percent power.
Raptor is a full-flow staged combustion engine, meaning it uses both oxidizer-rich and fuel-rich preburners and allows a both propellants through the turbines before going through a combustion chamber.
It allows turbines to run at lower temperatures and is easier on the engine overall, potentially allowing for a longer and more reliable life.
To date, three full-flow staged combustion engines have ever made it to test stands, the Soviet-designed RD-270 in the 1960s, an Aerojet Rocketdyne demonstration project in the 2000s and Raptor. None have seen actual flight, though.
Musk said on Twitter that the engine will be ignited using metholox torch igniters, which he described as “heavy duty spark plugs.” Those ignite dual blow torches that ignite the preburners and main chamber, he said.
A prototype of the upper stage of SpaceX’s Mars rocket, called Starship, is being built in south Texas. This “hopper” will use three Raptor engines to fly to various low altitudes for early tests of the vehicle.
During construction, it was revealed that the ship is now expected to be made out of stainless steel, rather than advanced carbon fiber. Musk said this allows for a simpler and lower-cost design and counter-intuitively, a lower-mass vehicle since stainless steel can withstand much higher temperatures.
Additionally, Musk has been teasing a regeneratively-cooled heat shield that sweats liquid methane through tiny holes in the bottom for added cooling. If done successfully, it would be another words first as all spacecraft heat shields to date have been either ablative, like on SpaceX’s Dragon capsule and NASA’s Orion crew vehicle, or absorptive, like the tiles used on the space shuttles.
The first orbital test flights of Starship could come as soon as 2020, however, even Musk has admitted that is a highly-ambitious schedule. Additionally, a flight around the Moon with Japanese billionaire Yusaku Maezawa and eight artists is planned as early as 2023.
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a blog about the International Space Station, called Orbital Velocity.