In Brief
In a recent AMA on Reddit, Musk was asked about the Raptor prototype engine. He claims that it will be a piece of cake to scale up, but the difficulties will lie in ensuring safety and preventing unscheduled disassembly.

The SpaceX Raptor

In 2016, the United States Air Force contracted SpaceX to begin designing and developing the Raptor prototype upper-stage engine, a bipropellant rocket engine. This design is based on SpaceX’s reusable, methane-powered Raptor engine, which is used in the upper stages of both the Falcon 9 and Falcon Heavy. On Saturday, in an ask me anything (AMA) on Reddit, Elon Musk got candid online and answered some questions about the prototype and other Raptor design objectives.

One person asked, “Could you update us on the status of scaling up the Raptor prototype to the final size? The sub-scale Raptor prototype has a (speculated) thrust of about ~100 tons-force currently, and will be scaled up to ~170 tons-force according to your IAC/2017 design. Can you tell us more about the current status and expected (best-case) timeline of this scale-up effort?”

Musk gave a thorough response: “Thrust scaling is the easy part. Very simple to scale the [developed] Raptor to 170 tons.  The flight engine design is much lighter and tighter, and is extremely focused on reliability. The objective is to meet or exceed passenger airline levels of safety.”

“If our engine is even close to a jet engine in reliability, has a flak shield to protect against a rapid unscheduled disassembly and we have more engines than the typical two of most airliners, then exceeding airline safety should be possible,” he continued. “That will be especially important for point to point journeys on Earth. The advantage of getting somewhere in 30 mins by rocket instead of 15 hours by plane will be negatively affected if ‘but also, you might die’ is on the ticket.”

Rocket Travel

SpaceX’s reusable rockets have paved the way for cost-effective, environmentally conscious, and efficient space travel. The Raptor prototype engine is, as Musk explained in the AMA, currently on track to scale up for use in the aerospace company’s rockets. But Musk’s response, alongside his recent presentation at the International Aeronautical Congress (IAC), have added to the discussion. These updates not only confirmed that SpaceX will be able to scale up the engine, but asserted that the design will focus on human safety—all the while alluding to the possibility of casual travel by rocket.

So, is there the possibility, in the near future, that SpaceX will be marketing their rockets for casual, commercial use? It is possible. But currently, it seems SpaceX still has work to do in completing the scaling of the engine and improving the safety for riders within these vehicles. If the comments poking fun at Musk’s careful wording of potential failure are to be taken to heart, SpaceX and Musk’s priorities—the dreaded “unscheduled disassembly”—are in the right place.