SpaceX is changing the separation of Starship stages before the next launch

WASHINGTON — SpaceX is changing the approach to separating the two stages of its Starship vehicle to increase payload performance ahead of its next test flight, Elon Musk said June 24.

In an online discussion With Bloomberg journalist Ashlee Vance on Twitter, the social media company Musk owns, he said that SpaceX recently decided to switch to a “hot staging” approach, in which the spacecraft’s upper stage fires its engines , while still connected to the Super Heavy booster.

“We made kind of a game-changing change that’s really significant to the way phase separation works,” Musk said of the move to hot staging. “With hot staging, there is a significant payload-to-orbit advantage that’s conservatively around a 10% increase.”

Hot staging, used on Russian launch vehicles for decades, fires the engines on one stage while still attached to the lower stage. Musk said that for Starship, most of the Super Heavy booster’s 33 Raptor engines would shut down, but some were still firing when the Starship upper stage engines ignited. This, he said, avoids the thrust loss associated with traditional stage separation, where the lower stage shuts down first.

This requires some modifications to the Super Heavy booster. Musk said SpaceX is working on an extension to the top of the booster “that includes almost all of the vents” to allow exhaust gases to escape from the upper stage while still attached to the booster. SpaceX will also add a shield to the top of the booster to protect it from the exhaust fumes.

“That’s the riskiest thing for the next flight in my opinion,” he said of the new staging technique.

In addition to the stage separation change, Musk said SpaceX made a “tremendous number” of other changes to the vehicle, “well over a thousand.” He didn’t elaborate on the changes, but noted that the company is still working to upgrade the launch pad to avoid damage caused by Starship’s first launch on April 20, such as a “steel sandwich.” -Water flooding system. “We’re actually going too far with the steel sandwich construction and concrete, so the base of the pad should be left in much better shape than last time.”

SpaceX also made improvements to the Raptor engines, with Musk describing that the vehicle, due out in April, utilized a “hodgepodge” of engines built over time. Changes were made to the hot gas manifold in the engine on the new-vehicle Raptors to reduce fuel leaks.

Those changes, he said, would have given him more confidence in the success of the next launch. “I think the probability that the next flight will work and get into orbit is much higher than the last one. Maybe it’s 60%.” In an online conversation at the end of April, he estimated the chance of success at the next launch to be “more than 50%”.

Musk has not set a specific launch date. “There are a lot of variables here that are out of our control,” he said, an apparent reference to the Federal Aviation Administration’s takeoff licensing process. “We anticipate that the launch pad and launch vehicle and ship upgrades will probably be ready in about six weeks.” In that call in April, Musk said he expects to be ready to fly “in a couple of months.”

At the start of the call, Musk declined to comment on recent rumors that SpaceX was considering spinning off its Starlink satellite broadband business and conducting an initial public offering (IPO) of the shares. Fox Business reported June 21 that SpaceX investors were expecting Starlink to spin out and go public this year so Musk could raise money for other ventures like Twitter.

When asked about plans for a Starlink IPO, Musk declined to comment. “It would not be legal for me to speculate on a Starlink IPO,” he claimed. “I think it’s against the rules to give any details about a future IPO.”

Musk has previously downplayed any talks of spinning off and listing Starlink. He said in 2020 he was “thinking about that zero” to focus on making the broadband service a technical and financial success.

In an internal company meeting in June 2022, Musk said he doesn’t know when SpaceX will list Starlink, but estimates it will take at least three to four years.

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