WASHINGTON — SpaceX is changing the approach for separating the 2 stages of its Starship vehicle to extend payload performance before its next test flight, Elon Musk said June 24.
In an internet discussion with Bloomberg journalist Ashlee Vance on Twitter, the social media company Musk owns, he said that SpaceX had recently decided to change to a “hot-staging” approach where the Starship upper stage will ignite its engines while still attached to the Super Heavy booster.
“We made type of a late-breaking change that’s really quite significant to the way in which that stage separation works,” Musk said, describing the switch to hot staging. “There’s a meaningful payload-to-orbit advantage with hot-staging that’s conservatively a few 10% increase.”
Hot-staging, which has been used on Russian launch vehicles for a long time, involves igniting the engines on one stage while still attached to its lower stage. Musk said that, for Starship, a lot of the 33 Raptor engines on the Super Heavy booster could be turned off, but a couple of still firing, when the engines on the Starship upper stage are ignited. Doing so, he said, avoids the lack of thrust during traditional stage separation, where the lower stage shuts down first.
Doing so requires some modifications to the Super Heavy booster. Musk said SpaceX is working on an extension to the highest of the booster “that is nearly all vents” to permit the exhaust from the upper stage to flee while still attached to the booster. SpaceX can even add shielding to the highest of the booster to guard it from the exhaust.
“That is essentially the most dangerous thing, I believe, for the subsequent flight,” he said of the brand new stage separation technique.
Besides the change in stage separation, Musk said SpaceX made a “tremendous number” of other changes to the vehicle, “well over a thousand.” He didn’t go into details in regards to the changes, but did note the corporate was continuing work to upgrade the launch pad to avoid the damage brought on by the primary Starship launch April 20, corresponding to a “steel sandwich” water deluge system. “We’re actually going for overkill on the steel sandwich and the concrete, so that ought to leave the bottom of the pad in a lot better shape than the last time.”
SpaceX also made improvements to the Raptor engines, with Musk describing the vehicle launching in April as using a “hodgepodge” of engines built over time. The Raptors on the brand new vehicles include changes to the recent gas manifold within the engine to scale back fuel leakage.
Those changes, he said, gave him more confidence within the success of the subsequent launch. “I believe the probability this next flight working, attending to orbit, is way higher than the last one. Possibly it’s like 60%.” In an internet conversation in late April, he estimated a “higher than 50% probability” of success on the subsequent launch.
Musk didn’t commit to a selected launch date. “A variety of variables here which can be outside of our control,” he said, an apparent reference to the Federal Aviation Administration launch licensing process. “We expect, probably, the launch pad upgrades, and the booster and ship, are ready in about six weeks.” Musk, in that April conversation, said he expected to be able to fly “in a pair months.”
Earlier within the conversation, Musk declined to comment on recent rumors that SpaceX was considering spinning out its Starlink satellite broadband business and conducting an initial public offering (IPO) of stock in it. Fox Business reported June 21 that SpaceX investors anticipated a spinout and IPO of Starlink this yr in order that Musk could raise money for other ventures, like Twitter.
Musk, asked about any plans for a Starlink IPO, declined to comment. “It could not be legal for me to take a position a few Starlink IPO,” he claimed. “I believe it’s against regulations to speak with any sorts of specifics a few future public offering.”
Musk has previously played down any discuss spinning out Starlink and taking it public. He said in 2020 he was “excited about that zero” to be able to concentrate on making the broadband service a technical and financial success.
In an internal company meeting in June 2022, Musk said he didn’t know when SpaceX would take Starlink public, but estimated it will be no less than three to 4 years.
