SpaceX Starship Never Stops Thrusting With Hot Staging

Elon Musk told Ashlee Vance on a Twitter Space, that SpaceX had recently decided to switch to a “hot-staging” approach where the Starship upper stage will ignite its engines while still attached to the Super Heavy booster.

Musk said, describing the switch to hot staging. “There’s a meaningful payload-to-orbit advantage with hot-staging that is conservatively about a 10% increase.” This will be done on the next Super Heavy Starship launch. This was discussed 36 minutes into the Twitter Space.

Hot-staging has been used on Russian launch vehicles for decades. The engines of one stage are ignited while still attached to its lower stage. Musk said that, for Starship, most of the 33 Raptor engines on the Super Heavy booster would be turned off, but a few still firing, when the engines on the Starship upper stage are ignited. Doing so, he said, avoids the loss 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 top of the booster “that is almost all vents” to allow the exhaust from the upper stage to escape while still attached to the booster. SpaceX will also add shielding to the top of the booster to protect it from the exhaust.

“This is the most risky thing, I think, for the next flight,” he said of the 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.”

SpaceX was continuing work to upgrade the launch pad to avoid the damage caused by the first Starship launch April 20, such as a “steel sandwich” water deluge system. “We’re actually going for overkill on the steel sandwich and the concrete, so that should leave the base of the pad in much better shape than the last time.”

Well, things ended a bit abruptly. 😂 But here’s the recording of the Space Spaces with @elonmusk. Many thanks to him for the time in the middle of a party. And here’s my new book on the subject. https://t.co/W3HGEAdpaLhttps://t.co/w5KJS5lWD1

— Ashlee Vance (@ashleevance) June 24, 2023

SpaceX does not spend any time thinking about competition. They only focus on improving their own systems.

If SpaceX luck holds they will launch 80% of the mass of the world’s payloads to orbit this year.