Elon Musk Reveals Simple Reason Why SpaceX Starship Uses 2 Stages Instead Of Just One: 'No Problem On Mars...'

SpaceX CEO Elon Musk provided insight on Saturday into why the Starship launch vehicle, designed for future Mars missions, features a two-stage design rather than a single stage.

What Happened: The Starship comprises SpaceX’s Super Heavy rocket and the spacecraft, aiming to transport people and cargo to orbit, the Moon, and Mars. 

Musk responded to a user on X who shared an edited photo removing the Super Heavy booster, leaving only the spacecraft. 

The user jokingly suggested a single-stage-to-orbit (SSTO) design, to which Musk replied, “Yeah, wrong planet for SSTO. No problem on Mars with ~37% Earth gravity.” 

In simple terms, Musk explained that an SSTO design would be less practical for Earth due to its higher gravity. However, he pointed out that on Mars, with its lower gravity, an SSTO design could be feasible.

SSTO refers to a spacecraft that reaches orbit using only one stage.

Notably, no SSTO vehicles have been flown from Earth to orbit thus far.

Why It Matters: Mars has a lower surface gravity compared to Earth, approximately 37% of Earth’s gravity. This means that, theoretically, it requires less energy (thrust) to escape Mars’ gravitational pull. A vehicle designed for Mars might have an easier time achieving SSTO compared to a similar design intended for Earth.

The Starship’s second liftoff on Nov. 18 saw successful stage separation, but the booster experienced an explosion shortly afterward. 

The spacecraft lost contact with SpaceX after reaching an altitude of nearly 150 kilometers, failing to complete the test launch’s goal of a round-trip flight to space with a splashdown in the Pacific Ocean. 

Despite this setback, Flight 3 appears to be on the horizon.

"Starship Flight 3 hardware should be ready to fly in 3 to 4 weeks," Musk wrote on X a day after the second Starship launch.

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