Starship Belly Flop Maneuver
The “belly flop” is the unusual way SpaceX’s Starship spacecraft slows itself for landing: instead of dropping straight down, it falls on its side like a skydiver, then flips upright at the last second for a powered touchdown.
Quick facts
- Also called: the skydiver or aerodynamic-descent maneuver
- Descent attitude: belly-first, falling roughly flat (horizontal)
- Flip altitude: about 500-550 m (1,640-1,800 ft) above the ground
- Control surfaces: four large body flaps (two forward, two aft)
- Engine fuel for landing: drawn from small dedicated “header tanks”
- First test: SN8, 9 Dec 2020, from 12.5 km
- First success: SN15, 5 May 2021, from 10 km
What it is and how it works
Most rockets land tail-down, falling nose-up the whole way. Starship does something different. After its engines shut off at the top of its arc (apogee, the highest point of the flight), the vehicle tips onto its side and falls flat, belly toward the ground.
The reason is drag, the resistance the air pushes back with as an object moves through it. A skydiver who spreads into a wide “X” catches far more air and falls more slowly than one diving headfirst. Starship’s long body does the same thing: lying flat, it presents a huge surface to the rushing air and sheds most of its speed for free, without burning any fuel.
Four flaps steer the fall. These are aerodynamic control surfaces, hinged panels that catch the air, not wings that create lift to glide. Two sit near the nose and two near the tail, and each moves on its own. By extending or folding them, the vehicle adds or removes drag on different parts of its body and stays balanced and on target.
Then comes the dramatic part. At about 500-550 m up, Starship relights its Raptor engines and swings their nozzles hard to one side (called gimbaling) to rotate from horizontal to vertical, the “flip.” A brief landing burn follows, and the ship settles down tail-first.
Why it matters
Doing most of the braking with air rather than engines saves an enormous amount of fuel. The landing needs only about 250 m/s of delta-v (the measure of how much a burn changes a vehicle’s speed), compared with roughly 620 m/s for a high-altitude flip. Every kilogram of fuel a vehicle does not have to carry for landing is a kilogram it can spend on cargo, or on the fuel needed to return from Mars.
The approach is also gentler. Starship comes in around 90 m/s and about 2.5 g (a measure of force, where 1 g equals normal gravity at Earth’s surface), versus roughly 310 m/s and 5 g for a Falcon 9 booster’s straight-down landing. That eases the load on the airframe. Because air gets thinner with altitude, the technique works on both Earth and, in lighter form, Mars, making it a genuinely new kind of orbital-class landing.
Notable test flights
SpaceX proved the maneuver one prototype at a time, and the early ones were rough:
- SN8 (9 Dec 2020, 12.5 km): first belly flop and flip; low methane pressure in a header tank starved an engine, causing a hard impact and explosion.
- SN9 (2 Feb 2021, 10 km): an engine failed to relight for the flip, and the vehicle could not right itself.
- SN10 (3 Mar 2021, 10 km): first to land after the flip, but a methane fire destroyed it about ten minutes later.
- SN11 (30 Mar 2021, 10 km): a methane fire damaged its avionics; it exploded as the engines reignited.
- SN15 (5 May 2021, 10 km): the breakthrough, completing the full belly flop, flip, and landing intact.
The flip is unforgiving because it has to happen low and fast, leaving almost no margin if an engine or fuel feed misbehaves. To guarantee a clean supply during that violent move, the landing engines draw from small dedicated header tanks, one in the nose for liquid oxygen and one lower down. Even as SpaceX later moved to catching its booster with the launch tower’s “chopstick” arms, the ship still uses the belly-flop-and-flip for atmospheric descent and ocean splashdown.
