What, if any, would be the most correct term for the aerodynamic flight control surfaces of SpaceX's Starship? SpaceX's Starship uses a unique flight control scheme during descent that I have not seen anywhere except with skydivers: it falls straight down belly-first using four aerodynamic control surfaces at the nose and the bottom to induce drag and thus provide pitch, roll, and yaw control, somewhat like a skydiver uses their four limbs.
 [Time lapse by @asy on Twitter, original source footage by LabPadre.]
This is a pre-flight actuation test of the aerodynamic control surfaces. The Starship is in its launch attitude, i.e. tail-down / engines down. On descent, it would be falling belly-down, where the belly is the side facing away from the camera, i.e. if the vehicle were falling right now, we would be looking at it from the top.
These aerodynamic control surfaces have been called lots of names by the spaceflight community: fins, flaps, wings, flings, wing-dings, flippety-flappety-bits (yes, really). Tim Dodd, the Everyday Astronaut, sometimes jokingly calls them Elonerons. SpaceX themselves only name them once on the Starship website, where they use the term flaps. Elon Musk uses both flaps and body flaps in tweets.
They are, however, different from many of the concepts mentioned above, in that they act perpendicular to the airflow. The closest analogy I can think of, other than a skydiver's limbs, is how the Northrop Grumman B-2 Spirit uses differential speed brakes for yaw control instead of a rudder.
Given that we have so many names for so many different types of control surfaces (e.g. flap, slat, spoiler, aileron, elevator, rudder, speed brake, horizontal and vertical stabilizer) as well as combinations of them (spoileron, flaperon, stabilator (all-moving tail), &quot;ruddervator&quot; (V-tail)), etc., there must be some term we can apply to these?
What I am looking for is a term that concisely conveys what these control surfaces do, in much the same way as everybody knows what an &quot;aileron&quot; or an &quot;elevator&quot; does. Or, alternatively, an answer could be that such a term does not exist.
As far as I know, the only other example of this flight profile in aviation is post-stall maneuvering, especially for flat spin recovery. For planes, control in these flight regimes is mainly accomplished by thrust vectoring and canard/stabilator actuation. The Starship flaps don’t match these.
Another close sibling of this flight profile is the Shuttle reentry. The Shuttle used a body flap as well as conventional Delta-wing control surfaces in combination with RCS to maintain a specific, high AoA during hypersonic reentry, then transitioned to gliding for approach and landing. The Shuttle body flap (under the engines) has the closest resemblance to the Starship flaps out of any space vehicle I know. It has a much smaller actuation range, though.
Of course, the control surface naming depends on how you define the vehicle frame; with thrust direction-forward, the flaps are variable-dihedral. With velocity direction-forward, the flaps are variable-AoA with a wide actuation range.
The noun I would go with would be variable-drag flaps. Spoilers aren’t correct; there isn’t another airfoil to spoil. Airbrakes usually don’t contribute to attitude control.