aerospikes

Aerospikes are a type of rocket engine nozzle that uses the surrounding atmosphere as part of its structure.

Unlike conventional bell-shaped nozzles optimized for a single altitude, an aerospike maintains efficiency across a range of atmospheric pressures—from sea level to near-vacuum.

The design directs exhaust along a central spike or wedge, with ambient air pressure shaping the outer boundary of the exhaust plume.

Though theoretically superior for single-stage-to-orbit vehicles, aerospikes have seen limited practical use due to engineering challenges with cooling and weight.