Aerospike Engines: Why aren't we using them now? [video]
Summary:<p>1. An aerospike engine tries to overcome a problem in the traditional bell-shaped nozzles: traditional nozzle shape and size can only be optimized for one specific pressure (e.g. either sea level or a higher altitude). At all other altitudes, it is inefficient.<p>2. An areospike is kind of an inverted bell -- there is a spike in the middle and the rocket exhaust flows around it. This forms a sort of virtual bell nozzle (the inner wall is the spike&#x27;s surface, the outer wall is the air itself). As the atmospheric pressure varies, the virtual nozzle shape adjusts too. This makes the areospike efficient at all altitudes (but not as efficient as a bell nozzle at it&#x27;s most optimal).<p>3. Ideal for single-stage-to-orbit<p>4. Work stopped (author claims) because in the space industry, tried and tested is favored. And apparently, fuel is not such a large component of the cost of a rocket launch.