Design and evaluation of aerospike nozzles for an upper-stage application

Aerospike nozzles are often studied because of their intrinsic self-adaptation behavior to the atmospheric pressure. Another unique feature of aerospike nozzles is their mass-and volume-efficient integration with the underlying vehicle. This latter aspect, if fully exploited, could be of interest for both lower stages operating in the atmosphere and for upper stages operating in vacuum. In this paper, a numerical analysis is carried out of the possible advantages of using an aerospike engine under specific volume constraints of a reference upper-stage configuration, discussing basic aspects of aerospike and internal expansion design, clustering, and plug truncation length. The results of the present preliminary analysis show the extent of possible performance advantages of aerospikes in terms of the specific impulse delivered for a given available volume for the nozzle with respect to a conventional bell configuration.