Aerospikes are rocket engines that don't make use of common bell-nozzles. They can maintain a high efficiency at any altitude, as their expansion ratio is constant over altitudes. The design, however, leads to higher complexity and heat - reasons why they are not currently used in any rocket on the market.

Aerospike engines are rocket engines that don't make use of common bell-nozzles. They can maintain a high efficiency at any altitude, as their expansion ratio is constant over altitudes.

Their design leads to higher complexity, more surface area that has to be cooled and more heat. They are not currently used in any rocket on the market.

For questions regarding the rocket engines, use the tag, for questions about nozzles in general, use the tag.