Aerospike engines will use 25–30% less fuel at low altitudes. Rocketdyne did a lot of tests in the 1960s on this technology. NASA tried to make aerospikes work for the X-33 program in the 1990s.
Three XRS-2200 engines were built during the X-33 program. The XRS-2200 produced 204,420 lbf (909,300 N) thrust with an Isp of 339 seconds at sea level and 266,230 lbf (1,184,300 N) thrust with an Isp of 436.5 seconds in a vacuum.
Rocketstar LLC launched a small rocket in 2016.
It's official! Next stop: Space!
Engine: Proprietary aerospike
Planned altitude: 50 Miles
Launch location: Barge launch, off Cape Canaveral#CarpeAstra #aerospike #cowbell #rocketlaunch #space #rocketstar pic.twitter.com/qcuIMKmwFd
— RocketStar (@RocketStarSpace) January 18, 2019
— RocketStar (@RocketStarSpace) April 17, 2016