>>11763404They're a good jack-of-all-trades engine. But they're not really "great" at any specific altitude. They're just okay. As such they are good for SSTOs, but remember that SSTOs are horribly impractical.
>Delta Clipper was a vertical landing/takeoff SSTO>Mass of 36 Metric tons when dry, held 434 tons of propellant>Only put FOUR tons of payload into LEO alone!However
>Stack a Delta Clipper onto a stage with the exact same propellant mass/dry mass>Put landing legs on the first stage, make it able to land as well>100% reusable vehicle>Can put 20 tons into LEO!SSTOs are cool but they are impractical given that Two-Stage-Reusable vehicles can just put a payload several times larger into orbit, while only increasing the vehicle size by a factor of at most two or three.
As such, there's no need for an aerospace engine, as you do not have to optimize your impulse for all altitudes. You can just put a vacuum engine on the second stage, and a sea level one on the first.
Technical challenges aside, aerospikes just are impractical.
