eAc (Environmental Aeroscience Corp) developed and fired t' first solid propellant Aerospike motor in 2003. Aerospike nozzles are designed t' be altitude compensatin' and self adjust t' expansion ratio makin' them extremely useful for ground-launched soundin' rockets. Blimey! This feature is specifically useful for long burn hybrid rocket applications. Ahoy! Several design verification tests firings usin' short burn solid propellants, with t' goal o' applyin' t' technology t' t' long burn Hybrid motors.