Exquadrum conducted the Hybrid Upper Stage Booster (HUSB) program for NASA in order to develop a new technology called the Solid/Liquid Integrated Cycle Engine (SLICE).
The Hybrid Upper Stage Booster (HUSB) Phase II program achieved all of its objectives. The feasibility of the Solid/Liquid Integrated Cycle Engine (SLICE) propulsion concept has been decisively demonstrated. A gas-generator propellant designated as Exquadrazine 6514 was developed that is low cost, but has high performance. The propellant received a Department of Transportation (DOT) hazard classification of 1.4C, which is the safest possible rating for a formulation that is designated for use in rocket propulsion. The engine ignited readily and smoothly in all tests. Combustion was stable with smooth transients during throttling. The effort concluded with a test of three combustors operating from a single gas-generator with the exhaust exiting on a section of an aerospike nozzle.