Rocket Propulsion Elements, 9th Edition

CHAPTER 16HYBRID PROPELLANTS ROCKET PROPULSION¹

Rocket propulsion bipropellant concepts in which one component propellant is stored in the liquid phase and the other as a solid are called hybrid propulsion systems or hybrid rocket engines (there is no universally accepted designation). See Fig. 1–6. Hybrid propulsion is of considerable interest to commercial rocket endeavors primarily for space applications. The main advantages of hybrids are: (1) more safety and ruggedness than conventional chemical propulsion systems—vehicles using hybrid propellants may survive unharmed effects of bullet impacts, fires under the vehicle, inadvertent droppings, and of explosions from adjacent munitions or other rockets; (2) start–stop–restart capabilities; (3) relative simplicity compared to liquids which may translate into low overall system cost; (4) higher specific impulse than solid rocket motors and higher density‐specific impulse (see Eq. 7–3) than many common liquid bipropellant engines; and (5) capability to smoothly change thrust on demand over wide ranges. Even though hybrids have many unique features of their own, they do benefit from developments in liquid and solid rockets. Early hybrid motors were produced for target drones and for one small tactical missile. Experimental hybrid motors in sizes between 2 and 250,000 lbf thrust have been developed and ground tested. A few of medium‐sized and small hybrid motors have flown in experimental vehicles. However, as of 2015 none of the ...