Solid Rocket Propulsion

How Solid Rocket Motors Work

Conceptually, solid rocket motors (or SRMs) are simple devices with very few moving parts. An electrical signal is sent to the igniter which creates hot gases which ignite the main propellant grain (see image below). The propellant contains both fuel and oxidizer; therefore these devices can operate in the vaccuum of space. Thrust is developed as the high thermal energy of the combustion gases is converted to kinetic energy in the exhaust. The simplicity of SRMs make them an attractive choice for many rocket propulsion applications. Because there are few structural components, the SRM is efficient in that the vast majority of its weight is actually usable propellant. SRMs can be ignited in a moments notice and don't require tanking of liquids prior to operation. On the downside, their efficiency (specific impulse) is generally lower than liquid systems, and they cannot be readily throttled. Once ignited, the motor will burn to extinction unless special provisions are included to terminate thrust during the middle of a firing.

Details of Various Solid Rocket Motors

• Cordant Thiokol
  • Shuttle Reusable Solid Rocket Motor
  • STAR family
  • CASTOR family
• Pratt & Whitney CSD
  • Orbus family
• Alliant Techsystems
  • GEM strap-on booster
  • Orion booster
  • Sidewinder heatseeking missile motor
  • AMRAAM radar missile motor
• Aerotech
  • Composite Propellant high-power model rocket motors
• Estes
  • Black Powder model rocket motors

Comparison Tables of Various Engines

Strap-on Boosters

Make	Model	Thrust	Weight	Propellant	Total Impulse	Burn time	Applications
Thiokol	SRSM	3,300,000 lb	1,300,000 lb	ammonium perchlorate/aluminum	Information not available	75 s	Shuttle SRB
	Castor IVA	Information not available	Information not available	Information not available	Information not available	Information not available	Delta I, Atlas strap-on
Alliant	GEM	112,241 lb	28,592 lb	88% HTPB	7,090,000 lb-s	55 s	Delta II strap-on

 

Stand-alone solid rocket boosters

Make	Model	Thrust	Weight	Propellant	Total impulse	Burn time	Application
Thiokol	Castor 120	435,000 lb	116,275 lb	HTPB	29,900,000 lb-s	81 s	Athena I, II first stage, Athena II second stage
Alliant	Orion 50S AL	130,500 lb	29,581 lb	HTPB	7,893,000 lb-s	72.4 s	Pegasus air-launch space booster

 

Upper stage engines

Make	Model	Thrust	Weight	Propellant	total impulse	Burn time	Applications
Thiokol	STAR 48A	17,300 lb	5674 lb	Ap / Al	1,528,409 lb-s	88 s	STS Payload Assist Module
Pratt	Orbus 6	23,800 lb	6515 lb	Information not available	1,738,000 lb-s	101 s	STS Inertial Upper Stage
	Orbus 21S	59,460 lb	22,703 lb	Information not available	6,190,000 lb-s	138 s	INTELSAT-VI perigee kick

 

Tactical missile engines

Make	Model	Weight	Propellant	Operating temps
Alliant	Sidewinder	99 lb	RS HTPB	-65F to 160F
	AMRAAM	Information not available	156 lb	-65F to 145F

 

Model rocket engines

Make	Model	Propellant	Thrust	Impulse	Weight	Propellant Weight	Burn time
Aerotech	F50-4T disposable	Blue Thunder composite	50 N	80 N-s	83 g	38.3 g	1.6 s
	H180W reloadable	White Lightning composite	180 N	230 N-s	263.6 g	123 g	1.27 s
Estes	1/2A6-2	Black powder	6 N	1.25 N-s	Information not available	2.6 g	.21 s
	D12-7		12 N	17 N-s	Information not available	10.8 g	1.42 s

Information Page : Liquids Engines