index_html - School of Aeronautics and Astronautics - Purdue University

Liquid Rocket Engines

 

How Liquid Rocket Engines Work

Liquid rocket engines, or LREs, are one of the more popular rocket propulsion systems in use today. Most current engines utilize a bipropellant configurationin which fuel and oxidizer are stored in separate tanks. The propellants can be forced into the combustion chamber with high pressure gases (often calleda pressure-fed system) or can be drawn from the tanks using pumps. In contrast to the Solid Rocket Motor, pump-fed liquid systems can contain many components. For this reason, the LRE is generally less structurally-efficient than the SRM. However, the liquid systems usually have the advantage of higher specific impulse (energy content) and the systems can be fabricated to include throttling capabilities which SRMs generally don't posess. Finally, the LRE can be tested prior to use; the SRM must rely on rigorous manufacturing processes to insure high reliability.

Details of Various Liquid Rocket Engines

• Boeing Rocketdyne
  • MA-5A
  • RS-27A
  • RS-68
  • Space Shuttle Main Engine (SSME)
  • XRS-2200 Linear Aerospike (X-33)
• Aerojet
  • LR87-AJ-11
  • LR91-AJ-11
  • Modified Russian NK-33
  • AJ10-118K
• TRW
  • Delta TR-201
• Pratt and Whitney
  • RL10 family
  • RD-120 (with NPO Energomash)
  • RD-180 (with NPO Energomash)
• Apollo Mission
  • F-1
  • J-2
  • H-1

Comparison Tables of Various Engines

Disposable first stage engines. All values at sea level unless otherwise noted.

Make	Model	Thrust	Isp (s)	Fuels	Weight	Applications
Rocketdyne	MA-5A	490,000	265 s	LOX/RP-1	4371 lb	Atlas II, IIA, IIAS
	RS-27A	200,000 lb	255 s	LOX/RP-1	2528 lb	Delta II, III
	RS-68	650,000 lb	365 s	LOX/LH2	14560 lb	Delta IV EELV
	F-1	1,522,000 lb	265 s	LOX/RP-1	18,616 lb	Saturn V
Aerojet	LR87-AJ-11	552,600 lb (vac)	304 s (vac)	LOX/RP and others	4780 lb	Titan IV
P&W/NPO-EM	RD-180	868,400 lb	311 s	LOX/RP	11675 lb	Atlas IIAR

 

Disposable second/upper stage engines. Quantities in vacuum.

Make	Model	Thrust	Isp (s)	Fuels	Weight	Applications
Aerojet	LR91-AJ-11	105,000 lb	316 s	LOX/RP and others	1314 lb	Titan family
	AJ10-118K	9753 lb	320.5 s	Aerozine 50/N2O4 (hypergolic)	275 lb	Delta II, III, IV EELV
TRW	TR-201	9,900 lb	303 s	N2O4 and UDMH/N2H4 (hypergolic)	300 lbm	Delta I (???)
Pratt & Whitney	RL10A-4	20800 lb	449 s	LOX/LH2	370 lbm	Centaur
	RD-120	187,400 lb	350 s	LOX/RP	2480 lbm	Zenit
Rocketdyne	J-2	230,000 lb	425 s	LOX/LH2	3.480 lb	Apollo upper stages

 

Reusable first stage engines. Quantities at sea level unless otherwise noted.

Make	Model	Thrust	Isp (s)	Fuels	Weight	Applications
Rocketdyne	SSME Phase II	418,130 lb	454.4 s (vac)	LOX/LH2	6,990 lb	Shuttle main engine
	XRS-2200	204,420 lb	339 s	LOX/LH2	n/a (integrated)	X-33 main engine
Aerojet/Kuznetsov	AJ26-NK33A	339,000 lb	297	LO2/HC	2725 lb	Kistler RLV
Pratt & Whitney	RL10A-5	14,560 lb (vac)	368 s (vac)	LOX/LH2	316 lb	DC-X and -XA

Solid Rockets : Satellite Systems