SPACE SHUTTLE MAIN ENGINE

V
X
Q A B
M T
P
S
I L W
O R
N
H
U
K


G C Z
S T
H
D

L L


E J
A V E
G
B
U
F H

*NOT TO SCALE
LOW PRESSURE OXYGEN LOW PRESSURE FUEL
TURBOPUMP ELEVATION TURBOPUMP ELEVATION

Denotes Fuel (Liquid Hydrogen) *Note- This color scheme is primarily MAJOR COMPONENT ISOMETRIC PROPELLANT FLOW SCHEMATIC
used to help distinguish the two (SIMPLIFIED)
main systems more clearly. It is not
Denotes Oxidizer (Liquid Oxygen) a technical representation.

LOW-PRESSURE HIGH-PRESSURE FUEL PREBURNER FUEL HGM COOLANT CHAMBER

The Space Shuttle Main Engine (SSME) was designed for 55 missions. The engines were generally referred to as the center (engine 1), left (engine 2), and A FUEL TURBOPUMP
H OXIDIZER
N S PREBURNER
W Y COOLANT
OXIDIZER VALVE DUCT
TURBOPUMP VALVE
right (engine 3). The SSMEs were 14 feet long and 7.5 feet in diameter at the nozzle exit. Each nozzle had an area ratio of 77.5:1. Each SSME weighed
LPFTP TURBINE PNEUMATIC OPB LOX MAIN OXIDIZER
approximately 7,000 pounds. B LOW-PRESSURE I O CONTROL
T OXIDIZER X SUPPLY DUCT Z
OXIDIZER TUR- DRIVE DUCT PRE- VALVE
BOPUMP ASSEMBLY BURNER
The SSME utilized four turbopumps to boost the pressure of its cryogenic propellants for preburner and main combustion chamber injection. The design LPOTP TURBINE LOX BLEED
C LOW-PRESSURE J P HIGH PRESSURE U
incorporated a controller with a health management system. The five main control valves operated under hydraulic pressure and had redundant pneumatic OXIDIZER DUCT DRIVE DUCT LOX DUCT VALVE
control for failure scenarios. Additionally, the engine featured a passive on-engine POGO oscillation suppression system attached to the low-pressure oxidizer
duct (LPOD) to damp and prevent coupling of vehicle-to-engine low-cycle pressure oscillations. LOW-PRESSURE K LPFTP TURBINE HIGH PRESSURE V FUEL
D Q BLEED
FUEL DUCT DISCHARGE DUCT FUEL DUCT
VALVE
Throughout its history, the SSME incorporated many design improvements. Most large changes were incorporated in block upgrades. Many limitations of the MAIN COMBUSTION HOT-GAS OXIDIZER PRE-
first manned orbital flight (FMOF) engines were addressed by the Phase I design, which first flew on STS-6. Post-Challenger Return-to-Flight (STS-26R) E L R BURNER OXI-
CHAMBER MANIFOLD
brought the first flight of Phase II, which included modifications to the turbopumps, main combustion chamber, and avionics. The Block I configuration which DIZER VALVE

followed incorporated a new high-pressure oxygen turbopump, an improved powerhead, and a new heat exchanger. The Block I configuration was first flown MAIN FUEL
F VALVE
M CONTROLLER
on STS-70. Block IIA was first flown on STS-89. It incorporated a large-throat main combustion chamber reducing system internal pressures and
temperatures. The last block upgrade was Block II, which added a new high-pressure fuel turbopump. Block II first flew on STS-104. The cumulative effects HIGH-PRESSURE
of these modifications were increased safety and reduced maintenance costs between flights. Predicted reliability improved by a factor of four over the life of G FUEL TURBOPUMP
the program, and maintenance on the Block II engine was 57% less than on the Phase II engines.

SSME NO. 1 EXTERNAL TANK

CONNECTION TO SHUTTLE
MAIN ENGINES

HORIZONTAL
ENGINE REMOVAL

LIQUID HYDROGEN TANK

SSME NO. 3 SSME NO. 2
(FUEL)

SSME ARRANGEMENT
(FROM INSIDE AFT SECTION LIQUID OXYGEN
LOOKING OUT) TANK (OXIDIZER)