Encyclopedia Astronautica
GEM 46


Solid propellant rocket stage. Loaded/empty mass 19,327/2,282 kg. Thrust 628.31 kN. Vacuum specific impulse 278 seconds. Nine 1168-mm (46 in.) diameter Alliant graphite epoxy motors (GEM LDXLs) (strap-on solid rocket motors - SSRMs) augment the first-stage performance of the Delta III and were a direct evolution from the GEMs used on Delta II.

Three ground-ignited SSRMs have thrust vector control (TVC) to increase control authority. Ordnance for motor ignition and separation systems is completely redundant. Solid-motor separation is accomplished using redundantly initiated ordnance thrusters that provide the radial thrust to separate the expended solid motors from the booster.

Status: Active.
Gross mass: 19,327 kg (42,608 lb).
Unfuelled mass: 2,282 kg (5,030 lb).
Height: 14.70 m (48.20 ft).
Diameter: 1.17 m (3.83 ft).
Span: 1.17 m (3.83 ft).
Thrust: 628.31 kN (141,250 lbf).
Specific impulse: 278 s.
Specific impulse sea level: 273 s.
Burn time: 75 s.
Number: 45 .

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Associated Countries
Associated Engines
  • GEM 46 Hercules solid rocket engine. 608.1 kN. Air-ignited versions have nozzle ratio of 24.8:1, specific impulse of 284 sec. Isp=274s. First flight 1998. More...

Associated Launch Vehicles
  • Delta 3 American orbital launch vehicle. Delta 3 was an attempt by the manufacturer to provide the ultimate development of the original Delta booster. The core vehicle was beefed-up to accomodate much larger solid rocket boosters and a new cryogenic upper stage. However problems were incurred during development, resulting in the first two launches being failures. Meanwhile the satellite launch market crashed and the new vehicle was left without customers. The venerable Delta 7925 soldiered on for NASA, and the new Delta 4 series captured the USAF EELV requirement. More...
  • Delta 7920H American orbital launch vehicle. Version of Delta 7000 using much larger GEM 46 solid rocket motors originally developed for the Delta 3. More...
  • Delta 7925H American orbital launch vehicle. Four stage vehicle consisting of 9 x GEM-46 + 1 x EELT Thor/RS-27A + 1 x Delta K + 1 x Star 48B More...

Associated Propellants
  • Solid Solid propellants have the fuel and oxidiser embedded in a rubbery matrix. They were developed to a high degree of perfection in the United States in the 1950's and 1960's. In Russia, development was slower, due to a lack of technical leadership in the area and rail handling problems. Solid propellants have the fuel and oxidiser embedded in a rubbery matrix. They were developed to a high degree of perfection in the United States in the 1950's and 1960's. In Russia, development was slower, due to a lack of technical leadership in the area and rail handling problems. More...

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