Spaceflight Insider

MUOS-3 to get boost from AJ-60A solid rocket motors

United Launch Alliance Atlas V 551 rocket Space Launch Complex 41 Cape Canaveral Air Force Station photo credit Jason Rhian SpaceFlight Insider

Five Aerojet Rocketdyne AJ-60A solid rocket motors will be used to launch the MUOS-3 spacecraft to GTO on Tuesday, Jan. 20. Photo Credit: Jason Rhian / SpaceFlight Insider

CAPE CANAVERAL, Fla — When the third Mobile User Objective System (MUOS-3) spacecraft takes to the skies in about two days’ time, it will do so with the assistance of five AJ-60A solid rocket motors (SRM). Each of these will be affixed to the first stage of United Launch Alliance’s (ULA) Atlas V 551 launch vehicle’s booster core. The SRMs provide the extra thrust that is required to send the roughly 15,000 lbs (6,803 kg)MUOS-3 satellite out of Earth’s gravitational well – and on its way to orbit.

Developed at the close of the 1990s, the AJ-60A are solid rocket boosters designed for the Atlas V family of launch vehicles. According to the motors’ producer, Aerojet Rocketdyne, these commercially-produced motors are for the Atlas V launch vehicle, which is part of the U.S. government’s Evolve Expendable Launch Vehicle Program (EELV).

Atlas V 541 NROL-67 Cape Canaveral Air Force Station Space Launch Complex 41 United Launch Alliance ULA photo posted on SpaceFlight Insider

An Atlas V 541 launches the NROL-67 payload for the National Reconnaissance Office in April of 2014. Photo Credit: ULA

The AJ-60 is a monolithic motor with no segmented joints. This eliminates historical failure modes and provides functional and operational simplicity. The motor also has a fixed canted nozzle and no active trust vector control.

While Aerojet Rocketdyne’s webpage for the AJ-60A states that it can also be employed on either strategic missiles or on small-scale launch vehicles, Aerojet Rocketdyne’s Peter Cova, stated that the SRM is, at present, solely used on the Atlas V family of boosters.

“We received the contract award back in 1999 and in 42 months’ time, we completed the development and qualification of the AJ-60A and had our first flight in July of 2003,” Cova said. “Since then, we have delivered 74 flight-worthy solid rocket boosters and we have flown 60 of those on 20 different missions – with a 100 percent mission success rate.”

As is common on solid rocket boosters of this type, the AJ-60A is described by Aerojet Rocketdyne as a: composite graphite fiber and Aramid-filled EPDM insulation monolithic motor case.

The AJ-60A has no segmented joints, also the engine nozzle itself is fixed at a 3-degree cant. However, should a mission require it, the SRM can be upgraded to a flexseal TVC so that the thrust coming out of the AJ-60A can be directed. Both the throat, as well as the exit cone of the booster are constructed using carbon-phenolic composite materials.

According to information on the company’s website, the fact that the AJ-60A measures 62 inches (157 cm) in diameter and has a total length of some 669 inches (1,699 cm) – makes the SRM the largest monolithic motor that is currently being produced.

United Launch Alliance Atlas V 551 rocket Space Launch Complex 41 Cape Canaveral Air Force Station photo credit United Launch Alliance

The launch of MUOS-3 – will be the 61st time that the boosters, produced by Aerojet Rocketdyne, have been used to send a mission to orbit. Photo Credit: ULA

The AJ-60A has been used on an array of missions that include commercial, NASA, USAF and missions for the Department of Defense. A report appearing on Gunter’s Space Page states that between 1 and 6 AJ-60A’s can be employed on ULA’s newly-proposed Next Generation Launch System (NGLS), the planned successor of both the Atlas V and Delta IV family of launch vehicles.

The NGLS would move away from use of the Russian-made RD-180 rocket engine and would instead employ a U.S.-made engine such as the BE-4, manufactured by Blue Origin.

“Aerojet Rocketdyne takes the actions to decrease launch-service prices from ULA and its customers seriously. We are prepared to take significant actions to transform and lay a new foundation that can deliver the best value, next-generation solid rocket booster for ULA’s Next Generation Launch System. We are also driving affordability with continued reliability, committed to being ULA’s sole solid rocket motor supplier,” Cova said.


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Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

Reader Comments

67 yr old man, feel like I seen everything, now we are back to the future, 60’s with better rockets, better space crafts, hey go for it GOD bless!

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