Spaceflight Insider

ULA selects Orbital ATK’s GEM 63/63 XL SRBs for Atlas V and Vulcan boosters

GEM 60 test fire Utah Orbital ATK photo posted on SpaceFlight Insider

Photo Credit: Orbital ATK

Colorado-based United Launch Alliance (ULA) announced on Sept. 22, 2015, that it had selected Solid Rocket Boosters (SRBs) produced by Orbital ATK on the venerable Atlas V and forthcoming Vulcan launch systems. The GEM 63 will replace Aerojet Rocketdyne’s AJ-60A SRBs on upcoming flights of the Atlas V, and the XL version of the booster has been selected to aid certain versions of Vulcan aloft. 

According to statements from Orbital ATK and ULA representatives to SpaceFlight Insider, the SRBs will be ready to support flights as early as 2019 – when ULA currently plans to have the first flight of Vulcan take place.

“We’ll have the GEM 63 static-fired and qualified in late 2018… and I think that would equate to an initial launch with GEM-63s in 2019, probably early that year,” Orbital ATK’s Program Manager for GEM 63/63 XL Jason Meredith told SpaceFlight Insider.

United Launch Alliance Vulcan boosters image posted on SpaceFlight Insider

Although the solid rocket boosters in this image bear a resemblance to the AJ-60A, it now appears that the GEM 63XL will provide the extra lift requirements of the Vulcan system.
Image Credit: ULA

According to Meredith, both the GEM 63 and 63XL should be ready to support missions by the end of 2018. These two motors will have one substantial difference, owing to the size of the rockets on which they will be utilized.

“We are continuing the development process, as it is fairly early for the Vulcan, but right now, we’re talking about a difference that’s on the order of about five feet in length [between the 63 and the 63 XL], hence the ‘XL’ in the motor’s name,” Meredith said.

ULA is working to have the Vulcan booster to be certified and ready to send payloads to orbit for customers such as the U.S. Department of Defense (once Vulcan has been approved to fly under the Evolved Expendable Launch Vehicle program), NASA, and commercial satellite firms. The new launch system employs many elements that currently fly on the Atlas V and Delta IV

Both ULA and Orbital ATK noted that having one family of SRBs, with variants in place that can be flown on all of the families of boosters fielded by ULA, was a key consideration behind today’s announcement.

“There will be a lot of commonality between the two boosters. The strap-on motors there will be called the GEM 63 and the GEM 63XL. The GEM 63 will be designed to provide the performance to the Atlas V that is delivered to date [by the AJ-60A]. So, it is a ‘drop-in’ replacement. Whereas [with] the GEM 63XL, we’re working closely with ULA to develop that strap-on booster to meet the performance requirements of the Vulcan launch vehicle,” said Orbital ATK’s Jason Meredith.

Meredith noted the similarities between the 63 and 63XL can be traced back to another SRB produced by Orbital ATK – the GEM 60 (which is currently used on ULA’s Delta IV family of rockets).

ULA was asked as to what caused the Launch Service Provider opted to move away from the Aerojet Rocketdyne’s AJ-60A and toward the new GEM 63.

“Orbital ATK is the best option for Atlas V and Vulcan. We’ve carefully reviewed all of our options,” ULA’s Lyn Chassagne said.

United Launch Alliance Delta IV Medium+ 5,4 rocket launches from Cape Canaveral Air Force Station's Space Launch Complex 37 photo credit Jared Haworth SpaceFlight Insider

The Gem 63/63XL will be based on Orbital ATK’s GEM-60 solid rocket boosters. Photo Credit: Jared Haworth / SpaceFlight Insider

Besides its experience with the GEM 60, Orbital ATK also has experience in other, far larger solid rocket motors (the firm produced the four segment boosters for NASA’s Space Shuttle Program and is currently developing a five-segment version for NASA’s new Space Launch System super heavy-lift booster).

While there are similarities between the Atlas V and Vulcan launch vehicles, there are enough differences to require that two distinct SRBs be produced.

“From our perspective, to meet the requirements of the Vulcan launch systems, we did have to, I’ll say, ‘super-size’ – increase the size of the 63 – to meet those requirements that we’re working on with ULA for Vulcan,” Meredith noted.

From the perspective of Orbital ATK, the selection to go with the GEM 63 was tied to one of the most crucial concerns of the NewSpace era – cost.

“Part of what we see is the opportunity for lower-cost on the Vulcan launch vehicle – is the synergy in providing both of those strap-on boosters – for both the Atlas V and Vulcan and so that was part of what we discussed with ULA… as they move work to transition from the Atlas V to Vulcan. That’s part of the low-cost solution that we provided ULA for their SRB requirements.”

Representatives with United Launch Alliance noted in a release, co-issued by the two companies, that risk mitigation and continuing the successful track record that the Atlas V currently enjoys also played its part in Tuesday’s announcement.

“Our ability to deliver critical national security, scientific, and commercial satellites into the correct orbit for each mission is filled with risks and challenges, and ULA has delivered every time,” said Tory Bruno, ULA’s president and CEO. “This reliability will continue as we develop the right vehicle with the right team.”

This announcement serves to underline other agreements between the two aerospace firms. ULA has already been tapped to provide two Atlas V 401 boosters to hoist Orbital ATK’s Cygnus spacecraft out of Earth’s gravity well and on their way to the International Space Station under the $1.9 billion Commercial Resupply Services agreement Orbital ATK has with NASA – the first flight is currently slated for Dec. 3, 2015, and the second flight sometime in 2016.

When asked about what prompted ULA to select the GEM 63, Meredith reiterated that the need to keep costs to a minimum, as well as having the same firm produce both boosters, played a role in the decision-making process. A view underscored by Bruno.

“As ULA transforms the space lift industry, strong partners such as Orbital ATK are critical to reducing cost, introducing cutting-edge innovation and continuing our focus on mission success,” Bruno said. “We have relied for decades on Orbital ATK’s industry leading rocket motor technology, which is ideally suited to support our future rocket launch plans.”

If used in a similar fashion as the AJ-60A, the GEM 63 would likely be used in various configurations (between 0–5 of the SRBs being used) on the Atlas V. When one considers some of the similar characteristics between the Atlas V and Vulcan systems, it is likely that similar configurations could be used. These boosters are employed when the upmass requirements of a payload require more thrust. Dependent on the weight of these spacecraft, different numbers of the GEM 63XL will be affixed to the Vulcan’s first stage.


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

“As ULA transforms the space lift industry, strong partners such as Orbital ATK are critical to reducing cost, introducing cutting-edge innovation and continuing our focus on mission success,” Bruno said

Didn’t SpaceX transform the space lift industry? Everything that ULA & Ariane & the others are doing is in response to SpaceX. Guess they are trying to take credit away from SpaceX, now.

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