GEM-63s Stacked, As NROL-101 Processing Continues

The aerodynamic ogive-shaped heads of the GEM-63s are unique only to the Atlas V variant of the boosters. The GEM-63XLs which will fly next year on Vulcan-Centaur possess conical heads. Photo Credit: ULA

As United Launch Alliance (ULA) counts down to next weekend’s targeted flight of a long-delayed Delta IV Heavy—laden with the highly secretive NROL-44 payload for the National Reconnaissance Office—another rocket stands proud at Cape Canaveral Air Force Station, Fla., targeting a second classified liftoff, later this fall. On Friday, ULA declared that a trio of new-style solid-fueled rocket boosters had been installed around the base of its Atlas V 531 on Space Launch Complex (SLC)-41 in readiness for the NROL-101 mission. Of note, the installation occurred exactly seven years to the day since the 531’s most recent launch.

Video Credit: ULA

“The #GEM63s are mated to #AtlasV that will launch #NROL101 later this year,” ULA tweeted yesterday. “This will be the debut launch for the solid rocket boosters. GEM-63s will be used on Atlas V launches to build flight experience in preparation for the GEM-63XLs on #VulcanCentaur’s first flight in 2021.”

The Atlas V 531 gained its nomenclature from having a 17-foot-wide (5-meter) payload fairing, three strap-on boosters and a single-engine Centaur upper stage. It has only flown three times in this configuration, delivering the first three Advanced Extremely High Frequency (AEHF) military communications satellites to geostationary altitude on 18 August 2010, 4 May 2012 and 18 September 2013. As recently described by AmericaSpace’s Mike Killian, the six-satellite AEHF network was completed earlier this year and its final member satisfactorily concluded on-orbit testing just last week.

AmericaSpace photo ULA United Launch Alliance Atlas V 531 SLC 41 Cape Canaveral Advanced Extremely High Frequency 3 AEHF 3 satellite photo credit John Studwell 1 AmericaSpace
The Atlas V 531 was lasted used on 18 September 2013 to launch AEHF-3. Photo Credit: John Studwell/AmericaSpace

But on its three previous flights, the 531 utilized older Aerojet Rocketdyne-built AJ-60A solid-fueled boosters. For NROL-101, it will be equipped with Northrop Grumman Corp.’s latest incarnation of the Graphite Epoxy Motor, known as a GEM-63, numerically designated to identify its 63-inch-diameter (1.6-meter) casing.

The GEM-63 is the fourth generation of this motor, following hard on the heels of the 40-inch (101.6 cm) GEM-40, which supported 132 Delta II missions between November 1990 and September 2018, the 46-inch (116.8 cm) GEM-46 used on six Delta II Heavy launches and the 60-inch (150 cm) GEM-60, which was partnered with the workhorse Delta IV Medium+ for 26 flights, most recently that rocket’s retirement swansong in August 2019.

The GEM-63 will be trialed for the first time on NROL-101. Photo Credit: Northrop Grumman Corp.

The GEM-63’s origins date back to contracts awarded to Orbital ATK back in September 2015, with a key intention to “significantly lower the price to ULA and to the U.S. Government”. In tandem with a barebones GEM-63 for Atlas V operations, the “extended” GEM-63XL was developed for Vulcan-Centaur. And it was always intended that the new solids, together with a substantial chunk of other hardware for ULA’s new heavylifter, would be test-flown on the Atlas V.

Within just three years, in September 2018 the GEM-63 completed its first 110-second static fire test at Northrop Grumman’s test area in Promontory, Utah, which qualified it for use on the Atlas V, followed by a second test in early 2019 which qualified it for Air Force missions. A third was completed last October to satisfy Air Force requirements, validate ballistic performance across the temperature range and optimize the nozzle.

The 107-foot-long (32.5-meter) Common Core Booster (CCB) for NROL-101 stands upright in the Vertical Integration Facility (VIF) at SLC-41, earlier this month. Photo Credit: ULA

This astonishingly fast “drop-in solution” has been helped along the way by a long GEM heritage. “The GEM-63 utilized many lessons learned from prior GEM programs,” Northrop Grumman’s Kendra Kastelan previously told AmericaSpace. “Some of their design features and manufacturing processes are even common with GEM-63. It is fair to say that GEM-63 wasn’t starting at the beginning of the learning curve, so NGC was able to get to production sooner than a typical program.”

The 107-foot-long (32.5-meter) Common Core Booster (CCB) and single-engine Centaur upper stage for the Atlas V 531 assigned to NROL-101 arrived on the Space Coast in early July, transported from ULA’s Decatur, Ala., facility via the RocketShip cargo vessel. This was followed by the delivery of the three GEM-63s later that same month. At the instant of liftoff, this triad of solid-fueled powerhouses will churn out over 1.1 million pounds (508,000 kg), providing more than half of the total thrust needed to get the Atlas V 531 airborne. All told, with the CCB’s RD-180 engine also burning, the rocket will depart SLC-41 with a thunderous roar and almost 2 million pounds (900,000 kg) of thrust.

A GEM-63 is mated to the Atlas V. Photo Credit: ULA

A “middle-of-the-road”-type booster in terms of its lifting potential, the 531 can reportedly put up to 34,350 pounds (15,575 kg) of payload into low-Earth orbit and send around 16,480 pounds (7,475 kg) to Geostationary Transfer Orbit (GTO). This made it ideally suited for hauling the 13,600-pound (6,170 kg) AEHF payloads aloft on its first three missions. And although the nature of NROL-101—which will mark ULA’s 30th launch for the NRO—remains shrouded in secrecy, the use of the 531 is likely indicative of the satellite’s mass, energy requirement, orbital location or possibly all three.

Those 30 NRO missions have flown atop ULA’s impeccably reliable Atlas V and Delta IV product lines. Sixteen Atlas V launches for the NRO took place between June 2007 and October 2017 and 12 Delta IVs—including six missions by the gargantuan, triple-cored Delta IV Heavy—did so between June 2006 and January of last year. Next weekend’s planned launch of NROL-44 will mark the 29th mission, although an exact launch date for NROL-101 has yet to be announced. Presently, it is listed to fly later this fall.

A GEM-63 sits snugly against the base of the Atlas V on Friday. Photo Credit: ULA

With the already month-long delay to NROL-44, the final quarter of 2020 is shaping up to be a packed manifest for ULA. Assuming the mission flies as intended next weekend, another Delta IV Heavy—currently deep into processing at Space Launch Complex (SLC)-6 at Vandenberg Air Force Base, Calif.—is expected to fly before year’s end, although (as is customary with NRO missions) it will be put through a Wet Dress Rehearsal (WDR) beforehand. That mission will carry the NROL-82 classified payload, which may represent a classified electro-optical surveillance satellite.

Activity will also resume on the Space Coast, with more two Atlas V missions slated to rise from SLC-41 later this the fall. The first will use the most powerful variant of the rocket (the “551”, with five strap-on solids) to deliver the mixed-payload Space Test Program (STP)-3 to GTO, whilst the second with USSF-8 for the Space Force uses a never-before-flown configuration, known as the “511”.

Solar Orbiter launches atop the “Slider” 411 in February 2020. USSF-8 at year’s end will rise atop the “Super Slider” 511, flying its first mission. Video Credit: AmericaSpace

Equipped with only a single solid-fueled booster, the 511 will—like its cousin, the Atlas V 411, last used in February to launch Solar Orbiter—offer an unusual “sideways-flying” launch perspective as it leaves the pad. Although steering actuators on its RD-180 engine will counteract the asymmetrical thrust from the single solid, mitigating the propulsive offset and ensuring the rocket flies straight and true, it promises to be a disconcerting sight for spectators. And as ULA CEO Tory Bruno has previously revealed, each Atlas V variant has its own unique nickname. With the 411 having already earned the nickname “Slider” from ULA CEO Tory Bruno, the moniker for the larger 511 is “Super Slider”.

Assuming all missions fly as planned—and with the second uncrewed test flight of Boeing’s CST-100 Starliner to the International Space Station (ISS) widely expected to slip into early January—2020 may close with a cumulative total of two Delta IV Heavy launches and seven Atlas Vs.

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