ULA readies Atlas V for launch of NROL-79 reconnaissance satellite
An archive photo of a ULA Atlas V 401 common core booster being lifted into the vertical position for a previous launch. Photo Credit: ULA
After enduring several delays – most recently from an issue with the second stage of its Atlas V launch vehicle – United Launch Alliance (ULA) is set to launch the classified NROL-79 mission.
Liftoff is planned for Wednesday, March 1, 2017, at about 9:50 a.m. PST (12:50 p.m. EST / 17:50 GMT) from Space Launch Complex 3 at Vandenberg Air Force Base in California.
According to Spaceflight Now, the exact duration of the launch window is classified, but the opportunity is expected to close by 10:30 a.m. PST.
Official NROL-79 mission artwork. Credit: ULA
The Rocket
Tasked with launching the clandestine NROL-79 payload is the reliable Atlas V in its 401 configuration. By far the most common variant of ULA’s Atlas V, the 401 is the base model of the Atlas.
The “401” designation signifies a 4-meter payload fairing, no supplemental solid rocket boosters, and a single RL10C-powered Centaur stage.
The Atlas common booster core is powered by a Russian-made RD-180 main engine, which provides 860,000 pounds (3,827 kilonewtons) of thrust at liftoff. This increases to 933,000 pounds (4,152 kilonewtons) as the vehicle climbs and the atmosphere thins.
The kerosene (RP-1) fueled and liquid oxygen oxidizer engine has been a highly reliable powerplant for ULA’s rocket with a notable exception of the anomaly on the OA-6 resupply mission to the International Space Station.
The Atlas V’s second (Centaur) stage is outfitted with a single Aerojet Rocketdyne RL10C. The Centaur holds up to 45,920 pounds (20,830 kilograms) of liquid hydrogen and liquid oxygen propellant for the highly efficient engine and contains the flight and navigation computer for the Atlas V.
The RL10 has a long history, with a heritage dating back to the 1950s and the first flight in 1961. The RL10C-1 model flown on the Atlas V Centaur provides 22,890 pounds (101.8 kilonewtons) of vacuum thrust and has been solidly dependable throughout its Atlas V use, save for an anomaly on the NROL-30 mission.
Like its OA-6 counterpart, the NROL-30 mission was still classified as a success as the payload was able to reach its intended orbit. Those aberrations aside, the Atlas V has proven itself to be a highly dependable launch vehicle with an enviable 100 percent mission success rate.
The Mission
Sitting atop the rocket is the classified NROL-79 payload. This secretive spacecraft is designed and operated by the National Reconnaissance Office (NRO), which is a key component of the United States’ intelligence apparatus. The NRO is also responsible for developing and operating space-based reconnaissance systems.
While much isn’t known about the specifics of the payload, some inferences can be made based on the capabilities of the Atlas V in its 401 configuration.
The base model of ULA’s workhorse vehicle can carry 14,705 pounds (6,670 kilograms) to a Sun-synchronous orbit (SSO) and may be a good estimate of the mass of the NROL-79 payload.
There has been information suggesting NROL-79 might be a pair of Naval Ocean Surveillance Satellite (NOSS) spacecraft, much like those deployed on the previous NROL-36 and NROL-55 missions.
The NOSS spacecraft, also known by the code name INTRUDER, tip the scales at approximately 14,330 pounds (6,500 kilograms) for the pair and provide signals intelligence to the NRO and U.S. Navy.
Wednesday’s liftoff will mark the 70th flight of an Atlas V, and the 35th of the rocket in its base 401 configuration. It will also be the second launch of 2017 to fly out of Vandenberg Air Force Base (the first was SpaceX’s Iridium-1 mission) and ULA’s second Atlas V flight of the year.
Curt Godwin
Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.
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