Eleven months to the day since its most recent launch, a Northrop Grumman Corp. Minotaur-class booster took flight from Pad 0B at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., early Tuesday. Liftoff of the four-stage solid-fueled vehicle—making its first outing in its Minotaur I configuration since November 2013—took place at precisely 9:35 a.m. EDT to lift the highly secretive NROL-111 payload to orbit on behalf of the National Reconnaissance Office. The launch was delayed for more than 2.5 hours, on account of thunderstorms and highly dynamic lightning cells in the vicinity of the Wallops facility.
Descended from the Minuteman-II Intercontinental Ballistic Missile (ICBM), the Minotaur I booster stands 63 feet (19.2 meters) tall and, including today’s perfect launch, has now completed 12 successful missions since January 2000. It has the potential to inject payloads weighing up to 1,280 pounds (580 kg) into low-Earth orbit and up to 730 pounds (330 kg) into Sun-synchronous orbit, thus positioning it squarely within the bracket of “small expendable launch vehicles”.
Six of its missions, between January 2000 and February 2011, originated from Space Launch Complex (SLC)-8 at what is now Vandenberg Space Force Base, Calif., with six others between December 2006 and this morning having been staged from the pretty seaside environs of Pad 0B at MARS.
Over the course of the last two decades and across its 12 flights, the Minotaur I has delivered a range of small military payloads into orbit for purposes ranging from reconnaissance and infrared missile-plume observations to automated rendezvous and proximity operations and from evaluations of advanced imaging and communications technologies to meteorology, climatology, “space weather” monitoring and bacterial research.
Significantly, it has a proven track record in furnishing near-term solutions to military requirements, successfully lofting December 2006’s TacSat-2 mission only seven months after the contract award and demonstrating an ability to progress from Payload Mate to Launch in under six days.
Contracts to launch NROL-111 were awarded to Orbital ATK Inc. by the U.S. Air Force’s Rocket Systems Launch Program (RSLP), part of the Launch Enterprise Directorate at the Space and Missile Systems Center (SMC) at Los Angeles Air Force Base, Calif., way back in December 2016. Orbital ATK was subsequently acquired by Northrop Grumman Corp. in June 2018. The launch services contract totaled $29.2 million and initially called for the NROL-111 payload to be flown “no later than 24 months” after the award.
It represented the first award under the Orbital/Suborbital Program (OSP)-3 Lane 1 capability, which provides for the insertion of payloads weighing between 400 pounds (180 kg) and 4,000 pounds (1,800 kg) into low-Earth orbit, together with other long-range suborbital missions.
“Continued reliability of space vehicle delivery methods and affordable access to space for the National Reconnaissance Office is an essential forefront for space superiority,” said Lt. Gen. Samuel Greaves, who was until March 2017 the SMC commander and the Air Force’s program executive officer for space at Los Angeles Air Force Base.
“Utilizing the capability of the OSP-3 contract Lane 1 capability immediately benefits our Department of Defense mission partners. The OSP-3 capability also holds great potential for SMC to provide assured access to space for future DoD missions.”
Hopes of launching NROL-111 before the end of 2018, in keeping with the 24-month requirement, ultimately came to nothing and the mission slipped firstly until late 2019, then to late 2020 and ultimately into the summer of 2021. No details about the cause of these lengthy delays have been revealed.
Just last month, the NRO announced 15 June as its targeted launch date, with a five-hour “window” running from 6:30 a.m. through 11:30 a.m. EDT. Last week, that expansive timeframe was further narrowed to produce an estimated T-0 at 7 a.m. EDT.
Unsurprisingly for a highly classified payload, little detail has emerged about the nature of NROL-111, other than it comprises three discrete NRO payloads and will “provide intelligence data to United States senior policy-makers, the Intelligence Community and Department of Defense”.
It also added in a tweet that NROL-111 will “support” a critical national security mission to “operate sophisticated overhead intelligence-collection systems to provide near-real-time imagery and signals intelligence” for the Department of Defense and international partners.
NROL-111 represents the first dedicated NRO payload to ride a Minotaur I in more than a decade. Its last mission was NROL-66—also known as the Rapid Pathfinder Program (RPP), devoted to radiation monitoring of the space environment from near-polar orbit at an altitude of 750 miles (1,200 km)—which flew out of SLC-8 at Vandenberg back in February 2011.
The NROL-111 mission patch depicts a fearsome flying wild boar, clad in traditional aviator’s attire, with three stars to represent each of its three payloads. “Boars are a good spirit guide to call on when you have ambitious goals,” the NRO explained in its description of the patch’s symbology, “and inspire tenacity in the hunt to achieve them.” Beneath the boar was the legend “Boldness Be My Friend”.
All four stages on the Minotaur I are solid-fueled, with the two lower stages consisting of hardware from decommissioned Minuteman-II missiles and the two upper stages utilizing hardware from Northrop Grumman’s Pegasus-XL air-launched booster.
With a 60-percent probability of acceptable conditions at T-0, it came as little surprise when efforts to roll back the gantry and proceed with the countdown were held to allow a thunderstorm to pass over Wallops. Eventually, this threatening weather—including lightning cells—passed offshore to the east of Virginia and teams worked to co-ordinate a revised T-0 at 9:35 a.m. EDT, about 25 minutes before the closure of Tuesday’s launch window. As launch time neared, the weather outlook improved to 70 percent. “Range Green” came the final encouraging call a couple of minutes before launch.
Liftoff got underway with the ignition of the Minotaur I’s first-stage engine, generating a total propulsive yield of 210,000 pounds (95,250 kg) and a fast climb away from the Pad 0B complex. Two seconds after departing the pad, the rocket commenced a visually dramatic computer-controlled pitch and roll program maneuver to establish itself onto the proper flight azimuth for its ascent to orbit. At T+38 seconds, it encountered the period of maximum aerodynamic turbulence—known as “Max Q”—on its airframe.
The first stage shut down and separated at 61 seconds into the flight, after which the SR-19 second-stage engine was lit to push the Minotaur I uphill with 60,000 pounds (27,000 kg) of thrust. It burned hot and hard for 72 seconds, before it too was discarded a little over two minutes into the flight. By this point, the Minotaur I weighed barely a quarter of its mass at liftoff. And it was here, unsurprisingly in view of the mission’s secrecy, that direct coverage of the flight concluded. However, based upon previous Minotaur I launches, the two upper stages furnished an additional 2.5 minutes’ worth of “burn-time” to get NROL-111 to its requisite orbit.
The Pegasus-heritage Orion-50XL of the third stage was due to run for 73 seconds at a thrust of 26,600 pounds (12,000 kg) and it was during this mission phase that the Minotaur I’s payload fairing would be jettisoned to expose NROL-111 to the near-vacuum conditions of space for the first time.
By the end of third-stage propulsive flight, the vehicle would have already been some 290 miles (470 km) downrange of its Virginia launch site, at an altitude of about 150 miles (240 km) and traveling in excess of Mach 20. After its separation, the Minotaur I coasted for a few minutes, prior to the separation of the third stage and ignition of the fourth stage’s Orion-38 engine for a further 68 seconds. Burning with 7,800 pounds (3,500 kg) of thrust, this final push served to deliver and position the NROL-111 payload for deployment into its orbital slot.