It is turning into a “Groundhog Day” of sorts at Space Launch Complex (SLC)-41 pad surface at Cape Canaveral Air Force Station, Fla., following Wednesday night’s scrubbed launch attempt of United Launch Alliance’s (ULA) Mighty Atlas V with the highly secretive NROL-101 payload for the National Reconnaissance Office. The mission, which has succumbed to two postponed launch attempts in as many days, will now stand down until no sooner than Friday, 6 November, although the weather outlook heading into the weekend looks highly unfavorable.
As detailed in AmericaSpace’s NROL-101 preview article, virtually nothing of substance has trickled into the public domain about the nature of the payload. However, its presence atop the Atlas V in its infrequently-used “531” configuration—equipped with a 17-foot-diameter (5-meter) payload fairing, three solid-fueled boosters and a single-engine Centaur upper stage—does offer an indicator of its possible size, mass, orbital destination or energy requirements.
The 531 has only been used three times, delivering the first three Advanced Extremely High Frequency (AEHF) military communications satellites in August 2010, May 2012 and most recently September 2013. Nicknamed “The Thunderer”, the 531 has the capability to lift 34,350 pounds (15,575 kg) to low-Earth orbit and 16,480 pounds (7,475 kg) to Geostationary Transfer Orbit.
The Atlas V Common Core Booster (CCB) and Centaur for this mission were delivered to the Cape in early July, followed by the three uprated, 63-inch-wide (1.6-meter) Graphite Epoxy Motors (GEM-63s) later that month. These rocket parts came together in the 300-foot-tall (100-meter) Vertical Integration Facility (VIF) in September for the Launch Vehicle On Stand (LVOS) milestone.
Last month, minus its Medium Payload Fairing (PLF), the vehicle was rolled the 1,800 feet (550 meters) from the VIF to the SLC-41 pad surface for a Wet Dress Rehearsal (WDR). In the wake of the WDR, the RP-1 remained in the Atlas V tanks, but the cryogens were fully drained and the stack was returned to the VIF for integration of its payload. On 26 October, NROL-101—fully encapsulated in its two-piece fairing—was mounted atop the rocket, topping it off at 206 feet (62.8 meters) tall.
Originally targeting a sunset liftoff on 3 November, a smooth Launch Readiness Review (LRR) on Saturday produced a “Go” for the Atlas V to be rolled from the VIF to the pad on Monday. Although the vehicle and its Mobile Launch Platform (MLP) reached the pad without incident, strong winds from the north were expected to be sustained near 35 mph (56 km/h), gusting at up to 43 mph (68 km/h).
After rollout, a flow-rate reduction was noted in the payload’s Environmental Control System (ECS), which prompted an almost immediate rollback to the VIF. “Platforms in the VIF enabled technicians to reach this area at the top of the rocket,” ULA subsequently noted on its website, “which is inaccessible at the launch pad.”
“Going to roll back to the VIF,” ULA CEO Tory Bruno tweeted. “Very high winds at the pad. May have sustained damage to the upper ECS duct. Spacecraft is fine, but need to check it out.” It would appear that the task was accomplished swiftly, for the Atlas V was returned to SLC-41 later on Tuesday afternoon.
Weather conditions for Wednesday’s second launch attempt were predicted to be 70-percent-favorable and countdown operations began without incident at T-6 hours and 20 minutes. The Atlas and Centaur systems were respectively powered-up and launch teams proceeded through an intricate sequence of testing of the vehicle.
Just before the first 15-minute built-in hold in the countdown at T-2 hours, prior to fueling, Launch Weather Officer Jessica Williams reported that conditions were acceptable to begin loading the rocket with 66,000 gallons (300,000 liters) of cryogenic liquid oxygen and hydrogen propellants. The Atlas V’s flight supply of rocket-grade kerosene (known as “RP-1”) was loaded aboard the vehicle during WDR operations and has remained in the tanks.
Ms. Williams noted that the weather exhibited just a few low and broken clouds, good visibility and east-northeasterly winds of 25 mph (40 km/h) to 30 mph (48 km/h).
Shortly after 3 p.m. EST, Launch Conductor Scott Barney authorized teams to begin their departure from SLC-41, preparatory to fueling. Coming out of the first of two 15-minute built-in holds in the countdown, engineers began the process of chilling down the liquid oxygen propellant lines.
But shortly after 3:30 p.m. EST, a ground valve issue emerged with the first-stage liquid oxygen system, prompting Mr. Barney to halt the countdown at T-1 hour and 47 minutes to enable Anomaly Chief Dave McFarland and his team to troubleshoot the problem. Engineers were despatched to SLC-41 to examine hardware in the Atlas V’s liquid oxygen storage area, but at 5:54 p.m. EST—by happenstance the exact time that T-0 should have been reached—Mission Director Col. Chad Davis formally called a scrub.
ULA Launch Director Tom Heter III relayed the call to his team, as the process of reconfiguring the vehicle got underway for a 48-hour turnaround. In a subsequent update, it was noted that “an unexpected system response from remotely-commanded ground system liquid oxygen valves” was the culprit behind Wednesday’s scrub. “Almost there, but ran out of time,” tweeted Mr. Bruno. “We will be back in 48 hours.”
But the weather outlook for both Friday and Saturday do not look good. According to the 45th Weather Squadron at Patrick Air Force Base, in an update issued Wednesday night, there is only a 40-percent probability of acceptable conditions for Friday, deteriorating to only 30 percent on Saturday.
“A strong high-pressure ridge across the mid-Atlantic states and the elongated area of low pressure south of Cuba associated with Tropical Depression Eta is creating a tight pressure gradient over the Florida peninsula,” it was noted. “This gradient will tighten through Sunday, as Eta moves back towards the northeast, closer to Florida.” Although wind-speed forecasts are dependent upon Eta’s future progress, winds of up to 34 mph (55 km/h) are anticipated, together with scattered showers and some thicker mid-to-high-level clouds, plus a “slight” potential for lightning on Saturday.