After more than a year on the pad, and an unenviable eight scrubbed launch attempts, United Launch Alliance (ULA) is gearing up to fly one of its last few Delta IV Heavy boosters from Space Launch Complex (SLC)-37B at Cape Canaveral Air Force Station, Fla. Liftoff of the snakebitten mission—laden with the highly secretive NROL-44 payload for the National Reconnaissance Office—is expected to occur at 6:15 p.m. EST Thursday.
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Weather conditions for Thursday are currently predicted to be 90-percent favorable, declining to 80 percent in the event of a slip to Friday and 70 percent for Saturday. “Favorable weather is anticipated during Thursday evening’s launch attempt, with little concern of a weather-related violation,” noted the 45th Weather Squadron at Patrick Air Force Base in its L-2 update on Tuesday. “High pressure will cross the state and settle into the western Atlantic late in the week, resulting in gradually moderating temperatures and a very slow increase in moisture.”
Although it will be the first flight of a Delta-class booster since the swansong of the Delta IV Medium back in August 2019, Friday’s launch will be the sixth overall ULA launch of 2020, coming on the back of five successful Atlas V missions.
It has been one of ULA’s slowest years on record, in terms of launch cadence. Thus far in 2020, the Centennial, Colo.-headquartered launch provider flew Solar Orbiter in February, the sixth and last Advanced Extremely High Frequency (AEHF) military communications satellite in March, the U.S. Space Force’s classified X-37B Orbital Test Vehicle (OTV) in May, NASA’s Perseverance rover to Mars in July and, just last month, the classified NROL-101 mission atop a rarely-used variant of the Atlas V.
More flights—including a second uncrewed test of Boeing’s CST-100 Starliner to the International Space Station (ISS)—were originally baselined for 2020, but technical difficulties pushed it into the first half of next year. A second Delta IV Heavy, set to fly out of Vandenberg Air Force Base, Calif., with the secret NROL-82 payload, has also reportedly slipped into early 2021.
Six launches will mark a slight increase over 2019’s accomplishment of five flights, but will still close out 2020 as one of ULA’s “lightest” years on record. In fact, you would have to look all the way back to 2005 to see the last occasion that as few as six missions were executed by the Atlas or Delta product-lines. Looking ahead to 2021, the picture brightens, with up to ten Atlas V missions, the Delta IV Heavy with NROL-82 and the maiden voyage of ULA’s new Vulcan-Centaur heavylifter.
And watching 2020 in its entirety from the seaside environs of SLC-37B has been the gargantuan Delta IV Heavy, tasked with delivering NROL-44 into space. The 235-foot-tall (72-meter) beast—which comprises three Common Booster Cores (CBCs), mated together—was transported out to the pad on 15 November of last year, with initial expectations that it would fly in June 2020. The rationale for the longer-than-normal pad processing flow remains unclear, although fitting NROL-44’s pre-flight milestones in between other flights certainly played a role.
It underwent a fully-fueled Wet Dress Rehearsal (WDR) in the second week of January, before being postponed (for still unknown reasons) from June to 26 August. The NRO then requested an additional day of delay until the 27th.
Then the technical gremlins moved in for the summer…and the fall, too, as circumstances would transpire. Launch on the 27th was scrubbed due to a ground pneumatics control system issue and clocks were recycled for another try in the wee hours of 29 August. On that occasion, the countdown reached T-3 seconds, before the Terminal Countdown Sequencer Rack (TCSR) autonomously (and dramatically) commanded a “Hot Fire Abort”.
As is characteristic of the Delta IV Heavy’s staggered engine-start and ramp-up sequence, the starboard-side CBC roared to life as planned at T-7 seconds, but the proper conditions were not met for the ignition of its center and port-side counterparts at T-5 seconds. Another launch was ignominiously called off as ULA initiated an investigation, which zeroed-in on one of three pad-side regulators. All three were removed, refurbished and tested, before being reinstalled into the Delta IV Heavy.
But misfortune was far from done with the beleaguered mission. Hopes of flying on 26 September came to nought when a hydraulic issue with SLC-37B’s swing-arm system arose, forcing an additional three-day slip. Two more back-to-back scrubs were then enforced by the intractable Florida weather, with lightning warnings and a need to remove the pad crew to safety eating into their respective countdown operations. A hydraulic hose failure in the Mobile Service Tower (MST) piled yet more frustration onto the proceedings.
Finally, another attempt geared up for liftoff just a few minutes before midnight on 30 September. Countdown operations proceeded smoothly, with the weather outlook classified as “Green” and the only issue of any concern was an issue pertaining to the review of data readings. Anomaly Chief Dave McFarland and his team determined that a computer-controlled redline limit would be monitored manually, to avert the potential risk of a data readings issue from tripping up the terminal countdown. A slow-to-respond pad swing-arm sensor was “masked-out” to prevent it posing any further problems.
All went smoothly, again, until the final moments before the targeted launch. At T-14 seconds, the pad-side Radial Outward Firing Igniters (ROFIs) came to life like glittering sparklers to clear unburnt hydrogen from the vicinity of the engines. But as the last seconds ticked away, something did not look quite right, for the engine-side ROFIs did not fire. At T-7 seconds, with the same ominous pall of ashen-gray smoke last seen on 29 August, the Delta IV Heavy seemingly came alive, then fell silent, as abort calls rang out across the net.
“We experienced an automated abort because a sensor reported a fault,” tweeted ULA CEO Tory Bruno in the aftermath of the scrub. “Automated Safety System operated as intended. Bird and payload are safe and unharmed. Engine ROFIs were not fired. Turbopumps were not spun up. Mission safety first.”
As frustrating as yet another scrub for the snakebitten Delta IV Heavy might be, the rocket’s safety systems performed as advertised. “Recycle is always a better trade,” tweeted Mr. Bruno, “than the risk of killing a billion-dollar payload that took many years to build.” Initial hopes of flying as soon as 15 October came to nothing and ULA ultimately announced a new target of 23 October, “to allow our team to perform additional analysis and data-monitoring of ground systems to ensure they continue to perform nominally”.
That date also came ultimately to nought, when ULA announced that NROL-44 was being delayed indefinitely on the Eastern Range. “The #NROL44 launch date is now indefinite on the range,” it noted. “With continued emphasis on mission success, our team will continue to test and evaluate the swing-arm retraction system prior to the launch of the #DeltaIVHeavy. We will confirm a launch date as soon as possible.” Finally, on 4 December, ULA announced that it was targeting a five-hour “window” between 5:50 p.m. EST and 10:30 p.m. EST on 10 December, although this launch time was later refined to 6:15 p.m. EST.
Weather conditions are predicted to be 90-percent-favorable, tempered by the slight risk of violating the Cumulus Cloud Rule criterion. By pure serendipity, NROL-44 also marks ULA’s 30th launch for the National Reconnaissance Office. Had the mission flown as intended in the August-October timeframe, it would have been the 29th flight, but was “leapfrogged” by last month’s successful launch of NROL-101.