United Launch Alliance (ULA) has successfully launched its fifth and final flight of a mighty Delta IV Heavy from the West Coast, following Saturday’s spectacular 3:25:30 p.m. PDT (6:25:30 p.m. EDT) liftoff out of Vandenberg Space Force Base, Calif. The triple-barreled Heavy, which comprises three giant Common Booster Cores (CBCs), topped by a Delta Cryogenic Second Stage (DCSS), delivered the highly secretive NROL-91 payload to orbit on behalf of the National Reconnaissance Office.
All told, this afternoon’s flight marked the 14th launch of a Heavy, which entered service way back in December 2004. It has flown nine times out of Space Launch Complex (SLC)-37B at what is now Cape Canaveral Space Force Station, Fla., most recently lofting the snakebitten NROL-44 mission in December 2020.
But its forays out of Vandenberg have been somewhat sparser. And unlike the Cape, which has seen a couple of civilian science missions for NASA—the high-apogee maiden voyage of Orion on December 2014’s Exploration Flight Test (EFT)-1 and August 2018’s launch of the Parker Solar Probe—sprinkled into the Heavy’s manifest, all five of the great rocket’s flights from the West Coast have been highly classified.
It lofted four payloads to space in January, August 2013, January 2019 and most recently April of last year, all of which are thought to be KH-11 Kennen electro-optical reconnaissance/imaging satellites, reportedly weighing around 37,500 pounds (17,000 kilograms). Indeed, the Heavy’s impressive lifting capability allows it to deliver up to 63,470 pounds (28,790 kilograms) into low-Earth orbit and up to 31,350 pounds (14,220 kilograms) to geostationary altitude.
The NRO mission patch artwork for NROL-91, characteristically, is laden with much symbolism. In pride of place is the stern countenance of a U.S. military officer, whose face is modeled upon World War II Gen. Anthony C. “Nuts” McAuliffe (1898-1975).
McAuliffe was acting commander of the 101st Airborne Division, defending the city of Bastogne in Belgium’s heavily forested Ardennes, during the Battle of the Bulge. Three days before Christmas 1944, the commander of the German forces encircling Bastogne demanded the city’s unconditional surrender, threatening the “total annihilation” of U.S. forces if McAuliffe did not comply.
The general’s gritty response—“Aw, nuts!”—initially met with confusion among the German high command, who did not know what it meant. It was left to Col. Joseph Harper, who delivered the message, to offer clarification.
“In plain English,” Harper told the Germans, “it means: Go to hell!” McAuliffe’s 11,000-strong force—outnumbered five to one—stood its ground against a ferocious Luftwaffe aerial assault on Bastogne, withstanding nightly bombings until the Fourth Armored Division arrived on 26 December with reinforcements.
Remarkably, the Fourth had covered 150 miles (240 kilometers) in only 19 hours to bring relief. McAuliffe’s heroic force came to be known as the “Battered Bastards of Bastogne”.
“The combined NROL-91 team embrace the indefatigable “no surrender” attitude of the Battered Bastards of Bastogne,” noted the NRO, “and honor their selfless sacrifice and lost comrades who gave all in the defense of our freedom.” In addition to the allusion to McAuliffe, the NROL-91 patch also includes the familiar truss-structure of a World War II-era “Bailey Bridge”, symbolic of the military’s ability to adapt to changing conditions at short notice, and the silhouette of a bird of prey, illustrative of strength, endurance and a protective nature; characteristics which are “inherent,” says the NRO, “in our American warfighters”.
Finally, around the lower ribbon of the patch is a fitting quote from Abraham Lincoln’s November 1863 Gettysburg Address—“Dedicated to the Great Task Remaining”—in which the Civil War president urged his fellow citizens to take up the cause of liberty. “We dedicate this mission,” added the NRO, “to protecting our warfighters deployed in harm’s way and to the furtherance of that noble cause.”
NROL-91 is one of five missions awarded to ULA by the Space and Missile Systems Center (SMC)—now the Space Systems Command (SSC)—at Los Angeles Air Force Base, Calif., in partnership with the NRO, back in September 2019. The $1.18 billion launch services contract included NROL-44 and NROL-82, which rode Delta IV Heavies to space in December 2020 and April of last year, as well as the forthcoming NROL-68 and NROL-70 missions.
This latter pair will fly the final two Delta IV Heavy vehicles out of Cape Canaveral Space Force Station, with launches tentatively slated for 2023 and 2024. Hardware for the NROL-68 mission began arriving on the Space Coast in February of this year.
“These satellites are critical to our Intelligence Community and national security,” said Col. Robert Bongiovi, Director of Launch Enterprise, after the contract award. “These are the last remnants of our sole-source contracts. We look forward to embracing the competitive landscape that we have worked hard with industry to create.”
As is customary with classified missions, little detail of NROL-91’s launch date was revealed until just a few weeks ago. Until then, the mission retained the imprecise placeholder date of “Summer 2022”.
Last month, it was revealed that NROL-91 was tracking a 2.5-hour “launch window” on Saturday, 24 September, from 1:50 p.m. PDT (4:50 p.m. EDT) through 4:12 p.m. PDT (7:12 p.m. EDT). More recently, a definitive T-0 was set at 2:53 p.m. PDT (5:53 p.m. EDT).
The three CBCs for the Delta IV Heavy—each extending 134 feet (40.8-meters) in length—arrived at Vandenberg aboard ULA’s R/S RocketShip vessel in August of last year, to be placed in storage. They were connected together in the Horizontal Integration Facility (HIF) and the vehicle was raised to the vertical earlier this summer at SLC-6.
This was followed by integration of the DCSS and the 63-foot-long (19.2-meter) Payload Fairing (PLF), containing the classified NROL-91 cargo. Fully stacked and protected within the confines of SLC-6’s Mobile Assembly Shelter (MAS), the Delta IV Heavy stood 236 feet (72 meters) tall.
With the 30th Weather Squadron at Vandenberg predicting a 90-percent probability of acceptable weather on Saturday, Mother Nature and the technical gremlins did nothing to stand in NROL-91’s way. Yesterday, the Launch Readiness Review (LRR), led by ULA Launch Director Tom Heter III from Vandenberg’s West Coast Launch Operations Center, concluded with a definitive “Go” to proceed with the launch.
Also Friday, the 300-foot-tall (98-meter) MAS—which surrounded the Delta IV Heavy and provided weather and environmental protection during launch vehicle preparations—was retracted from its “Enclosure” position to its “Park” position. This exposed the giant rocket to the elements for the first time.
“Just your average 10-million-pound building rolling back from a 300-story-tall rocket,” tweeted Mr. Bruno with characteristics aplomb and humor. “No big deal.”
In the final hours before T-0, all personnel were cleared from SLC-6. And following a poll of the launch team, the process got underway to fuel the Heavy with 440,000 pounds (200,000 liters) of liquid oxygen and hydrogen.
This process began by chilling the tanks and ground equipment, fuel transfer lines and valves to prevent “thermal shocking” as propellants began to flow. After this process was complete, fueling began, with “fast flow” until the tanks were almost full, then transitioning into “replenishment mode”, which facilitated continuous topping to maintain flight-ready levels to replace boiled-off cryogens.
But shortly after 2:30 p.m. PDT (5:30 p.m. EDT), with clocks held in the second of two built-in “holds”—this one at the T-4 minute mark—a revised T-0 was announced. ULA announced an extension to the nominal 30-minute hold, “while the team completes post-fueling activities in the Delta IV Heavy”.
A few minutes later, Mr. Heter instructed his team to co-ordinate a new T-0 at 3:25:30 p.m. PDT (6:25:30 p.m. EDT). In support of this revised launch time, clocks resumed counting from T-4 minutes at 3:21 p.m. PDT (6:21 p.m. EDT).
Emerging from the final built-in “hold” in the countdown at T-4 minutes, ordnance aboard the rocket was armed and the CBC tanks were secured and pressurized for flight. At T-15 seconds, the sparkler-like Radial Outward Firing Igniters (ROFIs) came alive to burn off excess gases dumped through the RS-68A engine nozzles, ahead of ignition.
At staggered intervals, first the starboard CBC roared to life, then the port and center cores, and Vandenberg’s last Delta sprang away from the pad under a combined thrust of 2.1 million pounds (1 million kilograms). Launches of the Heavy are always somewhat disconcerting to the initiated in their opening seconds, as the vast quantities of hydrogen being dumped through the engines to condition them—ahead of opening the liquid oxygen valves and commanding the ignition sequence—generates a colossal fireball which appears to set the rocket’s orange-colored insulation alight as it departs the pad.
“Gotta love a rocket that is so metal, it sets itself on fire before launching into space,” tweeted ULA CEO Tory Bruno before today’s launch.
Seconds after clearing the SLC-6 tower, the Heavy began its computer-commanded pitch, roll and yaw program maneuver to establish itself onto the proper azimuth to insert NROL-91 into its highly optimized orbit. The vehicle surpassed Mach 1, eclipsing the speed of sound, about 80 seconds into ascent.
Four minutes after liftoff, their propellant depleted, the port and starboard CBCs were discarded, as the center core ramped up to full power. Its single RS-68A engine continued to burn for a further 90 seconds, before shutting down at 5.5 minutes into the flight.
The core was jettisoned shortly afterwards. This left the 45-foot-long (13.7-meter) DCSS and its single RL10-B-2 engine, which came alive with a thrust of 24,750 pounds (11,250 kilograms) to begin the process of delivering NROL-91 to its targeted operational orbit.
During the burn, the bisector halves of the payload fairing were discarded, exposing NROL-91 to the harsh environment of space for the first time. The precise duration of the RL10-B-2 “burn” was not announced.
With the roar of Delta IV Heavies now having fallen silent at Vandenberg for the final time, attention turns to the NROL-68 and NROL-70 missions from Cape Canaveral Space Force Station, Fla., whose own launches are expected in 2023 and 2024. These missions will mark the final flights of the Delta Program, whose heritage extends back over six decades.
As the last Delta IV Heavy mission out of Vandenberg, today’s flight was also, by default, the 95th and final launch of a Delta-class vehicle from the West Coast. This followed the retirement of ULA’s Delta IV Medium, which saw its last Vandenberg mission in January 2018 ahead of the full retirement of the Medium fleet in August 2019.
All told, ten members of the Delta IV family—five Mediums, five Heavies—launched from Vandenberg between June 2006 and today, nine of which were laden with classified NRO payloads and one other with a Defense Meteorological Satellite Program (DMSP) spacecraft for oceanography, meteorology and solar terrestrial physics research on behalf of the Department of Defense. Before that, earlier variants of the Delta had flown from the West Coast since October 1966, delivering a smorgasbord of payloads with objectives from weather forecasting to astronomy, ionospheric research to Earth observations and mapping and magnetospheric physics to cosmology.
Notable missions launched from Vandenberg aboard Delta vehicles included the very first Landsat, the U.S./Italian Laser Geodynamics Satellite (LAGEOS)-1 and the Cosmic Background Explorer (COBE). The much-flown Delta II logged 45 flights out of this mountain-ringed launch site between November 1995 and its retirement in January 2018 with the ICESat-2 mission.
Meanwhile, up next for ULA is the flight of the dual-stacked SES-20 and SES-21 communications satellites for Luxembourg-headquartered SES atop an Atlas V from Space Launch Complex (SLC)-41 at Cape Canaveral Space Force Station, Fla. Liftoff of the “Mighty Atlas”—flying in its rarely-seen “531” configuration, with a 17-foot-diameter (5-meter) fairing, three solid-fueled strap-on boosters and a single-engine Centaur upper stage—on ULA’s seventh mission of 2022 is expected at 5:36 p.m. EDT on 30 September.