For the 29th and final time, a United Launch Alliance (ULA) Delta IV Medium booster took flight this morning (Thursday, 22 August) to deliver the second Block III Global Positioning System (GPS) satellite to Medium Earth Orbit (MEO) for the U.S. Air Force. The familiar, orange-and-white rocket—flying with a 13-foot-wide (4-meter) payload fairing and two strap-on, solid-fueled boosters—departed Space Launch Complex (SLC)-37B at Cape Canaveral Air Force Station, Fla., at 9 a.m. EDT, right on the opening of today’s 27-minute “window”.
As previously detailed by AmericaSpace, the expensive “single-stick” Delta IV Medium product-line is being retired in favor of the Atlas V, the forthcoming Vulcan-Centaur heavylifter—which won contracts earlier this month to launch six Sierra Nevada Corp. Dream Chaser cargo flights to the International Space Station (ISS) and Astrobotic’s Peregrine lunar lander—and, for the next few years at least, the behemoth Delta IV Heavy.
By a strange quirk, today’s flight flew in exactly the same configuration—the so-called Medium+ (4,2)—as was employed on the very first Delta IV mission, way back in November 2002, which deployed the Eutelsat W5 communications satellite to geostationary altitude. Since then, this particular configuration has flown 14 more times, more than any other Delta IV variant, delivering three Geostationary Operational Environmental Satellites (GOES) for weather monitoring, two classified reconnaissance/intelligence sentinels for the National Reconnaissance Office (NRO), a pair of Air Force Space Command mixed payloads, six GPS Block II missions and, with today’s launch, a single GPS Block III.
The 134-foot-tall (40.8-meter) Common Booster Core (CBC) for the mission arrived at the Cape last November from ULA’s 1.5-million-square-foot (140,000-square-meter) facility in Decatur, Ala., via the MV Delta Mariner cargo ship. The 29-foot-long (8.8-meter) Delta Cryogenic Second Stage (DCSS) was mated to the CBC last April in the Horizontal Integration Facility (HIF) at SLC-37B and in late May the complete vehicle was transported to the pad and hydraulically elevated to vertical by the Fixed Pad Erector (FPE).
This action concluded the Launch Vehicle On-Stand (LVOS) milestone, after which the two Graphite Epoxy Motor (GEM)-60 strap-on boosters—each standing over five stories tall—were installed at its base over the period 31 May through 3 June. The bulbous payload fairing with the GPS III-02 satellite, named “Magellan” in honor of the 16th-century Portuguese explorer who first circumnavigated the Earth, was installed shortly thereafter to top-off the stack.
GPS III-02 is part of a next-generation network of global positioning, velocity and timing satellites, bound for Medium Earth Orbit (MEO). The Air Force awarded a $1.4 billion contract to Lockheed Martin in May 2008 to develop Block III, which will eventually comprise up to 32 satellites, the first of which was launched by SpaceX in December 2018 after several years of payload problems. GPS III-02 was structurally complete—with its system module, propulsion core and antenna deck fully integrated—by June 2017, after which it was put through several months of punishing environmental, acoustic and Thermal Vacuum (TVAC) tests. In August 2018, the satellite was declared “Available for Launch” by the Air Force and in March of this year it was shipped aboard a C-17 Globemaster III heavylift aircraft from Buckley Air Force Base in Aurora, Colo., to Cape Canaveral Air Force Station for final pre-launch preparations.
However, GPS III-02’s planned launch on 25 July was missed, when ULA revealed “an anomaly during component testing at a supplier which has created a cross-over concern”. This required further evaluation and additional time to replace and re-test the component, as part of ULA’s drive to maintain its 100-percent mission-success record. Launch was correspondingly postponed until no sooner than 22 August. In readiness for the revised launch attempt, the payload fairing holding GPS III-02 was transferred to SLC-37B overnight on 1 August and hoisted atop the Delta IV Medium+ (4,2), raising the stack’s total height to over 207 feet (63 meters).
Earlier this week, ULA Launch Director Paul Aragon oversaw the Launch Readiness Review (LRR), which verified that all was well for a Thursday launch attempt. “Leaders from ULA and the Air Force assessed all aspects If mission readiness, discussed the status of pre-flight processing work, heard technical overviews of the countdown and flight and previewed the weather forecast,” ULA noted in an update on its website. “At the conclusion of the meeting, the managers were polled, gave a unanimous “ready” for launch and then signed the Launch Readiness Certificate.”
With 500 times the transmitting power of current GPS systems, Block III benefits from improved navigational warfare capabilities, with three times better accuracy and eight times better anti-jamming functionality. This enables the satellites to shut off GPS service to limited geographical locations, whilst maintaining uninterrupted provision for U.S. and allied forces. Block III features a cross-linked command and control architecture, which allows the entire constellation to be updated from a single ground station. Furthermore, the new satellites will showcase a new spot-beam capability for enhanced military (“M-Code”) coverage and increased resistance to hostil jamming.
All told, these enhancements are expected to produce improved accuracy and assured availability for military and civilian users worldwide. Based upon Lockheed Martin’s tried-and-true A2100 “bus”, whose modular framework can supply 15 kilowatts of electrical power via high-efficiency solar cells, radiation-cooled traveling-wave-tube assemblies and improved heat-pipe design, each GPS Block III weighs around 8,500 pounds (3,900 kg). The A2100’s 15-year operational life span represents a 25-percent leap over the GPS IIF satellites currently aloft.
Weather conditions steadily improved throughout the week, with an 80-percent likelihood of acceptable conditions at T-0. “High pressure in the western Atlantic will stretch toward the peninsula this week and generate light south to southeast winds,” noted the 45th Weather Squadron in its L-2 briefing on Tuesday morning. “As a result, afternoon sea breeze driven showers and thunderstorms will concentrate over the mainland (west of the Spaceport). Drier air will draw nearer tomorrow and Thursday, bringing a lower than usual coverage of showers and storms.”
It was noted that “another increase in moisture” would lead to a slight deterioration in the weather to 70-percent-favorable in the event of a 24-hour scrub to Friday. “Thus, the primary concerns during the launch window are the Cumulus Cloud Rule and Flight Through Precipitation,” continued the forecast. “At this time, the next increase in moisture is forecast to occur after Friday morning, therefore the primary concerns for a 24-hour delay remain the same.”
Today’s mission marked only the third ULA flight of 2019, coming on the heels of a Delta IV Heavy in January to launch NROL-71 for the National Reconnaissance Office and the swansong of the Delta IV Medium+ in its (5,4) configuration, with a 16-foot-wide (5-meter) fairing and four strap-on boosters, back in March. The remainder of the year anticipates several Atlas V missions, with five originally booked for this year—including the unpiloted test-flight and inaugural crewed mission of Boeing’s CST-100 Starliner to the International Space Station (ISS)—although it remains to be seen how the manifest will pan out.
The first Atlas V flight of the year, laden with the fifth Advanced Extremely High Frequency (AEHF-5) military communications satellite, was originally scheduled to launch in June, but was postponed into mid-July due to a vehicle battery failure and eventually flew on 8 August. Current plans call for the first unpiloted Starliner to fly later in the fall, utilizing the first Dual-Engine Centaur (DEC), before NASA astronauts Mike Fincke and Nicole Mann, teamed with former shuttle commander and Boeing test pilot Chris Ferguson, launch on its first crewed mission as soon as late November.
Following the LRR, the Mobile Service Tower (MST) at SLC-37B was retracted a few hours prior to T-0. The multi-faceted countdown emerged from its final built-in hold at T-4 minutes and, passing one minute, the Range Operations Co-ordinator (ROC) declared that the Eastern Range was “Green”, with no remaining constraints to launch. At T-14 seconds, the Radial Outward Firing Igniters (ROFIs) were activated, sizzling like sparklers to burn off excess hydrogen lingering under the Delta IV’s single RS-68A main engine. Shortly before T-0, the liquid oxygen and hydrogen valves opened and the engine came to life, spewing 705,000 pounds (320,000 kg) of propulsive yield.
At zero, the twin GEM-60 boosters also ignited with their familiar staccato crackle, providing the muscle for the Delta IV Medium booster to punch away from SLC-37B and depart Earth for the final time. Shortly after clearing the pad, the rocket initiated a combined pitch, roll and yaw program maneuver to establish itself onto the proper azimuth to inject GPS III-02 into Medium Earth Orbit (MEO) at an inclination of 55 degrees to the equator. Following the separation of the CBC at four minutes into flight, the RL-10B-2 engine of the DCSS ignited for two long “burns”—the first lasting nine minutes, the second just four minutes—to continue the boost of its precious payload into orbit. Separation of GPS III-02 occurred a little under two hours into flight.