The Space Coast will be greeted by a rare spectacle on Friday evening (15 March), when United Launch Alliance (ULA) lofts the second-to-last member of its “single-stick” Delta IV fleet of boosters from Space Launch Complex (SLC)-37B at Cape Canaveral Air Force Station, Fla. The almost-six-decade-old pad—which last saw service to launch NASA’s Parker Solar Probe in August 2018—will reverberate to more than 1.8 million pounds (810,000 kg) of thrust from the Common Booster Core (CBC) and four strap-on solid-fueled rockets of the Delta IV Medium+ (5,4). Liftoff of ULA’s second mission of 2019 is scheduled for 6:56 p.m. EDT, at the opening of a 129-minute “window”, which closes at 9:05 p.m. Assuming a successful launch, the tenth Wideband Global Satcom (WGS-10) satellite will be released into supersynchronous orbit about 42 minutes into the flight, setting it up for a minimum 14 years supporting U.S. and allied warfighters.
In keeping with tradition, this particular Delta IV vehicle is dedicated to a late ULA employee; in this case, Kurt Huschle, who held critical roles during a 30-year aerospace career and was the electrical installations lead for the Delta IV.
Alongside its fleet of Atlas V vehicles, ULA has steadily phased-out the expensive single-stick variants of the Delta family in recent years. After three decades of near-impeccable service, the Delta II launched its last mission back in September 2018. Following the final mission of the Delta IV Medium+ (5,4) with WGS-10—configured with a 16-foot-wide (5-meter) payload fairing and four Northrop Grumman-built GEM-60 solid-fueled boosters—the sole remaining single-stick Delta IV, the Medium+ (4,2), with two strap-on GEM-60s, will fly its swansong in July 2019 with the second Global Positioning System (GPS) Block III satellite.
“ULA made the decision to retire the Delta IV Medium launch vehicle when our National Security Space customer decided to compete missions in 2015,” explained ULA director and general manager of launch operations Tony Taliancich, in comments provided to AmericaSpace. “Prior to the acquisition strategy change, ULA was required by the government to maintain two families of launch vehicles to meet assured access to space policy requirements. In a competitive environment, ULA must favor its lowest-cost product to meet the market requirements. Maintaining multiple product lines would lead to lower launch rates and higher costs.”
ULA will henceforth rely upon the Atlas V, Delta IV Heavy and its in-development Vulcan-Centaur heavylifter, which is waiting in the wings for a maiden voyage, no sooner than spring 2021.
“ULA expects that flying out the Delta IV medium and transitioning to Vulcan Centaur will provide the lowest cost, most reliable support to our launch customers,” added Taliancich. “ULA will continue flying the Delta IV heavy launch vehicle as long as it is required by our customers. Once transitioned to Vulcan, we will be able to provide a single stick Vulcan that can meet Delta IV heavy mission requirements at a lower price.”
“Our manifest remains flexible in 2019 to accommodate our customer requirements,” says Taliancich. “2019 is a busy year for us as we prepare for scheduled launches and a very busy 2020 manifest. In our factory alone we will be working at a record setting manufacturing pace with 30 boosters in production during 2019 and 2020.”
First flown in December 2009, the Medium+ (5,4) has the potential to haul up to 30,250 pounds (13,370 kg) to low-Earth orbit and as much as 15,109 pounds (6,890 kg) to geostationary altitude. Its seven previous launches—including its most recent flight, in March 2017—have lofted all but two members of the Boeing-built WGS constellation of high-capacity X-band/Ka-band military communications satellites, which enhance the capabilities of U.S., Australian and Canadian armed forces through additional bandwidth for tactical command and control, communications, intelligence, surveillance and reconnaissance, battlefield management and combat-support.
Three “Block 1” members of the fleet—WGS-1, WGS-2 and WGS-3—were launched into orbit between October 2007 and December 2009, providing complete strategic coverage of the Pacific and Atlantic Oceans and support U.S. Central Command in Afghanistan, Iraq and western Asia. This was followed by the three-member “Block 2” fleet of WGS-4, WGS-5 and WGS-6, launched between January 2012 and August 2013, by which time Boeing was already working on a $182 million contract to develop four “Block 2 follow-on” satellites, the first of which (WGS-7) rose to orbit in July 2015.
Two more Block 2 follow-ons were launched in December 2016 and March 2017, with WGS-10 closing out a ten-strong fleet, which is operated by the Air Force Space and Missile Systems Center (SMC) at Los Angeles Air Force Base, Calif. Last year, Congress provided $600 million funding for two additional WGS satellites, whose launch dates and vehicles have yet to be announced.
Each satellite is based on Boeing’s BSS-702 “bus”, with a reported mass of around 13,200 pounds (6,000 kg) and the capability to provide more than 11 kilowatts of electrical power at the end of its 14-year operational lifetime. The WGS network has evolved considerably through its three phases, with enhanced levels of instantaneous switchable bandwidth and broader capacity for tactical users, as well as switchable radio frequency bypass functionality to support the transmission of ultra-high bandwidth airborne intelligence, surveillance and reconnaissance imagery via unmanned aerial vehicles.
Whereas the Block 1 and Block 2 satellites could instantaneously filter and downlink up to 4.410 GHz, their Block 2 follow-on variants can achieve up to 8.088 GHz. When WGS-10 was ordered by the Air Force in July 2012, Boeing received contracts to incorporate wideband digital channelizers aboard WGS-8, WGS-9 and WGS-10 to afford a 90-percent improvement in bandwidth. The WGS design includes 19 independent coverage areas to serve U.S. and allied warfighters operating between 65 degrees North and South latitudes, with eight steerable X-band beams, ten steerable Ka-band bneams and a single X-band Earth-coverage beam. Depending upon the mix of ground terminals, data rates and modulation and coding schemes utilized, a single WGS can support over 6 Gbps and—for the more recent satellites, with advanced digital channelizers—can handle over 11 Gbps.
Built at ULA’s facility in Decatur, Ala., the Common Booster Core (CBC) for the Delta IV Medium+ (5,4) was delivered to Cape Canaveral in July 2018, by means of the M/C Delta Mariner cargo vessel for final integration in the seven-story Horizontal Integration Facility (HIF) at SLC-37B. It was mated to its Delta Cryogenic Second Stage (DCSS) and on 24 January the 170-foot-long (51.8-meter) stack was rolled out to the SLC-37B pad surface and raised to the vertical within the Mobile Service Tower (MST).
“Cradle-like pallets holding the rocket were secured to the Fixed Pad Erector on the pad’s surface,” ULA noted. “Two hydraulic pistons rotated the orange-and-white rocket vertically onto the pad’s launch table…achieving the Launch Vehicle On-Stand (LVOS) pre-launch milestone.” A crane was then utilized to install the four GEM-60 boosters—each of which stands 53 feet (16.1 meters) tall—around the CBC’s base, in a multi-day operation which concluded on 11 February.
More recently, at the end of last month, the WGS-10 payload itself—encapsulated within its 47-foot-long (14.3-meter) payload fairing—was mounted atop the stack, raising the last Delta IV Medium+ (5,4) to a total height of 218 feet (66.4 meters). “The payload was hauled by a motorized KAMAG Elevating Platform Transporter (EPT) that provided hydraulic leveling and precision positioning capabilities along the route,” ULA noted in an update. “The EPT also towed a Portable Environmental Control System (PECS) trailer to supply conditioned air to the fairing during the trip.”
As February rolled into March, an Integrated Systems Test (IST) validated the electrical compatibility of the entire rocket and payload, ahead of an extensive flight-readiness review. An on-time launch on Friday evening will commence with the ignition of the RS-68A engine of the CBC, followed by all four GEM-60s. The strap-on boosters will be jettisoned about 100 seconds into flight, with the RS-68A shutting down and the CBC separating at four minutes. The DCSS will then pick up the baton, performing two discrete “burns” of its RL-10 engine to deliver WGS-10 into supersynchronous transfer orbit, with an apogee of 27,571 miles (44,372 km) and a perigee of 270 miles (435 km).
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