Screenshot from ULA Webcast of the launch of WGS-8. Why do We always take off in darkness?
Mission Rundown: ULA - Delta IV M+5,4 - WGS-8
Written: December 27, 2022
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United Launch Alliance (ULA) has launched a Delta IV Medium rocket on December 7, Wednesday evening, carrying the eighth satellite in the US Air Force’s Wideband Global Satcom system. The rocket lifted off with WGS-8 from Cape Canaveral Air Force Station’s SLC-37B pad at 18:52 EST - 23:52 UTC.
Wideband Global Satcom 8 (WGS-8), the eighth of ten satellites in the Wideband Global Satcom constellation, is a communications satellite designed to provide secure military communications for the United States Air Force and its national and international partners.
United Launch Alliance (ULA) was responsible for conducting Wednesday’s launch. Using a Delta IV Medium+(5,4) rocket flying from Space Launch Complex 37B at the Cape Canaveral Air Force Station in Florida, the mission lasted forty-one minutes and 43.6 seconds from liftoff to spacecraft separation.
The launch of WGS-8 comes a week after ULA celebrated its tenth anniversary; the company was founded on 1 December 2006 through the amalgamation of the launch vehicle divisions of Lockheed Martin – the original manufacturer of the Atlas V – and Boeing, who developed the Delta IV and also manufactured the earlier Delta II.
The WGS-8 launch was the 34th flight of all the Delta IV, and the 27th to be conducted by United Launch Alliance. The remainder of ULA’s launches have been made by twenty-eight Delta II vehicles and 59 Atlas V rockets. As a main provider of launch services to the US Government, ULA’s customers have primarily been the US military and NASA.
The WGS-8 Payload
The follow-on satellites, WGS-7 to WGS-10, were contracted between September 2011 and July 2012, with WGS-9 being funded through contributions from Canada, the Netherlands, Denmark, Luxembourg and New Zealand as the program gained international partners.
Wideband Global Satcom spacecraft are based around Boeing’s BSS-702HP satellite bus. Operating in geosynchronous orbit, each spacecraft has a design lifespan of fourteen years. Fuelled, the satellite has a mass of 5,987 kilograms (13,200 lb). In 2012, the cost of the WGS-8 spacecraft was estimated at $353.9 million.
WGS satellites are important elements of a high-capacity satellite communications system providing enhanced communications capabilities to America's troops in the field for the next decade and beyond. WGS enables more robust and flexible execution of Command and Control, Communications Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR), as well as battle management and combat support information functions. The WGS constellation augments the existing service available through the UHF Follow-on satellite by providing enhanced information broadcast capabilities.
With a new state-of-the-art digital channelizer, WGS-8 will increase communication capacity by approximately 45 percent more than previous WGS satellites. The WGS constellation is the nation’s highest-capacity military communication system, providing a quantum leap in communication capability for the U.S. military and allied forces.
This vital asset continually collects and routes real-time data through all X-band and Ka-band terminal types in support of a wide variety of missions, from search and rescue efforts to military operations.
The Delta IV M+5,4 Launch
Delta 376’s launch began with first stage ignition, five seconds ahead of the planned liftoff. Once the countdown got to zero, the solid rocket motors ignited and Delta 376 began its ascent towards orbit. Seven seconds after liftoff the vehicle began a series of pitch, yaw and roll maneuvers to put itself on course for the ascent to orbit. Delta flew a launch azimuth of 93.46 degrees, East out over the Atlantic.
Climbing through Earth’s atmosphere, Delta 376 passed through the area of maximum dynamic pressure, or Max-Q, 46.2 seconds into flight.
The first pair of solid motors burned out 91.6 seconds after liftoff, followed by the second pair a second and a half later. The spent casings remained attached for a few seconds, before being jettisoned in pairs 2.4 seconds apart, beginning 100 seconds after launch.
Three minutes and 14.4 seconds into Wednesday’s mission, the payload fairing separated from around the WGS-8 satellite at the nose of the Delta IV. The first stage continued to burn until T+ three minutes and 56 seconds, at which point the RS-68A was shut down. Six seconds later the spent Common Booster Core separated from the vehicle.
The Delta IV second stage, or Delta Cryogenic Second Stage (DCSS) is powered by a single RL10B-2 engine. This has an extendible nozzle which deployed after separation. The engine ignited thirteen seconds after staging to begin the first of two second stage burns. The first burn lasted fifteen minutes and 36.8 seconds.
The coast phase between the end of the first upper stage burn, and the beginning of the second, lasted nine minutes and 34.8 seconds. Following the coast, the RL10 engine restarted for three minutes and seven seconds, to reach the target deployment orbit for WGS-8.
WGS-8 flight plan with DCSS orbit insertion burn cutoff at 7. GTO burn is 8-9. Deployment is 10
The satellite separate, at 41 minutes, 43.6 seconds mission elapsed time, into a 435 by 44,378 kilometer (270 x 27,575 miles; 235 x 23,962 nautical miles) geosynchronous transfer orbit at an inclination of 27 degrees. Following spacecraft separation, the DCSS performed a third short burn to deorbit itself.
The Delta IV M+5,4 rocket
Wednesday’s launch used Delta 376. Its Medium+(5,4), or M+(5,4) configuration consisted of a single Common Booster Core (CBC) first stage, a five-meter diameter Delta Cryogenic Second Stage and four GEM-60 solid rocket motors to provide additional thrust at liftoff.
WGS-8 will mark ULA’s 70th national security launch since the company was founded in 2006. This is the sixth flight in the Medium+ (5,4) configuration; all launches in this configuration were WGS missions.
Both the Common Booster Core and the Delta Cryogenic Second Stage have liquid hydrogen as the fuel and liquid oxygen as the oxidizer.
Standing 217 feet tall and weighing 881,997 pounds, the upgraded Delta IV Medium+ (5,4) and its predecessor, the one with the weaker RS-68 engine, have exclusively launched WGS satellites since 2009. At liftoff, the launch vehicle will produce 1,702,974 pounds of thrust, which is about as much as the Falcon 9 rocket.
Delta IV Medium+5,4 split in its major parts. The DCSS will deliver WGS-8 into its GTO target
The 4 strap on GEM 60 boosters from Orbital ATK each produce 185,800 lbf at liftoff, burning HTBP propellant for 91 to 93 seconds for a total cumulative booster thrust at liftoff of 743,200 lbf — increasing to 1,124,000 lbf during flight.
At liftoff, the Common Booster Core's RS-68A engine provides 705,250 lbf and burns LH2 and LOX for 245 seconds (4 minutes 5 seconds).
Total thrust at liftoff of the Delta IV M+ (5,4) is 1,448,450 lbf. During flight, when the SRMs reach maximum thrust, the total combined thrust of the vehicle reaches 1,829,250 lbf.
The second stage, the Delta Cryogenic Second Stage (DCSS), burns LH2 and LOX via a single RL10-B-2 engine that delivers 24,750 lbf.
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