A United Launch Alliance Delta-IV rocket is set for launch March 18 carrying the WGS-9 satellite—the ninth of 10 planned U.S. Air Force/Boeing Wideband Global Satcoms. A spectacular dusk liftoff for the Delta IV medium+ (5,4) version into a supersynchronous geosynchronous transfer orbit is planned for 7:44 p.m. EDT, at the opening of a 74 minute launch window that closes at 8:58 p.m. EDT.
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But the launch follows an unprecedented month where both of ULA’s Delta and Atlas launchers were temporarily grounded by first stage engine problems at Cape Canaveral.
With more than 10 years of Evolved Expendable Launch vehicle experience under its belt and a near 100% success rate, it is highly unusual for technical problems to delay a ULA launch, let alone two launches involving Atlas and Delta rocket propulsion systems at the same time.
A problem with the Aerojet Rocketdyne RS-68A engine in the WGS-9 Delta-IV on Launch Complex 37 delayed the critical military satcom launch from March 8 to no earlier than 7:44-8:58 p.m. EDT March 18. Neither ULA or the Air Force would comment on what the nature of the RS-68 engine problem was, although it took several days to resolve.
Meanwhile a hydraulics problem with the Russian Energomash RD-180 engine in the first stage of the Atlas-V mounted on Launch Complex 41, delayed the launch of the OA-7 Cygnus International Space Station resupply mission from March 9 to no earlier than 10:11 p.m. EST March 21.
Ironically, a problem with the ULA Atlas-V Mixture Ratio Control Valve in the oxygen/kerosene RD-180 powering the OA-6 Cygnus to orbit almost exactly a year ago on March 22, 2016, resulted in an early shutdown of that flight’s first stage, forcing the mission’s Centaur upper stage to burn longer to place that cargo craft into a proper orbit for rendezvous with the ISS.
“There is always a tremendous amount of pressure to launch these missions successfully,” said Laura Maginnis, United Launch Alliance vice president for Government Satellite Launch Operations.
“There are thousands of details that have to come together and a lot of precision analysis and focused teamwork that needs to come together at the right time and in the right way for successful testing and launch,” she said at a prelaunch briefing where no mention of the RS-68 issue was raised.
This particular WGS mission is especially noteworthy because the $424 million spacecraft costs have been shared between the U.S., Canada, Denmark, Luxembourg, The Netherlands and New Zealand. This broadens further the international participation in the program beyond Australia which paid for the entire WGS-6 satellite.
The percentage of payment from each country determines the amount of WGS constellation access each country receives. All five gained access to the system starting in 2012 when the cooperation agreement was signed. Canada leads the group with a contribution of $337 million to the program.
The mission was also selected by the USAF to commemorate the 70th anniversary of the U.S. Air Force. The USAF was formed into a separate service in 1947, after throughout World War 1 and World War 2 being part of the U.S. Army.
The significance of the anniversary and international participation in the flight are highlighted by the nose art on the 47 x 17 ft. launch shroud on the 217 ft. tall rocket. In addition, the mission poster for the flight depicts WGS-9’s Delta IV during climbout above a diamond formation of nine USAF F-22 fighters.
Each 13,200 lb. WGS satellite “is a key element in helping the Air Force win in the atmosphere, space and cyberspace domains and we are honored to be flying the 50th anniversary logo on our Delta IV fairing,” said Robert E. Tarleton Jr., Director of the MILSATCOM Systems Directorate at the Air Force Space and Missile Systems Center at Los Angeles AFB, Calif.
Only one more satellite WGS-10 remains to be launched, and that mission is planned to fly from Cape Canaveral on the Delta-IV too, late in 2018.
“There was some interest among other nations for us to build a WGS-11, but that never materialized,” Tarleton said.
WGS satellites are important elements of a new high-capacity satellite communications system providing enhanced communications capabilities to our troops in the field. WGS has 19 independent coverage areas, 18 of which can be positioned throughout its field-of-view. This includes eight steerable/shapeable X-band beams formed by separate transmit/receive phased arrays; 10 Ka-band beams served by independently steerable diplexed antennas; and one transmit/receive X-band Earth-coverage beam.
WGS can tailor coverage areas and connect X-band and Ka-band users anywhere within its field-of-view. The X-band phased array antenna enables anti-jam functionality without sacrificing performance.
In addition, the WGS constellation is supplemented by four older but nuclear hardened DSCS lll Defense Satellite Communications System spacecraft. A total of 14 DSCS III’s were launched between the early 1980s and 2003.
It will take about 5 months of checkout and spacecraft maneuvering before WGS-9 goes into service at a secret geosynchronous orbit location. WGS-8 launched last December has just reached its operational station.
Although the wideband WGS satellites are the most powerful of all military satcom, their capability is dwarfed by advanced commercial satellites.
Each WGS has a service life of 14 years, with the initial three spacecraft launched in 2007 and 2009. According to Tarleton, the Pentagon is starting a Wideband Communications Services Analysis to determine the nature of follow on spacecraft to replace the WGS constellation starting about 2029. He said a commercial lease arrangement is one option to an all military replacement design. The WGS bus itself is based on the commercial Boeing BSS-702HP design, but WGS satellites do not carry non military related commercial traffic.
Going the commercial lease route is a significant factor for the future. According to Andrew Ruszkowski, Chief Commercial Officer at the satellite firm XTAR, “the company’s own commercial satellite, XTAR-EUR at 29 east long. was launched in 2005 and flies with an 864 MHz X-band payload with a potential throughput of 2.4 Gbps. This is equivalent to WGS, even without a Ka-band payload.” he said in a company blog.
“A more recent example is ViaSat-1 launched in 2011 and currently operating at 115.1 west long.
ViaSat-1 is the first in a growing category of commercial birds often referred to as High Throughput Satellites,” he said in the blog. “It provides an astonishing 140 Gbps of potential throughput. That’s 58 times greater than WGS claims!,” he said.
In the same blog Todd Dudley a retired Navy F-18 pilot and XTAR’s director of Foreign Military Sales and International Business Development notes the latest WGS satellite WGS-8 and soon WGS-9 “Mark a technological leap forward for the WGS constellation, bringing more X- (and Ka-band) capacity to the Department of Defense. X-band is also an important part of NATO’s own capabilities package for satellite communications.”
“There is a reason that the Department of Defense and NATO have invested so heavily in X-band: It provides high-throughput, virtually weatherproof satellite communications that excels with high-mobility, lightweight applications ranging from forward tactical and Special Force units, to maritime communications, to airborne intelligence, surveillance and reconnaissance and UAV assets. For these types of applications, X-band in fact provides substantially better service than Ka-band. No wonder X-band is a key component of the Department of Defense’s and NATO’s SATCOM architectures,” says Dudley.
With all times here approximate, key moments in the 42 min. ascent into about a 27,575 x 240 mi supersynchronous transfer orbit are:
- 46 seconds: The rapidly climbing vehicle will throttle back momentarily to go through max-Q.
- 90 seconds: The four solids burn out and separate in pairs just past the 90 sec. mark in the ascent.
- 3 minutes 14 seconds: The nose fairing will split into two halves and separate from around the massive satellite.
- 4 minutes 2 seconds: The burnout and separation of the first stage and its RS-68 engine will occur as the vehicle flies north of the Bahamas.
- 4 minutes 15 seconds: The Delta IV’s cryogenic second stage with an Aerojet Rocketdyne 24,750 lb. thrust RL10B-2 engine will be ignited for a nearly 16 min. firing to power the vehicle across the Atlantic at 17,500 mph at 110-120 naut mi. altitude.
- 19 min. 51 seconds: This first of two upper stage firings will end with the stage and satellite passing just south of Cape Verde off the West African bulge. The vehicle will then coast south down the West African coast.
- 29 min. 27 seconds: The RL10 will be ignited for the second time for about 3 min. 18 sec, until 33 minutes into the flight where cutoff will occur over south central Africa. The vehicle will then coast across this narrowest part of Africa until it exits the southeast African coast near Madagascar.
- 42 minutes: Spacecraft separation.
Over the next several weeks WGS-9 will use its onboard bi-propellant propulsion system to raise perigee and lower apogee to its approximate 22,300 mi. geosynchronous orbit operational altitude.
The Aerojet R-4D 110 lb. thrust engine that will perform the maneuvers is powered by nitrogen tetroxide and monomethyl hydrazine (UDMH), and was originally designed by Marquardt as the attitude control engines used on the Apollo Command/Service module and Lunar Module.
Propellant consumed during four perigee and four apogee burns will reduce the spacecraft’s mass to 7,600 lb.
Xenon thrusters will then be used for maneuvering and station keeping in geosynchronous orbit.
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