Cape Canaveral Air Force Station was the scene of an important launch on January 19th, 2012. Having previously proven itself three times for this series of satellites, United Launch Alliance (ULA) managed the Boeing built, Worldwide Global SATCOM satellite number four. With a dramatic push away from Earth, the satellite successfully slipped into its orbital slot aboard a Delta IV vehicle, empowered by Alliance Techsystems and Pratt & Whitney engines. This was actually the second launch by ULA using the Delta IV, with two previous missions completed with the Atlas V launch vehicle. Noteworthy is that ULA can now launch satellites with more alacrity, as the Company can use both the Atlas V and the Delta IV for such tasks.

On January 19th, 2011, the first signals from WGS-4 were received, indicating the satellite’s health is as anticipated, and orbital maneuvers and ops testing were started. Ground stations in Dongara, Australia, as well as Boeing’s Mission Control Center in El Segundo, California, all received initial contact and confirmed that the satellite is functioning as expected.

The Boeing Build
For Boeing, the Wideband Global SATCOM Four (WGS-4) is worthy of special note. The satellite will, of course, support anywhere MILSATCOM is critically needed for our nation’s warfighters. However, WGS-4 is also the only military satellite capable of simultaneous X- and Ka-band communications. Network support for tactical C4ISR is therefore, enabled.

The stated purpose of the WGS satellites is to provide broadband communications connectivity for U.S. and allied warfighters all around the globe. To ensure such is enabled, Boeing invested in phased antenna arrays as well as digital signal processing. The end result is the implementation of the 4Cs for even the most demanding ops... capacity, control, connectivity and capacity.

Additionally, WGS pumps up data processing to more than 3.6 gigabits per second — 10x that of previous MILSATCOM satellites. CommLinks are supported through 500MHz of X-band and 1GHz of Ka-band spectrum that can take advantage of more than 4.8GHz of usable comms bandwidth through the reuse of frequency and digital channelization. The latter divides uplink bandwidth into some 1,900 independently routable sub-channels, resulting in extremely efficient bandwidth use by the satellite.

There are four WGS Operations Centers (WSOCs), all using Boeing provided control elements via software and databases from Boeing, ITT and Raytheon. Actual platform control is handled by the 3rd Space Operations Squadron (3 SOPS) located at Schriever Air Force Base using mission software that was designed by Boeing in tandem with the U.S.A.F.’s CCS-C, which is fielded by Kratos Defense and Security Systems’ subsidiary, Integral Systems.

Boeing has also just received authorization from the U.S. Air Force to produce and launch the eighth and ninth WGS satellites. The WGS-9 authorization and the WGS-8 production option, which was authorized last month, have a combined value of $673 million and are part of the $1.09 billion contract modification announced by the Air Force in September 2011. WGS-8 and -9 will join four other satellites that are part of the Block II series, which adds a switchable radio frequency bypass that enables the transmission of airborne intelligence, surveillance and reconnaissance imagery at data rates approximately three times greater than the rates available on Block I satellites.

New Partnerships
Just signed is a new WGS international partnership between the United States, Canada, Denmark, Luxembourg, the Netherlands and New Zealand. This partnership, based upon the U.S. and Australian WGS-6 Memorandum of Understanding that was signed in November of 2007, will allow the Partners immediate access to existing WGS satellites. Additionally, the funding by the Partners will enable expansion of the ninth satellite, WGS-9. Resource allocations will be based upon ongoing satellite development and the operational status of the WGS System, for WGS 1 to 9. Specific requirements needed by each Partner will be addressed over time. The costs for each nation, with a total ceiling contribution of up to US$10.530 billion, are:

Canada — $396.5M
Denmark — $62M
Luxembourg — $49.6M
The Netherlands — $49.6M
New Zealand — $62M
USA — $9,910.6M

The Partnership’s first steering committee meeting was held in Washington, DC, on January 17th of this year.

Boeing’s 702HP Platform
The WGS satellites are built upon Boeing’s 702HP satellite platform with its xenon-ion propulsion system (XIPS), solar cells comprised of triple-junction gallium arsenide, and even deployable radiators with flexible heat pipes that allow for a far cooler and more stable environment for the bus and the payload. And why is such important? Because performance variations that could occur over the life of the satellite are reduced and component reliability is increased.

Boeing announced the 702 Series in October of 1995. In 2009, the Company introduced a mid-ranged version, the 702MP for “mid-power.” At that time, the legacy Boeing 702, which has continuously evolved, was designated the Boeing 702HP, the HP an acronym for “high-power,” which evolved from the proven 601 and 601HP (high-power) spacecraft.

The first Boeing 702HP satellite was launched in 1999. The satellite can carry more than 100 high-power transponders and deliver any communications frequencies that customers request. The Boeing 702 design is directly responsive to what customers said they wanted in a communications satellite, starting with lower cost and including high reliability with a broad spectrum of modularity. A prime example of such modularity is the payload/bus integration. After the payload is tailored to customer specifications, the payload module mounts to the common bus module at only four locations and with only six electrical connectors. This design simplicity confers major advantages. First, nonrecurring program costs are reduced, as the bus does not need to be changed for every payload, and payloads can be freely tailored without affecting the bus. Second, the design permits significantly faster parallel bus and payload processing. This leads to the third advantage: a short production schedule.

Additional efficiencies are derived from the 702’s XIPS, which is 10 times more effective than conventional liquid fuel systems. Four 25cm thrusters provide economical stationkeeping, requiring only 5kg of fuel per year, a fraction of what bipropellant or arcjet systems consume. Using XIPS for final orbit insertion conserves even more mass as when compared to using an on-board liquid apogee engine. Customers can apply the weight savings to substantially increase the revenue-generating payload at a small marginal cost, to prolong service life, or to change to a less expensive launch vehicle (when cost is based on satellite mass). The Boeing 702HP also incorporates a bipropellant propulsion system, which can lift the satellite into final orbit after separation from the launch vehicle.

Dual and triple-junction gallium arsenide solar cells, developed by Spectrolab (a Boeing subsidiary) support power ranges of up to 18kW. The Boeing 702HP separates the bus and payload thermal environments and substantially enlarged the heat radiators to achieve a cooler, more stable thermal environment for both bus and payload. This increases unit reliability over service life. Deployable radiators use flexible heat pipes, which increase packageable radiator area. Further thermal control occurs through passive primary rejection via heat pipes.

The Boeing 702HP geomobile satellite system features a 12.25m deployable antenna as well as onboard digital signal processing and beamforming. This satellite system integrates a Boeing geosynchronous-orbit satellite with a ground segment and a user terminal segment. The baseline Boeing 702 is compatible with several launch vehicles: Delta IV, Atlas V, Ariane 5, Proton, and Sea Launch.

The ULA Launch
The WGS-4 mission was initiated from Space Launch Complex 37 (SLC-37) at Cape Canaveral Air Force Station (CCAFS), Florida on a Delta IV Medium+ (5,4) vehicle. The two-burn mission flew an easterly trajectory from SLC-37 with an approximately 101 degree flight azimuth. The separation event released the WGS-4 satellite into a super synchronous transfer orbit with a 237 nautical mile (nmi) perigee, an apogee radius of approximately 36,108 nmi, and an approximately 24 degree inclination.

Developed in partnership with the U.S. Air Force (U.S.A.F.) Evolved Expendable Launch Vehicle (EELV) program, the Delta IV family of launch vehicles meets all customer requirements for the launch of high-priority U.S.A.F., National Reconnaissance Office (NRO), NASA, and commercial payloads to orbit. With operational launch pads on both coasts — Space Launch Complex-37 at Cape Canaveral Air Force Station, Florida, and Space Launch Complex-6 at Vandenberg Air Force Base, California — every Delta IV configuration is available to service the requirements of current and future satellite programs.

The Delta IV Workhorse
The Delta IV launch system is available in five configurations: the Delta IV Medium (Delta IV M), three variants of the Delta IV Medium-Plus (Delta IV M+), and the Delta IV Heavy (Delta IV H). Each configuration is comprised of a common booster core (CBC), a cryogenic upper stage and either a 4m-diameter or 5m-diameter payload fairing (PLF).

There are three variants of Delta IV M+ configuration. The Delta IV M+(4,2) uses two strap-on solid rocket motors (SRMs) to augment the first-stage CBC and a 4-m diameter PLF. The Delta IV M+(5,2) and Delta IV M+(5,4) have two and four SRMs, respectively, and 5m-diameter PLF. The latter was used for WGS-4.

The main engine for the Delta IV is the RS-68. Designed and manufactured by Pratt & Whitney Rocketdyne, the throttleable RS-68 engine is the largest existing hydrogen-burning engine. Conceived using a simplified design approach, the resulting engine requires 80 percent fewer parts than the Space Shuttle main engine, is lower risk, has reduced development and production costs and has inherently reliable operation.

Nominal Thrust (sea level): 663,000 lb
Specific Impulse (sea level): 359 seconds
Length: 204 in
Weight: 14,876 lb
Fuel/Oxidizer: Liquid Hydrogen/Liquid Oxygen

For missions requiring additional thrust at liftoff, the Delta IV M+ configurations use either two or four Alliant Techsystems-manufactured solid rocket motors (SRM). Separation is accomplished by initiating ordnance thrusters that provide a radial thrust to jettison the expended SRMs away from the first stage.

Peak Vacuum Thrust: 280,000 lbf
Total Vacuum Impulse: 17,957,000 lb-seconds
Length: 637 in
Maximum Diameter: 60 in
Weight: 74,500 lb
Burn Time: 90 seconds

Both the Atlas and the Delta IV second stages rely on the RL10 propulsion system to power their second stages. Logging an impressive record of more than 385 successful flights and nearly 700 firings in space, RL10 engines, manufactured by Pratt & Whitney Rocketdyne, harness the power of high-energy liquid hydrogen and boast a precision control system and restart capability to accurately place critical payloads into orbit. The Delta IV employs the RL10B-2 with the world’s largest carbon-carbon extendible nozzle.

Nominal Thrust: 24,750 lb
Specific Impulse: 465.5 seconds
Fuel/Oxidizer: Liquid Hydrogen/Liquid Oxygen
Length: 86.5 in (stowed); 163.5 in (deployed)
Diameter (nozzle extension): 84.5 in
Weight: 664 lb

Fairings protect the payload once the payload is encapsulated through the boost phase of flight. The 5m-diameter composite fairing is of bisector design and comes in two standard lengths. The 14.3 m (47 ft) fairing is used on the Delta IV M+(5,2) and M+(5,4). The 19.1 m (62.7 ft) fairing is used on the Delta IV Heavy.

The 5m metallic trisector fairing (the baseline for heritage government programs) is a modified version of the flight-proven Titan IV aluminum isogrid fairing designed and manufactured by Boeing. All PLFs are configured for off-pad payload encapsulation to enhance payload safety and security and to minimize on-pad time.

The advanced technology and capabilities of the 6.5 ton WGS-4 satellite, with solar-power wings spanning 134 feet, will prove to be an immensely crucial asset for MILSATCOM needs, with access at speeds up to 2.8 gigabits per second. For UAV/UAS ISR missions, the increased communications capacity — thanks to the bypass feature that enables two uplink and two downlinks for 3x normal channel bandwidth — brings a much wider pipeline into strategic play.

Mr. Jim Sponnick, the vice president of mission operations for United Launch Alliance, said, “WGS was the first constellation of satellites to launch on both Delta 4 and Atlas 5 vehicles since the formation of ULA. We’re honored to have worked closely with our Air Force partners in integrating and launching these important WGS satellites. Our ability to integrate and launch satellites successfully and efficiently on two launch systems to provide operational flexibility was a primary reason that ULA was formed.”

Mr. Mark Spiwak, the WGS program director for WGS at Boeing, stated, “WGS is the DOD’s highest capacity communications satellite system. These satellites provide tremendous operational flexibility to deliver the needed capacity, coverage and connectivity in support of demanding operational scenarios. Everyday WGS helps save and improve the lives of users worldwide. This launch (is) another important step in advancing these capabilities.”

Mr. Dave Madden, the director of the Military Satellite Communications System Directorate at the U.S.A.F.’s Space and Missile Center, noted, “WGS provides critical operation and situational awareness information to the warfighter. I want to thank Boeing and the work they have done to give us a first-class quality satellite that’s going to be a critical add to our constellation.”

Go Boeing! Go United Launch Alliance. Go WGS!

Editors’ Note:
We wish to thank Boeing and United Launch Alliance for their presentations regarding the WGS and WGS-4 satellites and the Delta IV launch vehicle, from which the contents of this article were assembled by the editors. All imagery is courtesy of Boeing and/or United Launch Alliance.