United Launch Alliance delivered to orbit eighth Wideband Global SATCOM satellite yesterday. Spacecraft will provide reliable and resistant for jamming communication for United States Armed Forces.
ULA with their Delta IV Medium+ (5,4) showed during 114th mission in company’s history, that confidence of Department of Defense, which was put into their fleet of launch vehicles was not wasted. Again launch was performed flawlessly and without any problems during following 42 minutes of the mission. Worth $426 million satellite was securely delivered to designated orbit under 5 m wide payload fairing – for the sixth time by Delta IV launch vehicle. WGS-8 represents latest Block II generation of Wideband Global SATCOM spacecrafts and will serve to U.S. Army and U.S. Air Force, albeit already one and one planned satellite (WGS-6, WGS-9) operating under WGS system, were founded by partner countries: Canada, Australia, New Zealand, Netherlands, Luxembourg and Denmark.
Maybe not perfect, but still favorable weather forecasts given by 45th Weather Squadron put standing at SLC-37 Delta IV rocket into last phase of launch campaign. Due the fact, that launch was scheduled for the beginning of 49 minutes launch window starting at 23:53 UTC, rocket was under last preparations for whole Wednesday. Even with 80% of weather forecast (caused mainly by heavy clouds on higher altitude), launch was still set for “go”. Countdown entered into planned hold phase at 23:16 UTC; weather became more favorable reaching its best with 90% for go. At 23:27 UTC rocket switched to internal power and core stage with four GEM-60 solid fueled boosters were ready for launch. Seven minutes before launch, last readiness polls of the launch team and mission managers have been completed and mission received final green light from ULA launch director and the Air Force mission director. Four minutes before opening of launch window, countdown was resumed. Ninety seconds before launch tanks with LH2 and LOX were pressurized and after next 50 seconds, tanks were already secured to flight. After final “go” 30 seconds before launch, rocket performed spectacular liftoff at 23:52 UTC. Next it performed standard pitch and roll maneuver to set trajectory for South-East. After 36 seconds rocket hit and passed sound barrier still being supported with four GEM-60. Eleven seconds later at T+47″ rocket reached point of maximal dynamic pressure. At T+1’35” all four boosters were cut off and separated ten seconds later. After passing speed of 10 Ma at T+3’05”, nose cone was jettisoned and WGS-8 was exposed. At T+3’57” CBC cut off its RS-68A engine and eight seconds later it separated from Delta Cryogenic Second Stage. Next at T+4’23” RL10B-2 was ignited for the first time. Second Stage with WGS-8 reached altitude of 34500 km (with designated highly elliptical SSO transfer orbit with apogee of 38616 km) at T+16′. First cut off was performed at T+19’47”. Delta Cryogenic Second Stage started ballistic phase of flight to reignite engine at T+29’28” for three minutes. Burn was finished at T+32’38”. Four minutes later stage and WGS-8 reached designated orbit. Finally at T+46’49” satellite was deployed.
WGS-8 is one of the satellites developed to meet demands of new communication system for Department of Defense. Wideband Global SATCOM was designed to be high capacity, resistant for jamming and secure mean of communication between Army and Air Force; at the moment eight satellites are operating with planned at least two in nearest future. Until now, two generations of WGS spacecrafts were developed: Block I (first three satellites), Block II (further satellites). Due the character of the WGS program, DoD offered possibility of joining to program and integration own military communication systems with U.S. Army to foreign partners. In this way WGS-6 was founded by Australian Government and WGS-9 is planned to be founded thanks to agreement signed in 2012 by Canada, Denmark, Luxembourg, the Netherlands and New Zealand. These countries decided to add $620 million to WGS budget to get access to WGS system. It is still lower cost than creating own modern communication system independently.
WGS-8 satellite is based on BSS-702 satellite bus updated with ion propulsion. It was manufactured and designed by Boeing, just as rest of the WGS spacecrafts. Four XIPS-25 ion thrusters for keeping correct orbit are able to provide 165 mN consuming 4215 W; R-4D-15 AKM if generating 440 N of thrust and is fueled with NTO/MMH. Satellite weighs 5987 kg fueled and ready to mission. It is powered by two deployable solar arrays with 40 m span and onboard batteries (11 kW of power will be provided in the end of mission). Its operational life is described as 14 years for GEO orbit mission – long service life was possible thanks to electric propulsion, which consumes less propellant for keeping satellite on correct orbit. Main equipment of WGS are of course antennas and transponders. To provide 19 coverage areas with 10 Ka and 8 X band spotbeams, satellite has three group of antennas. First with two dishes installed in the center on fuselage and additional two groups with five dishes each are placed on the both sides. Antennas are able to move (only antennas for global coverage are fixed) with electrical system (X band antennas) or mechanical (Ka band antennas) system. WGS operates on 4.875 GHz bandwidth with capacity ranging from 2.1 Gbps up to 3.6 Gbps. It is possible to operate on 1900 independently routable 2.6 MHz channels; WGS offers up to 19 coverage areas placed from 65° North and South latitude.
Delta 4 Medium+ (5,4); in this configuration rocket is equipped with cryogenic upper stage and five-meter nose cone. It is supported by 4 solid fueled strap-on boosters. GEM-60 boosters are provided by Orbital ATK – each is equipped with single engine fueled with 29700 kg of HTPB and able to provide thrust at 826.6 kN. First stage weight is 226400 kg, height is 36.6 m and diameter is 5.1 m. It is equipped with one RS-68A engine able to provide 3140 kN of thrust and is fueled with LH2/LOX propellant. Second cryogenic stage, called Delta Cryogenic Second Stage (DCSS), weighs 30700 kg; both are powered with liquid fueled RL-10-B-2 engine (fueled with LH2/LOX with propellant mass at 27000 kg or 28000 kg depending on mission), which is giving 110 kN of thrust. Version used today was equipped with 5 m x 13.7 m fairing with weight of the second stage at 30550 kg and diameter at 5.1 m.