(word processor parameters LM=8, RM=78, TM=2, BM=2) Taken from KeelyNet BBS (214) 324-3501 Sponsored by Vangard Sciences PO BOX 1031 Mesquite, TX 75150 August 3, 1990 Courtesy of NASA BBS at 205 895-0028 -------------------------------------------------------------------- FLTSATCOM LAUNCH KSC 81-89 September 1989 FLTSATCOM-8 VERSATILE UHF/EHF MILITARY SATELLITE COMMUNICATIONS SYSTEM SHARED BY THE U.S. NAVY, AIR FORCE, AND DEPARTMENT OF DEFENSE PROVIDES RELIABLE, SECURE COMMUNICATIONS FOR SHIPS AND SUBMARINES AT SEA, PLANES IN THE AIR, AND MILITARY GROUND UNITS THROUGHOUT THE WORLD PROVIDES INSTANT COMMUNICATIONS BETWEEN PRESIDENT AND COMMANDING OFFICERS IN THE UNITED STATES AND REMOTE UNITS ANYWHERE IN THE WORLD FLTSATCOM (pronounced FleetSatCom, for Fleet Satellite Communications) is a versatile, high-capacity worldwide military communications system operated by the United States. NASA previously launched seven of these spacecraft for the military services, all on Atlas/Centaur vehicles. With FLTSATCOM-8, the last to be launched under NASA auspices, there will be six FLTSATCOM satellites operating in orbit. FLTSATCOM provides instant communications between the President and commanding officers in the United States and remote units stationed anywhere in the world. FLTSATCOM-1, operating since February 1978, provides service from Southeast Asia across the Pacific to the West Coast of the United States. FLTSATCOM-2, launched in May 1979, covers the Indian Ocean area from Africa to the Phillipines. FLTSATCOM-3, launched in January 1980, provides service from the middle of the United States across the Atlantic and the Mediterranean. FLTSATCOM-4, launched in October 1980, is co-located with FLTSATCOM-1 and provides coverage over the Pacific. FLTSATCOM- 5, launched in August 1981, was damaged during launch, and was never declared operational. FLTSATCOM-7, launched in December 1986, was placed in orbit co- located with FLTSATCOM-1. It now provides service over the United States. The most recent, FLTSATCOM-6, was lost after being struck by lightning shortly after launch in March 1987. In addition to the Ultra High Frequency (UHF) capability of the earlier satellites in this series, FLTSATCOMs 7 and 8 carry an Extremely High Frequency (EHF) communications package. This package serves as a test bed for the new MILSTAR terminals. FLTSATCOMS are launched on Atlas/Centaurs from Launch Complex 36 on the Cape Canaveral Air Force Station in Florida. The Atlas stage will complete its burn and fall into the ocean. The first burn of the Centaur injects the spacecraft into a parking orbit, at a perigee altitude of about 92 statute miles (148 kilometers) and apogee of approximately 229 statute miles (369 kilometers). After a coast period of about 14 minutes, the Centaur engines ignite again and place the spacecraft into a highly elliptical, or egg-shaped, "transfer orbit" with an apogee of about 22,362 miles (35,988 kilometers). The Centaur releases the spacecraft and, as its final act, performs a retromaneuver which takes it safely out of the flight path. The U.S. Air Force Space Systems Division (SSD) then assumes charge of the satellite, operating through its Consolidated Space Test Center (CSTC) at Onizuka Air Force Base, Sunnyvale, CA. NASA tracking stations throughout the world, together with the Air Force Satellite Control Network Remote Tracking Stations, provide range and range-rate measurement support to assist the CSTC controllers in bringing the satellite on station. The elliptical transfer orbit is designed so that the satellite will reach its apogee while over the equator. To convert the orbit from an elliptical to a circular one, and change the angle of inclination so that the flight path will be more nearly above the equator, CSTC operators will correctly aim the spacecraft and fire an onboard solid propellant motor at a selected apogee. This final burn "transfers" the satellite into a circular "drift" orbit, almost at synchronous altitude and with the angle of inclination reduced to 5 degrees. The FLTSATCOM then drifts to its assigned place in the global network, where the CSTC controllers fire the small thrusters of the onboard hydrazine reaction control system to stop the drift motion. When a satellite is located above and in line with the equator at an altitude of about 22,238 miles (35,789 kilometers), and given a velocity of 6,879 miles (11,071 kilometers) per hour, its movement becomes "synchronized" with that of the Earth below. It appears to remain stationary in the sky, while actually completing one orbit every 24 hours. All fully geosynchronous satellites, including those for commercial communications, weather observation, and military communications, are stationed above the equator at the same altitude, spaced around a circle about 165,000 miles (266,000 kilometers) in circumference. They are carefully separated by distance or by assigned radio frequencies to prevent interference between their individual communications systems. Since FLTSATCOM-8, like its predecessors, will initially be inclined to the equator, it will appear from the ground to be moving back and forth from north to south. At the same time, it will appear to move slightly east and west from the centerpoint, and so trace a constant figure "8" across the equator in the sky. The Navy portion of the FLTSATCOM shared system provides communications between naval aircraft, ships, submarines, and ground stations. The Air Force portion of each satellite is part of the USAF Satellite Communications System (AFSATCOM). AFSATCOM links the National Command Authority with Strategic Air Command units, and other arms of the Air Force. A FLTSATCOM provides 23 UHF channels. FLTSATCOM-8, with an 81-pound (37-kilogram) adapter for connection to the vehicle, weighs about 5,061 pounds (2,296 kilograms) on the ground, and has a mass of about 2,696 pounds (1,223 kilograms) in space after burning up the apogee motor propellants. It measures 43.4 feet (13.2 meters) from tip to tip of the fully extended solar panels. The main body is 7.5 feet (2.3 meters) wide, and 21.6 feet (6.6 meters) high from the bottom of the body to the tip of the offset spiral antenna mast. Both the spiral antenna and the solar panels are in a retracted configuration for launch, as is the 16-foot-(4.9-meter) diameter, silver-filled stainless steel mesh UHF antenna. The main body consists of three attached hexagonal modules called the payload module, the spacecraft module, and the EHF module, or FEP. The solar arrays extend from the spacecraft module, which also contains the hydrazine-fueled reaction control system thrusters and tanks, Sun and Earth sensors, a reaction wheel which spins to hold the spacecraft steady in its operating attitude, and the other systems needed for control and operation of the spacecraft. The payload module contains the three antenna systems, the transponders for the 23 channels, and all the associated electronics required to support the communications functions. The offset mast is the UHF transmit antenna. A small, separate conical helix antenna atop the central mast serves as the S-band Tracking, Telemetry and Control antenna, used to command and monitor the spacecraft. The superhigh frequency antenna horn protrudes through a hole cut into the UHF antenna mesh. The FEP contains the Extremely High Frequency communications package, with its 30 (maximum) voice channels. The package was designed and built by the MIT Lincoln Laboratory in Lexington, Massachusetts. The EHF antenna, consisting of a 5 degree steerable spot beam and an Earth coverage aperture, look through cutouts in the center portion of the UHF transmitting antenna. In operation, the momentum wheel provides a means to control the spacecraft attitude so that the antennas are always aimed at the Earth. The two solar arrays rotate on their extended arms so that they constantly face the Sun. These two arrays contain three panels each, with a total of 23,000 solar cells, each 0.79 by 1.57 inches (2 by 4 centimeters) in size, which will produce about 2,200 watts at the beginning of their orbital life. Three 24-cell nickel-cadmium batteries provide power when the spacecraft must operate in the Earth's shadow; 2,150 of the solar cells are reserved for battery charging. FLTSATCOMs 1 through 4 and 7 have accumulated some 40 years of on-orbit service. Four of the five orbiting satellites already have lasted longer than their five-year design life. The current estimate of the expected life of the UHF communications capability is in excess of 10 years. The Extremely High Frequency package on FLTSATCOM-8 is expected to last more than two years. The spacecraft are built by TRW Space & Technology Group, Redondo Beach, CA. The U.S. Navy manages the overall program, and the U.S. Air Force Space Systems Division is the contracting agency for the space segment. The military agencies reimburse NASA for the cost of the Atlas/Centaur launch vehicle and associated launch services. ATLAS/CENTAUR 137.6 FEET (41.9 METERS) TALL; 10 FEET (3 METERS) IN DIAMETER WITH PAYLOAD, WEIGHS APPROXIMATELY 360,856 POUNDS (163,684 KILOGRAMS) AT LIFTOFF ATLAS THRUST 438,416 POUNDS (1,950,074 NEWTONS) AT LIFTOFF CENTAUR THRUST 33,000 POUNDS (146,784 NEWTONS) IN A VACUUM FOR 7 1/2 MINUTES Atlas/Centaur vehicles are built by General Dynamics/Space Systems Division (GDSS). FLTSATCOM-8 and its launch vehicle will be launched by a team from NASA, GDSS and the U.S. Air Force. This will be the last Atlas/Centaur launch by NASA. In the future, NASA will contract with either the U.S. Air Force or the vehicle manufacturer to procure Expendable Launch Vehicles (ELVs) such as the Atlas/Centaur, and related launch services. NASA will retain oversight responsibilities for those vehicles which carry NASA payloads. The two-stage, liquid-fueled Atlas/Centaur has been used to launch a variety of scientific and technological spacecraft. These have included Surveyors to the moon, Mariners to Venus, Mercury and Mars, and Pioneers to Jupiter and Saturn. It has placed Applications Technology Satellites, and COMSTAR, INTELSAT, and FLTSATCOM communications satellites into geosynchronous transfer orbits. In 1984, it was upgraded by lengthening the Atlas stage to provide larger propellant tanks. The Centaur stage has been improved by substituting attitude control thrusters powered by hydrazine (used as a monopropellant) for ones powered by hydrogen peroxide, and replacing the oxygen and hydrogen propellant pumps by pressure-fed systems. The 76.3-foot (23.3-meter) long first stage is an uprated version of the flight-proven Atlas vehicle used in the national space program since 1959. The Rockwell International/Rocketdyne MA-5 engine system burns RP-1, a highly refined kerosene, and liquid oxygen. The MA-5 uses two main engines, a 377,500-pound (1,679,120-newton) thrust booster engine with two thrust chambers, and a smaller sustainer with a single thrust chamber that produces approximately 60,000 pounds (266,900 newtons) of thrust. The sustainer nozzle is located between the two larger ones of the booster engine. Two small vernier engines which help control the vehicle in flight also are burning at liftoff, for a total thrust of 438,416 pounds (1,950,074 newtons). Total weight at liftoff is about 360,856 pounds (163,684 kilograms). An unusual feature of the Atlas vehicle is its "stage-and-a-half" construction. All five thrust chambers are burning at liftoff. After more than 2 1/2 minutes of flight, the booster engine cuts off. This engine and its supporting structures are jettisoned, deleting a large portion of the structural weight of this stage. The sustainer and vernier engines continue to burn until the propellants are gone, at about 4 1/2 minutes. This means an Atlas retains most of the weight reduction advantage gained by jettisoning a used-up stage, but does not have to ignite its engines in flight, as a separate stage must. The only radio frequency system on the Atlas is a range safety command system, consisting of two receivers, a power control unit, and a destruct unit. The Atlas can be destroyed in flight by ground control if necessary, but otherwise receives all its control directions from the Centaur stage. The Centaur stage sits above the Atlas on a barrel-shaped interstage adapter. The Atlas and Centaur separate two or three seconds after the Atlas burns out. Eight small retrorockets near the bottom of the Atlas fuel tank then back this stage away from the Centaur. The Centaur stage is 30 feet (9.1 meters) in length without the fairing on top. Exclusive of payload, it weighs about 39,000 pounds (17,700 kilograms) when loaded with propellants. The main propulsion system consists of two Pratt & Whitney engines burning liquid oxygen and liquid hydrogen, producing 33,000 pounds (146,784 newtons) thrust in the vacuum of space in which they are designed to operate. These engines can be stopped and restarted, allowing the Centaur to coast to the best point from which to achieve its final trajectory before igniting for another burn. While coasting, the stage is controlled by 12 small thruster engines, powered by hydrazine. These hold the stage steady and provide a small constant thrust to keep the propellants settled in the bottom of their tanks, a necessity for a second or third burn. A cylindrical nose fairing with a conical top sits on the Centaur and protects the spacecraft. Total vehicle height is 137.6 feet (41.9 meters). Both stages are 10 feet (3 meters) in diameter. The Centaur electronic packages are mounted in a circle around a conical equipment module, located above the upper tank. An adapter on top of this module connects to the payload adapter on the bottom of the spacecraft. These electronic packages provide an integrated flight control system which performs the navigation, guidance, autopilot, attitude control, sequence of events, and telemetry and data management functions for both the Atlas and Centaur stages. The heart of this system is a Digital Computer Unit (DCU), built by Teledyne. The DCU sends commands to control most planned actions, including all but items one, two, and five in the table, shown below. The DCU receives guidance information from a combination of sensors called the Inertial Measurement Group, built by Honeywell, and sends steering commands to all Atlas and Centaur engines. The Centaur also has a ground-controlled destruct system similar to that on the Atlas, in case the vehicle must be destroyed in flight. The Centaur uses the most powerful propellant combination available, has a lightweight structure, and an engine burn time of up to 7 1/2 minutes, the longest of any upper stage now in service. This gives it the most total energy for its size of any stage yet built. The following table provides a list of the major events that will occur during the flight. Event Time After Distance Liftoff Altitude Downrange Velocity MIN:SEC MI/KM MI/KM MPH/KPH Liftoff T+0 --/-- --/-- --/-- Atlas Booster Engine Cutoff 2:35 37/60 55/89 5,703/9,178 Jettison Atlas Booster Engine 2:38 39/63 60/97 5,764/9,276 Jettison Centaur Insulation Panels 3:0 51/82 93/150 6,124/9,856 Jettison Nose Fairing 3:43 71/114 169/272 7,055/11,354 Atlas Sustainer/ Vernier Engines Cutoff 4:30 89/143 266/428 8,466/13,625 Atlas/Centaur Separation 4:32 89/143 271/436 8,469/13,630 First Centaur Main Engines Start 4:43 97/156 295/475 8,441/13,584 Centaur Main Engines Cutoff 9:55 102/164 1,294/2,082 16,652/26,799 Second Centaur Main Engines Start 23:56 101/163 5,103/8,212 16,686/26,854 Second Centaur Main Engines Cutoff 25:32 110/177 5,600/9,012 22,013/35,426 Centaur/Spacecraft Separation 27:47 179/288 6,391/10,285 21,791/35,069 These numbers may vary, depending on exact launch date, launch time, and spacecraft weight. NOTE: The final velocity of 22,013 miles (35,426 kilometers) per hour places the spacecraft in a transfer orbit, with an apogee of 22,362 miles (35,988 kilometers) and a perigee of 104 miles (167 kilometers). The U.S. Air Force then assumes control of the spacecraft. At an apogee chosen by Air Force controllers, the onboard apogee motor will be fired to make the orbit more circular at geosynchronous altitude, about 22,238 miles (35,789 kilometers) above the equator. It will then be "drifted" to its assigned place in the FLTSATCOM global network. The spacecraft will have a final velocity of about 6,879 miles (11,071 kilometers) per hour. It will complete one orbit every 24 hours, and so move back and forth above the same area on both sides of the equator. -------------------------------------------------------------------- If you have comments or other information relating to such topics as this paper covers, please upload to KeelyNet or send to the Vangard Sciences address as listed on the first page. Thank you for your consideration, interest and support. Jerry W. Decker.........Ron Barker...........Chuck Henderson Vangard Sciences/KeelyNet -------------------------------------------------------------------- If we can be of service, you may contact Jerry at (214) 324-8741 or Ron at (214) 484-3189 --------------------------------------------------------------------