As the dust settled at Wallops Island, Va., following yesterday’s catastrophic loss of Orbital Sciences’ fifth Antares booster—carrying the ORB-3 Cygnus cargo ship, bound for the International Space Station (ISS)—the effort to continue delivering U.S. launch vehicles into space continued unabated today (Wednesday, 29 October), with the successful 50th flight of an Atlas V. Liftoff of the venerable Atlas, which is operated by United Launch Alliance (ULA), took place precisely on time at 1:21 p.m. EDT from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla., approximately 870 miles (1,400 km) to the south of Wallops. The mission lasted 3.5 hours and perfectly inserted the eighth satellite of the Block IIF Global Positioning System (GPS) constellation into a medium Earth orbit, at an altitude of 11,047 nautical miles (20,460 km), where it will provide critical positioning, velocity, and timing assets for worldwide users.
Despite the fact that ULA—the Centennial, Colo.-based launch services organization, formed in December 2006 as part of a merger between Boeing and Lockheed Martin—is not directly associated with NASA, there existed some concern that the first stage of its Atlas V is powered by a Russian-built RD-180 engine, which utilizes a mixture of liquid oxygen and a refined form of rocket-grade kerosene, known as “RP-1.” Antares, which appeared to lose thrust a few seconds after clearing the tower in yesterday’s ill-fated ascent, carries a first stage which is fed by two AJ-26 engines, developed by Aerojet from Soviet-era NK-33 powerplants. In its heyday, the NK-33 was part of Russia’s N-1 lunar superbooster, intended to challenge Apollo and send cosmonauts to the Moon. It exploded catastrophically during every one of its four launches between February 1969 and November 1972.
Thirty-six AJ-26 engines were purchased from Russia for $1.1 million per unit in the mid-1990s and have been extensively upgraded by Aerojet with modern electronics and instrumentation. They successfully powered four Antares boosters—and three Cygnus cargo ships—into orbit between April 2013 and July 2014, prior to Tuesday night’s failure. One engine, earmarked for use in one of next year’s planned Antares launches, also suffered a failure on the test stand in May 2014 at NASA’s Stennis Space Center in Hancock County, Miss. However, the common thread between the RD-180 and the AJ-26 in reality extends solely to the fact that both engines are Russian-made and liquid-fueled in nature. As a result, the ORB-3 launch failure had no bearing and created no impact on the final preparations for the Atlas V mission.
The vehicle at the center of this first U.S. spaceflight in the immediate aftermath of the first major U.S. launch failure of 2014 is actually one of the most reliable boosters in active operational service. The Atlas V first flew in August 2002 and, including today’s launch of GPS IIF-8, has now completed 50 missions, of which all but one have been classified as wholly successful. Only the June 2007 launch of two National Reconnaissance Office (NRO) satellites went awry, when a leaky oxygen valve caused the Centaur upper stage to shut down a few seconds early, leaving the payload in a slightly low orbit. Nevertheless, the mission was categorized as partially successful.
Over the past 12 years, the Atlas V’s various configurations have run the gamut from the “barebones” 401 to the 541 heavylifter and have delivered 56 primary payloads into orbit. These have included commercial communications satellites and a range of military spacecraft, including members of the Wideband Global Satcom (WGS), the Defense Meteorological Satellite Program (DMSP), the Advanced Extremely High Frequency (AEHF), geostationary-orbiting elements of the Space-Based Infrared System (SBIRS), and a pair of heavyweight Multi-User Objective System (MUOS) communications satellites. Additionally, the Atlas has delivered a number of classified payloads on behalf of the National Reconnaissance Office (NRO) and has launched the Orbital Test Vehicle (OTV)-3 mini-shuttle (also known as the “X-37B”) on three occasions in April 2010, March 2011, and December 2012. The most recent OTV-3 mission ended earlier this month, with a successful landing at Vandenberg Air Force Base, after 675 days aloft.
Although the Atlas V’s pedigree has been dominated by military payloads, it has also delivered a number of important missions of exploration into the heavens. These include the Mars Reconnaissance Orbiter (MRO) in August 2005, the Pluto-bound New Horizons in January 2006, the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) in June 2009, the Solar Dynamics Observatory (SDO) in February 2010, the Jupiter-headed Juno orbiter in August 2011, the Mars Science Laboratory (MSL) and Curiosity rover in November 2011, the Van Allen Probes in August 2012, and, most recently, the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft in November 2013.
Wednesday’s GPS IIF-8 mission was conducted by the workhorse Atlas V 401, which is numerically designated to describe a 4-meter (13-foot) payload fairing, no strap-on boosters, and a single-engine Centaur upper stage. This configuration of the vehicle is by far its most-flown variant, having supported 26 missions since August 2002, and has the capacity to deliver 21,600 pounds (9,800 kg) into low-Earth orbit and up to 10,470 pounds (4,750 kg) into geostationary transfer orbit.
Following the standard Launch Readiness Review (LRR) on Sunday, 27 October, the 196-foot-tall (60-meter) Atlas V booster was rolled out, atop its Mobile Launch Platform (MLP), from the Vertical Integration Facility (VIF) to the SLC-41 pad surface on Monday, completing the journey in about 35 minutes. Upon arrival at the pad, it was carefully centered and propellant umbilicals and electrical and data links were connected. The track mobiles were removed and ULA engineers prepared for formal countdown operations, which kicked off early Wednesday morning. Patrick Air Force Base meteorologists had already identified a 70-percent likelihood of acceptable weather conditions at T-0, with key concerns revolving around northerly winds.
A final “Go-No Go” poll of all stations produced a unanimous “Go” to enter the terminal countdown phase at 1:15 p.m., and controllers released the clock from its hold point at T-4 minutes at 1:17 p.m. All propellant tanks were pressurized and the Flight Termination System (FTS)—tasked with destroying the vehicle in the event of a major accident during ascent—was placed onto internal power and armed. At T-60 seconds came the final, almost symbolic call: “Go Atlas, Go Centaur, Go GPS,” declaring that the booster, upper stage, and payload teams were ready to support the launch.
The Atlas V 401’s RD-180 engine, with a propulsive yield of 860,000 pounds (390,000 kg), ignited about 2.7 seconds ahead of liftoff, burning a mixture of liquid oxygen and RP-1. Liftoff occurred at 1:21 p.m., precisely on the opening of the 18-minute “launch window.” Climb-out from SLC-41 commenced at T+1.1 seconds and the pencil-like vehicle rose vertically for about 16 seconds, after which the avionics of the Centaur upper stage commanded a pitch, roll, and yaw program maneuver. This established the Atlas onto the proper flight azimuth of 45.8 degrees, following a north-easterly trajectory to inject the 3,600-pound (1,630-kg) GPS IIF-8 satellite into orbit.
At the shutdown of the RD-180—whose Russian heritage has made ULA the subject of much criticism in 2014, particularly in light of sanctions issued after the Kremlin’s annexation of Crimea in March—about four minutes into the flight, the Atlas V had already reached an altitude of 34 miles (55 km) and was 55 miles (88 km) downrange of the Cape, traveling in excess of 5,000 mph (8,000 km/h). The 41-foot-long (12.4-meter) Centaur and attached GPS IIF-8 were detached, prior to two “burns” to achieve the target orbit of 11,047 nautical miles (20,460 km), inclined 55 degrees to the equator. Ignition of the Centaur’s 22,300-pound-thrust (10,100-kg) RL-10A engine for the first time occurred about 10 seconds after the separation of the Atlas V’s first stage. This engine employs a cryogenic mix of liquid oxygen and hydrogen and is designed to be restartable.
The first firing was followed by the jettisoning of the two-piece (or “bisector”) payload fairing to expose GPS IIF-8 to the space environment for the first time. The initial burn lasted about 13 minutes, after which the Centaur/payload combo coasted for almost three hours, ahead of a second burn, lasting just 90 seconds. After this event, the Centaur spun-up GPS IIF-8 to five revolutions per minute and released it into space at T+3 hours, 24 minutes, and 17.5 seconds. Throughout the ascent phase, telemetry data was gathered by the Eastern Range, together with various worldwide installations under the U.S. Air Force Space Command Network, including New Boston Air Force Station, N.H., the Royal Air Force’s Oakhanger installation in Hampshire, England, Diego Garcia in the Indian Ocean, and Guam in the western Pacific Ocean. Additionally, NASA’s Tracking and Data Relay Satellite System (TDRSS) will participate in the gathering of telemetry.
“ULA is honored to work with this world-class U.S. Government and contractor mission team and we are very proud to have delivered the GPS IIF-8 satellite to orbit today on the 50th Atlas V mission,” said Jim Sponnick, ULA’s vice president for Atlas and Delta Programs. “Achieving 50 Atlas missions with 100-percent mission success is a tribute to this team’s sustained focus on one mission at a time and dedication to reliably meeting our customer’s launch needs.”
GPS IIF-8, which arrived at Cape Canaveral Air Force Station for final processing on 16 July, is the fourth of its kind to be launched in 2014 and will represent the 12th overall GPS to be lofted atop a ULA booster and only the third to ride atop an Atlas V. It is anticipated that the GPS Block IIF network will employ a mixture of Atlas V and Delta IV launches, with the latter having been employed to insert GPS IIF-1, GPS IIF-2, GPS IIF-3, GPS IIF-5, and GPS IIF-6 into orbit. The forthcoming GPS IIF-9 and GPS IIF-10 satellites—currently scheduled to fly in 2015—will both be carried aboard Delta IVs. These “Interim” Block IIF satellites will keep the Navstar system of positioning, velocity, and timing assets fully operational until the next-generation GPS Block IIIA comes online in 2016.
Wednesday’s launch marked the fourth GPS mission of 2014. From its semi-synchronous, medium-altitude Earth orbit, GPS IIF-8 will circle Earth once every 12 hours. It represents the eighth satellite in a 12-strong network of GPS Block IIF spacecraft, the first of which was launched in May 2010. A second satellite followed in July 2011, then a third in October 2012, a fourth in May 2013, a fifth in February 2014, a sixth in May 2014, and a seventh in August 2014. The GPS IIF boasts improved positioning, velocity, and timing accuracy, a reprogrammable processor, an interference-free civilian signal for commercial aviation search and rescue, and a new Military code (or “M-code”) to offer better resistance to electronic jamming. “As each IIF satellite becomes operational, we continue the seamless transformation of the GPS constellation into an even more accurate, reliable, and durable navigation resource for the U.S. military and the global civilian user community,” said Craig Cooning, vice president and general manager of Boeing Space & Intelligence Systems. “Our efficient pulse-line manufacturing process, adapted from Boeing’s commercial airplane production lines, also ensures that we deliver each spacecraft on time and on cost.”
In the meantime, the Air Force expects the next-generation GPS IIIA network to enter service no earlier than April 2016, about two years later than originally intended. It awarded a $1.4 billion contract to Lockheed Martin in May 2008 to develop this new network, which may eventually comprise as many as 32 satellites, although the Air Force has only formally contracted for four of these. With 500 times the transmitter power of current systems, the IIIA satellites will benefit from improved navigational warfare capabilities, enabling them to shut off GPS services to limited geographical locations, whilst maintaining service to U.S. and allied forces. The GPS satellite system is operated and controlled by the 50th Space Wing, located at Schriever Air Force Base, Colo.
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