In what is proving to be a dramatic week for space flight, United Launch Alliance’s Atlas V rocket made its fiftieth flight on Wednesday, tasked with orbiting the GPS IIF-8 satellite for the US Air Force. Liftoff from SLC-41 at Cape Canaveral was on schedule at the start of an eighteen minute window that opened at 13:21 local time (17:21 UTC).
Atlas V Launch:
Introduced in 2002, the Atlas V was originally developed by Lockheed Martin for the US Air Force’s Evolved Expendable Launch Vehicle (EELV) programme, along with Boeing’s Delta IV.
Based loosely on the earlier Atlas-Centaur series of rockets, the Atlas V is a two-stage rocket with a Common Core Booster (CBC) first stage and a Centaur upper stage.
Early Atlas V launches were conducted by International Launch Services (ILS), however Lockheed withdrew in 2006 ahead of the formation of United Launch Alliance (ULA) that December.
A partnership between Lockheed Martin and Boeing, ULA is responsible for the manufacture and operation of both EELVs and the older Delta II, as well as marketing them to US Government customers.
ULA has also conducted commercial missions under contract to Lockheed Martin for the Atlas V, and Boeing for the Delta II. The Delta IV is not offered for commercial launches.
Both the Atlas V and Delta IV were designed to be adaptable to all of the US Air Force’s payload requirements, with multiple configurations depending on the required capacity.
For the Atlas V this meant a Light configuration with a modernised Agena upper stage, a series of medium to intermediate configurations with varying numbers of solid rocket boosters to increase performance, and a Heavy configuration with two additional Common Core Boosters to provide the maximum capacity. The Light and Heavy configurations were cancelled and never flew.
The first flight of the Atlas V took place successfully in August 2002, carrying Eutelsat’s Hot Bird 6 spacecraft (since renamed Eutelsat 8 West C).
All of the rocket’s early flights carried commercial communications satellites, with the next few launches orbiting HellasSat-2, Rainbow 1, AMC-16 and Inmarsat-4F1. In August 2005 the sixth Atlas V embarked on the type’s first mission for the US Government, deploying NASA’s Mars Reconnaissance Orbiter on the first leg of its mission to the Red Planet.
The next launch in January 2006 carried the New Horizons probe, which is currently en route to Pluto with a flyby expected next July.
In April 2006 the Atlas flew its last mission for International Launch Services, carrying SES Astra’s Astra-1KR spacecraft. Eleven months later ULA flew its first Atlas mission, carrying six small satellites for the Space Test Program.
The only blemish on the Atlas V’s launch record to date occurred during the rocket’s tenth flight, in June 2007. Carrying a pair of Intruder ocean surveillance satellites, designated NROL-30 or USA-194, for the National Reconnaissance Office, the Atlas injected its payload into a lower than planned orbit after the upper stage ended its final burn prematurely.
The fault was later traced to a liquid hydrogen leak caused by a faulty valve. Despite the shortfall both satellites were able to manoeuvre themselves into a usable orbit.
The Atlas returned to flight in October 2007 with the launch of the first Wideband Global Satcom spacecraft for the Air Force, finishing the year with the deployment of a Quasar communications satellite for the NRO in December.
In 2008 two Atlas V launches occurred, including the type’s first mission from Vandenberg Air Force Base in March – using a pad which had previously been used by the Atlas II. This launch carried a signals intelligence satellite for the National Reconnaissance Office, while the other launch, in April, deployed ICO Global Communications’ ICO-G1 satellite.
Despite the satellite being deployed successfully, concerns regarding the performance of the first stage on the ICO mission kept the Atlas grounded for the rest of 2008. A year later the rocket returned to flight, again deploying a Wideband Global Satcom communications satellite.
This was the first of five launches in 2009, including NASA’s Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS), which were deployed in June. As part of the LCROSS mission the Atlas’ upper stage was intentionally impacted into the south pole of the Moon.
The three other launches in 2014 carried the PAN communications satellite for an undisclosed government agency, a Defense Meteorological Satellite Program (DMSP) weather satellite and the Intelsat 14 communications spacecraft.
Four Atlas launches in 2010 carried NASA’s Solar Dynamics Observatory, the first flight of the recoverable X-37B spacecraft, an Advanced Extremely High Frequency military communications satellite and a Topaz radar imaging spacecraft.
Five launches in 2011 included NASA’s Juno mission to Jupiter and the Curiosity rover bound for Mars as well as three military payloads – one of which was a further X-37B mission.
In 2012 six launches were made, including the third X-37B – which landed earlier this month after nearly two years in orbit – three military communications satellites, a pair of Intruder ocean surveillance satellites and NASA’s Van Allen Probes to study Earth’s radiation belts.
Last year the Atlas made eight flights; deploying NASA’s TDRS-11 data relay satellite, Landsat 8 Earth imaging spacecraft and the MAVEN probe to study Mars. The remaining launches carried military payloads; a SBIRS-GEO missile defence satellite, a GPS navigation spacecraft, MUOS and AEHF communications satellites and a Topaz radar reconnaissance bird for the NRO.
Wednesday’s launch is the eighth Atlas launch of 2014.
For Atlas, the year began with the launch of NASA’s TDRS-12 in January, before a launch from Vandenberg carried a DMSP weather satellite into orbit in early April.
Seven days after the DMSP launch another Atlas flew from Cape Canaveral carrying the NROL-67 payload – believed to be a successor to the Mercury signals intelligence satellites launched in the 1990s. In May an Atlas V carried an NRO Quasar satellite, NROL-33, into orbit.
Early August saw the launch of the previous GPS satellite – GPS IIF-7 – from the Cape, followed by a commercial launch from Vandenberg with the WorldView-3 Earth imaging satellite. The most recent Atlas launch occurred in mid-September with the CLIO satellite. Like 2009’s PAN, CLIO is a communications satellite launched for an undisclosed government agency.
The Atlas that launched on Wednesday had the tail number AV-050.
Wednesday’s payload, GPS IIF-8, is the eighth Block IIF satellite in the Global Positioning System (GPS) constellation. Used to provide navigation data to both military and civilian users, the GPS programme began in the 1970s with the first demonstration satellite launching in February 1978.
The first-generation GPS constellation consisted of ten test satellites – an eleventh was launched by failed to achieve orbit – operating in more highly inclined orbits than those which would later be used for operational missions.
Begun as a military programme, US President Ronald Reagan ordered that the system be made available to civilian users once complete after the Soviet Union shot down a Korean Air Lines Boeing 747 which strayed into its airspace in 1983.
The first operational, or Block II, GPS satellite was launched on the maiden flight of the Delta II rocket in 1989, with all operational spacecraft until 2009 riding to orbit atop Delta IIs. In late 1990 the Block II spacecraft were replaced with the upgraded Block IIA, which itself gave way to the Block IIR (Replenishment) series in 1997.
The current-generation GPS satellites, the Block IIF, are an interim series designed to bridge the gap between the IIR and the new Block III spacecraft which will replace them.
Constructed by Boeing the new satellites are lighter than the previous generation, achieved in part by eliminating the solid apogee motor used to inject the satellites into their final orbit.
The Atlas V and Delta IV, being far more powerful than the Delta II, are able to place the spacecraft directly into their operational medium Earth orbits.
The first Block IIF satellite was deployed by a Delta IV in May 2010. Of the seven launched to date, two have flown aboard Atlas Vs and the remaining five atop Delta IVs.
Wednesday’s launch took place from Space Launch Complex 41 at the Cape Canaveral Air Force Station, a former Titan launch pad which was converted for the Atlas V in the late 1990s. The complex was originally built in the 1960s for the Titan IIIC, with the Titan IIIE and Titan IV rockets later launching from it.
During the 1970s Complex 41 was the launch site for both of NASA’s Viking missions to Mars and both Voyager missions to the Outer Planets, which made use of the Titan IIIE with its Centaur upper stage.
The final Titan IV launch from Complex 41 occurred in 1999, and was an unsuccessful attempt to place a Defense Support Program missile detection satellite into geostationary orbit. Demolition work on pad structures began later the same year to set the facility up for the Atlas V’s “clean pad” approach.
Atlas rockets are assembled off-pad in the Vertical Integration Facility, before being rolled to the launch complex atop a mobile launch platform. By contrast the Atlas pad at Vandenberg, SLC-3E, uses a traditional assembly-on-pad approach.
The launch on Wednesday began with ignition of the Atlas’ RD-180 main engine 2.7 seconds before the countdown reached zero. Liftoff occurred at the +1.1 second mark as the thrust the vehicle is producing exceeds its weight.
For GPS launches the Atlas V flies in the 401 configuration, with a four-metre payload fairing, a single engine Centaur upper stage and no solid rocket motors attached to the first stage. As a result all thrust during the early stages of flight comes from the RD-180 burning RP-1 propellant in liquid oxygen.
The RD-180, which is derived from the RD-170 developed for the Soviet Union’s Zenit and Energia rockets, is a two-chamber engine which was first introduced on the Atlas III, a short-lived rocket which served as a testbed for the Atlas V development programme.
Around 17.2 seconds into flight AV-050 will began a series of pitch and yaw manoeuvres to establish the trajectory it required to reach its target orbit.
The rocket flew downrange on an azimuth of 45.8 degrees, reaching a speed of Mach 1 at around the one minute, 18.5 second mark.
The vehicle passed through Max-Q, the area of maximum dynamic pressure, 90.3 seconds after liftoff.
First stage flight lasted four minutes and 3.8 seconds, with separation of the spent Common Core Booster occurring six seconds after its engine cut off.
Following staging the second stage, the Centaur, entered its prestart phase with ignition of its RL10A-4-2 engine taking place ten seconds later. The payload fairing separated from the nose of the rocket eight seconds into second stage flight.
The Centaur burned for twelve minutes, 49.6 seconds, entering an elliptical transfer orbit. Three hours, one minute and 7.3 seconds later, after coasting to its apogee, the Centaur restarted for a brief second burn. Lasting 89.7 seconds, this burn circularised the spacecraft’s orbit ready for deployment.
The satellite separated four minutes and 45.7 seconds after the burn ended, or three hours, 24 minutes and 17.5 seconds after lifting off. The target orbit for spacecraft separation is a circular semi-synchronous orbit at an altitude of 20,448 kilometres (12,705 miles, 11,041 nautical miles) and an inclination of 55.0 degrees.
Once operational GPS IIF-8 will broadcast pseudo-random noise (PRN) code 03. The satellite will operate in slot 1 of plane E of the GPS constellation, replacing the GPS IIR-4 satellite which was launched in May 2000. IIR-4, which is also known as USA-150, will then be re-phased into a reserve slot in the A plane of the constellation to replace GPS IIA-19, the final Block IIA satellite to launch, which is being decommissioned.
The seventieth orbital launch attempt of 2014, Wednesday’s mission comes less than twenty four hours after the failure of the United States’ previous launch.
An Orbital Sciences Antares rocket flying from the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia, appeared to suffer a failure seconds after launch, crashing in flames close to the launch pad. The Antares had been carrying a Cygnus spacecraft intended for a resupply mission to the International Space Station.
The GPS launch is the twenty-first US launch of the year, with the Antares the only failure. AV-050 is the eighth Atlas V to fly in 2014, and the twelfth mission for United Launch Alliance, who have also launched three Delta IVs and a Delta II.
ULA’s next mission is scheduled to be the 4 December launch of a Delta IV Heavy with NASA’s Exploration Flight Test 1 (EFT-1), which will be the first test flight for the Orion spacecraft. The next Atlas V will launch a week later from Vandenberg with the NROL-35 payload for the National Reconnaissance Office.
Two GPS launches are scheduled to occur next year, with the next launch being of a Delta IV with GPS IIF-9 in March. GPS IIF-10 will ride an Atlas into orbit in June.