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Old 04-14-2018, 02:26 PM
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Arrow ULA Atlas V set for AFSPC-11 launch

ULA Atlas V set for AFSPC-11 launch
By: William Graham April 14, 2018
RE: https://www.nasaspaceflight.com/2018...spc-11-launch/

United Launch Alliance’s Atlas V rocket will carry out the AFSPC-11 mission for the United States Air Force Saturday, deploying the CBAS communications satellite and EAGLE technology demonstrator. Liftoff is scheduled for a launch window of undisclosed duration opening at 19:13 Eastern Time (23:13 UTC).

Saturday’s launch will see Atlas undertake a lengthy mission to inject its payloads directly into near-geostationary orbit, 35,786 kilometers (22,236 miles, 19,323 nautical miles) above the equator. The Air Force Space Command 11 (AFPSC-11) payload consists of two satellites which will separate from their carrier rocket over five-and-a-half hours after liftoff.

The primary payload for the AFSPC-11 mission is the Continuous Broadcast Augmenting SATCOM (CBAS) satellite. Few details of the CBAS mission have been made public. However, the spacecraft is known to be coordinated by the US Air Force’s Military Satellite Communications Directorate, who also manage the operational Wideband Global Satcom (WGS) and Advanced Extremely High Frequency (AEHF) communications programmes.

CBAS will serve as a communications relay for senior military commanders and augment the United States’ existing military satellite communications architecture.

Communications being vital in the modern battlefield, the US military operates a large and varied fleet of communications satellites. These include the Wideband Global Satcom (WGS) constellation that forms the backbone of the network, while the US Air Force’s Advanced Extremely High Frequency (AEHF) provides specialized protected communications.

The US Navy operates the Mobile User Objective System (MUOS), providing high-speed narrowband communications for mobile users. The National Reconnaissance Office operates its own fleet of relay satellites, the Satellite Data System (SDS), which supports its fleet of reconnaissance satellites.

In addition to these programmes, a number of legacy Defense Satellite Communications System (DSCS), Milstar and UHF Follow-On (UFO) satellites remain in service. These constellations have largely been replaced by WGS, AEHF and MUOS respectively.

CBAS is flying in the upper position for Saturday’s dual-satellite launch. The Air Force Research Laboratory’s ESPA-Augmented Geostationary Laboratory Experiment (EAGLE) satellite is mounted below it.

EAGLE has been built around an EELV Secondary Payload Adaptor (ESPA), which incorporates the separation mechanism for CBAS. This allows the two satellites to be stacked directly atop each other without the need for an additional payload adaptor such as the SYLDA used on dual-satellite Ariane 5 launches.

EAGLE was developed by Orbital ATK and hosts an array of technology demonstration payloads. The satellite is based on Orbital’s ESPAStar platform, which adds propulsion, power-generation and flight systems to an ESPA payload adaptor, turning it into a free-flying satellite. The core ESPAStar spacecraft has a dry mass of 430 to 470 kilograms (950 to 1,040 pounds), with a hydrazine-based monopropellant propulsion system mounted inside the payload adaptor ring with up to 310 kilograms (680 lb) of fuel.

The platform is three-axis stabilized and provides power via a 96 amp-hour battery and a deployable solar array, which will generate 1.2 kilowatts of power at the beginning of the satellite’s operational life.

On the outside of the ESPAStar platform’s adaptor ring, six hardpoints are available to mount payloads. Each hardpoint can accommodate a 181-kilogram payload (400-pound), either fixed to the satellite or a deployable subsatellite. EAGLE is the first mission to test the ESPASat bus, which is optimized for geostationary missions but can also be used in other orbits.

EAGLE is a partnership between the AFRL and the Space Test Program (STP). It is carrying four fixed experiments and a deployable subsatellite. The fixed experiment packages are the AFRL-1201 Resilient Spacecraft Bus Development Experiment (ARMOR), Compact Environmental Anomaly Sensor III Risk Reduction (CEASE-III-RR), Hypertemporal Imaging Space Experiment (HTI-SpX) and the Inverse Synthetic Aperture LADAR (ISAL). These experiments are primarily geared towards developing space situational awareness and satellite inspection capabilities.

CEASE-III-RR will use a suite of instruments to identify conditions in the space environment that could affect the operation of a satellite. Consisting of high and low-energy proton/electron telescopes and an electrostatic analyzer, CEASE will measure the flux of charged particles in geostationary orbit, with this data being used to identify potential causes of anomalies in the spacecraft’s data or operation.

HTI-SpX will use a suite of visible-light, ultraviolet and medium and long-wave infrared imagers to collect data that will be used to demonstrate hypertemporal image processing techniques. This will see the satellite collect data over a long period of time, automatically identifying small changes that may warrant further attention. Developed by Raytheon, HTI-SpX will serve as a demonstrator for future long-term surveillance missions.

ISAL will demonstrate laser radar (LADAR) imaging of satellites in geostationary orbit. The payload consists of a synthetic aperture radar system, using the difference in velocity between EAGLE and its imaging target to increase its aperture size for imaging, resulting in higher-resolution images of the target.

The subsatellite, Mycroft, will be deployed from EAGLE at an unspecified future date. Mycroft is based around Orbital ATK’s ESPASat platform, designed specifically for deployment from the ESPA.

This has a design life of three years. Measuring 56.6 by 56.6 by 70.0 centimeters (22.3 by 22.3 by 27.4 inches) before payload installation the bus has a dry mass of 70 kilograms (150 lb). It can carry up to 22.7 kilograms (50.0 lb) of hydrazine propellant and a thirty-kilogram (66 lb) payload.

The platform provides three-axis control with six degrees of freedom via reaction wheels and attitude control thrusters. It incorporates a 24 amp-hour lithium ion battery with a solar panel generating up to 265 watts of power. An ESPASat was previously used for the AFRL’s ANGELS experiment, which launched aboard a Delta IV in 2014 and was decommissioned last November.

AFSPC-11 will be launched by United Launch Alliance’s workhorse Atlas V rocket, flying in its 551 configuration. The rocket has tail number AV-079 and will be making the seventy-seventh flight of an Atlas V. One of the most reliable rockets in service worldwide, Atlas V has never lost a mission – the only blemish on its record a partial failure back in 2007 that left a pair of NRO ocean surveillance satellites in an incorrect orbit.

Link to photo of the rocket: https://www.nasaspaceflight.com/wp-c...-14-163514.jpg

Developed by Lockheed Martin under the US Air Force’s Evolved Expendable Launch Vehicle (EELV) programme, Atlas V first flew in August 2002 when it deployed Eutelsat’s Hot Bird 6 satellite into geosynchronous transfer orbit. The rocket’s launches were originally contracted by International Launch Services – who had marketed the earlier Atlas II and III vehicles – however in 2006 operations were passed to the newly-formed United Launch Alliance (ULA).

ULA was created from the amalgamation of Boeing and Lockheed Martin’s space launch divisions and took over responsibility for manufacturing and launching Boeing’s Delta II and Delta IV vehicles, as well as Atlas V. ULA also took responsibility for marketing its rockets to US Government customers, while Boeing and Lockheed Martin retained the right to market their respective rockets for commercial launches. Earlier this year, United Launch Alliance announced that it had taken over marketing commercial Atlas launches – its Delta rockets are no longer available for commercial missions.

Atlas V is a two-stage rocket, consisting of a Common Core Booster (CCB) first stage and a Centaur upper stage. The rocket is able to fly in many different configurations – varying the size of its payload fairing, the number of engines on the Centaur stage and the number of solid rocket boosters clustered around the CCB – in order to accommodate different payloads. The 551 configuration that will be used for Saturday’s launch is the most powerful version to have been developed. A more powerful version of the rocket, Atlas V Heavy, would have used two additional CCBs strapped to either side of the central core, however this never left the drawing board.

Link to a top down view of the rocket: https://www.nasaspaceflight.com/wp-c...-14-163552.jpg

Saturday’s launch is the eighth time Atlas V has flown in the 551 configuration – which was first used in January 2006 to send NASA’s New Horizons spacecraft on its way to Pluto. The configuration was also used for 2011’s launch of the Juno mission to Jupiter and to deploy five MUOS communications satellites for the US Navy between 2012 and 2016. This version of Atlas V uses a five-meter (16-foot) diameter payload fairing, five solid rocket motors and a single-engine Centaur (SEC) upper stage. Three different lengths of five-meter fairing can be used on Atlas 5 missions – with the AFSPC mission using the shortest of the three. Built by Swiss firm RUAG, the fairing measures 20.7 meters (68 feet) in length and encapsulates Centaur as well as the payload.

The AFSPC-11 launch will take place from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station. Originally built for the Titan IIIC rocket in the late 1960s, SLC-41 went on to serve the Titan IIIE and Titan IV rockets, remaining in service for Titan until 1999. NASA’s Voyager missions to the outer planets, Viking missions to Mars and the Helios missions to study the Sun – the latter a joint venture with the German Aerospace Centre – launched from Complex 41 in the 1970s, while most of the other Titan launches from the complex carried military payloads.

With EELV rockets due to replace the Titan IV within the first few years of the 21st century, SLC-41 was transferred to the Atlas programme with Titan launches continuing from nearby Space Launch Complex 40 until 2005. Lockheed Martin wasted no time in converting the pad. In October 1999 – just six months after the last Titan IV had departed the complex – SLC-41’s fixed and mobile service towers were toppled in controlled explosions.

Atlas V initially used a clean-pad approach at the complex, with its umbilical tower attached to a mobile launch platform and all integration performed at the Vertical Integration Facility (VIF), a purpose-built tower 600 meters (9,970 yards) south of the pad. In recent years a fixed tower has been constructed at the launch complex housing a crew access arm to support future manned launches with Boeing’s CST-100 Starliner spacecraft. Starliner is expected to make its first, unmanned, test flight later this year.

SLC-41 was the site of Atlas V’s maiden flight in 2002 and was originally expected to be the rocket’s only launch pad. The former Atlas II launch pad at Vandenberg Air Force Base’s Space Launch Complex 3E (SLC-3E) was later converted to allow Atlas V to make higher-inclination launches. However, SLC-41 has been used for the majority of the rocket’s flights. Prior to the AFSPC-11 launch, SLC-41 had supported 27 Titan and 62 Atlas V missions, making Saturday’s launch the ninetieth mission to depart from Complex 41.

Saturday’s mission will begin with ignition of the Atlas Common Core Booster’s RD-180 engine, 2.7 seconds before the countdown reaches zero. Built by Russia’s NPO Energomash, the RD-180 is derived from the RD-170 family of engines originally developed for the Soviet Union’s Zenit and Energia rockets. A single engine with two combustion chambers and two nozzles, the RD-180 burns RP-1 propellant – rocket-grade kerosene – oxidized by liquid oxygen. Five Aerojet Rocketdyne AJ-60A solid rocket motors will augment the CCB at liftoff, igniting about T+1.1 seconds as the rocket lifts off.

Climbing away from Cape Canaveral, AV-079 will begin a series of pitch and yaw maneuvers 3.9 seconds into its mission, placing the rocket onto an 89.9-degree azimuth – almost due East – for the journey into orbit. Atlas will reach Mach 1, the speed of sound, 34.4 seconds after liftoff, passing through the area of maximum dynamic pressure – Max-Q – eleven-and-a-half seconds later.

Link to the actual launch: https://youtu.be/mFbD3bOyNso

The AJ-60A boosters will burn for a little over ninety seconds before their thrust tails off and the boosters burn out. Two of the boosters will be jettisoned 107 seconds into the flight, with the remaining three separating a second and a half later.

The RD-180 engine will continue to burn as Atlas climbs out of the atmosphere. About three minutes and 31 seconds after liftoff the payload fairing will separate from the rocket. This structure, which encloses the upper stage and payload to protect them from the atmosphere and preserve the rocket’s aerodynamic qualities, is no longer needed once the vehicle reaches space and is jettisoned to reduce weight.

Shortly after the fairing separates the forward load reactor, a device attached at the top of the Centaur to stiffen the fairing and reduce vibrations, will also be jettisoned.

Atlas’ Common Core Booster will burn out four minutes and 33.5 seconds after liftoff – a milestone in the launch that is designated booster engine cutoff (BECO). The spent core is discarded, separating four seconds after BECO, with Centaur igniting its RL10C-1 engine ten seconds later.

The cryogenically-fuelled Centaur burns liquid hydrogen and liquid oxygen. The stage traces its heritage back to the 1960s and the earliest Atlas-Centaur rockets, while Centaur has also flown aboard Titan rockets, was proposed for several other launch systems including the Saturn I and the Space Shuttle, and will be used – at least at first – as the second stage of United Launch Alliance’s next-generation Vulcan rocket.

Centaur will make at least three burns during Saturday’s launch as it carries AFSPC-11 into geostationary orbit. The first burn will last six minutes and 1.2 seconds, injecting itself into an initial parking orbit. After a twelve-minute, 6.7-second coast Centaur will restart as it passes over the west coast of Africa, making a five-minute, 48.9-second burn to place itself into a geosynchronous transfer orbit. Five hours and six minutes after the end of the second burn, after reaching geostationary altitude, Centaur will make a two-minute, 36.2-second burn to circularise its orbit and reduce its orbital inclination to zero.

United Launch Alliance has not confirmed the separation times for either CBAS or EAGLE, nor whether Centaur will undertake any further maneuvers between separation of its two payloads. After both satellites have separated, Centaur will place itself into a disposal orbit to reduce the chances of it colliding with a satellite in geostationary orbit. The mission is due to end at six hours, 57 minutes and 24.4 seconds elapsed time – one hour, twenty minutes and two seconds after the end of Centaur’s third burn.

Saturday’s launch is the third Atlas V mission of 2018, following successful launches in January and March that respectively carried the SBIRS-GEO-4 satellite for the US Air Force and GOES 17 for the National Oceanic and Atmospheric Administration (NOAA).

The next Atlas V launch is currently targeting 4 May out of California’s Vandenberg Air Force Base, with a mission to deploy NASA’s InSight lander bound for Mars. Atlas’ next East Cost launch is not currently expected until the end of August, when the rocket will carry Boeing’s Starliner spacecraft on its first unmanned test flight. The August launch will be the first flight of Atlas V with a dual-engine Centaur and the first not to use a payload fairing.
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