Photo from ULA prior to launch of AFSPC-11. Standing tall among four lightning towers - Wow
Mission Rundown: ULA - Atlas V 551 - AFSPC-11
Written: December 2, 2022
It’s an Air Force radio thingy
United Launch Alliance’s Atlas V 551 rocket launched the AFSPC-11 mission for the United States Air Force on Saturday, April 14, 2018 deploying the CBAS communications satellite and EAGLE technology demonstrator. Liftoff occurred without problems the first time asking for a 19:13 EDT - Eastern Daylight savings Time - 23:13 UTC liftoff.
Saturday’s launch from SLC-41 involved Atlas undertaking 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 AFSPC-11 Payloads
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.
CBAS was flying in the upper position for Saturday’s dual-satellite launch. The Air Force Research Laboratory’s ESPA-Augmented Geostationary Laboratory Experiment (EAGLE) satellite was mounted below it.
EAGLE has been built on 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.
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 ring with six payload ports on its side, turning it into a free-flying satellite.
Graphic by Orbital ATK of EAGLE in orbit. Six ports. BUS in the middle. CBAS release ring on edge
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 ‘Bus’ 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.
A 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.
Mycroft 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 secret military 30 kilograms (66 lb) hosted payload.
The ESPASat 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.
The AtLas V 551 Launch
AFSPC-11 was launched by United Launch Alliance’s workhorse Atlas V rocket, flying in its 551 configuration. The rocket had tail number AV-079 and 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 was a partial failure back in 2007 that left a pair of NRO ocean surveillance satellites in an incorrect orbit.
Graphic of Atlas V 551 in its major parts. Five SRB’s, main booster, Centaur 2nd stage and CBAS
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 – depending on different payloads.
The 551 configuration 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 CCB’s strapped to either side of the central core, however this never left the drawing board.
Atlas V used 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 took place from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station.
Landing zones for Atlas V 551 spent parts: Five SRB’s, two fairing halves and a main core booster
Saturday’s mission began with ignition of the Atlas Common Core Booster’s RD-180 engine, 2.7 seconds before the countdown reached 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 began 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 reached 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.
The AJ-60A boosters burned for a little over ninety seconds before their thrust tails off and the boosters burned out. Two of the boosters jettisoned 107 seconds into the flight, with the remaining three separating a second and a half later.
The RD-180 engine continued to burn as Atlas climb’s out of the atmosphere. About three minutes and 31 seconds after liftoff the payload fairing separated 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, was also jettisoned.
Atlas’ Common Core Booster burned 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.
Centaur made at least three burns during Saturday’s launch as it carried AFSPC-11 into geostationary orbit. The first burn lasted six minutes and 1.2 seconds, injecting itself into an initial parking orbit. After a twelve-minute, 6.7-second coast Centaur restarted 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 made a two-minute, 36.2-second burn to circularize 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.
However, they confirmed After successful separation events, which would have been followed by Centaur placing itself into a disposal orbit to reduce the chances of it colliding with a satellite in geostationary orbit. The mission ended 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 was 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).
