Screenshot from ULA Webcast of the launch of USSF-12. The weather is much better today
Mission Rundown: ULA - Atlas V 541 - USSF-12
Written: December 6, 2022
Giving another ‘Ring’ to Space
United Launch Alliance has deployed a pair of Space Force technology demonstration payloads into geostationary orbit Friday evening. The USSF-12 mission lifted off from Cape Canaveral at 7:15 PM EDT (23:15 UTC) on Friday, following a 24 hour delay from Thursday due to weather as well as additional weather delays early in the Friday window.
United States Space Force 12 (USSF-12) consists of two satellites that will help the Space Force to test and develop systems for future national security space missions. The Wide Field of View (WFOV) satellite will test an infrared sensor to be used on the next generation of missile detection satellites, while the USSF-12 Ring utilizes a free-flying propulsive EELV Secondary Payload Adapter (ESPA) to carry additional research payloads for the Space Test Program.
WFOV will be operated by Space Force’s Space Systems Command. Using space-based sensors allows the maximum possible warning of an incoming missile, giving time for defensive precautions and countermeasures to be employed against the threat and for a nuclear counterattack to be launched if necessary.
The WFOV - USSF-12 Payload
WFOV was constructed by Boeing’s Millennium Space Systems subsidiary, based on the Aquila M8 platform, and has a mass of around 3,000 kilograms. It carries a 200-kilogram infrared imaging system, the Wide Area Six-Degree Payload (WASP), built by L3Harris Technologies.
Unlike WFOV, few details about the smaller USSF-12 Ring have been made public, other than its use of the propulsive ESPA ring developed by Northrop Grumman.
The satellite will be operated by the Space Test Program, an agency under the US Department of Defense that carries out research and development of new space systems for future military applications.
Previous ESPA-derived spacecraft have deployed additional CubeSats after launch, although it is not clear whether this will be an element of the USSF-12 Ring’s mission. One CubeSat - USA-337 has been successfully deployed.
Photo of the payload top half being hoisted up in the VIF. Looks like they are loading a giant gun
The rocket launch
Atlas lifted off from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Space Force Station. Originally a Titan launch pad, SLC-41 has been the East coast home of Atlas V since its introduction and is due to continue in service with ULA for decades to come as the company transitions over to Vulcan.
AV-094 was stacked atop a mobile launch platform within the Vertical Integration Facility (VIF) and then rolled into position at the launch pad for liftoff.
The Common Core Booster is powered by a single RD-180 engine. This ignited at the T-1 second mark in the countdown, with liftoff occurring at T+1 second.
Four GEM-63 solid rocket boosters fired alongside the RD-180 for the first 98 seconds of flight, providing additional thrust as Atlas ascended through the dense lower regions of the Earth’s atmosphere.
After lifting off, AV-094 began a series of pitch and yaw maneuvers to put itself on course for geostationary orbit. The first of these took place 6.9 seconds into the flight, as the rocket assumed an easterly track to minimize its orbital inclination.
It took about 57.8 seconds for the rocket to reach Mach 1, the speed of sound. Less than ten seconds later, AV-094 passed through the area of maximum dynamic pressure, Max-Q.
Although the SRMs only burn for about 98 seconds, they remain attached for about ten seconds after burnout. At one minute and 48 seconds mission elapsed time, the spent boosters separated and fell away from the vehicle.
Three minutes and 26 seconds after liftoff, the payload fairing which encloses the satellites and the Centaur upper stage and provides protection during the climb through the atmosphere was jettisoned.
Shortly after fairing separation, the forward load reactor separated from the forward end of Centaur. Besides supporting the weight from the satellites and the fairing top half it stops hydrogen gasses from entering the payload housing. The satellites are in a nitrogen filled room to prevent water vapors from damaging corrosion and condensing.
The RD-180 continued to power the CCB until Booster Engine Cutoff (BECO) at the four-minute, 24-second mark in the mission. At BECO, the CCB shuts down its engine in preparation for stage separation, which occurs six seconds later. Centaur’s RL10C-1 engine begins its pre-start sequence, igniting ten seconds after separation to begin the first of three planned burns.
While the first stage burns RP-1 kerosene and liquid oxygen - LOX, Centaur uses cryogenic liquid hydrogen - LH2 and LOX. Its first burn lasts six minutes and 18 seconds, putting the upper stage and payloads into an initial parking orbit.
Twelve minutes and 15 seconds later, it restarts for a second burn, firing its engine for five minutes and 28 seconds to reach geosynchronous transfer orbit (GTO).
For many launches, GTO is the final destination for the rocket, with the payloads then released to make their way into their operational orbits.
On Friday’s mission, however, the additional power provided by the Atlas V 541 rocket allows a direct insertion to be made into geostationary orbit. This requires a third burn to be made at the apogee – or highest point – of the transfer orbit, so the mission enters an extended coast phase lasting five hours, 15 minutes, and 12 seconds.
Centaur’s final burn lasts two minutes and 26 seconds, circularizing the orbit and zeroing out its inclination. They are now in geosynchronous orbit around Earth.
Three minutes and 16 seconds after verification of insertion, WFOV was deployed into a near-geostationary orbit with a perigee of 36,106 km (22,435 mi, 19,496 nmi), an apogee of 36,168 km (22,473 mi, 19,529 nmi) and inclination of 0.0 degrees.
Once WFOV separated, Centaur reoriented itself, performed another short burn and jettisoned the payload release adaptor that was sitting between the satellites.
The USSF-12 ring separated into a 36,167 by 36,323 km (22,473 x 22,570 mi, 19,529 x 19,613 nmi) orbit 15 minutes and 45 seconds after WFOV’s deployment.
About 26 minutes and 20 seconds later, Centaur will perform a blowdown to help passivate itself, reducing the risk of an on-orbit explosion since deorbiting the stage is not possible with Friday’s mission profile.
The USSF-12 mission will officially end at T+ seven hours, six minutes and 41 seconds.
The Atlas V 541 rocket
The USSF-12 mission launched aboard an Atlas V rocket, operated by United Launch Alliance (ULA). The Atlas V has been a workhorse for the US government’s military and scientific space missions across its first twenty years of service.
Originally developed in 2002 by Lockheed Martin for the US Air Force’s Evolved Expendable Launch Vehicle (EELV) program, Atlas was selected for development alongside Boeing’s Delta IV – which is now also operated by ULA formed in 2006.
Atlas V itself is a two-stage rocket, with a Common Core Booster (CCB) first stage and a Centaur upper stage. Different configurations vary the number of strap-on solid rocket motors (SRMs) that augment the first stage during the initial phase of flight, the size of the rocket’s payload fairing, and the number of engines on the Centaur stage.
USSF-12 Atlas flew in its 541 configuration, which means a five-meter diameter payload fairing, four solid rocket motors, and a single-engine Centaur (SEC). Atlas V has a unique tail number; the USSF-12 mission is AV-094.
Facts on the Atlas V launch vehicle
Height of Atlas V 541: 196 feet (59.7 meters)
Fuel onboard: 91,000 gallons of liquid propellant
First stage Atlas: 25,000 gallon RP-1 - 48,800 gallon LOX
Second Stage Centaur: 13,050 gallon LH2 - 4,150 gallon LOX
LOX+LH2 = 66,000 gallon of cryogenic liquid propellant
150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks
Helium storage tanks: Unknown so far
4 GEM-63 SRB: 400,000 pounds of solid fuel
Mass at liftoff: 1,182,975 pounds (536,180 kg)
Thrust at liftoff: 2.3 million pounds (10.44 mega-Newtons)
Orbit: Geosynchronous - 22,000 miles (35,500 km)
Graphic of Atlas V 541 split in its major pieces. The Ring Spacecraft was once a payload adaptor
Atlas V rocket is filled with 344 472 liter - 91 000 gallons of RP-1, liquid oxygen and liquid hydrogen. They contain 344,47 m3 RP-1, cryogenic oxygen and cryogenic hydrogen.
The Common Core Booster holds 184 728 liter - 48 800 gallon liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 184,73 m3 oxygen tank.
The Common Core Booster holds 94 635 liter - 25 000 gallon RP-1 highly refined kerosine at room temperature that can fit in a 94,64 m3 fuel tank.
The Centaur upper stage holds about 49 400 liter - 13 050 gallons of liquid hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit that can fit in a 49,40 m3 hydrogen tank.
The Centaur upper stage holds about 15 709 liter - 4 150 gallons of liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 15,71 m3 fuel tank.
Still to find is data on Helium gas, pressures used and number of COPV to store it.
150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks to store propellant used for RCS maneuvering during ascent and in orbit.
