December 6th, at 4:04 AM Est from SLC-41 at Cape Canaveral Space Force Station
STP-3 or Space Test program -3 is a mission for the U.S. Space Force Space Systems Command. A mission that matures technology and reduces further space program risk for the Department of the Air Force, and Space Force. The mission will launch using a ULA (United Launch Alliance) Atlas V rocket in the 551 configuration. The general purpose of this mission is to advance warfighting capabilities in areas of nuclear detonation detection, space domain awareness, and communications. It’s a co-manifested mission, meaning there is two spacecraft aboard the rocket, both will be delivered to a geosynchronous orbit. Geosynchronous orbits are perhaps the most difficult to insert to. It is a highly complex situation which requires three Centaur burns and precise navigation, which a capability unique to the Atlas V. With it taking over seven hours to get into that orbit this mission is the longest for ULA to date.
The STP spacecraft or STPSat-6 is the primary craft on this mission with a smaller rideshare of the Long Duration Propulsive Evolved Expendable Launch Vehicle. Both vehicles were built by Northrop Grumman, and the STPSat-6 payloads include the Space Atmospheric burst Reporting System 3 (SABRS-3), NASA’s Laser Communication Relay Demonstration (LCRD) payload which will test technologies for the next generation of data relay satellites and multiple DoD (Department of Defense) space experiments review board space weather and situational awareness payloads. What we do know about the Long Duration Propulsive Evolved craft is that it is designed for a one to three year mission and carries experimental payloads.
This mission also debuts three United Launch Alliance engineering features that are designed to reduce risk and accumulate flight experience before used on the Vulcan Centaur. The first being OoA (Out of Autoclave) payload fairings. These fairings were developed using a new method, an alternative way to cure carbon fiber composites which allows for a more efficient production process at a lower cost. They also weigh less and are able to maintain the same level of reliability and quality as the previous fairings. At 17.7ft or five meters these fairings encapsulate the spacecraft inside to protect them during their ascent into space. They are a composite structure made with a vented aluminum honeycomb core and graphite epoxy face sheets. When on top of the launch vehicle it brings the total height of Atlas V up to 196ft tall.
Secondly ULA is introducing an in-flight-power system or IFPS. This system supplies power to the satellite’s batteries during the rocket’s long duration ascent, which lasts more than seven hours. The IFPS will ensure the spacecraft have fully charged batteries as they are deployed into their desired geosynchronous orbit.
Lastly there will be an enhanced navigation GPS system which utilized existing flight computer hardware to provide GPS signals to improve Centaurs navigation system performance to allow the rocket to achieve more accurate orbits.
An Atlas V booster is 12.5ft in diameter and 106.5ft in length. Its tanks are made from isogrid aluminum barrels, spun-formed aluminum domes and intertank skirts. Its propulsion is provided by a single Russian made RD-180 engine system that burns RP-1 (Rocket Propellant 1, or purified kerosene and liquid oxygen. Its total thrust is around 860,200lbs. These 551 variants of the Atlas V means it has five SRBS (Solid Rocket Boosters). These Gem-63 SRBs will bring the total thrust of the vehicle up to about 2.5 million pounds.
Originally scheduled for December 5th at 4:04 AM Est the ground teams quickly discovered a leak in the RP-1 ground storage system as they began to load propellant into the Atlas V. It was said that about 2,200lbs of fuel were lost in the surround area. Teams worked tirelessly to get the situation fixed and get the “Bruiser” as the Atlas V 551 is nicknamed off the ground just twenty-four hours after the initial launch time. Weather stayed the same for those hours as well, a 90% GO for launch forecast held as predicted by Space Launch Delta 45, and it was a crisp beautiful morning on the space coast during launch time.