ULA scrubs Space Force missile tracking satellite, first Atlas V launch of 2021
United Launch Alliance (ULA) has scrubbed the Atlas V launch at Space Launch Complex-41 (SLC-41)… The post ULA scrubs Space Force missile tracking satellite, first Atlas V launch of 2021 appeared first on NASASpaceFlight.com.
United Launch Alliance (ULA) has scrubbed the Atlas V launch at Space Launch Complex-41 (SLC-41) at the Cape Canaveral Space Force Station ahead of its mission to loft a new Space Based Infrared System (SBIRS) military reconnaissance satellite into Geostationary transfer orbit. Liftoff of SBIRS GEO-5 is now set for no earlier than Tuesday, 18 May at approximately 13:31 EDT / 17:31 UTC.
The flight will mark the first 2021 launch of ULA’s Atlas V rocket and the second launch made by the company this year following the April launch of NROL-82 which utilized a Delta IV Heavy launch vehicle. The Atlas V is configured in the 421 variant, meaning it utilizes a 4 meter diameter fairing, two solid rocket boosters and single engine centaur upper stage.
The Space Based Infrared System
The United States Space Force’s (USSF’s) Space Based Infrared System was born during the 1991 Gulf War, when the US Military realized its missile warning capabilities were lacking and a new system would be needed in order to allow the country to quickly and accurately track short- and long-range missile launches from around the world.
Prior to SBIRS, the US military’s missile warning capabilities were provided by the Defense Support Program (DSP), a constellation of 23 satellites launched between 1970 and 2007. Although this system was useful in providing missile early warning capabilities, shortcomings experienced while using the system during the Gulf War made it clear the DSP would need to be replaced by a more advanced system.
The US Air Force later chose Lockheed Martin to build that system, which became SBIRS.
SBIRS was split into two different categories, the first being SBIRS Low (also known as SBIRS HEO) which was initially to consist of two satellites in a highly eccentric orbit known as a “Molniya orbit“. The second category was known as SBIRS High (or SBIRS GEO), initially set to consist of two satellites located in Geostationary Orbit.
Each SBIRS GEO spacecraft utilizes a suite of two advanced sensors, allowing them to detect short- and mid-wave infrared signals, providing data which can be used to track missile launches from around the world. The constellation has very quickly proven its worth; according to Lockheed Martin, the SBIRS system detected nearly 1,000 worldwide missile launches in 2019 alone.
After the system first came online in 2013, the US Air Force awarded Lockheed Martin a set of contracts to expand the constellation, ordering a third HEO spacecraft in 2009 followed by a third and fourth GEO satellite that same year.LIVE Atlas V/SBIRS GEO-5 UPDATES
In 2014, the US Air Force awarded Lockheed Martin a contract for a fifth and sixth GEO satellite. Contracts for GEO-7 and GEO-8 were also awarded, but those spacecraft were cancelled in 2019, and GEO-6, scheduled for launch next year, is now set to be the final spacecraft that will join the SBIRS High constellation.
When GEO-5 was ordered alongside GEO-6, the two spacecraft were initially supposed to be identical to the four SBIRS High satellites that have preceded them, which used Lockheed Martin’s A2100 satellite bus.
During the development of GEO 5 and 6, it was decided to instead use the modernized LM2100M (Modernized Military) bus, which is developed specifically for military operations.
The LM2100M is designed to be more resilient to cyber attacks and contains an upgraded suite of power and propulsion equipment.
The modular design of the spacecraft also allowed for a much more streamlined manufacturing process.
The launch of GEO-5 will mark the first flight of the new spacecraft design, although the US Space Force has already awarded contracts to Lockheed Martin for at least 26 satellites built on the LM2100M design, one for GEO-6, three for the branch’s Overhead Persistent Infrared (OPIR) missile warning constellation, which is set to start replacing SBIRS from 2025, and 22 for the next generation of Global Positioning System (GPS) satellites.
The ULA Atlas V 421 rocket is scheduled to liftoff from SLC-41 at 17:35 UTC, though there is an undisclosed window and the launch period is not instantaneous.
The rocket’s first stage is powered by an RD-180 main engine and supplemented on this flight by two AJ-60A solid rocket boosters from Aerojet Rocketdyne, all together providing around 6,700 kN of thrust at liftoff according to ULA — increasing to over 7,100 kN during first minute and a half of ascent.
After 47 seconds of flight, the rocket will break the sound barrier and pass Mach 1, followed less than a second later by MaxQ, the period in the launch where the Atlas V will experience maximum aerodynamic pressure.
At T+2 minutes 9 seconds into the flight, the two AJ-60A solid rockets will be jettisoned more than 30 seconds after burnout, allowing them to begin their fall back safely back to Earth. They are held by the Atlas V first stage for such a prolonged period after burnout to ensure a clean separation from the vehicle based on aerodynamics.
The first stage will then continue to burn until T+4 minutes10 seconds, when the RD-180 will cutoff, followed six seconds later by first stage separation. The Centaur upper stage will coast for 10 more seconds before its single
The payload fairing, which will protect the satellite as the rocket rips thought the thickest parts of the atmosphere, will be deployed at T+4 minutes 34 seconds, as the atmosphere will then be thin enough to allow for SBIRS to be safely exposed to the elements.
At 15 minutes 06 seconds into the flight, Cenatau’s RL10C-1-1 engine will cut off, placing the vehicle into an initial parking orbit. Almost immediately, two rideshare payloads, EZ-3 and EZ-4, will deploy from Centaur.
EZ-3 and -4 are technology demonstration satellites for the US government testing experimental data for the US Air Force Academy.
A 15 minute coast phase will follow, with Centaur engine reignition at T+31 minutes 06 seconds. This 3 minute 21 second burn will place SBIRS and Centaur into the mission-specific Geostationary transfer orbit, (GTO), of 925.2 x 35,753.2 km with an inclination of 21.14 degree, down from the initial 28.5 degree inclination at liftoff.
From this orbit, the spacecraft will begin the process of moving itself into its planned Geostationary orbit location.
Lockheed Martin will then officially hand over control of the spacecraft to the USSF’s Overhead Persistent Infrared Battlespace Awareness Center at Buckley Air Force Base, Colorado, who will control it from their on.
Space Launch Delta 45
Besides marking the first flight of a new generation of missile warning satellites, the mission also marks the first launch since the US Space Force re-named the 45th Space Wing to Space Launch Delta 45.
In the last 12 months, the 45 SW planned for 230 launches, went into 59 countdowns & launched 39 missions. While at one time our goal was “Drive to 48," we now avoid a specific number and simply say “Set the Pace for Space” because two launches a day may soon be a reality! (1/3)
— Space Launch Delta 45 (@SLDelta45) May 12, 2021
Since the early 90s, all launches from Florida’s eastern range have been managed by the 45th Space Wing, initially a US Air Force unit that was transferred over to the Space Force when the branch was created in late 2019.
As part of the Space Force’s restructure, moving it away from its Air Force heritage as it establishes its own vocabulary and structure, the 45th Space Wing was renamed Space Launch Delta 45, alongside the Western Range’s 30th Space Wing which was renamed to Space Launch Delta 30.
(Lead image: Atlas V on the pad ahead of SBIRS GEO-5. Credit: Stephen Marr for NSF)
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