Screenshot from ULA Webcast of the launch of NROL-107. Mind the Dog. It don’t bark, but it bites
Mission Rundown: ULA - Atlas V 551 - NROL-107
Written: September 10, 2022
Finally another launch
ULA (United Launch Alliance) launched its 98th flight with an Atlas V 551 rocket and its second mission of 2023. Launching from SLC-41 (Space Launch Complex 41) in Cape Canaveral, Florida, the NROL-107 mission is lofting an intelligence satellite for the National Reconnaissance Office.
The mission will also test several new technologies onboard the company’s Atlas V launch vehicle during the longest duration mission for an Atlas rocket to date. Liftoff occurred on September 10 at 08:47 EDT (12:47 UTC) after holding for hurricane Adelia.
The attachment of five side-mounted solid rocket boosters (SRBs) to the Atlas first stage will generate three-quarters of the energy necessary at liftoff to power the vehicle on to a complex, seven-hour flight. The core Atlas V booster will do the remaining 25%.
NOTAM hazard areas where Atlas V 551 will drop off SRB boosters, fairings and 1st stage
The number 5 obviously means a 5 meter fairing. The second number determines the number of strap on solid rocket boosters (SRBs). It can range from 0 to 5, and in this case, there are five on various sides of the center common core.
The third and final number refers to the number of engine bells on the Centaur Upper Stage, which can be either one or two. In this case there will be one engine. The only time that there have been two engines (while on an Atlas V) was on Starliner’s OFT-1. So to review, for the NROL-107 mission, this rocket has a five-meter fairing, five solid rocket boosters, and one engine on the Centaur Upper Stage.
It’s unique to the Atlas rocket to have their solid rocket boosters (SRBs) positioned in this way. When, like in this case, 5 SRBs are used, they are positioned with two on one side and three directly opposite of them. If you notice carefully in the image of Atlas core boosters, there are long and somewhat flat pipes “running” down the side of the first core stage.
These are raceways and carry fuel from the tanks down to the engines and some carry gasses back up to the tanks to pressurize them so the fuel stays flowing out the pipes.
When Atlas was designed, these two raceways were placed in their positions without the thought of SRB placement. So when more SRBs were needed, they were placed in the most convenient spot. Two SRB between the raceways and three opposite them.
The offset of the thrust won’t make it fly in the wrong direction. The engines on the core stage can gimbal, they counteract that offset of thrust by vectoring their thrust which is known as Thrust Vector Control, or TVC. The SRBs, and most of them for that matter, do not have TVC abilities, but their nozzles can be angled and turned slightly sideways. That will counteract some of that offset SRB thrust.
During the NROL-107 mission, ULA plans to demonstrate three new technologies onboard its Atlas V rocket: a new fairing design, an upgraded power system for the spacecraft, and what the company calls “Enhanced Navigation.” All of these technologies will feature on the company’s future Vulcan Centaur rocket.
Manufactured in Decatur, Alabama–right next door to ULA’s factory–by RUAG Space, the new fairing uses a manufacturing method called Out-of-Autoclave, and will replace the fairings made by RUAG in Switzerland. While they are the same size as previous Atlas V 5.4 meter-class fairings, the new process “weighs and costs less while being easier and quicker to make,” according to ULA.
Due to NROL-107’s nearly seven hour journey to a circular geosynchronous orbit, the Atlas V rocket is flying for the first time with what the company calls an IFPS (In-Flight Power System) which keeps the batteries of both spacecraft fully charged throughout the flight. This means that the spacecraft have more time on battery power before needing to rely on their deployable solar panels after separation from the Atlas V’s Centaur upper stage.
ULA is also debuting what the company refers to as “Enhanced Navigation,” a system that uses GPS data to compliment the rocket’s onboard flight computer in order to increase orbital insertion accuracy. According to ULA, the system was tested on previous launches, and “will be available for use on all Atlas V missions going forward.”
The ULA-manufactured upper stage for Boeing’s Space Launch System, called ICPS, will also use “Enhanced Navigation.” ICPS is short for Inner Cryogenic Propulsion System and is a modified Centaur second stage loaded with liquid Hydrogen and Oxygen.
The NROL-107 Payload
NROL-107 is a dedicated launch for the U.S. Space Force’s Space Test Program. The program is designed to fly experimental payloads in order to mature technologies for future Department of Defense missions. The NROL-107 mission is composed of one primary spacecraft as its payload.
NROL-107's primary spacecraft is known as Silent Barker, which is a joint project of the National Reconnaissance Office (NRO) and the United States Space Force that has been in development for approximately three years.
According to budget reviews, “SILENTBARKER will provide the capability to search, detect, and track objects from a space-based sensor for timely custody and event detection.”
This essentially means that Silent Barker will form a “watchdog” constellation of satellites used for tracking other countries’ activities in geostationary orbit.
This departs from the current method of geostationary tracking using ground-based assets, which can track objects down to the size of a basketball — depending on the weather on the ground. Silent Barker can track smaller objects and continuously observe their position and movement.
This launch, expected to be one of two in total for the initial constellation, will have multiple satellites on board — although the exact number is classified. NRO will operate the constellation, which should be operational by 2026.
From the publicized launch requirements, the Silent Barker payload will be launched into a 41,849 by 42,479-kilometer orbit with zero inclination, positioned at the 105-degree East slot. This places the satellites around 7,000 kilometers above a proper geosynchronous orbit. It is unknown where the satellites will maneuver themselves following deployment.
The Atlas V 551 rocket
The Atlas V core for this mission is AV-100 ?. Atlas V 551 stacking will begin working in the coming days, five GEM 63 solid rocket boosters and the Centaur upper stage with its RL10C-1 engine will be hoisted into place. NROL-107 payload attachment occurs after the ‘Wet Dress Rehearsal’ on August 11 with a rollout to Space Launch Complex-41.
Inside the Vertical Integration Facility − VIF, a team of engineers fastened the payload fairing, which houses the NROL-107 spacecraft.
The mission is scheduled to launch on September 10 from Launch Complex 41 on CCSFS, with a two-hour launch window beginning at 6:04 a.m. EDT.
Graphic illustration of the Atlas V 551 split in its major parts. The spacecraft is a generic model
The fully stacked rocket and payload stands 196 feet tall and is anticipated to roll out on a mobile launch platform from the VIF to the launch pad on Sep. 9.
The Centaur second stage will remain attached until 4 minutes, 33 seconds after launch, and deployment of NROL-107 is scheduled about 6 hours, 30 minutes after launch.
On September 9, the Atlas V 551 was rolled from its Vertical Integration Facility to its launch pad at Space Launch Complex 41. The rocket’s first stage was already filled with its RP-1 kerosene fuel, which can be loaded ahead of time as Atlas V does not yet rely on the use of super-chilled kerosene, such as Falcon 9.
Seconds before launch, the RD-180 engine on the first stage ignited. At T-0 seconds, the five GEM-63 solid rocket boosters ignited, followed by liftoff at T+1.1 seconds.
About 35 seconds after launch, the Atlas V passed the speed of sound, or Mach 1. Only 11 seconds later, the Atlas V will reach max-Q, which is the period of maximum dynamic pressure on the vehicle.
At T+1:47 after launch, all five solid rocket boosters were jettisoned. First, two separated, followed by the other three about two seconds later. The payload fairing separated from the rocket at T+3:05 after launch.
At about T+4:30 after launch, the RD-180 engine on Atlas’ first stage shut down, and the Centaur upper stage carrying the NROL-107 payloads separated. Centaur’s RL-10C-1-1 engine should then burn for about six minutes to reach an initial low earth orbit.
Reaching the equator on the descending node some ten minutes later the Centaur ignited once more and burned for about six minutes to raise the orbit's apogee, or highest point in the orbit, to a geostationary altitude. If its second burn is delayed to the ascending node, then it will burn 45 minutes later passing over Java.
After a roughly six to seven hours long coast phase, the Centaur ignited again, circularizing its orbit and changing its orbital inclination from about 27.5o degrees to zero degrees with a roughly three minute burn.
At seven hours and 30 minutes after launch, NROL-107 should be deployed.
The upper stage Centaur’s RL-10 engine depleted its last reserves of propellant to lift itself into a graveyard orbit some 42 000 km away from earth. The remaining gasses and fuel vapors will be vented at apogee in order to raise the perigee just a little.
The Centaur’s propellant tanks must be empty to avoid exploding like a rotting toad in the sunlight. At least three upper stage Centaur’s weren't purged and exploded in 10-15 large tumbling pieces of space debris.
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