ULA has delayed the launch of NROL-107, the last NRO mission to the Atlas.

United Launch Alliance (ULA) has canceled an Atlas V launch for the classified NROL-107 Silent Barker mission, which was scheduled for Tuesday. The ULA noted that “due to extreme caution regarding personnel safety, a critical national security payload, and the approach of Tropical Storm Idalia,” the decision was made to return the missile and payload to the Vertical Integration Facility (VIF) on SLC-41.

For the challenging mission of delivering a payload to near geostationary orbit, Atlas V will fly in its most powerful active configuration: the Atlas V 551.

Launch of NROL-107 Silent Parker

Silent Barker is a joint project of the National Reconnaissance Office (NRO) and the US Space Force, which has been developed for almost three years. According to the published budget review,SILENTBARKER will provide the ability to search, detect and track objects using space sensors for timely redundancy and event detection.

Essentially, this means that Silent Parker will form a constellation of “surveillance” satellites used to track the activities of other nations in geostationary orbit. This is in contrast to current geostationary tracking methods, which use ground-based facilities that can track objects up to the size of a basketball, depending on the weather on the ground. Silent Barker can track small objects and constantly monitor their position and movement.

This launch, which is expected to be one of two proto-constellation launches, will carry a large number of satellites, though the exact number is being kept under wraps. The NRO will manage the constellation, which is expected to become operational in 2026.

In accordance with the stated launch requirements, the Silent Barker payload will be placed into a zero-inclination orbit of 41,849 x 42,479 kilometers located in slot 105 degrees east longitude. As a result, the satellite will be at an altitude of about 7000 kilometers above the geostationary orbit. It is not known where the satellite will move after it is deployed.

But before any action can be taken in orbit, Silent Parker must first be launched.

The Atlas V launch pad began to take shape in early August. The first stage was first installed on the mobile launch pad, followed by five GEM-63 solid propellant rocket engines (TRDs) and the Centaur upper stage in a five-meter payload base.

On August 11, the entire assembly, with the exception of the payload, was rolled out to the SLC-41 launch pad. There, the cars held a dress rehearsal (WDR). As the name suggests, this event is a dress rehearsal of the launch day events, starting with fuel loading and ending just before the engine is started. This helps resolve any potential issues with the integrated launch vehicle and ground support systems prior to launch day.

Many ULA launches do not include a pre-flight WDR. However, customers may request larger or more expensive shipments. Such tests are commonly used on missions such as Boeing Starliner flights, NASA science missions, and NRO payloads.

An enlarged view of the configuration of the Atlas V 551, the most powerful flying version of the Atlas V. This rocket will lift the NROL-107 into orbit. (Photo: United Launch Alliance)

Once the WDR is complete, the Atlas V returns to the Vertical Integration Center to install the load. Although cryogenic liquid oxygen and liquid hydrogen fuel were removed from the vehicle prior to the recall, there was no RP-1 first stage fuel. This is because RP-1, a purified form of kerosene, is stable at room temperature and can stay in a car for a long time compared to cryogenic fuel.

The NROL-107, housed inside a five-meter-wide payload interface, is lifted onto the entire launch vehicle before the completed rocket returns to the launch pad.

On launch day, Atlas V will be filled with the remaining cryogenic propellants, liquid oxygen and liquid hydrogen. The first-stage engine RD-180 RP-1 burned liquid oxygen and liquid oxygen, and the second-stage engine “Kentavr” RL-10S-1-1 burned liquid hydrogen and liquid oxygen.

Both the RD-180 engine and the Centaur upper stage are derived from earlier Atlas vehicles. The Centaur flew as the second stage of the Atlas rockets from May 1962 on the Atlas Centaur, the rocket that launched the Surveyor lunar rover, several Mariner missions to Mars, and Pioneer 10 and 11 to Jupiter and Saturn. However, the RD-180 is newer, having entered service with the short-lived Atlas III in 2000. Although the RD-180 will be retired along with the Atlas V at the end of the decade, the Centaur has been further developed for the upcoming aircraft. Volcano. .from ULA. rocket.

The countdown will move into a scheduled break at minute T-4, after which ATLAS Mission Control will conduct a final check for all flight controllers to ensure the ship is safe and ready for launch. If all controllers respond “go ahead”, the hold will be released immediately.

During the last four minutes of the countdown, the fuel will be charged and the tanks will be pressurized for flight. At T-2.7 seconds, the RD-180 engine caught fire, and the on-board computer independently checked all the engines and systems of the vehicle. If the engine and vehicle as a whole are working properly, the computer instructs five SRMs to fire simultaneously and release the trigger clamps, allowing the vehicle to take off from the launch pad in T+1 second.

Thanks to the high thrust of five GEM-63 SRM Atlas V rockets, it will become supersonic in just 35 seconds after launch. In just 11 seconds, the car will reach its maximum Q, which is the period of maximum dynamic load on the car. After this point, the aerodynamic load on the ship will drop to almost zero as the rocket hits a vacuum.

View from the flight of the second stage of the Centaur on the previous Atlas V launch, showing the deceleration of the booster stage. (Photo: United Launch Alliance)

One minute and 44 seconds after launch, the SRM will burn out and be ejected. They will be divided into groups of two and groups of three with two seconds between them.

The next event is a discharge of T+3 minutes 5 seconds, as a result of which the Centaur and Silent Barker payloads will be launched into outer space. This removes some of the dead mass. The protective cover is no longer needed, as the machine will be in a vacuum. The two front-loading reactors of the Centaur will also be thrown in a few seconds. This equipment transfers some of the load on the structure from the payload sensor to the sides of the fairing, reducing the overall load on the thin walls of the Centaur’s tank during its initial flight at high acceleration.

Due to the classified nature of the mission, the published launch schedule does not include details of other mission activities. However, based on previous Atlas V 551 flights, the Atlas booster – or first stage – caught fire and separated after about four and a half minutes of flight. The Centaur will then begin the first of three or four possible burnouts, placing its payload into low Earth orbit. The RL-10 engine then turns off and the stage moves.

After hovering for a while, the RL-10 will turn on a second time, sending the group into geostationary transfer orbit. The scene will cut into the Beach scene again, this time for about five to six hours.

Near aphelion, the highest point in geostationary transfer orbit, the Centaur will fire its RL-10 thrusters for the third time, placing the Silent Barker into synchronous Earth orbit. The satellite would then be deployed and the Centaur would eject the remaining propellant or fire its engines one last time, orbiting the graveyard to get rid of it.

This will be the 98th Atlas V mission and the second this year for United Launch Alliance. It also closes a chapter in the Atlas V story. NROL-107 will be the last NRO payload to launch on the Atlas V, as all other ULA reconnaissance missions will fly on the upcoming Vulcan rocket.

(TOP PHOTO: Atlas V rolled out to launch pad SLC-41 ahead of AEHF-6 mission in March 2020. Image courtesy of United Launch Alliance)

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