Screenshot from ULA Webcast of the launch of NROL-101. It’s a ocean view right on the beach
Mission Rundown: ULA - Atlas V 531 - NROL-101
Written: September 6, 2021 - Edit: November 28, 2022
Just jumping the NRO launch line
United Launch Alliance (ULA) will use an Atlas V rocket in the 531 configuration to support and deliver a payload for the National Reconnaissance Office (NRO) – NROL-101.
This was the 17th NRO launch with an Atlas V that debuted three of the new GEM-63 solid rocket boosters from Northrop Grumman — switching away from the old AJ-60A Aerojet Rocketdyne solid rocket boosters.
Liftoff is set from Florida’s Cape Canaveral Air Force Station on SLC-41 at 17:32 Eastern Standard Time (22:32 UTC) on Friday, November 13, 2020.
The Atlas rocket that carried the NROL-101 payload into orbit had tail number AV-090. It was the 86th mission for United Launch Alliance’s workhorse Atlas V rocket and the fourth Atlas V to use the 531 configuration.
From the NOTAM it’s known that the SRB will land in area C and 1st stage will land in area D
The GEM 63s measure 1,6 meter - 63 inches in diameter and 20,12 meter - 66 feet in length. They will be ignited at the launch pad and burn for 94 seconds, each consuming 44,250 kilograms - 97,500 pounds of propellant to produce 371,550 foot pounds (1.65 mega-Newtons) of max thrust to augment the 860,200 pounds (3.83 mega-Newtons) of thrust produced by the RD-180 main engine to power the Atlas V rocket skyward.
The Atlas V 531 stack produces three x 1.65 mega-Newtons plus 3.83 mega-Newtons from the SRB’s and the Core booster - a total of 8.74 mega-Newtons thrust at liftoff.
The United Launch Alliance Atlas V rocket will come off the pad on 1.8 million pounds of thrust produced by the RD-180 main engine and three solids. 8.74 mega-Newtons thrust converts to 1.97 million pounds of thrust. Evidence of throttling down during liftoff?
The NRO is one of the United States’ main intelligence agencies and is tasked with operating and maintaining the nation’s fleet of spy satellites, with its spacecraft designed to gather electronic and photographic reconnaissance data directly, or to support intelligence gathering through other means – such as with communications relays.
While details of most of its spacecraft and its operations are highly classified, past leaks and observation of the satellites in orbit have revealed many details of the types of satellites operated and how they can collect data.
The NROL-101 Payload
As other National Reconnaissance Missions are, the public, and even some members of ULA, are kept out of the loop about the payload. Government satellites are mostly highly classified due to their technologically advanced nature.
The United States government aims to keep this information within the United States as it is highly valuable to world success.
This launch appears consistent with a launch into Molniya orbit (including a dog-leg, somewhere halfway on the dotted line below). But it was later proven to be a medium earth orbit with a high inclination.
The NRO already operates several types of satellite in inclined orbits – including Trumpet signals intelligence satellites and Quasar communications spacecraft in elliptical Molniya orbits and Intruder ocean surveillance spacecraft in low Earth orbits – all at inclinations of around 63.4 degrees.
Some Lacrosse/Onyx radar satellites were launched into 57° orbits. While the next gen. Topaz Block 1 satellites all went to retrograde orbits, perhaps this is Topaz Block2 satellite, reverting to the old 57° orbit.
Topaz Bl 1 was in the medium 5m fairing, but was using an Atlas V-501 launch vehicle.
If NROL-101 is carrying a Quasar payload, it is unlikely to be a single satellite of the same configuration as the most recent geostationary missions, as these fit within a 4-meter payload fairing and the Atlas rockets that carried them only required two boosters.
A single large fourth generation satellite with a MUOS-style dish for mobile terminal communications is possible, or alternatively the mission may include 2-4 smaller satellites sent to replace old existing satellites in this orbit.
The payload is designated USA-310, indicating that NROL-101 is a single large satellite.
The Atlas V rocket
The Atlas V is an expendable medium lift launch system and member of the Atlas rocket family. The rocket is one of the most reliable in the world, having more than 76 launches (As of November 2020) with no complete failures.
Screenshot of Atlas V 531 graphic split in its major parts. Note the 5.4 meter wide fairings mounted on the ‘boat tail’ interstage extension who carries most of the fairing mass load past the 3.1 meter wide Centaur second stage - which is totally encapsulated by the 5.4 meter fairings
The rocket has two stages. The first is a Common Core Booster (CCB), which is powered by an RD-180 engine with two bells and burns kerosene (RP-1) and liquid oxygen (LOx). This is accompanied by up to five strap-on solid rocket boosters. The second stage is the Centaur upper stage, which is powered by one or two RL10 engines and burns liquid hydrogen (LH2) and liquid oxygen (LOx).
In the 531 configuration, the Atlas V is capable of carrying up to 14,067 kg to Low Earth Orbit (LEO), and 6,890 kg to Geostationary Transfer Orbit (GTO).
The Atlas V 531 rocket has a three number configuration code.
The first number represents the fairing diameter size in meters, so in this instance there is a 5,4 meter fairing. The second number denotes the number of solid rocket boosters (SRBs), which attach to the base of the rocket. The number of SRBs for a 5 meter fairing can range from 0 – 5. In this case there will be 3 SRBs attached to the center core.
The third and final number refers to the number of engines on the Centaur Upper Stage, which can be either one or two. In this case there will be one Aerojet Rocketdyne RL-10C engine. So this means that this rocket will have a 5 meter fairing, 3 solid rocket boosters, and 1 engine bell on the Centaur Upper Stage.
Solid Rocket Booster - SRB
The GEM-63 builds on the wealth of experience with solid motor design that Northrop Grumman inherited through its 2018 purchase of Orbital ATK, itself originating from a string of mergers including companies such as Orbital Sciences Corporation, Alliant Techsystems and Thiokol.
The company’s Graphite Epoxy Motor (GEM) series of boosters was originally developed for the Delta II rocket, being introduced with the 7000-series in November 1990.
The name Graphite Epoxy Motor comes from the carbon epoxy composite used in the construction of its casing, making the GEM-40 – as the original version was named – significantly lighter than the steel-cased Castor boosters that had been used on earlier Delta rockets.
The number 63 in the motor’s designation gives its diameter in inches – so the original GEM-40 measured 40 inches, or 102 centimeters, across, while the GEM-63 for Atlas V has a diameter of 63 inches, or 160 centimeters. Each booster is filled with QDL-4, a propellant compound based on hydroxyl-terminated polybutadiene (HTPB).
The GEM 63s measure 66 feet in length. They will be ignited at the launch pad and burn for 94 seconds, each consuming 97,500 pounds of propellant to produce 371,550 pounds (1.6 mega-Newtons) of max thrust to augment the 860,200 pounds of thrust already produced by the RD-180 main engine to loft the Atlas V rocket.
GEM 63s are a lower-cost alternative to the solid rocket boosters that have been used by Atlas V since 2003, yet they deliver the same level of thrust and lift-capacity to enable replacement. They also offer a streamlined process for attaching them to the launch vehicle at the Vertical Integration Facility.
What's more, the upcoming Atlas V launches with the new motors will build flight experience in preparation for using GEM 63XLs on Vulcan Centaur's first flight.
The XL variant will stand 72 feet tall, contain 105,800 pounds of propellant and generate approximately 450,000 pounds of thrust each. They will be the longest single-segment solid rocket motors ever built.
The Space Shuttle’s solid rocket boosters are bigger and more powerful, but they are built of 5 big segments screwed together with the infamous O-rings between the segments.
Atlas V can be fitted with as many as five GEM 63s, the Vulcan Centaur can incorporate up to six GEM 63XLs, depending on the weight of the payload and its orbital destination. All motors will have stationary nozzles.
They are manufactured using state-of-the-art automation and robotics. The cases are filaments wound by computer-controlled winding machines using high-strength graphite fiber and durable epoxy resin.
ULA entered a long-term strategic partnership with Northrop Grumman in 2015 to become the sole provider of solid rocket boosters for Atlas V and Vulcan Centaur.
GEM 63s will be added to future Atlas V missions throughout 2021 using a predefined schedule to complete a full transition in the near future.
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