Screenshot from ULA Webcast of the launch of NROL-42. Second attempt to launch tonight
Mission Rundown: ULA - Atlas V 541 - NROL-42
Written: December 15, 2022
Just look down. They'll never see You
United Launch Alliance (ULA) launched an Atlas V rocket on Saturday evening, carrying out the classified NROL-42 mission for the United States National Reconnaissance Office. Atlas V 541 lifted off from California’s Vandenberg Air Force Base on September 23, 2017 at 22:49 Pacific Time (05:49 UTC on Sunday).
Notam: NROL-42 will drop of two SRB’s, two fairings and its first stage booster in the red zones
The Atlas V with NROL-42 lifted off from Space Launch Complex 3E (SLC-3E) at the Vandenberg Air Force Base in California.
SLC-3E is the Atlas’ only West Coast launch pad, providing access to high-inclination trajectories such as polar and sun-synchronous orbits useful for optical imaging and the retrograde orbits used by some radar imaging spacecraft.
Orbits with intermediate inclination, such as elliptical Molniya orbits that are usually used by signals intelligence satellites that were delivered on this launch.
The NROL-42 Payload
The use of a Molniya orbit for the NROL-42 who is similar to the NROL-35 mission suggest that the spacecraft was the second member of a new series of highly elliptical orbit (HEO) signals intelligence (SIGINT) satellites, a series that began with the Jumpseat satellites launched aboard Titan IIIB rockets in the 1970s and 1980s.
As no codenames have leaked for the fourth-generation satellite, observers identify them as “Advanced Trumpet”, “Improved Trumpet” or “Trumpet Follow-on”.
From notices to airmen, or NOTAM’s, issued to ensure flight safety along the launch corridor. These show that the rocket flew along a south-south-easterly azimuth along the Pacific coasts of California and Mexico, consistent with the approximately-63-degree Molniya orbit. NOTAM for NROL-42 resemble those issued on the NROL-35 launch.
The Molniya orbit is a special class of highly elliptical Earth orbit, with an orbital period of approximately twelve hours and inclination of about 63.4 degrees. Most of that time is spent looking down on Russia looking for multiple missile launches. Two satellites usually take turns working together with relay of data to a third geostationary satellite.
The Atlas V 541 Launch
About 2.7 seconds before the countdown gets to zero, Atlas ignites its RD-180 first stage engine. At T+1.1 seconds the rocket’s solid rocket motors ignited and the vehicle began its climb away from the launch pad, reaching a speed of Mach 1 within 35 seconds and passing through the area of maximum dynamic pressure, or Max-Q, twelve seconds later.
Atlas’ first stage, or Common Core Booster (CCB), is powered by a single RD-180 – manufactured by Russia’s NPO Energomash and derived from the RD-170 series used by the Zenit and Energia rockets. It burns RP-1 propellant, oxidized by liquid oxygen.
The AJ-60A motors burned for 98 seconds. After burnout, the spent motors remained attached for another thirteen seconds before separating in pairs a second and a half apart.
Payload fairing separation took place towards the end of first stage flight, at three minutes and 24 seconds after liftoff, followed five seconds later by the forward load reactor – a device attached at the top of the Centaur to reduce vibrations within the fairing.
Once the fairing separated, the mission entered a news blackout, with the only further announcement coming via press release confirming a successful launch following spacecraft separation.
The RD-180 continued to fire until a little over four minutes after liftoff, around which time Booster Engine Cutoff (BECO) occurred, with the engine shutting down.
Six seconds after BECO, the spent Common Core Booster was jettisoned, with the Centaur upper stage began its prestart sequence. Centaur’s single RL10C-1 engine ignited ten seconds after stage separation, beginning its first burn of the mission. Trumpet-series satellites are typically deployed directly into Molniya orbit. After separating the NROL-42 payload, Centaur will perform a deorbit burn, propelling itself to a destructive reentry to the south of Australia.
The Atlas V 541 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 72 launches with no complete failures.
The Atlas V 541 rocket, tail no. AV-072 is standing 59.7 meters - 196 feet tall on SLC-3E.
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).
Atlas V rocket is filled with 344 472 liter - 91 000 gallons of RP-1, liquid oxygen and liquid hydrogen. Question is now how much goes to fill each stage and the four tanks. Together they can contain 344,47 m3 RP-1, cryogenic oxygen and cryogenic hydrogen.
Atlas V 541 split in its major parts. This is a generic non mission specific graphic configuration
The Common Core Booster holds 184 728 liter - 48 800 gallon liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 184,73 m3 oxygen tank.
The Common Core Booster holds 94 635 liter - 25 000 gallon RP-1 highly refined kerosine at room temperature that can fit in a 94,64 m3 fuel tank.
The Centaur upper stage holds about 49 400 liter - 13 050 gallons of liquid hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit that can fit in a 49,40 m3 hydrogen tank.
The Centaur upper stage holds about 15 709 liter - 4 150 gallons of liquid oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit that can fit in a 15,71 m3 fuel tank.
Still to find is data on Helium gas, pressures used and number of COPV to store it. And are there tanks to store propellant used to maneuver during ascent and in orbit.
HAZ GAS operations are completed when the hydrazine is loaded. The RCS thrusters on the Centaur stage are using hydrazine as a monopropellant during orbit insertion.
The reaction control system (RCS) includes the ullage pressure thrust from the tanks and consists of twenty hydrazine monopropellant engines located around the stage in two 2-thruster pods and four 4-thruster pods. For propellant, 150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks and fed to the RCS engines with pressurized helium gas, which is also used to accomplish some main engine start up functions.
In the 541 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 541 rocket has a three number configuration code.
The first number represents the fairing diameter size in 4 or 5 meters, so in this instance there is a 5 meter fairing.
The fairing, which is manufactured by RUAG of Switzerland, comes in three different lengths, with this launch using the shortest of these. This measures 20.7 meters (68 feet) in length, while the exact diameter is 5.4 meters (17.7 feet).
As well as encapsulating the payload, the five-meter fairing also encloses the rocket’s second stage, the 10 feet wide Centaur. This encapsulation of Centaur is dangerous on account of hydrogen leaking because it's so volatile. Making a lot of ventilation holes in the lower half of the fairing refuses that danger.
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 4 SRB’s attached to the center core.
The third number shows the number of engines on the Centaur Upper Stage, which is 1 in this configuration. So this means that this rocket will have a 5 meter fairing, 4 solid rocket boosters, and 1 engine bell on the Centaur Upper Stage.
