Screenshot from ULA Webcast of the launch of NROL-79. Such clear blue skye is seldom seen
Mission Rundown: ULA - Atlas V 401 - NROL-79
Written: December 22, 2022
In the Navy We look for other ships
For its second launch of the year, the Atlas V rocket marked its 70th mission to space on Wednesday as the veteran rocket lofted the National Reconnaissance Office’s NROL-79 spacecraft to Low Earth Orbit (LEO).
Liftoff took place from SLC-3E at Vandenberg Air Force Base, California, on March 1, 2017 at 09:50 PST (17:50 UTC), the opening of a 40 minute launch window. The mission has been declared a success.
The NROL-79 Payload
The NROL-79 payload contains most likely two NOSS 3 satellites of the Intruder class surveillance satellite network.
The Naval Ocean Surveillance System - NOSS 3 carry equipment to track ships and aircraft via their radio transmissions. Positions of the origin of the transmissions are determined by triangulation. Each launch consists of two satellites of similar size in the same orbit. Both satellites maneuver to stationkeep relative to one another.
Both satellites are built by Lockheed Martin as third generation surveillance satellites.
While the exact orbital destination for NROL-79 has not been revealed, all previous NROL missions from Vandenberg have been non-GTO (Geostationary Transfer Orbit) missions to either LEO or Molniya orbits (highly elliptical, high inclination orbits with arguments of perigee of -90 degrees and an orbital period of one half of a sidereal day). ‘12 hours.’
The precise launch time indicates that NROL-79 is a replacement mission with intent to relieve two existing satellites in their orbit. Only launches to the ISS have a one second launch window in order to catch the precise orbit trajectory.
The Atlas V 401 Launch
A final launch verification took place at T-16 seconds, leading to the start sequence of the RD-180 engine at the base of the Atlas V core at T-2.7 seconds.
After ramping up to full thrust and a series of health checks, the hold down clamps released and the Atlas V lifted off at T+ 1.1 seconds.
While the exact orbital destination for NROL-79 has not been revealed, all previous NROL missions from Vandenberg have been non-GTO (Geostationary Transfer Orbit) missions to either LEO or Molniya orbits (highly elliptical, high inclination orbits with arguments of perigee of -90 degrees and an orbital period of one half of a sidereal day).
Given this, the NROL-79 Atlas V 401 can be expected to follow an LEO ascent profile, with the RD-180 engine producing 860,000 lbf at liftoff, a level of thrust that will gradually increase to 933,000 lbf as the vehicle breaks through Earth’s atmosphere and enters the vacuum of space.
In its 401 configuration, the Atlas V reached Max Q – the moment of maximum dynamic pressure and mechanical stress on the vehicle – 88 seconds after liftoff at an altitude of 11.6 km (37,970 ft) with a total Max Q of 490 psf - pound square feet.
Throughout the first 100 seconds of flight, the RD-180 engine thrusted at 100% of total throttle, stepping down to 95% of rated thrust from 100 seconds through 210 seconds, at which point a throttle drop off occurred as the booster maintained a 5G acceleration limit in preparation for Booster Engine Cutoff (BECO).
BECO occurred just prior to Atlas/Centaur separation at the T+ 246 second mark at an altitude of ~157.6 km (~517,015 ft).
Ten seconds after Atlas core stage separation, the Centaur single-engine upper stage ignited at the T+ 256 second mark.
Payload fairing jettison followed at T+ 264 seconds at an altitude of 193 km (633,100 ft).
Once payload fairing jettison occurs, per the NRO’s usual request to ULA, the live webcast ceases, and the final portion of launch operations and placement of the satellite into orbit will not be seen live.
However, the US Air Force later confirmed a successful deployment.
The Atlas V 401 rocket
Saturday's launch of United Launch Alliance’s Atlas V flying in the 401 configuration.
The Atlas V, tail number AV-068, consists of a Common Core Booster (CCB) first stage, with a single-engine Centaur (SEC) upper stage and a four-meter payload fairing fitted atop the Centaur. Although the Atlas V can fly with up to five Aerojet AJ-60A solid rocket motors boosting the first stage, AV-068 will use none.
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 70 launches with no complete failures.
The Atlas V 401 rocket, tail no. AV-068 is standing 58.23 meters - 191 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 401 split in its major parts. This is a generic non mission specific graphic configuration
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.
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 there are 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 401 configuration, the Atlas V is capable of carrying a structural maximum of 9,050 kg to Low Earth Orbit (LEO), and 4,950 kg to Geostationary Transfer Orbit (GTO).
The Common Core Booster contains a total of 284,089 kilograms - 626,309 pounds of RP-1 kerosene and liquid oxygen, weighs 306,271.7 kilograms - 675,213.5 pounds fully fueled, and is 35.63 meters - 116,9 feet tall and 3.81 meters - 12,5 feet wide.
Its RD-180 main engine produces 3,826.9 kilonewtons - 860,321.35 pounds of thrust at sea level while the thrust level increases to 933,406.73 pounds in space.
The Centaur V1 upper stage contains 20,830 kilograms - 45,922.3 pounds of liquid hydrogen and liquid oxygen, weighs 23,073 kilograms - 50,867.3 pounds fully fueled, and is 12.68 meters - 41,6 feet tall & 3.05 meters - 10 feet wide.
Its RL-10C-1 engine is optimized for vacuum usage, so it only produces 101.8 kilonewtons - 22,885.55 pounds in space.
The Atlas V 401 weighs 338,149.7 kilograms - 745,492.48 pounds, including the NROL-79 spacecrafts; and is 58.23 meters - 191 feet tall and 4.2 meters - 13,8 feet wide.
The NROL-79 two spacecraft weighs a maximum of 6,500.0 kilograms - 14,330 pounds on their own, that’s with the fairings weight excluded. If all weight numbers are right then the NROL-79 two spacecraft weighs 6,218.0 kilograms - 13,708 pounds.
The Atlas V 401 LPF fairings weigh 2,487.0 kilograms - 5,482.9 pounds. The weight of a 3 foot fairing extension is estimated to be a small part of the LPF fairing. 100 kg at most.
Doing the math: 306272 kg + 23073 kg + 6218 kg + 2487 kg + 100 kg = 338150 kg.
The Atlas V 401 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 4 meter fairing. This launch will use the 13.1-meter long (43 ft) EPF.
The standard four-meter fairing, named the Long Payload Fairing (LPF), measures 12.2 meters (40 feet) in length and was first introduced as an optional larger fairing for the Atlas I rocket in 1990.
The three Payload Fairings. The height difference is negligible unless you're a satellite so a weight increase of 100 kilo pr. 3 feet extension when the smallest weighs 2487 kg are within reason
One or two 90-centimeter (3-foot) cylindrical segments can be added to the fairing to form an Extended Payload Fairing (EPF) 13.1 meters (43 feet) or Extra-Extended Payload Fairing (XEPF) 14.0 meters (46 feet) respectively for payloads that require the additional space.
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 no 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 4 meter fairing, no solid rocket boosters, and 1 engine bell on the Centaur Upper Stage.
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