Screenshot from ULA Webcast of the launch of NROL-55. No wind, no light and no matches around
Mission Rundown: ULA - Atlas V 401 - NROL-55
Written: January 7, 2023
Take fiftyfive. And we’re rollin’
United Launch Alliance’s Atlas V rocket successfully deployed a National Reconnaissance Office primary payload (NROL-55) – and a host of smaller satellites – Thursday following a pre-dawn liftoff from SLC-3E at Vandenberg Air Force Base.
Liftoff was on schedule at 05:49 Pacific Daylight Time - 12:49 UTC on October 8, 2015.
Just six days after another Atlas flew United Launch Alliance’s (ULA’s) one-hundredth mission with launching Mexico’s Morelos-3 satellite last Friday, Thursday’s launch marked the shortest time between two Atlas V launches.
Atlas V 401 flight path measures 2200 km ±100 km indicates a steep climb into its orbit since the impact area of the core booster is 400 km closer to the launch site at Vandenberg Air Force Base
The NROL-55 Payload
Thursday’s launch, designated NRO Launch 55, or NROL-55, is carrying an unspecified primary payload for America’s National Reconnaissance Office (NRO).
While the nature of this payload is classified, as is usual for NRO missions, much can be inferred from the configuration of the rocket carrying the payload and airspace closures and hazard areas which give away the course that the rocket will take.
In the case of NROL-55, the Atlas V – tail number AV-058 – flew in its 401 configuration, which consists of a Common Core Booster first stage, a single-engine Centaur second stage, no attached solid rocket motors and a payload fairing with a diameter of 4 meters.
This configuration has been used to launch two types of NRO spacecraft – a constellation of communications satellites known as the Satellite Data System (SDS) or Quasar; and ocean reconnaissance spacecraft known as the Naval Ocean Surveillance System (NOSS), or Intruder.
Thursday’s launch used the Extended Payload Fairing which has previously been used for Intruder launches – while Quasar has used the Large Payload Fairing. This points towards NROL-55 carrying an Intruder payload – which is supported by similarities between the hazard areas for Thursday’s launch and the last Intruder launch in 2012, NROL-36.
The Atlas V 401 Launch
Details of the mission profile or flight plan for Thursday’s launch were not revealed – however, a fairly typical two-burn ascent to low Earth orbit can be expected.
The first stage – or Common Core Booster – ignited its RD-180 engine 2.7 seconds before the countdown reaches zero, with the rocket lifting off at about T+1.1 seconds. Rolling to a southeasterly heading along the coast of California – as indicated by the launch hazard areas – AV-058 pitched over for her climb into orbit.
A little over a minute into the flight the RD-180 engine throttled down as the vehicle passed through the area of maximum dynamic pressure, or Max-Q. After navigating this period of flight the engine again throttled up to continue its burn.
First stage powered flight lasted a little over four minutes, with the RD-180 again throttling down a few seconds before cutoff to limit the rocket’s acceleration.
The Centaur second stage separated from the spent Atlas booster about six seconds after cutoff, with the stage’s RL10 engine igniting ten seconds later and the payload fairing separating from the nose of the rocket after a further fifteen seconds. Due to the nature of the mission, live coverage ended at this point of the launch.
Most Centaur stages are now powered by RL10C-1 engines, a new version of the RL10 which was introduced late last year; however, there have been occasional launches that have made use of the older RL10A-4-2. ULA has not announced which engine will be used on Thursday’s mission. This photo is of the Centaur single engine bell.
The first RL10 burn lasted about fourteen and a half minutes, establishing an initial parking and transfer orbit. Following an hour-long coast phase, Centaur restarted for a second burn of around 60 seconds that will circularize the orbit.
Spacecraft separation occurred two minutes after the second burn concludes, based on estimates, with the two NOSS satellites remaining attached to each other at the point of separation from the Atlas, before dividing to begin their mission.
Following deployment of its primary payload – which required an orbit of approximately 1,000 by 1,200 kilometers (620 by 750 miles; 540 by 650 nautical miles) at an inclination of 63.4 degrees, the Centaur maneuvered to deploy its secondary payloads.
Wanna go for a ride?
Accompanying NROL-55 were thirteen CubeSats which comprise the NRO’s Government Rideshare Advanced Concepts Experiment (GRACE). Like the earlier OUTSat, GEMSat and ULTRASat missions, this used a Naval Postgraduate School CubeSat Launcher (NPSCUL) attached to the Centaur’s Aft Bulkhead Carrier to deploy the satellites.
The 13 CubeSats will be deployed from a similar dispenser placed on the Centaur aft bulkhead. Seen here among two green pressure vessels, one gray Hydrazine tank, batteries, avionic boxes and the RL-10C-1 rocket engine with its bell. A timer opens the lids and coil springs deploys them
Three of the spacecraft are three-unit CubeSats being carried as part of the US Army’s SMDC Nanosatellite Program, or SNaP. The SNaP-3 mission, which consists of spacecraft named Alice, Eddie and Jimi, will be used for communications experiments.
The Aerospace Company’s 1.5-unit AeroCube-5C spacecraft will be used for communications and tracking testing. It follows two previous AeroCube-5 satellites launched in December 2013 as part of the GEMSat mission.
The Optical Communications and Sensor Demonstration A (OCSD-A) satellite, also known as AeroCube 7A, is the first member of a three-satellite constellation that will be used to demonstrate laser communications in orbit.
A pair of two-unit SINOD satellites; SINOD-D1 and D3 were carried on the launch for SRI International. These spacecraft will be used for communications experiments while a pair of single-unit PropCube spacecraft – PropCube 1 and PropCube 3 – will accompany them to take measurements of the ionosphere to assist with calibration.
Of the thirteen CubeSats on NROL-55, NASA has funded the launch of four educational research satellites along with the nine CubeSats from NRO’s GRACE program, under its Educational Launch of Nanosatellites (ELaNa) program.
Designated ELaNa XII, the CubeSat payloads consist of:
Alaska Research CubeSat 1 (ARC-1) for the University of Alaska; BisonSat for Salish Kootenai College on Flathead Reservation, Montana; the Low Mass Radio Science Transponder (LMRST-Sat) for the Jet Propulsion Laboratory and Fox-1A for AMSAT.
LMRST-Sat is a three-unit CubeSat while the other NASA-sponsored CubeSat payloads are all single-unit - 1U - spacecrafts.
ARC-1 will be used to study the conditions the satellite encounters as it ascends towards orbit, in terms of the satellite’s temperature and the vibration encountered. Once in orbit the satellite will test attitude control and communications system, using a camera to image Earth’s ice caps in order to provide data for communications tests.
BisonSat, or Nwist Q̓ʷiq̓ʷáy – meaning “Buffalo Up Above” in Salish, will be used for Earth imaging, land classification and studies of clouds. LMRST-Sat will test a low-mass radio system intended for use on future deep space missions to accomplish science objectives.
Fox-1A is an amateur radio satellite, also carrying a physics research experiment and a gyroscope experiment for Penn State University.
The Atlas V 401 rocket
Thursday’s launch of United Launch Alliance’s Atlas V was flying in the 401 configuration.
The Atlas V, tail number AV-058, 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-058 will use none.
Atlas V 401 split in its major parts. This is a generic non mission specific graphic configuration
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 55 launches with no complete failures.
The Atlas V 401 rocket, tail no. AV-058 is standing 57.32 meters - 188 feet tall on SLC-41.
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.
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 and 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 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.
The Centaur upper stage holds about 48 075 liter - 12 700 gallons of liquid hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit that can fit in a 48,07 m3 hydrogen tank.
The 350 gallon of extra tank capacity found in the LOX tank could be used by Helium gas, Nitrogen gas and Hydrazine pressure vessels. That could be seven 50 gallon tanks.
Still to find is data on Helium gas, Nitrogen gas, pressures levels used and number of tanks - Carbon Overwrapped Pressure Vessels - COPV to store it. And there are tanks to store Hydrazine N2H4 propellant used to maneuver during launch 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 of the Centaur RL-10C-1 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, 8,200 kg to the International Space Station - ISS 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 with a big nozzle - engine bell, so it only produces 101.8 kilonewtons - 22,885.55 pounds in space.
Atlas V 401 weighs an estimated 338,150.7 kilograms - 745,494.7 pounds, including the NROL-55 spacecraft; and is 57.32 meters - 188 feet tall and 4.2 meters - 13,8 feet wide.
The NROL-55 spacecraft weigh 6,218.0 kilograms - 13,708 pounds on their own, that’s with the fairings weight excluded. Weight of 13 CubeSats and dispenser is missing.
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 NROL-55 + 2587 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 meter (40 feet) in length and was first introduced as a larger fairing for the Atlas I rocket that was used as a launch vehicle in 1990.
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.
