Screenshot from ULA Webcast of the launch of MUOS-4. Schyy. Be quiet. Maybe they won’t see it
Mission Rundown: ULA - Atlas V 551 - MUOS-4
Written: January 9, 2022
We find our Navy in the Sky
United Launch Alliance’s Atlas V rocket completed the US Navy’s Mobile User Objective System (MUOS) constellation Friday, following the launch of the fifth and final first generation satellite from Cape Canaveral.
The launch occurred on September 2, 2015 inside a 44-minute window at 06:18 Eastern Daylight Time (10:18 UTC).
The MUOS-4 Payload
Each MUOS satellite has a mass of approximately 6,740 kilograms (14,900 lb) fully fueled, and is designed for fifteen years of service.
They were built by Lockheed Martin, based around the A2100M bus, with an BT-4 engine from IHI Corporation to provide propulsion for orbit-raising and maneuvering.
The first satellite, MUOS-1, was launched in February 2012 with subsequent launches in July 2013 and January and September 2015.
The satellite aboard Wednesday's launch is the fourth to fly, it is actually SV-05 the fifth produced MUOS satellite. During tests MUOS-3 was found to have defective soldering.
As the satellite SV-3 required repairs, its place on the MUOS-3 mission was taken by the SV-4 vehicle that was next in line to be flown.
It was originally reported that SV-3 has been launched as MUOS-4, however it now appears that the final satellite to be built, SV-5, was used instead for that flight. They were launched in the following order SV-01, 02, 04, 05 and 03.
Although MUOS-4 enters the constellation, a sixth satellite could be funded and possibly be launched between 2018 and 2020. SV-06, if launched, would be with collaboration from international partners in exchange for access to the constellation.
Two satellites of the US Air Force’s Wideband Global Satcom (WGS) programme were funded by similar agreements with allied forces.
The 100-pound-thrust apogee engine on the MUOS-4 is built to carry the satellite from its transfer orbit into its position in its geostationary orbit. That 100-pound-thrust apogee engine is a ‘third’ stage built for this purpose only. In orbit its dead weight.
Ground controllers will use the satellite’s small thrusters for station keeping during its 10-15 year planned mission life.
The spacecraft is equipped with 18 monopropellant hydrazine thrusters designed for attitude control — a dozen 0.2-pound thrusters and six 5-pound thrusters.
MUOS-4 completed orbit raising on September 22, 2015 and successfully deployed its solar arrays for power generation and its antennas for mission operations on Sep. 30.
The satellite will begin on-orbit testing before being turned over to the Navy for the military testing program and final approval and commissioning into service for mission operations was given on November 30, 2015.
With this approval given, 55,000 currently fielded radio terminals with US and allied units on battlegrounds, camp’s, barracks, ships, planes and military vehicles can be upgraded to be MUOS-compatible, with many of them requiring just a software upgrade.
The Atlas V 551 Launch
AV-056’s flight began with ignition of the RD-180 engine, at the minus 2.7-second mark in the countdown. The engine built up thrust, reaching readiness to launch at the zero mark in the countdown.
At T-3 seconds, the Sound Suppression Water System will activate to absorb the shock of the 2.5 million pounds of thrust.
This was followed by ignition of the five solid rocket motors, with the rocket lifting off at 1.1 seconds elapsed time.
NOTAM hazard areas where Atlas V 551 will jettison its five SRB boosters about 250 km, the fairing halves about 1000 km and the core stage close to 3200 kilometer downrange ±100km
With five solids burning the Atlas cleared the pad quickly, before beginning a series of pitch and yaw maneuvers to attain its prescribed trajectory, 3.9 seconds after liftoff. The Atlas flew East from Cape Canaveral over the Atlantic Ocean, along an azimuth - aka. a compass course of 94.58 degrees.
The vehicle encountered the area of maximum dynamic pressure, or max-Q, 49.3 seconds into the mission. It’s marked by a visible white contrail on flights without SRB’s.
The solid rocket motors burned for about ninety seconds after liftoff before tailing off. To ensure a clean separation they were kept attached for a few seconds after burnout, with the first pair separating 108.7 seconds into the flight. The remaining three were jettisoned a second and a half later.
The RD-180 engine continued to power the mission, burning RP-1 propellant oxidized by liquid oxygen, as Atlas climbs towards orbit.
The payload fairing separated from the nose of AV-056 at 207.8 seconds after liftoff.
Five seconds later the Forward Load Reactor, which attaches to the forward end of the Centaur and is used to dampen vibrations within the fairing, was also jettisoned.
First stage flight concluded with a booster engine cutoff, or BECO, four minutes and 25.6 seconds into the mission. The spent Common Core Booster separated six seconds later.
Following stage separation, the Centaur began its pre-start sequence. Its single RL10C-1 engine ignited ten seconds after staging, beginning the first of three planned burns.
This lasted seven minutes and 46.9 seconds, establishing an initial parking orbit.
Seven minutes and 59.2 seconds after the first burn ended, a second burn began lasting five minutes and 46.9 seconds, raising the apogee of the orbit towards geosynchronous altitude.
After the second burn the mission entered a lengthy coast phase, with a third burn occurring two hours, 48 minutes and 40.4 seconds after launch, lasting for 58.3 seconds. This raised the perigee and reduced the inclination of the vehicle’s orbit.
3 minutes and 39 seconds after the end of the third burn, MUOS-4 was deployed.
The target orbit for Wednesday’s launch is 3,819 by 35,784 kilometers (2,373 by 22,235 statute miles; 2,062 by 19,322 nautical miles), at an inclination of 19.11 degrees.
The spacecraft will under its own power achieve its operational geostationary orbit.
The Atlas V 551 rocket
For Wednesday's mission the Atlas V flew in its 551 configuration, which consists of a Common Core Booster (CCB) first stage, a single-engine Centaur upper stage and five Aerojet Rocketdyne AJ-60A solid rocket motors clustered around the first stage.
The vehicle is topped with a five-meter payload fairing which encapsulates both the Centaur and the payload. For MUOS launches the medium-length version of this fairing is used, which is 23.4 meters (76.8 feet) in length. The rocket had tail number AV-056.
Atlas V 551 rocket stands assembled 62.39 meter - 204.7 foot tall with a medium fairing.
Data on another Atlas V 551 rocket standing 196-foot-tall with a small fairing. Weighs 1.3 million pounds. Or more exactly 1278919 pounds equal to 580107.9 kg ~ 580.1 tons.
The Atlas V flew from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station. It can also launch from Space Launch Complex 3E at Vandenberg Air Force Base.
Atlas V 551 split in its major parts. The 5 meter fairing protects the entire Centaur second stage and Payload from the dynamic pressures and temperature increases caused by the air friction
The Atlas V 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 five AJ-60A strap-on solid rocket boosters. The second stage is the Centaur upper stage, which is powered by a RL10C engine with one nozzle that burns liquid hydrogen (LH2) and liquid oxygen (LOX).
The Atlas V propellant volume numbers
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 of 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 Oxygen tank.
The Centaur upper stage holds ca. 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 and Hydrazine pressure vessels. That could be three 100 gallon and one 50 gallon tank.
Still to find is data on Helium gas, pressures levels used and number of tanks - Carbon Overwrapped Pressure Vessels - COPV to store it. And a tank to store Hydrazine N2H4 propellant used to maneuver during launch and in orbit.
The Atlas V weight calculation
In the 551 configuration, the Atlas V is capable of carrying a maximum of 18,500 kg to Low Earth Orbit - LEO, carrying 13,550 kg to Sun Synchronous Orbit - SSO, carrying 8,700 kg to Geostationary Transfer Orbit - GTO and carrying 3,960 kg to Geostationary Orbit - GEO.
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.
Data on an Atlas V in the 401 configuration weighed an estimated 338,149.7 kilograms - 745,492.48 pounds, including the NROL-79 spacecraft; and is 58.23 meters - 191 feet tall and 4.2 meters - 13,8 feet wide.
The MUOS-4 spacecraft weigh 6,740.0 kilograms - 14,900 pounds on its own.
Doing the math: 306272 kg Core Booster + 23073 kg Centaur + 6740 kg MUOS-4.
Using found numbers Atlas V and MUOS-5 without fairings must weigh 336084 kg.
Five AJ-60A solid rocket motors or boosters weigh 233,395 kilo - 514,745 pounds.
Data found on Atlas V 551 rocket that stands 59.7 meter 196-foot-tall with a small fairing. Weighs 1.3 million pounds. Or more exactly 1,278,919 pounds equal to 580,107.9 kg ~ 580.1 tons with 5 AJ-50A SRB’s attached.
Doing the math again: 580108 kg - (336084 kg + 233395 kg = 569479 kg) = 10629 kg.
The boat tail, the short fairing and the two forward reaktor segments must weigh a total of 10,629 kg. Now all that’s missing is to determine the weight of said parts and the weight of the two other fairings on the Atlas V rocket.
The Atlas V 551 fairings
The Atlas V 551 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. This launch will use the 23.45 meter medium fairing (77 ft).
The fairing manufactured by RUAG of Switzerland, comes in three different lengths, with this launch using the shortest of these with a diameter of 5.4 meters (17.7 feet).
The fairing is a Carbon Composite sandwich, made with two layers of Graphite-epoxy face sheets over a middle aluminum honeycomb core. Silver aluminum plates mounted on the inside walls are temperature, sound and vibration dampening pads made of cotton.
The shortest measures 20.70 meters (68 feet) in length, the medium measures 23.45 meters (77 feet) in length and the longest measures 26.49 meters (87 feet) in length but is usually only used on Delta IV Heavy launches.
The four part fairing sections rest structurally on the ‘Boattail’ and extension rings on the Atlas V core booster. The two bottom halves encapsulates the Centaur stage completely and is preventing it from carrying the full load of the payload and fairings. There is a structural maximum of 9,050 kg on the Centaur stage itself during launch.
The two top halves encapsulates the MUOS-4 payload and stands on the Centaur upper stage that is reinforced by two forward reaktor load segments. They act as a floor that keeps Hydrogen gas from seeping into the top fairing compartment, and stops the fairings from wobbling and buckling during maximum aerodynamic pressure loads.
The Centaur bottom fairing half is filled with venting holes to allow the Hydrogen gas to escape during propellant loading. This is seen in photos of the 5 meter fairing.
The ‘Bullitt’ or top fairing payload compartment is air conditioned with dry NOx gasses using a mix of pure Nitrogen and Oxygen gas under pressure to prevent water vapors and hydrogen gas from entering the payload compartment.
Deep Sea divers use NOx gas mixtures to prevent getting the ‘bends’, it’s nitrogen bubbles in their blood and they also mix in Helium gas on long duration deep sea dives.
Reaching space the fairing separation splits the two fairing halves lengthwise, and a few seconds later the forward reaktor segments are jettisoned as well.
The halves now fall in a ballistic curve back to Earth to be incinerated as shooting stars and the remains will sink beneath the Ocean waves some 1000-1600 kilometers down range depending on when and where the fairings were released.
Solid Rocket Boosters - SRB
The second number denotes the number of solid rocket boosters (SRBs), which attach to the base of the rocket. The number of SRB’s for a 5 meter fairing can range from 0 – 5. In this case there will be five AJ-60A SRB’s attached to the center core.
It’s unique to the Atlas rocket to have their solid rocket boosters (SRBs) positioned in this way. When, like in this case, five SRB’s are used, they are positioned with two on one side and three directly opposite of them.
If you notice carefully in the image of Atlas core boosters, there are long and somewhat flat pipes “running” down the side of the first core stage. These are raceways and carry fuel from the tanks down to the engines and some carry gasses back up to the tanks to pressurize them so the fuel stays flowing out the pipes.
When Atlas was designed, these two raceways were placed in their positions without the thought of SRB placement. So when more SRBs were needed, they were placed in the most convenient spot. Two SRB between the raceways and three opposite them.
The offset of the thrust won’t make it fly in the wrong direction. The engines on the core stage can gimbal, they counteract that offset of thrust by vectoring their thrust which is known as thrust vector control, or TVC. The SRBs, and most of them for that matter, do not have TVC abilities, but their nozzles can be angled and turned slightly sideways. That will counteract some of that offset SRB thrust.
A single attached SRB produces 1,668.4 kiloNewton - 379,600 lbf of thrust then five SRB’s must produce 8,342.0 kiloNewton - 1,898,000.0 lbf of thrust.
The AJ-60A solid rocket motor or booster weighs 46,679 kilo - 102,949 pounds. Measures 17 meter - 669 inches in height and 1.6 meter - 62 inches in diameter.
Five AJ-60A solid rocket motors or boosters weigh 233,395 kilo - 514,745 pounds.
The Centaur upper stage
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, 5 solid rocket boosters, and 1 engine bell on the Centaur Upper Stage that is more than 12 m long, 3.05 m in diameter, with an empty mass of 2,100 kg.
The RL-10C-1 engine is optimized for vacuum usage with a big nozzle - engine bell, it produces 101.8 kilonewtons - 22,885.55 pounds of thrust in space.
The aft RL-10C-1 engine section of the Centaur upper stage seen here in a graphic format
This technical image of the aft bulkhead with the RL-10C-1 vacuum engine depicts two green pressure vessels and a gray composite wrapped Hydrazine propellant tank used to feed the Reaction Control System.
Monopropellant hydrazine N2H4 feeds the 9-pound thrusters designed for attitude control and keeping the propellant tanks under a small constant g force.
The hydrazine N2H4 tank of an Atlas V Centaur upper stage rocket, which is produced by ATK as a model 80427-1 pressure vessel. ATK described it as a 59 cm diameter, 86 cm long pressure vessel, constructed of annealed 6AL-4V Titanium and T-1000G graphite hoop wrap, and two spun domes.
Its empty mass is 19 kg; minimum wall thickness is 1 mm; propellant capacity is 153 kg.
The two green pressure vessels with Helium gas are either used to backfill the propellant tanks to prevent structural buckling or to spin a propellant pump up before engine ignition. The Helium gas could also pressurize the Oxygen tank to force a 10 second Oxygen rich startup sequence before hydrogen and spark plugs are applied.
A third pressure vessel with Helium gas is placed inside one of the propellant tanks. All propellant tanks have one pressure vessel with Helium gas inside
Centaur is equipped with Ullage thrusters fed with boiled off Hydrogen and Oxygen gas that constantly needs to be burned off to prevent the propellant tanks from overpressuring and rupturing during space flight.
The Ullage thrusters help with keeping the propellant tanks under a constant g force thus settling the liquid propellant Hydrogen and Oxygen ai the intake valves ready to use.
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 double-thruster pods and four quadruple thruster pods.
For propellant, 150 kg (340 lb) of Hydrazine is stored in a tank and fed to the RCS engines. The propellant tanks are backfilled with pressurized helium gas, which is also used to accomplish some of the Centaur RL-10C-1 engine start up functions.
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