Screenshot from ULA Webcast of the NROL-67 launch.
Mission Rundown: ULA - Atlas V 541 - NROL-67
Written: January 29, 2023
What’s in the new box from NRO?
The United Launch Alliance (ULA) has launched an Atlas V 541, tasked with deploying a payload directly to geostationary orbit for the National Reconnaissance Office.
NRO Launch 67 - NROL-67, lifted off on Thursday April 10, 2014 from Cape Canaveral’s Space Launch Complex -41 (SLC-41) on schedule at 13:45 EDT local time - 17:45 UTC.
NOTAM on rocket debris crash sites for rocket failure, 4 SRB’s, 2 fairings and the core booster
The NROL-67 payload
The mission of the NROL-67 payload is classified. While this has never stopped observers identifying most NRO spacecraft ahead of their launch, this marks the first use by the NRO of an Atlas V 541 rocket, indicating that it is likely a new class of payload.
Like kids trying to find Uncle Sam’s Christmas present, shaking them and trying to guess what's in them, satellite observers world wide look for clues to what it could be. This NRO spacecraft is much harder to identify as there are no similar launches to compare it to.
Atlas V 541 rocket can lift a maximum of 3730 kg directly to geostationary orbit. With that information you can deduce that there is no apogee engine or propellant tanks onboard the NRO spacecraft. Therefore it’s a lighter satellite but otherwise similar to existing NRO satellites placed in geostationary orbit. All it needs is station keeping capabilities and a mission-dependent instrument package to carry out said mission.
So what existing NRO spacecraft would weigh less than 3730 kg? without its apogee engine or propellant tanks? and with a smaller less bulky satellite bus+ and be carrying its new and improved mission dependent instrument package? Riddle me this instead.
Notices to airmen (NOTAMS) and hazard areas published ahead of the launch show that the rocket will launch to the East, over the Atlantic Ocean, to a low-inclination orbit. Such a trajectory means that the payload is almost certainly bound for a geosynchronous orbit, since other equatorial regimes are of little value for reconnaissance.
The NRO has had two or three principal constellations of spacecraft in geosynchronous orbit, each fulfilling different purposes. The Quasar or Satellite Data System (SDS) spacecraft are used to provide communications between lower-orbit reconnaissance satellites and ground stations. Quasar launches during the EELV era have made use of Atlas V 401 and Delta IV Medium+(4,2) rockets.
The use of the more powerful Atlas V 541 for NROL-67 means that this payload is unlikely to be related to the Satellite Data System; however it is still possible that it could be a newer and larger satellite, two spacecraft launching together, or a satellite being placed directly into geostationary orbit rather than the usual transfer orbit.
The remainder of the NRO’s geostationary fleet is used for signals intelligence (SIGINT) of one form or another. Orion satellites, formerly known as Magnum, are believed to be used to intercept and eavesdrop upon communications while the Mercury series pinpoints radar signals, although some reports reverse the assumed missions of these two series.
Another suggestion has been that the Mercury series is used to collect communication data while Orion intercepts telemetry data from foreign weapon systems aka. missiles.
The true nature of NROL-67 will be difficult to ascertain until the satellite has been sighted in orbit and observed over a period of several months. A team of amateur observers keep track of classified satellites, posting data on their locations and orbits online.
The most likely explanation is that it’s a long-overdue replacement for the older Mercury satellites, however this still leaves many questions unanswered.
All NRO can do is watch, listen, wait and finally act, when the enemy makes his move.
The Atlas V 541 launch
Thursday’s launch took place from Space Launch Complex 41 at the Cape Canaveral Air Force Station, a former Titan launch pad which is the east coast home of the Atlas V.
AV-045’s flight plan was not announced. Events in the early stages were deemed to be similar to the Mars Science Laboratory launch, with RD-180 ignition occurring at T-2.7 seconds, with the solids joining them at T-0. Around eleven tenths of a second later the Atlas lifted off to begin its ascent.
Roll, pitch and yaw maneuvers began at around T+5.2 seconds to attain the necessary attitude to achieve its target orbit, however the early flight was close to vertical as AV-045 climbed out of the atmosphere to reach an altitude at which fairing separation can occur.
The solid motors burned for around 85 to 90 seconds before they separated in pairs around 27 seconds later.
Fairing separation came around the three and a half minute mark, with the forward load reactor being jettisoned from the nose of the Centaur shortly afterwards. The load reactor is a device used to dampen vibrations from the fairing while it is attached, preventing, with the fairings, acoustic vibrations and air friction heat from damaging the satellite.
The first stage is expected to have burned out around approximately four minutes and 20 seconds after liftoff, with the last 20 seconds of the flight being made at partial thrust as the RD-180 is throttled back to limit structural loads due to acceleration.
The spent CCB is expected to have separated six seconds after cutoff, with the Centaur’s RL10 engine igniting ten seconds later.
The Centaur then made two or three burns depending on the flight profile. Assuming NROL-67 goes to geosynchronous orbit, the Atlas may place it there directly, or instead the satellite might enter a transfer orbit and raise itself to the final orbit under its own power.
Direct insertion into geostationary orbit has been favored for past NRO SIGINT launches, and is also used on some of Russia’s Proton launches. The majority of geosynchronous launches by contrast use a transfer orbit, and this approach has been used for the NRO’s Quasar satellites in the past.
Direct insertion into geostationary orbit would require a three-burn profile, while a transfer orbit could be reached in two or three burns depending on mission requirements.
A typical ascent to a transfer orbit would use two burns; the first burn, which would be significantly longer than the second, would place the spacecraft into an elliptical parking orbit, with the Centaur then restarting to increase the apogee to geostationary altitude or above. On some missions an extended coast phase may be inserted between the burns to allow a higher perigee to be achieved.
Alternatively, a third burn could have been made separately to raise the perigee during the coast towards apogee. A direct launch into geostationary orbit would work in much the same way, except for the third burn being made five hours after launch to circularize the orbit at apogee. In order to achieve this the Centaur must carry an extended mission kit.
For a typical mission to place a satellite directly into geostationary orbit, the Centaur would make an initial burn lasting around eight and a half minutes. After coasting for nine and a half minutes, the stage would restart for about 265 seconds into the transfer orbit.
The Centaur would then begin rolling to maintain thermal control during its extended coast phase. After five hours and seven and a half minutes of coast, the RL10 would restart for a further two minutes to place the payload into its target orbit with spacecraft separation occurring about two and a half minutes later.
ULA confirmed a successful spacecraft separation later on Thursday.
The Atlas V 541 rocket
The Atlas V used for the NROL-67 mission was AV-045. The forty-sixth Atlas V to fly, it was the second to use the 541 configuration which made use of a payload fairing with a diameter of five meters, four solid rocket motors and a Centaur upper stage with a single engine.
This configuration has flown just once before; sending the Curiosity rover on its way to Mars in November 2011.
The first stage of the Atlas is a Common Core Booster, powered by a single RD-180 engine derived from the RD-170 series made in the Soviet Union for the Zenit and Energia rockets.
The twin-chamber RD-180 is fueled by RP-1 propellant and liquid oxygen. Four of a maximum five Aerojet Solid Rocket Motors (SRMs) were used to augment the CCB’s thrust at liftoff on Thursday’s mission.
The second stage, the Centaur, is powered by an RL10A-4-2 engine burning liquid hydrogen and liquid oxygen. During the early stages of flight it was encapsulated, along with the payload, inside the fairing.
AV-045 sported the short variant of the five-meter fairing, measuring 20.7 meters (67.9 feet) in length and 5.4 meters (17.7 feet) in diameter.
Atlas V configurations with more than three solid rocket motors require the use of a five meter fairing, as opposed to the four meter fairing which leaves the Centaur exposed, as the upper stage would not structurally be able to withstand the excessive thrust to weight or gravity - ‘g’ loads imparted by the additional boosters.
Atlas V 541 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
Atlas V 541 rocket stands assembled 59.70 meter - 196 feet tall with a small 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. We just need to subtract the weight and the thrust of one AJ-60A SRB.
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.
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 kerosene 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 Ammonia Hydrazine and Helium pressure vessels. That could be in three 100 gallon tanks and two spheric 25 gallon ball tanks.
Still to find is precise data on Helium gas, pressures levels used in them and number of tanks - Carbon Overwrapped Pressure Vessels - COPV to store it. Tanks to store Hydrazine N2H4 and Ammonia propellant used to maneuver during launch and in orbit.
The Atlas V weight calculation
In the 541 configuration, the Atlas V rocket can carry a maximum mass of:
17100 kg to Low Earth Orbit - LEO - heading directly east from SLC-41
12435 kg to Sun Synchronous Orbit - SSO - heading prograde about 98o south
8240 kg to Geostationary Transfer Orbit - GTO - doing a transfer burn at equator
3730 kg to Geostationary Orbit - GEO - doing a third circularization burn at apogee
Facts on the Atlas V 541 launch vehicle - Calculated with 4 SRB’s + NROL-67
Height of Atlas V 541: 59.70 meter - 196 feet
Mass at liftoff: 530 990.9 kilogram - 1 170 635 pounds
Thrust at liftoff: 10.5 meganewtons - 2.38 million lbf
Fuel onboard: 91,000 gallons of liquid propellant
LOX+LH2 = 66,000 gallon of cryogenic liquid propellant in three tanks
Core stage Atlas: 25,000 gallon RP-1 or 94,64 m3 - 48,800 gallon LOX or 184,73 m3
Core stage weighs fully fueled 306,271.7 kilograms - 675,213.5 pounds
Core stage propellant weighs 248,089.7 kilograms - 626,309.5 pounds
Core stage measures 35.63 meters - 116,9 feet tall x 3.81 meters - 12,5 feet wide
Core stage RD-180 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
Upper Stage Centaur: 13,050 gallon LH2 or 48,07 m3 - 4,150 gallon LOX or 15,71 m3
Upper Stage Centaur weighs fully fueled 23,073 kilograms - 50,867.3 pounds
Upper Stage Centaur propellant weighs 20,830 kilograms - 45,922.3 pounds
Upper Stage Centaur measures 12.68 meters - 41,6 feet tall - 3.05 meters - 10 feet wide
RL-10A-4-2 engine is optimized for vacuum usage with a big nozzle - engine bell, so it only produces 99.1 kilonewtons - 22,300 pounds in space
Centaur has 150 kg (340 lb) of Hydrazine + Ammonia is stored in two diaphragm tanks
Centaur has 2-3 Helium 100-150 gallon pressure vessel storage tanks
The AJ-60A SRB stands 17 meter - 55’9’’ feet in height x 1.6 meter - 5’2’’ feet in diameter
The AJ-60A solid rocket motor or booster weighs 46,679 kilo - 102,949 pounds.
Four AJ-60A solid rocket motors or boosters weigh 186,716 kilo - 410,775 pounds.
The AJ-60A SRB produce 1,668.4 kilonewton - 379,600 lbf of thrust
Four AJ-60A SRB produces 6,673.6 kilonewton - 1,518,400 lbf of thrust
NROL-67 payload weighs 3 730 kg ~ 8 223 pounds - Maximum for a GEO mission
Fairing parts weighs 11 200 kg ~ 24 692 pounds - Calculated mass from AEHF-6 data
Data found on Atlas V 551 rocket. It 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 ton with five AJ-60A SRB’s attached and carrying the AEHF-6 satellite.
Five AJ-60A solid rocket motors or boosters weigh 233,395 kilo - 514,745 pounds.
The AEHF-6 spacecraft weigh 6,168.0 kilograms - 13,598 pounds on its own
Doing the math: 306272 kg Core Booster + 23073 kg Centaur + 6168 kg AEHF-6
Using found numbers Atlas V and AEHF-6 without fairings must weigh: 335513 kg
Doing the math again: 580108 kg total - 335513 kg rocket - 233395 kg SRB’s = 11200 kg of interstage parts including the boat tail, the short fairing, the two forward reaktor segments and the payload adaptor fitting used to hold and release the AEHF-6 satellite.
They must weigh a total of 11,200 kg. Now all that’s missing is to determine the weight of said parts and the weight of the two longer fairing types 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 NROL-67 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 four 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, four SRB’s are used, they are positioned with two on one side and two more 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. Two SRBs do not have TVC abilities, but their fixed nozzles can be angled and turned slightly sideways. That will counteract some of that offset thrust from the SRB’s.
A single attached SRB produces 1,668.4 kilonewton - 379,600 lbf of thrust then four SRB’s must produce 6,673.6 kilonewton - 1,518,400 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
Four AJ-60A solid rocket motors or boosters weigh 186,716 kilo - 410,775 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, 4 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-10A-4-2 engine is optimized for vacuum usage with a big nozzle - engine bell, it produces 99.1 kilonewtons - 22,300 pounds of thrust in space.
The Centaur 2nd stage with a RL-10A-4-2 engine is hanging here in the Vertical Integration Facility
This photo of the Centaur with the RL-10A-4-2 vacuum engine depicts two insulated green pressure vessels - one behind the engine - a white insulated Ammonia sphere tank and a blue insulated Hydrazine sphere tank with propellant used to feed the thrusters in the Attitude/Reaction Control System - ACS/RCS.
The propellant is visibly divided in a large Hydrogen tank forward and a smaller Oxygen tank below it supporting the engine mount. The RL-10A-4-2 vacuum engine's red nozzle will get a longer gray nozzle cone extension mounted.
Monopropellant hydrazine N2H4 feeds the thrusters designed for attitude control and keeping the propellant tanks under a small constant g force.
A recovered crashed hydrazine 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 believed 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 over pressuring 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 gas pressure thrust from the tanks and consists of twenty hydrazine monopropellant engines located around the stage in two 27 newton twin-thruster pods and four 40 newton quad-thruster pods.
For propellant, 150 kg (340 lb) of Hydrazine and Ammonia is stored in a pair of diaphragm tanks ‘White and Blue’ and fed to the RCS engines aided by pressurized helium gas, which is also used to perform some of the Centaur RL-10A-4-2 engine start up functions.
