Screenshot of NASA/ULA Webcast of the Osiris-REx launch. View from VIF. Top of the World. Mom
Mission Rundown: ULA - Atlas V 411 - Osiris-REx
Written: December 29, 2022
In darkness I will find you
NASA’s OSIRIS-REx spacecraft began a seven-year round trip to the asteroid Bennu on Thursday, beginning its journey via a launch aboard the United Launch Alliance (ULA) Atlas V 411. The Centaur RL-10A-4-2 engine usually flies with two engine bells, but has only one engine bell mounted, so no changes to the Atlas V 411 to a ‘412’ designation.
Liftoff from SLC-41 at the Cape Canaveral Air Force Station was on time, at the start of a 115-minute window that opened at 19:05 local time (23:05 UTC).
The Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer, or OSIRIS-REx, is NASA’s first sample-return mission to an asteroid, and – excluding the Apollo program – its third sample return mission beyond Earth orbit after the Genesis and Stardust probes.
OSIRIS-REx is the third mission of NASA’s New Frontiers program, following the New Horizons spacecraft which flew past Pluto last year and Juno, which arrived in orbit of Jupiter in early July.
The OSIRIS-REx mission is expected to last seven years, culminating with the reentry of the spacecraft’s return capsule in September 2023.
About two and a half years of the mission will be spent at the asteroid (101955) Bennu, from August 2018 to March 2021, with sampling of the asteroid expected to occur in 2020.
Bennu was discovered on 11 September 1999 by scientists at the Lincoln Laboratory’s Near Earth Asteroid Research (LINEAR) program using the Experimental Test Site (ETS) telescope at White Sands, New Mexico. It was provisionally named 1999 RQ36.
An Apollo-class near Earth asteroid orbiting between 134 and 203 million kilometers (83.4 to 126 million miles; 0.897 to 1.36 astronomical units) from the Sun, Bennu has an orbital period of 437 days and a rotation period of 4.29 hours.
The asteroid has a radius of approximately 246 meters (807 feet) and its mass has been estimated at between 60 and 77.6 billion kilograms (59 to 76 million Imperial tons; 66 to 86 million US tons).
Bennu is classified as a B-type asteroid, within the wider C-group of dark-coloured carbonaceous asteroids.
The Osiris-REx Payload
The goals of OSIRIS-REx’s mission are to return a sample of Bennu to Earth for analysis, to conduct a spectral analysis of the asteroid’s surface and characterize its composition, to investigate changes in the asteroid’s orbit due to the absorption and reemission of radiation – a phenomenon known as the Yarkovsky effect – and to study the structure of the asteroid’s regolith.
Osiris REx before integration with the fairing halves. The top cone would have been enough space
The spacecraft was constructed by Lockheed Martin Space Systems.
OSIRIS-REx will be powered by a pair of solar arrays, generating up to three kilowatts of power at perihelion. Unfuelled, the spacecraft has a mass of 880 kilograms (1,940 pounds) and at launch it will weigh 2,110 kg (4,650 lb). The sample return capsule – the only part of the spacecraft designed to return to Earth – has a mass of 46 kilograms (100 lb).
As a sample-return mission, OSIRIS-REx’s primary objective is to collect a sample of Bennu and deliver it to Earth. The Touch-and-Go Sample Acquisition Mechanism, or TAGSAM, will be used to achieve the sampling part of the objective, while a reentry capsule will facilitate its safe return to Earth.
TAGSAM consists of a sampler mounted on an extensible 3.35-meter (11-foot) arm. OSIRIS-REx will maneuver close to the asteroid without landing and deploy the arm to bring the sampler into contact with the surface. This will use a nitrogen jet to loosen surface material for collection. The spacecraft is carrying sufficient nitrogen to attempt this process three times if an insufficient amount of material is initially captured. At least sixty grams (2.1 ounces) of material is expected to be collected.
Once sampling is complete, the sampler head will be stowed within OSIRIS-REx’s return capsule and detached from the arm.
The return capsule will remain attached until OSIRIS-REx makes its final approach to Earth in September 2023, at which point it will separate with the main spacecraft bus subsequently performing a course correction to avoid also entering the atmosphere.
The sample capsule will use an ablative heat shield to protect it as it reenters the atmosphere, descending under a parachute to a landing in Utah. Following landing, the capsule will be taken to the Johnson Space Center’s Astromaterials Acquisition and Curation Office for the study of its contents.
A suite of five instruments aboard OSIRIS-REx will aid in the location of a sample collection site, provide for additional study of the asteroid and give context to the samples returned.
• OSIRIS-REx Camera Suite (OCAMS) – A system consisting of three cameras provided by the University of Arizona, Tucson, will observe Bennu and provide global imaging, sample site imaging, and will witness the sampling event.
• OSIRIS-REx Laser Altimeter (OLA) – A scanning LIDAR (Light Detection and Ranging) contributed by the Canadian Space Agency will be used to measure the distance between the spacecraft and Bennu's surface, and will map the shape of the asteroid.
• OSIRIS-REx Thermal Emission Spectrometer (OTES) – An instrument provided by Arizona State University in Tempe that will investigate mineral abundances and provide temperature information with observations in the thermal infrared spectrum.
• OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) – An instrument provided by NASA’s Goddard Space Flight Center in Greenbelt, Maryland and designed to measure visible and infrared light from Bennu to identify mineral and organic material.
• Regolith X-ray Imaging Spectrometer (REXIS) – A student experiment provided by the Massachusetts Institute of Technology (MIT) and Harvard University in Cambridge, which will observe the X-ray spectrum to identify chemical elements on Bennu’s surface and their abundances.
The OSIRIS-REx flight system is made up of the spacecraft bus (which includes the structure, and all of the various subsystem components to control and operate the vehicle), the TAGSAM (Touch-And-Go Sample Acquisition Mechanism), the SRC (Sample Return Capsule), and the five science instruments.
EPS (Electrical Power Subsystem): The EPS includes two rigid solar arrays, gimballed about the spacecraft Y and Z axes. In addition, two batteries are utilized for off-sun maneuvering, including the critical TAG mission phase.
PPS (Propulsion Subsystem): The high heritage propulsion subsystem is a single fault tolerant monopropellant system of Aerojet Rocketdyne, a subsidiary of Aerojet Rocketdyne Holdings, Inc.
The propulsion subsystem includes main engines, trajectory correction maneuver thrusters, attitude control system thrusters, and low thrust reaction engine assemblies.
The propulsion devices on the spacecraft include four MR-107S 222 N thrusters, six MR-106L 22 N thrusters, 16 MR-111G 4.4 N thrusters and two MR-401 0.44 N thrusters.
Aerojet Rocketdyne propulsion is involved in the mission, including the Earth-departure phase to fine tune the Earth escape velocity; the cruise phase to adjust trajectory and ensure a perfectly accurate trajectory for the Earth swing-by and arrival at Bennu. 8)
GN&C (Guidance, Navigation and Control): The GN&C subsystem includes four RWAs (Reaction Wheel Assemblies) for performing spacecraft slewing and low jitter pointing during science operations. These reaction wheels also store system momentum between desaturation events.
The GN&C subsystem is responsible for commanding all of the thrusters on the spacecraft including executing trajectory correction maneuvers and RWA desaturations. The GN&C subsystem utilizes an IMU (Inertial Measurement Unit) and flight-proven star trackers to determine and propagate on-board attitude knowledge.
Sun sensors additionally support spacecraft autonomous safing operations. Two GN&C sensors provide measurements used for relative navigation: a GN&C lidar is used for ranging to the surface to support TAG operations, a TAG CAMS (TAG Camera System) supports ground based navigation throughout proximity operations and autonomous on-board optical based navigation during the TAG phase.
Atlas V launch preparation timeline
OSIRIS-REx airlifted from Lockheed Martin, Denver to Kennedy Space Center: May 21
Centaur upper stage arrives at Atlas Spaceflight Operations Center CCAFB: July 27
Fairing halves arrives on trucks at Kennedy Space Center, Florida: July 28
First stage booster arrives at Atlas Spaceflight Operations Center: July 29
Atlas first stage booster hoisted vertical: August 8
One AJ-60A solid rocket booster attachment: August 9
Pre-assembled interstage, Centaur, and boattail hoisted into place: August 10
Atlas/Centaur Combined Systems Test: August 15
Atlas/Centaur Roll from Vertical Integration Facility (VIF) to launch pad: August 23
OSIRIS-REx encapsulation in the Payload Hazardous Service Facility: August 24
Atlas/Centaur Wet Dress Rehearsal (WDR): August 24 - Part of the contract with NASA for spacecraft that must launch during planetary launch windows
Atlas/Centaur Roll from launch pad back to VIF: August 25
OSIRIS-REx attachment, hoisted inside payload fairing: August 29
Atlas V Integrated Systems Test: August 31
Atlas V Flight Readiness Review (FRR): September 1
Atlas V Mission Dress Rehearsal: September 2
Atlas V Launch Readiness Review (LRR): September 6
Atlas V Roll from VIF to launch pad: September 7
Atlas V 411 ready to Launch: September 8
The Atlas V 411 Launch
Thursday’s launch began with ignition of the first stage’s RD-180 engine 2.7 seconds in advance of the planned T-0 mark in the countdown. Ignition of the solid rocket motor and liftoff occurred 1.1 seconds after the zero mark.
Ascending from Cape Canaveral’s Space Launch Complex 41 (SLC-41), AV-067 began a series of pitch and yaw maneuvers after 6.7 seconds of flight to establish an 89-degree launch azimuth taking it almost due East over the Atlantic Ocean.
The vehicle reached Mach 1 – the speed of sound – 56.9 seconds after launch before passing through the area of maximum dynamic pressure, or Max-Q, 11.7 seconds later.
The AJ-60A booster is designed to burn for around ninety seconds, after which its thrust tailed off. Its spent casing remained attached until the two-minute, nineteen-second mark when conditions were optimal for its jettison.
The first stage burned for four minutes and 2.8 seconds before shutting down its RD-180 engine, an event designated Booster Engine Cutoff (BECO).
Six seconds after BECO the spent Common Core Booster separated and the Centaur began its pre-start sequence, culminating in ignition – designated Main Engine Start 1 (MES-1) ten seconds after staging.
Centaur’s first burn lasted eight minutes and 3.7 seconds, establishing an initial parking orbit. Following the conclusion of the burn at Main Engine Cutoff 1 (MECO-1) the Centaur coasted for 21 minutes and 25.7 seconds.
After its coast phase concluded, Centaur restarted for a second burn. Lasting six minutes and 50.4 seconds, this burn propelled OSIRIS-REx to Earth escape velocity and into heliocentric orbit.
Spacecraft separation occurred a quarter of an hour after the end of the second burn, at 55 minutes and 38.6 seconds elapsed time, over the Indian Ocean.
Centaur underwent blowdown and safing 26 minutes and 20 seconds after separation, with the Atlas’ mission concluding one hour, 56 minutes and 58.6 seconds after liftoff.
Following launch, OSIRIS-REx will perform a series of maneuvers as it journeys towards the asteroid Bennu. This will include a flyby of Earth which is scheduled to occur on 22 September next year in order to gain a gravity assist.
The spacecraft is currently slated to arrive at Bennu in August 2018, remaining there until March 2021. The sample return capsule is expected to return to Earth on 24 September 2023 while the parent spacecraft will remain in orbit around the Sun.
The Atlas V 411 rocket
OSIRIS-REx began its 111th overall mission on a United Launch Alliance’s launching of the 65th flight of an Atlas V rocket since its 2002 debut.
OSIRIS-REx was launched by AV-067, which was the 4th to fly in Atlas V 411 configuration.
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 Centaur stage makes use of the old double-engine version of RL10A-4-2 providing thrust and burns liquid hydrogen (LH2) and liquid oxygen (LOX).
The single-engine Centaur was introduced with the Atlas III in 2000 as an alternative to the twin-engine configuration the stage had used since the 1960s becoming the standard.
The Atlas RD-180 engine with a single AJ-60A SRB will produce 5,315.4 kiloNewton - 1,199,333 pounds of thrust at liftoff on T0.
Atlas V 411 split in its major parts. Osiris Rex is a spacecraft who doesn’t take up much space
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 lbf of thrust at sea level while the thrust level increases to 933,406.73 lbf in space. With a SRB producing 1,668.4 kiloNewton - 379,600 lbf thrust attached there should be a combined thrust of 5,315.4 kiloNewton - 1,199,333 pounds of thrust.
Adding the two thrust forces gives a higher combined thrust of 5,495.3 kiloNewton - 1,239,921 pounds.
The offset thrust from the single SRB forces the RD-180 main engine to vector its thrust to one side and not straight down. About 140,000 pounds of vertical thrust seems to be lost in this sideways vector thrust pushing.
As a visible result the Atlas V 411 slides sideways already at the launch pad.
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-10A-4-2 engine is optimized for vacuum usage with one nozzle - engine bell, so it only produces 99.1 kilonewtons - 22,300.0 pounds in space.
Atlas V 411 weighs an estimated 334,043 kilograms - 745,494.7 pounds, including the Osiris-REx spacecraft; and is 57.32 meters - 188 feet tall and 4.2 meters - 13,8 feet wide.
The Osiris-REx spacecraft weigh 2,110.0 kilograms - 4,650 pounds on their own, that’s with the fairings weight excluded.
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 + 2110 kg Osiris-REx + 2587 kg = 334042 kg.
The Atlas V 411 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 one SRB attached to the center core.
AJ-60A is a solid fueled booster rocket burning HTPB. It measures 17 meters in length by 1.6 meters in diameter. It weighs 46,697 kg - 102,949 pounds on its own. At lift off it produces 1,668.4 kiloNewton - 379,600 lbf thrust.
The casing is composed of a graphite epoxy composite, and the engine throat and nozzle are made of carbon-phenolic composite. As configured for use on Atlas V, the nozzle is fixed at a 3 degree cant away from the attachment point, but Aerojet offers a variant with thrust vectoring capability.
The Atlas V configuration also features an inward slanting nose cone, but it is available with a conventional nose cone or none at all for use on other rockets.
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, 1 solid rocket boosters, and 1 engine bell on the Centaur Upper Stage.
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