Space Launch Report:   Antares (Taurus II)
Home    On the Pad     Space Logs     Library    Links

Antares-a1-1.jpg (34375 bytes)Antares (Taurus II)
(By Ed Kyle, Updated 06/12/2018)

Vehicle Configurations

Vehicle Components

Antares Launch History

First Antares Flight Vehicle is Loaded onto its Transporter/Erector in Wallops Island Horizontal Integration Facility on April 4, 2013

Orbital (OSC) began in-house design of a new medium-class launch vehicle, originally named "Taurus II" but now known as "Antares", in 2007.  In early December 2007, Orbital provided an initial glimpse of its plans.  The company said that Taurus II would, carry Delta II-class payloads by combining elements of Orbital's existing Pegasus, Taurus, and Minotaur launchers with "hardware from one of the world’s leading launch vehicle integrators".   In its October 18, 2007 report of third quarter earnings, the company disclosed that such a development, tenatively named "Taurus II" (or "Taurus 2"), could cost $40-45 million in 2008, but could also increase corporate revenue by as much as $25 million.  

On February 19, 2008, NASA awarded a Commercial Orbital Transportation Services (COTS) Demonstration Mission to Orbital.   The $170 million project award, recompeted after NASA cancelled RocketPlane Kistler's original COTS award, was expected to be combined with $150 million of Orbital's own money to develop Taurus II and a new "maneuvering spacecraft" named "Cygnus".

Taurus II and Cygnus would be developed to perform a demonstration of commercial cargo delivery to the International Space Station (ISS).  Cygnus would carry up to 2.3 tonnes of pressurized and unpressurized cargo on speciallized interchangeable modules.  A reentry version would be able to return as much as 1.2 tonnes of cargo from ISS to Earth.

taurus2.jpg (OSC)cygnus.jpg (OSC)Artist Depictions of Antares (Left) and Cygnus (Right)

Orbital’s COTS demonstration mission was initially planned to occur before the end of 2010, but subsequently slipped into 2011. The company planned to develop a system capable of conducting as many as eight ISS cargo flights per year by 2012-13.  Cygnus, based on Orbital's satellite design skills, would be developed and assembled in Dulles, Virginia and Greenbelt, Maryland.  Taurus II would be assembled and tested in Ukraine, in Dulles, and in Chandler, Arizona.  Taurus II, initially slated to fly from rebuilt Launch Area 0-A at Wallops Island, Virginia, would be able to lift 3.7 to 5.4 tonnes to low earth orbit, depending on launch site, orbit altitude, and orbit inclination.   

On December 23, 2008, NASA awarded a $1.9 billion Commercial Resupply Services (CRS) contract to Orbital, purchasing eight ISS resupply missions to be launched by Taurus II/Cygnus from Wallops Island.  The first mission was slated for October 2011.  The contract extended through the end of 2016. 

Orbital planned for Taurus II to be profitable at relatively low flight rates.  The company expected to perform no more than five or six Taurus II flights per year by 2015.   

t2drwgs.jpg (5622 bytes)t2origin.jpg (7866 bytes)Vehicle Description

Antares is a Ukrainian/Russian/American Rocket - Perhaps the World's Most International Launch Vehicle.  It will Orbit an Italian/American Spacecraft to an International Space Station..

Yuzhnoe/Yuzhmash of Ukraine will develop and build Taurus II's 3.9 meter diameter first stage.  The stage will use kerosene and liquid oxygen tanks with the same diameter as Zenit 2/3, which is also made by Yuzhnoe/Yuzhmash.  Twin Kuznetsov NK33 engines, modified by Aerojet and cataloged as "AJ26-62" engines, will power the Taurus II first stage.

During the 1990s, Aerojet acquired rights to import about 46 of the engines from ND Kuznetsov Joint Stock Company Scientific-Technical Complex of Samara Russia.  The engines were originally developed for the Soviet Union's N1 launch vehicle.  More than 50 more NK33s are reported to remain in storage in Samara.  Aerojet negotiated a license to produce new copies in the U.S., but such production would require several years to initiate. 

In 2008, Orbital reported that it had rights to 36 NK33 engines and that it planned to purchase 30 more, providing a total of 33 flight sets.

Each staged combustion cycle kerosene/liquid oxygen NK33 develops nearly 153 tonnes of sea level thrust and 167 tonnes in vacuum at 100% throttle, but the engines will be throttled up to 108% for Taurus 2.  The engines are highly efficient, with specific impulse ratings of 297 seconds at sea level and 331 seconds in vacuum.  

The first stage will carry 240 tonnes or more of propellant, weigh 18.75 tonnes empty, and stand roughly 28 meters tall.  The high thrust provided by two NK33 engines means that Taurus II will not need strap-on boosters to match Delta II performance, but such boosters could presumably be added to increase performance in the future. 

c30tst.jpg (11861 bytes)Castor 30 Test

Taurus II will use a new "Castor 30" solid fuel second stage motor produced by ATK.  Castor 30, a derivative of the longer Castor 120 motor, will weigh about 14 tonnes loaded, will burn for 155 seconds, and will produce about 26.4 tonnes of average thrust.  Orbital will add a cold-gas three-axis attitude control system to the Castor 30 to create a stage that can coast and maneuver.   Guidance and control of the stage and vehicle will be provided by an Avionics Module mounted atop the stage.  

Orbital's Taurus II fact sheet was updated in May 2009 to show a follow-on "enhanced" second stage option.  The stage would be powered by a new Pratt & Whitney Rocketdyne PWR35M engine that would burn LOX and Methane to produce 35,000 lb (15.88 tonne) class thrust.  With this stage, Taurus II could move beyond Delta II payload capability, hauling up to 7.6 tonnes to low earth orbit or 1.8 tonnes to Earth escape velocity when topped with a Star 48 third stage. 

In early 2010, the "enhanced" stage design shifted toward kerosene/LOX, potentially to be powered by the Russian RD-0120 staged combustion engine used by Soyuz 2.1b.

In January 2009, Applied Aerospace Structures Corporation of Stockton, California announced that it would build composite structures for Taurus II, including the payload fairing, fairing adapter, interstage, Stage 2 motor adapter, payload fairing adapter, and avionics cylinder.  Deliveries were expected to begin in late 2009.  

A maneuvering bipropellant hypergolic third stage could eventually see use with Taurus II, though it would not be used for COTS demo missions.   The stage, equipped with a bipropellant hypergolic pressure-fed propulsion system similar to equipment used by Orbital's Star2bus satellites, has been called an Orbit Raising Kit (ORK).  The ORK could provide orbit raising maneuvers for higher-altitude missions.       

For higher energy missions, Taurus II could use a Star 48V solid propellant kick motor.  A Star 48V on top of a Taurus II would be able to boost more than 1.1 tonnes to Earth escape velocity.     

Orbital has examined Taurus II designs before.   A Taurus II design studied during the early 1990s used two Castor 120 motors stacked in series topped by a new bi-propellant liquid stage.  As many as eight Castor IVA strap-on boosters augmented the core stage.  The most powerful variant would have matched Delta II capability.

Taurus II will stand roughly 40.5 meters tall, assuming a 9-10 meter long payload fairing.  The 2.34 meter diameter Castor 30 second stage would fit within a 3.9 meter diameter, 4-5 meter tall "interstage" section.

nk33tst.jpg (41624 bytes)Development Progress

NK-33 Testing in Samara

During 2009, construction of Taurus II facilities began at Wallops Island.  The old Conestoga service tower at Pad 0-A was demolished to make way for a brand new Taurus II pad.  Construction of a Horizontal Integration Facility also began.  Taurus II will be horizontally integrated with a mated payload in the HIF.  A wheeled transporter/erector will roll out and erect the rocket on its launch pad about 24 hours prior to launch.  

In December 2009, ATK tested its Castor 30 motor in a high altitude chamber at the Arnold Engineering Test Center in Tennessee.  The stage performed a 150 second burn, producing a peak 32.66 tonnes of thrust.

Russia's SNTK initiated extended-duration "margin" testing of an NK-33 engine at the Vintay test range in Russia's Samara region beginning in the Fall of 2009.  A successful 220 second test on October 1 was followed by an aborted test five days later.  The abort, which created a fire on the stand, occurred 160 seconds into the test when pulsations began in a test stand oxidizer feed line.    Testing resumed in early 2010.  In early March, an NK-33 performed three test runs for a cumulative 600 seconds, including runs twice as long as the planned 235 second Taurus II burn.

aj26-1.jpg (24128 bytes)AJ26-62 Pathfinder at Stennis

A pathfinder AJ26-62 engine was shipped to NASA's Stennis Space Center Test Stand E-1 on February 23, 2010 for configuration verification testing, to verify changes made by Aerojet to the original NK-33 engine and to measure engine performance in its flight set-up.  The engine performed an initial 10 second "readiness firing" on November 11, 2010.   A second, 55-second hot-fire acceptance test took place on December 16, 2010.  A third hot-fire test for engine control valve tuning was subsequently canceled after crews determined it was not needed. 

The "E1" engine was removed from the Stennis E-1 stand in January 2011.  Engine "E2" immediately took its place.   E2 completed a 54 second acceptance firing on February 7, 2011.  Afterward, the engine was shipped to Wallops Island for integration with the first Taurus 2 first stage.

Meanwhile, construction was underway at Wallops Island Pad 0A, where an entirely new elevated pad structure was being erected to replace the old Conestoga pad.  A new Horizontal Integration Facility was also rising on the island.  

In Ukraine, Yuzhnoe/Yuzhmash completed the pathfinder Taurus 2 first stage on October 8, 2010.  The stage underwent acceptance testing in Ukraine prior to being shipped to Wallops Flight Facility, where it arrived in December, 2010.  The stage was said to weigh 13.154 tonnes dry (probably without engines installed), extend 27.44 meters in length, and have a 3.9 meter diameter.

The next first stage was delivered to Wallops during April 2011.  "Vehicle No. 1" was to be used for static testing on the launch pad while "Vehicle No. 2" was to perform the first Risk Reduction Flight.   After its static testing, "Vehicle No. 1" was to be refurbished for use on a later mission. 

On March 22, 2011, the Horizontal Integration Facility at Wallops was dedicated.  Pad 0A was nearing completion by that date. 

In early April, 2011, NASA announced that it would fund a Taurus 2 Risk Reduction Flight.  The test flight, to be performed without a live Cygnus spacecraft payload, would occur no earlier than October 2011.  Prior to the launch, Orbital would use the pathfinder stage to test launch site equipment in an effort culminating in a static test firing on the new pad. 

taurus2ehs.jpg (10592 bytes)Taurus IIe

On April 25, 2011, Orbital announced that it had directed ATK to develop a more powerful upper stage named "Castor 30XL".   The $57 million effort would lengthen the "Castor 30A" stage, used for the first two Taurus 2 flights, by about 40% and likely increase propellant loading by nearly 80%.   An upgraded "Castor 30B", equipped with an extended nozzle,   would power Flights Two and Three before Castor 30XL would enter service on Flight Five, creating a new "Taurus IIe" model. 

It was not immediately clear if the decision halted, or merely shelved, plans for the previously discussed "enhanced" liquid upper stage. 

Taurus IIe would, according to the annoucement, be able to lift 6 tonnes to LEO from Wallops, bettering Delta II performance and nearly matching Delta II Heavy results.   It would boost 4.2 tonnes to a 600 km polar orbit if launched from Vandenberg AFB or from Kodiak in Alaska.  Taurus IIe would fly beginning in 2013. 

Adding a Star 48BV third stage, also made by ATK, atop a Castor 30XL would create a "Taurus IIh".  This three-stage rocket would be able to boost 1.1 tonnes to Earth escape velocity from Wallops.  Taurus IIh would be available in 2014.

30xlfirst.jpg (10661 bytes)First Castor 30XL Test Firing

Castor 30XL was successfully test fired for the first time on March 28, 2013 at the U.S. Air Force's Arnold Engineering Development Complex (AEDC) in Tennessee.

Orbital planned to establish a new Taurus II west coast launch site that would be ready in 2014.  Vandenberg and Kodiak were both under consideration.

AJ-26 Testing

After successfully testing the first three AJ-26 engines, the program suffered a setback when a fourth engine suffered a failure during a June 9, 2011 static test at Stennis Space Center's E-1 test stand.  The engine caught fire during the aborted test because of a kerosene fuel leak from an engine manifold.  The root cause was subsequently determined to be stress corrosion cracking of the 40-year old metal.  The fire damaged the engine to such an extent that it had to be replaced with another engine in the delivery plan, although the engine was deemed repairable if ultimately necessary.  The replacement engine was successfully hot-fire tested on September 28, 2011 after improved inspection protocols had been implemented.  Another engine was tested in mid-November, 2011. 

ant-v1v2s.jpg (15159 bytes)First AJ-26 Engine Set Installed on Vehicle No. 1 at Wallops

In mid-November, the first complete AJ-26 propulsion system was mated to Vehicle No. 1 at the Wallops Island HIF.  By that time, both a live Castor 30 second stage motor and a Cygnus payload simulator had been delivered to the facility.   


On December 12, 2011, Orbital Sciences Corporation announced that Taurus II would be renamed "Antares".  The name was announced prior to the beginning of what the company called the "operational phase" of the program, with three launches then planned to occur in 2012.

Orbital stuck with its tradition of using "Greek-derived celestial names" for its rockets.  Antares, among of the brightest stars in the sky, is in the constellation Scorpius. 

At the time of the name change, Antares had a 10 launch backlog, including an initial test launch in 2012 followed by a demonstration mission later in the year.  Both flights were to be performed under the Commercial Orbital Transportation Services (COTS) agreement with NASA - a program intended to develop a cargo transportation system for the International Space Station (ISS).  Antares would also be used for eight subsequent contracted Commercial Resupply Services (CRS) missions.   The latter missions were part of a $1.9 billion agreement to deliver cargo to the ISS from 2012 through 2015.

t2path.jpg (32241 bytes)Hot Fire

First Antares Vehicle Stage, Used for February 2013 Hot Fire Test at Wallops

Launch site delays pushed the schedule back.  An Antares first stage, serving as a pathfinder, was rolled out to the pad during April 2012, but only for mechanical fit checks. The stage was returned to the pad in October, 2012 for cold flow testing.  Those tests, involving propellant loading, were not completed until January 2013, a process that was delayed by the passage of Hurricane Sandy.

On February 22, 2013, Orbital Sciences successfully performed a hot fire test of the pathfinder Antares first stage at Wallops Island.   The test, performed at launch Pad 0A, began at 23:00 UTC and lasted for 23 seconds, during which time the AJ26 engine pair generated about 308 tonnes of thrust.  It was the first time that an integrated test of two AJ26 engines and the first stage had been performed.

antares-a1-2.jpg (26421 bytes)Inaugural Antares Reaches Orbit

Second Antares First Stage Rolled Out with First "A-ONE" Flight Vehicle on April 6, 2013.

The first Antares flight vehicle, consisting of the second first stage to be delivered and the first Castor 30 stage, rolled out to Wallops Island Pad 0A on April 6, 2013.  The vehicle included a dummy Cygnus spacecraft.  The A-ONE test flight was planned to take place in mid-April 2013 as a ten minute test flight slated to boost the second stage and payload simulator into a 250 x 300 km x 51.6 deg orbit. 

wi0a.jpg (28794 bytes)A-ONE Antares Stands on Wallops Island Pad 0A a Few Days Before Launch

After nearly two years delay from original plans, Orbital Science's Antares launch vehicle  succeeded on its first, "COTS Risk Reduction" flight.  Antares A-ONE boosted its 3.8 tonne simulated Cygnus payload to orbit from Wallops Island, Virginia on April 21, 2013.  At about 277.45 tonnes gross liftoff weight, it was the largest rocket ever to fly from Wallops.

The Ukrainian/Russian/American built rocket rose from Pad 0A at 21:00 UTC on 332.94 tonnes of thrust produced by its two Aerojet AJ-26 (rebuilt Russian NK-33 engines dating from the 1970s) LOX/RP1 engines.  The engines burned for 230 seconds before shutting down.  Separation of the Ukrainian built first stage occurred five seconds later. 

aone2.jpg (9817 bytes)Antares A-ONE Rises from Pad 0A

The ATK Castor 30A powered second stage coasted for about 93 seconds before igniting.  During the coast, the payload fairing separated at 320 seconds, followed within ten seconds by separation of the 3.9 meter diameter interstage.  Second stage ignition occurred at T+328 seconds, beginning a 155 second burn that boosted the vehicle to a 241 x 260 km x 51.6 deg orbit.  Castor 30A averaged 29.83 tonnes of thrust during its burn.

Payload separation occurred about 10 minutes after engine start.  A set of microsatellites subsequently deployed.  All of the satellites and the upper stage were expected to reenter within a few weeks.

aone1.jpg (4479 bytes)The Initial Climb Out was Slow due to Antares 1.2 Thrust to Weight Ratio

Although the payload was injected into a slightly lower orbit than originally announced, Orbital officials said that the rocket had functioned as planned.

It was the first of ten Antares flights planned to occur during the next three years to haul cargo to the International Space Station.  The next flight will orbit the first live Cygnus cargo hauler on a test flight to ISS.   The remainder of the flights will be operational Cygnus missions, with most using a more powerful Castor 30XL second stage.

orbd1-1.jpg (46448 bytes)Antares/Cygnus Mission ORB-D1

First Flight Cygnus was Mated to Antares in early September, 2013

The second flight Antares was assigned to the ORB-D1 mission, planned to be the first flight test of a Cygnus cargo hauling spacecraft.  The goal of the mission was to test Cygnus in orbit, to test rendezvous and, if all goes well, berthing with ISS, and to haul a small amount of cargo to the station. 

Cygnus was mated to Antares in the HIF during early September, 2013.  The payload fairing encapsulation occured on September 9, 2013.

orbd1-2.jpg (46635 bytes)Rollout for ORB-D1 Mission

On September 13, 2013, Antares and Cygnus rolled out to Pad 0A at Wallops Island.   At the time of the rollout, launch was planned to occur four days later.

On September 18, 2013, the second Antares 110 successfully orbited the first Cygnus spacecraft after an 14:58 UTC launch from Wallops Island, Virginia.  The ORB-D1 mission was lofted into low earth orbit en route to a cargo delivery demonstration mission to the International Space Station.

The Antares/Cygnus launch took place from Pad 0A at Wallops Island. Cygnus consisted of an Orbital Sciences-built propulsion module and a cylindrical cargo module built by Thales Alenia Space in Italy. 

Antare's Ukrainian-built, Russian-powered first stage performed a 3 minute 53 second burn. The upper stage stack separated and coasted for 1 minute 36 seconds to an altitude of 189 km before the second stage ignited for its 155 second burn. Cygnus separated about 10 minutes after liftoff into a 255 x 288 km x 51.64 deg orbit.

For this "ORB-D1" mission, Cygnus weighed about 4,100 kg.  Its pressurized cargo module had about 18 cubic meters of internal volume, which was partially filled with 700 kg of cargo for the Expedition 37 crew.  The spacecraft used a Japanese-built IHI BT-4 main thruster that produced 45.4 kgf thrust, 32 Aerojet Rocketdyne control thrusters that each produced 2.7 kgf thrust, and twin solar panels built by EADS Astrium Dutch Space.

Cygnus will perform a four day check out mission before being allowed to approach ISS for capture and berthing by the station's robot arm.

antares2.jpg (2020 bytes)ORB-D1 Launch

It was the second and final launch of an Antares 110 variant, which uses an ATK Castor 30A solid fueled second stage motor. The next two Antares/Cygnus launches will use Antares 120 rockets with higher performing Castor 30B motors. Subsequent launches will use Antares 130 rockets with substantially more powerful Castor 30XL motors.

It was the third of four planned orbital launches from Wallops Island in 2013, all by Orbital Sciences launch vehicles.

orb1.jpg (9218 bytes)Antares Launches Cygnus Cargo Mission

Orbital Sciences launched its third Antares rocket from Wallops Island, Virgina on Janaury 9, 2014 with the company's first operational Cygnus cargo mission to the International Space Station. The Orb-1 Commercial Resupply Services mission, the first of eight currently planned for NASA, began from Launch Complex 0A - part of the Mid-Atlantic Regional Spaceport - with an 18:07 UTC liftoff.

It was the first flight of an Antares 120 variant outfitted with an upgraded ATK Castor 30B second stage solid motor. Castor 30B was the same size and produced about the same thrust as the Castor 30A motor used during the first two launches, but it used a longer, larger nozzle that improved specific impulse to about 300 seconds. One more Antares 120 will fly this year, to be followed by the first Antares 130 with a more powerful, longer, and heavier Castor 30XL second stage motor.

The Yuzhnoye/Yuzhmash first stage burned its Kuznetsov/Aerojet AJ-26 engines for 3 minutes 54 seconds to lift the rocket to an altitude of about 100 km. After shutdown, the stage separated and the upper portion of the vehicle coasted upward to about 179 km altitude until the Castor 30B ignited about 1 minute 52 seconds after first stage shutdown. The payload fairing and interstage adapter separated shortly before the 128 second long second stage burn began.

Second stage burnout occurred about 7 minutes 54 seconds after liftoff. Cygnus, named "C. Gordon Fullerton" in honer of the NASA astronaut and test pilot who died in August, 2013, separated two minutes later in a 219 x 280 km x 51.654 deg orbit. Cygnus carried 1.261 tonnes of ISS cargo, including equipment, crew supplies, and 33 CubeSat microsatellites that will be released from ISS later this year. The spacecraft weighed about 4.69 tonnes including cargo.

Orbital Sciences officials had delayed the launch one day to study high solar radiation levels after a January 7 solar flare. A winter storm producing very cold temperatures had delayed the launch by one day earlier in the week. The entire mission had been delayed by three weeks when a coolant leak developed on the space station that required a pair of space walks by the ISS crew to repair.

AJ-26 Static Test Failure

On May 22, 2014, another AJ26-62 engine suffered an "anomaly" during a static test at NASA's Stennis Space Center Test Stand E-1.   The engine, reportedly heavily damaged in the incident that occurred approximately 30 seconds into a planned 54 second test, was being tested for a 2015 launch assignment.   It was the second known AJ26 failure at Stennis.  The first occurred during 2011.  The impact of the failure on a planned June launch of the fourth Antares with Cygnus on the Orb-2 ISS resupply mission was to be determined.

orb2-13.jpg (13900 bytes)Antares Launches Cygnus/Orb-2

Orbital Sciences' Antares boosted a Cygnus spacecraft into orbit from Wallops Island, Virginia on July 13, 2014 to begin NASA's Orb-2 International Space Station resupply mission. Cygnus Orb-2, named "Janice Voss" in honor of the late former Orbital employee and NASA astronaut, carried 1,493.8 kg of crew supplies, vehicle hardware, science equipment, and other equipment inside its cylindrical pressure hull.  Including cargo, Cygnus weighed about 4.923 tonnes at liftoff.

Liftoff of the fourth Antares rocket took place from Wallops Mid-Atlantic Regional Spaceport Pad 0A at 16:52 UTC. Antares' twin AJ-26 engines produced about 332 tonnes of   liftoff thrust and burned for 3 minutes 55 seconds to lift the vehicle to more than 158 km altitude and a velocity of about 4.5 km/sec. The second stage and payload section separated and coasted for about 1 minute 45 seconds before the Castor 30B second stage
motor ignited to produce an average of more than 28 tonnes of thrust during a 2 minute 17 second burn. Just before second stage ignition, the payload fairing and interstage sections separated. Cygnus separated into a 191 x 284 km x 51.64 deg orbit.

orb2b.jpg (20362 bytes)"Janice Voss" approaches ISS

It was the fourth Antares launch, the third Cygnus spacecraft flight, and the second contracted ISS cargo supply mission for Cygnus. "Antares 120", a variant with a Castor 30B second stage, flew for the second and final time during the mission. "Antares 130" with a longer, more powerful Castor 30XL motor will perform subsequent ISS cargo missions beginning later in 2014.

The launch was originally scheduled for May, 2014, but ISS conflicts forced an initial delay. Then, on May 22, 2014, an AJ-26 being test fired at Stennis Space Center suffered a catastrophic failure 30 seconds into a planned 54 second burn. The failure destroyed the engine and triggered an investigation. Orbital did not reveal the cause of the failure. The Orb-2 Antares engines were cleared for flight following borescope inspections and a review of their own test firing data.

Cygnus "Janice Voss" reached ISS on July 16, 2014.


ant5-1.jpg (13013 bytes)Antares/Cygnus Launch Fails

First Antares 130 on Pad 0A with Orb-3/Cygnus Payload

The fifth Orbital Sciences Antares rocket suffered a fiery failure moments after liftoff with the Orbital CRS-3 (Orb-3) Cygnus ISS resupply mission from Wallops Island, Virginia on October 28, 2014. Flying for the first time as an Antares 130 variant with a lengthened Castor 30XL second stage, the rocket lifted off from Pad 0A at 22:22 UTC.

The two AJ-26 first stage main engines ignited at T+0 seconds, followed by liftoff at about T+2 seconds. The initial moments of the ascent seemed normal until about T+14 seconds when the engine exhaust plume suddenly changed color from its usual intense white to a yellowish color. About one second later a ball of fire erupted from the aft section of the rocket and propulsion ceased.

The big rocket momentarily hung in midair before beginning to fall, engine section first, trailing a stream of fire. At about T+24 seconds, the nearly fully fueled Antares rocket impacted between the beach and the pad itself, creating a huge fireball that flung debris in all directions. An intense post-impact fire that appeared to involve pieces of the second stage solid propellant burned for many minutes.

Although Pad 0A exhibited signs of obvious damage, the basic reinforced concrete structure of the launch pad and other elements of the facility appeared on NASA TV to still be intact - one hopeful sign amidst the otherwise catastrophic scene.

ant5-3.jpg (5652 bytes)The Initial Fireball

Orbital CRS-3 included a Cygnus spacecraft loaded with 2.215 tonnes of cargo for the International Space Station, heaviest-ever for Cygnus which weighed about 5.644 tonnes including cargo.  The cargo included crew provisions, research hardware, emergency equipment, spacewalk supplies and packing materials. It was slated to stay at ISS for about one month until returning to a destructive reentry with about 1.36 tonnes of trash.

It was the first Antares failure. The Ukrainian/Russian/American rocket first flew on April 21, 2013. The second Antares carried the first Cygnus to ISS on the Orb-D1 mission on September 18, 2013. The subsequent operational Orb-1 and Orb-2 missions lifted off on January 9 and July 13, 2014, respectively.

ant5-4.jpg (10541 bytes)Ground Impact

Although the cause of the failure was not known immediately after launch, attention was expected to focus on the AJ-26 main engines, which are decades-old NK-33 Russian rocket engines that have been refurbished by U.S. Aerojet-Rocketdyne. On May 22, 2014, an AJ-26 being test fired at Stennis Space Center suffered a catastrophic failure 30 seconds into a planned 54 second burn. The failure destroyed the engine and triggered an investigation.

Orbital did not reveal the cause of the failure and damage to the test stand had prevented renewed testing by the time of the Orb-3 liftoff. The Orb-2 and Orb-3 Antares engines, which had previously been tested at Stennis before the May failure, were cleared for flight following borescope inspections and a review of their own test firing data.

Orbital Announces Accident Recovery Plans

On November 5, 2014, Orbital Sciences announced its plans to recover from the October 28, 2014 Antares launch failure. Its plans included steps both to restore Antares to flight and to fulfill the company's contractual requirements under NASA's Commercial Resupply Services (CRS) program.

Orbital's decisions were informed in part by early findings of the Antares launch failure Accident Investigation Board (AIB), which was focusing on a "probable turbopump-related failure in one of the two Aerojet Rocketdyne AJ26 stage one main engines". As a result of the findings, Orbital announced that it would likely discontinue use of the engines on future Antares launch vehicles.

The company was already planning to replace the AJ26 engines, which are refurbished forty year old NK33 engines made by Kuznetsov for the USSR's N1 rocket. Even before the failed Antares launch, Orbital had decided on an alternate, modern engine, thought most likely to be an Energomash RD-18x or RD-19x series staged combustion kerosene/LOX engine.

The new engines would not have flown on Antares until 2017 at the earliest, but Orbital now intends to accelerate the replacement effort and aim for a 2016 first flight of the re-engined rocket from Wallops. If no more AJ26 engines are flown, a two year or more gap in Antares flights will result. To compensate, Orbital said that it plans to fly one or two Cygnus cargo missions to the International Space Station on "non-Antares" rockets during 2015-2016.

Likely potential temporary Antares stand-ins include Atlas 5, Delta 4, Falcon 9, and Soyuz.

The company planned to take advantage of the heavier lifting capabilities of both the "non-Antares" rockets and of the upgraded Antares after 2016 to carry more cargo in each Cygnus than originally planned. The result will be one less Cygnus mission than originally planned, eliminating the need to build a spacecraft to replace the Cygnus lost on October 28.

Atlas V as Antares Stand-in

On December 9, 2014, Orbital announced that had contracted with United Launch Alliance for an Atlas 5 launch of a Cygnus cargo spacecraft during the fourth quarter of 2015, with an option for a second flight in 2016.  Atlas would carry Cygnus toward ISS from Cape Canaveral, Florida's Space Launch Complex 41.   Use of the powerful rocket would allow each Cygnus to carry almost 35% more payload mass than previously planned for its Antares launches.

RD-181 to Replace NK-33/AJ-26

On December 16, Orbital revealed that it would buy RD-181 engines directly from Khimki, Russia’s NPO Energomash to replace the previous NK-33/AJ-26 engines.  RD-181, a downgraded, export version of Russia's RD-191 Angara engine, would fly in shipsets of two to mimic as much as possible the original dual AJ-26 behavior.  Once equipped with two RD-181 engines, Antares performance to low earth orbit will by improved by about 20%.  The first RD-181 engines were expected to arrive at Wallops Island, Virginia in mid-2015 to begin the process of vehicle integration and testing.  That first set will likely be used for a hot-fire test with an Antares first stage on the repaired Wallops launch pad in 2015.  A second set of engines will arrive during the Fall of 2015.

Orbital expected to to complete its $1.9 billion contract to deliver 20 tonnes of of cargo to the ISS by the end of 2016 using one less Antares/Cygnus launch than originally planned - four more instead of five.  Although a pair of RD-181 engines can deliver about 45 tonnes more thrust than two AJ-26 engines, they will be dialed back to the old engine's thrust level until modified first stages are put into service to take advantage of the extra thrust. 

In a January 2015 press release, Energomash revealed that each RD-181 would produce 186 tonnes thrust at sea level.  Energomash agreed to deliver as many as 60 RD-181 engines to Orbital within a contract envelope value of about $1 billion.  RSC Energia delivered the first two RD-181 engines, for NTO Energomash, to Orbital ATK on July 16, 2015.

oa5.jpg (18900 bytes)Re-engined Antares Launches

Orbital ATK's Antares launch vehicle returned to flight on October 17, 2016, successfully orbiting the company's Cygnus OA-5 cargo hauling mission from Wallops Island, Virginia. The success came two years after the previous Antares exploded above Pad 0A, damaging the pad and forcing a re-design of the launch vehicle itself. The resulting "Antares 230" retained the basic structure and avionics of the original, but gained two new Energomash RD-181 engines in place of the AJ-26 engines that powered the first five flights. An AJ-26 turbopump failure triggered the 2014 explosion.

Cygnus OA-5 was the third enhanced Cygnus with a stretched cargo module, but the first to fly on Antares. Atlas 5 rockets orbited the first two enhanced Cygnus spacecraft on Missions OA-4 and OA-6 during the two-year Antares stand-down. OA-5 carried a total 2,209 kg of cargo for the International Space Station, along with 133 kg of packaging. The spacecraft weighed about 6,163 kg at liftoff, easily making it the heaviest-ever Antares payload . Cygnus OA-5 was named in honor of former astronaut Alan Poindexter, who flew two space shuttle missions.

oa5b.jpg (6686 bytes)OA-5 Liftoff

Two RD-181 engines powered the Antares 230 Ukrainian-built first stage during its 23:45 UTC liftoff, each producing about 186 tonnes of sea level thrust to lift the roughly 300 tonne launch vehicle and payload. The first stage burned for about 200 seconds. After first stage shutdown, the second stage and payload section separated and coasted for about 45 seconds before the Castor 30XL second stage motor ignited to produce an average of about 51 tonnes of thrust during its roughly 160 second burn. It was the first in-space test of Castor 30XL, which had previously attempted a debut on the failed 2014 launch. Just before second stage ignition, the payload fairing and interstage sections separated.

Cygnus separated into a 214 x 362 km x 51.62 deg orbit at the 541.31 second mark. The spacecraft will wait in orbit until October 23 to approach ISS to allow for the next crewed Soyuz mission docking.

Another Antares first stage performed a roughly 30 second-long static fire test of the new RD-181 engined Antares on Pad 0A on May 31, 2016. That stage will be used on a future flight.

Antares 230 (Northrop Grumman)Northrop Grumman Acquires Orbital ATK, Antares

Antares 230+ as Shown in July, 2018 Northrop Grumman Fact Sheet

On June 6, 2018, Northrop Grumman, having won government approval, completed its aquisition of Orbital ATK. A new Northrop Grumman fact sheet was issued for Antares during the changeover. The fact sheet spelled out performance improvements that were likely the result of plans for first stage intertank and forward skirt structural improvements, Castor 30XL dry mass reduction, and other changes related to knowledge gained during the first three RD-181 powered Antares 230 series flights. The improved variant was named "Antares 230+" by an Orbital ATK official just before the acquisition.

The fact sheet showed Antares performance to a 200 km x 51.6 deg ISS type orbit increased from 6.3 tonnes to more than 7.4 tonnes. It showed 3 tonnes to a 500 km sun synchronous orbit when a hydrazine monopropellant Orbit Adjust Module third stage was employed in the Antares 231 variant. Use of a Star 48VB third stage motor provided 1.6 tonnes to escape velocity as Antares 232, better than Delta 2 or 2H and better than the old Atlas Centaurs of the 1970s-80s that boosted Pioneers and Mariners into deep space.

The improved performance was likely provided to support Antares/Cygnus CRS-2 missions, set to run from 2019 through 2024. At least six CRS-2 flights are expected. Antares is expected to provide the launch services for the first three missions, and possibly for all of the flights.


Vehicle Configurations (Estimated)

(metric tons)
(1) 200 km x 51.6 deg from WFF
(2) 500 km x 51.6 deg from WFF
Sun Synchronous
Earth Orbit from VAFB or KLC
(5) 200 km x 98 deg
(6) 500 km x 98 deg
Earth Escape (C3=0) from
(1) WFF
(2) CC
Configuration LIftoff
(metric tons)
(no payoad)
Antares 110 (2 Stg, i.e. COTS LV Verification) (2013) ~4.45 t (1) ~3.68 t (5) - Antares Stg 1 + Castor 30A Stg 2
+ Cygnus ("Cots Visiting Vehicle")
~40.5 m ~276 t
Antares 120 (2 Stg, i.e. COTS Demo) (2013) 4.7 t (1) 3.9 t (5) - Antares Stg 1 + Castor 30B Stg 2
+ Cygnus
~40.5 m ~276 t
Antares 121 (3 Stg BTS) 4.2 t (2) 3.4 t (6) 0.85 t (1) Antares Stg 1 + Castor 30B Stg 2
+ Bi-Propellant Third Stage (BTS)
~40.5 m ~277 t
Antares 130 (2013) 5.5 t (1) 4.5 t (5) - Antares Stg 1 + Castor 30XL Stg 2 ~43 m ~286 t
Antares 131 (2014) 5.0 t (2) 4.2 t (6) 1.1 t (1) Antares Stg 1 + Castor 30XL Stg 2
+ Star 48BV Stg 3
~43 m ~286 t
Antares 230 6.4 t (1) - - Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 ~43 m? ~286 t?
Antares 231 5.9 t (2) - - Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 + BTS Stg 3 ~43 m? ~286 t?
Antares 232 - - 1.45 t (1) Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 + Star 48V Stg 3 ~43 m? ~286 t?
Antares 230+ 7.4 t+ (1) - - Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 ~43 m? ~286 t?
Antares 231+ 6.2 t (2) 3 t (6) - Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 + OAM Stg 3 ~43 m? ~286 t?
Antares 232+ - - 1.6 t (1) Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 + Star 48VB Stg 3 ~43 m? ~286 t?
Antares 233+ - - - Antares 2xRD181 Stg 1 + Castor 30XL Stg 2 + Orion 38 Stg 3 ~43 m? ~286 t?
Taurus II (3 Stg S48) - - 1.3 t (2) Taurus II Stg 1 + Castor 30 Stg 2
+ Star 48V Stg 3
~40.5 m ~278 t
Taurus II (Enhanced Stg 2) 6.6 t (1)
6.0 t (2)
5.2 t (5) - Taurus II Stg 1 + "Enhanced" Stg 2 ~40.5 m ~283 t
Taurus II (Enhanced Stg 2 + Star 48) - - 1.6 t (2) Taurus II Stg 1 + "Enhanced" Stg 2
+ Star 48V Stg 3
~40.5 m ~285 t

Vehicle Components

Stage 1
Stage 1
Stage 2
(Castor 30A/B)
Stage 2
(Castor 30XL)
Stage 3
Orbit Adjust Module (OAM)
Stage 2
Stage 3
Star 48VB
Diameter (m) 3.9 m 3.9 m 2.34 m 2.34 m - 3.9 m 1.245 m 3.9 m
Length (m) 27.6 m 27.6 m? 3.5 m ~ 5.94 m - - 2.076 m 9.9 m
Empty Mass (tonnes) 18.8 t (est) 18.8 t (est)? 1.224 t ~ 2.1 t (est) - ~ 0.155 t 0.972 t
Propellant Mass (tonnes) ~242.4 t usu. (est) ~242.4 t usu. (est)? 12.834 ~23.1 t (est) 0.68 t (est)? ~ 2.009 t -
Total Mass (tonnes) ~261.2 t (est) ~261.2 t (est)? 14.06 ~25.2 t (est) - ~ 2.164 t -
Engine NK33 (AJ26-62) RD-181 Castor 30A/B Castor 30XL 500N? RD-0124 Star 48V -
Engine Mfgr Kuznetsov Energomash ATK ATK IHI? Kosberg ATK -
Fuel Kerosene Kerosene solid HTPB solid HTPB MMH? Kerosene solid -
Oxidizer LOX LOX solid HTPB solid HTPB NTO? LOX solid -
(SL tons)
307.94 t (100%)
332.58 t (108%)
~333 t (Antares Thottle?)
372 t (RD-181 Max)
- - - - - -
(Vac tons)
334.00 t (100%)
370.14 t (108%)
~370 t (Antares Throttle?)
~402 t (RD-181 Max est)
28.4 t (avg, est) 51.1 t (avg, est) - 30 t 7 t (avg) -
ISP (SL sec) 297 s 311 s? - - - - - -
ISP (Vac sec) 331 s 337 s? 293.2 s/300.6 s (est) 301 s (est) - 359 s 292.1 s (avg) -
Burn Time (sec) 235 s 235 s? 155 s 155 s - - 84.1 s -
No. Engines 2 2 1 1 ? 1 1 -
Throttle 56-108% Throttle 38-100%? TVC Nozzle TVC Nozzle - 4 Chambers
Also Powers
Soyuz 2 Stg 2
TVC nozzle -

Antares Launch History

 Date     Vehicle      No. Payload           Mass  Site   Orbit
04/21/13  Antares 110  A1  Cygnus Mass Sim.  3.8   WI 0A  LEO 
09/18/13  Antares 110  A2  Cygnus ORB-D1     4.13  WI 0A  LEO/ISS
01/09/14  Antares 120  A3  Cygnus/Orb 1      4.69  WI 0A  LEO/ISS
07/13/14  Antares 120  A4  Cygnus/Orb-2      4.923 WI 0A  LEO/ISS
10/28/14  Antares 130  A5  Cygnus/Orb-3      5.644 WI 0A [FTO][1]
10/17/16  Antares 230  A7  Cygnus/OA-5       6.163 WI 0A  LEO/ISS[2]
11/12/17  Antares 230  A8  Cygnus OA-8       6.173 WI 0A  LEO/ISS
05/21/18  Antares 230  A6  Cygnus OA-9       6.173 WI 0A  LEO/ISS
[1] Failed at T+14 sec.  Fell back near launch pad.  AJ26 turbopump 
[2] First flight with RD-181 engines.  First in-space Castor 30XL 


Taurus II Users Guide at
Sketch of the Taurus II at
Description on Orbital web site at
NASA COTS Press Release at
Taurus Fact Sheet at
ATK Space Propulsion Products Catalog, May 2008
Taurus II Development Status, AIAA Paper, July, 2008
Taurus II Development Updates at (2008-2013)
Antares 23x Fact Sheet (December, 2014)
Energomash RD-181 for Antares Press Release, January 2015
Antares Fact Sheet, Northrop Grumman, June 6, 2018