Orbital (OSC) began in-house design of a new medium-class launch vehicle in 2007. In early December 2007, Orbital provided an initial glimpse of its Taurus II plans. The company said that Taurus II would, if it were developed, 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.
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.
Vehicle Description
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.
Also read: Space Shuttle – Space Launch Report
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 143 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.
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-during “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.
AJ26-62 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.
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. The second first stage, apparently the initial flight stage, was en route to Wallops by mid-April.
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%. An upgraded “Castor 30B” would power Flights Two and Three before Castor 30XL would enter service on Flight Five. Details were not available, and it was not immediately clear if the decision had shelved plans for the “enhanced” liquid upper stage.
Vehicle Configurations (Estimated)
| LEO Payload (metric tons) (1) 200 km x 51.6 deg from WFF (2) 500 km x 51.6 deg from WFF (3) 200 km x 28.5 deg from CC (4) 500 km x 28.5 deg from CC | Sun Synchronous Earth Orbit from VAFB (5) 200 km x 98 deg (6) 500 km x 98 deg | Earth Escape (C3=0) from CC | Configuration | LIftoff Height (meters) | Liftoff Mass (metric tons) (no payoad) | |
| Taurus II (2 Stg, i.e. COTS Demo) | 5.1 t (1) 5.5 t (3) | 4.2 t (5) | – | Taurus II Stg 1 + Castor 30 Stg 2 + Cygnus (“Cots Visiting Vehicle”) Service Module | ~40.5 m | ~276 t |
| Taurus II (3 Stg ORK) | 4.9 t (2) 5.3 t (4) | 4.1 t (6) | – | Taurus II Stg 1 + Castor 30 Stg 2 + Orbit Raising Kit (ORK) Stg 3 | ~40.5 m | ~277 t |
| Taurus II (3 Stg S48) | – | – | 1.3 t | 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) 7.2 t (3) 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 | Taurus II Stg 1 + “Enhanced” Stg 2 + Star 48V Stg 3 | ~40.5 m | ~285 t |
Vehicle Components
| Stage 1 | Stage 2 (Castor 30A) | Stage 3 Orbit Raising Kit | “Enhanced” Stage 2 | Stage 3 Star 48V | Payload Fairing | |
| Diameter (m) | 3.9 m | 2.34 m | – | 3.9 m | 1.245 m | 3.9 m |
| Length (m) | 27.6 m | 3.5 m | – | – | 2.076 m | 9.9 m |
| Empty Mass (tonnes) | 18.8 t (est) | 1.224 t | – | ~ | 0.155 t | 0.972 t |
| Propellant Mass (tonnes) | ~242.4 t usu. (est) | 12.834 | 0.68 t (est) | ~ | 2.009 t | – |
| Total Mass (tonnes) | ~261.2 t (est) | 14.06 | – | ~ | 2.164 t | – |
| Engine | NK33 (AJ26-62) | Castor 30 | 500N | RD-0124 | Star 48V | – |
| Engine Mfgr | Kuznetsov | ATK | IHI | Kosberg | ATK | – |
| Fuel | Kerosene | solid HTPB | MMH | Kerosene | solid | – |
| Oxidizer | LOX | solid HTPB | NTO | LOX | solid | – |
| Thrust (SL tons) | 307.94 t (100%) 332.58 t (108%) | – | – | – | – | – |
| Thrust (Vac tons) | 334.00 t (100%) 370.14 t (108%) | 28.4 t (avg, est) | – | 30 t | 7 t (avg) | – |
| ISP (SL sec) | 297 s | – | – | – | – | – |
| ISP (Vac sec) | 331 s | 301 s | – | 359 s | 292.1 s (avg) | – |
| Burn Time (sec) | 235 s | 136 s | – | – | 84.1 s | – |
| No. Engines | 2 | 1 | ? | 1 | 1 | – |
| Comments | Throttle 56-108% | TVC Nozzle | – | 4 Chambers Also Powers Soyuz 2 Stg 2 | TVC nozzle | – |
