Antares (rocket)

Development

The NASA COTS award was for US$171 million and Orbital Sciences expected to invest an additional $150 million, split between $130 million for the booster and $20 million for the spacecraft. A Commercial Resupply Service contract of $1.9 billion for 8 flights was awarded in 2008. As of April 2012, development costs were estimated at $472 million.

On June 10, 2008 it was announced that the Mid-Atlantic Regional Spaceport, formerly part of the Wallops Flight Facility, in Virginia, would be the primary launch site for the rocket. Launch pad 0A (LP-0A), previously used for the failed Conestoga rocket, would be modified to handle Antares. Wallops allows launches which reach the International Space Station's orbit as effectively as those from Cape Canaveral, Florida, while being less crowded. The first Antares flight launched a Cygnus mass simulator.

On December 10, 2009 Alliant Techsystems Inc. (ATK) test fired their Castor 30 motor for use as the second stage of the Antares rocket. In March 2010 Orbital Sciences and Aerojet completed test firings of the NK-33 engines. On February 22, 2013 a hot fire test was successfully performed, the entire first stage being erected on the pad and held down while the engines fired for 29 seconds.

First stage

The first stage of Antares burns RP-1 (kerosene) and liquid oxygen (LOX). As Orbital had little experience with large liquid stages and LOX propellant, the first stage core was designed and is manufactured in Ukraine by Yuzhnoye SDO and includes propellant tanks, pressurization tanks, valves, sensors, feed lines, tubing, wiring and other associated hardware. Like the Zenit—also manufactured by Yuzhnoye—the Antares vehicle has a diameter of 3.9 m (150 in) with a matching 3.9 m payload fairing.

Antares 100

The Antares 100-series first stage was powered by two Aerojet AJ26 engines. These began as Kuznetsov NK-33 engines built in the Soviet Union in the late 1960s and early 1970s, 43 of which were purchased by Aerojet in the 1990s. 20 of these were refurbished into AJ26 engines for Antares. Modifications included equipping the engines for gimballing, adding US electronics, and qualifying the engines to fire for twice as long as designed and to operate at 108% of their original thrust. Together they produced 3,265 kilonewtons (734,000 lb_f) of thrust at sea level and 3,630 kN (816,100 lb_f) in vacuum.

Following the catastrophic failure of an AJ26 during testing at Stennis Space Center in May 2014 and the Orb-3 launch failure in October 2014, likely caused by an engine turbopump, the Antares 100-series was retired.

Antares 200

Due to concerns over corrosion, aging, and the limited supply of AJ26 engines, Orbital had selected new first stage engines. The new engines were planned to debut in 2017 and allow Orbital to bid on a second major long-term contract for cargo resupply of the ISS. Less than one month after the loss of the Antares rocket in October 2014, Orbital announced that it would no longer fly Antares with AJ26 engines, and the first flight of Antares with new first stage engines would be moved up to 2016. As of August 2016, the first flight of the re-engined Antares 230 configuration is anticipated for August 22, 2016, carrying the Cygnus CRS OA-5 cargo to the ISS. However, a new mission update from Orbital ATK's official page said that the mission was delayed to mid-September due to many reasons, including the company’s continuing processing, inspection and testing of the flight vehicle at Wallops Island, and NASA’s scheduling of crew activities on the International Space Station in preparation for upcoming cargo and crew launches. A more specific launch date would be identified in the coming weeks. As of October 2016, the launch was scheduled to happen on October 13, 2016 but was delayed due to Hurricane Nicole which formed over the Atlantic Ocean and headed towards Bermuda, the rocket's tracking site. If there are no further problem the launch will occur on October 17, 2016.

In late October 2014, the Russian news agency TASS reported that Orbital Sciences had preliminarily selected the NPO Energomash RD-193 to power the second version of the Antares first stage, and in December 2014 Orbital Sciences announced that the RD-181—a modified version of the RD-191—would replace the AJ26 on the Antares 200-series. The first engines are scheduled to arrive from NPO Energomash in summer 2015, where an on-pad 29-second static fire test is projected to occur in fall 2015.

The Antares 200 and 300 first stages will be powered by two RD-181 engines, which will provide 440 kilonewtons (100,000 lbf) more thrust than the dual AJ26 engines used on the Antares 100. Orbital plans to adapt the existing core stage to accommodate the increased performance in the 200 Series, allowing Antares to deliver up to 7,000 kilograms (15,000 lb) to low Earth orbit. The excess performance of the Antares 200-series will allow Orbital to fulfill its ISS resupply contract in only four additional flights, rather than the five that would have been required with the Antares 100-series.

Antares 300

While the 200 series uses the RD-181 by adapting the originally ordered 100 Series stages (KB Yuzhnoye/Yuzhmash, Zenit derived), it requires under throttling the RD-181 engines, which reduces performance. Thus, the 300 series will use a new first stage core designed for the full thrust and performance of the RD-181 engine.

Second stage

The second stage is an Orbital ATK Castor 30-series solid-fuel rocket, developed as a derivative of the Castor 120 solid motor used as Minotaur-C's first stage. The first two flights of Antares used a Castor 30A, which was replaced by the enhanced Castor 30B for subsequent flights. The Castor 30B produces 293.4 kN (65,960 lb_f) average and 395.7 kN (88,960 lb_f) maximum thrust, and uses electromechanical thrust vector control. For increased performance, the larger Castor 30XL is available and will be used on ISS resupply flights to allow Antares to carry the Enhanced Cygnus.

Third stage

Antares offers two optional third stages, the Bi-Propellant Third Stage (BTS) and a Star 48-based third stage. BTS is derived from Orbital Sciences' GEOStar spacecraft bus and uses nitrogen tetroxide and hydrazine for propellant; it is intended to precisely place payloads into their final orbits. The Star 48-based stage uses a Star 48BV solid rocket motor and would be used for higher energy orbits.

Fairing

The 3.9-meter (13 ft) diameter, 9.9-meter (32 ft) high fairing is manufactured by Applied Aerospace Structures Corporation of Stockton, California, which also builds other composite structures for the vehicle, including the fairing adaptor, stage 2 motor adaptor, stage 2 interstage, payload adaptor, and avionics cylinder.

Configurations and numbering

The first two test flights used a Castor 30A second stage. All subsequent flights will use either a Castor 30B or Castor 30XL. The rocket's configuration is indicated by a three-digit number, the first number representing the first stage, the second the type of second stage, and the third the type of third stage.

Inaugural flight

Originally scheduled for 2012, the first Antares launch, designated A-ONE was conducted on April 21, 2013, carrying the Cygnus Mass Simulator (a boilerplate Cygnus spacecraft) and four CubeSats contracted by Spaceflight Incorporated: Dove 1 for Cosmogia Incorporated (now Planet Labs) and three PhoneSat satellites – Alexander, Graham and Bell for NASA.

Prior to the launch, a 27-second test firing of the rocket's AJ26 engines was conducted successfully on February 22, 2013, following an attempt on February 13 which was abandoned before ignition.

A-ONE used the Antares 110 configuration, with a Castor 30A second stage and no third stage. The launch took place from Pad 0A of the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia. LP-0A was a former Conestoga launch complex which had only been used once before, in 1995, for the Conestoga's only orbital launch attempt. Antares became the largest — and first — liquid-fuelled rocket to fly from Wallops Island, as well as the largest rocket launched by Orbital Sciences.

The first attempt to launch the rocket, on April 17, 2013, was scrubbed after an umbilical detached from the rocket's second stage, and a second attempt on April 20 was scrubbed due to high altitude winds. At the third attempt on April 21, the rocket lifted off at the beginning of its launch window. The launch window for all three attempts was three hours beginning at 21:00 UTC (17:00 EDT), shortening to two hours at the start of the terminal count, and ten minutes later in the count.

October 2014 incident

On October 28, 2014, the attempted launch of an Antares carrying a Cygnus cargo spacecraft on the Orb-3 resupply mission failed catastrophically six seconds after liftoff from Mid-Atlantic Regional Spaceport at Wallops Flight Facility, Virginia. An explosion occurred in the thrust section just as the vehicle cleared the tower, and it fell back down onto the pad. The Range Safety officer sent the destruct command just before impact. There were no injuries. Orbital Sciences reported that Launch Pad 0A "escaped significant damage," though initial estimates for repairs were in the $20 million range. Orbital Sciences formed an anomaly investigation board to investigate the cause of the incident. They traced it to a failure of the first stage LOX turbopump, but could not find a specific cause. However, the refurbished NK-33 engines, originally manufactured over 40 years earlier and stored for decades, were suspected as having leaks, corrosion, or manufacturing defects that had not been detected. On October 6, 2015, almost one year after the accident, Pad 0A was restored to use. Total repair costs were about $15 million.

Following the failure, Orbital sought to purchase launch services for its Cygnus spacecraft in order to satisfy its cargo contract with NASA, and on December 9, 2014, Orbital announced that at least one, and possibly two, Cygnus flights would be launched on Atlas V rockets from Cape Canaveral Air Force Station. As it happened, Cygnus OA-4 and OA-6 were launched with an Atlas V and the Antares 230 performed its maiden flight with Cygnus OA-5 in October 2016. Further missions will see one more Atlas launch in March 2017 (OA-7), fulfilling Orbital's contractual obligations towards NASA, followed by regular service by Antares 230 with OA-8E in July 2017 and further missions from their extended contract.

List of missions

List includes only currently manifested missions. All missions are launched from Mid-Atlantic Regional Spaceport Launch Pad 0A.

Note: Cygnus CRS OA-4, the first Enhanced Cygnus mission, and OA-6 were propelled by Atlas V 401 launch vehicles while the new Antares 230 was in its final stages of development. Cygnus CRS OA-7 was also switched to an Atlas V scheduled for March 2017.

Launch sequence

The following table shows a typical launch sequence of Antares-100 series rockets, such as for launching a Cygnus spacecraft on a cargo resupply mission to the International Space Station.