As part of the COTS program, Orbital would be expected to conduct a successful demonstration of its rocket booster and spacecraft. If both demonstration flights were successful, Orbital would be eligible for a lucrative Commercial Resupply Service contract of $1.9 billion for eight flights to the ISS.
Originally designated the Taurus II, Orbital Sciences renamed the vehicle Antares, after the star of the same name, on December 12, 2011.
As of April 2012, development costs were estimated at $472 million.
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.
Because of concerns over corrosion, aging, and the limited supply of AJ26 engines, Orbital had selected new first stage engines to bid on a second major long-term contract for cargo resupply of the ISS. After the loss of the Antares rocket in October 2014, Orbital Sciences announced that the Russian RD-181—a modified version of the RD-191—would replace the AJ-26 on the Antares 200-series. The first flight of the Antares 230 configuration using the RD-181 launched on October 17, 2016, carrying the Cygnus OA-5 cargo to the ISS.
The Antares 200 and 200+ first stages are powered by two RD-181 engines, which provide 440 kilonewtons (100,000 lbf) more thrust than the dual AJ26 engines used on the Antares 100. Orbital adapted the existing core stage to accommodate the increased performance in the 200 Series, allowing Antares to deliver up to 6,500 kg (14,300 lb) to low Earth orbit. The surplus 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.
The Antares was upgraded to the Antares 230+ for the NASA Commercial Resupply Services 2 contract. NG-12, launched November 2, 2019, was the first NASA CRS-2 mission to ISS using the 230+ upgrades. The most significant upgrades were structural changes to the intertank bay (between the LOX and RP-1 tanks) and the forward bay (forward of the LOX). Additionally, the company is working on trajectory improvements via a "load-release autopilot" that will provide greater mass to orbit capability.
The Castor 30XL upper stage for Antares 230+ is being optimized for the CRS-2 contract. The initial design of the Castor 30XL was conservatively built, and after gaining flight experience it was determined that the structural component of the motor case could be lightened.
Antares offers three optional third stages: the Bi-Propellant Third Stage (BTS), a Star 48-based third stage and an Orion 38 motor. BTS is derived from Orbital's GEOStar, a 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. The Orion 38 is used on the Minotaur and Pegasus rockets as an upper stage.
On January 14, 2016, NASA awarded three cargo contracts via CRS-2. Orbital ATK's Cygnus was one of these contracts.
According to Mark Pieczynski, Orbital ATK Vice President, Flight Systems Group, "A further improved version [of Antares for CRS-2 contract] is in development which will include: Stage 1 core updates including structural reinforcements and optimization to accommodate increased loads. (Also) certain refinements to the RD-181 engines and CASTOR 30XL motor; and Payload accommodations improvements including a 'pop-top' feature incorporated in the fairing to allow late Cygnus cargo load and optimized fairing adapter structure".
Previously, it was understood that these planned upgrades from the Antares 230 series would create a vehicle known as the Antares 300 series. However, when asked specifically about Antares 300 series development, Mr. Pieczynski stated that Orbital ATK has "not determined to call the upgrades, we are working on, a 300 series. This is still TBD".
In May 2018, the Antares program manager Kurt Eberly indicated that the upgrades will be referred to as Antares 230+.
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.
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.
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 Cygnus OA-6 were launched with an Atlas V and the Antares 230 performed its maiden flight with Cygnus OA-5 in October 2016. One further mission was launched aboard an Atlas in April 2017 (Cygnus OA-7), fulfilling Orbital's contractual obligations towards NASA. It was followed by the Antares 230 in regular service with Cygnus OA-8E in November 2017, with three further missions scheduled on their extended contract.
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. The coast phase is required because the solid-fuel upper stage has a short burn time.
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