Due to Orbital's limited experience with large liquid stages, the construction was subcontracted to the Ukrainian companies Pivdenne and Pivdenmash.

Following Russia's invasion of Ukraine, Northrop Grumman announced plans for the Antares 300, featuring a new first stage developed in partnership with Firefly Aerospace.

The new first stage, similar to Firefly's MLV launch vehicle, will incorporate composite structures and seven Miranda engines, increasing Antares's payload capacity.

Later that year, on September 18, the rocket successfully launched Orb-D1, the first Cygnus mission to rendezvous with the International Space Station (ISS).

The COTS program also funded the development of SpaceX's Dragon spacecraft and Falcon 9 rocket, aiming to stimulate the commercial space industry by creating two medium-lift launch vehicles.

To encourage innovation, NASA offered funding through the Commercial Orbital Transportation Services (COTS) program to support the development of new spacecraft and launch vehicles.

On February 19, 2008, NASA announced that it would award Orbital Sciences Corporation a COTS contract worth $171 million.

[12] As part of the COTS program, Orbital would be expected to conduct a successful demonstration of its rocket booster and spacecraft.

[13] In June 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.

[15] Wallops allows launches which reach the International Space Station's orbit as effectively as those from Cape Canaveral, Florida, while being less crowded.

[17] On December 10, 2009, Alliant Techsystems Inc. (ATK) test-fired their Castor 30 motor for use on the second stage of the Antares rocket.

As Orbital had little experience with large liquid stages and LOX propellant, the first stage core was designed and is manufactured in Ukraine by Pivdenne Design Office and Pivdenmash[12] and includes propellant tanks, pressurization tanks, valves, sensors, feed lines, tubing, wiring and other associated hardware.

Additionally, the company is working on trajectory improvements via a "load-release autopilot" that will provide greater mass to orbit capability.

[8] For increased performance, the larger Castor 30XL is available[30] and will be used on ISS resupply flights to allow Antares to carry the Enhanced Cygnus.

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.

Originally scheduled for 2012, the first Antares launch, designated A-ONE[41] was conducted on April 21, 2013,[42] 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,[43] Graham and Bell for NASA.

[11][46] 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.

[47] An explosion occurred in the thrust section just as the vehicle cleared the tower, and it fell back down onto the launch pad.

[50] Orbital Sciences reported that Launch Pad 0A "escaped significant damage",[49] though initial estimates for repairs were in the $20 million range.

[54] Following the failure, Orbital sought to purchase launch services for its Cygnus spacecraft in order to satisfy its cargo contract with NASA,[24] 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.

One further mission was launched aboard an Atlas in April 2017 (Cygnus OA-7), fulfilling Orbital's contractual obligations towards NASA.