Cygnus is an expendable American automated cargo spacecraft designed for International Space Station (ISS) resupply missions.

In early 2006, the agency started its Commercial Orbital Transportation Services (COTS) program, where it would help fund the development of cargo spacecraft after a competitive process.

[8] To propel Cygnus into space, Orbital developed the Antares rocket, which also leveraged lower-cost, off-the-shelf parts and designs.

Construction and design of the first stage was subcontracted to Ukrainian companies and used refurbished NK-33 engines, remnants of the Soviet N1 moon rocket.

[9][10] The Antares made its maiden flight lifting a payload mass simulator to low Earth orbit on April 21, 2013.

On September 18, 2013, Antares successfully launched a Cygnus spacecraft on a flight test to rendezvous with the International Space Station.

[11] On 12 January 2014, the first scheduled Cygnus resupply mission arrived at the space station; the capsule carried Christmas presents and fresh fruit for the astronauts.

Its arrival was delayed, first by the need to repair the station, and then by frigid weather at the launch site and solar flares that forced postponements.

The SM was based on prior products developed by Orbital including the GEOStar and LEOStar (collectively known as Star Bus) satellite buses and the Dawn spacecraft.

[24][25] On 5 June 2020, NASA awarded Northrop Grumman Innovation Systems a $187 million contract to complete the preliminary design of HALO.

NASA will sign a separate contract with Northrop for the fabrication of the HALO, and for integration with the Power and Propulsion Element (PPE), being built by Maxar.