Cygnus is an expendable American cargo spacecraft developed by Orbital Sciences Corporation but manufactured and launched by Northrop Grumman Space Systems as part of NASA's Commercial Resupply Services (CRS) program. It is usually launched by Northrop Grumman's Antares rocket from the Wallops Flight Facility, although three flights were on ULA's Atlas V and three are planned for SpaceX's Falcon 9, in both cases launching from Cape Canaveral Space Force Station. It transports supplies to the International Space Station (ISS) following the retirement of the American Space Shuttle. Since August 2000, ISS resupply missions have been regularly flown by the Russian Progress spacecraft, as well as by the European Automated Transfer Vehicle, and the Japanese H-II Transfer Vehicle. With the Cygnus spacecraft and the SpaceX Dragon, NASA seeks to increase its partnerships with domestic commercial aviation and aeronautics industry.^[2]

Quick Facts Manufacturer, Country of origin ...

Cygnus

Cygnus spacecraft approaching the International Space Station for the NG-12 mission
Manufacturer	Northrop Grumman
Country of origin	United States
Operator	Northrop Grumman
Applications	ISS resupply
Specifications
Spacecraft type	Uncrewed cargo vehicle
Launch mass	6,600 kg
Dry mass	3,400 kg
Payload capacity	3,000 kg
Volume	18.9 m3
Power	3.5 kW
Design life	1 week to 2 years [1]
Dimensions
Length	5.1 m
Diameter	3.07 m
Production
Status	In service
On order	5
Built	21
Launched	20
Operational	1
Retired	18
Lost	1
Maiden launch	18 September 2013
Last launch	30 January 2024

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Cygnus is the Latinized Greek word for swan and a northern constellation.

With Rocketplane Kistler unable to meet funding obligations for its K-1 launch vehicle under the terms of the COTS agreement, NASA decided on 18 October 2007 to terminate its contract with Rocketplane Kistler and re-award its contract after a competition.^[3] On 19 February 2008, NASA announced that it had chosen Orbital Sciences as the new winner.^[4] On 23 December 2008, NASA awarded Orbital Sciences a $1.9 billion contract under the Commercial Resupply Services (CRS) program. Under this contract, Orbital Sciences agreed to deliver up to 20 tons of cargo to the ISS through 2016 in eight Cygnus spacecraft flights.^[2]

By April 2010, Orbital had displayed a full-scale model of the Cygnus cargo delivery spacecraft at the National Space Symposium (NSS) in Colorado Springs, CO.^[5]

Launched on an Antares (renamed from Taurus II) medium-class launch vehicle or Atlas V, the first Cygnus flight was originally planned to occur in December 2010.^[6]·^[7] The Cygnus demonstration mission was successfully launched on 18 September 2013.^[8] 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.^[8]·^[9]

With the December 2015 launch of Orb CRS-4 on Atlas V, the enhanced version of Cygnus made its debut. While it was planned from the beginning to fly on the fifth mission, the Orb CRS-3 failure and subsequent move to Atlas V meant a delay. However, lessons learned on packing and the extra capabilities of the Atlas allowed payload to be increased to 3,500 kg (7,700 lb).^[10]

The Cygnus spacecraft consists of two basic components: the Pressurized Cargo Module (PCM) and the Service Module (SM). The PCM is manufactured by Thales Alenia Space in Turin, (Italy). The first PCMs had an empty mass of 1,500 kg (3,300 lb) ^[11] and a volume of 18 m³ (640 cu ft).^[12] The service module is built by Orbital ATK and is based on their GEOStar and LEOStar spacecraft buses as well as components from the development of the Dawn spacecraft. It has a gross mass of 1,800 kg (4,000 lb) with propulsion provided by 32 monopropellant thrusters for attitude control. The SM also carries one BT-4 main engine ^[13] burning hypergolic propellants hydrazine and nitrogen tetroxide (the propellant mass is 800 kg (1,800 lb) ^[14][15]). The service module is capable of producing up to 4 kW of electrical power via two gallium arsenide solar arrays.^[12] On 12 November 2009, Dutch Space announced it would provide the solar arrays for the first Cygnus spacecraft.^[16]

The fourth and all subsequent Cygnus spacecraft are the "Enhanced" variant, as the standard version has been retired.^[17] These have a stretched 1,800 kg (4,000 lb) empty weight PCM with interior volume increased by 50% to 27 m³ (950 cu ft) and the service module uses Orbital ATK Ultraflex solar arrays providing the same power as the previous arrays at a lower mass.^[12]·^[17] A new upper stage built by Orbital ATK, the Castor 30XL, is used together with the enhanced Cygnus. With a more powerful upper stage and lighter solar arrays, the Cygnus payload delivered to the ISS can be increased by 700 kg (1,500 lb).^[18]

During nominal CRS missions, Cygnus maneuvers close to the International Space Station, where the Canadarm2 robotic arm grapples the spacecraft and berths it to a Common Berthing Mechanism on the Harmony module in a similar fashion to the Japanese H-II Transfer Vehicle and the retired SpaceX Dragon,^[12] but not the other active American CRS Dragon 2 vehicle, which docks autonomously. For typical missions, Cygnus remains berthed for about 30 days.^[19]·^[20] Unlike Dragon 2 and the earlier Dragon, Cygnus does not provide cargo return capability. However, it can be loaded with obsolete equipment and trash for destructive reentry like the Russian Progress vehicles.^[21]

An earlier proposed version of Cygnus would have replaced the PCM with the Unpressurized Cargo Module (UCM), based on NASA's ExPRESS Logistics Carrier, and would have been used to transport unpressurized cargo, such as ISS Orbital Replacement Units.^[6]·^[22] Another proposed variant would have replaced the PCM with the Return Cargo Module (RCM), which would have allowed Cygnus to return cargo to Earth.^[6]·

In August 2023, Northrop Grumman announced a further enlarged Mission B version of Cygnus, with a 1.5 m (4.9 ft) stretch to the payload module and payload mass increased to 5,000 kg (11,000 lb). This version is expected to enter service with the NG-23 mission in 2025 (the first to use the new Antares 330 launch vehicle).^[23]

List includes only missions that have flown and six planned missions. As of January 2024^[update] two missions are currently planned to be launched on the Falcon 9 rocket from SLC-40, and three from Wallops on an Antares 330. Cygnus is the only cargo freighter to launch on four different orbital launchers, that is, Antares 100 series, Atlas V, Antares 200 series and Falcon 9 Block 5 rockets.^[28]

Each mission is named for a notable member of the Human spaceflight community, often but not exclusively former NASA astronauts.

In March 2022, NASA ordered six additional flights, Cygnus NG-20 to NG-25, to resupply the ISS through 2026.^[75]

• Space Shuttle retirement
• Comparison of space station cargo vehicles
• cygnus.com