page_title: Cygnus (spacecraft)
section_title: Design
hierarchical_section_title: Cygnus (spacecraft) / Design
caption_attribution_description: English: Standard Cygnus is shown on the left, enhanced Cygnus is shown on the right. Image drawn to scale. Details on the service module are not shown. Drawings based off [1], [2] and various pictures of hardware. Created in Gimp.
context_page_description: The Cygnus spacecraft is an expendable American cargo spacecraft developed by Orbital Sciences Corporation and now manufactured and launched by Northrop Grumman Innovation Systems as part of NASA's Commercial Resupply Services program. It is launched by Northrop Grumman's Antares rocket or ULA's Atlas V and is designed to transport supplies to the International Space Station 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.
  Cygnus is the Latinized Greek word for swan and a northern constellation.
context_section_description: 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 initial PCMs have an empty mass of 1,500 kg  and a volume of 18 m³·. 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 with propulsion provided by thrusters using the hypergolic propellants hydrazine and nitrogen tetroxide and is capable of producing up to 4 kW of electrical power via two gallium arsenide solar arrays. On 12 November 2009, Dutch Space announced it will provide the solar arrays for the initial Cygnus spacecraft.
  The fourth and all subsequent Cygnus spacecraft are planned to be of the "Enhanced" variant, as the standard variant has been retired. These will use a stretched 1,800-kilogram (empty weight) PCM which increases the interior volume to 27 m³ and the service module will use Orbital ATK Ultraflex solar arrays which will provide the same amount of power as the previous solar arrays but at a lower mass.· A new upper stage built by Orbital ATK, the Castor 30XL, will be used in conjunction with the enhanced Cygnus; because of the more powerful upper stage and the lighter solar arrays, the payload that Cygnus can deliver to the ISS will be increased by 700 kg.
  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 other American CRS vehicle, the SpaceX Dragon. For typical missions, Cygnus is planned to remain berthed for about 30 days.· Cygnus does not provide return capability, but can be loaded with obsolete equipment and trash for destructive reentry similar to the Russian Progress vehicles.
  A formerly planned variant 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.· Another proposed variant would have replaced the PCM with the Return Cargo Module (RCM), which would have allowed Cygnus to return cargo to Earth.·
caption: A scale drawing of the Standard (left) and Enhanced (right) Cygnus.
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