On 19 February 2008 Orbital Sciences Corporation (NYSE: ORB) announced that it had been selected by the National Aeronautics and Space Administration (NASA) to demonstrate a new space transportation system for delivering cargo to the International Space Station (ISS). In a three-year, $320 million cooperative program, NASA will invest $170 million and Orbital will contribute $150 million (including its planned Taurus II launch vehicle development investment) in the Commercial Orbital Transportation Services (COTS) project.
In its first phase, the COTS project involved the development and flight demonstration of a commercial cargo delivery system to low Earth orbit with the potential to support ISS operations following the retirement of the Space Shuttle in 2010. This system consists of a new advanced maneuvering spacecraft called CygnusT, along with several interchangeable modules for pressurized and unpressurized cargo, and will be launched on Orbital's new Taurus II [later renamed Antares] medium-lift rocket.
The COTS project is strategically important to both NASA and Orbital," said Mr. David W. Thompson, Orbital's Chairman and Chief Executive Officer. "For NASA, the ability to deliver cargo to the International Space Station with reasonably priced commercial services is part of its long-term plan to rely on American industry for routine Earth-orbit operations, as the space agency focuses on returning astronauts to the Moon and beyond. For Orbital, the COTS project is a critical element of the company's strategy to play an expanded role in human spaceflight programs, including ISS operations and the development and support of NASA's Orion program."
Orbital's COTS demonstration mission was initially scheduled to take place in the fourth quarter of 2010. Subject to NASA's future requirements, Orbital would be prepared to carry out several follow-on operational COTS missions in 2011 and to conduct as many as eight operational ISS cargo flights a year by 2012 and 2013. The Cygnus spacecraft to be launched aboard the Taurus II rocket would be capable of delivering up to 2,300 kg of cargo to the ISS and will be able to return 1,200 kg of cargo from the ISS to Earth.
The COTS project provides NASA with a U.S.-produced and -operated automated cargo delivery service for ISS support, to complement Russian, European and Japanese cargo vehicles. In addition, the COTS project will help facilitate the introduction of Taurus II, a new medium-class launch vehicle that can be used by NASA and other government agencies and private-sector satellite operators for a variety of scientific, national defense and commercial space missions.
Orbital planned to carry out the development, production and integration of the Cygnus spacecraft and cargo modules at company facilities in Dulles, Virginia and Greenbelt, Maryland. The company's design, manufacturing and testing activities related to the Taurus II rocket will be done in Dulles and Chandler, Arizona. Early COTS missions are planned to be launched from NASA's Wallops Flight Facility on Virginia's Eastern Shore, with integrated mission operations conducted from control centers in Dulles and Houston, Texas.
Developed by Thales Alenia of Turin, Italy, the Pressurized Cargo Module [PCM] shares its heritage with numerous space station modules, including the Multipurpose Logistics Module, the Autonomous Transfer Vehicle, and Nodes 2 and 3. The Cargo Module is designed with two configurations. The standard configuration carries up to 4,409 lbs. (2,000 kg) of cargo while the enhanced variant will carry up to 5,952 lbs. (2,700 kg).
Service Module propulsion consists of dual-mode N2H4/MON-3 or N2H4, IHI Delta V engine generating 100 pounds of force (thrust), and 32 Rocket Engine Assemblies (REAs) which provide 6 pounds of force (thrust), each. Power is provided by two solar array wings on the service module, six panels total, generating 3.5 ilowatts of power.
Communication between Cygnus and the ISS is provided by the Japan Aerospace Exploration Agency’s (JAXA) proximity communications (PROX) system. The space station crew commands Cygnus using the Hardware Control Panel. Cygnus can also communicate on S-band via either the Tracking and Data Relay Satellite System (TDRSS) or ground stations.
Astronauts will enter Cygnus to remove cargo. Cygnus provides a habitable cabin with air circulation, fire detection, lighting, pressure and temperature monitoring.
Cygnus meets NASA’s high standards for human-rating to permit rendezvous and berthing to the space station. Cygnus successfully completed NASA’s 3 Phase safety certification program, proving that Orbital-engineered designs will ensure safe and successful missions for NASA and its crews. In addition, Cygnus met all 425 requirements necessary to approach and berth with the space station, imposed by the station to Visiting Vehicle Office specifications.
The Cygnus Service Module includes a Power Video Grapple Fixture (PVGF) developed by MacDonald, Dettwiler and Associates, providing a mechanical and electrical interface between Cygnus and the Space Station Robotic Arm (SSRMS). The PVGF allows Cygnus to obtain 120V power from the SSRMS once captured, reducing the time sensitivity of berthing Cygnus after it is grappled by the robotic arm.
The Avionics System provides a two fault tolerance for all critical computational and commanding systems, ensuring that Cygnus will safely and successfully complete its resupply mission to the space station. Cygnus includes a four computer real time voting architecture that is designed to continually monitor the health of the spacecraft and react to anomalies while still maintaining the stringent safety requirements imposed on Cygnus by NASA.
Guidance and Navigation systems include specialized sensors and software to provide guidance from Antares separation to the capture location 12 meters below the ISS. The navigation sensors include redundant Space Integrated Global Positioning System/Inertial Navigation System (SIGI) and redundant LIDARs to provide far and near field rendezvous guidance, respectively. SIGI and LIDAR have extensive flight heritage, increasing the chances for mission success. Navigation software includes Orbital proprietary software and software provided from Draper Laboratory, the company responsible for successfully guiding the Apollo capsule to the moon and return, and providing rendezvous software for the space shuttle.
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