WASHINGTON — Orbital Sciences Corp.’s Cygnus space tug will head to the international space station (ISS) in September powered by a pair of rectangular solar arrays from Dutch Space, but by the time the tug makes its fifth flight to the orbital outpost, it will be sporting a distinctive pair of circular arrays ATK Aerospace developed for NASA’s Orion deep-space crew capsule.

Loosely scheduled for 2014 or 2015, Orbital’s fifth space station resupply mission coincides with the introduction of an enhanced version of Cygnus that can carry as much as 2,700 kilograms, up from the original 2,000 kilograms, according to Orbital spokesman Barron Beneski. 

That means Dutch Space arrays will power Cygnus for four missions, while ATK’s Goleta, Calif.-built arrays draw power duty for at least five missions. The first Cygnus cargo run, scheduled for September, is a demonstration flight Orbital must complete before it can begin the eight cargo runs it owes NASA under a $1.9 billion Commercial Resupply Services contract signed in 2008. The contract helped defray the costs of Cygnus and a new Orbital Sciences rocket called Antares that will launch the barrel-shaped spacecraft from the Wallops Island Flight Facility in Wallops Island, Va. 

ATK, as a subcontractor to spacecraft prime Lockheed Martin Space Systems of Denver, started working on Orion’s circular solar arrays in 2006, two years before NASA tapped Orbital to develop an ISS resupply vehicle. In 2009, Dutch Space, an EADS Astrium company based in Leiden, Netherlands, already buildings solar arrays for the Europe Space Agency’s Automated Transfer Vehicle, won a $35 million contract from Orbital to provide a 3.5-kilowatt solar array system for Cygnus. In 2011, Orbital replaced Dutch Space on the project and gave ATK’s space components division, which was already supplying the substrates for Dutch Space’s Orion solar panels, a $20 million deal to provide UltraFlex arrays for later Cygnus flights. 

Beneski said the circular UltraFlex arrays are smaller and lighter than the more conventional rectangular ones from Dutch Space, making them highly desirable for later Cygnus missions, which must haul heavier payloads.

The last Cygnus resupply flight in Orbital’s current contract with NASA would be in 2016, but the company could bid on a follow-on Commercial Resupply Services contract for which NASA is expected to seek bids in December or January. That would give ATK a shot to supply more Cygnus solar panels later this decade, which would make up for some of the work it has lost on Orion project.

ATK was set to provide panels for Orion’s 2017 flight to lunar space but got bumped from that mission after the European Space Agency (ESA) agreed to provide NASA with an Orion service module based on the Automated Transfer Vehicle ESA has used four times to send supplies to ISS. That spacecraft has always used Dutch Space solar arrays. In January, around the time NASA and ESA formalized the agreement to use a European service module, ESA said the module would inherit the Automated Transfer Vehicle’s X-shaped array of four rectangular solar panels. The panels, ESA said, will get “a significant upgrade,” making them shorter, wider and capable of generating about 11 kilowatts of power. The current Automated Transfer Vehicle uses a 4.6-kilowatt array, according to Dutch Space’s website. 

ATK has not been working on solar panels for Orion for close to two years, spokesman George Torres said. Lockheed stopped funding ATK’s Orion solar array subcontract in October 2011, well before ESA’s November 2012 decision to provide NASA with an Orion service module barter element covering its 8.3 percent share of future ISS operating costs.

“We’re still under contract, but there’s no funding,” Torres said.

The decision was made to suspend ATK’s solar array work after Lockheed and NASA decided that Orion would run on battery power when it launches unmanned aboard a United Launch Alliance Delta 4 rocket for a two-orbit mission — dubbed Exploration Flight Test 1 — to stress test the capsule’s avionics and heat shields.

Torres said ATK was fighting to stay in the running as an Orion solar array subcontractor for missions beyond Orion’s initial test flights.

Meanwhile, Europe’s current design for the Orion service module exceeds a NASA-defined mass threshold, the European Space Agency confirmed in a July 31 statement. 

“The dry mass requirement of the service module is about 4 tons [and] the best engineering judgment of the current design exceeds [that] by about 500 kilograms,” the statement said. “A dedicated working group has identified mass opportunities and threats [and] shall conclude its activity not later than the Preliminary Design Review,” which is scheduled for November. 

The statement said the overage “include[s] the usual system and equipment margins, which are slowly released between Preliminary Design Review and Critical Design Review.”

Passing a critical design review typically clears a development program to start building flight hardware.

Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...