The Mir Solar Array Return Experiment was not the only U.S. effort to test technology for the then-upcoming International Space Station; the U.S. also contributed to a new solar array to feed the ever power-hungry Mir.
The array, known as the Mir Cooperative Solar Array, was made by installing U.S. solar cell technology, nearly identical to the cells that would go on the American solar arrays for the ISS, onto a Russian-made solar array frame. The array consisted of 84 U.S. solar cell modules installed onto 42 Russian frame assemblies on a single, long accordion-like frame. The array was to add 6 kW of power to Mir.
The MCSA was carried to Mir aboard Space Shuttle Atlantis on STS-74 in November 1995 and installed on the Kvant-1 module, pointing in the -z direction, or down toward Earth, in May 1996.
The schedule to design, build, and test MCSA was tight—less than two years. Mir was already ten years old by that time and U.S. astronauts needed more power for the experiments they were conducting aboard the station.
The MCSA project was managed from NASA-Lewis and employed a special technique developed by the Lewis Research Center to test the array after construction.
The flexible frame the U.S. solar cells were to be joined to was constructed by the Russian aerospace company RSC Energia. U.S. companies Lockheed Martin, the prime contractor, and Rocketdyne also worked on the arrays.
Before the arrays could be built on the full scale, it was important to make sure that the U.S. and Russian technologies involved would mesh. So, 2 Russian frame arrays were plated with the U.S. solar cells and sent to NASA-Lewis, where they were subject to an accelerated life-cycle test. They were exposed to temperatures ranging from 80 degrees C to -100 degrees C in 24,000 cycles, simulating 4 years in orbit, passing in and out of direct sunlight and Earth’s shadow.
As a result of the test, some small changes were made to the design of the array. But, in the end, 84 U.S. solar cell panels, originally designed for Space Station Freedom, were stitched (not glued, which was the Russian method of attaching solar cells to arrays) onto the Russian array frame.
The completed MCSA was shipped to Kennedy Space Center for final testing. NASA-Lewis used its expertise in space-based solar array technology to “dark test” the arrays—that is, they tested the ability of the arrays to generate power without having to deploy the arrays and fully illuminate them.
The array passed its dark testing and was ready for transport to Mir. Both the Cooperative Array and an All-Russian Array were attached to a Russian-made Docking Module for delivery to Mir.
The Docking Module was basically an extended docking tunnel that would attach to the APAS dock on Kristall, where the Shuttle usually docked. The structure of the new module would provide some clearance between the Shuttle and another of Mir’s solar arrays. The module also had an APAS docking mechanism on its bottom side, which would allow the Shuttle to dock to it just as it had docked to Kristall.
Space Shuttle Atlantis launched on STS-74 on November 12, 1995. It docked to Mir on November 15 in a maneuver that allowed it to dock the new Docking Module to Mir. The two solar arrays, the Cooperative Array and the All-Russian Array, were safely stowed on the exterior of the Docking Module.
And there they remained until May 1996, when two Russian cosmonauts, Yuri Ivanovich Onufrienko and Yuri Vladimirovich Usachyov, deployed the arrays on the -z port of the Kvant-1 module.
The MCSA delivered slightly less power to Mir than was desired, as the cable run from the end of the array back to the station itself caused some power to be lost to resistance, but the array still exceeded other expectations. NASA-Lewis used computer modeling to predict its performance across its lifespan, and the array’s actual performance was greater than predicted. NASA called for a 4.5% drop in efficiency each year, but the array only lost 3.7% per year, a good omen for the huge solar arrays already being constructed for the International Space Station.