Lockheed Martin Missiles and Fire Control
– Dallas’ Photovoltaic Radiators (PVR) are scheduled to be launched on the
Space Shuttle Endeavor on November 30 as part of the next International Space
Station assembly mission.

Under clear conditions, the deployed radiators will be one of the most
visible parts of the International Space Station (ISS), easily seen from the
ground with the naked eye.
The three PVRs were designed and manufactured at
the Lockheed Martin Missiles and Fire Control plant in Grand Prairie, Texas.

The PVRs are designed to get rid of excess heat produced by the solar cell
batteries, which provide electrical power for the ISS and the early habitation
The PVRs work like the radiator in a car, with liquid ammonia used
as the coolant.
Excess heat is taken from the batteries and a heat exchanger,
and moved to the PVR panels.
The ammonia enters the PVR panels on one side
and is distributed to small diameter tubes across each of seven flat panels.
As the fluid flows through each panel, heat is radiated into space, cooling
the fluid.

Initially, two of the three PVRs will be used to help cool the habitation
module and remove excess heat from early science experiments on the ISS.
These two units will eventually be moved to their final locations on solar
array segments as the ISS is expanded.
The third PVR is located on the solar
power module and will be used entirely to reject the excess heat from the
solar cell batteries.
The fourth and final PVR is scheduled for launch in
April 2003.

“In the environment of space, although it is very cold, heat can be a
major problem,” said Dave Williams, director – Space Programs for Lockheed
Martin Missiles and Fire Control – Dallas.
“Without these radiators, the
equipment would likely overheat in short order, and the Space
Station capabilities would be significantly diminished.”

Their large size made testing of the PVRs especially challenging to
engineers at Lockheed Martin Missiles and Fire Control – Dallas.
To verify
the PVR deployment mechanism in the extreme environments of space, tests in
the world’s largest thermal vacuum chamber were performed.
NASA’s Plum Brook
facility in Sandusky, Ohio, provided the facilities to test the Radiators’
mechanism across the -120 to +120 degrees Fahrenheit temperature range and
hard vacuum conditions expected on orbit.
The PVR panels are designed to
tolerate ammonia freezing when the surroundings are very cold.

In addition to the PVRs, Lockheed Martin Missiles and Fire Control –
Dallas has fabricated six Heat Rejection System (HRS) radiators which will
cool science equipment and the habitation modules.
These HRS radiators are
scheduled for launch and installation on the ISS at a later date.
the PV and HRS radiators will have a deployed area of approximately 6,500
square feet and weigh approximately 10 tons.
These large, mostly brilliant
white radiator panels will contribute significantly to the Venus-like
brightness of the completed ISS, which will be visible to over 95 percent of
Earth’s population.

The ISS radiators continue a long heritage of space-related activities for
Missiles and Fire Control – Dallas that date back to the beginning of the U.S.
space program in the late 1950s.
Except for Gemini and Skylab, most heat
rejection radiators for manned space flight were developed under the Space
Programs directorate within what is now Lockheed Martin Missiles and Fire
Control – Dallas.
For the Space Shuttle program, the company invented and
produced the reinforced carbon-carbon nose cap, chin panel and wing leading
edges, as well as the Space Shuttle radiators.

Located in Dallas, Tex.; Orlando, Fla.; and Sunnyvale, Calif., Lockheed
Martin Missiles and Fire Control develops, manufactures and supports advanced
combat, missile, rocket and space systems.
The company is organized in seven
program/mission areas:
Strike Weapons, Air Defense, Anti-Armor, Naval
Munitions, Fire Control and Sensors, Fire Support and Product Development.

Headquartered in Bethesda, Maryland, Lockheed Martin is a
global enterprise principally engaged in the research, design, development,
manufacture and integration of advanced-technology systems, products and
The Corporation’s core businesses are systems integration, space,
aeronautics, and technology services.

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