Using tools and techniques more often associated with fine tailoring than with space engineering, NASA technicians and engineers spent part of the holiday season laboring over sewing machines to clothe the Cassini spacecraft in the protective garb it must wear to survive during its long journey to Saturn.
At NASA's Jet Propulsion Laboratory in Pasadena, CA, a unique team of spacecraft shielding technicians are still cutting, stitching and fitting shiny gold-colored and black blankets onto the three-story-tall spacecraft in a clean room near the Laboratory's testing facilities. The work requires a unique combination of meticulous old-world skills and high-tech materials to produce the finely sewn, super-strong and extremely lightweight thermal blankets that will protect Cassini from the extreme hot and cold of deep space.
Though it appears to be gold foil covering the spacecraft, the shiny gold coloring of Cassini's blankets is due to the combination of a transparent layer of amber-colored material on top of a reflective aluminized fabric.
"Our blankets are built unlike any others," said Mark Duran, supervisor of the "shield shop" that provides the space survival gear for JPL's spacecraft and instruments. Using industrial sewing machines, brown butcher paper patterns and large cutting tables, Duran's team is working split shifts to finish the blankets in preparation for Cassini's move into JPL's thermal vacuum chamber next week. There, the finished spacecraft will be tested in an artificial space environment.
Spacecraft blankets are built for long-term durability and high thermal requirements. "Our goal in blanketing Cassini is to keep temperatures onboard the spacecraft at room temperature," said Pamela Hoffman, a thermal requirements engineer who is managing the blanketing of Cassini. In space, temperatures on the unblanketed portions of the spacecraft will range from about -220 to +250 degrees Celsius (about -364 to +482 degrees Fahrenheit).
All the fabrics used in the blankets must stand up to the extreme radiation environment of space and protect the spacecraft for the duration of Cassini's 11-year mission. The blankets also provide protection against micrometeoroids -- the dust grains of rocky debris that litter space. Some of Cassini's blankets are sewn with layers of a canvas-like, carbon-coated fabric called beta cloth that is especially effective in protecting against micrometeoroids.
For Cassini, the blankets consist of as many as 24 layers of different fabrics, including aluminized Kapton, mylar, Dacron and other special materials.
The blankets also have to meet tough electrical standards. At both Earth and Saturn, Cassini will be traveling through environments full of charged particles that could cause an electrical arc to form across the blankets, Duran said, "so a lot of work goes into making sure every single layer of each blanket is electrically grounded." Thin, accordion-like strips of aluminum are carefully sewn in to each blanket to prevent electrical arcing.
Cassini, the most sophisticated planetary spacecraft ever built, is scheduled to be launched October 6, 1997, on a Titan IV-Centaur rocket from Cape Canaveral, FL. Its voyage to Saturn will take nearly seven years. The spacecraft will fly a trajectory that brings it twice around Venus, once past Earth and once past Jupiter. These "swingby" maneuvers of other planets will give Cassini the speed it needs to reach Saturn, more than a billion kilometers away.
Once it reaches Saturn on July 1, 2004, Cassini will enter orbit and study the planet, its rings and moons for four years. It will also release a probe to parachute a payload of scientific instruments through the atmosphere and to the surface of Titan, Saturn's largest moon. Titan is believed to have large lakes of liquid ethane on its surface. Chemical reactions in the atmosphere create a variety of organic molecules that rain to the surface below. The Titan probe, called Huygens, is provided by the European Space Agency.
More information on the Cassini mission is available on its Internet home page at:
http://www.jpl.nasa.gov/cassini
The Cassini mission is a joint project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Office of Space Science, Washington, DC.
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