NASA mission to Mercury rising
CAPE CANAVERAL, Fla. -- NASA is about to embark on its hottest mission ever, to Mercury.
The Messenger spacecraft, scheduled to be launched next Monday, will be blasted by up to 840-degree heat as it orbits the tiny planet closest to the sun -- so close that it would be as though 11 suns were beating down on Earth.
Remarkably, the only thing between the probe's room-temperature science instruments and the blistering sun and pizza-oven heat will be a handmade ceramic-cloth quilt just a quarter-inch thick.
"If it doesn't stay toward the sun, it will fry everything," said Neal Bachtell, mechanical technician and master quilter.
Bachtell used X-Acto blades to cut the 3M Nextel fabric and then -- relying on sewing tips from his mother -- stitched the off-white pieces together into an 8-by-9-foot quilt, using Teflon-coated fiberglass thread and an industrial sewing machine. It was a nasty job; the itchy, ceramic-fiber cloth sheds and is bad to inhale.
"Neal, you're making history today, buddy," Jack Ercol, the project's lead thermal engineer, said during a mid-July spacecraft showing in an ultraclean room.
"It's cool, it's cool," Bachtell replied.
Messenger will be the first spacecraft to orbit Mercury and the first in more than 30 years to come close. Even at that, members of the Johns Hopkins University spacecraft team assembled in Cape Canaveral realize this mission cannot compete with Mars and its rovers, or Saturn and its newly arrived sentry, Cassini.
But there are plenty of cool facts about this red-hot mission, besides the off-the-charts-SPF sunscreen that was baked for days in ground testing.
You can see yourself in Messenger's twin solar wings, made up of a couple thousand little mirrors to reflect the intense sunlight in Mercury's neighborhood. The wings are two-thirds mirrors and one-third electricity-producing solar cells.
Diode heat pipes burrowed into the extraordinarily insulated spacecraft will radiate internal heat from all the electronics. When Messenger passes between the sun and Mercury and it gets really sweltering -- not too often and not for long because of Messenger's cleverly conceived flight plan -- these pipes will shut down and the boxy craft will be like a house with all the windows closed on a steamy afternoon.
"It's basically a thermos bottle," Ercol said.
"We're actually taking on a very brutal mission from the standpoint of the sun and then from the orbiting standpoint because the planet itself is very hot."
Although Mercury is 50 million miles from Earth at closest approach, Messenger will travel 5 billion miles to get there. It is technologically infeasible to fly straight to Mercury, a trip of a few months, and so the spacecraft must swing once past Earth, twice past Venus, and thrice past Mercury before slowing down enough to slip into orbit around Mercury.
Estimated arrival time: March 2011.
Mariner 10 was NASA's last Mercury lookout. Equipped with an umbrella for shade, it flew by Mercury three times in 1974 and 1975, providing the first up-close pictures of the planet. Messenger's photos will be far superior.
