|Aug. 20th, 2004 06:26 pm Stunt Pilots are gonna catch some Sun :)|
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"Stunt pilots to hook falling stardust sample
12:00 20 August 04
NewScientist.com news service
A piece of the Sun is set to fall to Earth and be captured by Hollywood stunt pilots in a tricky mid-air manoeuvre, NASA announced on Thursday.
A capsule filled with stardust will be dropped into the atmosphere from NASA's Genesis spacecraft on 8 September.
Genesis has collected charged particles from the Sun's outermost layer for about 27 months since its launch in 2001. Scientists believe its quarry will reveal the chemical composition of the cloud from which the Sun and planets condensed 4.5 billion years ago.
"We believe the solar nebula was a fairly homogeneous environment, but out of this all the diverse materials of planets formed," says Don Burnett of the California Institute of Technology, and principal investigator.
He hopes to track the Solar System's evolution by comparing the chemical makeup of meteorites to the original solar nebula.
The first science results may come in the spring of 2005, but the project hinges on getting the precious cargo - equivalent to the mass of a few grains of salt - back to Earth safely.
So NASA hired two professional helicopter stunt pilots to capture the 190-kilogramme sample return capsule as it parachutes into the sky above the US Air Force's Utah Test and Training Range southwest of Salt Lake City, Utah.
Radar and GPS
At 1253 BST on 8 September, the Genesis spacecraft, which will be hovering above the Earth's atmosphere, will release its sample return capsule. About four hours later, the capsule will hurtle into the atmosphere at 11 kilometres per second.
Two minutes after entering the atmosphere, it will fire a mortar to release its first parachute. This will then be jettisoned from the capsule, pulling out the main chute, called a parafoil, in the process.
The parafoil will slow the capsule to a leisurely 4 metres per second, and the capsule will drift for about 10 minutes before reaching an altitude of 3000 metres.
At that height, the pilots and their two-person crews will be hovering, having earlier received radar and GPS data on the capsule's whereabouts. They will fly in formation behind the parafoil, watching how it moves, before one of them overtakes it, staying just 2.5 metres above the chute.
At an altitude of 2750 m, the lead crew will try to snag the chute's fabric with a hooked pole 5.6 metres long. If successful, the capsule's weight will trigger a piston that secures the parafoil to the hook, and the pilot will pitch the helicopter's nose upward to prevent the parafoil from reinflating.
If that attempt fails, the pilots have five more chances until they reach a height of 150 m, at which point they will have to give up, leaving the capsule's fate up to the type of surface it lands on.
But even if the hook is successful, the pilots will still be under pressure. Within two hours of capture, scientists want to flush out any gas that might have entered the capsule during its atmospheric entry.
So the pilots will have to set the helicopters down gently and quickly strip off the parafoil so they can fly unhindered to an army air field several kilometres away. That is where scientists will be able to use nitrogen to purge the capsule of any contaminating gas.
"As soon as we get the purge on, I'll be very happy," Burnett said.
Pilot Dan Rudert, who flies stunts in movies but also does "bucket drops" above fires, says he expects the mission to go smoothly, having done more than 10 successful practice runs.
But he says the mission will be difficult, citing the lack of visual cues such as trees and houses at the hover height of 3000 metres.
Roy Haggard, the helicopter operations chief, agrees, saying most helicopter pilots never fly above 300 metres.