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  NASA's Pioneer 10/11: Heat as source of slowing

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Author Topic:   NASA's Pioneer 10/11: Heat as source of slowing
moorouge
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Posts: 1490
From: U.K.
Registered: Jul 2009

posted 05-13-2013 08:09 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
I'm intrigued by an unexplained reference to the Pioneer 10 and 11 flights.

This reference says that when these spacecraft were about the same distance from the Sun as the planet Uranus they began to slow down faster than expected. After analysis of the data in 2011 it was thought that this was due to the heat generated by the two craft creating pressure effects.

Does anyone have a more detailed explanation how this happens? And was the same effect observed with the two Voyager missions?

Jim Behling
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Posts: 537
From: Cape Canaveral, FL
Registered: Mar 2010

posted 05-13-2013 08:10 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
The shape of the Pioneer spacecraft reflected/emitted more heat in one specific direction which led to a net propulsive force.

The effect is not seen on Voyager because the shape is different and the spacecraft were 3-axis stabilized which used thruster firings unlike Pioneer which was spin stabilized.

Look up Pioneer Anomaly or Effect.

Robert Pearlman
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Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 05-13-2013 08:14 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA's July 2012 release summarizing the findings, as published in the June 12 issue of Physical Review Letters, can be found here.
"The effect is something like when you're driving a car and the photons from your headlights are pushing you backward," said Slava Turyshev, the paper's lead author at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It is very subtle."

moorouge
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Posts: 1490
From: U.K.
Registered: Jul 2009

posted 05-13-2013 10:56 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
If the effect quoted is correct then, presumably it means that one gets better mpg during the day when the headlights are off than at night when they are on. An interesting thought, though one that won't save one much money!!

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