Pioneer 10 & 11 Gravity Discrepancies

[ajna]

Does anyone have any idea as to why doppler measurements have shown that both of the Pioneer spacecraft are out by 240,000 miles due to gravity discrepancies? I've posted the news link below. They seem to be fully supporting Newton's idea of gravity, but who's to say that Einstein's time factor isn't at play? What if, at 92 AU from the sun, time flows differently? This would mean that the Oort cloud orbital data would also be off. It is after all in a very weak gravity well at that distance...<br /><br />Link: http://news.yahoo.com/s/space/20070327/sc_space/newfounddatacouldsolvenasasgreatgravitymystery

 

[docm]

As the article states current thought is that ~55%-75% of the discrepancy is from infrared coming off the RTG power cells hitting the dish antenna turning it into an "RTG Sail", displacing them relative to predicted positions. <br /><br />Modified Newtonian gravity is a possibility for the remainder, but all else has to be looked at before that should be considered. <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

Great! The first nuclear propulsion system in service!

 

[scottb50]

Newtonian gravity seems to be well established. Distant Galaxies seem to operate pretty much the same, gravity wise.<br /><br />If nothing else we will know not to aim an ion engine at an antenna again. Maybe there's more mass then we think there is in the Solar systems, random atom collisions would have the same effect. The last of the debris from the Suns beginning. <div class="Discussion_UserSignature"> </div>

 

[ajna]

gunsandrockets you are truly deep. I reckon this is the next step, using dimensionality and time to move around. Who needs solar sails when time changes can do the trick.. maybe... HOPEFULLY, we will see some of its effects in this data, but I know that design is a major part of the discrepancy.

 

[shyningnight]

There's something here I'm not getting...<br /><br />Wouldn't thrust from IR or particles from the RTG hitting the antenna be analogous to "bootstrap levitiation" (being able to levitate by pulling up on your shoelaces read hard)?<br /><br />I must be misunderstanding something, or the laws of physics have changed recently.<br /><br />Paul F.

 

[scottb50]

The RTG is a power generator not a ion engine....<br /><br />Not in the strict sense of expelling high energy mass. By giving off heat they expell infrared energy that provides a minimal but constant thrust. If the heat could be used to ionize particles it would be a lot more efficient as an engine. <div class="Discussion_UserSignature"> </div>

 

[trailrider]

Warp factor 3, Mr. Sulu! Engage! <img src="/images/icons/smile.gif" />

 

[henryhallam]

<font color="yellow">There's something here I'm not getting... <br /><br />Wouldn't thrust from IR or particles from the RTG hitting the antenna be analogous to "bootstrap levitiation" (being able to levitate by pulling up on your shoelaces read hard)? <br /><br />I must be misunderstanding something, or the laws of physics have changed recently. </font><br /><br />Draw a "control volume" (i.e. a box) around the whole spacecraft and consider what crosses the boundary of that volume.<br />If there were no antenna, the infrared photons from the RTG would exit roughly uniformly with no directional bias and there would be no thrust. With the antenna, some of the photons bounce off the antenna and go back mostly the way they came, so there is an asymmetry and more IR exits on one face of the box than the opposite face. Therefore there is a net thrust.

 

[spacester]

The Control Volume: One of the most powerful analytical tools ever invented.<br /><br />Nice post, henryhallam! <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

I was just about to say the same. I was having problems "seeing" about why it would cause problems and as soon as he stated the control volume and open systems it all made sense.

 

[shyningnight]

MUCH clearer!<br />Thank you...<br /><br />I was assuming that they were trying to draw the picture of the antenna being a "sail", and the RTG being a "fan" blowing on it.<br /><br />The "thrust" escaping asymetrically makes much more sense.<br /><br />Paul F.

 

[rocketman5000]

It works in laymans terms. Technically you could have fans blowing on a sail to move you forward. but it would be much more efficient to either turn the fans around or stick them in the water and use them as screws

 

[ajna]

This all sounds good as an explanation in principle but it doesn't fit with the information from the article. <br /><br />Firstly John Anderson of JPL said “We had a fitting model and it had all the effects in it that would influence the spacecraft out in interstellar space, except that it didn’t work. And all we had to do to make it work was to add a constant acceleration towards the Sun.” This would mean that for the antenna-sail theory to work the antenna would always have to be pointing ahead of the two spacecraft instead of towards Earth. Besides the antenna would be shot with space debris.<br /><br />We have never been in such an area of space before, the whole EM, gravity (and therefore time) environment there has never been tested or directly observed. Physics is starting to show that all forces and energy are interdimensional, so this data might be reflecting the effects of this that we haven't considered before. What's it like at 92AU? No true scientists could say that we know from physics, because it has yet to be tested.<br /><br />I'll put my neck on the line by hypothesising that because the time-frame at 92AU is faster than that nearer the sun, the probe would have to slow its kinetic energy to compensate and to conserve energy. In this case I believe it might be conservation of the objects whole interdimensional energy. We know from both theories of relativity that gravity, speed and time are interlinked. Maybe this data is giving us an example of this in the same way the orbit of Mercury did?