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#41
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Ralph Hertle wrote:
If no other gravitational flux would attract the spacecraft could Voyager return and be captured by the Sun? No; it's travelling at more than escape velocity. The further out it gets, the less the deceleration it will experience. -- Odysseus |
#42
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In article ,
Starry-Nite wrote: [Operating missions have been shut down in the past due to a perceived lack of return for additional expense - Viking, for instance.] No, while Viking Lander 1 was *threatened* with shutdown for financial reasons, it didn't actually happen. (It might have eventually, but the immediate threat was averted, and the lander died -- due to a mistaken command sequence -- before the problem could return.) Both the Viking Orbiters were shut down because they were about to run out of attitude-control fuel, and the loss of the last orbiter effectively killed Viking Lander 2, which was no longer able to talk to the ground directly. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#43
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In article ,
Ralph Hertle wrote: The Sun is pulling on the Voyager spacecraft and slowing it down. Almost too obvious eh? ... If no other gravitational flux would attract the spacecraft could Voyager return and be captured by the Sun? No. It has more than enough energy to escape entirely. The Sun will continue slowing it slightly (in principle, forever), but the rate of slowing -- speaking sloppily -- is dwindling more rapidly than the speed itself, so the speed will never reach zero. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#44
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In message , Louis Scheffer
writes Tim Auton tim.auton@uton.[groupSexWithoutTheY] writes: (Abdul Ahad) wrote: when I noted the velocities of both probes (relative to the Sun) were edging lower by small amounts over the past 8 years: Any ideas as to what's causing this slow down anyone? Gravity. Well, as accurately as we can measure the deceleration is all due to gravity, but data from the Pioneer craft suggest there may be something else (too small to measure for the Voyager craft due to the way they are stabilised). Search for "pioneer anomaly". It's very interesting, mainly because nobody seems to know what's causing it. This is just wishful thinking by the theorists, who want something new to explain. A careful look at Pioneer shows there are a number of features that cause it to radiate a bit more of its heat in the anti-sunward direction. This is just right to account for the observed slowdown. Conventional Forces can Explain the Anomalous Acceleration of Pioneer 10, Phys.Rev. D67 (2003) 084021. http://arxiv.org/abs/gr-qc/0107092 I'm the author so my opinion may be somewhat biased, of course. Note that when they put Cassini into a gyro-only mode for the gravity wave searches, it experienced an anomalous acceleration about 3x that of Pioneer, due to non-isotropic waste heat radiation. This effect is difficult to model, and the pre-launch estimates were off by 50%. But the theorists then do a song and dance about how this can't apply to Pioneer, all engineering data to the contrary. Interesting! Do you have a reference for that? (I could search, of course) My reading of the solar conjunction relativity experiment was that they _didn't_ find an anomaly, because they had modelled the heat output correctly. -- What have they got to hide? Release the Beagle 2 report. Remove spam and invalid from address to reply. |
#45
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On Thu, 24 Jun 2004 02:39:07 GMT, Ralph Hertle wrote:
Christopher: Christopher M. Jones wrote: [snip] Easy question with an easy answer, it's gravity. The Sun is pulling on the Voyager spacecraft and slowing it down. Almost too obvious eh? This is the way orbits work, if you have an exactly circular orbit then it just so happens that you balance out the falling / moving parts and the speed can stay constant. Otherwise speed will increase when falling into the Sun and decrease when heading away from the Sun, sans propulsive accelerations in the mix. If no other gravitational flux would attract the spacecraft could Voyager return and be captured by the Sun? There are two Voyager spacecraft. Both are moving at better than three times escape velocity at their distance - they will never return to the sun. Could it become a comet? A man-made metal spacecraft cannot become a comet. What kind of question is that? -- - Mike Remove 'spambegone.net' and reverse to send e-mail. |
#46
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Jonathan Silverlight writes:
In message , Louis Scheffer writes Note that when they put Cassini into a gyro-only mode for the gravity wave searches, it experienced an anomalous acceleration about 3x that of Pioneer, due to non-isotropic waste heat radiation. This effect is difficult to model, and the pre-launch estimates were off by 50%. But the theorists then do a song and dance about how this can't apply to Pioneer, all engineering data to the contrary. Interesting! Do you have a reference for that? (I could search, of course) My reading of the solar conjunction relativity experiment was that they _didn't_ find an anomaly, because they had modelled the heat output correctly. I'm working from memory here, but my recollection is that they knew there was non-isotropic heat rejection, so they added a constant force for this and fit it using trajectory data. They got a good fit, but the value of the radiation forces was different than their pre-launch estimates. Lou Scheffer |
#47
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Ralph Hertle wrote in message ...
If no other gravitational flux would attract the spacecraft could Voyager return and be captured by the Sun? Could it become a comet? Ditto! I fully accept the gravity attribution to the observed slow down (a=-GM/r^2 doesn't equal zero until 'r' reaches infinity), but you'd hope the rate of deceleration would drop off at a faster rate with distance. My *slight* concern was we saw a 2% reduction in the speed of V2 in the space of just 8 years (from 16.1 km/s down to 15.7 km/s). At this rate, if it were maintained, in just over a couple of centuries from now the craft's speed would fall away to complete insignificance and it will head back on a cometary path toward the sun! But the counter argument to this is V1 is already 25% more distant than V2... and it shows a less steeper drop off in its velocity, fitting the theoretical curve rather nicely. Interesting to watch the numbers and ponder! Abdul Ahad Ralph Hertle BTW, what's the reason for all the X-posting? |
#48
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Louis Scheffer writes:
Jonathan Silverlight writes: In message , Louis Scheffer writes Note that when they put Cassini into a gyro-only mode for the gravity wave searches, it experienced an anomalous acceleration about 3x that of Pioneer, due to non-isotropic waste heat radiation. This effect is difficult to model, and the pre-launch estimates were off by 50%. But the theorists then do a song and dance about how this can't apply to Pioneer, all engineering data to the contrary. Interesting! Do you have a reference for that? (I could search, of course) My reading of the solar conjunction relativity experiment was that they _didn't_ find an anomaly, because they had modelled the heat output correctly. I'm working from memory here, but my recollection is that they knew there was non-isotropic heat rejection, so they added a constant force for this and fit it using trajectory data. They got a good fit, but the value of the radiation forces was different than their pre-launch estimates. Found it! It's http://arxiv.org/abs/gr-qc/0308010 Note that the paper has been withdrawn, but thanks to the magic of arXiv the original version 1 is still available. Lou Scheffer |
#49
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"Mike Hawk" wrote ...
IIRC that article didn't dispute that Voyagers and Pioneers weren't slowing down due to gravity, but that their rate of deceleration was greater than expected. Here's part of the article http://tinyurl.com/2jpnz WELL? DUHHH???...something else is at work on these poor little intersteller MOFO's from Earth Congratulations on extracting the first (IIRC) public *PLONK* from me. |
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