Acceleration of voyager spacecraft

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Could the anomalous acceleration of the voyager spacecraft towards the sun be explained by its surface becoming electrically charged by friction with dust particles and the interaction of the electric charges with the sun's magnetic field?
 
I mean pioneer.And how do we know that the acceleration isn't due
to the sun having an uneven mass distribution or a large mass moving close to pioneer? And is the signal pioneer sends faulty after all this time?
 
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LURCH

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We can be pretty sure that it isn't due to something moving close to Pioneer because the effect was evidenced in both Pioneer 10 and 11 (which are nowhere near one another), as well as Galileo and Cassini.
 
Thanks for the clarification, battery - so we are actually all thinking about the same spacecraft.

Now I have already been in error with my statements so often, so don't take what I say now too seriously. But anyway: I don't think that interaction of a (possible) electrical charge of the spacecraft with the solar magnetic field might be the cause. A charged body moving through a magnetic field would be accelerated perpendicular to its velocity vector. But this spacecraft is moving away from the sun, and the strange extra acceleration is pointing towards the sun (right ?), so its in fact antiparalel to the velocity vector .
 
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Chronos

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Perpendicular wrt its velocity vector is confusing. Clarify your point. The pioneer anomaly has nothing to do with solar effects, so far as I know.
 
Thanks for the clarification, battery - so we are actually all thinking about the same spacecraft.

Now I have already been in error with my statements so often, so don't take what I say now too seriously. But anyway: I don't think that interaction of a (possible) electrical charge of the spacecraft with the solar magnetic field might be the cause. A charged body moving through a magnetic field would be accelerated perpendicular to its velocity vector. But this spacecraft is moving away from the sun, and the strange extra acceleration is pointing towards the sun (right ?), so its in fact antiparalel to the velocity vector .
The pioneer craft would have to be moving at exactly 90 degrees to the sun's surface to have a zero acceleration towards or away from it.This angle is unlikely and if there is some charge on pioneer then there will be a small force acting on pioneer.Also there are electric charges in the space around the sun that could attach themselves to pioneer.The question is: would there be a large excess of positive charges over negative charges or vice versa.
If Pioneer has large solar panels then these may be accumulating charge from space or perhaps solar radiation is kicking electrons out of the panels leaving them with a net positive charge.
And how do we know the acceleration is real - is this acceleration due to a faulty signal coming from pioneer or from some faulty analysis by Nasa?
 
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Chronos:

If you have a body with the charge q, that is moving with velocity v through a magnetic field B ,then it will experience a Lorentz force

F = q(v x B)

This force is perpendicular to the velocity v and perpendicular to the magnetic field B. Or to put it another way, it is perpendicular to the plane that is defined by v and B. And I was no talking about solar effects in general (this would be interesting too), I was just trying to argue that an interaction between a possibly charged pioneer spacecraft and the magnetic field of the sun should not be cause of the anomaly.

battery:

You are right, surely it is not exactly 90 degrees, so there would be a (small) component of the acceleration pointing towards the sun. But there would also be a (larger) lateral component. Now if people are sure that the anomaly exclusively consists of the (extra) acceleration towards the sun, i.e. there is no lateral component, then I would insist that interaction with the suns magnetic field cannot be the cause.

If, however, there might be an unknown, lateral component, then you are right. And this might just be the case. Maybe they can measure the acceleration towards the sun with a high accuracy (Doppler perhaps ?), but have no idea whether there is any lateral acceleration of the same order of magnitude.
 
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Chronos

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No magnetic force has been suggested.
 
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Could the anomalous acceleration of the voyager spacecraft towards the sun be explained by its surface becoming electrically charged by friction with dust particles and the interaction of the electric charges with the sun's magnetic field?
I think that possibility has been considered.

However, the anomalous Pioneer acceleration has been shown to be a constant 8.7 X 10^-8 cm/sec^2 toward the sun....constant in both time and in solar distance between 20 AU and 70 AU.

Since the Lorentz force is dependent upon the strength of the solar B field, which must vary as approx. the inverse cube of solar distance , then it is not likely to be the causal candidate for a constant acceleration, (unless of course the velocity is increasing by the same factor which it isn't).

Creator
 
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I think that possibility has been considered.

However, the anomalous Pioneer acceleration has been shown to be a constant 8.7 X 10^-8 cm/sec^2 toward the sun....constant in both time and in solar distance between 20 AU and 70 AU.
Creator

Could a constant magnetic force caused by solar radiation accelerating charges in the interplanetary medium close to pioneer be pulling pioneer towards the sun on the side of pioneer facing the sun, while a smaller magnetic force (also caused by interaction of solar radiation and interplanetary charges) in pioneer's shadow is
pulling in the opposite direction.The net force on pioneer might stay constant with distance from the sun because the solar radiation becomes less intense with increasing distance but
the charges in the interplanetary medium might also be more dense
and therfore more likely to interact with the solar radiation.
 
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Could a constant magnetic force caused by solar radiation accelerating charges in the interplanetary medium close to pioneer be pulling pioneer towards the sun on the side of pioneer facing the sun, while a smaller magnetic force (also caused by interaction of solar radiation and interplanetary charges) in pioneer's shadow is
pulling in the opposite direction.The net force on pioneer might stay constant with distance from the sun because the solar radiation becomes less intense with increasing distance but
the charges in the interplanetary medium might also be more dense
and therfore more likely to interact with the solar radiation.
On second thoughts I think this scenario is unlikely because less and less energy is involved
as the sun becomes more distant.
 
I think the only realistic possibility is that pioneer becomes electrically charged more and more the further it moves from the sun by either friction with dust particles/charges in space or by its solar panels becoming positively charged by x rays,gamma rays and other energetic particles kicking out electrons - more electrons as time passes.
If by some chance pioneer is getting struck on one side by some freak radiation source then that source could be detectable from Earth when the Earth is in line with the radiation source and the sun as pioneer must be.
 
The fact that the planets do not seem to have this anomalous acceleration suggests that the solution lies with things that are metallic - like pioneer 11 and hence can conduct electricity and interact with magnetic fields.Electrons escaping from the sun and moving close to the speed of light and close to pioneer 11 could generate a large enough magnetic field to pull it towards the sun, in concert with any electric charges from the sun that stick to pioneer's surface, and interact with the sun's magnetic field to produce a force in the sun's direction.Over time more charges would stick to pioneer's surface as, with increasing distance from the sun, fewer solar photons strike pioneer with the energy needed to eject charges off the surface and more charges emitted from the sun have slowed down because of the sun's gravity and so don't bounce straight off the surface.
 
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Chronos

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No. Any such effect would follow the inverse square law thing, not linear acceleration.
 
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No. Any such effect would follow the inverse square law thing, not linear acceleration.

I disagree with this. FORCE = qvB for charge moving through a magnetic field.

For a steady force with time then if velocity is constant charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
So we need charge on pioneer to be inversely proportional to magnetic field cubed ( q~1/ B^3).If charge on pioneer is proportional to time of travel ( more charges could stick to pioneer as time goes by) for length ,width and depth of pioneer spacecraft then it is not impossible that a relationship such as q~1/ B^3 exists.
 
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I disagree with this. FORCE = qvB for charge moving through a magnetic field.

For a steady force with time then if velocity is constant charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
So we need charge on pioneer to be inversely proportional to magnetic field cubed ( q~1/ B^3).If charge on pioneer is proportional to time of travel ( more charges could stick to pioneer as time goes by) for length ,width and depth of pioneer spacecraft then it is not impossible that a relationship such as q~1/ B^3 exists.
Sorry,the writing above doesn't make sense and should read:

For a steady force with time then if velocity is constant, charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
So we need the charge on pioneer to be proportional to the cube of the radius from the sun, to give a force that stays constant with time.
 
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I disagree with this. FORCE = qvB for charge moving through a magnetic field.

For a steady force with time then if velocity is constant charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
So we need charge on pioneer to be inversely proportional to magnetic field cubed ( q~1/ B^3)....

battery; That may be possible in principle,.... but apparently my seemingly naive comments about the solar B field ..... have mislead you.

I used the VERY general idea that a dipole field decreases as 1/r^3 simply to merely show in one specific way the quite GENERAL incompatability of a Lorentz type force with the measured constancy of the anomalous acceleration, not to give license for an exact derivation.

In reality the solar magnetic field is far more complex and far more dynamic than I implied, its magnitude varying both with the solar sunspot cycle and with position throughout the interplanetary region.

The solar B field at the solar surface varies with time and is max. during solar sunspot max. and the field lines are carried outward in a complex way by the solar 'wind' into the interplanetary regions. The solar winds goes out radially but due to the sun's rotation, the B field actually goes out in a spiral pattern.

Furthermore, every 1/2 solar cycle (11 years) the magnetic field REVERSES.

These and other complications should certainly put to rest any idea that an electromagnetic Lorentz force could be responsible for a long term constancy in the Pioneer acceleration....(even with charge accumulation). :wink:

See here for some details and to catch up on some info that should reveal the veracity of my above statement.

http://science.nasa.gov/headlines/y2001/ast15feb_1.htm [Broken]

http://www.oulu.fi/~spaceweb/textbook/solarwind.html [Broken]


http://www.iki.rssi.ru/mirrors/stern/Education/wsolwind.html



Creator :biggrin:
 
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I read that the Mars Polar Lander and the Mars Beagle mission both ended disastrously and in the same region of space relative to the sun ( decemebers 4 years apart 1999 and 2003).Did rocks in space hit these craft? Are rocks in space causing the anomalous accelerations of pioneer and galileo?
 
battery; That may be possible in principle,.... but apparently my seemingly naive comments about the solar B field ..... have mislead you.
In reality the solar magnetic field is far more complex and far more dynamic than I implied, its magnitude varying both with the solar sunspot cycle and with position throughout the interplanetary region.
Creator :biggrin:
I suspected this could be the case and my suggestion is unlikely because we would expect to see a little of the charging on satellites near to Earth and perhaps charging of the Earth and effect on the Earth's magnetic field and position in space!



I read that the Mars Polar Lander and the Mars Beagle mission both ended disastrously and in the same region of space relative to the sun ( decembers 4 years apart 1999 and 2003).Did rocks in space hit these craft? Are rocks in space causing the anomalous accelerations of pioneer and galileo? Was the crater seen close to Beagle caused by Beagle or by a rock that hit beagle?
 
As a rough estmate, a rock with a density similar to water at 273K, would have to be 1 km from pioneer with a radius of about 100m to produce an acceleration toward the Sun of 10^-8 m/s/s. Perhaps there are lots of these rocks acting one after another along pioneer's route to keep the acceleration constant.Did NASA send pioneer on a route that uses the gravity of the planets to direct pioneer.If so then these rocks could be following a natural pathway.If they have a variety of trajectories and speeds there would inevitably be some that keep pioneer company at least for part of its journey.The large Tunguska event that happened 100 years ago and was attributed to a meteoroid may have happened so close to our lifetime (in geological timescales) because there are far more big rocks in space than we think there are.
 
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Garth

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As a rough estmate, a rock with a density similar to water at 273K, would have to be 1 km from pioneer with a radius of about 100m to produce an acceleration toward the Sun of 10^-8 m/s/s. Perhaps there are lots of these rocks acting one after another along pioneer's route to keep the acceleration constant.Did NASA send pioneer on a route that uses the gravity of the planets to direct pioneer.If so then these rocks could be following a natural pathway.If they have a variety of trajectories and speeds there would inevitably be some that keep pioneer company at least for part of its journey.The large Tunguska event that happened 100 years ago and was attributed to a meteoroid may have happened so close to our lifetime (in geological timescales) because there are far more big rocks in space than we think there are.
O come on..

The key characteristic of the Pioneer anomaly is that it is equal for both spacecraft on opposite sides of the solar system and constant over a period of about 30 years since they left the orbital region of Saturn.

Garth
 
O come on..

The key characteristic of the Pioneer anomaly is that it is equal for both spacecraft on opposite sides of the solar system and constant over a period of about 30 years since they left the orbital region of Saturn.

Garth
If NASA haven't been getting their sums wrong,magnetism and electricity aren't the answer,Einstein's theory of relativity hasn't got the answer,quantum mechanics hasn't,there are no thermal effects in space that can
account for the anomaly,no internal factors on pioneer,no unusual theories like le sage's theory of gravity can answer this problem,no viable theory of dark energy or dark matter has been proposed, what is the answer. The only thing that sems to make any sense is some (improbable as it may seem) coupling of rocks in space to the motion of the spacecraft by the mechanism of newtonian gravity.
 
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Garth

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This topic has been discussed many times here on PF, such as in this thread: Does the PA show that DM/DE is dynamically important in the outer solar system?

Either the effect has some normal physics explanation, such as leaking gas or spacecraft radiation, which now seems an unlikely explanation for all of the effect, or there is some new physics involved.

The anomaly was discovered in the first place when the data was analysed for anomalous accelerations to search for Planet X. The actual anomaly turned out to be much more mysterious and it hasn't gone away.

If there were a lot of rocks, small Planet X that produced an equal and constant acceleration in both spacecraft. then I would have thought they would have bumped into one by now.

Garth
 
All other considerations aside, the maintenance of a nominal orbit depends upon the momentum of the spacecraft and assuming that NASA is able to program and measure that accurately the problem is most likely one of defects in their calculations. Few if any scientists acknowledge that the traditional formula for centripetal force has an error factor in it which increases as the orbital period decreases. This is what concerns me with the DAWN satellites which NASA hopes to insert into orbit around small asteroids.

In regard to the solar orbiting satellites, any accumulation of charges would effect the momentum either negatively or positively depending upon the relationship of the orbital path to the complex solar magnetic fields, but I suspect that these effects would be very minimal.
 
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