Mystery of the Slingshot Maneuver

There is a pole reversal at play here, for the last 100 years as such as they reverse they become weaker. So all fly bys the earth are not as much as a push as they think it would be. Earths gravity field must weaken to it to reverse or it will not happen. By the way this will be in full play by.

You guessed it 2012.

reply to post by jsettica



I assume you are talking about the geomagnetic reversal of earths magnetic field? That is, interchanging the north and south magnetic poles?

I find it fascinating. At that point, there can be bazillion possibilities as to why it happens. Some of them are already listed in the OP. I was also thinking of dense chunks of Solar Wind hitting the craft.

This is the next frontier for physics experiments. You can scatter small objects off asteroids and try to measure the trajectory with maximum possible precision, then try to account for various effects. Just a thought.

Originally posted by Droogie

Scientists were hoping to gain more insight into the anomaly when the Rosetta spacecraft swung by Earth on Nov. 13 2009 to pick up a gravitational boost for its journey to rendezvous with a comet in 2014.

However, in a major disappointment – which had deepened the mystery — the Rosetta spacecraft did not experience the flyby anomaly during this swingby of Earth in 2009, even though the same spacecraft did experience the anomaly when it flew by Earth 2005, but didn’t in 2007.

I think it's intruiging that it happens sporadically, and unpredictably at this point.

Are we sure this means it's happening sporadically? I suppose that's one possibility, however another possibility that might account for non-repeatable observations historically has been observational error.

That cause (observational error) was previously suspected as one possibility for the similar but possibly unrelated Pioneer anomaly

A number of proposed explanations for acceleration towards the sun have been pursued. These are defined as the following: observational errors, an unaccounted for real deceleration, and explanations that would essentially be New Physics.

Observational errors
The possibility of observational errors, which include measurement and computational errors, has been advanced as a reason for interpreting the data as an anomaly. Hence, this would result in approximation and statistical errors. However, further analysis has determined that significant errors are not likely because seven independent analyses have shown the existence of the anomaly (Pioneer anomaly) as of March 2010

So while observational errors have apparently been ruled out for the Pioneer anomaly, can we say the same for the flyby anomaly? I'm not sure but based on what I've read so far, I don't think we can rule out observational error for the flyby anomaly, especially based on the failure of the Rosetta spacecraft to experience any anomaly on the last 2 of its last 3 flybys of the Earth.

[edit on 3-8-2010 by Arbitrageur]

Originally posted by EnlightenUp
reply to post by bigfatfurrytexan

 

Centrifugal force doesn't really exist.

Correct.

There are only two 'forces' acting on a spacecraft as it falls unpowered into a gravity well: momentum and gravity.

For a spacecraft performing a slingshot manoeuvre around a planet in the Solar System, the gravity comes from the interaction of its mass with the Sun as well as with the planet. Good old three-body problem.

What's happening out at Saturn with Cassini, taking all those moons and things into account, is mind-bogglingly complex because of the number of bodies involved.

*

Originally posted by 4nsicphd
It is really rather meaningless to try and discuss this issue without describing it in terms of second or higher approximations of perterbational calculus. Become conversant with Leonhard Euler's work...

I think it's safe to assume that multibody perturbations, as well as more exotic stuff like relativistic effects, are already being accounted for here, and that this strange acceleration is supplementary to all that. But you are clearly a very clever fellow, and it is wonderfully condescending--in the complimentary, Victorian sense--of you to advise us. You wouldn't happen to be wonderfully munificent--also in the complimentary, Victorian sense--as well, would you? I could use a purse of gold right now.

After collecting data over a few decades one would HOPE it's not a simple observational error. That said, perhaps something is affecting the observations/readings and not the crafts themselves.

I've read a book or two on these missions and the lengths they go to to account for every single factor even down to what a "normal" person would consider negligible effects is extreme, to say the least. To say they are anally retentive is an understatement. Since some of our greatest minds are involved in these projects, I would say the effect is real. Remember, the observations are saying that the crafts are accelerating FASTER than any known physics can account for.

I'm going to go out on a wild consiracy theorist limb here.

Maybe gravity itself is not a universal constant. Maybe it varies slightly dependent on other unknown factors. Maybe the velocity of a body through it's galaxy has some effect. For example, let's pretend there is another solar system IDENTICAL to ours in another part of the galaxy but it is moving faster. Wouldn't the mass of it's sun and planets be more as mass increases as an object is accelerated (at some point the mirror solar system would have accelerated to it's faster speed). I believe the eggheads are having a hard time actually pinning down a value for gravity with the excuse it's so small compared to the other three forces.

I have no doubt I will be corrected as reqired.

reply to post by Arbitrageur


Regarding the Rosetta craft, I assumed the anomaly didn't occur since the excerpt of the article stated that it didn't. When they say they got disappointed when the craft didn't experience the anomaly during it's fly-by in 2009 and 2005, I assume they where looking for it and that it wasn't due to an observational error. And that's why this "further deepened the mystery", and that's also why I assume it happens sporadically.

But you might be right though, I wouldn't know. But can try to find some more information regarding the rosetta incident and see if they might have been open to the possibility that it was in fact due to observational error.

I won't say anything about historical incidents, but you might very well be right.

[edit on 4/8/10 by Droogie]

Haven't really read many of the replies, but it reminds me of the looping that glider-pilots use to pick up speed...


...no idea how that would translate in space though

[edit on 4-8-2010 by alaskan]

Originally posted by Astyanax
I think it's safe to assume that multibody perturbations, as well as more exotic stuff like relativistic effects, are already being accounted for here, and that this strange acceleration is supplementary to all that.

Again I don't make too many assumptions like that, which is why I find this paper interesting:

Special relativity may account for the spacecraft flyby anomalies

The empirical formula proposed by J. D. Anderson et al. [1] to reproduce the data on the Earth flyby anomalies is derived from special relativity (SR). The transverse Doppler shift together with the addition of velocities account for the Doppler data. Time dilation together with the addition of velocities account for the ranging data.

I also don't assume that paper's proposed explanation is correct, as I've seen no consensus from the scientific community that it satisfactorily explains the observations.

Originally posted by Droogie
Regarding the Rosetta craft, I assumed the anomaly didn't occur since the excerpt of the article stated that it didn't.

I don't make too many assumptions that I don't have to. These are relatively tiny anomalies. Here is some material on observational error, I'm pretty familiar with this stuff:

Experimental Error in Physics.ppt

(p1)Experimental Error in Physics, A Few Brief Remarks… [What Every Physicist SHOULD Know]
Repeatability is the cornerstone of Science!
(p3)No observation or measurement is truly repeatable!
The challenge is to understand the differences between successive measurements
Some observations differ because they are genuinely unique!
Some are different because of RANDOM CHANCE
Most real measurements are a combination of BOTH

So maybe I should clarify my explanation of observational error to include random chance. What portion of the measured discrepancy from expectations resulted because the measurement is unique and what part of the discrepancy resulted from random chance? There was actually a slight DECREASE in the Rosetta 2009 flyby versus expectations but they attributed that to random chance so that's why they called it no anomaly. That presentation is a pretty good read regarding experimental and observational errors if you are interested in that kind of thing.

wapedia.mobi...

Summary of Earth-flyby spacecraft is provided in table below. [2] The Rosetta data is for its first flyby in 2005; the second flyby produced no significant anomalous increase, and the third a negligible decrease.

Look at the size of the 2005 Rosetta anomaly for example (infinity values):
Velocity 3,863,000 mm/s
Anomaly 1.82 mm/s

So the anomaly as a proportion of the velocity is 1.82/3063000=0.00000047 which is pretty small

Not only that, but note the anomalies are not consistently increases even when the amount of deviation from expectation IS considered significant::

phys-merger.physik.unibas.ch...
[atsimg]http://files.abovetopsecret.com/images/member/79fa6cb0f8c6.png[/atsimg]

The mixture of plus or minus signs on the flyby anomalies tends to suggest more of a random cause than a new physics, doesn't it?

When they say they got disappointed when the craft didn't experience the anomaly during it's fly-by in 2009 and 2005, I assume they where looking for it and that it wasn't due to an observational error. And that's why this "further deepened the mystery", and that's also why I assume it happens sporadically.

As I said, it may happen sporadically as they suggest. But you have your years wrong. There was a slight increase in the Rosetta flyby in 2005 over what was expected, then in 2007 there was no increase over what was expected, and in 2009 there was a slight decrease observed but the amount wasn't considered significant so that's why they called it no anomaly.

reply to post by Arbitrageur


Thanks so much for your input, I have to say you seem considerably more knowledgable about this than me, but that's not saying much since I'm pretty dumb relative to this subject. I'll try to learn something from your input, some of it may be a bit over my head though, but I will definitely look through the links you provide. And I have to say you make some good points explaining the cause of the "mystery" put forward in the article, so thanks again.

Although I can't find it now, I had a science book from the 50s which showed how to make a simple ION powered model that would produce a small but measurable thrust.
It used a battery, a coil, and a bb, in a straw. on a string, hung like a pendulum, against a protractor

It involved charge and magnetism, the conditions I am sure, are created during certain relationships to the sun and a planet and its magnetic field on certain trajectories.

[edit on 5-8-2010 by Danbones]

Originally posted by Arbitrageur
The mixture of plus or minus signs on the flyby anomalies tends to suggest more of a random cause than a new physics, doesn't it?

Not really, although it's possible.

Again, using a toy model of interaction with density fluctuations in the solar wind, I could say that on different occasions the craft experienced either a boost or deceleration depending on the particular geometry of scattering.

reply to post by buddhasystem
If I understand what you're saying, it seems to support my point, as fluctuations in the solar wind, if that or something like it turned out to be the cause, wouldn't involve new physics, would it? I'm not ruling out new physics, but just saying that people who point to that as a likely candidate for the cause don't really have a lot of evidence to support that claim. It's possible but I wouldn't say it's likely.

If all the signs of the anomaly were the same and it was more consistent, I'd be more excited about the possibility of some new physics being involved.

The pioneer anomaly is a smaller effect, but I think it's more consistent, as I haven't seen anything about sign reversals of the direction of the effect.

I have read with interest the comments relating to the slingshot effect. I know little to nothing about the subject or space science other than what basic logic affords me. I am a retired auditor, which gives you some idea of my limited technical abilities.

To me some of the ideas like the tether effect seem illogical. A space ship flies in a straight line not a circle, as it approaches a planet. Ergo centrifugal force of a spacecraft is not present. How about a somewhat similar dissimilar idea?

As the vehicle approaches a planet, one which does in fact have a slingshot effect on the craft, gravity pulls the vehicle toward the planet. In doing so it changes the direction of the vehicle and increases its velocity. Theoretically, the same gravitational force must be overcome to leave the planet’s gravitational field, assuming there is no extra resistance to overcome. The exiting velocity should logically decline by the amount gained while approaching the planet.

Something else happens when the vehicle approaches the planet. The planet is rotating. (It has to rotate or there will be no slingshot effect should my logic prevail.) The planet’s gravitational field and atmosphere, if any is around, grab onto and hold the vehicle to some minor or major extent, adding its rotational speed to that of the vehicle. Only part of that speed is transferred to the vehicle, because it only gets a brief exposure to the rotation effect.

The vehicle tries to match the rotation speed of the planet, but the gravitational force of the planet is not strong enough to keep it in sync with the planet, given the overpowering initial forward momentum of the vehicle.

I visualize the slingshot effect as being similar to that of a pitching machine. A hard ball goes from zero to whatever speed, as it hits a rotating wheel and is tossed toward the batter. The increased of the baseball and a space vehicle can probably be calculated by really smart folks, using current physics, assuming they have the basic data to work with. I assume they do because our space program has used the effect with positive outcomes.

The vehicle picked up speed, due not to gravity, but to the lock on ability of gravity coupled with the planet’s rate of rotation. Having picked up speed, gravity pull plus lock on rotation pull, the vehicle continues on its merry way. After breaking the planet’s gravitational field, It loses gravitational speed increases, but retains planet rotationally imparted speeds.

Our moon rotates, which is why we have been able to slingshot around it. I have no idea if my logic holds in reality, but I like it as an easy to understand logical explanation.

An argument against this logic would be that we have had no increased vehicle speeds on some vehicles ‘slingshoting ‘ past earth. An reasonable explanation might be that the vehicle passed across one of the essentially stationary pole areas.

Slingshot
only works,,
when a good solid connection exists.

no loose plugs

Would a disruption of the magnetosphere cause enough "turbulence" to counter the slingshot effect? Typically our magnetosphere's bow wake looks somewhat like a comet's tail. But every now and then it can be flattened or tussled up like a bird's nest due to solar activity or interaction to recently passed objects. Wouldn't striking unusual spikes or flat spots have a significant effect on the small boast of speed?

reply to post by retirednv

As the vehicle approaches a planet, one which does in fact have a slingshot effect on the craft, gravity pulls the vehicle toward the planet. In doing so it changes the direction of the vehicle and increases its velocity. Theoretically, the same gravitational force must be overcome to leave the planet’s gravitational field, assuming there is no extra resistance to overcome. The exiting velocity should logically decline by the amount gained while approaching the planet.

You're right, save for one word: 'velocity'.

Substitute 'speed' (a scalar quantity) for 'velocity' (a vector) in the above paragraph and the problem is solved.

Yes, the spacecraft leaves the planet around which it was slung with the same speed, relative to the planet, at which it arrived.

However, its direction of motion and hence its velocity relative to the Sun have altered. That's really all there is to it.

Here is a more detailed explanation from Wikipedia. You'll find the inset diagram helps a lot.

reply to post by bigfatfurrytexan


you got it. I wonder that NASA makes these claims they don't understand it when there are examples of the same speed increase in figure skaters that pull their arms in close, or in space where two planets or suns orbit each other and at closest pass they both speed up as they loop around.

As a craft cuts a diagonal path inside our gravity it is subjected to a tighter faster spin than being outside of our gravity.
Gravity assist has been written of in sci-fi for decades.. If that is a new article I can't help but wonder why they are only mentioning it now and as pointed out they have the math down to fine details so for sure they know...

Yes, the spacecraft leaves the planet around which it was slung with the same speed, relative to the planet, at which it arrived.

That is incorrect. What actually happens is that the PLANET loses kinetic energy in the process (assuming that the gravity assist manouevre has been designed to accelerate the spacecraft; it could just as easily be used to decelerate the spacecraft, except that this would require a significantly different approach trajectory).