Is their an upper limit to the speed (less than light speed of course) you can achieve via graviational slingshot?

Could we use this method to send a probe to another star by continually building up speed over a few decades and then sending it off into interstellar space.

i would say yes. depends on the mass of the planet you’re slinging around and how close you can get.

DV or martin would be the ones with a better idea though.

A gravitational slingshot doesn’t increase the absolute speed of the spacecraft, only its velocity relative to the sun. That’s what makes this technique useful to get spacecraft to solar escape velocities.

http://en.wikipedia.org/wiki/Gravity_assist#Limits_to_slingshot_use

For a given solar system, there would be a practical limit to what could be achieved.

In answer to your second question, you can certainly use slingshot maneuvres to get up and beyond the solar system’s escape velocity.

as the voyagers show.

http://www.universetoday.com/113488/how-do-gravitational-slingshots-work/

JudgeMental said:

http://en.wikipedia.org/wiki/Gravity_assist#Limits_to_slingshot_use

Reading that link now

In practical terms wouldn’t there be things being slung around by the black holes of galaxys?

Cymek said:

Is their an upper limit to the speed (less than light speed of course) you can achieve via graviational slingshot?

Could we use this method to send a probe to another star by continually building up speed over a few decades and then sending it off into interstellar space.

Oh … Kay …

… About three years ago I had exactly the same idea, and went blithely about the task of building up huge spacecraft speeds by shuttling the craft between Jupiter, Saturn, Uranus and Neptune, bouncing around the Sun with no loss of speed when no planet was in the correct alignment. I used real planetary positions, but simplified trajectories. The result looked great.

Then …

… I calculated how close the spacecraft would have to get to the planet in order to get such an enormous speed. The result effectively killed off my idea. Too high a slingshot speed and the spacecraft slams into the planet instead of being speeded up, or at least gets so close that the upper atmosphere it passes through results in aerobraking.

I ended up with a maximum slingshot speed of roughly twice the speed of Voyager, ie. about 150,000 km/hr. Not good enough for relativistic space travel to the stars, unfortunately.

wookiemeister said:

In practical terms wouldn’t there be things being slung around by the black holes of galaxys?

Sure. Although that’s a bit different to a plain Newtonian gravity assist, since relativity rules have to be used when calculating trajectories near a BH, for several reasons. Firstly, the velocities involved tend to be high, so SR effects come into play. But more significantly, the gravity is so intense that the Newtonian approximation for gravitational force
(F = Gm₁m₂/r²) is no longer accurate, so GR must be used to calculate acceleration in terms of spacetime curvature. Also, if the BH is spinning (which is likely) there will be frame dragging (spacetime twisting) to take into account, too.

The upshot of this is that the classic Newtonian trajectories for a small body orbiting a single large body, the conic sections (i.e parabola, circle, ellipse, hyperbola) are not solutions to motion under GR. Elliptic orbits precess rapidly and soon go chaotic. A circular orbit is kind of stable, but even that will decay relatively rapidly due to gravitational radiation.

So virtually anything that approaches a BH will either cross the EH or get flung away, although some stuff does get into temporary orbits, especially if it can lose some kinetic energy by colliding with other matter in the vicinity, i.e. the BH’s accretion disc.

Of course, such collisions can also cause material to be ejected. And material ejected from the accretion disc tends to travel rather rapidly, otherwise it won’t escape, and the stuff trapped in the disc is already moving at relativistic speeds. So any stuff that falls towards a BH with the right vector to miss the hole & the accretion disk will almost certainly be deflected at a fair clip. :)

Some neutron stars are traveling at very high speeds relative to the mean galactic orbital speed in their (current) neighbourhood. One possible explanation for this is that the supernova explosions that give birth to neutron stars tend to be somewhat asymmetrical, so outer bits can get blasted off in one direction while the collapsed core heads in another direction. And if this happens to a star in a binary (or higher multiple) star system, the escaping neutron star could get a massive gravitational slingshot as it passes its companion star.

as you are around

if gravity is a wave , whats its frequency?

wookiemeister said:

as you are around

if gravity is a wave , whats its frequency?

Depends what colour it is.

Actually I have no idea, good question.

https://einstein.stanford.edu/content/relativity/q1618.html

https://www.physicsforums.com/threads/graviton-energy-and-frequency-wavelength.242145/

Janus is a reliable poster.

wookiemeister said:

as you are around

if gravity is a wave , whats its frequency?

Gravitational waves propagate changes in gravitational potential through space, and the frequency of those waves depends on the rate of change of the gravitational potential, which in turn depends on the masses involved and their motion.

It’s a lot like the magnetic waves between a pair of magnets. If the magnets are anchored somehow and not moving then there are no magnetic waves, just a static field, but if one (or both) magnets are allowed to move then you’re going to get waves propagating.

So don’t try to think of the simple gravitational attraction between two bodies operating in terms of some sort of wave exchange between them, it’s not particularly helpful. :)

There are various important differences between gravity & magnetism. Firstly, magnetism can be attractive or repulsive, whereas gravity is always attractive (as far as we know). Secondly, not everything creates or responds to a magnetic field, whereas everything creates and responds to gravity.

In a sense, gravity is extremely weak. The electromagnetic repulsion force between a pair of protons is about 10⁴⁰ times greater than their gravitational attraction. But because gravity’s purely attractive it dominates on the large scale, whereas electromagnetism tends to neutralise itself.

Now some of you may think
that gravity is strong,
cuz when you fall
off your bicycle,
it don’t take long
Until you hit the earth,
and you say,“Dang that hurt!”

But if you think the force
is powerful,
you’re wrong.

You see. gravity,
it’s weaker than weak!
And the reason why
is something many
scientists seek.

They think about dimensions.
We live in just three,
but maybe there are others
that are too small to see.

It’s into these dimensions
that gravity extends,
which makes it seem weaker
here on our end.

And these dimensions are
rolled up,
curled so tight
that they don’t affect you
in your day-to-day life.

but if you were as tiny
as a graviton,
you could enter
these dimensions
and go wandering on.

And they’d find you…

LHCb sees where
the antimatter’s gone
ALICE looks at collisions
of lead ions.
They’re lookin’ for whatever
new particles they can find.

>But if you think the force
is powerful,
you’re wrong.

You see. gravity,
it’s weaker than weak!
And the reason why
is something many
scientists seek.<

Stenger says that’s a popular fallacy. The only reason gravity is weak on tiny scales is because elementary particles have such low mass.

Bubblecar said:

>But if you think the force
is powerful,
you’re wrong.

You see. gravity,
it’s weaker than weak!
And the reason why
is something many
scientists seek.<

Stenger says that’s a popular fallacy. The only reason gravity is weak on tiny scales is because elementary particles have such low mass.

I don’t think it makes sense to say gravity is weak in comparison to the electromagnetic forces. It really depends on the charge/mass ratio of the objects. If an object has a high mass to charge ratio, gravity will be dominant force.

dv said:

I don’t think it makes sense to say gravity is weak in comparison to the electromagnetic forces. It really depends on the charge/mass ratio of the objects. If an object has a high mass to charge ratio, gravity will be dominant force.

Aye the actual force strength is meaningful in relation to such measurements but otherwise an arbitrary thingy, like C.

Bubblecar said:

>But if you think the force
is powerful,
you’re wrong.

You see. gravity,
it’s weaker than weak!
And the reason why
is something many
scientists seek.<

Stenger says that’s a popular fallacy. The only reason gravity is weak on tiny scales is because elementary particles have such low mass.

Or alternatively, the only reason elementary particles have such low mass is because gravity is weak on tiny scales.

The Rev Dodgson said:

Or alternatively, the only reason elementary particles have such low mass is because gravity is weak on tiny scales.

That’s arguably less meaningful, but this is not the right time for an argument.

PM 2Ring said:

In a sense, gravity is extremely weak. The electromagnetic repulsion force between a pair of protons is about 10⁴⁰ times greater than their gravitational attraction. But because gravity’s purely attractive it dominates on the large scale, whereas electromagnetism tends to neutralise itself.

Bubblecar said:

>But if you think the force
is powerful,
you’re wrong.

You see. gravity,
it’s weaker than weak!
And the reason why
is something many
scientists seek.<

Stenger says that’s a popular fallacy. The only reason gravity is weak on tiny scales is because elementary particles have such low mass.

dv said:

I don’t think it makes sense to say gravity is weak in comparison to the electromagnetic forces. It really depends on the charge/mass ratio of the objects. If an object has a high mass to charge ratio, gravity will be dominant force.

Indeed. Which is why I started that paragraph with “In a sense”. Still, the quarks, leptons, nucleons and nuclei in our universe do have rather low mass to charge ratios, so gravity is relatively negligible for them.

wookiemeister said:

as you are around

if gravity is a wave , what’s its frequency?

I suspect that’s calculable, using the particle-wave duality with the hypothetical graviton particle.

mollwollfumble said:

wookiemeister said:

as you are around

if gravity is a wave , what’s its frequency?

I suspect that’s calculable, using the particle-wave duality with the hypothetical graviton particle.

My thought (donkey’s years ago) about this, was that gravity may have a wave-function, with half-wave frequency equivalent to the length of life of the universe.

https://www.physicsforums.com/threads/graviton-energy-and-frequency-wavelength.242145/

this what i posted before seems, to me, to give the best answer as to the frequency of gravity.