What is the theory behind this?

[ste]

When traveling to the spacestation and you drop out of supercruise mid way there and then you just fly there by normal power for a while for whatever reason, why does the spacestation distance seem to be getting further away.

I guess it has something to do with it traveling around the planets orbit. And it must be really fast to out run your spaceship.

But when you get close you are easily much faster than it and it barely seems to be moving at all.

I have wondered that for ages but its only while impatiently waiting for the beta I thought I bring it up.

 

[Literalyte]

You are not in the space station's frame of reference, and its positional data keeps updating. This means it will move away (or towards) if it's orbiting.

 

[Susimetsa]

Indeed, when you are too far away from an object, you will not be in their "frame of reference". Planets and moons orbit their parents at very high speeds - much faster than the speed limit of the space crafts in the game - so you can never actually catch up with them without the supercruise (or by waiting along their orbit until they reach you, of course).

 

[Susimetsa]

In short, there's no theory. There's just a magic "frame of reference" to lock you to the moon's, station's or planet's speed when you are close to it.

 

[Vargur]

Orbits around a planet can be quite fast.
Just orbiting around earth like the ISS space station is at nearly 8 km/s.
The orbit speed of the space stations in ED is of similar order of magnitude, depending on the planets mass and the radius of the orbit.

 

[Vandaahl]

When traveling to the spacestation and you drop out of supercruise mid way there and then you just fly there by normal power for a while for whatever reason, why does the spacestation distance seem to be getting further away.

I guess it has something to do with it traveling around the planets orbit. And it must be really fast to out run your spaceship.

But when you get close you are easily much faster than it and it barely seems to be moving at all.

I have wondered that for ages but its only while impatiently waiting for the beta I thought I bring it up.

Its a delicate balance between the gravity of the star, the mass of the orbiting objects (thats also you), and the distance between the star and the object.

If our Earths mass would be double, we would be orbiting or much further away from the sun at the same speed, or, at the same distance but our year would last much longer. Earth get its inertia from the speed its traveling with around the sun, a staggering 100.000 km/h. All is stable, because the force of the suns gravity is exactly the same as the force of the Earths inertia.

Now try to imagine you are traveling at 3/4 AU from the sun. You have just exited super cruise and at a steady speed of 280 m/s (Cobra speed) flying towards Earth. That speed is nothing, so lets rule that out for a second. Imagine you are stable, then you are just orbiting our sun (otherwise you would be falling towards the sun). Now, the inertia you and your ship have to generate is very low, because your mass is very low and, because of that, the pulling force of the suns gravity is low. This will result in very low orbiting velocity. The difference between your orbiting velocity and the Earths will be huge.

The more you will travel towards Earth, the more you will become part of the Earth gravity field, the more you will gain speed (thats exactly what happens in super cruise), you'll have to start braking. When you are finally fully part of the Earths gravity field, it seems like you have come to a stop, while in fact you are traveling at the same speed around the Sun as Earth, 100.000 km/h.

So the key thing is up to what degree you are part of a gravitation frame of reference. The more you are part of the Suns frame of reference, the bigger the difference between you and earth. And the other way around.

 

[Mephane]

Its a delicate balance between the gravity of the star, the mass of the orbiting objects (thats also you), and the distance between the star and the object.

If our Earths mass would be double, we would be orbiting or much further away from the sun at the same speed, or, at the same distance but our year would last much longer.

I don't know where you got that idea from, but that is not true. For two bodies A with high mass and B with (relatively) low mass, the orbit can entirely be calculated by the mass of the heavier object, the current distance between A and B, and the velocity of B. (If the masses are rather similar, they will both orbit a common barycenter between them, as is the case with many binary stars.) If the Earth had formed with twice the mass, it would still move within the very same orbit.

Also, orbits are not that delicate. Two bodies orbitting each other is a very stable system, instabilities only arise between three or more bodies, and even then, the common result is that one of the bodies (usually the lightest) may be flung out of the system, but not fall onto one of the other objects.

Collisions, as in, for instance, asteroids hitting an object, primarily happen when two independent orbits happen to cross very closely and with good timing. There is then also some gravitational interaction that can change both orbits, but rocks don't just fall out of the sky - we just happen to cross their path sometimes.

Edit: I want to clarify the first paragraph a bit further: an orbit is effectively a free fall where your horizontal velocity component is so big that the curve that your trajectory describes is at least as large as the curvature of the object you are orbitting. (Or, as a wise man once wrote "the trick with flying is to fall and then miss the ground".) We all know that two objects in free fall accelerate at the very same rate regardless of their mass, the same applies to orbits because an orbit is a free fall.

 

[Vandaahl]

If the Earth had formed with twice the mass, it would still move within the very same orbit.

...and with the same speed?

 

[ste]

So say the spacestation is travelling at 30,000m/s. Does that mean when you get to the spacestation and you enter the same orbit and gravity you are really traveling at 30,000ms plus your ship speed.

 

[Mephane]

...and with the same speed?

Yes, of course, otherwise it wouldn't be the same orbit (if the Earth suddenly lost some of its speed, its orbit would become highly elliptical with the opposite side getting closer to the sun).

So say the spacestation is travelling at 30,000m/s. Does that mean when you get to the spacestation and you enter the same orbit and gravity you are really traveling at 30,000ms plus your ship speed.

Yes, if you wouldn't the station would move that fast relatively to you. You guys here should really try out Kerbal Space Program, it is great at teaching orbital mechanics.

Edit: Mandatory xkcd.

 

[Joe Spivey]

Will you guys stop making my head hurt? Please?

 

[Vandaahl]

For two bodies A with high mass and B with (relatively) low mass, the orbit can entirely be calculated by the mass of the heavier object, the current distance between A and B, and the velocity of B.

Thanks for that. I assumed my statement looking at Kepler 2nd law, which shows the relation between angular velocity and distance in elliptical orbits. I thought mass was part of the equation as well. I guess its time to have a look at some old books again. Assuming is the mother of all, you know...

 

[ste]

Will you guys stop making my head hurt? Please?

Yeah, I kind of wish I hadnt asked. Most of this stuff is way over my sore brow

 

[Hootmon]

Will you guys stop making my head hurt? Please?

You need to get your head into a stable orbit.

 

[Soda Popinski]

Thanks for that. I assumed my statement looking at Kepler 2nd law, which shows the relation between angular velocity and distance in elliptical orbits. I thought mass was part of the equation as well. I guess its time to have a look at some old books again. Assuming is the mother of all, you know...

Or play Kerbal Space Program. The game that makes orbital mechanics fun!

 

[metatheurgist]

So say the spacestation is travelling at 30,000m/s. Does that mean when you get to the spacestation and you enter the same orbit and gravity you are really traveling at 30,000ms plus your ship speed.

Yes. The Earth is hurtling through space at 30 km/s, the sun is moving through the galaxy at 220 km/s. You don't notice this if you're in geostationary orbit above the Earth but you're doing the same thing. Everything is relative.

 

[alexios]

So say the spacestation is travelling at 30,000m/s. Does that mean when you get to the spacestation and you enter the same orbit and gravity you are really traveling at 30,000ms plus your ship speed.

Sort of. You add the velocities, not the speeds (unless you're travelling in the exact same direction).

Velocity (and therefore speed) is defined relative to some point of reference. You could see this in FFE. It would display something like ‘Relative to: Lave’ to give you your reference point.

 

[Guy DudeBroMan]

Thanks for that. I assumed my statement looking at Kepler 2nd law, which shows the relation between angular velocity and distance in elliptical orbits. I thought mass was part of the equation as well. I guess its time to have a look at some old books again. Assuming is the mother of all, you know...

Gravity accelerates all objects at the same rate regardless of their size or their mass. If you wanted Jupiter to orbit 1 AU from the Sun, where Earth currently does, then Jupiter would orbit at exactly the same speed as the Earth does despite the fact that it is many times the size and many times the mass. In orbital mechanics, "horizontal speed" is the only metric that really matters in relation to the orbiting body.

 

[Achilles Maelstrom]

Or play Kerbal Space Program. The game that makes orbital mechanics fun!

I was just about to say that. This brings me to another question. If/when you're relying on Newton to get from A to B, is there a way of knowing where in orbit you currently are? Like the map in KSP? I think it would be a huge help if you could actually see the trajectory you're on.

On a side note, I'm just uploading a video where I witnessed the gravitational forces of a planet by turning every system off, except for lifesupport and scanners. Ship has been accelerating on its own. Maybe this is a bug and not a feature?

 

[Pinworm45]

If the earth had higher mass, it would have higher gravity, and thus the pull between it and the sun would be higher, drastically changing the entire solar system nevermind the Earth's Orbit.. is what my scientific knowledge tells me. Lots here are saying differently.

Would anyone mind telling me where I am incorrect, if I indeed am?