Funnily enough orbital mechanics don’t work that way. To accelerate towards an object ahead of you in your orbital plane you need to lose velocity, drop into a slightly lower orbit, then gain velocity to slow down and intercept.
Velocity is tightly coupled to altitude when orbiting.
::what do you think happens when your speed is lower than the orbital speed?
Answer: you move to a lower orbit, then stay there.
When you try to reduce orbital velocity (say by firing thrusters in the opposite direction), you change to a lower orbit -- you don't just start free falling to the object you are orbiting. In fact, the net effect is that your actual velocity will increase. For example Mercury's velocity is 170,503 km/h, while Earth's is 107,218 km/h, and Mars is 86,677 km/h.
Here's another counter-intuitive thing about orbital mechanics. Say you want to catch up to something in front of you -- you fire reverse thrusters, which causes you to fall into a lower (and faster) orbit, then you can fire forward thrusters to raise your orbit once you catch up to the other object (i.e., you do a move that you would normally do to "slow down" in order to "speed up").
Slow down to get into a lower orbit, where you will overtake your target. Then speed up to get back into the higher orbit where the target will catch up with you.
> When you try to reduce orbital velocity (say by firing thrusters in the opposite direction), you change to a lower orbit -- you don't just start free falling to the object you are orbiting.
Well, technically you do just start free falling - you have been the entire time you've been orbiting.
And you have to decelerate to catch up to the station in orbit. If you accelerate you will fall back.
That's because if you fire your rockets to accelerate you end up in a higher orbit, i.e. your circle is much bigger, and vice versa, to overtake/catch up you want to fall to a lower orbit. That's also not intuitive to someone with "earth-experience".
I've seen this idea on Reddit before, and it was explained that the issue of getting to orbit has nothing to do with altitude and everything to do with velocity.
You can be a great deal farther away from the Earth than orbital altitudes, but if you're not actually orbiting, you're going to fall directly toward the surface.
> What's wrong with accelerating toward the planet
It rotates the orbit, which is not the most efficient way to de-orbit. Instead, to de-orbit with minimal delta-v expended, you burn retrograde at the highest point of the orbit. This will lower the lowest point of the orbit into the atmosphere.
Makes sense. Get up to a higher speed and it’s easier to do a controlled slow down. Than having to speed up after getting into orbit near another orbiting body.
You don't get to orbit by going up far enough, if you did you'd just end up falling back to earth.
You get to orbit by going fast enough, so that acceleration due to gravity acts perpendicular to your velocity and so acts to change your direction and pulls you around the earth.
> The orbit becomes less circular and more elliptical. While the higher point (apogee) is further away than before, the lowest point (perigee) is closer.
Orbital dynamics is complicated and I admit I could be wrong here, but I'm pretty sure this is incorrect. If you push radially outward from a circular orbit, it should raise the apogee but keep the perigee the same.
I could see this working if you exert a radially outward force on an object in an elliptical orbit that is already coming in from apogee to perigee, because relative to the object's radial velocity that would actually be a braking maneuver. Is that what you meant?
If you're accelerating towards an orbital object you are by definition not in the same orbit as the target object. If you were you would be moving at the exact same speed. This effect makes getting yourself close enough for docking all sorts of tricky if you don't know what you're doing. Once you get close enough (like in the linked simulator) you can mostly ignore the problem since the effects are small given the relative speeds involved.
I can heartily recommend messing around with orbital maneuvers in KSP to get a feel for the problem. It's not exactly intuitive.
I highly recommend you play Kerbal Space Program if you want to get an intuitive understanding for how it works. But in short, yes, and also if you accelerate towards another orbiting object your own orbit becomes more elliptical such that over sufficient distance you will actually move away from it rather than toward it.
Once you're in orbit (say around the sun), you have to cancel the orbital velocity to fall into the object you're orbiting around. If you point at the sun and accelerate 1 km/s directly at it, you're still moving 30 km/s "sideways". All you'd end up doing is making the orbit more elliptical-shaped.
At least that's how I see it, but I am far from being an authority on this topic.
Cannot agree more. If I remembered correctly, there was such an obvious bug in 'Gravity' that in the orbit, if you want to catch up with another object in front of you, you cannot simply accelerate, or you will result in getting further from it. In stead you will have to decelerate first and then accelerate again. The result is counter intuitive, I remember that simply because I did not believe it at first and as a result we did such calculation on the blackboard while I was in high school.
High circular orbits move a lot slower than lower circular orbits (eg: geostationary orbits basically don't move at all relative to the ground). It's the highly elliptical orbits that have massive velocities.
Velocity is tightly coupled to altitude when orbiting.
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