When wanting to exit our solar system, do we have to always go outward from the sun in the direction of the other planets? Or can we simply travel “north”?
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Followup question cause now I’m very curious, are there other planets/stars directly above and below earth? Do we know? Has anyone done a 3D map of space?
I just watched this series with my 9 y/o to help us both understand orbital mechanics
Didn’t one of the Voyager craft do that?
What you’re referring to is called “the plane of the ecliptic”, basically the flat plane in which more or less the whole solar system orbits.
And the short answer is we don’t *have* to, but it’s way more efficient. It’s hardly impossible, just costly… and we don’t really have a good reason to do it.
Rocket science all comes down to fuel efficiency. Acceleration is expensive, and you pretty much have to carry the mass of all the fuel you’re going to use from the very beginning of your trip. Fighting gravity is expensive.
Advantages of travelling in the plane of the ecliptic:
* You get to use your existing orbital velocity (Earth’s speed as it travels around the sun) as a starting point for the escape velocity you need to climb out of the sun’s gravity well.
* You get to use the gravity of planets and other massive bodies further out to help “slingshot” you further and faster.
Problems with leaving the plane of the ecliptic:
* Orbital velocity is in the wrong direction, so it doesn’t really help you much. You could try to find a way to slingshot around the south pole of another massive body, like maybe Venus, to translate that momentum into a different axis, but that requires a bunch of extra maneuvering, and maneuvering costs fuel.
* Instead of being helped along by gravity wells further out, you basically have to hit escape velocity sufficient to overcome the *collective gravity well of the entire solar system’s mass*. You’re a long way from most of it, but it still matters.
Finally, basically everything we want to get to is in the plane of the ecliptic.
* Nearby rocky planets like Venus and Mars that might be candidates for colonization.
* Asteroids and the asteroid belt, which might have resources we want, and might need to be studied closer in light of possible future collision hazards.
* Gas giants that bear closer study, like Jupiter and Saturn.
* Jovian/Saturnian moons, which might have resources or even extra-terrestrial life (Titan, Enceladus, and Europa, especially).
* Cometary bodies/the Oort cloud, if we want to send a probe *way* out there.
Up the Z axis is basically empty. Even if you were trying to get to Alpha Centauri, ~ 4 lightyears away, you’d be better off heading along the plane of the ecliptic initially and then slingshotting off Jupiter to get you off the plane at the right angle.
Does not make much sense these days, but when new engines will be used, we will see this more often. There are reasons to go there.
Like Voyager 1 and Ulysses you’d still launch on the ecliptic and then head out to Jupiter to use its gravity to fling you to the new inclination as this is far more efficient than trying to burn fuel to do it
I’ve read that many deep-space probes used Jupiter’s gravity to “slingshot” them. Pass by close enough, but not too close, and you whip around.
No reason you couldn’t, but current propulsion tech is what limits us to traveling on our “solar plane”. If we had some high powered/efficient energy source that wasn’t liquid/gas propellant based you could go any direction you wanted, you just need to counteract the inertia you already have.
This is also the reason why its actually super energy heavy and sort of counter intuitive to send something to the sun. We are moving pretty fast in orbit and you need to to slow down for gravity to “pull you in”.
One other thing too is that all the planets are generally on a flat-ish place. So it kinda makes sense to do some drive byes as we send things out of the solar system, otherwise you are wasting opportunities to study things.
If you just went “up”, you miss out on all that science, and you don’t leave the solar system any sooner. The heliosphere is… well, a sphere, so you wouldn’t get to interstellar space any sooner.
While all the other posters are correct, I’m going to try to help you demonstrate what they mean.
Let’s imagine you are the sun, and your hand is the earth. A ball in your hand will represent a satellite, or whatever you’d like to exit the solar system. (In this demonstration, your arm will represent the gravitational attraction between the sun (your body) and earth (your hand)
Experiment with trying to get the ball to move in various directions like “upwards”, and “outwards”.
Now start spinning around. You’ll want to go fairly quickly, but obviously not so fast that you can’t stomach it. (You can use an office chair, or a frictionless surface). Hold the ball at arms length. This is how the sun and the earth move in relation to each other. As before, experiment with trying to get the ball going in different directions like “upwards”, and “outwards” to see how it feels, and what happens when compared to being stationary.
I expect that when you try to throw it upwards, you end up having to throw it about equally as hard as when you were stationary to get it to the same height. The ball may also go outwards inadvertently. When you try to get the ball to move outwards, you can simply let the ball go, as opposed to throwing it.
Hopefully that demonstrates what people in the comments mean when they describe needing extra fuel, inefficiency, and orbital velocity. As a bonus, a “gravity assist” is basically if your friend were doing this same thing (spinning around on a chair nearby), caught the ball you just threw, and then let it go. The ball needs to be thrown with less energy each time to get further outwards.
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