I saw a meme that stated that, if you’re mad at someone, it take less Delta-V to launch them out of the solar system than in does to fire them into the Sun.
Why is that? Wouldn’t the attraction of the Sun’s mass be greater and provide assistance?
In: Physics
Oh, I just thought of one other thing. The meme you’re talking about, forgot to account for something: gravity assists.
Sometimes called a “slingshot maneuver,” it’s possible to cheat at this ‘delta-v’ game by taking advantage of moons and other planets, and flying past them at just the right speed and distance so that their gravity will bend your path in the desired direction.
Imagine you’re a superhero on the roof of a speeding truck, it’s going 100 km/h.
You need to jump off the truck to the ground, and in order to not hurt yourself and scrape your knee, you need to be falling *straight downwards* when you land. You can’t have any horizontal momentum.
This means you’re gonna have to be able to launch yourself backwards off the back of the truck at 100km/h, so that your launch speed counteracts the speed of the truck and your resultant ground speed is 0km/h.
In order to make something fall *into* the sun, instead of falling into orbit around it, we need to do basically the same thing, except the moving truck is the earth and it’s going 30km per second.
Earth orbits the Sun at more than 100000 km/h. That velocity (or at least a big part of it) needs to be gone in order for an object to “fall” into the Sun. This assumes the object has already left Earth and Earth’s orbit, which also requires changes in velocity.
Thats not how space works. It’s a bit counterintuitive, but it’s just as hard to get inside a gravity well as getting out of it because space has no friction.
If you orbit something you have a specific energy that keeps you in that orbit. To lower your orbit you need to reduce your kinetic energy, but since you can’t “brake” in space you need to accelerate in the opposite direction. (wich takes energy)
We are already more than halfway out of the suns gravity well, so leaving it is easier than getting to the center.
You can also trick this a bit. If your orbit is very elliptic like one of a comet then it takes only a tiny
You’re already booking it just being here on Earth
Earth is orbiting the Sun at 30 km/s, to leave the solar system from Earths orbit you need to get up to 46 km/s, and to crash into the sun you need to get down to 0 (or near). Since you’re starting from 30 that means escape requires a delta-V of 16 km/s, but hitting the sun requires 30 km/s in the other direction
The attraction of the Sun’s mass is what has caused the Earth to already be doing 30 km/s in orbit around it, and everything starting from Earth starts with that same velocity. You can do some gravity “assists” around Mars and Venus to shed some speed so you don’t need fuel for all 30 km/s of Delta V but it’ll still take a long time to get in close to the sun. The easiest way to get to the Sun is actually to add 16 km/s to reach escape velocity, scoot out to the edge of the solar system, burn a tiny bit more fuel to drop speed to zero, then wait 100 years as the probe slowly falls back inwards towards the sun (its fuel efficient but not time efficient)
It’s a fun meme, but it’s actually ~~incorrect~~. Edit: it’s actually correct
What is very difficult is to *orbit* close to the sun. Because when you approach the sun, you will gain a lot of speed, which you’ll need to lose if you want to enter a stable orbit. In space, accelerating and decelerating is the same problem, so decelerating a lot requires a lot of energy, more than what is needed to leave the solar system.
But if you want to get rid of someone, you don’t need them to orbit within the sun. If they hit the sun very fast, it works just as well, and ~~you don’t need the expensive deceleration phase~~.
So, from earth, you can simply move them to an elliptical orbit with high eccentricity, so that the orbit intersects the sun’s surface. ~~That’s actually much cheaper in energy than exiting the solar system~~ (but it’s still a very expensive way to get rid of someone).
But in practice, there is more or less zero use in impacting the sun or a planet at high speed. So that’s why when people discuss space, they always implicitly consider the cost of orbiting close to the sun or a planet, and not just the cost of hitting the surface at full speed.
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