this post was submitted on 13 Oct 2023
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So, it doesn't work the way you think.
It's only going that fast because it's near the sun. The same way a satellite close to Earth needs to move faster than one farther away. You can't really use that velocity to go elsewhere. It had to lose a lot of energy to get as close to the sun as it is. It would need to gain that back to get to earth.
I'm really blanking on a way to explain this concisely and I can't explain orbital mechanics in a Lemmy post.
If you play Kerbal space program, you can definitely use that to get a very intuitive understanding of this concept.
Drop a ball. It goes fastest just before and after it hits the ground, and slows down until it gets back to near the height you dropped it from
The probe is the ball, and slingshotting around the sun is like bouncing off the ground. The potential energy (height of ball/distance from sun) gets converted to and from kinetic energy (speed).
That's a pretty good answer. I was definitely overthinking it.
A little correction. They would be slingshotting around either Venus, Mercury, or both to lose energy.
Going around the sun is like just bouncing a perfectly elastic ball.
Close enough for this mental model, though.
Edit: in my own defense I am in Vegas doing minor Vegas things.
While I'd really rather be talking about orbital mechanics or some other geek shit, I do get to see an annular eclipse in totality in a beautiful national park. That's certainly a once in a lifetime event.
Seeing an annular eclipse is an excellent application of orbital mechanics! Enjoy!
I intend to. Provided I don't get trapped in the desert for days. We're bringing extra food, water, and eclipse glasses to auction to the highest bidder, though.
We didn't even plan this. The opportunity came up before I even knew that I could take a tour and see this.
Glad you are having fun. I never want to fly through Vegas again. That airport was outrageous, even by airport standards. Ended up paying $45 for a Shake Shack meal. Thankfully I had my rolling machine, tubes, and tobacco. They wanted $20 per pack of cigarettes, I forgot my lighter though, and paid $10 for a BiC lighter.
Oh. I hate it here. I'll never be back. My wife is here for work and convinced me to fly out for a long weekend.
It's awful. I don't party or gamble or smoke or really do much but outdoor and educational, and I particularly hate people trying to extract more money from me.
I'm fine with paying what it costs, even if that's a lot, but once I've paid, you don't talk to me about money again.
Plus everyone's smoking inside and smoking weed and driving and lower class than even Myrtle or Daytona Beach.
The airport was bad, then we realized that the Lyft driver ran up the meter on us by going the long, more trafficy way. I didn't even know that was possible.
Plus I now am away from home without a pair of glasses and with a case of pinkeye (bilateral, which I've never had before) that I must've picked up at the optometrist on Wednesday. Plus I can't seem to trick Google or this new kagi thing into telling me how common this is. It keeps telling me that optometrists can diagnose but not treat pinkeye in most jurisdictions. Of course it must be common.
Thanks! I didn't think about the fact that it'd lose velocity to gravity as it gets further away.
I wonder if you could slingshot a probe by firing it to fly by the sun and then shedding mass at its perihelion. The idea being that the craft would be mostly dead weight, increasing the force exerted on the craft by the sun's gravitational pull. Once you reach the perihelion, you eject the mass behind the craft so that there's less force acting on the craft as it moves away from the sun.
👍. I like science.
You wouldn't just drop mass along side you in space. It would just continue to float along beside you.
You definitely have to throw it behind you, like you said, but that's what rockets do. They throw mass behind them to make them move forward. That's a rocket.
When you throw mass behind you at one point in your orbit, you raise the height of your orbit on the opposite side of the orbited object (this is simplified).
So you're basically right, it's partially about the mass of the object, but it's mostly the firing of the rocket.
You've got some pretty good intuition though. That's basic orbital mechanics.
It even has a name, the Oberth effect
Just "shedding mass" won't do it. Uncouple a payload from the mass of the ship at perihelion, and they will just float along together, side by side in their original orbit.
But, if that "mass" is "rocket fuel", and you "shed" it by burning it behind you, you've got the right idea. As the other commenter said, the Oberth effect means the closer you are to the sun, the faster you are moving, and the greater the effect that burning will have.
Yes, the Oberth effect means that firing a rocket at the periapsis changes your orbit more than at any other point in the orbit.