A friend told me that with the current engineering we cannot send a satellite to the sun (just reaching it, not survival) because we would have to nullify the velocity of earth with respect to the sun. I’m not sure I understand and not sure if that is true.
In: Physics
If you’re still having trouble understanding it, this may help:
[https://www.youtube.com/watch?v=LHvR1fRTW8g](https://www.youtube.com/watch?v=LHvR1fRTW8g)
Earth isn’t falling into the sun because it’s in orbit. It’s going so fast to the side that by the time it would have fallen into the sun, it’s moved out of the way. If you want a spacecraft to get to the sun, you have to stop moving as fast at the Earth is. But in space, there’s no land or air to slow you down. So, instead, you point your rockets in the direction that you’re moving towards and fire for the same amount of time that you would to get to that original speed from a standing start. Then, you’ll keep being pulled toward the sun, but you won’t go to the side at all, and you’ll just fall into the sun. But it takes a *lot* of fuel to do that. Like, way too much to be viable. Going to Mars, for example, just takes speeding up from Earth’s orbit a bit. That way, you’re moving faster to the side than you’re falling, and you’ll get further away from the sun before your arc takes you back down. Then, you just match’s Mars’s speed as you approach it, and you can enter its orbit. That takes a *lot* less fuel than just dropping straight into the sun.
Get a friend to jump on a playground roundabout, spin it as fast as you can then get them to throw a ball for you to catch. That in a nutshell is why it’s hard to get a sattelite to the sun, we’re spinning at about 1,00MPH (the roundabout) but we are also orbiting what we are trying to aim at so you also have to imagine the roundabout going around you while also spinning.
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Its easy to send something into orbit around the sun. Its hard to send something INTO the sun. This is because anything that is launched from the earth is already orbiting the sun. To send something into the sun it has to be accelerated in the opposite direction we’re orbiting which is about 67000 miles per hour. That takes a lot of energy and fuel.
Yes this is true. For any kind of higher orbit you need more speed and lesser orbits less speed. If you’re already going fast, you have to spend energy to slow down.
https://www.theatlantic.com/science/archive/2018/08/parker-solar-probe-launch-nasa/567197/
Imagine you’re in a car travelling at 30mph. (Obviously you’re in a kid’s seat because you’re 5.) You open the window and drop a ball. You might expect the ball to fall straight down. What will actually happen is that the ball will fall, but in an arc. This is because it’s already going forwards at 30mph, and its momentum carries it forwards. To make it fall straight down, you’d actually need to throw it backwards at 30mph to cancel the speed of the car.
Probes are the same. If you launch one from Earth, it’ll want to orbit the Sun along with Earth. To make it head right for the Sun, we need to throw it ‘backwards’.
Now you might think we could just fire it at the Sun. But that’s like throwing the ball down. It will keep going forward, but will bounce higher. Similarly, firing the probe at the Sun will still make it miss, but it’ll end up in an even bigger orbit!
I mean, it’s not true. But it is hard. For the simplified case where the sun is a point-mass and there’s nothing between us and the sun, yeah it’s difficult because your probe or ship will have Earth’s orbital velocity trying to put you in orbit around the sun. But if you have a way to scrub off some of that velocity, say by slingshotting off of Venus or Mercury, and aerobraking in the outer layers on the sun you could hit it. We recently sent a probe within a few solar radii in fact (not into the sun because they want it functional). Should be there in the next few years.
Pretend you’re in a moving car, and you throw a ball forward out of the car. The speed of your throw is added to the speed of the car and it moves forward until air resistance and gravity slow it.
Now you throw an identical ball backward. The speed of your throw is subtracted from the speed of the car and it moves forward until air resistance and gravity slow it.
The same thing happens when launching a vehicle (ball) from earth (car), except in space you can pretty much ignore resistance and gravity as we understand them on earth **and** speed moves you away from the sun while slowing down moves you toward it.
The Earth is moving at about 67,000 miles per hour. When you launch an object from Earth, it starts off with that same speed.
That speed is why the planet, and any other object, stays in orbit. In order to get closer, you have to reduce the speed. To get to the sun, you have to reduce that speed to almost 0.
The escape velocity from the sun at Earth’s distance is 94,000 miles per hour. So to launch an object out of the solar system, you only need to change its speed by 27,000 miles per hour.
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