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13

Escaping the solar system requires adding orbital velocity to the spacecraft. Similarly, getting closer in the solar system requires removing orbital velocity. It turns out Earth is more out of the Sun's gravity well than it's in it. In other words, the simple answer is that Mercury is "farther away" in terms of the change of velocity that's ...

12

Based on the calculations presented by @uhoh I generated a plot showing the necessary delta-V for a fly-by mission, i.e. entering into a Hohmann transfer with a far point intersecting the orbit of a planet to get into a circular orbit at the same radius as a planet Note that this does not include any methods to save fuel (aero-braking, swing-by) and ...

25

Changing orbits requires delta-v. To reach the Sun, you need to subtract delta-v such that your velocity relative to the Sun is near zero, which allows you to "fall straight down" into the Sun - your required delta-v is nearly equal to your orbital speed. To escape the solar system, you need to add sufficient delta-v in order to reach escape ...

7

Many quantitative questions about orbits can be answered using the vis-viva equation $$v^2 = GM\left(\frac{2}{r} - \frac{1}{a} \right)$$ where $a$ is the semi-major axis, $r$ is the current distance to the central body and $v$ is the velocity at $r$, and the vis-viva equation comes straight from the principle of conservation of total energy which is the sum ...

58

Because the earth goes very fast around the sun. If you want to get to the sun, you need to slow down almost completely so that your speed relative to the sun becomes almost zero. If you don't slow down (almost) completely, your probe will miss the sun when you 'drop' it, so it will eventually come back and you'll end up in an elliptical orbit. Kind of like ...

4

Check these visualizations from NASA. Solar Orbiter will never get as close as Parker Solar Probe perihelion. That's why it can operate a camera pointed directly into the Sun and why it didn't have to wait for better shielding technology to arrive. The goal is to get the spacecraft (Parker Solar Probe) to fly through the corona at a distance of 9.5 solar ...

8

Other spacecraft have been closer, but none have carried Sun-facing imagers. Source: The link you provided ("Other spacecraft" is linked to an article about Parker Solar Probe) Q: Or did Parker just not take pics of the Sun yet? A: Yes, or at least not from a distance closer than Solar Orbiter

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