NASA's Parker Solar Probe Reports Successful Closest Approach to Sun | Hacker News Reader

NASA's Parker Solar Probe Reports Successful Closest Approach to Sun

blogs.nasa.gov

94 pointsdivbzero17 comments

The temperature and radiation it has to endure is impressive, but I'm more blown away by good old fashioned gravity assists to yeet the probe and not have it fall into a fiery well of gravity.

192 km/s is pretty insane.

That's 0.06% of light speed?

And a bit over 10x what the Voyagers are traveling at?

Wonder what the time dilation would be. Must be in seconds with that soeed.

By my rough calculations about 18 milliseconds of time dilation per day assuming 690,000 km/h - 430,000 mph.

18 milliseconds per day is roughly 6.5 seconds per year: same order of magnitude as itishappy’s estimate elsewhere in this thread.

    1 / sqrt(1 - v^2 / c^2)

    1 / sqrt(1 - v^2)        (when v is in units of c)

    1 / sqrt(1 - 0.0006^2)

    100.000018% or about 5 seconds per year

    (I may have this reversed, but it doesn't really affect the numbers at this speed, just the sign.)

Is the dilation due to the Sun's gravity well larger than that?

Both from the sun gravity well and the high speed. Different kinds of time dilation.

Hitting the sun is actually surprisingly hard. It’s harder than leaving the solar system. Earth orbits at around 30km/s and you need 42km/s (+12km/s) to escape orbit.

They plan to eventually destroy the sensors by giving them full exposure to the sun but sadly the probe won't actually crash into the sun

https://en.wikipedia.org/wiki/Parker_Solar_Probe

Any idea why? It's not like its orbit will ever near the Earth again, and even if it did trashing the sensors probably doesn't affect its orbit.

Getting to the sun is really hard. Any object flying at earth's orbit has so much energy that you need to reduce in order to get to the center. The probe simply doesn't have enough propellant to slow down that much. The only other way that I can think of is to perform a gravity assist that would send the probe straight into the sun. And if you miss, the probe becomes a molten blob of metal that will forever continue flying in a highly eccentric orbit around the sun.

You don’t need to cancel out the velocity with respect to the sun though, since you aren’t trying to land on it, or even trying to enter into a circularized heliocentric orbit. The first two burns of a bi-elliptic transfer (as if you were attempting to insert to a nonexistent Earth orbit at the sun’s altitude) should put you on the right trajectory I think?

It's really bonkers to take a step back and realize there's just this unimaginably huge naked fusion reaction hanging out in space. Nothing fueling it but gravity. Absolutely insane.

Does increasing the speed via repeated gravity assists improve the odds of the probe surviving during closer approaches to the sun?

The opposite, actually. Increasing speed is the very thing that brings it closer to the Sun.

To clarify a bit... The gravity assists from Venus actually decrease the probes instantaneous speed, which allows it to fall closer to the Sun. The act of falling towards the Sun is what generates speed, with more speed being generated during closer approaches.

Most likely that they are usibg the gravity assists to decrease the orbit (e.g. slow down) not to increase the speed. As your orbit gets more and more elliptical, your closest point to the celestial body gets closer and your actual speed relative to the celestial body increases dramatically.

It sounds contradictory, but think of that in this way: you have an incredible amount of energy stored in potential energy relative to sun and by decreasing your orbit you convert this to kinetic energy.

Think about falling into the sun from several billion kilometers, but just missing it slightly because you still have a bit of horizontal momentum left.

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