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164 points pseudolus | 4 comments | | HN request time: 0.797s | source
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pavel_lishin ◴[] No.42472143[source]
> Now, you might naively think that it's the easiest thing in the world to send a spacecraft to the Sun. After all, it's this big and massive object in the sky, and it's got a huge gravitational field. Things should want to go there because of this attraction, and you ought to be able to toss any old thing into the sky, and it will go toward the Sun.

Yes, yes, speak orbital dynamics to me!

> The problem is that you don't actually want your spacecraft to fly into the Sun or be going so fast that it passes the Sun and keeps moving. So you've got to have a pretty powerful rocket to get your spacecraft in just the right orbit.

What?! No! I mean, yes, you don't want your spacecraft going right into the sun itself, but that's not the major reason why it's difficult! It's that at launch, the spacecraft is already in orbit around the sun - since it came from the Earth. And left to its own devices, it won't want to "fall" into the sun any more than it already is, any more than the Earth is falling into it. Changing orbital parameters that much is expensive in terms of delta-V!

As I recall, the "cheap" way of getting into a low-enough orbit to get that close to the sun is to counterintuitively first expand your orbit massively, and then do a retrograde burn at the highest point. (But I'm guessing the Parker Solar Probe used gravity assists.)

I wonder if some editor cut a large part of this paragraph.

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1. strongpigeon ◴[] No.42474238[source]
You would think Eric Berger (who's a pretty seasoned space writer) would have played Kerbal Space Program. That game took my understanding of orbital dynamics to a whole other level. I was immediately bothered by that paragraph as well.
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2. daveslash ◴[] No.42474894[source]
I'm not a KSP pro, but I have tried and tried to fly into the sun and have yet to succeed. Even if I do my best to lose as much of the planet's orbital velocity as I can until I'm out of fuel, and I begin to fall towards the sun.... I still always miss and then just go into an elongated elliptical orbit. It's really hard.
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3. Filligree ◴[] No.42475164[source]
You'll want a bi-elliptic transfer orbit. And probably a larger rocket.
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4. LorenPechtel ◴[] No.42475920{3}[source]
I would suspect that a slingshot at Jool would do it but I've never tried.