The Parker Solar Probe will make its closest approach yet to the Sun

> 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.

i was thinking the same but with respect to this entire article -- feels like we're missing the second half and/or much more detail. feels like the article was due in to the editor by 11pm and the author forgot and started writing it at 10pm. :x

either way, very fascinating experiment. i look forward to hearing about the results!

would a solar sail be a feasible - albeit long time scale - method of getting the delta-v to decrease the orbit? Just point it retrograde and wait a long time?

I absolutely hate that AI is the first thing I think of whenever I see things like this now.

Yes, innocent mistakes happen in writing and editing all the time. But look at that whole paragraph you're quoting. It does exactly what sloppily-guided AI does: It's using words in an order that sounds relationally intuitive, but taken as a whole it's ping-ponging across completely unrelated concepts. It can't have come from a human, unless, like you said, parts were removed in editing without re-reading the result.

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.

Yes, Parker used gravity assists, several passes by Venus.

The cheapest way in terms of delta-v in the real solar system is actually to use Jupiter, launch to there and slingshot against your incoming velocity to cancel it out and drop towards the sun. Parker considered this, but decided not to because it would complicate the spacecraft design to handle operations at Jupiter (cold) and at the sun (hot).

And yes, without assists, it's harder to get from Earth to the sun than to anywhere else. Solar escape velocity is 42 km/s at the altitude of Earth's orbit. Earth's orbital speed is 30 km/s, closer to escape velocity than to the near-0 you would need to drop all the way to the sun.

I disagree. I have encountered tons of humans who do exactly that - Use "words in an order that sounds relationally intuitive, but taken as a whole it's ping-ponging across completely unrelated concepts". It's not unique to AI, it's fairly common across bullshitters of all stripes. But perhaps more tragically, it often happens to actually big thinkers whose brain is connecting dots so fast that they're eliding a bunch of important hops along the way, and while the former is more common, it's easy to confuse for the latter.

I might be missing something, but here is my thinking... the radiation coming out of the sun would always be perpendicular to your direction of travel around the sun at any given moment, so it would only ever be able to add delta-V and increase your orbit, not reduce it.

Unfortunately you can't do upwind sailing in a vacuum.

That being said, you can still use it for the method described in parent post, but you'd still need a different propulsion method to slow you down at the apogee.

They can eventually decrease orbit toward the sun. They just need to be angled in such a way that the thrust is retrograde (not the sail itself). It would be incredibly slow though.

You should be able to tilt your mirror/sail at 45°, so that the reflected light heads off in the direction of your travel, so that the momentum it imparts works against your current velocity, slowing you down, and degrading your orbit. Right?

Hey, sometimes you get called on in standup when you're trying to do some work, and you just have to glue some words together. I'm just glad nobody's writing those words down and publishing them!

They can be used to decrease orbit as well. Since you just need to bleed off the speed from Earth's orbit, you could angle the sail diagonally so the the reflected light is pushing against your direction of orbit (sort of like how the fins on a pinwheel are angled).

While I was googling, a couple places likened it to tacking into the wind, but that's a different kind of phenomenon that works because of friction and pressure differences.

I think that if you're constantly being thrusted radially out, you don't actually gain delta-v or increase your orbit - you just shift it. Your apoapsis increases, but your periapsis decreases.

(It's been awhile since I've played KSP, I could be wrong.)

I'm not wild about the title either. In English, "fly into the sun" implies permanence and they exploited that for title bait.

Better, "closest approach" or even "dip into" would say that Parker will keep doing its job afterwards, maybe even lower the next time!

Sailors have figured this out centuries ago to travel against the wind (called tacking). Some of the same principles apply, like orienting the sail so that photons push against the sail reducing the angular momentum.

Thats improv, not standup; granted, one must be agile either way.

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.

It sounds like for large changes in orbit, a bi-elliptic transfer can beat Hohmann: https://news.ycombinator.com/item?id=42357272

Tacking works because you have resistance against two media (air and water) which are travelling at different velocities -- you need a keel in the water. Solar sails don't have an analogous second medium.

You'll want a bi-elliptic transfer orbit. And probably a larger rocket.

I would suspect that a slingshot at Jool would do it but I've never tried.

I don't think it has the delta-v to go lower. Anything it loses to the solar wind on the flyby comes off the apoapsis, not the periapsis. Really messed up mission to Eeloo, returning the capture burn for Kerbin would have been around 2,000m/s and I only had half of that. After many reloads I managed to make it work: I put the encounter distance in the upper atmosphere and waited until the burn would complete a bit past periapsis to light the engine. The booster was destroyed by the heat just after the engine shut down, a good portion of my heat shield burned off but I came out of the encounter slowed just barely enough for capture. I turned around and waited. Every time around my apoapsis would drop, the periapsis stayed almost constant through many orbits. When my apoapsis was low enough I didn't expect to get another orbit I turned back around and went in.

Plane change maneuvers are expensive

Scrum standup, not comedy...

But they do! The (sort of) analogous second medium is gravity. You can “sail upwind” with a solar sail by angling it to reduce your orbital velocity.

I think this will be the greatest travesty of AI, that will hurt us beyond what any stolen+regurgitated content ever will. AI is going to steal our faith in each other, our faith in fellow humans. because you'll never know for sure, if you're talking/listening to a human or not. This will lead people to treat each other worse because of being jaded by talking to bots all the time.

"Sailing upwind" here -- if you were genuinely tacking, rather than doing something analogous to tacking -- would (with a big enough solar sail) let you propel yourself into the sun more quickly than gravity alone would pull you in.

So yes, you can produce a sideways component and let gravity do the rest, but that component can never actually push you towards the sun.

Sure, the analogy is loose, but as a sailor myself, I think it fits the fundamental ethos- one works the natural forces against each other to get where they are trying to go- wind, tides, and both aerodynamic and hydrodynamic lift.

The fact that one has a number of force vectors in varying directions with both sailing and solar sailing, both let you work them together in unison get where you want to go.

Quite often when I am "sailing" the wind is light or dies, and I go to "windward" by timing the currents, and wind at best lets me position for the right currents, but below a sufficient level produces no lift to windward.

Fair, although I think the analogy breaks down quickly enough that it's not necessarily helpful.

> It's using words in an order that sounds relationally intuitive, but taken as a whole it's ping-ponging across completely unrelated concepts. It can't have come from a human

...or from my emails; I'm an atrocious writer.