The Parker Solar Probe will make its closest approach yet to the Sun(arstechnica.com)
arstechnica.com
The Parker Solar Probe will make its closest approach yet to the Sun
https://arstechnica.com/space/2024/12/were-about-to-fly-a-spacecraft-into-the-sun-for-the-first-time/
150 comments
Most of the comments so far are about the temperature and the closeness to the sun, and, hey, I get it: those are both amazing to think about. But to me even more amazing is... 0.16% of the speed of light?? Yikes.
Pretty sure it's 0.064%, not sure why the article got it wrong, still impressive though
Correct. About 18 milliseconds of time dilation per day assuming 690,000 km/h - 430,000 mph.
Still. ~200,000 m/s (= ~430,000 mph) is unfathomably fast.
It is, although I was still a little surprised it's on the order of a minute to go NYC to Tokyo at that speed. My intuition was it would be much less time.
Light loops around the earth ~7.75x a second iirc so a few orders of magnitude less makes sense
Light is fast, but it isn't imperceptible. The original experiments to measure it in a lab involved spinning rigs and mirrors between hills. When dealing with objects the size of continents, such as phone or other communication systems, the delays are well within our abilities to detect.
terrestrial phone / internet carried by undersea cables are gated by the relays more so than c. the ping time from US to Australia (one way) is about 115 ms (rounding down, using most optimistic data.
Light can travel over 34,000km in that time. The great arc distance from LA to Sydney is just over 12,000km. In all likelihood the fiber line connecting them doesn't follow that arc, but it shouldn't be too far out of limits. So about 2/3 of the latency is caused by relays and switching equipment.
it gets even worse for satellite, because (until starlink) communications satellites are in geosynchronous orbit, 35,000km above the equator. so talking on one means a 70km round trip, which causes its path to take over 5x more distance than the linear distance (across the surface) between those 2 cities.
Light can travel over 34,000km in that time. The great arc distance from LA to Sydney is just over 12,000km. In all likelihood the fiber line connecting them doesn't follow that arc, but it shouldn't be too far out of limits. So about 2/3 of the latency is caused by relays and switching equipment.
it gets even worse for satellite, because (until starlink) communications satellites are in geosynchronous orbit, 35,000km above the equator. so talking on one means a 70km round trip, which causes its path to take over 5x more distance than the linear distance (across the surface) between those 2 cities.
>> it gets even worse for satellite, because (until starlink) communications satellites are in geosynchronous orbit
No. There were and are other communication satellites in lower orbits. SpaceX did not invent the concept of low-orbit communications satellites. The first satellites of the 90+ Iridium constellation were launched in the late 90s. That system is still online in low orbit today. Before that there were various military/state-owned satellites. The Soviet Union and Russia were big on providing coms to areas where the geo-stationary relays could not, specifically the north, as far back as the 60s. See the Molnya program.
https://en.wikipedia.org/wiki/Molniya_(satellite)
https://en.wikipedia.org/wiki/Iridium_satellite_constellatio...
No. There were and are other communication satellites in lower orbits. SpaceX did not invent the concept of low-orbit communications satellites. The first satellites of the 90+ Iridium constellation were launched in the late 90s. That system is still online in low orbit today. Before that there were various military/state-owned satellites. The Soviet Union and Russia were big on providing coms to areas where the geo-stationary relays could not, specifically the north, as far back as the 60s. See the Molnya program.
https://en.wikipedia.org/wiki/Molniya_(satellite)
https://en.wikipedia.org/wiki/Iridium_satellite_constellatio...
Iridium existed but how much backhaul did it actually carry? it was meant for very low-bandwidth applications.
> So about 2/3 of the latency is caused by relays and switching equipment.
Not really; the speed of light in fiber optic cable is only about two-thirds of that in a vacuum. That means it takes light about ~60ms to travel the 12,000km great arc distance.
Not really; the speed of light in fiber optic cable is only about two-thirds of that in a vacuum. That means it takes light about ~60ms to travel the 12,000km great arc distance.
thats a great point, I failed to consider c in the propagation medium. however, OP didn't specify that either, he just insinuated that we can perceive propagation delays by c. we are both wrong (in his specific case about telecom delays, we have absolutely contrived experiments to detect it)
>> The great arc distance from LA to Sydney is just over 12km.
12,000km ?
12,000km ?
fixed, thank you
Right now I’m reading the Expeditionary Force series and one thing the author drives home is how incredibly slow the speed of light is.
The speed of light is the speed of causality, so obviously it can't be too fast or everything will be in instantaneous causal contact. It's not strange that biological creatures find that things over distances that "feel" distant actually take light some perceptible "time" to reach.
Yeah, it always sticks in my mind that the time it takes for light to reach the top of the Eiffel tower from the ground is measured in nanoseconds. Maybe that came from a Grace Hopper talk?
Microseconds even! Light travels about 0.3 meter in a nanosecond, and the Eiffel tower has a height of ~300 meter, so it takes about a microsecond for light to get from the ground to the top.
~200,000 m/s is unfathomably fast.
It's about 110,000 fathoms per second.
It's about 110,000 fathoms per second.
Or if you prefer leagues, at that speed it would still take 9 minutes to reach the depth in Jules Verne's book.
The title refers to the distance the _Nautilus_ traveled while submerged, not the depth it reached.
Until I realized this, the title was quite confusing. If “20,000 leagues” were referring to depth, it would be enough to go all the way through the Earth, exit the other side, and then make it a quarter of the way to the moon.
Yeah he really needed a comma.
20,000 Leagues, Under the Sea
I think it reads cleaner.
20,000 Leagues, Under the Sea
I think it reads cleaner.
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Helios2 was half that speed in 1976
I guess everything with a sun slingshot is going to be impressive.
We'd have 1% speed-of-causality probes by now if it meant better war machines but best they can do with the budget
Vaguely related they did capture light moving with a 1 billion frames per second experiment so Femtosecond Photography is definitely some cutting edge stuff.
I guess everything with a sun slingshot is going to be impressive.
We'd have 1% speed-of-causality probes by now if it meant better war machines but best they can do with the budget
Vaguely related they did capture light moving with a 1 billion frames per second experiment so Femtosecond Photography is definitely some cutting edge stuff.
> 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.
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.
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.
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.
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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.
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.
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'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!
Better, "closest approach" or even "dip into" would say that Parker will keep doing its job afterwards, maybe even lower the next time!
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.
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.
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.
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.
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!
Thats improv, not standup; granted, one must be agile either way.
Scrum standup, not comedy...
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.
> 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.
...or from my emails; I'm an atrocious writer.
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!
either way, very fascinating experiment. i look forward to hearing about the results!
It sounds like for large changes in orbit, a bi-elliptic transfer can beat Hohmann: https://news.ycombinator.com/item?id=42357272
Plane change maneuvers are expensive
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 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.
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.
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?
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.
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.
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.
"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.
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.
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.
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.
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.)
(It's been awhile since I've played KSP, I could be wrong.)
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.
Reminds me of this far side comic, https://static1.srcdn.com/wordpress/wp-content/uploads/2023/...
I don't get the Far Side. Could a Cliff Clavin chime in ?
Children's song lyrics I heard growing up.
Sun, sun, Mr. Golden sun, sun shine down on me.
Sun, sun, Mr. Golden sun, sun shine down on me.
Yeah I'm generally a big fan but that one is a bit obscure - according to this [0], it's just the incongruity of trained professionals in mortal danger using a childish nickname for the thing that's about to destroy them.
[0] https://www.cbr.com/the-far-side-confusing-comics-like-cow-t...
[0] https://www.cbr.com/the-far-side-confusing-comics-like-cow-t...
I think it's simply out of fashion. E.g., "Don't mess with Mr. In-between" is a line from the 1940's song "Ac-Cent-Tchu-Ate the Positive." It's addressing abstract entities in a personalized form, which --I assume-- is a style convention commonly understood at the time.
https://www.youtube.com/watch?v=5Qk9o_ZeR7s
https://en.wikipedia.org/wiki/Ac-Cent-Tchu-Ate_the_Positive
I learnt of this song through the fantastic series "The Singing Detective."
https://www.youtube.com/watch?v=5Qk9o_ZeR7s
https://en.wikipedia.org/wiki/Ac-Cent-Tchu-Ate_the_Positive
I learnt of this song through the fantastic series "The Singing Detective."
Those only smart enough to think of our local star as "Mr Sun" perhaps should not be piloting craft in its vicinity.
If KSP is to be believed, this is shockingly difficult to do
It requires seven Venus flybys, and 24 orbits around the sun[1]. Wikipedia has a nice animation of the trajectory[1], and NASA has another one here[2].
[1]https://en.wikipedia.org/wiki/Parker_Solar_Probe?wprov=sfti1... [2]https://svs.gsfc.nasa.gov/3966/
[1]https://en.wikipedia.org/wiki/Parker_Solar_Probe?wprov=sfti1... [2]https://svs.gsfc.nasa.gov/3966/
Second link is beautiful and really shows the whiplash of the last set of solar encounters. Recommend clicking through to anyone with a passing interest.
In order to 'land' on the sun, or any celestial body, you need to get rid of your orbital speed. Higher orbital speed means higher orbit altitude. Landing on earth is comparatively easy, because you can use the atmospheric drag to slow down. It is so difficult to land on Mars because of it's thin atmosphere. Alternatively you need a shitload of fuel to burn to kill that velocity.
Earth's orbital velcity is ~30km/s. So by extension, anything that comes from Earth will at least have that speed. So the probe needs to find 30km/s delta v in order to actually get close to the sun.
Earth's orbital velcity is ~30km/s. So by extension, anything that comes from Earth will at least have that speed. So the probe needs to find 30km/s delta v in order to actually get close to the sun.
I wonder if you can use atmospheric drag to pull you into the Sun / a different star / Kerbol.
Long ago, playing Elite if I remember correctly, you could fly close to a star and scoop up a load of hydrogen for later resale. I'd be interested to see a graph of gas density vs tendency to melt spacecraft compared to distance from the core for a typical star.
Long ago, playing Elite if I remember correctly, you could fly close to a star and scoop up a load of hydrogen for later resale. I'd be interested to see a graph of gas density vs tendency to melt spacecraft compared to distance from the core for a typical star.
> wonder if you can use atmospheric drag to pull you into the Sun
You can, and I believe this probe will. The Sun’s atmosphere is just much nastier than our own, which means your aerobraking destroys your spacecraft quicker.
You can, and I believe this probe will. The Sun’s atmosphere is just much nastier than our own, which means your aerobraking destroys your spacecraft quicker.
It was Elite. Once you had a fuel scoop there was no requirement to dock and refuel any more so it was much easier to be a pirate or privateer.
There was a bug (or was it?) in the very PC version where by if you had fuel scoops installed, set your view to looking out the rear of the ship, flew toward a star, and ignored all the warnings on your dashboard, you could fly right through the star. If you were being chased at the time you had the additional satisfaction of watching your pursuers' ships explode as they tried to follow you in.
There was a bug (or was it?) in the very PC version where by if you had fuel scoops installed, set your view to looking out the rear of the ship, flew toward a star, and ignored all the warnings on your dashboard, you could fly right through the star. If you were being chased at the time you had the additional satisfaction of watching your pursuers' ships explode as they tried to follow you in.
>So the probe needs to find 30km/s delta v
I don't understand why we aren't doing solar + ion drive everywhere (except obviously launch), and instead we settle for slow multi-year multi-grav-boosts trajectories. Current ion drives (by NASA and on Starlink) have 2500-3500 Isp. Which means that even 100+ km/s is easy doable with just 2 stages.
I don't understand why we aren't doing solar + ion drive everywhere (except obviously launch), and instead we settle for slow multi-year multi-grav-boosts trajectories. Current ion drives (by NASA and on Starlink) have 2500-3500 Isp. Which means that even 100+ km/s is easy doable with just 2 stages.
I assumed that if I did out the math on this, it would be clear why we don't, but then I did and I now share your confusion.
The Parker Solar Probe mass is 555kg. An achievable amount of ion thrust is around 0.5N. Thus, running that thruster would accelerate the craft at 0.0009m/s2.
Getting such a craft to 30km/s of delta-v would therefore take about 33.3 million seconds of thruster time, or about 13 months.
I don't know what the duty cycle is on ion thrusters. Maybe they aren't robust enough to fire for over a year straight?
The Parker Solar Probe mass is 555kg. An achievable amount of ion thrust is around 0.5N. Thus, running that thruster would accelerate the craft at 0.0009m/s2.
Getting such a craft to 30km/s of delta-v would therefore take about 33.3 million seconds of thruster time, or about 13 months.
I don't know what the duty cycle is on ion thrusters. Maybe they aren't robust enough to fire for over a year straight?
>The Parker Solar Probe mass is 555kg. An achievable amount of ion thrust is around 0.5N. Thus, running that thruster would accelerate the craft at 0.0009m/s2.
To be precise for 555kg probe you'd need additional 600-800kg of propellant mass and thus run the thruster(s) at about 1.5N thrust using 40-60KW - 250m2 of solar panels - everything is available at the current state of tech.
https://en.wikipedia.org/wiki/Ion_thruster
"A test of the NASA Solar Technology Application Readiness (NSTAR) electrostatic ion thruster resulted in 30,472 hours (roughly 3.5 years) of continuous thrust at maximum power. Post-test examination indicated the engine was not approaching failure.[75][3][4] NSTAR operated for years on Dawn."
To be precise for 555kg probe you'd need additional 600-800kg of propellant mass and thus run the thruster(s) at about 1.5N thrust using 40-60KW - 250m2 of solar panels - everything is available at the current state of tech.
https://en.wikipedia.org/wiki/Ion_thruster
"A test of the NASA Solar Technology Application Readiness (NSTAR) electrostatic ion thruster resulted in 30,472 hours (roughly 3.5 years) of continuous thrust at maximum power. Post-test examination indicated the engine was not approaching failure.[75][3][4] NSTAR operated for years on Dawn."
Ah, fair point.
In that case I have a theory. The extra propellant mass, extra solar panel mass, etc, are all more mass against a small amount of thrust. Every bit of additional mass extends that 1-year timeline, and all the extra stuff is extra things that might go wrong.
So instead of a 7 year mission being reduced to 18 months, we have a 7 year mission reduced to maybe 4 years, but then there's possibly a higher chance of failure.
Balancing three years against failure risk, I could see that falling on one side for some missions, and the other side for others. I'm not surprised that they pick the extra time for some missions. I am surprised that they don't pick the faster option more frequently.
In that case I have a theory. The extra propellant mass, extra solar panel mass, etc, are all more mass against a small amount of thrust. Every bit of additional mass extends that 1-year timeline, and all the extra stuff is extra things that might go wrong.
So instead of a 7 year mission being reduced to 18 months, we have a 7 year mission reduced to maybe 4 years, but then there's possibly a higher chance of failure.
Balancing three years against failure risk, I could see that falling on one side for some missions, and the other side for others. I'm not surprised that they pick the extra time for some missions. I am surprised that they don't pick the faster option more frequently.
The numbers i mentioned give 30km/s in less than 1 year. As far as i see the ion thruster makes sense even for the trips to/from Mars.
You could use a solar sail to project a satellite towards the sun.
How do you sail into the solar wind?
You sail perpendicular to the wind, cancelling your horizontal velocity relative to the sun.
Then gravity crashes you into the sun
Then gravity crashes you into the sun
Just need a triangular sail and some zigzagging.
Tacking doesn't work without water and a keel
Won't the crafts relative motion (relative to desired travel) provide the same effective force as the water+keel?
Perhaps a sacrificial solar mirror that detaches from the main ship.
While the unfolded mirror is pushed moving away from the Sun, it reflects enough light for the smaller main body to accelerate sunward.
While the unfolded mirror is pushed moving away from the Sun, it reflects enough light for the smaller main body to accelerate sunward.
There's a difference between flying directly into the sun as if landing there, and orbiting the sun but so close that the spacecraft is inside the solar atmosphere.
This is doing the latter.
This is doing the latter.
It's actually not too brutal so long as you don't try to do it directly. Launch a craft out past Jool then when you start falling back burn retrograde. It's like the opposite of what you do to efficiently burn when leaving Kerbin.
In real life they used a set of Venus gravity assists instead. This has allowed them to slowly get closer while observing over time instead of a long wait and then one big bang close up before being shot ridiculously far back out.
In real life they used a set of Venus gravity assists instead. This has allowed them to slowly get closer while observing over time instead of a long wait and then one big bang close up before being shot ridiculously far back out.
In SpaceFlight Simulator it’s quite easy IIRC (it’s been a while):
1. Orbit yourself around low earth
2. When entering the transfer window (opposite side of the sun-facing earth, i.e. above midnight longitude) booooost
3. For orbit, aim for tangent with your target. For sun discovery, aim for sun center. Choose but don’t change.
The game is in 2D and you got nice auto-calculated transfert windows and trajectories. Is it one of those game simplification that makes it easy or there’s more difficulties?
1. Orbit yourself around low earth
2. When entering the transfer window (opposite side of the sun-facing earth, i.e. above midnight longitude) booooost
3. For orbit, aim for tangent with your target. For sun discovery, aim for sun center. Choose but don’t change.
The game is in 2D and you got nice auto-calculated transfert windows and trajectories. Is it one of those game simplification that makes it easy or there’s more difficulties?
The math is simple enough, it's just the delta-v requirements are brutal. Or you take the slingshot approach at which point the math requirements are brutal.
And I'm not aware of any KSP mod that helps you plan slingshots. And even if there was a slingshot maneuver requires a lot of precision because your ejection angle is highly sensitive to exactly how close you came.
The Parker probe was sent outward to Jupiter and used it to slingshot away much of it's energy. (We normally think of using a planetary encounter to gain energy but it works both ways. Ejection velocity from a slingshot at Jupiter can be anywhere from hitting the sun to solar escape. It's just most probes are heading out, not in.)
And I'm not aware of any KSP mod that helps you plan slingshots. And even if there was a slingshot maneuver requires a lot of precision because your ejection angle is highly sensitive to exactly how close you came.
The Parker probe was sent outward to Jupiter and used it to slingshot away much of it's energy. (We normally think of using a planetary encounter to gain energy but it works both ways. Ejection velocity from a slingshot at Jupiter can be anywhere from hitting the sun to solar escape. It's just most probes are heading out, not in.)
> And I'm not aware of any KSP mod that helps you plan slingshots
If you're willing to go for the full n-body package, Principia [0] has a pretty nice flight planner that is quite usable for planning more complicated missions.
KSP Trajectory Optimization Tool [1] is a non-mod alternative with some additional capabilities beyond flight planning as well. I think this one is designed for stock gravity so it should be usable in an otherwise vanilla install.
[0]: https://github.com/mockingbirdnest/Principia
[1]: https://github.com/Arrowstar/ksptot
If you're willing to go for the full n-body package, Principia [0] has a pretty nice flight planner that is quite usable for planning more complicated missions.
KSP Trajectory Optimization Tool [1] is a non-mod alternative with some additional capabilities beyond flight planning as well. I think this one is designed for stock gravity so it should be usable in an otherwise vanilla install.
[0]: https://github.com/mockingbirdnest/Principia
[1]: https://github.com/Arrowstar/ksptot
KSP TOT looks like it does help you plan slingshots. I hadn't heard of it before.
> I'm not aware of any KSP mod that helps you plan slingshots.
As someone who played before they added patched conics, I'd consider patched conics such a thing.
As someone who played before they added patched conics, I'd consider patched conics such a thing.
The same gravity that wants to pull you in keeps you in orbit. And any object we launch starts off in the suns orbit.
It's only the v0 you start off with from being in orbit already that makes it hard. Earth (and Kerbin) orbit at a very high speed.
> The same gravity that wants to pull you in keeps you in orbit
I would say it's your velocity that keeps you in orbit. Without the velocity, you fall into the star. Without the star's gravity, you keep going away in a straight line. Any object we launch starts off with Earth's velocity.
I would say it's your velocity that keeps you in orbit. Without the velocity, you fall into the star. Without the star's gravity, you keep going away in a straight line. Any object we launch starts off with Earth's velocity.
It's like a joke I recall from Hitchhiker's Guide to the Galaxy: You are indeed falling towards the ground... but the trick is to miss.
Your lateral velocity is what keeps you missing, whether you want to or not.
Your lateral velocity is what keeps you missing, whether you want to or not.
I don't know if I'm shocked or not shocked that the temperature is 2500F 4 million miles away from the Sun. Part of me expected it to be much much hotter than that, but I guess it is 4 million miles. Considering we are 90 million miles away, and the temperature still gets up to 120F on the Earth, maybe that makes sense?
Depends on the object receiving the heat. Walk outside in bearfoot in summer. You will soon notice some surfaces are way hotter than others. This depends on how efficiently heat can transfer. Convection, radiation, conduction I think are the 3 ways.
The air temp is heated by the sun, those surfaces then the atmosphere is preventing heat escaping. A lot going into that 120F!
That is why things like climate change and urban heat islands don't need a closer sun.
The air temp is heated by the sun, those surfaces then the atmosphere is preventing heat escaping. A lot going into that 120F!
That is why things like climate change and urban heat islands don't need a closer sun.
Indeed. The Moon's surface temperature swings between 250F and -208F and it's essentially the same distance from the Sun as Earth is. The wild swings happen because the Moon has no atmosphere.
https://www.space.com/18175-moon-temperature.html
https://www.space.com/18175-moon-temperature.html
you're probably getting downvoted because there isn't really a temperature 4 million miles away from the Sun (it's mostly just empty space being bombarded by radiation)
2,500º F is merely the temperature the probe is expected to reach at that distance. if it were to stay at that distance indefinitely, it would grow much, much hotter as it absorbed more energy from the sun.
2,500º F is merely the temperature the probe is expected to reach at that distance. if it were to stay at that distance indefinitely, it would grow much, much hotter as it absorbed more energy from the sun.
No not necessarily - it will keep growing hotter until the black body radiation emitted by the probe matches the power of the radiation hitting the probe. Then it will stay at constant temperature.
It's a standard undergraduate problem to work out what this equilibrium temperature is for a flat plate at a distance from the sun equal to the Earth's orbital radius.
Interestingly the result is only a few 10's of degrees less than the average temperature of the real Earth - the difference is due to the Greenhouse Effect.
For the probe one could easily do the maths but I could believe that at 4 million miles that equilibrium temperature is 2,500F.
It's a standard undergraduate problem to work out what this equilibrium temperature is for a flat plate at a distance from the sun equal to the Earth's orbital radius.
Interestingly the result is only a few 10's of degrees less than the average temperature of the real Earth - the difference is due to the Greenhouse Effect.
For the probe one could easily do the maths but I could believe that at 4 million miles that equilibrium temperature is 2,500F.
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i definitely can't do the math myself, but excellent retort. thank you for the nuance
Temperature is so wibbly-wobbly. The probe will reach an equilibrium energy-in vs. energy-out temperature depending on its distance from the sun, its surface area facing the sun, and the materials being lit, vs. its surface area facing away, the thermal radiation rate of various materials, and other factors. You could give an aerospace engineer almost any temperature between the CMB and the surface of the sun and they could probably design a (at least theoretical) probe that would reach that temperature eventually* at almost any distance. My guess is that 2500 ºF probably is the equilibrium temperature of the probe at that distance.
* With "eventually" being "assuming a stable state for infinite years" which is of course not how astrophysics actually works.
* With "eventually" being "assuming a stable state for infinite years" which is of course not how astrophysics actually works.
Eh, not quite yeah?
You’re talking about heat (think ‘amperage’), where temperature is more like voltage.
You can’t get above a specific temperature merely by transferring more heat, or losing less heat, etc.
Upper bounds of temperature is still going to be limited by the temperature/frequency of the input energy, barring energy loss which can reduce it.
The solar atmosphere layers have specific maximum temperatures that limit the maximum temperature of objects exposed to them or the radiation from them.
You’re talking about heat (think ‘amperage’), where temperature is more like voltage.
You can’t get above a specific temperature merely by transferring more heat, or losing less heat, etc.
Upper bounds of temperature is still going to be limited by the temperature/frequency of the input energy, barring energy loss which can reduce it.
The solar atmosphere layers have specific maximum temperatures that limit the maximum temperature of objects exposed to them or the radiation from them.
well, in space (perfect vacuum) you only lose heat to radiation
but you can keep absorbing radiation indefinitely
so the equilibrium temperature will depend on the incoming radiation and ensuing outgoing radiation as dictated by the material makeup of the thingy
but you can keep absorbing radiation indefinitely
so the equilibrium temperature will depend on the incoming radiation and ensuing outgoing radiation as dictated by the material makeup of the thingy
Assuming passive systems? It doesn’t work that way.
Once the object has reached the temperature of the source of the radiation (assuming radiative heat transfer), it reaches equilibrium and it will radiate away at the same rate it is absorbing (as a black body). Per the 2nd law of thermodynamics.
It’s why there is a maximum temperature with concentrated solar too - regardless of magnification, you can’t exceed the temperature of the surface of the sun the light was emitted from. Attempted to do so will actually heat the sun (or some other thing) through radiative thermal heat transfer the other direction.
It’s also why radiative heat transfer can’t be used to produce infinitely high temperatures by having a large emitter near a tiny absorber (like a speck of dust) in a vacuum.
If there is some kind of heat pump or laser or the like which you a providing power, then that doesn’t apply of course, but for pure black bodies it does.
If you have some way to let an object absorb radiation, while emitting no radiation even when it is as hot as the source of that radiation, then you have something pretty special going on eh?
Once the object has reached the temperature of the source of the radiation (assuming radiative heat transfer), it reaches equilibrium and it will radiate away at the same rate it is absorbing (as a black body). Per the 2nd law of thermodynamics.
It’s why there is a maximum temperature with concentrated solar too - regardless of magnification, you can’t exceed the temperature of the surface of the sun the light was emitted from. Attempted to do so will actually heat the sun (or some other thing) through radiative thermal heat transfer the other direction.
It’s also why radiative heat transfer can’t be used to produce infinitely high temperatures by having a large emitter near a tiny absorber (like a speck of dust) in a vacuum.
If there is some kind of heat pump or laser or the like which you a providing power, then that doesn’t apply of course, but for pure black bodies it does.
If you have some way to let an object absorb radiation, while emitting no radiation even when it is as hot as the source of that radiation, then you have something pretty special going on eh?
Edit window closed, but here is a more in-depth explanation. It’s decidedly non-obvious [https://www.reddit.com/r/AskPhysics/comments/1arh55g/why_can...]
Part of it is due to the ‘Principle of Etendue’ [https://en.m.wikipedia.org/wiki/Etendue#Conservation]
What confuses people I think (practically) is that the actual high temperature (~4500F) is far beyond the limits of a useful highest temperature in 99% of situations we might want in engineering. A spacecraft hitting that temperature is going to be a molten piece of scrap long before it hits that point.
But the limit does actually exist - it won’t somehow hit 10,000F for instance. That is also why we can’t produce infinitely high temperatures with a huge magnifying glass - the highest we can hit, regardless of how big it is, is still ~ 4500F. Higher temperatures need something like an electric arc furnace, or LASER.
Part of it is due to the ‘Principle of Etendue’ [https://en.m.wikipedia.org/wiki/Etendue#Conservation]
What confuses people I think (practically) is that the actual high temperature (~4500F) is far beyond the limits of a useful highest temperature in 99% of situations we might want in engineering. A spacecraft hitting that temperature is going to be a molten piece of scrap long before it hits that point.
But the limit does actually exist - it won’t somehow hit 10,000F for instance. That is also why we can’t produce infinitely high temperatures with a huge magnifying glass - the highest we can hit, regardless of how big it is, is still ~ 4500F. Higher temperatures need something like an electric arc furnace, or LASER.
Soundtrack for appropriate ambiance.
https://music.youtube.com/watch?v=ZnIxWznakz8&si=jhjMURGD4S0...
https://music.youtube.com/watch?v=ZnIxWznakz8&si=jhjMURGD4S0...
I was thinking about Red Dwarf theme: https://youtu.be/zV0hwZwNQZc?si=NcQULlVtqBX_V7wm
”It's cold outside
There's no kind of atmosphere
I'm all alone
More or less
Let me fly
Far away from here
Fun, fun, fun
In the sun, sun, sun”
”It's cold outside
There's no kind of atmosphere
I'm all alone
More or less
Let me fly
Far away from here
Fun, fun, fun
In the sun, sun, sun”
Soundtrack to "Sunshine" also seems very appropriate.
https://www.youtube.com/watch?v=AXzqJucLae8
https://www.youtube.com/watch?v=AXzqJucLae8
I was thinking about Adagio in D Minor, because of Sunshine (2007).
You could also go with this: https://www.youtube.com/watch?v=juq0_2Oj5qw
Came here to post exactly this. Mainly for the sample of Jo'Bril, obviously.
Came here looking for this. :)
Imagine the Sun as a ball 1 mile in diameter. If you flew a probe by the Sun that never got closer than 4 miles away (4 diameters) would you describe it as "into the Sun?"
Neither would I.
Sure, it's close enough to get very hot. But it's not into the sun.
Neither would I.
Sure, it's close enough to get very hot. But it's not into the sun.
I think NASA is saying it's already gone well inside the Alfvén surface and so that qualifies as basically "into the suns atmosphere."
[1] https://en.wikipedia.org/wiki/Alfvén_surface
[1] https://en.wikipedia.org/wiki/Alfvén_surface
I would argue that is also most “into the sun” we can reasonably get.
Related. Others?
What NASA's Parker Solar Probe discovered in its first 5 years looping the sun - https://news.ycombinator.com/item?id=37128838 - Aug 2023 (1 comment)
A NASA probe has touched plasma and gas that belongs to the sun - https://news.ycombinator.com/item?id=29965805 - Jan 2022 (31 comments)
NASA’s Parker Solar Probe Is Unlocking the Sun’s Mysteries - https://news.ycombinator.com/item?id=21709598 - Dec 2019 (2 comments)
Traveling to the Sun: Why Won’t Parker Solar Probe Melt? - https://news.ycombinator.com/item?id=17743599 - Aug 2018 (121 comments)
Traveling to the Sun: Why Won't Parker Solar Probe Melt? - https://news.ycombinator.com/item?id=17569741 - July 2018 (86 comments)
What NASA's Parker Solar Probe discovered in its first 5 years looping the sun - https://news.ycombinator.com/item?id=37128838 - Aug 2023 (1 comment)
A NASA probe has touched plasma and gas that belongs to the sun - https://news.ycombinator.com/item?id=29965805 - Jan 2022 (31 comments)
NASA’s Parker Solar Probe Is Unlocking the Sun’s Mysteries - https://news.ycombinator.com/item?id=21709598 - Dec 2019 (2 comments)
Traveling to the Sun: Why Won’t Parker Solar Probe Melt? - https://news.ycombinator.com/item?id=17743599 - Aug 2018 (121 comments)
Traveling to the Sun: Why Won't Parker Solar Probe Melt? - https://news.ycombinator.com/item?id=17569741 - July 2018 (86 comments)
This article is about 3 years late, Parker first flew through the Sun's atmosphere in 2021. This is its closest approach but definitely not the first time it's doing it.
Out of curiosity, what is the relationship between 430,000 mph and the speed of impulse power on Star Trek? I assume Parker Solar Probe is way slower, but what are we talking?
Apparently, full impulse is relative to the engine spec. For the Voyager, it is 0.25c, so about 167 million mph.
Edit: https://memory-alpha.fandom.com/wiki/Impulse_engine
Edit: https://memory-alpha.fandom.com/wiki/Impulse_engine
Look at this NASA animation of two solar probes orbiting the Sun (thanks
ostacke and DiggyJohnson):
https://svs.gsfc.nasa.gov/3966/
One probe, Parker I assume, goes through all the planetary flybys to achieve its solar orbit. The other just drops into an even closer solar orbit. Why not do that for both probes?
https://svs.gsfc.nasa.gov/3966/
One probe, Parker I assume, goes through all the planetary flybys to achieve its solar orbit. The other just drops into an even closer solar orbit. Why not do that for both probes?
The Parker solar probe gets much closer than the solar orbiter, 0.046 AU vs 0.28 AU respectively. The successive Venus flybys are to drop it increasingly further into the sun's orbit to take solar atmospheric data on quick flybys while the Solar orbiter is more for spectrograph measurements of the sun's corona, just different mission sets.
You can't "just drop", it requires energy (fuel) and that's probably the answer why.
Yeah, it's going to get pretty hot. Scientists estimate that the probe's heat shield will endure temperatures in excess of 2,500° Fahrenheit (1,371° C) on Christmas Eve, which is pretty much the polar opposite of the North Pole.
That's the South Pole. I wasn't aware global warming has gotten that bad yet.
That's the South Pole. I wasn't aware global warming has gotten that bad yet.
Rather frustrating to read - as if intentionally written for nine year-olds. I was surprised to see it was Eric Berger, I don’t recall this affected style from him before, though I’ve not paid close attention.
This reminds me of an old joke about a guy known for being particularly foolish (often a member of a specific group, like a military unit). He tells someone he plans to travel to the Sun in a spaceship. When the other person points out, "You can’t do that - you’d die from the extreme heat before even getting close" the first guy replies, "I'm not stupid! I'll go at night!"
very cool indeed, looking forward to see how the results pan out from this project.
Of course it is completely evaporated before hitting anything that remotely resembles a surface.
To be clear, it's not the end of the mission as far as I'm aware. It will come around again and do 4 more sun flybys next year.
No if they go during the night
Is there even a surface?
Yes, if you zoom out enough you see it. Like with ordinary objects.
Most ordinary objects have the property that the density of object mass has a very sharp gradient near some 2d surface that encloses a compact domain, and outside that is close to 0. However not identically 0, since eg the object is constantly releasing vapor of atoms of itself. If you zoom out enough out out of anything it looks like that, depending on how sharp you wish the gradient to be to call it a "surface".
For objects where the gradient at the boundary is not great relative to our size we would subjectively experience no surface when coming close eg to a cloud.
Does a galaxy have a "surface"? We can often also "clearly see" the edge of it...
For objects where the gradient at the boundary is not great relative to our size we would subjectively experience no surface when coming close eg to a cloud.
Does a galaxy have a "surface"? We can often also "clearly see" the edge of it...
How do you define density?
Really? I suspect this is a troll but, in the static case, roughly the ratio of volume of space to how much gravitational force said volume applies on other objects. Extrapolate correctly for qm/gr - thats an exercise left for the reader.
Depending on your scales etc you may wish to group different things into the category of “object”, eg a car would likely be be selected as a valid grouping of atoms as an object by most people in conversation wheres it is mostly empty space at the micro level, and has a bunch of very different densities (many oom) at diff volumes even at the macro scale (eg the air in the trunk vs the engine block).
Depending on your scales etc you may wish to group different things into the category of “object”, eg a car would likely be be selected as a valid grouping of atoms as an object by most people in conversation wheres it is mostly empty space at the micro level, and has a bunch of very different densities (many oom) at diff volumes even at the macro scale (eg the air in the trunk vs the engine block).
The photosphere is the visible surface of the Sun that we are most familiar with. Since the Sun is a ball of gas, this is not a solid surface but is actually a layer about 100 km thick (very, very, thin compared to the 700,000 km radius of the Sun).
https://solarscience.msfc.nasa.gov/surface.shtml
https://solarscience.msfc.nasa.gov/surface.shtml
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It would be nice if the public could see the data/images directly in real time, not this curated drivel they feed us.
Set the controls.
It's not very hot if you go at night.
Your comment gives me faith in humanity.
Well played!
Well played!
For those of you that are worried the ship is going to burn up, the team does have a plan: they’re going to do the mission at night.