[HN Gopher] The Parker Solar Probe will make its closest approac...
___________________________________________________________________
The Parker Solar Probe will make its closest approach yet to the
Sun
Author : pseudolus
Score : 157 points
Date : 2024-12-20 11:23 UTC (1 days ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| pavel_lishin wrote:
| > _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.
| zomg wrote:
| 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!
| Ancalagon wrote:
| 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?
| tifik wrote:
| 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.
| floxy wrote:
| You should be able to tilt your mirror/sail at 45deg, 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?
| emilamlom wrote:
| 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.
| pavel_lishin wrote:
| 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.)
| josho wrote:
| 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.
| andrewaylett wrote:
| 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.
| UniverseHacker wrote:
| 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.
| emilamlom wrote:
| 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.
| happytoexplain wrote:
| 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.
| GauntletWizard wrote:
| 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.
| pavel_lishin wrote:
| 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!
| adolph wrote:
| Thats improv, not standup; granted, one must be agile
| either way.
| Heliosmaster wrote:
| Scrum standup, not comedy...
| gosub100 wrote:
| 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.
| strongpigeon wrote:
| 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.
| daveslash wrote:
| 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.
| Filligree wrote:
| You'll want a bi-elliptic transfer orbit. And probably a
| larger rocket.
| LorenPechtel wrote:
| I would suspect that a slingshot at Jool would do it but
| I've never tried.
| vikingerik wrote:
| 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.
| imglorp wrote:
| 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!
| LorenPechtel wrote:
| 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.
| hnuser123456 wrote:
| It sounds like for large changes in orbit, a bi-elliptic
| transfer can beat Hohmann:
| https://news.ycombinator.com/item?id=42357272
| maximilianburke wrote:
| Plane change maneuvers are expensive
| buildsjets wrote:
| Soundtrack for appropriate ambiance.
|
| https://music.youtube.com/watch?v=ZnIxWznakz8&si=jhjMURGD4S0...
| Qem wrote:
| I was thinking about Adagio in D Minor, because of Sunshine
| (2007).
| grecy wrote:
| Soundtrack to "Sunshine" also seems very appropriate.
|
| https://www.youtube.com/watch?v=AXzqJucLae8
| vardump wrote:
| 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"
| hinkley wrote:
| They don't literally mean _in_ the sun.
| lizzas wrote:
| They mean Fiji
| wormius wrote:
| Came here looking for this. :)
| koops wrote:
| You could also go with this:
| https://www.youtube.com/watch?v=juq0_2Oj5qw
| zimpenfish wrote:
| Came here to post exactly this. Mainly for the sample of
| Jo'Bril, obviously.
| amelius wrote:
| Of course it is completely evaporated before hitting anything
| that remotely resembles a surface.
| detritus wrote:
| Is there even a surface?
| amelius wrote:
| Yes, if you zoom out enough you see it. Like with ordinary
| objects.
| shwouchk wrote:
| 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...
| amelius wrote:
| How do you define density?
| shwouchk wrote:
| 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).
| amelius wrote:
| I mean, how do you select the volume to sample over?
| shwouchk wrote:
| You look at that wierd bright thing going baaaaaam for
| millions of years nonstop and decide you would like to
| know some stuff about it? ;-)
| adolph wrote:
| _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
| alnwlsn wrote:
| 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.
| ceritium wrote:
| No if they go during the night
| alnwlsn wrote:
| _Yeah, it 's going to get pretty hot. Scientists estimate that
| the probe's heat shield will endure temperatures in excess of
| 2,500deg Fahrenheit (1,371deg 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.
| blindriver wrote:
| 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?
| thisisbrians wrote:
| 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.
| tomnicholas1 wrote:
| 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.
| feoren wrote:
| 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.
| lazide wrote:
| 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.
| lizzas wrote:
| 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.
| dreamcompiler wrote:
| 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
| FredPret wrote:
| If KSP is to be believed, this is shockingly difficult to do
| lizzas wrote:
| The same gravity that wants to pull you in keeps you in orbit.
| And any object we launch starts off in the suns orbit.
| FredPret wrote:
| 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.
| feoren wrote:
| > 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.
| Terr_ wrote:
| 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.
| beAbU wrote:
| 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.
| FredPret wrote:
| 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.
| JumpCrisscross wrote:
| > _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.
| anigbrowl wrote:
| 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.
| nostromo wrote:
| You could use a solar sail to project a satellite towards the
| sun.
| Jeff_Brown wrote:
| How do you sail _into_ the solar wind?
| tedunangst wrote:
| Just need a triangular sail and some zigzagging.
| mtreis86 wrote:
| Tacking doesn't work without water and a keel
| dan_linder wrote:
| Won't the crafts relative motion (relative to desired
| travel) provide the same effective force as the
| water+keel?
| gpm wrote:
| You sail perpendicular to the wind, cancelling your
| horizontal velocity relative to the sun.
|
| Then gravity crashes you into the sun
| Terr_ wrote:
| 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.
| trhway wrote:
| >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.
| margalabargala wrote:
| 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?
| trhway wrote:
| >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."
| margalabargala wrote:
| 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.
| aziaziazi wrote:
| 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?
| LorenPechtel wrote:
| 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.)
| lmm wrote:
| > 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.
| aw1621107 wrote:
| > 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
| kccqzy wrote:
| 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.
| ostacke wrote:
| 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/
| DiggyJohnson wrote:
| 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.
| zamadatix wrote:
| 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.
| kfogel wrote:
| 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.
| verzali wrote:
| Pretty sure it's 0.064%, not sure why the article got it wrong,
| still impressive though
| caseyohara wrote:
| Still. ~200,000 m/s (= ~430,000 mph) is unfathomably fast.
| jebarker wrote:
| 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.
| tehjoker wrote:
| Light loops around the earth ~7.75x a second iirc so a
| few orders of magnitude less makes sense
| sandworm101 wrote:
| 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.
| gosub100 wrote:
| 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.
| andrehacker wrote:
| >> The great arc distance from LA to Sydney is just over
| 12km.
|
| 12,000km ?
| gosub100 wrote:
| fixed, thank you
| jebarker wrote:
| 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?
| irrational wrote:
| 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.
| Ankaios wrote:
| _~200,000 m /s is unfathomably fast._
|
| It's about 110,000 fathoms per second.
| fy20 wrote:
| Or if you prefer leagues, at that speed it would still
| take 9 minutes to reach the depth in Jules Verne's book.
| mwcremer wrote:
| The title refers to the distance the _Nautilus_ traveled
| while submerged, not the depth it reached.
| MereInterest wrote:
| 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.
| Loughla wrote:
| Yeah he really needed a comma.
|
| 20,000 Leagues, Under the Sea
|
| I think it reads cleaner.
| kristianc wrote:
| It weighs half a ton. Getting it to even 10% of the speed of
| light would take more energy than is produced by the world in a
| year.
| bagels wrote:
| It wouldn't be in orbit of the sun anymore
| ck2 wrote:
| 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.
| verzali wrote:
| 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.
| curtisblaine wrote:
| 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!"
| abecedarius wrote:
| https://www.poetryfoundation.org/poems/43914/the-walrus-and-...
| rufus_foreman wrote:
| Set the controls.
| adregan wrote:
| 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?
| bc569a80a344f9c wrote:
| 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
| lqueenan wrote:
| Reminds me of this far side comic,
| https://static1.srcdn.com/wordpress/wp-content/uploads/2023/...
| throwaway657656 wrote:
| I don't get the Far Side. Could a Cliff Clavin chime in ?
| danparsonson wrote:
| 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...
| tgv wrote:
| 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."
| QuantumGood wrote:
| Those only smart enough to think of our local star as "Mr
| Sun" perhaps should not be piloting craft in its vicinity.
| nick3443 wrote:
| Children's song lyrics I heard growing up.
|
| Sun, sun, Mr. Golden sun, sun shine down on me.
| fortran77 wrote:
| Can't they just go at night?
| ordu wrote:
| At night there is no corona, nothing to look at.
| dreamcompiler wrote:
| 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_.
| ozim wrote:
| I would argue that is also most "into the sun" we can
| reasonably get.
| dang wrote:
| 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)
| mmooss wrote:
| 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?
| Hextinium wrote:
| 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.
| rplnt wrote:
| You can't "just drop", it requires energy (fuel) and that's
| probably the answer why.
| spacesanjeet wrote:
| very cool indeed, looking forward to see how the results pan out
| from this project.
| ballooney wrote:
| 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.
| everdrive wrote:
| 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.
| d754903977 wrote:
| It's not very hot if you go at night.
| MR4D wrote:
| Your comment gives me faith in humanity.
|
| Well played!
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