h a l f b a k e r yOh yeah? Well, eureka too.
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so, we have landed on and flown past many planets and
yet, don't have much to show for anything but mars.
so i was realizing what with the failure of our last comet
lander mission-------------why not bring back NUCLEAR
BATTERIES instead of solar panels.
which then, made me realize one simple
thing, the cold
side of mercury is more than reasonable for a planetary
lander to land on and then study.
more importantly, on the dark side, shielded from the suns
intense rays, the lander would have to MOVE to avoid being
roasted. fortunately a day on mercury lasts 1400 hours.
and because mercurieis circumfrence is between 9400 and
9600 miles, this means a lander would have to average
near 6.8 miles per hour at all times to stay in permenent
darkness as the days past.
even while the lander takes breaks to study, a lander
capable of doing 10-12 miles an hour ------powered by a
nuclear battery, could keep itself warm and powered ,
with power for LED's and other electronics.
the best part of this mission is that the lander could dig up
things and then come back to them after they've been
roasted 'overday' when the nighttime falls again. in this
vain, the lander could actually study the effects of
mercurian sunshine on newly exposed mercurian soil.
existing missions to mercury
http://en.wikipedia...Observation_history
[teslaberry, Feb 02 2015]
24/7 solar power
Lunar_20Rail_20Dist...ed_20Infrastructure
[FlyingToaster, Feb 03 2015]
Mercury orbit/rotation
http://sciencenetli.../OrbitRotation.html
[tatterdemalion, Feb 03 2015]
Mercury 2.0
Mercury_202_2e0_20(the_20planet)
This baker got very enthusiastic about the prospect. Right down to the username. [bungston, Feb 03 2015]
[link]
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I don't think most nuclear batteries have enough
power output to move themselves around at
7mph. And if the rover gets behind and gets
caught in the daylight, I think the 427 deg C
temperatures are likely to kill a lot of your
electronics. |
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If you land near one of the pole, it's quite cold (-93
C) day long, so there ought to be someplace just a
bit closer to the equator that has usable
temperatures during the day, and survivably cold
nights. Your unconventional idea of
circumnavigating the planet to maintain the
proper temperature would be much more doable
at a high latitude as well. |
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Nice idea, but on the other hand, if there ever was a planet
where solar power packs some punch, it would be Mercury. |
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Shielding a lander from IR and visible radiation can be done
surprisingly effectively using a clever bit of technology called a"
mirror". |
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If the vehicle is close to the terminator, as the sun rises it can
harvest enough solar energy via PV panels to scuttle back into
the shadows - essentially a robotic cockroach. |
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Besides, Mercury's a dump. You've been to your moon? Well,
Mercury's about the same, just a bit more gravity. |
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//
Besides, Mercury's a dump |
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This idea would be half-baked until it fails. |
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A mirror could keep out the direct sunlight, but
when you have 88 days of continuous heat, the
ground nearby is going to heat up, and it is going
to conduct to the ground under the mirrors and
through the wheels of the rover. You may have
some pretty good insulation to slow down the
conduction, but it won't keep it cool that long. |
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Although... is there a photo-voltaic technology
that can withstand that heat? If so, maybe you
could use a heat pump to keep critical
components cool while using mirrors and insulation
to reduce the load on the heat pump, but you'd
need a very good heat pump to handle that
temperature difference. |
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//unconventional idea of circumnavigating |
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Actually that one has cropped up in an SF story, can't
remember exactly, but possibly some power-station
on tracks on the moon, perpetually in sunlight... |
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//SF story// An HB post, mine in fact :) I wrote and rewrote and deleted and reposted ... and it still looks like crap, but the idea's there <link>. |
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[edit: and another one: "Terminator Lunar Colony" by [simonj] ] |
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Mercury is not actually tide-locked to the Sun; most places on its surface experiences a day/night cycle. Only at the poles can you find places (craters) that might be permanently in shadow. |
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// why not bring back NUCLEAR BATTERIES instead of solar panels. |
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Bring back? They never stopped using them. Radioisotope thermoelectric generators are onboard Mars Curiousity and the New Horizons Pluto probe. |
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[Vernon] Mercury is gravitationally locked in a sort of 3:2 orbit/rotation ratio. As such a Mercury day is about two Mercury years long. [edit: this is wrong, see correction below]. So all surfaces except extreme polar regions face the sun over the course of that time. |
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You vastly overestimate the technological feasibility of a
rover capable of going around Mercury |
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It doesn't have to be autonomous. |
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Satellite mapping will allow a route to be pre-planned. Combined
with feedback imagery from the rover, navigation won't be too
difficult, providing a viable route exists. |
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//Radioisotope thermoelectric generators are onboard
Mars Curiousity and the New Horizons Pluto probe// |
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Wot he said. Solar panels are super cheap and light if you
consider how much energy you can get out of them on
the scale of years. Especially when you don't put a whole
lot of atmosphere in the way. |
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// Mercury is gravitationally locked in a sort of 3:2
orbit/rotation ratio.// |
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May I suggest Sturmey archer as the prime sponsor...? |
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Could possibly land in the dark and have enough time to dig a
hole to hide from the sun when needed. Do your exploring in
the dark. |
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My take on this was to use nukes to generate wave amplification retarding rotation to the point where Mercury becomes tidally locked. Mine half the planet in the shade, then flip it around again and mine the other half. |
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How will a shock wave stop the planet's spin? |
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Only way to find out is to try it. |
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Now I have a nagging suspicion [8/7] will stop
Mercury's rotation and actually nudge it out of orbit,
colliding it with Earth on a fine Sunday morning. |
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He will be standing in your front yard, reciting
horrible poetry, when it occurs. |
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//How will a shock wave stop the planet's spin?// |
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Not 'a' shock wave, many directional shock waves timed to amplify, and we don't need to stop the planet's spin... just tilt one of its poles to face the sun. Maybe tidally locked is not the right term for this. |
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Given a large enough 'lever' located close enough to the center of the planet we could rotate a planet's poles within a single revolution. I call it gyroscillation. |
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// why not bring back NUCLEAR BATTERIES instead of solar
panels. |
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They never left; many space missions use them right now.
The reason that Philae didn't use one is entirely down to ESA
politics (and scarcity of the plutonium isotope that RTGs use) |
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// a Mercury day is about two Mercury years long. |
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Self-correction - I got the math wrong on that 3:2 thing. It's actually a Mercury year lasts a Mercury day and a half. |
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// Now I have a nagging suspicion [8/7] will stop Mercury's rotation and actually nudge it out of orbit, colliding it with Earth on a fine Sunday morning. // |
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Not us. Q might do that, but not us. You humans are far too good entertainment to kill you all off. |
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// He will be standing in your front yard, reciting horrible poetry, when it occurs. // |
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Don't diss our poetry, man. |
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// scarcity of the plutonium isotope // |
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= reluctance to bow the knee to the Yanks or the Ivans. |
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//Self-correction - I got the math wrong on that 3:2
thing. It's actually a Mercury year lasts a Mercury day and
a half.// |
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No, you were right the first time. Mercury completes
three full revolutions (with respect to an outside
observer standing above the ecliptic) every two (Mercury)
years. However it's also completing two full orbits every
two years, which subtracts from that count. Therefore
it only gains one full revolution every two years. So it's
day is 176 (earth) days long, and it's year is 88. |
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Now I'm confused, and it sounds like you're agreeing with me. |
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According to the diagram I linked, it appears Mercury does one full rotation on its axis in about 58 earth days, about two-thirds of a Mercury year. |
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But that doesn't mean every point on the surface has been exposed to the sun. Seems like it takes about one and a third solar orbits for that to occur. I guess that's the only factor relevant to this idea. |
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I think you're right [MechE] but I'm not sure I'm wrong, I probably am. I was right once though. |
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(Just did some checking and it seems the 58-and-change earth days per Mercury day is correct, not 176.) |
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Nope. It's definitely 176. The key thing here is that a full
rotation of the planet (your 58.6 days) is not a full day.
Mercury rotates on it's axis 1/2
way
over 1/3 of it's orbit. But since the two are in the same
direction, only 1/6th of the planet is newly exposed to
sunlight (the orbit subtracts from the rotation). |
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This is
the same reason why the same side of the moon always
faces us. It rotates 1 full rotation in 1 full orbit, and
when you subtract the two, you get zero relative change
to the earth. |
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In order for the same meridian on Mercury to reach the
same position relative to the sun ( a full day), Mercury
must make 6/3rds of an orbit, or two complete orbits. |
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Look at your own link and see how many complete orbits
it takes before the one and the two are in the same
orientation relative to the sun (NOT the screen, which
does happen at the 2/3 point). |
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I think the confusion stems from what definition of "day" we're using. |
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I'm referring to a complete rotation around its own axis, a sidereal day, which for Mercury is ~58 earth days. I think you're talking about a solar day, a complete rotation relative to the sun - which granted is a mess to figure out for Mercury, but is indeed 176 earth days. |
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But yes, the solar day is really the number we're looking for here, as regards the idea. |
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<at the post office>I'd like to send this parcel to Norfolk, how many days do you think it will take?
<clerk>Solar days or sidereal days sir? |
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Yeah, day means solar day. Sidereal days only exist because
the astronomers were to lazy to make up their own word. |
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// I'd like to send this parcel to Norfolk, how many days do you think it will take? // |
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You have to allow for the time difference - when it's 1200 hrs GMT in London, it's only 1156AD in Norfolk ... |
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