Landing on Mercury on equator at perihelion |
Landing on Mercury on equator at perihelion |
Mar 21 2006, 12:18 AM
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#1
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Junior Member Group: Members Posts: 40 Joined: 20-March 06 Member No.: 720 |
How will it be to make a manned landing at Mercury at its closest to the sun (perihelion) on its equator when the sun is in the zenith ,what are the dangers of a landing then? Do we need to be protected against the sunheat and radiation then? How strong is the heat and radiation of the sun then ,and is it dangerous when the solaractivity is high then? What kind of spacesuits do we need then? Better protected suits than we have used on the apollo moonlandings i think. Can you explain how a landing on Mercury will be when it is at perihelion and land on its equator with the sun directly overhead? I hope it will ever happen. Lets start discuss about it.
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Guest_BruceMoomaw_* |
Mar 21 2006, 04:25 AM
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#2
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Guests |
A manned landing on Mercury at perihelion -- or an unmanned one, for that matter -- would be difficult as Hell (which may be appropriate). The problem wouldn't be as severe as that on a Venus lander, but it would be plenty hard -- you would not only need to have an extremely efficient reflecting shield to fend off the heat radiation from the Sun, but also another to deal with that being reflected and emitted from Mercury's surface. (This, in fact, is one reason why the Messenger orbiter will be put into a highly elliptical orbit around Mercury: to give it time to cool off again from each of its low-altitude periapses over Mercury's surface.) As for the design of any EVA walking suit that could cope with that heat: I shudder even to think about the problem. The high-energy particle radiation and X rays from the Sun at that range would also pose a very difficult problem for any manned mission that close to the Sun -- we'll have enough danger from those during long-duration manned trips to Mars and near-Earth asteroids.
However, temperature-wise, there are plenty of other places that either an unmanned or manned lander could touch down on Mercury that would be a cinch. Its near-polar regions are quite tolerably cool -- which is why it has ice as its poles -- and its nightside very quickly cools down after sunset, stays cold, and even stays within modest temperature ranges for a short time after sunrise again. A polar or nightside landing on Mercury is entirely feasible with the technology we have right now. The trouble, as usual, is simply money. Europe's BepiColombo, which consists of a large and low-altitude European orbiter and a small secondary Japanese one for magnetospheric studies, was originally also supposed to include a very small lander to touch down within about 3 degrees of the pole -- but, since Mercury is an airless world with a gravity field considerably stronger than the Moon's (and therefore requiring a larger mass of braking fuel), in the end the cost and mass of the lander was just too much for ESA's already-strained budget to endure and they cut it out of the mission. At some point it certainly will be done by someone; Mercury's surface almost certainly looks almost indistinguishable from the Moon's, but there are a great many interesting geophysical and compositional instruments they could land there on even a single lander. But that's likely to be a couple of decades off (at least), just for monetary reasons. |
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Mar 21 2006, 10:02 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
A polar or nightside landing on Mercury is entirely feasible with the technology we have right now. [...] At some point it certainly will be done by someone; Mercury's surface almost certainly looks almost indistinguishable from the Moon's, but there are a great many interesting geophysical and compositional instruments they could land there on even a single lander. But that's likely to be a couple of decades off (at least), just for monetary reasons. A good bang-for-the-buck mission might avoid a high-latitude constraint by making a night landing and carrying a strobe light for imaging the vicinity. Because the surface will not cool immediately after sundown, it would be best not to land in daytime just before sunset. To allow a mission plenty of duration for seismic (or, alternately, lifetime for a rover), it could land about 10-20% of the way into local night, study the vicinity for about 45 days (night on Mercury is 54 Earth days), and then get a sunrise panorama of the background before sunlight cooks the craft. Another approach would come from the unique fact that the Sun shows retrograde motion on Mercury because the revolution at perihelion overtakes the rate of rotation. A carefully-targeted lander could alight somewhere that was in night, then experienced a very brief "day" of a sunrise-then-sunset. So long as the engineering team could set the lander down precisely, the length of that day could be arbitrarily brief, and a rotatable "parasol" could mean that the craft would take no direct solar heating while the ground would experience only trivial heating in the short run. A lander aimed at just the right longitude could thus experience a short sol (for imaging) and go on to run other studies during a few more Earth days of nighttime before a longer sol cooked the craft. And of course, there is the polar option. Conceivably, a lander could be sent into an area of eternal night, and never face a thermal constraint at all (except during cruise), but such a landing site would be idosyncratic (and therefore interesting, but differently interesting than just a generic Mercury landing site). |
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Guest_BruceMoomaw_* |
Mar 21 2006, 11:57 PM
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#4
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Guests |
A good bang-for-the-buck mission might avoid a high-latitude constraint by making a night landing and carrying a strobe light for imaging the vicinity. Because the surface will not cool immediately after sundown, it would be best not to land in daytime just before sunset. To allow a mission plenty of duration for seismic (or, alternately, lifetime for a rover), it could land about 10-20% of the way into local night, study the vicinity for about 45 days (night on Mercury is 54 Earth days), and then get a sunrise panorama of the background before sunlight cooks the craft. Another approach would come from the unique fact that the Sun shows retrograde motion on Mercury because the revolution at perihelion overtakes the rate of rotation. A carefully-targeted lander could alight somewhere that was in night, then experienced a very brief "day" of a sunrise-then-sunset. So long as the engineering team could set the lander down precisely, the length of that day could be arbitrarily brief, and a rotatable "parasol" could mean that the craft would take no direct solar heating while the ground would experience only trivial heating in the short run. A lander aimed at just the right longitude could thus experience a short sol (for imaging) and go on to run other studies during a few more Earth days of nighttime before a longer sol cooked the craft. And of course, there is the polar option. Conceivably, a lander could be sent into an area of eternal night, and never face a thermal constraint at all (except during cruise), but such a landing site would be idosyncratic (and therefore interesting, but differently interesting than just a generic Mercury landing site). I already thought of Idea #1. (Pause for misguided snickers from Alex.) If you want to set up a good multiple-lander seismic network on Mercury -- and a mission with several tiny Mercury landers, which could be very productive scientifically, is on the Decadal Survey's list of longer-range New Frontiers candidates -- then just putting two seismometers at the poles, although they could survive indefinitely there, would be lousy for trying to locate seismic events on the planet. You'd want a third lander (or maybe just a second one) at low latitude, and the only way to get that would be the nighttime lander plan. (Also keep in mind that, given today's instruments, any searchlight that a nighttime lander needed for photos and near-IR maps could be very low-powered -- Huygens' was about as strong as a nightlight. But, to the extent that the payload of a Mercury lander would be seriously limited by mass and data rate, the very first thing I'd throw out would be the camera. It's good for PR, but low-value for science.) As for the polar landing: except for the possibility that it might be able to study one of the polar ice (or sulfur) deposits, there's nothing particular unusual geologically about Mercury's poles -- which made them the perfect spot for the ESA's planned first-time Mercury lander. Clarke also wrote an SF story in the 1950s about astronauts who land in the "Twilight Zone" of Mercury - back when its day was still thought to equal its year of 88 Earth days. I can recall their encounter with a spindly crab-like creature that caught prey and defended itself by throwing rocks. It threw a rock at one of the astronauts, puncturing his spacesuit and causing a scramble back to the ship. Yeah, that was his Winston kids' SF novel "Islands in the Sky". Poor Arthur -- the Solar System has turned out to be SO much less interesting than he hoped it would be. (Note, though, that the guy whose suit was damaged -- with the result that his legs froze solid and had to be amputated -- then happily made a life for himself on a space station, since legs are actually something of an encumberance in 0-G. That idea has been floating around in the SF world ever since, usually in connection with genetic engineering of humans. As Jack Vance points out, obese people would also be a lot happier living in orbit.) While we're on the subject of misguided SF predictions about Mercury, the prize-winner surely has to be Larry Niven's very first SF story, "The Coldest Place", in which the same two astronauts we'd later meet in "Becalmed in Hell" have just landed triumphantly on "the coldest place in the Solar System", and encountered a helium II-based lifeform. The story neatly suckers the reader into assuming that they're on Pluto, until the last sentence reveals it to be the permanent nightside of Mercury instead. Poor Niven got this story published exactly three months before the radar discovery that Mercury's rotation was not synchronous. |
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