Spacecraft Buzzes By Mercury 62
Riding with Robots writes "The robotic spacecraft MESSENGER is making its second fly-by of the first planet today, skimming just 200 kilometers above the surface. The fly-by will reveal portions of the planet that have never been seen before, but the main purpose of the maneuver is to prepare for an orbital insertion in 2011. The mission site offers extensive information, along with the first pictures that are already arriving on Earth, with many more expected in the coming hours and days."
Re:Buzzed by my anus (Score:4, Funny)
Re:Buzzed by my anus (Score:5, Funny)
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Re:Buzzed by my anus (Score:5, Funny)
That's because they didn't want to have to rename the company to "Whores Galactic".
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How about Mirgin Galactic, if you use a font where the M looks like the special place on a woman + her legs? :)
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No, that's because no one deserves to be a Zero-G Jizz-Mopper.
Comment removed (Score:5, Interesting)
Re:The coldest place (Score:4, Informative)
Some areas in the polar regions of Mercury (deep crater floors) may be permanently shadowed and hence very cold. Similarly to some areas on the Moon poles. This is due to the very low obliquity of the planet. This was discovered by radar studies done from Arecibo, which had anomalously high signal return in some restricted polar regions. This will answered most definitely by MESSENGER itself when it gets into orbit in a few years.
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That doesn't make a lot of sense to me. Okay, the not being in the sunlight hence cold makes sense, but wouldn't heat be conducted through the planet? That would make it warmer than just being out of the sun, say at Mercury's L2 (assuming that that's in the umbra).
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Sure there will be some conduction, but rock doesn't conduct heat terribly well. So while I'd expect Mercury's polar craters to be warmer than the Moon's polar craters, I would expect them to still be really cold. (Not necessarily the coldest place in the solar system, though. In fact, you can guess that it may be a polar region of a Jovian moon since Jupiter's obliquity is only 3 degrees. Or a Neptunian moon; tilt is a lot higher, but 1/r^2 comes in big time there as does the high albedo of the bodies.)
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Good point. I hadn't considered that. The same would probably hold true for the gas giants. Although for Coldest-Place-In-The-Solar-System(tm), I'd still be looking more toward Pluto and Sedna, than anywhere inward of the asteroid belt.
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Actually, Pluto (at least on the average) is warmer than Triton. Albedo wins in that case. For actual coldest place, the rapidly expanding frontier is making that a moving target, I'm sure.
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Rock does conduct heat very well. Well, some do. Others not so well, but none of them are what we would call good insulators.
But hundreds or thousands of miles of *anything* will make a very effective insulator. :)
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It's not a good conductor compared to, say, metals, which is my point. Coupled with the point I didn't make explicit, but you did (thanks!), that LOTS of rock is just not a good conductor.
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"ERROR 589: Your argument is out of relation."
A huge sun right in front of you for billions of years makes a *very* effective heating device too. :)
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Well, which is going to win? Billions of years of sun, or hundreds or thousands of miles of rock?
I suspect the sun will. The core of the Earth is hot too, but the surface isn't. But if you go down just a few miles, the temperature increases so much that humans can't survive without special cooling. The Earth has had a few billion years to find an equilibrium too.
In any event, my only point was that rock isn't a particularly good insulator, that it only seems that way because there's so much of
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(And yes, I know what you're referring to.)
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Because almost all regular satellites orbit pretty much in their planets' equatorial planes. Saturn's moons are therefore bad candidates, for example, since Saturn has a high obliquity (26 degrees).
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Mercury doesn't get as much interest as Venus because it is very, very hard to get to and has an extremely hostile orbital environment once you get there. Venus gets less attention than Mars because it very hard to get there, has a hostile orbital environment and very difficult to learn anything once you do because of the cloud cover.
Mars, by comparison, is merely hard to get to, has a relatively benign orbital environment, and has a transparent atmosphere.
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Oddly enough, fat bottomed girls are nowhere to be found.
they are, but hidden behind event horizon [slashdot.org]
Orbital Insertion? (Score:2, Funny)
I thought this kinda thing wasn't happening when I read the No Space Porn [slashdot.org] article?
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Misleading Headline (Score:2)
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No, but as soon as I read it, I thought I was going to be reading about some new, mercury-based propulsion system - or about a spacecraft that had suffered a mercury containment failure and this had caused some weird kind of resonance/electrical short.
Too much Star Trek, I guess.
Question on why so long a time to establish orbit? (Score:2, Interesting)
Could someone please explain why according to the web site the orbit insertion is going to take another pass and another 3 years. Does it really take that long to slow the spacecraft down?
Re:Question on why so long a time to establish orb (Score:5, Informative)
Because it is energetically tough to get to Mercury they are trying to get into with as little fuel expenditure as possible, to send as much payload as possible. Since there is no atmosphere, aerobraking is not possible, and thus they are using gravity assists to help reduce the orbital insertion delta-v to a manageable number. Each flyby speeds up the spacecraft a little, to better match Mercury's orbital velocity, and they decided on 3 of these to get the performance they wanted. There is a synodic period (the orbital beat period) between each such opportunity, so it takes a while to complete three flyby gravity assists.
The mission FAQ [jhuapl.edu] has more information on this.
Re:Question on why so long a time to establish orb (Score:4, Informative)
sorry - "speeds up" should be "slows down," above.
oh no! (Score:1)
Speeds up is correct, mod parent down. (Score:1)
Info on gravity assists for the MESSENGER mission [jhuapl.edu].
There will actually be 6 total flybys (3 of mercury, 2 of venus, 1 of earth) during which the spacecraft will accelerate in order to decrease its orbital period from 365
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The flybys and the ridiculously indirect route are not to speed up the craft, its actually to slow it down. Mercury is a very small planet, a little bigger than our moon, so the flybys are meant to slow down the craft enough so that it can be "caught" in the very low energy level orbit of Mercury.
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Well as another poster in the above [slashdot.org] thread pointed out, that's incorrect.
To be "caught", you'd want low relative velocity to Mercury, surely.
And just because you missed it, I'll repost oneTheory's link: http://messenger.jhuapl.edu/the_mission/gravity.html [jhuapl.edu]
Re:delta-v (Score:5, Informative)
The most efficient time/location to make orbital adjustments is apogee or perigee. If you enter into a highly eliptical orbit and wish to circularize at a much lower altitude using only a fractional-Newton thruster, yeah, it'll take a while. MESSENGER has a 650N main thruster, but only about 600kg of propellant. That equates to "not a lot" of thruster time. The main engine has a Specific Impulse (Isp) [wikipedia.org] of 318 seconds. [spaceref.com] On Earth, you'd get about 318 seconds (5+ minutes) of operation. That gravitational element doesn't really apply out in space, so the available thrust-time will be longer. The NASA PDF [nasa.gov] indicates that the final orbital insertion burn will consume 30% of the propellant, and will last about 14 minutes. Extrapolating, that indicates that MESSENGER has about 42 minutes of propellant on board.
There's also a nice explanation of the orbital maneuvers on the JHUAPL website, [jhuapl.edu] and also a nice PDF showing the orbital insertion cost plots. [nasa.gov]
Re:delta-v (Score:4, Informative)
The main engine has a Specific Impulse (Isp) of 318 seconds. [spaceref.com] On Earth, you'd get about 318 seconds (5+ minutes) of operation.
No. Specific impulse, despite being measured in seconds, has nothing to do with how long the rocket can fire. That obviously depends on how much propellant you carry.
Take another look at that Wikipedia article you linked on specific impulse [wikipedia.org].
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Fthrust = Isp * (mass flow rate) * (gravity on Earth), which allows us to solve for the mass flow rate:
650N = 318s * MFR * 9.8m/s^2
MFR = 0.209 kg/s
With 600kg of propellant on board, you'd be able to fire the engine for 600kg / 0.209kg/s = 2871 seconds on the Earth's surface
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With 600kg of propellant on board, you'd be able to fire the engine for 600kg / 0.209kg/s = 2871 seconds on the Earth's surface ... a little over 47 minutes.
True, though your calculation has nothing to do with Earth's surface. (When Isp is measured in seconds, they multiply by the gravity on Earth's surface just for fun.)
Re:Question on why so long a time to establish orb (Score:1)
MESSENGER used solar sailing (Score:4, Interesting)
Note that MESSENGER used solar sailing to correct its trajectory for this flyby:
http://www.planetary.org/blog/article/00001674/ [planetary.org]
we should be doing more of this (Score:2, Interesting)
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AFAIK, neither creationism nor Paris Hilton has had any appreciable effect on Space exploration.
In any event, most Intelligent Design folks don't deny the usefulness of space science, they just believe that someone started created the Universe. The position that God (or some imaginary man with a long white beard) created the universe does not preclude one from exploring said created universe.
The actual cause is that too few people are interested in a project which will only become economically significant
We need to be solving practical problems. (Score:5, Funny)
When they eventually build a hotel on Mercury, I want an ice machine that works and doesn't keep running out of ice. So how big would such an ice machine have to be on Mercury? Would they have to charge $3 for a soda? I hate those tacky signs that say "No Filling Ice Chests."