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First Probe To Orbit Mercury May Help Us Learn How Planets Form
An anonymous reader writes "Next month, the first space probe in nearly 40 years will approach the planet Mercury, with an array of instruments that could help answer fundamental questions about how planets form. The mission is called MESSENGER, for Mercury Surface, Space ENvironment, GEochemistry and Ranging. On March 17 it will pull into orbit around mercury, after more than six years of maneuvering between the Earth, Venus and Mercury itself."
On the bright side the solar panels don't have to be very large," Blewett said.
I see what you did there.
Ice Cream has no bones.
That article is far worse than your average /. post: it lacks cohesion, and sounds more like rambling than a serious piece of journalism. I would bet the author hasn't had it proof-read, probably not even by himself. There must be better articles around describing this event.
They certainly did a lot of "ranging" coming up with that acronym.
New game-show? "NASA would like to buy a vowel for....ten million dollars!" *clap* *clap*
Table-ized A.I.
http://www.nasa.gov/mission_pages/messenger/main/index.html
how is plannet formed
how solarsystem get pragnent
OT, but one of my favorite spacecraft videos is the departure video from MESSENGER.
A lot of gravity assist maneuvers. It is (energy wise) very difficult to get to put a probe in mercury's orbit, first you have to do a lot of braking to put it into an elliptical orbit to reach mercury's orbit then another lot of braking to make it match mercury's orbit then more braking to put it into (some sort) of elliptical orbit AROUND mercury then (optional) more braking to "circularize" your orbit around mercury!
I think energetically speaking it's about as difficult to send a probe to Mercury as it is to Jupiter even though Jupiter is much farther away. So in order to not have to use a huge (expensive booster), the probe does a bunch of gravity assists by sling-shotting near Venus, Mercury and maybe even the earth. This saves a LOT of fuel but adds a LOT of time (otherwise as you probably guessed it would've gotten there years earlier).
This will let you see how things look from any spacecraft: http://space.jpl.nasa.gov/
Thinking of Mercury also makes me think of the very good horror/sci-fi movie "Sunshine". (Partial SPOILER ALERT).
I really liked it except the intensity of the Sun, even at those distances, was dialed up a bit too high. I mean, when the captain gets "blown" by the very brief exposure to the (dying) sun, it was a little too much considering he was in a very heavily heat shielded suit. And the ship wasn't even yet at Mercury's orbit! I guess just slowly being cooked to death was not dramatic enough for the script writers.
Otherwise, I really liked the movie, the other details were mostly spot on (except there wasn't "zero-G" in a few places in the spacecraft where it should've been) and the fact that they were out of communications with earth even before reaching mercury seemed suspect (I know there could've been crazy radio interference with a wacky sun but a good laser/maser could punch through almost anything). Obviously these were points that the director chose not to deal with because of cost (zero-G) or plot (kept the crew in scary isolation). Anyway, loved some other touches like the room with the fissile material "bomb" which was evidently so dense it had it's own significant and varying gravitational field! And a believable scary "monster!"
Another excellent sun-oriented sic-fi piece is Arthur C. Clarke's story about a trip to the asteroid Icarus (I think it's called "Summertime on Icarus"). I always thought it would be a good way of protecting future long-term travellers to asteroids/comets from solar flares, just temporarily park them in the shadow!
Messenger is a great name, perfectly respectable with a sort of a cute "ZOMG HI Mercury! LUV Earth!" edge to it.
And then you just had to go and fucking ruin it with a horrendous backronym didn't you.
I think we missed a great opportunity to try a medium sized solar sail. Say a couple of hundred metres in diameter. Inside the orbit of Venus a sail like that would be very efficient.
http://michaelsmith.id.au
Apologies if I'm being dumb here, but isn't a solar sail only really useful for moving away from the sun, not towards it?
I am trolling
An object orbiting the sun could point the sail 45 degrees away from the sun so that sun light is reflected ahead in the orbit. That way pressure from sun light would slow the object down and move it into a lower orbit. Mercury is very difficult to reach because you need to dump a lot of kinetic and potential energy to match orbits with the planet. In other words you have to go a long way down the sun's gravitational well.
http://michaelsmith.id.au
Those probes in uranus doesn't count.
What about the rings around Uranus?
Ceci n'est pas une
the probe does a bunch of gravity assists by sling-shotting near Venus, Mercury and maybe even the earth.
It sling-shots around Mercury to get to Mercury?
"Total destruction the only solution" - Bob Marley
Actually, it's easier to escape the Solar System than go into an orbit around Mercury.
Reaching Mercury from Earth poses significant technical challenges, since the planet orbits so much closer to the Sun than does the Earth. A Mercury-bound spacecraft launched from Earth must travel over 91 million kilometers into the Sun’s gravitational potential well. Mercury has an orbital speed of 48 km/s, while Earth’s orbital speed is 30 km/s. Thus the spacecraft must make a large change in velocity (delta-v) to enter a Hohmann transfer orbit that passes near Mercury, as compared to the delta-v required for other planetary missions.
The potential energy liberated by moving down the Sun’s potential well becomes kinetic energy; requiring another large delta-v change to do anything other than rapidly pass by Mercury. To land safely or enter a stable orbit the spacecraft would rely entirely on rocket motors. Aerobraking is ruled out because the planet has very little atmosphere. A trip to Mercury requires more rocket fuel than that required to escape the Solar System completely. As a result, only two space probes have visited the planet so far. A proposed alternative approach would use a solar sail to attain a Mercury-synchronous orbit around the Sun.
https://secure.wikimedia.org/wikipedia/en/wiki/Mercury_(planet)
Do what thou wilt shall be the whole of the Law
You don't use an untested, unvetted technology as your primary and only means of propulsion for a mission whose sole purpose is to study a previously unstudied planet in detail. That would be like betting your life savings on a horse that has never run a horse race before.
Now, that said, if the spacecraft had enough spare capacity (power and mass wise) to pack on a small solar sail for a proof-of-concept demonstration, then, yes, it could have been a great opportunity. But if the technology was not ready, if the risk was too high (controlling a long, deployable, non-rigid moment arm is no trivial task) , or if the budgets for the spacecraft were too tight, then the design team would have vetoed any additional secondary mission (like a tech. demo).
Motorcycles, Robots, Space Gossip and More!
Yep.
http://en.wikipedia.org/wiki/MESSENGER#Launch_and_trajectory
The "sling shots" are to lose momentum, rather than gain it. As far as I understand it, MESSENGER used a (relatively distant) orbital pass of Mecury to slow down, allowing it to enter it's lower altitude orbit on a later pass.
IANARocketScientist, though.
You don't even really need to be able to direct the sail if you can change its surface area. Deploy to maximum at apoapsis and it will slow the craft as it approaches periapsis resulting in a lower periapsis. The hard part (using a solar sail) would be drawing in apoapsis, as you would have to exert thrust towards the sun, you would need use a more conventional thruster and undeploy the solar sail or you will end up increasing the ellipticality.
http://xkcd.com/681/ has a nice graph of gravitational potential energy differences that need to be overcome when traveling around the solar system (ignoring gravity assists, etc). Mercury is clearly harder to match up with energy-wise than anywhere else besides the sun itself.
Wikipedia:
Which is correct?
There is no force, however great/Can stretch a cord, however fine/Into a horizontal line/Which is absolutely straight.
It takes a lot of delta v to get to Mercury and orbit the planet, so multiple sling shot manuvers were done to keep the cost of the probe from being excessive. Neil
Rotates on its axis once every 59 Earth days, but because of its slow rotation and fast speed around the Sun, one solar day (from noon to noon at the same place) lasts 176 Earth days, or two Mercury years
Although I'd say the article is clearer, both the article and Wikipedia are technically correct because Wikipedia talks about three rotations, not days. Calculating the length of a solar day on Mercury requires accounting for the orientation of a point on Mercury to the Sun; as Mercury rotates once, it also travels through 59/88 of an orbit, so one rotation != one solar day on Mercury and the article and Wikipedia are not in contradiction, they just tell different parts of the story. Hope this helps.
"I can't imagine how things could get any worse!" (some guy) "That could just be failure of imaginatioÂn on your p