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Messenger En Route To Mercury
Soft writes "NASA's Messenger space probe has lifted off on its second try on a Delta 2-Heavy rocket.
As mentioned earlier on Slashdot, it is poised to orbit Mercury in 2011 after three flybys, as well as two flybys of Venus and one of Earth for course corrections.
It will be the first probe to visit the innermost planet since Mariner 10 in 1974 and 1975.
Stories on the BBC and SpaceflightNow."
Not exactly Instant Messenger, is it?
How did Mercury, believed to be 60 percent iron, end up with an oversize core, a thin shell of a crust and the highest density in the solar system? Was its crust blasted away in the distant past by a cataclysmic impact? Was it boiled away in the extreme heat of the young, nearby sun? Or were metals for some reason concentrated in the inner region of the solar nebula that coalesced to form the sun and planets?
Perhaps my knowledge is a little dated, but I thought that the inner four planets have higher density because the sun stripped the inner solar system of light gasses like hydrogen due to the larger mass and higher gravitational field of the sun during the formation of the sun and the solar system. Outer planets are gas giants because the Sun's (or the pre-sun center of the accretion disk ) gravitational field was not strong enough to grab the light elements from the portion of the solar system that would become the gas giants (further from the center of the pre solar system accretion disk). Also, this was thought to be why Pluto is an oddball (far away from the sun, but a frozen rock of a planet) that might be an escaped moon or oort cloud refugee.
Can anyone confirm this? Or am I citing stone age planetary science that is no longer valid?
8-2-3004 2:15:56.537 EST: Departure Scan, Cape Canaveral 9-5-2005 Scan Venus gravitational assist 4-22-2008 Scan First flyby 12-14-2009 Scan Second flyby 6-12-2010 Scan Third flyby 2-01-2011 Scan Orbital Insertion ADDRESSEE NOT HOME, SIGNATURE WAIVED
When a launch is canceled due to mechanical failures, weather, or any other reason, it's considered a try as long as the launch procedure has been started. Since launch procedures can range from 6 hours to 6 days, there are a lot more tries than launches.
Yoda wisdom or no Yoda wisdom, you're still wrong.
(With rockets, if you try and don't succeed, its pretty much SOP - most things don't launch on the first attempt. Now, if you were to say "ignite" instead of try, you'd be correct - most rockets don't do too well on a second ignition.)
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Mod me down, you fucking twits. Go ahead. I dare you.
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The spacecraft cannot fly straight to Mercury; it does not carry nearly enough fuel. So it will fly once past Earth, twice past Venus and three times past Mercury and make 15 loops around the sun before slowing enough to slip into orbit around the small, hot planet.
The following statement is false.
The previous statement is true.
Welcome to my world.
maybe now they'll finally find Planet Vulcan
try { do() || do_not(); } catch (JediException err) { yoda(err); }
MESSENGER stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging
I dont understand why solar-powered ion drives are not used on missions like this. Probes like the ESA SMART-1 has shown that such craft can be small & economical, and there is an abundance of solar power available for free. I understand that final orbital insertion can be a problem - could a solar ion drive deliver enough "punch", or would a supplemental booster be needed? Otherwise I understand that solar would be way more fuel/time efficient over a few years compared to carrying rocket fuel & hanging around for gravity slingshots. Am I right?
I have even read of deep-space solar-powered mission designs that head in inside mercurys orbit, grab loads of power and then head out beyond Jupiter..
Why arnt ion drives used more?
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As another poster has pointed out, officially the name is derived thus: MESSENGER stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging. I was looking at this information and thought that it was a rather contrived name - kind of like the laws that the US Congress passes (PATRIOT Act, etc...) And then it occurred to me, they probably called it Messenger because in Greek mythology, Mercury was the messenger of the Gods. Or I could be completely wrong...
Seriously, the Metric/Imperial thing happened like 1999. Since then we have had Galileo end it's mission successfully, Mars Odyssey (2001), The exploration rovers, Cassini has so far performed flawlessy, and the hard part is over (Orbit insertion), NEAR, an orbiter, landed softly on an asteroid on it's solar panels, Deep Space 1 did the comet Borrelly encounter, Stardust has successfully collected the comet material (return in 2006)..and probably others that I don't remember offhand.
I mean, after so many successes, and some folks *still* don't let go. Now, if one of the probes were lost *again* due to a measurement system error then we could get a laugh out of it, but so far...they have not done that. Granted, in 1999 the *other* Mars probe, Polar lander was lost too, and so was Deep Space 2. But still...that's five years ago, and NASA has had loads of successes since then.
This is kinda starting to resemble *BSD is dying trolls..
Also, remember the Earth is in orbit around the sun, so to get to the orbit of Mercury you need to lose a lot of the energy Earth's higher 'altitude' gives you to start with. Plus you need to slow down enough to where you don't need an ungodly amount of fuel to slow down into orbiting Mercury itself.
Mix the failings of Usenet with the shortcomings of the World Wide Web and the result is slashdot.
Why aren't ion drives used more?
2 1072826.htm. (And enter "ion engine" at NASA's main site for a huge number of links.) So, it's not only ESA that have their fingers in this pie.
That's actually quite a good question, given the huge amount of power available from sunlight in the inner solar system. A continuous-burn trajectory to Mercury would probably be very much shorter than the current one; the thrust may be small, but craft speed builds up rapidly under such continuous acceleration. You'd only need to carry enough conventional chemical propellant for the final orbital insertion.
NASA has been very active on the ion-engine front -- last year it successfully completed a pretty advanced test: http://www.sciencedaily.com/releases/2003/11/0311
Maybe the answer is that ion engines still need a few more years of development? Certainly not long though, since small ion thrusters are already in use, as you point out.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
Actually it's a combination of *decreasing* velocity (each flyby will take speed away from the craft, causing it to have a smaller orbit) and the final position in orbit (the final orbit has to be very ellipitcal, and very near polar).
The number of times around the sun is merely a side effect of a) the number of flybys needed and b) the fact that Messenger needs to orbit for a while before it can reach the planet needed for flyby.
Gilthalas
Software Engineer, Space Dept, JHU/APL
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No, there isn't. The official terminology acknowledges attempts as tries, as does the English language. Do you think trying to launch starts when they hit "Go" on the main motors? It starts a lot earlier than that; launch procedure usually starts with fueling (for liquid-fueled motors). Solid rockets have much shorter launch procedures, but are generally not used for launch all by themselves (only as strap-on boosters, for the most part).
The writeup is correct as written. 'NASA made two launch tries, and succeeded in launching on the second try'. This sentence is equivalent to 'NASA made two launch attempts, and succeeded in launching on the second attempt.' There is no difference in the two. NONE.
And here are the common English definitions, just to drive the point home:
Attempt - To try to perform, make, achieve.
Try - To make an effort to do or accomplish (something); to attempt (something).
Admit you were wrong and move on.
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Mod me down, you fucking twits. Go ahead. I dare you.
(I read with sigs off.)
after having gone by Earth on a flyby (2005?)
and by Venus twice on flybys (2007, 2008)
See this link Mercury
After a flyby of Mars in 2008, and another in 2009, it settles down for orbit in 2011.
That last long ago (30 years) visit was only a flyby.
So all that confusion is about getting the right orbital velocity to stay, plus we get good science all along the way.
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