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Space

Messenger En Route To Mercury 120

Posted by timothy from the luggage-is-going-to-phoenix dept.
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."
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Messenger En Route To Mercury More

Messenger En Route To Mercury

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  • 2011? (Score:5, Funny)

    by Anonymous Coward on Tuesday August 03, 2004 @05:05AM (#9867762)
    Not exactly Instant Messenger, is it?
    • Not exactly Instant Messenger, is it?

      Indeed not, as far as I can tell it seems to be a time machine of some sort. Quoting verbatim with my emphasis.

      If all goes well, MESSENGER's main engine will fire for 15 minutes on March 18,
      2001, putting the spacecraft into an elliptical orbit tilted 60 degrees to the planet's equator with a low point of about 125 miles above the northern hemisphere and a high point of 9,420 miles.

      • Re:2011? (Score:2, Interesting)

        by essreenim ( 647659 )
        Yeah. I _KNOW_ my grandmother could get there before then. I know orbital mechanics is tricky because trying to enter orbit around Mercury is difficult with the immense speed generated by travelling towards the sun ... but come on.
        What this is like everything is a money dictated project i.e the Messenger guys have none and have had to come up with a low cost lengthy gravity controlled trip ..blah blah blah.
        Come on Nasa, start working on cutting down your mission times..
        • It's harder than that, because you have to slow down enough to even get to that "immense speed generated by travelling towards the sun".

    • Gets there in 2008 actually (Score:4, Informative)

      by DumbSwede ( 521261 ) <slashdotbin@hotmail.com> on Tuesday August 03, 2004 @02:58PM (#9871298) Homepage Journal
      2008 actually
      after having gone by Earth on a flyby (2005?)
      and by Venus twice on flybys (2007, 2008)
      See this link Mercury [nytimes.com]

      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.

    • Re:2011? (Score:3, Funny)

      by Lord Omlette ( 124579 )
      It'll have to put up an away message for quite some time.
    • of MS-Windows 95 AKA Project Chicago. Does that count for anything?

  • Men are from Mars, Women are from Venus and Small furry creatures are from Alpha Centauri.

    So what the heck is there on Mercury? :-)

  • I thought we knew this bit already . . . (Score:5, Interesting)

    by StateOfTheUnion ( 762194 ) on Tuesday August 03, 2004 @05:22AM (#9867808) Homepage
    From the Spaceflight Now [spaceflightnow.com]

    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?

    • Re:I thought we knew this bit already . . . (Score:5, Interesting)

      by el-spectre ( 668104 ) on Tuesday August 03, 2004 @05:37AM (#9867849) Journal
      I think your science is right... what the article seems to be emphasizing is the massive iron content... Earth, whilst having an iron core, is still mostly silicon and oxygen (the mantle & crust). For some reason Mercury has more than it's fair share of iron core, compared to other inner planets. 'tis puzzling.

    • Re:I thought we knew this bit already . . . (Score:2, Interesting)

      by Anonymous Coward
      According to the Messenger website you are largely correct, the absence of lighter gpI&II metals is down to them simply boiling away from the crust. However it goes on to say that this is unconfirmed _theory_ and one purpose of the mission is to collect more evidence to confirm/deny this. The other theory is that physical activity (impacts) have blasted away most of these elements from the early crust.

      On a sceptical note, I question the value of such a mission. Mercury is going to remain beyond our rea

      • Re:I thought we knew this bit already . . . (Score:5, Informative)

        by pedroloco ( 778593 ) <hombrepedro@gmai l . c om> on Tuesday August 03, 2004 @11:46AM (#9869580)
        Mercury is real hard to observe from Earth-based telescopes since it is so close to the Sun. In the near future, the only way to get higher resolution data is to send the telescopes to Mercury. Even the most fervent remote sensing advocate will have to admit that data quality generally improves with decreasing distance to the target.

        Using martian studies as an analogy for mercurian (hermitian?) observations, one can see how spacecraft data provide much more detailed observations over ground-based observations. Earth-based data of Mars obtained during the last opposition last summer (when Mars was closer to Earth than Mercury ever gets) does not compare to spacecraft data in terms of resolution. Earth-based (visible-wavelength) observers of Mars have to content themselves with seeing albedo variations. The geology which caused those albedo variations was largely unknown prior to our sending spacecraft. (Please note that tha "canals" reported by Lowell were likely optical illusions - Lowell's canal maps do not correspond to locations of known martian dry channels.)

        Similarly, Earth-based spectroscopic observations of Mars have poor spatial resolutions. I remember one paper from '96 which reported 300 km/pixel resolutions. Two spectrometers currently in orbit around Mars get far better spatialresolution (Thermal Emission Spectrometer gets 3 km/pixel; THEMIS-IR gets 100 m/pixel - although, granted, that's with a low spectral resolution).

        Two advantages that Earth-based observations have over spacecraft data are: 1) Earth-based observations are a lot cheaper to obtain and 2) a network of Earth-based observers can look for changes in the target with better time continuity than a singe spacecraft (since the spacecraft may be looking at some other part of the planet).

        The true value of a Mercury mission is two-fold. Most obviously, new spacecraft observations will provide geologic context for current ground based observations (Mariner 10 only imaged ~40% of the planet). Additionally, Mercury is considered an end-member planet - a planet that likely formed close to the Sun in the solar nebula from which the solar system formed. As such, understanding how Mercury formed will provide a calibration point for models of solar system formation, which could have implications for formation in other portions of the solar nebula or the early solar system or of other planetary systems.

        No, we aren't going to be sending people to Mercury anytime soon, but neither are we going to be sending people to Mars in the near future. (Even Bush's space initiative doesn't plan a Mars landing for at least 20 years - plenty of time to get distracted by other problems.) However, even if people aren't going to those placed, there are still useful things to learn regarding the solar system in which we live.
    • It's not so much that gas is pulled to the Sun easier, rather than it's harder to get hydrogen and helium to stay solid when large clumps of it collide. It sublimates and it's momentum is distributed. This makes it hard for the gases to build up to the velocities that planets have. With lower velocities they fall to lower orbits, most likely becoming part of the Sun.

      As far as Mercury, it is so close to the Sun that the solar wind is strong enough to blow away any atmosphere it has. It also has a very low ma

    • Re:I thought we knew this bit already . . . (Score:2, Informative)

      by Anonymous Coward
      You're close, but not quite. It wasn't that the sun's gravity pulled in the lighter elements from the inner planets, but rather, that the solar wind from the sun blew all the lighter material outward, towards the outer solar system (which is why there was so much of it available to form the gas giants). You just have your vacuum in the wrong direction ;).
    • Not quite, no.

      The inner planets are rocky/metallic because it was too hot for ices to form. Most of the proto-solar disk would have been in the form of hydrogen and helium. The next most abundant elements are oxygen, carbon, and nitrogen. With so my of these and hydrogen, hydrogen compounds (water, ammonia, methane) can do a lot of planet building if they can form solids. Near the proto-Sun, it would habe been too hot for this to happen. Somewhere around 5 AU, water ice could first freeze out. Not su

  • Messenger's telemetry log... (Score:4, Funny)

    by vudufixit ( 581911 ) on Tuesday August 03, 2004 @05:28AM (#9867828)
    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
  • This is a very bad idea - going to Mercury and back to Earth. Haven't they read that Mercury is toxic [healthcastle.com]

    Next they'll try to return from Saturn with car parts. [saturn.com]

  • Too bad this isn't Microsoft Messenger... they could apply service packs to Mercury and give it an atmosphere.

  • planet inside mercury orbit (Score:3, Interesting)

    by ch-chuck ( 9622 ) on Tuesday August 03, 2004 @06:05AM (#9867911) Homepage
    maybe now they'll finally find Planet Vulcan [csicop.org]

  • What Messenger Really Stands For . . . (Score:5, Informative)

    by StateOfTheUnion ( 762194 ) on Tuesday August 03, 2004 @06:05AM (#9867914) Homepage
    According to JPL [nasa.gov]

    MESSENGER stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging

  • 2011? How long with ion drives? (Score:5, Interesting)

    by adeyadey ( 678765 ) on Tuesday August 03, 2004 @06:13AM (#9867925) Journal
    I dont understand why solar-powered ion drives are not used on missions like this. Probes like the ESA SMART-1 [esa.int] 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?
    • Though ion drives are really effective in terms of specific impulse (you need little fuel for gaining unit momentum), they are not much mass-effective (thrust per unit engine mass) at all. a trip to Mercury is a kind of parachute jump, you have to go really slowly or you're Sunburnt :). so if you want to get there faster, you first have to accelerate, and step on brakes afterwards. Russians say -- going slowly, get farther. :)

      • Re:2011? How long with ion drives? (Score:4, Informative)

        by adeyadey ( 678765 ) on Tuesday August 03, 2004 @06:53AM (#9868008) Journal
        ..They are not much mass-effective (thrust per unit engine mass) at all.

        Current Ion drives can deliver >10x more power overall per Kg compared to rockets - but they do it slowly, over months/years.. Rockets can deliver "punch" at a spacific time. Advantages/Disadvantages both ways really.

        Messanger as-is carries 1/2 its weight as fuel, so if you can reduce that 10 fold, or get 10 times the power, thats a good thing. Faster missions are less expensive in terms of keeping support staff too, and less risky. I think a solar-ion mission that spirals inwards as it decelerates would be way more efficient than the current plan. And would be much less dependant on celestial mechanics for launch dates.

        Anyone from NASA here know why they dont use solar-ion drives for these missions? Is there some sort of political bias against solar & pro old fashioned rockets or nuclear? (And yes, I know nuclear (RTG) is needed for deep space - at least for electric power for the science instruments..)

        Here is a better link for SMART-1.. [esa.int]
        • Current Ion drives can deliver >10x more power overall per Kg compared to rockets - but they do it slowly, over months/years.. Rockets can deliver "punch" at a specific time. Advantages/Disadvantages both ways really.

          I'm no rocket scientist, but I don't think I'd want to depend on a thruster that takes that long to develop it's 'punch' for braking while headed toward something as close to the Sun as Mercury.

          It just has "oops" written all over it :)

          ---PCJ

        • Re:2011? How long with ion drives? (Score:4, Informative)

          by Cujo ( 19106 ) * on Tuesday August 03, 2004 @08:11AM (#9868260) Homepage Journal

          Not power - specific impulse, which is effectively propellant ejection velocity.

          Usually specific impulse is given in units of seconds, but this is an archaic convention - it's really velocity (they divide by the acceleration of gravity at ea level to get seconds).

          There are two major problems with ion propulsion - ion thrusters need Kilowatts of power to operate (and so drive the design, mass and cost of the power subsystem), and they have very low thrust. They are also expensive and have limited life. So with ion propulsion, like everything else in engineering; if it's not necessary to do it, then it's necesary NOT to do it.

          • Usually specific impulse is given in units of seconds, but this is an archaic convention - it's really velocity (they divide by the acceleration of gravity at ea level to get seconds).

            Thank you for that simple but insightful bit of information. I regret I have no moderation points to give you.

            I've never really understood "rocket science" even though I still remember the mechanics and physics I learned in college. Is there a good website that explains the calculations, and especially any more unobvious te

            • Probably - JPL had a "Space Mechanics" tutorial online once - probably still do.

            • What calculations are you looking for, in particular? There are a lot of them, you know ;) Here's a page that has a good number of them:

              http://members.axion.net/~enrique/rocket.html

              As for myself, there is only one problem in orbital mechanics that I have been unable to track down a solution to, which has been holding up the addition of the effects of torques (and consequently, realistic effects of RCS thrusters, control surfaces, and gimballing) to my rocket simulator:

              Does anyone know how to, given a n
              • I've checked a number of physics texts, and none of them address this problem.

                Get some better textbooks, maybe? (Say for example, Univeristy Physics by Young & Freedman- I don't have it, but at $150, it had better be good) Problems like that this are, to my recollection, standard material for a second semester college physics course.

                It's called "rigid body kinematics/dynamics". You start by studying spheres of uniform density, then consider objects composed of multiple such spheres locked together
                • > Or, if you know calculus, you can derive closed-form solutions to problems ... (etc)

                  Seing as I already mentioned moments of inertia, I'm quite familiar with this already.

                  > It's called rigid boxy kinematics/dynamics

                  Yes, I'm aware of that. And with my searching thusfar, plus searching on the net, I've found plenty that discusses both linear acceleration of a free-floating body, and angular acceleration around a fixed center of mass. Neither of those are what I need. I'm dealing with both multipl
                  • I'm dealing with both multiple forces applying both angular and linear acceleration on a free floating body at the same time here

                    But... multiple forces just does the same thing as single forces... multiple times.

                    Of course, in 3d, each force is likely to be acting about a different axis than the previous one, making bookkeeping of all the axes quite painful (even in software). But that's where tensor analysis comes in handy... or so the engineering students tell me.

                    Have you tried Wiesel's Spaceflight Dy
                    • Actually, I just found an excelent paper last night when I went out net searching again, that covered it all. It explained the main issue that was concerning me (the question of "how much energy goes to angular and to linear momentum?"). The answer is "all of it, to both".

                      Work is force times distance. The reason that you end up with more work being done when you push on the outer edge of an object is because you're having to apply the force across the combination of the distance that the object moves li
          • Yes I remember that impulse was rated in seconds - I should have said per Kg of propellant - ie, I understand that an ion drive can generate 10x the thrust per Kg of propellant, it just does it slower..

            The SMART-1 mission cost $100 million in *total*, not too much in terms of space exploration. The thrusters will operate for 18 months & I think newer designs allow for multiple replacement anodes to replace old ones..

            Ion drive missions have spiral paths, in this case decellerating towards the sun. An i

            • It's actually very difficult designing a planetary rendezvous mission with very low thrust engine. I'm not even sure how you'd do it. Sure, you can use gravity assists in some cases (e.g. Galileo, Cassini, and now MESSENGER), but this helps a chemical propulsion mission as well, and doesn't solve the problem of how you match speeds with the planet. Even with 6 gravity assists, MESSENGER still needs high thrust delta-Vs, and substantial at that.

            • At points where the craft is nearer the sun, more power is available - lots more power.

              When you get close to the sun, solar arrays have a certain problem - they get hot, and hot solar arrays are much less efficient. If you look at MESSENGER's solar arrays, you'll see that most of the solar array area is taken up with reflectors to keep the solar array from overheating.

    • Lot of activity on ion engines at NASA too (Score:5, Informative)

      by Morgaine ( 4316 ) on Tuesday August 03, 2004 @07:13AM (#9868061)
      Why aren't ion drives used more?

      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/2003/11/03112 1072826.htm [sciencedaily.com]. (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.

      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.
      • Maybe it is something as simple as that they designed MESSENGER years ago when ion drives were not fully tested. Once they had designed it and started construction and programming etc., they would have been required to rebuild the thing from scratch to use ion drives, possibly costing more money than saved. Or maybe this was some big shot's pet project and it just went through. In the future I expect NASA will use more ion drives but they've got something that works now, and there is no huge rush to see

      • Re:Lot of activity on ion engines at NASA too (Score:2, Insightful)

        by Anonymous Coward
        I'm not an expert, but I suspect that the problem with Mercury is that the environment is so hostile that you want to spend all your time close to the sun doing science rather than getting into orbit. This craft is going to swing by Mercury a few times, but it also swings out again, so until final orbital insertion it is generally quite far from the planet. With an ion drive you'd slowly spiral in towards the sun from Earth, so you'd spend a lot of time near the sun but not yet at Mercury.

        You might also st

    • Re:2011? How long with ion drives? (Score:4, Informative)

      by CXI ( 46706 ) on Tuesday August 03, 2004 @10:33AM (#9869118) Homepage
      Why arnt ion drives used more?

      To put it in simple non-technical terms, you can't slow down fast enough. Yes, you can get a good bit of speed up over several months on a more direct trajectory, but you'd end up having to start slowing down once you're only 1/2 way there.

      To make it at all reasonable, you'd have to use a few gravity sling-shots to build up speed and possibly dump speed later. Once you're doing that, you might as well go with the old tried and true chemical propellent that gets you up to speed much quicker.

      Ion drives are great if you're going to be going in a straight line for a very long time and don't want to stop, ever. The farther you go, the faster you go, so the less reasonable it is to slow down.

      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..

      Really? Where do they store all this power? If they used an ion drive, they would need constant power for the entire trip. Sounds a little fishy to me...
      • Last September the European SMART probe [bbc.co.uk] was launched to the Earth's Moon. It will take 15 months to arrive there by ion drive. Manned lunar missions took three days by chemical propellant.
        • SMART-1 was primarily a test-bed for lots of new technologies, including ion propulsion. Going to the moon was almost a bonus - the main objective was to see if it was possible to make very small, cheap missions ($100 million, I think). It was piggy backed (cheaply) onto an existing satellite launch, hence having the minimal boost needed to get to Low Earth Orbit.. If you used a bigger rocket (smaller than Apollo) it could get there in 3 days too.

          For a bigger mission like Mercury, as you can see, it is mu
    • 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 suspect that as far as Messenger is concerned, it doesn't use an ion drive simply because they weren't around when the project was started --- I can't find any information on when design started, but these missions routinely take well over a decade from when the paperwork start

    • I dont understand why solar-powered ion drives are not used on missions like this.

      Because any spacecraft headed for planets inside earth's orbit will be falling towards the sun anyway, and thus accelerating. This makes a direct trip between Earth and Mercury very difficult because in order to acheive orbit around Mercury, you'd have to slow down a whole lot - more than a chemical rocket could produce and way, way more than an ion drive. Sending a probe on a path like this would essentially give it a stup
      • Also, you don't seriously believe that solar panels could withstand the heat and radiation on Mercury do you?

        Uh oh! You better tell NASA quickly! The solar panels [jhuapl.edu] that they've just launched to inside the orbit of Mecury are gonna kersplode!
      • For interest's sake, here are some 0th-order approximations of the Hohmann transfer orbit patched-conic calculations...
        1. Low-earth orbit requires about 7.8kps
        2. Hohmann transfer from Earth to Mercury requires an apehelion delta-V of 7.5kps relative to Earth. Relative to low-Earth orbit, that becomes about 5.5kps.
        3. A circular near-Mercury orbit requires 70% of surface escape velocity (which is 4.3kps), or 3kps.
        4. The Hohmann transfer requires a perihelion delta-V of 8kps relative to Mercury. Relative to
    • In reply to my own question - the up and coming ESA Bepicolombo mission to mercury [esa.int] will use.. yep.. Solar Electric Propulsion. It still uses gravity slingshots to slow down, and needs a small conventional rocket to kick it into Mars orbit.

      It will launch 2012 and take 4 years to get to Mercury, compared to 7 for messenger. Now the interesting part - how much is saved in the mission profile with ion engines? Do ion engines allow for more flexible mission launch windows? How will the propellant/mass profile

  • Mercury, messenger of the Gods? (Score:3, Interesting)

    by Airw0lf ( 795770 ) on Tuesday August 03, 2004 @06:22AM (#9867940)
    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...
    • You're right. I don't know why they bother coming up with an acronym - what's wrong with simply "Messenger"? The earlier probes (Galileo, Voyager, Mariner etc) didn't need a fancy acronym. I guess there's some beaurocratic reason...
      • GALILEO--Get Awfully Lucky If it Leaves Low Earth Orbit
        VOYAGER--Vogons Observing Your Area; Get 'Em Running! (Ah, its true purpose is revealed)
        MARINER--Meet Alien Robots In Near Earth Rendez-vous
        • There's a proposed mission to the Aitken Basin in the south polar regions of the moon currently under consideration. A friend of mine who works in that group asked a number of people for suggestions of what to name the mission. One name was preemptively ruled out: South Pole Aitken Mission (SPAM)
    • Precisely my thoughts. For one thing, I have no doubt Messenger was named such because Mercury was the messenger of the Greek Gods. I've always felt that Messenger was an obvious name for a Mercury probe, so it was no surprise when I heard of this one. (Similarly, i've always thought Mercury would be a great name for an email program, instant messenger or some type of communications software, but i guess the name is too common).

      The MErcury Surface, Space ENvironment, GEochemistry and Ranging bit is obvious
  • I am wonder why so many fly by's. I remeber before it was increase V, but is this being used to do a gentle park around Mercury?

    • Re:So many fly by's (Score:1, Interesting)

      by Anonymous Coward
      There's no doubt that a direct flight to Mercury could have been made in theory, but it would have required a MASSIVE amount of fuel to prevent it from being sucked into the giant gravity well of the sun. There's a remarkable grace in the use of planetary fly-by's to achieve the same result much more efficiently. I actually work with the rocket scientists responsible for this planning.

      • Re:So many fly by's (Score:2, Interesting)

        by thbigr ( 514105 )
        I am sorry I must not have phrased the question well. I do understand using a fly by to increase Velocity, but this guy is going around the sun quite few times. Mercury is inside those orbits. I am assuming it is more of a case of placement rather then speed? Right?

        • Re:So many fly by's (Score:3, Informative)

          by Gilthalas ( 145182 )
          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.
        • I do understand using a fly by to increase Velocity

          To reach Mercury orbit, you have to decrease velocity. Remember that in outer space, it's just as hard to slow down as to speed up. (Unless you find a convenient atmosphere to help you brake, which Mercury doesn't have.)

    • Re:So many fly by's (Score:1, Insightful)

      by Anonymous Coward
      The mission planners may well have some other objectives in mind. It might be nice to have data from other angles/distances and maybe some shots of Venus, as well, especially from inside it's orbit. Ultimately, though, there is simply no huge rush to collect data on Mercury, since we aren't planning on landing people there in the near future, so you might as well cut some fuel costs.

      By the way, check out the drawings of the probe. It's pretty cool looking. It's got a big radiation shield on the side it tur

  • Stupid rockets... :) (Score:3, Interesting)

    by JCMay ( 158033 ) <JeffMayNO@SPAMearthlink.net> on Tuesday August 03, 2004 @07:33AM (#9868112) Homepage
    We were, of course, some of the first people to know that the Messenger launch had occurred; with TS Alex to our northeast we had winds out of the north and the noise of the launch was exceptionally clear at our house. Woke me up with rattling windows and a low rumble.
  • Mercury is at most 222 hundred thousand kilometers from earth [noblemind.com]. Messenger is traveling 7.9 billion km.

    I know that there is no other good way to get it there, but I just find that interesting. I hope it has something good to read on the trip.
    • 222 hundred thousand?

      Its 222 MILLION km for the maximum, if you insist on counting in hundred thousands, you need 2220 of them, not 222.

      • TY

        I really shouldn't try to do math before coffee. It all started when I was converting miles to kilometers.... On the bright side.. it's correct on my website.

        Do I get brownie points for recognizing that 7.9 billion is a bigger number? That's about the best I've done today.
        • Do I get brownie points for recognizing that 7.9 billion is a bigger number? That's about the best I've done today.

          I would consider that under par for the avarage /. poster, especially on space articles.

    • Reporters always seem to make a big deal about the total distance, but it just comes from the fact that Messenger will be in orbit around the sun for a long time as it uses the occasional planetary swingby to adjust its orbit. In the six-and-a-half years until Messenger begins orbiting Mercury, the Earth will have travelled 6.1 billion miles in its orbit, and Mercury will have travelled 9.8 billion miles in its orbit. Since Messenger's orbital speed will be changing gradually from one to the other, natura
  • When is next solar max? What are the odds of a solar
    flare hitting it before it orbits mercury? What ar ethe odds of a solar
    Flare hitting it early on in its orbit of mercury? Isn't mercury struck by solar flares
    from time to time?

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