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Space

Ion Rocket to Map Moon with X-Rays 172

Posted by CmdrTaco
jralls writes "The Guardian is reporting that a European ion-rocket has taken the last year to reach the moon and is about to enter lunar orbit. Once it slows and gets into a very low orbit, it will probe the surface with x-rays in an effort to solve the long standing puzzle of the moon's origin."
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Ion Rocket to Map Moon with X-Rays

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  • Visibile from Earth? (Score:3, Interesting)

    by fembots (753724) on Sunday November 07, 2004 @12:07PM (#10746952) Homepage
    I wonder if we are able to observe this interplanetary tortoise from earth? If it passes the bright side in full moon, we should have quite a clear view of it since it's going so slowly.

    Play iCLOD Virtual City Explorer [iclod.com] and win Half-Life 2
    • Why did it take so long to get to the moon?
      • by NetKraft (785677) <artturi@karhula.gmail@com> on Sunday November 07, 2004 @12:23PM (#10747065)
        Ion rockets can't generate very high accelerations. They can, however, keep going for a long time.
        • If we used some sort of higher powered rocket to generate the velocity, I wonder if ion rockets could hold that velocity for a long time.
          • by wertarbyte (811674) on Sunday November 07, 2004 @12:33PM (#10747134) Homepage

            If we used some sort of higher powered rocket to generate the velocity, I wonder if ion rockets could hold that velocity for a long time.

            Since we are using this space, I wonder what we would need the ion rocket for to hold that velocity. In space, there is not much that could slow you down.

            • by Anonymous Coward
              >In space, there is not much that could slow you down.

              True. Unless you are somewhat near a large gravity source that the rocket would have to fight against. The Earth for instance.
          • I don't think there ever were any problems with holding the velocity. Acceleration, however...
            • So the question is, if we used conventional rockets to quickly achieve a high speed, could the ion propulsion continue the excelleration after the rocket burns out?
              • by pe1rxq (141710) on Sunday November 07, 2004 @01:20PM (#10747399) Homepage Journal
                That is exactly what this thing does...Use a conventional rocket to get away from earth's surface and then continue with ion propulsion to the moon.

                Jeroen
                • by Digemedi (790263)
                  The general idea of a ionization engine is obviously sustained impulse (as previously stated).

                  Ionizations engines are typically attatched to probes which have initial combustion engines that give them the thrust required to escape the earth's gravity. Once the probes have escaped gravity, the ion engines allow continual thrust that allow (for extremely long range expeditions) extremely high velocity. It is a competing technology with solar sails - which also allows for huge velocities over long distances
      • It's fairly simple. The ESA doesn't have a rocket capable of putting a payload on a lunar path. AFAIK Arianne is really only good for LEO stuff. The only two countries with lunar capable rockets are I believe the Russians and the USA. Of course, the ultimate lunar capable rocket, the Saturn V, is dead, so all we can do is cross our fingers and hope that NASA will come to its senses and bring back the big dumb booster.
    • I wonder if we'll be able to see the four elephants too.
    • My question is will they be able to see the American flag that *supposedly* resides up there...

      this is assuming that they really *did* land on the moon
    • by dmadole (528015)

      I wonder if we are able to observe this interplanetary tortoise from earth? If it passes the bright side in full moon, we should have quite a clear view of it since it's going so slowly.

      I'm curious what make you think it will be going slowly? It will be orbiting the moon at exactly the same speed as any other craft at the same altitude would be orbiting the moon. The type of engine or thrust has nothing at all to do with orbital mechanics.

    • It's not going slowly, it's going at the same speed anything else in the same orbit would be at. It's taking a long time to reach lunar orbit because it started out in Earth orbit and needs to accelerate quite a bit. It's using an ion engine, so it'll take longer to achieve a given change in velocity. A conventional rocket would achieve the same change in velocity more quickly, but the end result would be basically the same...except that the conventional rocket would be bigger and heavier, and thus more exp
  • by mfh (56) on Sunday November 07, 2004 @12:07PM (#10746953) Homepage Journal
    Place your bets!

    I say the moon came from Uranus, what do you say? Here take a survey [opinionpower.com]!

    Survey...

    Uranus
    Another Galaxy
    Mars-sized planet crashed into the earth
    Comet
    Meteor
    Microsoft
    Another Dimension
    It was a spaceship!
    Cowboy Neal
  • Great title (Score:5, Funny)

    by Chairboy (88841) on Sunday November 07, 2004 @12:08PM (#10746966) Homepage
    I expected the story to read "But when Flash Gordon approaches, will the moon people fight back with their electro-guns? Watch next week to find out!"
  • Moon mining? (Score:5, Interesting)

    by FiReaNGeL (312636) <fireang3l&hotmail,com> on Sunday November 07, 2004 @12:11PM (#10746986) Homepage
    From the article :

    "The sun emits X-rays and these are reflected back into space by atoms on the Moon's surface. A magnesium atom will reflect an X-ray in a different way from an iron atom, and Grande's detector can detect these differences.

    Flying over the lunar poles, so that it covers the entire Moon as it revolves below, Smart will create strip maps of the surface - and eventually a global map of its composition."

    Look like useful data to me if we were in the 'mine the moon' business... maybe in a not so distant future?
  • I keep hearing that Ion propulsion is faster than what we currently use. What's with the incredibly slow travel time?
    • by SpryGuy (206254) on Sunday November 07, 2004 @12:15PM (#10747009)
      The ultimate speed of ion propulsion is higher than that of chemical propulsion.

      But the mass being expelled at high speeds (the ions) is so low, that accelleration is VERY slow. So it takes a long time to get up to speed, but the maximum speed you can theoretically reach is much greater than that of chemical rockets.
      • by GileadGreene (539584) on Sunday November 07, 2004 @12:33PM (#10747131) Homepage
        Actually, the maximum speed that you could theoretically reach is the same in both cases: c

        The difference is that it will take a chemical rocket much more propellant to get there, because it is far less efficient in its use of propellant mass (i.e. it has a lower specific impulse).

        • I thought nithing with a mass could be accelerated to c since it would take an infinite ammount of energy to accelerate it to c since the mass of the object grows the more it reaches c.
        • by Evil Pete (73279) on Sunday November 07, 2004 @04:25PM (#10748697) Homepage

          Look up any reasonable book on mechanics and you will find a formula for the final velocity of rockets that have a empty mass M, mass of fuel m, and have an exhaust velocity v. The final velocity of the vehicle is ...

          V = v . ln( (M + m)/M )

          In other words ion rockets will beat chemical rockets because they eject their exhaust at a reasonable fraction of c, whereas chemical rockets have exhaust velocities more like velocities we see on earth (e.g. bullets). So chemical rockets need lots of mass, but that's ok because they throw out lots of mass. Trouble getting to space is expensive ... each kilo of fuel you put in orbit better be wisely used ... so in space ion rockets make sense (apart from the fact you can't use them on Earth anyway ... wouldn't be able to lift off even).

          Hope this makes things a bit clearer.

      • I think they should have used Twin Ion Engines [wikipedia.org] to get a little better acceleration...
      • by Brett Buck (811747) on Sunday November 07, 2004 @02:40PM (#10747897)
        > The ultimate speed of ion propulsion is higher than that of
        > chemical propulsion.

        Depending of course on the fixed mass of the spacecraft, vs it's propellant mass, of course. You get more momentum change from given amount of propellant, but if you only had a teaspoon full of propellant, or the spacecraft was exceptionally massive, you wouldn't get more velocity.

        > But the mass being expelled at high speeds (the ions) is so
        > low, that accelleration is VERY slow. So it takes a long
        > time to get up to speed, but the maximum speed you can
        > theoretically reach is much greater than that of chemical
        > rockets.

        To expand, the measure of efficiency of a rocket engine is the specific impulse or ISP. It's how much momentum change you get per unit of propellant mass, and the usual unit is seconds (lb-sec/lb). The highest actually-achievable ISP from a chemical rocket is somewhere in the 475 seconds. The Saturn 5 first stage was more like about 350, and monopropellant thrusters used for many satellite propulsion systems is more like 150-180! That means that if you want to change the velocity a lot, you need a whole lot of propellant.

        I'm not sure which engine this particular program uses, but the ISP of the typical Xenon ion thruster is something like 1800. So you have to carry fantastically less propellant for a given velocity change, meaning it can weight less at liftoff, meaning you can use a weaker/cheaper booster.

        The downside is that you don't get something for nothing. It takes, not surprisingly, a whole lot of electrical power to make it go. So you put in 4000-5000 watts of power, and it only generates .04 lb of thrust - .64 of an ounce, pushing a spacecraft weighing thousands of pounds on the ground. So the acceleration is very small, meaning takes a long time to get going. The other downside is that the Xenon ions, although chemically pretty neutral, shoot out at such high speeds that anything that gets in the exhaust gets eaten away. This may or may not be an issue depending on there you put it relative to the rest of the spacecraft.

        Brett
    • by Anonymous Coward
      They are using euro ions, which require extended committee meetings and discussions before determining the appropriate direction in which to apply their force.
    • What you heard is that the specific impulse is way larger than with chemical, meaning that the exhaust velocity is very high. That means that you have a very efficient means of propulsion, with each particle of exhaust producing more thrust/particle than chemical rockets do. The exhaust being a tenuous gas however, the actual THRUST is very low (and the thrust/weight ratio even more so). Because it works in the vacuum of space and can run for years on end, the eventual velocity that this low thrust can impa
    • shouldnt this have had a fairly substantial speed to start? Ie, the space torch orbits about 29,000 Km/hr which is about the minimum for low earth orbit.
  • by Anonymous Coward
    Anyone still using film up there is going to be pissed when their exposures are ruined.
  • by bs_02_06_02 (670476) on Sunday November 07, 2004 @12:16PM (#10747017)
    Everyone learns that the moon is made of cheese in the cartoons. I bet they'll say it's from Wisconsin.
  • Finally we can have proofs that the moon is made out of cheese..

    I do hope it's cheddar..
  • Will these guys be able to snag some good shots of the trash we left on the moon? Exluding the flag of course, which can't be trash cuz its on a stick.
  • Isn't that the way the monolith will be found?
  • wow (Score:5, Funny)

    by flacco (324089) on Sunday November 07, 2004 @12:25PM (#10747077)
    sobering thought that that headline sounds exactly like something you might hear in a pulp sci-fi movie from the 50's...
    • Re: wow (Score:2, Funny)

      by Black Parrot (19622)


      > sobering thought that that headline sounds exactly like something you might hear in a pulp sci-fi movie from the 50's...

      Science has finally caught up with fiction!

  • by jdkane (588293) on Sunday November 07, 2004 @12:41PM (#10747179)
    Smart's map should provide that data and show if scientists are right in believing that the Moon coalesced from a vast ring of debris generated when an ancient planet the size of Mars destroyed itself after crashing into Earth. Understanding the origins of the Moon will therefore give insights into the nature of our planet.

    Doesn't this mean earth should have some huge dent in it, and not be so round? Look at the sizes of Mars and Earth [nasa.gov]. Are you surprised earth is still here after a crash of that magnitude? I am. Maybe earth was a lot bigger before a Mars-like planet destroyed itself crashing into earth, but then I go back to my question about the roundness of the earth.

    Maybe someone more knowledgeable wants to talk about that. The article doesn't go into any great detail on that, which causes a lot of questions to be raised.

    • by Anonymous Coward
      The eart wasn't a solid mass 4 billion years ago. It was molten.
    • by Anonymous Coward
      Any planet (or asteroid, or whatever) above a certain mass will become spherical under its own gravity. I don't have the numbers at hand, but it is surprisingly low, if I recall correctly it would have to be roughly 30 miles wide to have enough mass.
    • I saw something on the Science Channel about this, and the illustration they had involved the two planets hitting each other and swirling around a bit. Since the earth is mostly moltent rock, I think during the collision, a lot of that came in to fill it in. Plus this was a long long time ago, so the Earth could have covered it up by now. Not the best explaination I know, I can't say I understand it all myself.
    • Don't forget that the Earth was molten at the time, and even if it wasn't, look at what is left of the Yuccatan crater due to the forces of erosion. Wind and water are very, very powerful forces.
    • by Anonymous Coward
      There was once a theory that the Pacific Ocean was the hole left when the moon was pulled out of the Earth, but...

      There is a reason why small objects, like asteroids, are often irregular in shape, while large objects, like planets, tend to be nearly spherical. All parts of an object are attracted to each other by gravity, this tends to pull the object into a spherical shape. Above a certain size (which depends on the materials involved) the object is not strong enough to maintain its shape and collapses
    • Biq == Round (Score:5, Insightful)

      by DumbSwede (521261) <slashdotbin@hotmail.com> on Sunday November 07, 2004 @01:21PM (#10747404) Homepage Journal
      Beyond a certain size, gravity pulls things into a spherical shape. The immense pressure makes the insides molten and irregular structures eventually sink down in. Mars has Mons Olympus, the tallest volcano in the solar system, this is because Mars is smaller and has less gravity than Earth. The larger the planet the more regular it has to be. Asteroids can be highly irregular because they haven't the size and gravity to collapse them into spheres.

      The mountains on Earth may appear huge to us insects on the surface, but from a distance the earth appears as smooth as a billiard ball.

      Ironically this event was so big, that unlike latter smaller hits, all evidence in the way of dents will be gone as the entire globe virtually liquefied and coalesced again. Though I wouldn't rule out some exotic mass distributions that might lend evidence of it.

    • by barakn (641218) on Sunday November 07, 2004 @02:46PM (#10747935)
      Take a look at the moon. Those dark spots are the sites of enormous ancient impacts. They may have been holes briefly, but they then filled up with lakes of lava. As far as the Earth goes, the impact was so devastating that the outer layers of the Earth had to reform by falling back down.

      The following contains some links to mostly non-technical explanations of planetary roundness. I'd like to point out that part of this explanation [sciam.com], by "Derek Sears, professor of cosmochemistry at the University of Arkansas and editor of the journal Meteoritics and Planetary Science," is wrong. He says "Planets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it." But this is a circular argument (pardon the pun). Generally a non-spherically symmetric distribution of matter doesn't have a gravitational field that acts as if it originates from the center of the body (the "center" being the center of mass). Spherically symmetric mass distributions do have this special property, so what Sears really implied is that planets that are already round will have gravitational fields that point towards the object's center of mass. This does absolutely nothing to address cases of objects that deviate from perfect roundness, i.e. all celestial bodies. This explanation [astronomycafe.net] by Dr. Sten Odenwald suffers from the same argument, and there's even a hint of it here [nasa.gov]. Nonetheless, these explanations are approximately true, and require bizarre shapes to break them.

      For example, imagine a homogenous, perfectly shaped doughnut (a torus with a circular cross section). At the center of the doughnut hole we'd feel no gravitational field at all (a perfectly balanced tug-of-war). But deviate from the exact center just a tiny amount, and the closer side of the doughnut becomes more attractive than the other. One suddenly experiences a gravitational field that points away from the center of mass.

      • For example, imagine a homogenous, perfectly shaped doughnut (a torus with a circular cross section). At the center of the doughnut hole we'd feel no gravitational field at all (a perfectly balanced tug-of-war). But deviate from the exact center just a tiny amount, and the closer side of the doughnut becomes more attractive than the other. One suddenly experiences a gravitational field that points away from the center of mass.

        Do you have a link to a proof of this? I know that this is not the case for a

      • I don't know the deep maths (didn't do anything like that in my maths degree...) but one issue occurs to me: are objects with very different gravitational fields stable? If a roughly spherical shape is deformed (plastic flow due to gravity, impact, fragmentation, accretion, whatever), then its gravitational field will maintain a roughly spherical shape; but is that true of toroidal objects, for example?

        I wouldn't be surprised if the majority of shapes with radically non-spherical gravitational fields are

    • It was Lister playing Planet Pool. "Played for and got!"
    • Well, maybe that explains why we have continents which do not cover all of Earth's surface? (Reminder: The sea floor is a different material than the continents!)
  • Free X-rays for all Moon residents. Take that Canada!
  • by boola-boola (586978) on Sunday November 07, 2004 @01:05PM (#10747306)
    ....what happened when they probed Mars with X-rays! Watchout! (is Gary Sinise piloting?)
  • Scientists believe nuclear-powered ion-drives are their only real hope of exploring deep space, and vigorously support their development. Not surprisingly, anti-nuclear protesters, like the Global Network Against Weapons and Nuclear Power in Space, have pledged opposition.
    Too much time on Slashdot. Any group that starts GNA... automaticly activates my mental filters. (No great loss in the case of Huggers In Space.)
  • News at eleven.
  • from 'dept' topic (Score:2, Interesting)

    by deunan_k (637851)
    Posted by CmdrTaco on 01:06 AM -- Monday November 08 2004
    from the dept.


    I've always read the 'from the so and so and whatever dept' cuz it's humourously funny and cynic at the same time.

    This time, it's just plain ol' from the dept. I just wonder, whether it is an oversight or CmdrTaco really does not have anything witty to say about it? :-P

    I know, I know it is off-topic, mod me down then.. I probably deserve it.


  • by SimURL (822939) on Sunday November 07, 2004 @03:42PM (#10748317) Homepage
    Ion drive technology allows you to explore space in ways that chemical rockets simply can't.

    Quoting from the article,
    "We have shown that even a small ion engine like Smart's can get us across space. Now we are planning to build space telescopes and robot probes to planets such as Mercury, using bigger and more powerful ion engines. These will take years off space-travel times. Instead of decades-long missions, we will take only a couple of years to cross space for future projects."

    But,
    "Ion engines need electricity and only solar panels can provide enough at present. So ion engine missions will be restricted to planets and moons near the Sun."

    So the solution to deep space exploration is nuclear-powered ion-drives and NASA is working on it.
  • Can any astrogeologists explain why the assumption is that the Moon is a result of debris from a two-planet crash as opposed to regular accretion of debris the way moons were formed on the other planets? Billions of years ago, each planet was a gradually coalescing disc, and the jovian planets still have evidence of this in their rings. The closer planets instead have moons - I assume because the Sun's gravity is stronger at our closer distance from the Sun, and caused the rings of the closer planets to agg
    • Re:Accreted Rings (Score:3, Insightful)

      by cjameshuff (624879)
      It's really freaking big. Mercury and Venus don't have any moons, and the moons of Mars appear to be captured asteroids...relatively tiny rocks not big enough to form themselves into spheres. The Earth-Moon system is nearly a double planet. Of the inner planets, Earth is the only one with a decent moon...and it's a monster compared to the planet.

      In any case, the planets you see now are just the ones that stayed in the system. Material didn't just cleanly accrete directly into the existing bodies. Most of t

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