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Ion-Engine Spacecraft On Moon Mission

Posted by timothy on from the get-rutan-on-the-case dept.

anactofgod writes "The Times On-line and space.com reports that the European Space Agencies Smart-1 probe has cleared the Lagrangian point between the Earth and its moon and is due to enter lunar orbit on Nov 15th. Smart-1's mission is to make observations related to the moon's formation and composition. What's cool about this mission, other than this is the first European mission to Earth's moon, is that the probe is using solar powered ion engine thrusters. Ion engines are an order of magnitude more efficient than chemical engines. NASA flew the first ion-powered spacecraft, Deep Space 1, in 1998. Smart-1 is the second spacecraft to use the technology, and was designed as a testbed for future ESA missions. The ESA is scheduled to fly the ion-powered BepiColombo on a mission to Mercury in 2009."

38 of 43 comments (clear)

  1. Re:Better description by azav · · Score: 3, Informative

    The lagrange point is where the gravity from the moon offsets the gravity from the earth, making a point where there is no gravitational pull towards either body.

    --
    - Zav - Imagine a Beowulf cluster of insensitive clods...
  2. Re:Better description by srstoneb · · Score: 5, Informative

    The lagrange point is where the gravity from the moon offsets the gravity from the earth, making a point where there is no gravitational pull towards either body.

    Not quite -- it also includes the "centrifugal" pseudoforce. The Lagrangian points are fixed points within the rotating reference frame of the Earth/Moon system. Because the frame rotates, it is not an inertial frame, so pseudoforces contribute. If the Earth and Moon were held in place magically, instead of orbiting each other, the balance point between us would be in a different location than it is when the system rotates.

    Also, of course, there are five Lagrangian points, only one of which is physically between the Earth and Moon. If only gravity mattered, it would be the only one. The other four arise thanks to the contribution of pseudoforces.

  3. Nuclear Thermal vs. Ion Thruster designs by justanyone · · Score: 3, Interesting

    I heard recently about a new Nuclear Thermal design (in http://www.wired.com/). I'm wondering if this is better (higher ISP per unit cost) than an Ion thruster.

    Obviously, if you're headed inbound into the solar system, you're destined for more light therefore more available energy. And, going outbound (Pluto-wise), sunlight gets scarce. So, where is the breakeven? Solar panels cost weight, and Ion engines mass a lot for the miniscule thrust they generate. Nuclear thermal (or Nuclear/Ion) combinations also mass a lot but have the added advantage of much higher available thrusts for short bursts if needed.

    What about pairing Nuclear thermal with Ion thrusting? Generate a plasma by heating it with a slow fission or plutonium decay reaction, and also generate electricity from the waste heat. Use the electric power to do microwave heating. Or, directly accelerate the plasma ions using a magneto-hydrodynamic MHD setup?

    Is anyone actually actively developing anything like this? It seems to me that the fundamental limitations of our current space delivery systems are NOT who can build a better mousetrap, but that all the mousetraps are using cheese (LH2+LOX) instead of peanut butter (NTR, MHD, Ion engines, etc.).

    Also, are there any somewhat-better-than-rumors of USAF designs using these that are flying but that people can't talk about?

    --
    Unitarian Church: Freethinkers Congregate!
    1. Re:Nuclear Thermal vs. Ion Thruster designs by anactofgod · · Score: 2, Informative

      Ion thruster designs have an Isp that start at 3500, and can potentially go much higher. Nuclear thermal designs have an Isp ranging from 825 to 925. By comparison chemical reaction rockets have low specific impulses, ranging from 150-450.

      --

      ---anactofgod---

      "Equal opportunity swindling - *that* is the true test of a sustainable democracy."
    2. Re:Nuclear Thermal vs. Ion Thruster designs by Christopher+Thomas · · Score: 2, Interesting

      Nuclear thermal is limited by the need to keep the exhaust temperature to something the core materials can withstand. Ion drives have no such limitation, and can in principle achieve exhaust velocities close to C (though in practice you'd never want to build a drive that did this). This gives ion drives far higher Isp.

      You can in principle build a magnetically confined nuclear thermal drive that holds a uranium plasma in a magnetic field and reaches very high temperatures, but this turns out to have many practical problems (not the least of which is a fairly large minimum size), so don't expect it to be done soon.

      Nuclear-electric drives are the way of the future for craft outside the inner solar system. They use a small fission plant to generate electricity, which then drives an ion drive or hall effect thruster or plasma drive or what-have-you.

    3. Re:Nuclear Thermal vs. Ion Thruster designs by cjameshuff · · Score: 2, Interesting

      Look into gas core rockets a bit more. The confinement is inertial, not magnetic...though magnetic fields might be used for controlling the vortex. In the "nuclear lightbulb" form, the gas core surrounds a cylinderical quartz window cooled by liquid hydrogen. The working mass is forced through the center, and is heated by radiant UV. However, you are basically correct...none have been built, they would need to be big, and the biggest problem is finding materials and cooling systems that can handle the extreme temperatures. (Up to 55000 K)

      Nuclear electric is fine for probes...higher efficiency, and very long operation times. However, for many things they are simply too low-thrust. Nuclear thermals spit out greater amounts of reaction mass at a lower velocity than ion thrusters, and can't produce as much delta-v from a given amount of propellent, but they are far better than chemical rockets and produce much greater thrust than ion thrusters. I think they are most promising for any manned craft and unmanned craft that need to make high-acceleration maneuvers.

  4. Re:Better description by Cade144 · · Score: 4, Informative

    A nifty diagram is available here.
    As I seem to recall, there are a group of asteroids in the L4 and L5 points (with regards to the Sun and Jupiter) called the Trojan Asteroids. Not shure that this is relevent, but the factoid just popped into my head.

  5. Interesting ... by gstoddart · · Score: 1

    In terms of number and diversity of missions, the ESA actually seems to be a lot more active than NASA overall. (That might just be perception, who knows.)

    Does anyone have any info on the relative activities/funding of NASA vs ESA?

    It's super cool that they're experimenting with newer propulsions sytems and the like.

    --
    Lost at C:>. Found at C.
    1. Re:Interesting ... by wertarbyte · · Score: 1

      According to this, ESA has a budget of 2700 million. It is paid by its members proportional to their gross national product as some kind of "base funding" and optional donations for specific additional projects.

      --
      Life is just nature's way of keeping meat fresh.
    2. Re:Interesting ... by stevesliva · · Score: 1
      In terms of number and diversity of missions, the ESA actually seems to be a lot more active than NASA overall. (That might just be perception, who knows.)
      No offense, but you are indeed suffering from misperception. NASA's Deep Space 1 used ion propulsion 6 years ago. NASA's Lunar Prospector orbited the Moon, also 6 years ago, and before that in modern lunar probe history there was Clementine, from the US, but not NASA. And don't forget the current missions-- Stardust comet sample return mission, the Messenger Mercury mission, the Mars rovers, two Mars Orbiters, and the Deep Impact mission about to launch to smash into a comet. NASA/ESA also are collaborating on Cassini/Huygens at Saturn now.
      --
      Who do you get to be an expert to tell you something's not obvious? The least insightful person you can find? -J Roberts
    3. Re:Interesting ... by VanillaCoke420 · · Score: 1

      Ion propulsion is done by Japan as well, on their latest asteroid sample return mission. Soviet experimented with ion thrusters back in the 60's. Also don't forget the current Rosetta mission - the first probe to land on a comet. And as for Venus we have Venus Express, Mercury we're collaborating with Japan on the Bepi-Colombo. Also, within the frameworks for the Aurora programme, ESA is working on a Mars rover and a Mars sample return mission.

  6. Re:Better description by centauri · · Score: 5, Informative

    You can see a picture of the Trojan asteroids here. Jupiter is on the left of the page and revolves counter-clockwise. The trailing Trojans at L5 are 60 degrees behind Jupiter, near the top of the picture and the leading Trojans are, of course, 60 degrees ahead, near the bottom of the page. There are also a smattering of bodies around the L3 point. The Solar-Jovian L3 is closer to Jupiter's orbit than the diagram in the parent post would indicate.

    Sometimes, the L4 and L5 Lagrange points of a system are called Trojan points.

    This site mentions how the prominent asteroids at the Trojan points are named after characters from the Iliad. One group is named after Greeks, the other after Trojans. Each group also has a "spy" in its midst.

    --
    Don't blame me, I voted for Durga.
  7. Nuclear rockets by Cuchullain · · Score: 1

    I don't have an answer for you, but I think that the idea of powering a ion thruster with nuclear material is an interesting one. The question is whether the mass required to generate power for a reasonable amount of time is more than the mass of solar panels to power it for a similar amount of time.

    It seems like such a logical design change that I am sure it has been considered. It would totally kill the level of complexity though, which may be enough to kick it out of practicality regardless.

    Cool stuff in general though. The idea of low levels of constant acceleration is very attractive for long distance probes. Not necessarily fast enough for manned missions though.

    Cuchullain

    --
    "If sharing a thing in no way diminishes it, it is not rightly owned if it is not shared." -St. Augustine
    1. Re:Nuclear rockets by anactofgod · · Score: 3, Insightful

      It's not technically complex. It's politically complex.

      The problem all nuclear powered designs have is the fact that they are nuclear powered. It's hard to convince J. Q. Public that it's okay to launch any kind of nuclear reactor design into space, especially when said material is being launched via highly combustible chemical rockets. No one would want to be in charge of the cost-benefit of making the design and launch decisions the first time a launch like that goes bad.

      --

      ---anactofgod---

      "Equal opportunity swindling - *that* is the true test of a sustainable democracy."
    2. Re:Nuclear rockets by mars75 · · Score: 1

      The fact that certain payloads are nuclear isn't that much of an issue. Most nuclear payloads are actually very safe isotopes. A colleage of mine has , on several occasions, handled Plutonium without any protection. Not all nuclear materials are weapons-grade and they do decay in a very civil way!!!

  8. Re:Better description by centauri · · Score: 1

    I looked on wikipedia, but was turned off because of the spartan nature of the article.

    Not "spartan." "Trojan."

    --
    Don't blame me, I voted for Durga.
  9. But before that comes... by Engineer-Poet · · Score: 1

    Smart-86, which will almost get to its destination but will wind up saying "Missed it by that much!"

    --

    Sustainability and energy independence essay
  10. A fisking of TFA by Engineer-Poet · · Score: 4, Informative
    Too many newspapers use scientific illiterates to write their science coverage. The Times of London appears to be one of them, if we consider the quality (or lack thereof) of TFA.
    a Star Trek-style thruster
    Star Trek postulates warp drives (which we have no idea how to build) and "impulse engines". Ion drives are impulse engines, but all rocket motors are impulse engines too.
    Had the ion drive fallen just 5 per cent short of maximum thrust, Smart-1 could have collided with the Moon.
    It's completely opaque to me how this could be the case. If you don't have enough thrust for one trajectory, you use another.
    They work by using electricity from solar panels to charge atoms of the noble gas xenon, which are then fired into space at 1,000mph to power the probe.
    The author is obviously innumerate. Impulse of the DS-1 engine peaked at 3100 seconds, for an exhaust velocity of ~30 km/sec. That is not 1000 MPH, it is about 68000 MPH.
    This stream of ions accelerates Smart-1 at just 0.2millimetres per second.
    Per second squared.
    In space, this builds up over time to generate speeds of up to 10miles per second, or 36,000mph.
    Except that a mission to the Moon never gets to such speeds; the spacecraft slows down as it spirals outward. Orbital velocity of the Moon around Earth is only about 2200 MPH.

    Why newspapers publish drivel like this, I'll never know. If it was hard to get right you wouldn't have amateurs fisking this stuff on Slashdot!

    --

    Sustainability and energy independence essay
    1. Re:A fisking of TFA by radtea · · Score: 1


      The most irritating thing about this is to see a NASA article full of sensible units mN, kW and the like, and then report Isp in "seconds", a dimensionally incorrect anachronism from the days when men were men and pounds was the name for both a unit of mass and a unit of force.

      Could we please start reporting Isp in N*s/kg?

      --Tom

      --
      Blasphemy is a human right. Blasphemophobia kills.
  11. Ion powered? by DaveJay · · Score: 1

    So, what, it's got an engine from General Motors' latest economy car? If so, I hope it goes on a mission to the ringed planet next.

  12. Earlier slashdot article about this by cruff · · Score: 1

    This is a recent article from earlier in the week about this mission.

  13. Too Damn Slow! by reallocate · · Score: 1

    This thing took a year to get to the Moon. Yes, it's a testbed for ion propulsion, but if it takes a year to get to the Moon, ion engines aren't going to help us much.

    We need propulsion technology that moves bigger things faster, not smaller things slower.

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    -- Slashdot: When Public Access TV Says "No"
    1. Re:Too Damn Slow! by cjameshuff · · Score: 1

      For probes, we need technology that moves things farther for a given mass. That's exactly what ion engines do. They use reaction mass far more sparingly, throwing out a smaller mass at a far greater velocity than chemical rockets. By doing this, they can achieve a given change in velocity using a much lower mass of fuel. Smart-1 doesn't need to get to the moon faster than this, and by using ion engines to maneuver once it's in space, it can carry more scientific payload and still have plenty of maneuvering capacity after it reaches its destination.

      The benefit is even greater for probes to the outer solar system, or really to any location with a significantly different orbit from Earth's. Chemical rocket boosters capable of accelerating probes enough to send them a significant distance would be huge in comparison to the ion drives, requiring larger launch rockets to get off the ground and cutting into the useful payload.

    2. Re:Too Damn Slow! by R.Caley · · Score: 1
      We need propulsion technology that moves bigger things faster, not smaller things slower.

      No, we need to send bigger things further. Ion engines are good for that.

      Elapsed time is hardly very important, unless you build your space probes from fragile components with very short working lives. The moon will still be there if your probe takes 10 years to get there, let alone one.

      --
      _O_
      .|<       The named which can be named is not the true named
    3. Re:Too Damn Slow! by reallocate · · Score: 1

      Any engine that gets to escape velocity will send anything anywhere, given enough time.

      The whole point of space exploration is to put people there, not treat it as some curiosity to be explored at great leisure with research probes. The speed we can travel in space needs to increase for the same reasons we work so hard to increase the speed of travel on Earth.

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      -- Slashdot: When Public Access TV Says "No"
    4. Re:Too Damn Slow! by R.Caley · · Score: 1
      The whole point of space exploration is to put people there

      Says who?

      People are the most obvious example of fragile components with short working lives which therefore should not be used in space exploration.

      Even if you think the only reason for interest in the rest of the universe is to eventually send people (a rather bizzare POV implying a remarkable lack of curiosity), clearly we're well below the level of technology and knowledge at which it makes sense to do that now. Does that mean all space exploration should stop of 50 years or a century?

      --
      _O_
      .|<       The named which can be named is not the true named
    5. Re:Too Damn Slow! by reallocate · · Score: 1

      Says me. We've had the technology to base people on the Moon since the 1960's, as well as to travel to Mars. It's only lack of will and intent that's kept that from happening. There's no reasonto wait.

      Curiosity had everything to do with it, but it is a curiosity that can't be satisfied with machines. The purpose of using automated probes is to learn, and the primary reason to learn about a new place is to enable people to travel to that place. If I want to live in a different country, that desire can't be met by flying an unmanned probe overhead.

      This "We're Not Ready" attitude makes no more sense to me than one that would have seen the Europeans decide to stay in Europe until they invented air conditioning, indoor plumbing and the airplane. My ancestors took months getting fromn Europe to North America. I'm rather glad they did not wait.

      --
      -- Slashdot: When Public Access TV Says "No"
    6. Re:Too Damn Slow! by R.Caley · · Score: 1
      We've had the technology to base people on the Moon since the 1960's, as well as to travel to Mars.

      And they've been hiding this technology inthe same hanger as the ever lasting lightbulb and the car which runs on water?

      [...]the Europeans decide to stay in Europe until they invented air conditioning

      More to the point is the fact that they didn't set out into the atlantic until they had invented the boat.

      Current state of the art in manned space travel is to either:

      • Stick a test pilot in a can and balance that on the top of a firework, aim that at the moon and pray there isn't a solar storm, a meteor strike or other everyday occurance, or
      • put some people in an airtight trailer-home just far enough up that the atmospheric drag isn't too bad and pray you can get them back down before their bodies start falling apart.

      On the `crossing the atlantic' technology scale, this is somewhere around `grab onto a fallen tree trunk and start paddling West'.

      --
      _O_
      .|<       The named which can be named is not the true named
    7. Re:Too Damn Slow! by reallocate · · Score: 1

      Well, you must have missed it. We've been to the Moon, 35 years ago. There were plans -- not dreams or idle wishes -- to establish a permanent presence and push on to Mars in the 1980's. The only reason that did not happen was a failure of political will and intent, especially in the Nixon administration.

      As for you "crossing the Atlantic" schtick, are you arguing that Prince Henry and Columbus should have waited until they had the technology to build the Queen Mary, rather than go exploring with little wooden ships and no refrigeration?

      Try again when you have a better notion of what you're talking about.

      --
      -- Slashdot: When Public Access TV Says "No"
    8. Re:Too Damn Slow! by R.Caley · · Score: 1
      Well, you must have missed it. We've been to the Moon, 35 years ago.

      Er, yes, I pointed out how far from a workable technology that was.

      Yes, if we had continued to work forward from there we might have a level of technology to do real earth-moon travel to support an outpost there by now, but the point is that we don't. The USSR moved to learning enough about themedical problems to try for an apollo-style publicity stunt to mars. The USA more or less gave up on manned space exploration, just sending men along for the ride to LEO on the Scuttle. With the fall of the USSR, the USA has taken up their space medicine programme.

      Meanwhile, the unmanned space programme has done lots of really fun stuff through most of the solar system. On the whole I think one Cassini is worth more than the whole shuttle programme from day one to when they finally get rid of the embarassing thing.

      --
      _O_
      .|<       The named which can be named is not the true named
    9. Re:Too Damn Slow! by reallocate · · Score: 1

      You apparently don't think Apollo was "real earth-moon travel". You also apparently agree that we had the capability to stay on the Moon, but only failed to do so thanks to a lack of will and intent. I agree that the Shuttle was and is a purposeless vehicle, but the fact that the Nixon admininstration chose it rather than to proceed with the post-Apollo Moon/Mars plans laid out by the Johnson administration is simply the manifestation of that lack of will and intent.

      If we had the possessed the will, we could have had a Lunar base by in the 1970's, and a Martian expedition in the 1980's. There was and is no need to wait until we have developed the equivalent of the 747 before exploring space.

      As for probes, they are no subsititute for a human presence in space. The exploration of space is not a research venture.

      --
      -- Slashdot: When Public Access TV Says "No"
    10. Re:Too Damn Slow! by R.Caley · · Score: 1
      You apparently don't think Apollo was "real earth-moon travel".

      In the sense that the Wright Flyer was not a real method of air travel. It was a point from which development could begin, but no one was going to start scheduled passenger or freight services using that technology.

      You also apparently agree that we had the capability to stay on the Moon, but only failed to do so

      No, I said we might have had by now -- ie we were 30 years development away from that point. We are perhaps 20 years away now -- developments in technology have happened for other reasons which would be a help -- plus maybe 5-10 years to go from a standing start to a manned space programme (which could happen in parallel).

      As for probes, they are no subsititute for a human presence in space.

      I didn't say they were. I said they did a different and more immediatly interesting job.

      The exploration of space is not a research venture.

      As I said, you show an amazing lack of curiosity.

      --
      _O_
      .|<       The named which can be named is not the true named
    11. Re:Too Damn Slow! by reallocate · · Score: 1

      >>"...the Wright Flyer was not a real method of air travel. It was a point from which development could begin, but no one was going to start scheduled passenger or freight services using that technology."
      One, you seem to be arguing that the Wrights should not have flown because 1903 technology wasn't capable of supporting scheduled service. Two, the ability to operate scheduled passenger/freight service is not a prerequisite for human space exploration.

      Technology will not develop by itself; it does does not grow and develop at a steady rate. Something -- the Wrights or Apollo -- must drive interest and demand for that technology. E.g., absent the Wrights, scheduled service in large airliners would not have sprung magically to life decades later when the technology was ready. It wouldn't have happened at all because the technology would not have been developered.

      >>"...we were 30 years development away from that point. We are perhaps 20 years away now...

      The rest of this statement is difficult to parse, but if you are saying we lacked the technology in the 1970's to establish a permanent human presence on the Moon, and to conduct a human mission to Mars in the 1980's, I fundamentally disagree.

      >>"...you show an amazing lack of curiosity."

      Just the opposite. How can research data transmitted by a machine compare with actually being there yourself? My curiosity is not satisifed by venture like Cassini or Spirit and Opportunity. Just the oposite. Everytime I see a finding or an image from one of those missions, I can't help but ask how much more we would learn, how much faster we would learn, if we had people there instead of these unthinking and incurious machines.

      --
      -- Slashdot: When Public Access TV Says "No"
    12. Re:Too Damn Slow! by R.Caley · · Score: 1
      One, you seem to be arguing that the Wrights should not have flown because 1903 technology wasn't capable of supporting scheduled service.

      Er, no, I was saying that no one should have tried to set up a scheduled friegt service using clones of the Wright Flyer.

      if you are saying we lacked the technology in the 1970's to establish a permanent human presence on the Moon, and to conduct a human mission to Mars in the 1980's, I fundamentally disagree.

      Are you imagining creating and supplying a moonbase with a technology which was barely capable of putting 2 men on the moon with supplies to last a few days, at huge cost per flight? As for mars, we still don't know what we'd need to know from the medical end, and that is one of the few areas which has been worked on continuously from then to now. All the hard technology is decades away even from an Appolo style spam in a can mission.

      How can research data transmitted by a machine compare with actually being there yourself?

      Ever used a microscope? how much faster we would learn, if we had people there instead

      You mean people not using instruments? We'd learn a huge amount that way, honest. If you gather the information through an instrument, why does it matter if the instrument is split in half, and the bit manipulated by a human being is on Earth?

      There may be a small benefit in some cases of having a human being driectly manipulate the instrument without time delay, but the cost, compexity and danger of sending someone up there just to do that is not going to be justified until we are orders of magnitude better at everything than we are now. And even then, most of the really intersting places are just off limits to people. Or are you going to volunteer to burn up plunging into the atmosphere of Saturn or spend 10 years in a weird orbit pointing instruments at the Sun or whatever?

      You are not talking about curiosity, you said it, you aren't interested in finding anything out, `not a research project'. You are talking about tourism, going there, staying at the Holliday Inn, eating whatever you'd eat at home, taking the same photos every else has before you of things you don't know anything about and flying home.

      I'd love to have been an Appolo astronaut, but that is not curiosity. They didn't come back knowing more than when they went. They left some instruments and brought back some rocks so people who didn't go got to learn things. You will not there were no scientists sent to the moon (I think one guy was an ameteur geologist).

      --
      _O_
      .|<       The named which can be named is not the true named
    13. Re:Too Damn Slow! by reallocate · · Score: 1

      >>"...no one should have tried to set up a scheduled friegt service using clones of the Wright Flyer..."

      More to the point, no one would have been able to set up a scheduled freight service without the Wright Flyer's existence. The technology to sustain that service would not have otherwise developed. As I said, technological progress is not a steady-state exercise. The reason that we developed the infrastucture and technolgy that allowed scheduled air service is that the Wrights, and their successors, developed the technology that created the demand for that service. It just doesn't make sense to avoid doing what you are capable of doing because you want to wait for something else to come along. In most cases, that "something" won't come along. If we don't traveling in space using the capabilities we have today, no demand will exist to create better technology.

      NASA's post-Apollo plans included use of nuclear-powered stages in Saturn follow-on vehicles. These would have provided the lift and the speed needed to reduce a transit to Mars to a few months. That's easily within tested human capabilities. These, and other vehicles, would have also supported and sustained a permanent lunar presence.

      As for research and robotics, of course they are important and necessary. I did not say I am not "interested in finding anything out". That's a scarecrow argument you've fabricated. But the purpose of establishing a human presence in space is no more wholely research than was the purpose of peopling the planet. We live, and will live, where our technology allows us to live. (Without technology, humans would still be confined to equatorial Africa.) We conduct research to determine what our technology needs to do to support us. We also use research in purely scientific endeavors, i.e., Cassini. Doing one does not preclude the other.

      The purpose of Apollo was not to do scientific research, or to satify a someone's curiosity. It was to send people to the Moon. If we had not walked away, there would have been plenty of science done on the Moon. And, btw, the guy was a professional geologist, not an amateur.

      --
      -- Slashdot: When Public Access TV Says "No"
  14. More info by weeboo0104 · · Score: 1

    Here's a picture of the ion craft that went to the moon.

    --
    It is easier to build strong children than to repair broken men. -Frederick Douglass
  15. My mistake by weeboo0104 · · Score: 1

    That was no moon, it was a space station.

    --
    It is easier to build strong children than to repair broken men. -Frederick Douglass
  16. Re:Better description by kettlechips · · Score: 1
    This talk of langrangian points and thrust by small particles made me think of launching a spacecraft straight at the sun. It would deploy a solar sail to slow it down and eventually make it hover at the point where the sun's gravity would be offset by the force created by the solar wind on the sail. The sail would have to be able to expand and contract, compensating for the fluctuations in solar wind force.

    Such crafts would not need to orbit the sun and you could put them almost anywhere. In fact, you could launch them in almost any direction within the solar system and establish the equilibrium between solar wind and gravity.

    And why not provide them with an ion engine? Imagine if the sun went out, the things would simply plummet to their doom otherwise and all the hard work would have been for nothing.