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Space Science

Ion-Engine Spacecraft On Moon Mission 43

Posted by timothy 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."
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Ion-Engine Spacecraft On Moon Mission More

Ion-Engine Spacecraft On Moon Mission

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  • Nuclear Thermal vs. Ion Thruster designs (Score:4, Interesting)

    by justanyone ( 308934 ) on Friday November 12, 2004 @03:43PM (#10801805) Homepage Journal
    I heard recently about a new Nuclear Thermal design (in http://www.wired.com/ [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?
    • 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 stuf

      • Re:Nuclear rockets (Score:4, Insightful)

        by anactofgod ( 68756 ) on Friday November 12, 2004 @04:25PM (#10802179)
        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.
        • 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!!!
    • 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.
    • 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 pr
      • 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 extre
  • 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.

    • According to this [esa.int], 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.

    • 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 M

      • 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.

  • A fisking of TFA (Score:5, Informative)

    by Engineer-Poet ( 795260 ) on Friday November 12, 2004 @05:31PM (#10802861) Homepage Journal
    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. [timesonline.co.uk]
    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, [nasa.gov] 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!


    • 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
  • 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.
  • This [slashdot.org] is a recent article from earlier in the week about this mission.
  • 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.
    • 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
    • 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.

      • 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.
        • 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 exp

          • 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
            • 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 bal
              • 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 w
                • 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

                  • 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 co
                    • 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 -- d

                    • >>"...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 doe
                    • 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

                    • >>"...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 successor
  • Here's a picture [google.com] of the ion craft that went to the moon.

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