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Space Science

Beware the Rings of Pluto 96

Hugh Pickens writes "The Christian Science Monitor reports that scientists are planning a new route for NASA's New Horizons space probe as it approaches a potentially perilous path toward Pluto through a possible set of rings that may create dangerous debris zones for the NASA spacecraft. New Horizons is currently about 1,000 days away and 730 million miles from closest approach to Pluto but given that New Horizons is currently zooming away from the sun at more than 33,500 mph, 'a collision with a single pebble, or even a millimeter-sized grain, could cripple or destroy New Horizons,' says project scientist Hal Weaver. 'We need to steer clear of any debris zones around Pluto.' Researchers are making plans to avoid these hazards if New Horizons needs to. 'We are now exploring nine other options, "bail-out trajectories,"' says principal investigator Alan Stern. New Horizon's current plan would take it about halfway between Pluto and the orbit of its largest moon, Charon. Four of the bail-out trajectories would still take the spacecraft between Pluto and Charon's orbit. The other alternatives would take New Horizons much further away from Pluto, past the orbits of its known moons. 'If you fly twice as far away, your camera does half as well; if it's 10 times as far, it does one-tenth as well,' says Stern. 'Still, half a loaf is better than no loaf. Sending New Horizons on a suicide mission does no one any good. We're very much of the mind to accomplish as much as we can, and not losing it all recklessly. Better to turn an A+ to an A- than get an F by overreaching.'"
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Beware the Rings of Pluto

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  • by mcgrew ( 92797 ) * on Wednesday October 17, 2012 @02:18PM (#41684859) Homepage Journal

    "(a) is in orbit around the Sun,
    (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
    (c) has cleared the neighbourhood around its orbit." [http://en.wikipedia.org/wiki/Planet#2006_definition]

    Pluto meets A,B and not C.

    Neither has Jupiter. [wikipedia.org]

  • by camperdave ( 969942 ) on Wednesday October 17, 2012 @02:37PM (#41685117) Journal
    The gravitational perturbations would, more than likely, cause the moon's moon to be unstable. Eventually, it (the moon's moon) would either crash into the planet or the moon, or be ejected from the system entirely. However, for the short term, it is entirely possible. Our Moon has quite a number of satellites orbitting it; all artificial, of course.
  • by pavon ( 30274 ) on Wednesday October 17, 2012 @02:40PM (#41685167)

    You don't really get much improvement in per-unit cost by building 10 of something vs 2. The biggest factor in the cost even with just the first couple isn't the engineering but the testing and qualification. Most of that has to be repeated for every unit you build until you are creating enough to have confidence in the past performance and to fall back to statistical testing, or at least are building enough for automating that work to be economical. But you would need to be creating several dozen of them for that to kick in. Furthermore, construction is more expensive that you are allowing for at those low quantities since it's all is done by hand, by highly skilled labor. That won't drop by much until you get into mass-manufacturing quantities, hundreds at least.

    So you would get minor savings, and at the loss of a huge amount of science. There is a reason that each of these probes is wildly different, and that is because the have wildly varying requirements. There is no one-size fits all suite of sensors. They will want different spectral ranges, different optics setups (detailed, narrow FOV vs wide coverage), different transmitter requirements (Horizon has much farther to transmit than MRO), all of which drives different battery requirements.

    Finally, the point of science is to keep learning; to keep pushing things forward. You do that by sending probes with improved and/or different capabilities, not just more of the same. Sure we could have sent 3 more MERs (Spirit/Opportunity) for the cost of Curiosity, but we wouldn't have learned as much as Curiosity will be able to tell us.

  • by c++0xFF ( 1758032 ) on Wednesday October 17, 2012 @03:48PM (#41686069)

    Trojans don't count in the same way that moons don't count. Basically, the definition of "cleared the neighborhood" means that anything left is dominated by the gravitational influence of the planet. Moons orbit the planet, Trojans orbit the Lagrange points.

    Another similar class of objects are those in orbital resonance with the planet. The Pluto/Neptune system, for example. Or Cruithne/Earth. The planet's gravity dominates in each case, so we're OK there.

    The term "cleared the neighborhood" is unfortunately misleading. And purposefully vague, I always thought. When does the neighborhood become cleared? There's a lot of asteroids in our near neighborhood (which result in rather significant accretion events, so to speak).

% APL is a natural extension of assembler language programming; ...and is best for educational purposes. -- A. Perlis