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NASA Space

Cassini's Elaborate Orbital Mechanics 116

jamie found an article at the NY Times about the extreme orbital mechanics gyrations required to extend the Cassini mission at Saturn by seven more years. Here's a graphic of the mission extension, which NASA took two years to arrive at. "The plans are for Cassini to keep working for seven more years, but it currently has only 22 percent of the maneuvering propellant it had when it started. Figuring out how to more than double the duration of the mission with less than a quarter of the fuel is hard. Cassini's orbital mechanics present an astonishingly complex exercise in Keplerian physics and geometry. The enormous array of science objectives and targets — moons, rings, Saturn itself — makes it one of the most complex missions ever flown. ... 'Without Titan,' Mr. Seal [Cassini's mission planning supervisor] said, 'we would go into one orbit around Saturn and be stuck there.' Thus Titan, in the argot of orbital mechanics, is Cassini's 'tour engine.' [T]he final 'reference trajectory' ... now includes 56 passes over Titan, 155 orbits of Saturn in different inclinations, 12 flybys of Enceladus, 5 flybys of other large moons — and final destruction."
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Cassini's Elaborate Orbital Mechanics

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  • Sounds like... (Score:1, Insightful)

    by Anonymous Coward on Tuesday April 20, 2010 @02:20PM (#31913608)

    they used genetic algorithms to solves this? Or something alike

  • by Anonymous Coward on Tuesday April 20, 2010 @02:28PM (#31913708)

    And yet your comment is the usual back-biting. Ah well.

  • Re:I call bullshit (Score:1, Insightful)

    by Anonymous Coward on Tuesday April 20, 2010 @02:40PM (#31913856)

    You plan for what you know your resources will do for sure. If there is anything left you make a plan to use what's left. Repeat until you can't any more.

  • Re:I call bullshit (Score:1, Insightful)

    by Anonymous Coward on Tuesday April 20, 2010 @02:45PM (#31913924)

    That's because, unlike most, they DO expect the Spanish Inquisition. The only extend the mission if the inquisition never gets off the ground.

  • Re:I call bullshit (Score:5, Insightful)

    by Nadaka ( 224565 ) on Tuesday April 20, 2010 @02:49PM (#31913952)

    Because everything costs so much to launch that they design something to absolutely be capable of fulfilling its mission parameters. If they screw it up, it crashes and dies with billions lost. If they get it right, they might have some triplicate backup resources used to ensure function for 90 days that are left over. And because it would cost billions to get those resources up with a new mission, they might as well take advantage of what is left.

  • Re:I call bullshit (Score:5, Insightful)

    by BJ_Covert_Action ( 1499847 ) on Tuesday April 20, 2010 @04:05PM (#31914820) Homepage Journal

    and makes the bigger-brained among us yawn at the idea that anyone is impressed with 64 loops around a couple of rocks that aren't going anywhere fast...

    That's a bit of an arrogant statement. While you hit the nail right on the head with the margins in spacecraft design, I have to say that seeing the orbital plots of a mission as complex as Cassini, is, in no way, a yawning experience. While you may think that it's nothing more than a few geometric loops around some rocks that aren't going anywhere, those of us who have worked on orbital mechanics problems understand, in no small part, just how complex the math must have been to work out those solutions. Furthermore, we have a fascination with the idea of getting to fiddle with problems like that ourselves one day. In fact, this particular plot has inspired me to pull out my 3-body problem source code when I get home and revisit some of the algorithms used to optimize fuel consumption for 3 body orbital problems.

    What I am getting at is that those 64 loops around a couple of rocks, which you so trivialize, represent, to those of us involved in this field, a visual depiction of a very high level of hard, computer intensive work that we are familiar with. It's kind of like hearing a symphony play a composer's final musical construct. Those who are composers can appreciate the symphony as it depicts, audibly, just how intensive, deep, and subtle the composer must have been in his work. Likewise, those of us that are familiar with these types of problems can look at the visualization and appreciate the incredible mathematical nuance and finagling that must have gone into doing these calculations.

    Then again, very few people tend to have any appreciation for the engineering intensive processes that go into even common, everyday appliances like computers and cars, so I suppose I shouldn't be surprised when a self-proclaimed 'bigger-brained' person cannot appreciate the depth and culmination of work that a plot like the one linked to in the summary represents.

Beware of Programmers who carry screwdrivers. -- Leonard Brandwein