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DIRECTV Satellite Discussion D-14 @99W

Discussion in 'DIRECTV General Discussion' started by Sixto, Jun 17, 2010.

  1. Sep 4, 2012 #581 of 3078
    P Smith

    P Smith Mr. FixAnything

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    Perhaps in distant future it will be solved by other way: design and build satellites as serviceable (to replace blocks/modules at its orbit or at lowered altitude) and create a fleet and a crew for such missions (at least at LEO - 500 km, Hubble proved the concept).
    Original idea above - robots for execute such tasks is too early, before man will get all the knowledge of fixing in a space, it would be baby game. :)
     
  2. Sep 4, 2012 #582 of 3078
    RAD

    RAD DIRECTV A-Team

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    It did retreive one satellite that was in LEO, http://www.sattel.com/life_of_palapa_b2.htm .
     
  3. Sep 4, 2012 #583 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    In theory, that's a fine concept. But Hubble (not "Habble") was only serviced a bare handful of times over its 22+ years in service, and almost certainly won't be serviced again (due to the retirement of the Shuttle). Each of those missions cost in the ballpark of half a billion dollars, and several of them had some kind of issue or glitch that a robotic servicing satellites wouldn't be able to handle: stuck fasteners, a service door that wouldn't close and latch correctly, etc. One mission even did almost depot-level repair of a component never intended to be replaced at all that had to be repaired using techniques and tools not considered when the spacecraft was designed.

    Adding in "on-orbit serviceability" is a major design requirement, one that pushes all sorts of things in many ways: components need to be larger and have handles or tether attach points. They have to have connectors and clamps between them and the spacecraft bus that are large enough that they can be manipulated by gloved astronaut hands or robotic grips and tools. They components have to have clearances around them on all sides so they can be removed and replaced. The areas inside the spacecraft where people or robots are doing work have to easily seen by eyes or cameras and have sufficient lighting without deep shadows so that the crew of tele-operators on the ground can tell what they're doing. Those areas also must be free of static and shock hazards, sharp edges (for crewed servicing), and with the service door open, they must be designed for exposure to blackbody darkness of deep space or the solar flux of direct sunlight, which will affect the thermal environment inside.

    All of those requirements mean the spacecraft itself is bigger, heavier and therefore costs more to launch. It's also functionally more complicated with more interfaces and points of failure, which makes it more expensive to design and validate, and can increase mission risks overall.

    So yeah, "far future" indeed, especially up in GSO or higher in a graveyard orbit. None of these ideas are trivial.
     
  4. Sep 4, 2012 #584 of 3078
    maartena

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    They did do some pick-ups in lower orbit though, as well as grab and repair existing satellites. Without the Space Shuttle, the mathematical error made in the design of the Hubble Space Telescope would not have been able to be fixed, and we would have never seen the amazing images it has been giving us for well over 10 years.

    I know the space shuttle has aged and needed to be retired.... but we have lost some capabilities we won't get back with the current development for new crewed space ships, which are focused on the IIS, landing on the moon/asteroid, and moving on to mars eventually.

    Robotic "satellite grab" missions could be done. It's the getting it back to earth without burning up that is tricky.
     
  5. Sep 4, 2012 #585 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    That's true. As far as it goes.

    But remember, the reason Hubble's main mirror was launched with that aberration in the first place is that the prime contractor and optics subcontractor nixed end-to-end testing of the optical path as a way to deal with the inevitable cost overruns experienced by space programs. Full-up testing would've revealed the flaw prior to launch. Part of those cost overruns was designing the thing to be serviced in the first place instead of simplifying the design and launching it fully-tested and accepting a shorter design lifetime. Hubble is/was a great achievement, no doubt. But some astronomers wish the design had been scaled back and two or three shorter-duration, improved models had been launched over the last 22 years instead of spending that same money on servicing missions.

    It's all a tradeoff.
     
  6. Sep 5, 2012 #586 of 3078
    evan_s

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    I have to agree with lefty here. Recovering or servicing sats isn't something I expect any time soon. The cost of launch things is just far too high for it to make sense and I don't see that changing any time soon. Human servicing has far too much overhead (need to provide food, oxygen, extra protection, etc.) and robotic is just far too complex. Sure, if everything was in perfect condition and went perfectly you might be able to service an old sat and keep it running but you'd still be limited by the old design and the reality is the sat has spent years in a harsh environment and isn't going to be in perfect condition and things will go wrong. Far safer and easier to launch a replacement sat and you get to benefit from the advances in technology. Most everything else now a days is disposable and there isn't any huge overhead with trying to repair a cell phone or TV.

    BTW the aberration in the mirror wasn't due to a mathematical error. It was a flaw in the manufacturing process due to stress and deadlines. The had made a previous, smaller mirror that was perfect. It starts on the bottom of page 2 and continues on to page 3.

    http://www.techworld.com.au/article..._telescope_what_managers_can_learn_from_it_/?
     
  7. Sep 5, 2012 #587 of 3078
    Groundhog45

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  8. Sep 5, 2012 #588 of 3078
    HarleyD

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    I anticipate that nothing of substance will be done in this area until the proliferation of space "junk" becomes untenable.

    And even then, I would not be surprised to see a deliberately destructive de-orbiting approach rather than recovery. Let them burn up on re-entry and be done with them.
     
  9. Sep 5, 2012 #589 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    For LEO satellites, that is the goal. However, for GSO vehicles, it would require a great deal of fuel to lower the perigee of the orbit enough to intersect with the atmosphere at a low-enough level to ensure vehicle breakup and burnup. Risk of debris hitting the ground or in shipping lanes must be minimized. Satellites tend to have some parts, especially tanks or pressure vessels, that are very resilient and can (and have in the past) survive reentry. So for GSO satellites, the FCC and international regulation require orbit raising to several hundred kilometers above GSO into "graveyard orbits" that are stable for several thousand years at least.
     
  10. Sep 5, 2012 #590 of 3078
    inkahauts

    inkahauts DIRECTV A-Team

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    So let people in a couple thousand years deal with it cause we won't be around! ;)

    Curios, how hard would it be to raise their orbit enough for it to slowly get bigger and bigger in its circling of the globe and then eventually head off toward somewhere else, like the sun or on to the next Galaxy or something... And I mean over the course of a hundred years or so (maybe even a thousand since we evidently have that long) something slow but just enough to make it happen...
     
  11. Sep 10, 2012 #591 of 3078
    Diana C

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    IIRC there was a Jerry Pournelle story about the aftermath of a major war, during which "killer satellites" were used to destroy the enemy's satellite communications network. The result was so much space junk that human beings were trapped on earth - nothing could survive a trip through the junkyard.

    We may get there without a war...this is what is in orbit now...
     

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  12. Sep 10, 2012 #592 of 3078
    HoTat2

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  13. Oct 10, 2012 #593 of 3078
    Ernie

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    That isn't going to happen. Orbits get higher when energy is imparted to the satellite. The moon's orbit increases about 4 cm/yr due to the effects of the moon caused tides slowing the earth. This complex interaction transfers energy from the earth's rotation to the moon. Unfortunately, a satellite nearly at geosynchronous orbit won't induce a tide on earth that will transfer energy to it.

    Ernie
     
  14. Oct 10, 2012 #594 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    Not to mention the fact that Moon is so massive that the epicenter of its orbit isn't even at the center of the Earth, which causes a small but measurable wobble in Earth's rotation; it's also far enough away that the sun has an effect on the Moon's orbit as well.

    Of course, if we're getting into second- and third-order effects, we might as well go off on solar radiation pressure on satellites too. :p
     
  15. Oct 10, 2012 #595 of 3078
    Laxguy

    Laxguy Honi Soit Qui Mal Y Pense.

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    I feel I should recognize your new avatar, Herb, but I canna'.
     
  16. Oct 10, 2012 #596 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    What, you don't recognize Lt. Templeton "Faceman" Peck? :grin:

    (Don't worry - I'm planning to change it again ... "soon" ;) )
     
  17. Oct 10, 2012 #597 of 3078
    Laxguy

    Laxguy Honi Soit Qui Mal Y Pense.

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    No, FOOL! I didn't....:lol: I'd have recognized Mr. T, but more due to his afterlife in commercials than from the show.
    Wouldn't have helped to have seen the attached, either. I missed the entire A-team for whatever reason.
     

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  18. Nov 4, 2012 #598 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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    Not particularly applicable to U.S. subscribers, but Directv on Thursday applies to the FCC for launch and operate authority for "Directv Ku-76W", a new Ku band satellite to expand broadcast capability to Mexico for Directv Latin America.
     
  19. Nov 4, 2012 #599 of 3078
    P Smith

    P Smith Mr. FixAnything

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  20. Nov 4, 2012 #600 of 3078
    LameLefty

    LameLefty I used to be a rocket scientist

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