Re: question on orbits and boosting

From: Rainer Kresken (rkresken@t-online.de)
Date: Sun Nov 23 2008 - 18:19:54 UTC

  • Next message: Rainer Kresken: "Re: question on orbits and boosting"

    Darwin Teague wrote:
    
    > The lower the orbit, the faster a sat has to go to counteract gravity.
    
    yes.
    
    > Even at 220 miles up, there is enough atmosphere to gradually slow the 
    > ISS. Therefore it needs to boost itself into a higher orbit periodically.
    > 
    > Am I right so far?
    
    yes.
    And to say it explicitely: Atmospheric friction makes a satellite go
    *faster*. That's weird.
    
    > If so, why does slowing it down make it go down and not up?
    
    The point is that an orbit boost increases the orbital energy of a
    satellite. Orbital energy is the sum of potential energy and kinetic
    energy. If push a satellite int a higher orbit, you *increase* the
    potential and you decrease the kinteic energy. The sum of both parts is
    larger than before the manoeuvre.
    
    atmospheric friction does it the ither way round: It decreases potential
    and increases kinetic energy, and the sum is smaller than before.
    
    Hope that helps.
    
    Regards,
    
    Rainer
    
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