Re: FW: Shuttle water dump while attached to ISS

From: Vitek, Antonin (
Date: Mon Aug 20 2001 - 15:18:35 PDT

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    Bjoern Gimle wrote:
    > If RCS is indicative of true cross-sectional area, drag force increases with
    > RCS.
    > But the EFFECT of the force decreases with more mass of the affected object.
    Exactly speaking (in equations):
    spacecraft decelaration is given as
    a = (1/2).cx.(A/m).rho(h).v.v
    where cx - aerodynamic coefficient (depending on shape of object)
    A - effective cross-sectional area of spacecraft
    m - mass of spacecraft 
    rho(h) - atmospheric density at given height h
    v.v - velocity (squared)
    For a circular orbit with major semiaxis a, the change (decay) of 
    semiaxis per orbit is given as
    delta a =
    Consequences: for spacecraft of silimilar shape the decay is
    proportional to the A and inversely proportional to the m (PI is Ludolph
    number, 3.14159265....)
    Mgr. Antonin Vitek, CSc.
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