🚀 go-pugleaf

In article <1073@galaxy>, ruane@andromeda.rutgers.edu.rutgers.edu (Michael T Ruane Sr) writes:
> ...Part of the story is about a crew on a space
> station in HEO. The question(s) are:
> 
> 	3. The orbit wouldn't deteriorate appreciably in 200-300 years,
> 		would it ?
> 
   Of course in HEO your going to have trouble with *solar* radiation and Van Allen belts, but
   if you can build a booster big enough to get it to HEO ( > 1000 km ) it should be around for
   a century or two ( at least  ).

   I know it's not what you asked, but just for some background info...

   A space station in *LEO* with a mass of 100,000 kg, frontal area of 1,000 m^2 and Cd of 2.2
   would decay from 500 km ( 310 mi ) to 280 km ( 175 mi ) in around 1100 days.

   Once the station is down to 280 km it's orbit is decaying at 3km per day.

      The equation for the time between two circular orbits is given by :

         t = ( Hsc * ( 1/rho1 - 1/rho2 )) / ((Cd * A / m * go ) * ( go * Ro )^1.5)

      Where
    
         t   =  time between altitudes 1 and 2 ( seconds )
      
         rho1,rho2 = density of the atmosphere at 1 and 2, respectively ( kg/ft^3 )
 
         Cd  = draq coefficient

         A   = frontal area ( m^2 )
 
         go  = 9.807 m/s^2 

         Ro  = radius of earth = 6375400 m

         Hsc = ( h2 - h1 ) / ( ln(rho1) - ln(rho2 )) where h2, h1 are altitude of orbit in m
      
         This assumes that the density increases exponentially from h2 to h1. ( Which is valid
         ( sort of ) from 1000 km down to 400,000 ft or so ( sorry to mix units -- habit )
 
   I don't have any real feel for the density above 500 km, other that that above ~1000 km
   it's low enough that lifetimes should be in 100s of years.

   I would have sent mail, but I figure this is just as valid a contribution to the discussion
   as personal attacks on Canadians. 

   ...so I guess the answer to your question is *NO*

   As you can probably tell, I'd be happy to provide more info.

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                                               |      Ken Sheppardson
  "Ask a simple question -- get an equation."  |      U of M Aerospace Engin
                                               |      sheppard@caen.engin.umich.edu
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