sheppard@caen.engin.umich.edu (Kenneth Charles Sheppardson) (12/01/88)
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. ----------------------------------------------------------------------------------------------- | Ken Sheppardson "Ask a simple question -- get an equation." | U of M Aerospace Engin | sheppard@caen.engin.umich.edu -----------------------------------------------------------------------------------------------
sheppard@caen.engin.umich.edu (Kenneth Charles Sheppardson) (12/01/88)
... of course if the nuclear war is severe enough, you could probably blow away the
atmosphere and not even worry about orbit decay...
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Ken Sheppardson
U of M Aerospace Engin
sheppard@caen.engin.umich.edu
-----------------------------------------------------------------------------------------smryan@garth.UUCP (Steven Ryan) (12/06/88)
>I am new to this newsgroup, but I find many of the discussions >interesting. >Could someone be kind enough to post the definitions of HEO and >LEO? Good luck getting any help from the experts. They are far too busy to respond to mere amateurs as you or I. As far as I can glean, HEO = High Earth Orbit LEO = Low Earth Orbit -- +---------------------------------------+--------------------------------------+ | Multi-culturalism -- just an excuse | When are we going to see | | to keep the minorities satisfied. | Anglo-saxon cultural events. | +---------------------------------------+--------------------------------------+
sheppard@caen.engin.umich.edu (Kenneth Charles Sheppardson) (12/07/88)
------------------------------------------------------------------------- In article <2121@garth.UUCP>, smryan@garth.UUCP (Steven Ryan) writes: >>Could someone be kind enough to post the definitions of HEO and >>LEO? > > Good luck getting any help from the experts. They are far too busy to > respond to mere amateurs as you or I. We'll I hadn't really considered myself an "expert", but ... > As far as I can glean, > > HEO = High Earth Orbit > > LEO = Low Earth Orbit LEO <=> 100-500 nautical miles ( 200-1000 km ) HEO <=> >500 nautical miles ( >1000 km ) ------------------------------------------------------------------------ Ken Sheppardson sheppard@caen.engin.umich.edu
maniac@garnet.berkeley.edu (George W. Herbert) (12/08/88)
In article <401907a2.5e37@dl5e37.engin.umich.edu> sheppard@caen.engin.umich.edu (Kenneth Charles Sheppardson) writes: > >LEO <=> 100-500 nautical miles ( 200-1000 km ) > >HEO <=> >500 nautical miles ( >1000 km ) pardon, but since when is 500 miles=1000 km? even nautical miles... really, 500 nm=925 km (close, but no cigar?...) -george william herbert
sheppard@caen.engin.umich.edu (Kenneth Charles Sheppardson) (12/08/88)
--------------------------------------------------------------------------------------------- In article <17976@agate.BERKELEY.EDU>, maniac@garnet.berkeley.edu (George W. Herbert) writes: > In article <401907a2.5e37@dl5e37.engin.umich.edu> I wrote: > >>LEO <=> 100-500 nautical miles ( 200-1000 km ) >>HEO <=> >500 nautical miles ( >1000 km ) > > pardon, but since when is 500 miles=1000 km? > even nautical miles... > really, 500 nm=925 km > (close, but no cigar?...) > -george william herbert Actually, if I wanted to be picky I'd point out that: 1 nm = 1852 m => 500 nm = 926 km ^ ...but then since my original statement was intended only as a general guideline/rule of thumb, and since the limits aren't that clearly defined, I see no reason for me to be picky. --------------------------------------------------------------------------------------------- Ken Sheppardson sheppard@caen.engin.umich.edu