From: isaackuo@jell-o.berkeley.edu (Isaac Kuo)
Subject: Re: Drag-free satellites
Organization: U.C. Berkeley Math. Department.
Lines: 37
NNTP-Posting-Host: jell-o.berkeley.edu

In article <15821.2be3e125@cpva.saic.com> thomsonal@cpva.saic.com writes:
>On Sat, 1 May 1993 23:13:39 GMT, henry@zoo.toronto.edu (Henry Spencer) said:
>
>> No.  A "dragless" satellite does not magically have no drag; it burns fuel
>> constantly to fight drag, maintaining the exact orbit it would have *if*
>> there was no drag.  
>
>     Well, almost. It turns out that clever orbital mechanics can 
>engineer things so that resonant interactions with the higher order 
>harmonics of the Earth's gravitational field can pump energy into a 
>satellite, and keep it from experiencing drag effects for periods of 
>months to years. 

A harmonic of the Earth's gravitational field?  What IS a harmonic of the
Earth's gravitational field?

>     My favorite example of this is the Soviet/Russian heavy ELINT 
>satellites of the Cosmos 1603 class, which are in 14:1 resonance. In 

14:1 resonance with WHAT?  It's not like there's any wavelength or frequency
to the Earth's gravitational field.  Now, there' might be some interesting
interactions with the Moon's tidal effect--is that what you're talking about?
>
>    This probably has little relevance to space stations, since the 71 
>degree orbits of the C1603 satellites are at 850 km, which is 
>unacceptably far into the inner van Allen belt for manned platforms. But 
>it's kind of interesting from the point of view of the physics of the 
>situation. 

What are the physics of the situation?  The only way I can see gravitational
effects being useful in adding energy to an object orbiting Earth is some
sort of interaction with the moon.
-- 
*Isaac Kuo (isaackuo@math.berkeley.edu)	*       ___
*					* _____/_o_\_____
*	Twinkle, twinkle, little .sig,	*(==(/_______\)==)
*	Keep it less than 5 lines big.	* \==\/     \/==/
