Re: [amsat-bb] satellite propulsion thrust equations

[G0MRF@xxxxxxx]

Hi Bob.
 
Thanks for the pointer to the NASA site and the description of Hohmann  
transfer orbits. _ Particually the direction of thrust and the effect on where  
apogee will occur. I have cut and pasted the Nasa graphic onto the MEOSAT page,  
with due credit of course.
 
I take your point about the amount of fuel required but the ball park  figure 
appears to be much less than a phase 3 bird.  The main  difference seems to 
be that while electronics (and solar cell efficiency) has  progressed hugely in 
the last 30 years, allowing minaturisation and 10 fold mass  saving, those 
pesky Newtons laws haven't given us an improvement in 300  years.
Fortunately, with 'cubesat x 3' type structures, the fuel  requirement looks 
modest.
 
Incidentally, I notice that the SSETI projects use of Nitrogen is providing  
130m Newton attitude thrusters on Express but the next in the series, ESEO, is 
 using 20 bar of pressure to achieve 10 Newtons of thrust for major changes 
in  orbit.
 
Good luck with Eagle
 
Regards
 
David  G0MRF
 
 
 
 
In a message dated 12/10/2005 14:32:02 GMT Standard Time,  
rwmcgwier@comcast.net writes:

While  not at its peak intensity, the radiation environment would be 
intense and  I think your bird would spend more time in this area than a 
Phase 3  HEO.  We would have to do some detailed calculations but my 
intuition  tells me the total dosage would be higher in your bird.    
Secondly,  the complexity in these satellites is not strictly the  height 
of the orbit BUT the need to carry a propulsion at all.  Once  you have 
crossed that threshold,  you might as well  optimize it  for 
communications.  You have also discovered what a huge boost (pun  
intended) we are given in delta-V by getting off at GTO rather than at  
LEO altitudes. To get to your altitude the satellite would have to carry  
more fuel than a Phase 3 bird.
----
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