Re: [amsat-bb] satellite propulsion thrust equations

[G0MRF@xxxxxxx]

Hi  Drew,  /  Achim / Graham / Florio
 
I suppose the modern form of scribbling ideas on the back of an envelope is  
sending them to a website for a wider audience.
 
Glad you liked it.  - Thank you for your comments.
 
Achim's .xls file is very interesting. Playing with the numbers produces  
some very interesting results. The required delta V for the example is quite  
high, 2000m/sec.  However, if you play with the mass and reduce the  
specification of the propulsion system I see it's still possible to raise an  orbit from 
something like AO-51 to a higer RS15 type orbit with a delta V of  just 
200m/sec. Amazing.  Still, I shall keep looking at 7500km (ish)
 
I will try and become more familiar with some of the terms, then go off and  
look at propulsion systems in more detail and their exhust velocities and try 
to  figure out the necessary vectors required to ensure the thrust pushes the  
satellite in the appropriate direction.
 
Something to do on the next rainy night in London. (not long to wait  then!)
 
Regards
 
David  G0MRF
 
www.g0mrf.freeserve.co.uk/MEOSAT.htm
 
 
 
 
David,

That is a very well written page, and an excellent idea. If  you take it just 
a small step further, there are launches to 22-23k circular  orbits coming up 
(soon?) in the Galileo program and maybe replacement GPS birds  too. Who 
knows if we could get out foot in the door on one of these, but it is  worth 
checking into...I'm not sure these are direct to this orbit, or if the  Galileo and 
GPS s/c include their own propulsion though.

73, Drew  KO4MA



In a message dated 12/10/2005 09:53:50 GMT Standard Time,  
avollhar@physik.unizh.ch writes:

Hi  David!
I read your idea and found it:

1. an interesting idea
2.  very well written
3. a challenge (the propulsion question).

So here  we are: go  to

http://gulp.physik.unizh.ch/meosat_propulsion.xls

and  download the excel sheet. I started from the following boundary  
conditions:

starting orbit circular (no GTO.. this complicates  things).. something a 
russian launcher can deliver (if the staging works  well :( )

Target orbit circular.. transfer orbit Hohmann type, so you  have two 
burns: one to change the low orbit into an elliptical with apogee  at the 
height of the high orbit and a second burn to circularize. This is  the 
theoretically most efficient transfer.

The input fields are in  blue (start height, target height, Isp, dry 
mass, fueled mass) and the  results (required delta_V, achievable 
delta_v) are in red. I filled in  some values from David's website 
including the Isp for the bi-propellant  enging and a 50/50 partitioning 
of fuel and dry mass for a 20 kg launch  mass. It is just possible..

Please play around and report errors.. I do  not take responsibility for 
any wrong mission planning :)

73s  Achim, DH2VA/HB9DUN

PS: to David, I certainly enjoyed the Surrey  colloquium.. see you next year!
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