[amsat-bb] Re: AMSAT HEO design evolution (longish)

[Bruce Robertson]

All the reasoning below is quite progressive. Thanks, everyone. If I
can piggy-back on Trevor's suggestions, I suspect a cubesat-based
collaboration with a university group that wants to try out a new
propulsion scheme would be idea. We would offer our expertise in
communications and antenna design and, more importantly, our
telemetry-collecting strength-in-numbers. They would build the
propulsion system, either ion-based, or sail, or whatever.

Consider that, for us, many kinds of failures of these sorts of
propulsion systems would not be catastrophic: we'd just have another
LEO at 700km to play with. Moreover, if the satellite took 2 years to
reach its target altitude, I think we'd all find it great fun to watch
and track that. Perhaps if it were a propulsion system like ion, that
requires the use of the solar panels, we could periodically switch the
propulsion off and try out the transponder to 'wet our whistles'.

Finally, this sort of scheme would be very nicely suited for S-band
work, since the doppler shift would not be as painful with the higher
altitude. With the lower altitude, but lower power, perhaps the 60cm
dish could be used, thereby allowing a more easily camouflaged antenna
set-up for US hams in restricted circumstances. (The uplink antenna is
something of a problem, but perhaps 50w on 70cm into a attic-mounted
beam would still do well.)

Nobody's mentioned attitude control yet. I assume that with a
propulsion system attitude will have to be finely controlled. Is this
a problem?

73, Bruce
VE9QRP

On Mon, Aug 11, 2008 at 6:55 PM, Trevor <m5aka at yahoo.co.uk> wrote:
> A MEO orbit at 4500 km would be good compromise between range, path loss, radiation, time delay and doppler shift but the problem is geting there or to higher MEOs. Inevitably you'd end up with a propulsion system on your sat to get from a 'cheap' 700 km orbit. But once you've got such a system the additional costs to get it into an HEO orbit are negligable.
>
> However, as the web page http://www.g0mrf.freeserve.co.uk/MEOSAT.htm shows there are other propulsion systems that are feasable assuming you're prepared to wait longer to achieve the final orbit.
>
> One of the great things about Cubesats is that they allow you to try experiments such as alternate means of achieving orbital changes at 'little' cost.
>
> 73 Trevor M5AKA
>
> --- On Mon, 11/8/08, Graham Shirville <g.shirville at btinternet.com> wrote:
>> From: Graham Shirville <g.shirville at btinternet.com>
>> Subject: Re: [amsat-bb] Re: AMSAT HEO design evolution   (longish)
>> To: "SV1BSX" <sv1bsx at yahoo.gr>, G0MRF at aol.com, m5aka at yahoo.co.uk, amsat-bb at amsat.org
>> Date: Monday, 11 August, 2008, 10:29 PM
>> > if we can not launch a HEO, why not  about a MEO?  I
>> remember a nice page
>> > around Internet (unfortunately I can't find this
>> page any longer)
>>
>>
>> Try one of David's own pages:
>>
>> http://www.g0mrf.freeserve.co.uk/MEOSAT.htm
>>
>> Really interesting and thought provoking reading!
>>
>> 73
>>
>> Graham
>> G3VZV
>
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