[amsat-bb] Re: New satellies / Shuttle question
ve9qrp at gmail.com
Sat May 31 19:04:01 PDT 2008
On Sat, May 31, 2008 at 5:40 AM, <G0MRF at aol.com> wrote:
> Hi Edward / group.
> Most current construction or feasility study is centered on P3E / Eagle /
> Intelsat /HEO where launch opportunities are rare and costs are high.
> Perhaps we should look at this problem from another viewpoint. Start with
> what launch opportunities AMSAT can afford and then retake the technology
> initative and investigate what minaturised payloads can we launch for that price?
> For example. Imagine a 2 or 3U cubesat type structure, or even one half the
> size of AO-51 on last weeks Russian launch to 1500km. With payloads reduced
> to transponders and a basic onboard computer and an Electrical Power System,
> it would be feasable to put RF comms equipment into a decent orbit on 29MHz
> 145MHz 435MHz with an RX on 1269.
> For bands higher than 13cm doppler is a problem and path loss is quite high.
> It may not be possible to provide the necessary DC power for transmitters
> in a small structure.
I asked the same question at the end of a thread decrying the lack of
HEO satellites, hoping to start a conversation on the topic. Let's
have one here. The best of this group is when we bat around ideas such
First, very soon we will have a great basis for future discussion in
Delfi C3. Already, though, it shows that a 3x cube can hold
transponder and deploy enough solar for a good transponder U/V
(judging by its fantastic downlink now). Could we replace the science
on board D C3 with a battery of chargeable cells and still stay within
the cubesat weight requirements? Or, even more radically, can we do
without batteries, given how we can live with AO-7 and D C3?
My guess is that deploying a 29MHz antenna could be hard with that
limited space. But it would represent a fascinating challenge.
Perhaps the hardest part would be finding a ride to high LEO without
propulsion. My sense is that Cubesats work economically because there
are lots of them. Won't university groups interested in remote sensing
see this as something worse than what they have with low LEO, for a
greater cost? Maybe we could get a bunch of projects interested in
high LEO together for one launch. Or, perhaps we could help one of the
national groups that still have access to their countries' launch
facilities, such as Japan or India or China. These might include a
p-pod or two in a high LEO launch as a charitable act: much cheaper
than a micro-sat.
> Talking of DC power, the number of cubesats that fail due to power problems
> is huge. The answer is to get inventive with deployable solar arrays. With
> the engineering excellence AMSAT possesses it should not be impossible to
> arrange a structure where the entire outer layer contains extra solar cells that
> are deployed after seperation from the launcher. Imagine a 3U cube which in
> orbit becomes a 3U box of electronics covered in cells, with an extended outer
> 3U shell that deploys forming a 6U structure producing nearly double the DC
> power. The 6U structure also makes antenna design easier
A neat idea. What about film solar panels that would be unfurled once
in orbit? I think these probably have such a lower efficiency that
they wouldn't be worth the extra area they might cover. In any case,
Delfi C3 gives a pretty great worst-case scenario.
> For a slightly more risky idea.....small satellite propulsion. Again,
> perhaps 3U cube, with the last section comprising a small motor. A single burn
> unit could provide a really nice elliptical LEO orbit, perhaps 680km to 2000km.
> Wouldn't that be interesting. I notice that there is an Austrian university
> team who have developed a cubesat sized ion propulsion system asking if
> anyone would like to try it. So, while this may initially seem a 'wild idea' it
> is based on technology that is very nearly a reality.
Regarding the ion propulsion, what if we were willing to wait a year
or two before use, so that all solar energy went into boosting the
orbit for that time?
And then there's the transponder. How efficient could a SDX be?
William, PE1RAH, is working on cubesat format UV transponders, I
> Worth investigating?
I really think we should look into S-band downlink, too. The stats on
s-band in HEO might be scary, but I think in LEO it would still be
high enough signal to be great fun. And we'd be colonizing an
> David G0MRF
> In a message dated 30/05/2008 23:22:37 GMT Standard Time, vk3jed at gmail.com
> At 12:15 AM 5/31/2008, Edward Cole wrote:
>>Once you total the costs it may actually be cheaper to build a new
>>satellite and launch it!
>>Back the effort for P3E and Eagle/P4.
> That too, yes, a new bird would be the easiest approach
> indeed. Still, as I said, it was interesting contemplating how such
> a recovery might be achieved with today's technology. :)
> 73 de VK3JED
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