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RE: Re: Useless CubeSats



IMHO cubesats have the big challenge of making a <1000g satellite the cheap
and easiest way possible, and most of the times this is quite difficult,
although in any satellite design u're allways counting the grams :)
I mean, there is still the need of having batteries, solar cells,
communications devices, gyros and attitude control, On board Computer -  all
the basic stuff  - and a really tight mass budget as an "enemy".

Problems as high power doesnt exist, true, but the "miniaturization" is an
headache!

73 de Luis Rolo,
CT2INY

-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On Behalf
Of William Leijenaar
Sent: terÁa-feira, 8 de Fevereiro de 2005 6:59
To: amsat-bb@amsat.org
Subject: Re: [amsat-bb] Re: Useless CubeSats

Hi AMSATs,

I like to give some comment on your reply:

>Now, come on...the big sat and the little sat have all the same things - 
>solar
>cells, batteries, control circuits, comm circuits, mission specific 
>circuits,
>attitude parts...and they work the same. Bill, the ICs are just the same, 
>the
>solar cells too. Same Teflon wire, Kapton tape, potting compound, machined
>aluminum...just less of it. And less is cheaper, easier to manage, test and
>design for some who have never done so.

Maybe I didn't explain to well why a CUBESAT can not be compaired with a 
real satellite.
Yes, they are both made of the same materials, but that doesn't mean they 
have the same problems. A cubesat has no high powers, not that much high 
temperature problems, no difficult propulsion systems. They have mostly 
simple tranceivers, only omni-antenna's etc etc...

With a bigger satellite you have real physical problems to solve, that can 
not only be fixed with a program. There you even have to think where to 
place components to get ride of the heat (e.g PA) or find ways to shield 
sensitive parts (like uProcessors), think out how to place antennas in a way

they "light" the earth without interfering other radios on board.
Then you need to deal with high current/voltages that must be converted in 
other voltage levels, in an efficient way (not with simple regulators).
When the satellite is spin-stabalized, all the payloads have to be weight 
balanced.
>
> > Its like giving a truck-mechanic-student a small truck model to learn 
>how to
> > repair a truck engine.

>A good analogy - but to make it complete - the truck model runs, just like 
>a big
>truck. It doesn't haul as much, but it runs.

When you think that an electrical motor work equal to a diesel motor...
They are both made of metal, but never work the same...
>From the outside they look-a-like the same, like a CUBESAT is also a 
satellite, but they have totally different physical way of working 
principles.

> > A better use for the CUBEs would be on a high-altitude balloon.
> > The boxes are small and light, and ideal for such missions.
> > These missions are less expensive and are 100x more educative because 
>after
> > the box returns down, the student can inspect what has happened to the
> > electronics.
> > You can only learn when you know what you have done wrong, and when you 
>can
> > change it and try again.
>
>For simple satellites, that would be the case. But, there are many CubeSats

>that
>have serious experiments on board - not just a CW ider. They need the space
>enviroment for the work. And as for the issue of RF congestion, consider 
>this -
>these little cubes will decay within a couple years or so and be out of 
>your
>hair - far sooner than other satellites.

I mentioned before that CUBESATs can be usefull for some small scientific 
measurements. What I disagree is that they can be used to learn students how

to build a satellite. In a matter of words they are making a satellite, but 
then you can also buy an FT847 put it into repeater mode and launch it into 
space.

>Shrink your analog transponder and offer it.

I am already working on that, but time is my enemy :o)

>
>--
>Dave Goncalves
>W1EUJ

73 de PE1RAH,
William
---

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