Kickstarter MSP430 in Space - Page 1
Forum section: electronics / general

author: kaz911
author_rank: Super Contributor
timestamp: July 12, 2013, 06:56:52 am
content: Hmm - this seems to be a tinker special :-)http://www.kickstarter.com/projects/1677943140/send-your-own-pocket-spacecraft-on-a-mission-to-th?ref=categoryGet your own "micro" space craft/sensor - with MSP430 and solar powered - and with the possibilities of doing your own MSP430 software - and even versions where you can add (Att: Chris - printable) passive circuits on the thin film main board.They fill up a "Pringle" can with lot of the thin film modules - and ship them to high orbit - or later to space - and release them.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: July 12, 2013, 10:13:51 am
content: I don't get it?*) Satellites, even CubeSats, need to be above a certain volume, to ensure the electronics stays at a reasonably constant temperature. The temperature of a thin FlimsySat would very quickly plummet to that of liquid Nitrogen when in the shade of the Earth or the Moon, and toast at around 150 degrees C when exposed to the Sun. What COTS components do they expect will survive this temperature cycle?*) Space junk is a serious concern with the relevant authorities due to the potential problem of theKessler syndrome. CubeSats are intentionally launched (kicked off by a spring) at fairly low altitudes. This way their orbit will naturally degrade fairly quickly, after which they re-enters the atmosphere and burns up. The Moon has no atmosphere, so an object, which doesn't hit the surface on the first orbit, will effectively stay in orbit forever. I cannot see this group getting permission to launch thosands on FlimsySats in low Moon orbit. That would be insane.*) S-band is about 3 GHz, while X is around 10 GHz. A parabolic dish reflector needs to have a surface, where deviations are within a quarter wavelength, for it to have a gain close to the theoretical value, given by its diameter. At 3 GHz a quarter wavelength is about 2.5 cm. Building a fully steerable dish for 3 GHz of 5 meter in diameter is hard to do in your back yard. Sure, amateurs do sometimes have dishes of that size, but they are usually only used up to 1.3 GHz for this very reason, if even that. At higher frequencies hams tend to use smaller, off the shelf units.*) A fully steerable, commercial dish of 5+ m diameter, useable at 3 GHz or above, is very expensive. Very few will be in the hands of individuals, and the commercial/science antennas are all booked solid with 'paying' work, just to keep up with the growing needs of just the regular, scientific community.*) These people will no get access to facilities like the DSN for something like this, that is just plain delusional. The DSN cannot even keep up with the work NASA throws at it.*) Cameras are of very little use, unless your spacecraft at the very least has spin stabilization. A FlimsySat would just be randomly tumbling through space.*) Same issue with solar cells and the communication link to Earth, unless you have batteries (or super capacitors) on board. Without either the FlimsySat would reset every time an edge is pointing in the general direction of the Sun. Which will be very frequently for a small, disc shaped object in hard vacuum, not equipped with any guidance systems.*) A solar sail requires very accurate guidance plus a stable orientation of the spacecraft in order to do anything at all. Tumbling spacecraft plus solar sail equals fail. Might work for the CubeSat carrier trip to the Moon, but steering the individual FlimsySats would be impossible after launch from the carrier.*) The free space path loss between the Moon and the Earth is more than 200 dB at 3 GHz. What kind of receivers do they expect people to have, if the TX power from a FlimsySat is, say, 10 mW (+10dBm)? What kind of downlink bandwidth is shared by the 50 people on a single FlimsySat?*) Nobody outside the commercial/education/military sector will get permission to operate the thousands of Earth bound S- and X-bandtransmittersrequired to establish an uplink, assuming people were willing to pay for those in the first place.Could probably go on for a while, but think I'd better stop here...

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: July 12, 2013, 11:15:13 am
content: Just did a quick calculation on the Moon/Earth downlink power budget. If my math isn't completely off, then the SNR will be-5 dB in a 50 Hz bandwidthat 3 GHz. This assumes zero antenna gain on the spacecraft, 5 m diameter receiver antenna with 50% efficiency, +10 dBm transmit power, non-cryo cooled rx preamp and 1 dB receiver noise figure.So basically you can detect the signal is there when using a FFT waterfall display on a PC. Alternatively you can transmit downlink dataveryslowly while using the same technique combined with various forms of error correction.50 people sharing the same downlink?

author: Psi
author_rank: Super Contributor
timestamp: July 12, 2013, 11:33:53 am
content: I'd love to put a cubesat up there that transmits some copyright movies/tv.Just because it would be funny to see the MPAA scratching their heads at how to shut it down.

author: andersm
author_rank: Super Contributor
timestamp: July 12, 2013, 01:00:52 pm
content: They don't need to shut it down when they can just fine you for each transmission*the potential number of viewers (ie. the whole world).

author: ve7xen
author_rank: Super Contributor
timestamp: July 13, 2013, 05:52:00 am
content: Quote from: ElectroIrradiator on July 12, 2013, 11:15:13 amTheir KickStarter claims the 'FlimsySats' (nice name) will have ~1bps TX bandwidth and will relay via the CubeSat when in lunar orbit, which they claim will deliver 1200bps shared by all FlimsySats (and for mission telemetery). They suggest "you should probably assume your Earth Scout will average one bit per second and your Lunar Scout one bit per hour." I was looking for more detail on the modulation etc. but there doesn't seem to be any on the site. I'm not sure if there's access control or how they are moderating access to the channel. Anyway, 1 bit per hour spread across a few hundred of these things doesn't seem completley out to lunch to me, but theywillneed a pretty substantial ground station.The FilmySats are apparently on the UHF amateur band (~440MHz), the CubeSat downlink is on S-band. It's not clear to me if they plan on an uplink at all.It's an interesting and unconventional idea, and there are clearly a lot of challenges, but they do appear to be thinking through at least some of them, and again appear to have some engineering talent on the team. Chances are they will fail to get the support needed to even attempt the project, but I think the 'serious' agencies do see some merit in investing a little bit in crazy shit now and then, and the investment on their part would be very little to support a CubeSat launch. It reminds me a bit of early CubeSats or the NASA PhoneSats. Crazy ideas with small-scale spacecraft that defy the conventional engineering norms, but maybe if they work will push the cost of simple experiments way down.Not convinced enough to pledge any money, but I'd like to see it succeed.