Technical Update 10.12.2010
from the worklab on friday, 10th december, 2010
how temperature resistant is it? which temperatures can lithium metal batteries bear? are they frostsensitive? how hot may they get? temperature: at the start they might fall under zero, otherwise probably not. which temperatures will we have to face?
maybe we have to isolate the battery. what we have to be careful about there is that most isolation materials are based on gas inclusion, which is a problem in vacuum. maybe there is vacuum proof styrofoam.
all materials used must be suitable for the temperature range; multi-wire cable does not become brittle so easily.
the antenna is a dipol. when the satellite turns, the polarisation turns, too. if the observer is in the axis of the antenna (along the axis), s/he cannot receive anything.
we need 3 tests:
vibrator test - with some sort of "loudspeaker"/membran
temperature test - from -40 to +100 testing, 30times; what burns in vacuum? maybe testing with thermographic camera? localize hotspots with temperature sensors? sunlit sides can have totally different temperatures from non-sunlit sides, difference from -40 to -150?
vacuum test - for the material, degassing, no convection anymore (we need a vacuum chamber).
tracking the antenna
it will be necesary to track the antenna, following it automatically; due to the low orbit the time-of-sight will be relatively short. we will have to use each flyover, as the satellite wont be in orbit for so long. the challenge will be to build (or find?) a controllable autotracking device on 2 axes; it wont have to be too robust (only for a time span of 3 - 6 weeks).
we are planning to realize at least one test flight with a balloon, in order to test some things. the advantages: data transfer and transmission; we get the hardware back; we can test with the hard pressure of weitght restrictions; the autotracking for the antenna can be tested; this can easily be made into a public event; good effective event for general public; a good possibility for involvement and participation of interested people (receiving signal, tracing, following and recovert the satellite; additionally send a fm-transmitter along and each radio becomes a receiver.
receiver: scanner plus antenna plus cable: euro 200,-;extra costs for data storage and transmission.
sender: a lot of questions open; surely no manual tracing
gravity gradient boom
gravity gradient boom: serves as a alignment stablizer for the satellite, (where a small camera could be mounted to enable the satellite to take beautiful self portraits); how can it be deployed? automatically, with melting fuse, bimetall switch, muscle wire. the deployment has to be neutral to torsional moment (for example test it with a thin thread, or calculate it - henrik?)
maybe a stabiliation of position can be reached by magnetic torquers. for that we need a sensor on the satellite that tells us, how the satellite is positioned in relation to earth.
telemetric marker buoy
is a telemetric marker buoy sensefully doable? we can get data like the current stage of the battery, minimal info like when another satellite is passing, it can say "hello, world!".
no, of course it will send its callsign "mursat1".