Contents
Technical Update 10.12.2010
from the worklab on friday, 10th december, 2010
battery
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.
material
all materials used must be suitable for the temperature range; multi-wire cable does not become brittle so easily.
antenna
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.
necesary tests
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).
balloon
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.
groundstation
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:
dient zur stabilsierung der ausrichtung (und da könnte dann auch eine kleine kamera dranhängen für ein wunderschönes selbstportrait); wie soll er ausgefahren werden? automatisch, mit schmelzsicherung, bimetallschalter, muscle wire. das ausklappen muss drehmomentneutral sein (zb auf einem dünnen faden testen, oder ausrechnen - henrik?).
vielleicht lässt sich eine lagestabilisierung über magnettorquer erreichen. dafür müssen wir einen sensor anbringen, der uns sagt, wie der satellit zum magnetfeld der erde steht.
telemetriebake
wäre eine telemetriebake sinvoll machbar? dadurch kriegen wir den aktuellen zustand. zb. batteriestand, minimale info zb. wenn ein anderer satellit drüberfliegt, schickt er sein rufzeichen - "mursat1".