Tuesday 29 October 2013

Droidcon 2013: Phones in Space

Chris Bridges, Surrey Space Centre, @DrChrisBridges

STRaND-1 Nanosatellite

space is old tech!

  • catch-22 with electronics in space: if it hasn’t flown, we can’t fly it
  • most electronics in space are 10-20 years old
  • they are larger: 90nm features
  • 30nm of modern fabs may have trouble in space — we think they will be knocked out by single event effects
  • largest particle coming out of the sun is an ion proton at just under 90nm
  • but foundries that make 90nm chips are soon going to be decomissioned
  • so need to start testing effects on smaller chips soon!
  • also, newer components, especially mobile are smaller and much more powerful
  • if we’re worried about reliability, could duct tape three phones together and get more power than the entire ISS
  • also useful for medical purposes — investigate how tech behaves in radiation situations

hardening phones

  • components also get shaken to 30-40G when rocket goes up
  • used 3D printed brackets (chins) to hold pieces together
  • control satellite attitude with magnetic coils
  • had to harden the phone & connections
    • extract out the button connections & stick the trackball in place
    • need to remove any electrolytic components — they pop in space
    • also some plastics degrade in space
  • controlled from Digi-Wi9C: low power linux single board computer
  • put programs into solid state flash memory (PIC-24) that is not affected by space radiation
  • also needed to check out timings: satellite works at about 8-40MHz; Digi-Wi9C at 150MHz
  • android apps had to be instrumented so that they could be monitored and controlled: added heartbeat monitors to check if apps were still alive
  • wanted to have a software lab in space
  • had to check how the hardware behaved without convection
    • saw that battery voltage reporting flipped a sign when temperature went below zero
  • destroyed about 12 phones in radiation… cobalt-60 ionising radiation
  • tested satellite for equivalent of 6 years of radiation
  • have a camera that looks at the screen
    • useful if usb connection fails
    • can connect over wi-fi
    • or else fall back to taking a picture of the screen

your apps in space

  • had an app competition for software on facebook
  • can you scream in space?
    • does the vibration from the speaker reach the microphone?
    • don’t know yet…
  • antenna communicates at 9Kb/s back to Earth
  • went up into low earth orbit in 25th February
  • SSC groundstation
  • amateur satellite trackers around the world really important and integrated — 10 people around the world
    • gmail > gdocs > SQL databases > plotting
    • can get a groundstation in a single USB stick
    • just need a bit of wire for the antenna
  • when it’s first released, the satellite tumbles uncontrolled — need to use coils to place it in controlled orbit
  • strand-1 status on web site
  • testing charging the phone — have done it 9 times now
  • will soon be testing apps…
  • code available on s-android on google code
  • satellites normally take years to build: STRaND-1 built in 3-4 months in lunch breaks and evenings
  • NASA taking it forward
  • UniS doing STRaND-2
    • want to have two satellites docking & undocking in space

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