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