KiteSat-1

Most people are not going to get the chance to launch a satellite into space, but everyone can launch a KiteSat. Of course you can’t strictly speaking add the ‘sat’ part because it will never be in orbit, but we’re mainly interested in the experience.

The idea was briefly presented at SpaceUp:UK 2014.  I think there was some confusion in the room – partly from my failure to describe the idea, and partly because it wouldn’t have much appeal to people involved with real satellites.  However, at the time Dr Chris Bridges did share that the main components of a satellite are:

  • Power: Solar panels, batteries etc.
  • Processing: Some form of computer
  • Communications: Typically radio
  • Optional sensors (but not very interesting without them)

All of these features are available in a modern Smartphone; which explains why some have already formed the basis of satellites – such as STRaND-1, and the NASA Ames PhoneSats.  However, for this first trial of KiteSat the communications part was not used.

 

Launch Options

Even if you’re not going into orbit, there are still the options of weather balloons or sounding rockets.  However, we’re going to go for something much simpler – the classic kite.  Kites have been used throughout history for aerial photography, meteorological equipment, and even to elevate human observers.  Also, if the string snaps it’s likely to fall back to Earth without travelling too far.

There is an almost infinite variety of kites, but one source suggested that the French Military Kite was a good design for lifting loads.  The chosen kite was of a similar design, but note that it isn’t anything special.  It’s just a budget, single-line recreational kite..

kite flying in the sky

Box kite with wings; but similar to a French military kite.

 

The Satellite

The chosen device was a Samsung Galaxy Ace that was no longer being used.  It’s a relatively light smartphone that runs Android.  The sim card was removed and the phone wiped just in case it blew away in the wind.  A case was made from layers of foam board so that it could be attached to the kite, and to add a bit of extra protection from rough landings.

Chosen phone (Samsung Galaxy Ace) and case made from foam board (note the opening for the camera)

Chosen phone (Samsung Galaxy Ace) and case made from foam board (note the opening for the camera)

 

The Software

We want our KiteSat to gather and save sensor readings.  Thankfully there are a large number of freely available apps that can do just that.  In this case AndroSensor was used.  It monitors all sensors and saves the data to a file on the phone.  It also has the option of emailing the data, which would have fulfilled the communication requirement of satellites, but since the phone was going to be recovered it was not necessary this time.

If I’ve learnt anything from space probes over the years, it’s that no matter how ground-breaking and revealing the sensor data is, it’s nice pictures that everyone wants to see.  An additional time-lapse app was installed (the free version of Lapse It) to take pictures every few seconds.

Only one app was active at a time, so separate flights were used.

 

Attaching KiteSat-1

A clothing button was threaded onto the main line, and KiteSat-1 was attached to that.  The mass of string near the button is a testament to how difficult it was to get a secure knot on the smooth string.  A fisherman’s clinch was used to attach the string to the kite, and that held well.

phone attached to the main line through use of a button

phone attached to the main line through use of a button

 

Launch Day

On launch day there was a light breeze, occasionally gusty.  Probably around 3-4 on the Beaufort scale.  It’s best to fly the kite on its own first to ensure that there’s enough wind.  On this occasion, apart from the odd time when the wind dropped completely, it flew well.

However, with the phone attached things didn’t go so well.  The attached weight caused the kite to tilt forwards and lose its lift.  Fortuitously the connection point on the kite snapped (at the top of the orange section), which required the string to be tied on to the frame further down (at the bottom of the orange section) – and this improved its flight.

KiteSat-1 in flight.

KiteSat-1 in flight.

 

Sensor Data

AndroSensor will save files on the phone that you can retrieve by attaching it to your computer with a data cable.  These appear as .csv files, and can be easily opened in Excel or Libre Office Calc.  You can also import the data into Google Drive; but be sure to choose a custom separator, and enter a semi-colon:

Setting the semi0colon separator in Google Drive

Setting the semi0colon separator in Google Drive

You can then create graphs from the data.  For example, the graph below shows data from the accelerometers in the phone.

Examine the graph and imagine that this is the sensor data that has come back from a satellite or space probe.  What information is it telling you?  It might help to know that when the phone is vertical and not moving the Y acceleration will be around 9.8, and both X and Z will be near zero.  This is measuring the acceleration due to gravity.

Graph of accelerometer data from KiteSat-1

Graph of accelerometer data from KiteSat-1

If you interpreted the data as showing that the flight was turbulent, then you’d be right.  The phone bounced around quite a bit.  However, the data also shows that it remained mostly vertical – since the Y value oscillates around the 10 line.  You might also have noted a calm period in the middle.  This is when the kite fell to the floor and was relaunched.

 

Images

The bumpy ride meant that the majority of images were distorted, but a couple came out OK.

Image from KiteSat-1 - colour corrected.

Image from KiteSat-1.  Colour corrected, and with some curvature distortion

Image from Kite-Sat1

Image from Kite-Sat1

 

Improvements

Definitely, some method of creating a more stable platform for the smartphone needs to be explored.  Possibly a larger kite is also needed so that lifting the phone is less of a struggle, and maybe waiting for a windier day.



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