Welcome to the Mile Pi Club

The HAB team is getting together with a group from the Computing Society to work on a joint ballooning project! As you may have guessed from the name, the payload on the first launch will be the always-popular Raspberry Pi. On its first flight, it’ll be connected to:

  • A GPS module. You’ve got to be careful when choosing these: consumer-grade GPS modules are designed to stop working if they think they’re on an intercontinental ballistic missile, and have different ways of deciding whether they are. Pick the wrong one, and it’ll panic and shut down simply by going too high.
  • A GSM module, which will attempt to text us the landing coordinates once the payload has descended close enough to the ground to pick up a mobile phone signal. Of course, the balloon will spend most of its flight too high above the ground to pick up the network, and the payload might land in a remote area with no signal, which is why it’ll also have…
  • A radio transmitter, to send us GPS coordinates and photos while the balloon is flying.
  • Speaking of photos, there’s a camera module to record video of the flight, which will also occasionally send pictures back to us on the ground.

Becky’s currently working on a cosmic ray detector that might also fly on this balloon, so we might be doing some actual science as well as taking pretty pictures! (On the other hand, it might be more sensible to fly the cosmic ray detector on the second flight, once we’ve had some practice and are less likely to lose the payload…)

Stay tuned for updates on this blog about what the joint ballooning team is up to! If you’re really keen and want to follow the project’s progress in minute detail, the code is all on Github.

New Sponsor: National Instruments

We’re happy to say that National Instruments is joining our growing list of sponsors and supporters. Welcome to the team!

National Instruments

National Instruments is the industry leader in automated test equipment and virtual instrumentation software. They make software and hardware tools used by scientists and engineers all over the world to acquire and process experimental data and to automate industrial processes.

This year they’re kindly giving* us an exciting gadget called a myRIO. It’s essentially a small embedded computer running a flavour of real-time Linux, with a host of exciting features like:

  • A dual-core ARM Cortex-A9 processor at 667MHz, which gives us a decent amount of processing power.
  • A Xilinix Z-7010 FPGA – this chip can be reconfigured to carry out a complicated operation of your choice in a single clock tick. Using an FPGA would usually involve learning esoteric languages like VHDL, but the myRIO’s FPGA can instead be programmed using NI’s graphical programming tool LabVIEW.
  • A total of 48 digital I/O lines and a total of 10 analog input lines – the latter can sampled at up to 500 kilosamples/second. While the 12-bit ADC doesn’t quite have the resolution of the ADCs found on dedicated DAQ boards, it won’t be a limiting factor in what we’re using it for this year.
  • Wi-Fi connectivity: the option of one fewer cable to trip over!
  • A button.
NI myRIO

Shiny new myRIO, plugged in and ready to do some serious rocket science.

It’s a very powerful (but heavy – it’d be half the vehicle’s mass!) option for Hummingbird’s flight computer. Since it can handle both control and data acquisition, it’ll also be useful for test-firing the torch igniter: the test team can set everything up, leave the lab, and command it from a safe distance to begin a test-fire and save data to internal memory, all while relaying important information to us.

We’re looking forward to seeing what we can do with this new piece of hardware – and in the longer term, we look forward to continuing to work with National Instruments on exciting spaceflight-related projects!



*Strictly speaking it’s on loan for as long as we find it useful, but I don’t think we’re going to run out of uses for it any time soon

A Model Of Hummingbird

Over the holidays, Joe (seen in the first picture here with the excitingly stripy rocket) put his model-making skills to use by assembling a foamcore model of Hummingbird. The gimbal even moves! I’ve just been told it wasn’t actually supposed to move, so I should probably stop playing with it…

1

Having something physical gives a better idea of how everything fits together.

The model pointed out something that’d be useful to change: the original concept had a single platform where the electronics would sit, but we now reckon it’d work better to have a second platform just for the flight computer. Of course, unlike the version in the model, the roll cage needs to be extended over this too.

Initial Hummingbird Concept

Here’s a quick concept layout of Hummingbird. It’s inspired by David Wyatt’s Kestrel design, but uses a gimballed rocket motor instead of cold gas thrusters. (if you’re wondering what that’s about, there’ll be more about different attitude control systems in a later blog post!)

Artist's Impression png

It’ll be a very modular vehicle, so it’s easy to swap out parts for improved parts once it’s been test-flown a few times and we’ve spotted things that need improving (or, erm, after we’ve broken things and need to replace them…). Features you can see above include:

  • A platform to make batteries and the flight computer easily accessible and swappable.
  • Landing legs made of carbon fibre kite spars. Not shown is some sort of shock absorber – this is definitely needed, becase a solid-fuelled motor can’t be throttled, so we’ll always land with a bit of residual vertical speed. (If you’re really on the ball you’ll have spotted that even with a single motor it’s possible to set the thrust-to-weight ratio slightly above 1 and then move towards the ground by “tacking” or “fluttering” from side to side… but that’s a bit of a complicated flight profile for the first batch of flights!)
  • A roll cage, just in case Hummingbird lands on its head.
  • The red cylinder in the middle is a Klima D3-P motor. For scale, it’s 70mm long.
  • The grey boxes are placeholders for small servos as used in RC models, something like this:
Corona DS919MG

CAD model found on GrabCAD of one possible micro servo.

WR-1 Is Finished

We built a rocket! According to simulations, once it’s been completed, it should comfortably reach an altitude of 1000m, carrying an interesting payload. The flight computer’s design has substantial room for improvement. We hope to get more electronic engineers on board next year to work on an improved design!

I’ll write a follow-up post soon, telling the entire story of the design and construction of WR-1, also known as the I’m Sure A More Poetic Name Will Become Obvious Once We’ve Built It. For now, here’s a photo:

Photo of WR-1

The rocket, disassembled, in a handy carrying box.