Original URL: http://www.theregister.co.uk/2014/03/10/lohan_avionics/

Heroic Playmonaut wowed by LOHAN's bulging package

LOHAN team wraps Vulture 2 spaceplane avionics install

By Lester Haines

Posted in SPB, 10th March 2014 13:02 GMT

Pics Following the recent successful fitting and testing of our Vulture 2 spaceplane's Raspberry Pi and Picam rig, the Low Orbit Helium Assisted Navigator (LOHAN) team is relieved to announce that we've wrapped the permanent installation of the rest of the aircraft's avionics.

What's more, our heroic Playmonaut now has the proper seat we promised him, but more on that later.

Last month, we did an initial hook-up of the 3D Robotics Pixhawk autopilot, while we worked out just how we were going to cram in all the bits and pieces.

Here's the view last week, with the Pi temporarily removed to give us a bit of wrangling space. We'd already fitted the digital airspeed sensor and probe, and mounted the external LED and safety switch:

The Vulture 2 avionics running off four AA Energizer Ultimate Lithium batteries

Starting at the rear, first up on the agenda was to position the power supply module (top left) and provide a fetching pink plastic straw to accommodate one of the antennas of LOHAN team member Anthony Stirk's back-up PAVA tracker:

The rear of the fuselage showing wiring and a pink straw

The PAVA - destined to sit right at the rear of the front fuselage/nose assembly - has three antennas, which are actually guitar strings.

Anthony Stirk's PAVA tracker

While two will protrude from the fuselage, one has to run straight up it, hence the straw to prevent the antenna snagging on something during installation. LOHAN regulars will know that the straw colour choice is in deference to Anthony's penchant for pink gaffer tape.

With a free passage for the PAVA antenna assured, we could stick in a Velcro-covered battery mount board, and place the Pixhawk radio transmitter beside that. To the left you can see the styrofoam cradle for the PAVA...

The wooden battery platform with Velcro, running down the fuselage

...and here is the tracker held in place with our quite sensational "elastogrip" system: a couple of cable tie mounts, some metal clips and a rubber band:

The PAVA tracker mounted inside the Vulture 2 fuselage

It's worth noting that anything which needed gluing down, like the cable tie mounts in this case, was fixed with Scotch-Weld 2216 Epoxy ("certified for aircraft and aerospace applications" and "excellent for cryogenic bonding applications").

It's the same stuff we used to fix the Vulture 2's outer wings to the rear fuselage/inner wing (for photos of the aircraft's components, see here):

A close-up of the sanded wing surface

Taming the Pixhawk

So, onwards towards the spaceplane's nose. Next up on the list was how to tame the Pixhawk and its GPS/compass unit...

Close-up of the Pixhawk and untamed wiring

...which first required the placing of a new Futaba S.BUS R/C receiver. Unlike the previous ArduPilot Mega (APM) 2.6, with its eight separate inputs, the Pixhawk has a single S.BUS in, hence the new kit. Note the Pixhawk's I2C extender to the left:

Our Futaba receiver mounted in the Vulture 2

A block of wood on either side of the receiver, with some bolts and rubber washers provided support...

The wooden mounting blocks for the Pixhawk around the R/C receiver

...for the removable autopilot platform:

The Pixhawk mounted, with a rubber band retention system

The autopilot is separated from the platform by self-adhesive foam mounts, and more securely held using rubber bands. Behind it, we lovingly crafted a platform for the GPS/compass...

The wooden board for the GPS to sit on, with Velcro pads

...and with that last component Velcroed down, it was pretty much a wrap:

The GPS mounted, seen with the Pixhawk

Pi-stuffed crust

And now, ladies and gentlemen, we present a view of the whole thing shipshape and Bristol fashion, with the Raspberry Pi reinstalled:

View of the complete installed avionics rig

For clarity, feast you eyes on this astounding annotated version of the above:

Annotated version of the Vulture 2 avionics rig photo

A few notes:

The USB - serial interface to connect the Pi to the Pixhawk

Finally, for absolute clarity and those of you who haven't been paying attention at the back, here are all the components of the Pixhawk rig for your viewing pleasure:

Schematic showing all the bits and connections of our Vulture 2 Pixhawk rig

Oh, hold on, we nearly forgot. Our impressed Playmonaut took a moment to try out his new seat, courtesy of some Playmobil aircraft breaker's yard down on eBay. The USB to TTL acts as a handy table aboard what is a right-hand-drive spaceplane, which is only right and proper:

The Playmonaut in his seat aboard the Vulture 2

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