Original URL: http://www.theregister.co.uk/2013/08/19/lohan_flying_truss/

Flab-fighting LOHAN fettles fantastical flying truss

Lightweight Vulture 2 launch platform almost ready for action

By Lester Haines

Posted in SPB, 19th August 2013 07:58 GMT

Amid all the excitement surrounding the imminent appearance of the Vulture 2 spaceplane, the Low Orbit Helium Assisted Navigator (LOHAN) team has been beavering away on the fantastical flying truss which will carry our magnificent aircraft heavenwards.

For LOHAN newbies, and those of you who haven't been paying attention at the back, here's the launch concept, showing how we intended to mount the aircraft under a carbon fibre truss...

Revised graphic of our Vulture 2 launch system

...and here's how the truss looked this morning, outside the entrance to our secret garage/shed/bunker construction complex:

An annotated view of the LOHAN flying truss

You'll notice we've rethought just how to mount the launch rod to the truss. First up, we canned the aluminium plates on the grounds of weight and replaced them with 20mm square carbon fibre box sections.

This is how that works in theory...

Graphic of the revised launch rod mount system

..and here are the sections bolted to the truss:

Another view of the LOHAN flying truss

The upper part of the launch rod mount, bolted to the truss

The lower end of the launch rod mount, bolted to the truss structure

Obviously, the mounts are offset from centre, since they're bolted to the side of the longitudinal truss tubing, but our cunning plan is to bolt the launch rod to the side of the bottom of the box section, thereby bringing it back to the centre line.

This is how the rod will look when mounted under the truss.

Graphic overlay showing how the launch rod will sit below the truss

We've left the mounts extra long so we have a bit of play in the rod's vertical position in relation to the underside of the truss, to bring the Vulture 2 as close to the structure as is safely possible.

Similarly, we'll mount the longitudinal Teflon strip – designed both to protect the Vulture 2's wings on the ascent and prevent them from hitting the truss brackets as the aircraft exits the rod – when we have the aircraft in position and we can get the Telfon as close as possible to the wings' upper surfaces.

Regarding the rod itself, the planned titanium has gone the way of the aluminium plates. For starters, we couldn't easily get a 10mm titanium rod long enough for the job, and its weight was an issue anyway.

So, we grabbed a 4 metre length of 10mm diameter aluminium rod and a tube of similar dimensions, but they quickly went banana-shaped, revealing they just weren't rigid enough for the job:

The aluminium tube and bar laid over a chair, showing the degree of bend

We then had a bit of a lightbulb moment – or rather we realised a possible solution had been staring us in the face all along. So, we now have a couple of lengths of 10mm diameter carbon fibre tube – much lighter and more rigid than the aluminium, and which we can join seamlessly with a length of 8mm diameter carbon fibre tube.

The idea is to get the launch rod tube as long as possible, to ensure the aircraft exits at a decent rate of knots, and its control surfaces have a chance of getting a bite in the rarefied atmosphere at altitude.

Just how long we can go remains to be seen. When we've finally wrapped the truss and got the electronics enclosure and other bits sorted, we'll let you know just how long that is.

As you can see, the garden shed engineering continues apace, and our truss redesign has saved us at least a kilo in weight – critical if we are to avoid a ticking off from balloon wrangler supreme Dave "Fight the flab for a flighty HAB"* Akerman. ®

Bootnote

* HAB = High Altitude Ballooning.


Further LOHAN resources:

LOHAN - A Special Projects Bureau production in association with...

  • 3T RPD logo
  • University of Southampton logo
  • Applied Vacuum Engineering logo
  • Escher Technologies
  • Flashpoint Fireworks logo
  • HAB Supplies logo
  • Rock 7 logo

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