LOHAN's fantastical flying truss sprouts tail
Vulture 2 launch platform design shapes up nicely
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The Low Orbit Helium Assisted Navigator (LOHAN) team has been bogged down over the last few weeks in hypobaric rocket motor tests, but we've also been busy firming up the design for the Vulture 2 launch platform - our fantastical flying truss.
It's been a while since we last pondered this critical structure, which will be a carbon fibre triangular truss under which our spaceplane will soar aloft to its launch altitude.
The truss will also act as a platform for mission electronics, batteries, cameras, etc, all of which will sit inside a styrofoam box at the structure's rear end.
The LOHAN mission summary gives an overview of our cunning plan. Note that the Vulture 2 launch system - and specifically how we mount the launch rod - isn't the definitive design, and we've already got some planned changes based on input from our beloved reader experts.
LOHAN fans will recall we've already tested one flying truss model...
...which gave us enough information to come up with a definitive design.
Here's a one-quarter scale model of how the finished two-metre-long truss will actually look, complete with a mocked-up electronics enclosure and, provocatively, a shapely rear end:
We suspended the truss at its planned inclination of 20° from vertical and let the wind do its stuff. The biggest potential problem on the ascent is wild spinning, but our design has one big advantage over the Paper Aircraft Released Into Space (PARIS) solid main payload box.
The fact that we have an open structure at one end of the truss, and the electronics enclosure at the other, causes a weather vane effect which tends to dampen the spinning. By adding a tail, as seen in the above snap, we've been able to further reduce spin as the entire truss naturally orientates itself into the wind.
So, we're pretty happy with that, and are poised to buy some carbon fibre bits and get on with the full-fat truss. As noted above, just how we mount the Vulture 2 launch rod assembly is still to be firmed up, and since it depends on the final dimensions of the spaceplane, we'll deal with that when the Vulture 2 emerges from the 3D printing machine.
As we move inexorably closer to a stratospheric climax, your comments/suggestions on LOHAN's progress are warmly welcomed. ®
Further LOHAN resources:
- New to LOHAN? Try this mission summary for enlightenment.
- You can find full LOHAN coverage right here.
- Join the expert LOHAN debate down at Reg forums.
- All the LOHAN and Paper Aircraft Released Into Space (PARIS) vids live on YouTube.
- For our SPB photo archive, proceed directly to Flickr.
- We sometimes indulge in light consensual tweeting, as you can see here.
LOHAN - A Special Projects Bureau production in association with...
COMMENTS
Re: What goes up generaly comes down...
Soles are salt water fishes, and a quick shufti with a map and a ruler suggests that the nearest sole, unwary or not, might be found some 1807 brontosauruses (250km) west from PARIS' launch site, on the Portuguese coast, although I can't tell if one could actually find soles (unwary or not, as noted already) at this location. Note that I have discounted soles on display at a fishmonger, as those are a) generally quite stationary in a batch of ice and therefore not happening to be passing by, and b) by and large protected from falling aerial debris by shops' roofs or market stall awnings.
If you meant the type of sole generally found at the contact point between a standing or walking being and the surface it's in contact with: it's their very location that makes them unlikely to be susceptible from being hit by Lohan's truss; the upper parts of that being's anatomy would be hit first, unless it was doing a handstand or had a habit of walking around with a shoe on its head.
Vane in vain?
Will the 'weather vane effect' work when the balloons are travelling at the same speed as the wind?
Re: Launching into the wind.
We've tried the weathervane approach in an effort to mitigate spin rate and consequent mal de mer when viewing live video. It doesn't work very well, and here's why:
The dominant airflow vector is vertical, since the balloon envelope has far greater drag area than any reasonable vane. However, even minor wind shear will cause the payload line to "swing and sway with Sammy Kaye", and the tail fin (weathervane) will respond nicely to that with a series of snappy 180-degree turns.
What DOES work quite well, however, is increasing the rotational inertia around the payload's vertical axis. On our GoPro DVR, we installed a pair of 1m long 1mm x 3mm carbon fibre flats rigidly cantilevered horizontally from the payload structure in opposing directions with 10 g of Pb weight added to each extreme end. This resulted in a rather profesional-looking slow and smooth pan rate looking at the horizon.
Since there's negligible horizontal airflow velocity, there doesn't seem to be any point in your endeavor to launch LOHAN into the wind, but keeping the spin rate down might make for a more manageable launch trajectory.
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