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back to article Flab-fighting LOHAN fettles fantastical flying truss

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 …

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Bronze badge

I do think I predicted this

but good to see you have found the issue and are correcting it. I hope the carbon tube will be strong and sturdy enough for the job. In my experience it can be pretty bendy as well on longer lengths.

I'll also restate my earlier idea, support the rod on 2 locations and put a "runner" on it that can detach from LOHAN once she's got her loins suitably heated. This does mean the length of the rod will be limited to however long you can support it over.

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Silver badge

Just out of interest

I realise it's very unlikely to happen, but if anyone on the ground does end up being speared by LOHAN's plumetting truss, have you got some sort of insurance to cover it? Or do you just plan to use the time advantage provided by GPS tracking to just hide the body before anyone else finds it?

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(Written by Reg staff) Silver badge

Re: Just out of interest

Yes, we do have insurance - it's obligatory.

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Bad Design

Sorry but anchoring a tube at on end and hoping it'll be stiff enough is just asking for trouble.

Surely a better design would have been to use a tube with a slot in it. The tube could have been clamped to the truss along its entire length. 2 inserts at the nose and tail of the aircraft would ensure that there would be no twisting upon launch, and as long as the inserts we made of a suitable material and the slotted tube well greased there wouldn't be much friction.

And wouldn't a 'blast' plate fixed to the truss behind the rocket motor give it a bit more of a kick on ignition. Yes newton's 3rd but I'm assuming that the mass of the truss, balloon etc is a lot more than the aircraft.

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Foam filling?

Might to tricky to do make but if you could foam fill the tube it would make it a lot stiffer without adding much weight.

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Silver badge

Length of the rod/tube

Are you sure you need it that long?

The longer the rod, the more it will interfere with the acceleration and slow it down + there is more chance of vibration tearing the rocketplane up.

All you need is to make sure that the rocket initially clears the truss, then it can continue to accelerate in free flight.

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(Written by Reg staff) Silver badge

Re: Length of the rod/tube

Fair comment, but another concern is that the Vulture 2 might hit the balloon. We're mulling the total length of the launch rod and will certainly do a balance test to see what's what.

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Re: Length of the rod/tube

Have you talked to anybody who flies S8E rocket glider? These are all launched from rails and, judging by the photos and what I remember from seeing them flown in competition, the launch rails are little longer than the glider's fuselage. More details are here: www.spacemodeling.org/s8/s8ercrg.html

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Bronze badge

watch your centre-of-gravity during launch

During the launch, CoG of the whole contraption will move from its static position to somewhere between the plane and electronics box. If this centre of gravity lands on the "wrong" side of balloon tether, the whole contraption may swing pointing your plane downwards. The longer the launch tube, the further away at the moment of launch the plane will be from electronics box, and the bigger chance (and longer time) for such swing to happen.

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Am I the only one...

... who's not sure if the rocket motor will fire yet?

I seem to remember from the REHAB chamber test that there was a significant pause before the motor fired properly - one interpretation was that the motor was burning a little and the exhaust gases built up increasing the pressure within the REHAB chamber, and once the pressure had built close to 1atm the rocket then fired properly.

I remember there being a comment in the article about investigating this, but I don't think anything ever came of it. Coupled with the only partial success of the igniter trial with the SPEARS board recently, how confident are you that it will actually fire ?

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(Written by Reg staff) Silver badge

Re: Am I the only one...

We're working on it, but you'll have to wait to see the results of further testing.

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Re: Am I the only one...

Excellent - I await further shed-related boffinery with much interest!

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There's a lot of bolts and plastic plate on that truss are you sure a couple of tubes of araldite and fibre mesh wouldn't be lighter?

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Are you secretly hoping that the tube/ rod will be the point of failure so that you can run a headline along the lines of: Flaccid rod foils LOHAN?

If so you are going to impressive lengths for a pun!

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