back to article LOHAN's flying truss: One orb or two?

The roll-out yesterday of our Low Orbit Helium Assisted Navigator (LOHAN) fantastical flying truss prompted a flurry of comments from readers unimpressed with our twin-globe proposal. Click here for a bigger version of the LOHAN graphic To recap, our cunning plan for the Vulture 2 spaceplane launch platform involves a …


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  1. EddieD

    Simple solution

    LOHAN is an amazon warrior, so wondrous globe would be appropriate.

  2. Jamie Kitson


    Does the truss really need to be horizontal? It would be much easier to keep it at a steady angle if it was just hanging straight down from balloon(s). You can then adjust the angle of the things on it to the horizontal.

    1. VeganVegan

      Re: Vertical

      I like this idea:

      The pressing issue is the balloon(s) swelling so much that it / they block LOHA's path. Perhaps cutting the balloon tether & launch can be coordinated? Another idea is to intentionally bursting the balloon. Launch LOHAN during free fall, using girder-mounted aerodynamic surfaces or little drag chutes to stabilize its orientation. This is easiest if the girder is imagined as an arrow: add drag-inducing features to the top of the vertically hung girder, and a pointy tip at the other end

      1. sisk

        Re: Re: Vertical

        Following that line of thought, perhaps it would be better to rig some sort of sensor to detect when the balloon bursts and light LOHANS fire at that exact moment. I don't know how practical that is, but if it's doable you kill two birds with one stone: you get maximum altitude and you get the balloon out of the way.

        1. taxman

          Re: Re: Re: Vertical

          The trouble about lauching when the balloon bursts is flying through a mass of debris that would probably tangle around the wings of the bird. They make a heck of a mess when they blow.

      2. Pat 4

        Re: Re: Vertical

        Cutting the line would be a much better option because blowing the balloon creates a risk that some of it's material will land on the truss itself and ruin the launch.

    2. Jamie Kitson

      Re: Vertical

      After writing this post I then found the original design article and realised that this has already been gone through, soz!

  3. Kevin Johnston Silver badge

    OK, probably stupid but.....

    Does the rocket have to be suspended below the balloon?

    Had a vision of a totally ridiculous idea with three smaller balloons close-coupled on a small frame which had a central rod rising to the launch platform mounted above the balloons. the additional lift from the three would allow a weight below to keep the rod 'vertical' and if one balloon bursts early, having the balloons close-coupled above the centre of gravity for the weight/rod/platform will keep the orientation.

    Accelerometers or similar to spot if lift is lost when the first burst pops the other two.

    Gives a headline option for 'Fun-bag Three' (pleased to say that although I remember the band I don't remember any of their tracks).

    1. Ralph B

      Re: OK, probably stupid but.....

      Weather balloons get really huge at high-altitude which would probably cause problems if three were tethered close together.

      What about having the rocket sitting on hat-like platform on top of a single balloon and the relatively heavier avionics/cameras etc. hanging off the bottom of the balloon as a counter-weight?

      1. Kevin Johnston Silver badge

        Re: Re: OK, probably stupid but.....

        I did think of a 'halo' truss but the change in size of the balloon would be even more catastrophic as at low altitude the balloon would bulge inside the halo plus there is the problem of keeping it in place at the top of the balloon.

        This was the thinking behind having a rod up past the balloons, may cause sympathetic detonation at burst but if you have calculated the gas volume correctly then you would be launching before that point (excepting a balloon failure of course).

        Did a lot of work with weather balloons when I was an apprentice radar engineer so I do understand how big they get (mahoosive springs to mind) but again by using three you would need much less gas per balloon improving your burst height.

        1. Martin Gregorie Silver badge

          Data! we need data!Martin Gregorie

          Is there any reliable data on just how big one of the balloons can get? If not, are they so expensive that you couldn't slowly inflate one with air on the ground and track how big it gets before it bursts?

          It seems to me that this is essential data because the beam length needs to be at least twice the burst size of a balloon. Three times would be better if LOHAN is to have a good chance at a vertical launch without hitting one of the balloons.

        2. Ralph B

          Re: Re: Re: OK, probably stupid but.....

          Instead of a 'halo' truss, my "hat" rocket platform be attached to a circular net with long, thin strings radiating around the balloon to connect with the cable holding the avionics etc.

          The length of the strings would allow the balloon to freely expand. The weight of the avionics would provide the counter-weight to keep the net-mounted rocket platform to remain at the top of the balloon.

          So, in this order:



          circular net

          strings ballon strings

          strings strings



    2. Marco van Beek

      Re: OK, probably stupid but.....

      Just a thought. If you use three balloons, and assuming they are all the same size and tethered equally, there would probably be a gap between them that might be big enough to allow a vertical launch from a platform underneath.

  4. DragonLord

    Would it be feasible to have some sort of mobile weight attached to a 2 way mercury switch such that when one side of the truss goes up the weight will travel up a rail of some description to the end that has the most lift, thus counteracting the lift (assuming it gets far enough before the weight is vertical)

  5. wiggers

    How about...

    O O

    | \ / |

    | \ / |

    | X |

    | / \ |

    | / \ |



    Might lose something in formatting, but essentially connect both ends of the truss to both balloons. If one starts to rise faster than the other it will take more of the weight and slow down, keeping them in balance.

    1. Anonymous Coward
      Anonymous Coward

      Re: How about...

      Or keep the new arrangement, and connect two balloons above the swivel instead of one.

      Would make a better looking "set" IMHO, and - ehem... - that extra lift must be necessary or something right?

    2. Anonymous Coward
      Anonymous Coward

      Re: How about...

      This is what I would vote for with the advantage that even if one burst it should stay relatively level.

  6. b166er

    Can't you drape a net/strop over the balloon and balance a vertical launch platform on one side, with the visual apparatus and recovery system on the other side?

    If the tails of the net/strop are rigid and balanced, that should ensure a vertical launch trajectory shouldn't it.

    1. b166er

      LOHAN's saddlebags, if you will.

  7. Tom7

    Two possible solutions

    1. Sling a weight from two lines connected to each end of the truss. If one end starts to rise above the other, the weight will transfer to the line hanging from that end and rebalance it. Downside: extra weight.

    2. Four balloons on a triangular truss structure. Tie one to each corner and a fourth in the middle that is connected to all three corners. Again, any imbalance will cause the central balloon to take more weight from the other two corners and rebalance it. This gives you three mid-truss points with no balloons above them.

  8. Tom 38 Silver badge

    IANAE*, but couldn't you do this with an array of balloons held together in a ring. The platform is suspended below the ring, and shoots the plan through the ring.

  9. dotdavid
    Paris Hilton


    Probably won't work, but is there any way of just having one balloon and making the bursting of the balloon trigger the launch somehow? I guess lots of balloon guts would get in the way a bit, and it adds a bit of complexity, but to my untrained eye it looks feasible.

    Paris because wasn't something similar done for PARIS, based on altitude?

    1. Code Monkey

      Re: Maybe

      IIRC the PARIS release mechanism froze and the bursting of the balloon freed it. A happy accident.

  10. AndrueC Silver badge

    The truss doesn't look horizontal in that graphic to me :)

  11. Daniel 1

    One balloon, two balloons... It barely matters how many, they'd have swollen to the point where they filled 80-90% of the available sky above the rig, anyway, as far as I can see, and you're only going to get a ridiculous little spurt of extra altitudefrom any engine you use, compared to what the balloons have already provided.

    Better to consolidate all your LOHANs into one, easy to manage, package.

    1. M Gale

      Ridiculous spurt.

      I I recall correctly, the SPB team have decided that the wimpy little E class thing they were testing is far below the power levels required, and could well be going for M class and above. Those things don't provide a ridiculous little spurt. More like a ridiculously powerful kick in the pants and several thousand feet of altitude in about five seconds from ground level. From 80,000 feet with little atmosphere in the way, who knows how high it'll go?

      1. Anonymous Coward
        Anonymous Coward

        Re: Ridiculous spurt.

        is there a reasonable you tube video demoing one of these M class to get a visual idea of thrust the launch platform will need to withstand ?

        im thinking about actually using gravity to start forward momentum off at the top of a half circle track tripping the M class main engine start at the dead centre and exiting the track at a 45 or greater vertical angle like the scifi film i forget the name of right now LOL, simple and effective and you might as well use what's available to you at the great hight for free to reach flight stability speed ASAP rather than waste it.

        1. M Gale

          Re: Re: Ridiculous spurt.



          Though I really hope a Q class is feasible:

  12. Elthrin

    Just move the Vulture 2

    How big do these balloons actually get?

    Launching from the end of the truss, rather than the middle should allow for a steeper climb.

    Locating the Avionics, cameras etc further towards the other end of the truss would balance everything out and give a better view of the launch.

    Having the launch vector parallel to the truss may also reduce any change in launch azimuth caused by the platform swinging away at ignition.

  13. thomas k.

    easy solution?

    How about, instead of a single truss, a + shaped one (with the launch pad in the center where the bars cross) suspended below a donut-shaped balloon?

    Should provide some great headlines, as well - the rocket shot upward through the enormous hole, or some such.

  14. Albert.G

    Self balancing strings


    If you attach a string from each balloon, entering 1/3 into the truss and attached to the battery, when one balloon starts going higher than the other, the string will pull the weigth to its side, keeping the system balanced. If needed, weight displacement can be amplified with a lever.










    Note : The · symbol just means empty space

    1. wiggers

      Re: Self balancing strings

      Ah, now why didn't I think of using dots!

  15. Bill Neal

    ...soon as we can get our hands on some helium.

    How difficult is it over there?

    In 'merica all we have to do is go to walmart. $20 for a tank the size of a standard 30lb refrigerant jug.

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: ...soon as we can get our hands on some helium.

      I'm right out in the sticks, and the nearest supply of helium is pretty well the Sun.

      1. bertino

        One of these might be useful...

        Have a circular base section. Attach 3 balloons tethered to this base. Have the electronics in the base too for balance. Fix the bottom thick end of the pole to the circular base. The pole will then poke out above the balloons, stick launch module on top of pole, job done, vertical launch. There are then 2 questions.

        1) Will weight of pole at around 800g be too much?

        2) is 9.5 metres long enough, how large do the balloons get at altitude?

      2. Anonymous Coward

        Re: Re: ...soon as we can get our hands on some helium.

        best line yet.

      3. TeeCee Gold badge

        Re: Re: ...soon as we can get our hands on some helium.

        Wow, that is a long way out in the sticks.

        Here on planet Earth, all the Wal-Marts in the US are closer to any point on the surface that I might find myself at than the Sun is......

      4. Anonymous Coward
        Anonymous Coward

        Re: Re: ...soon as we can get our hands on some helium.

        while i remember, dont forget to order some cheap chemical heat packs for the electronic packing as they may need it to keep functioning up there, BTW you didnt said just how big the uni guys are making the rocket glider or if you hope and plan to get above the world record for beating the record for Unmanned gas balloon 53.0 km (173,900 ft)

        to launch the LOHAN) flight.

  16. TRT Silver badge


    hang an octohedron by its top apex to the balloon tether and launch through one wall of that. Hang the recovery parachute from the bottom apex and put the logging equipment in the bottom half of the octohedron. Forget about launching vertically! With all that tossing, who's to say what's vertical anyway?

  17. Jan 0 Silver badge

    Wrong balloon?

    Why not use a balloon that doesn't explode?

    Either have a pressure relief valve, or use a large, partly filled, inelastic balloon filled with just enough helium to reach a target height. An aluminised mylar balloon should do nicely, but you'll need to glue the seams (you can weld plain mylar, but it will lose helium faster).

  18. Gotno iShit Wantno iShit

    IANAHABE* but how reliably can the moment of ballon burst be detected and reacted to? Or can the balloon be popped on demand?

    I Am Not A High Altitude Baloon Engineer.

  19. Anonymous Coward
    Anonymous Coward

    Why not release the balloon just before ignition?

    The balloon will be out of the way pretty much as soon as the weight of the launch platform is released.

    If you can get the timing correct, the launch platform will still be pointing the right way (up), otherwise design a launch platform that falls with the rocket pointing up.

    1. Anonymous Coward
      Anonymous Coward

      Re: Why not release the balloon just before ignition?

      Sort-of this. one baloon pops, the truss swings down vertical. the plane swivels on the truss so it points upwards, pop the other baloon and launch along the length of it? LOHAN orbs burst, slides along truss, ejects into space.

  20. david 63

    How do JPA do it?

    They seem to get good launches with 2 ballons.

    1. Martin Gregorie Silver badge

      Re: How do JPA do it?

      Just what I was going to say. So, ask them.

      Worst thing that can happen: they won't tell you.

      1. ryanp

        Re: Re: How do JPA do it?

        I was thinking just along these lines, but instead of asking you can watch it:

        Of course their rig looks a little more complicated.

  21. Alfie
    Paris Hilton

    don't know about the horizontal issue, but...

    ...why would the two balloons need to be on long tethers that could twist around each other?

    I assume that the plan is to make the girder long enough to leave a big enough space to shoot the vulture between them (ooh, err, missus!); then all you need to do is make sure the tether lines are less than the length of the girder (or maybe less) and the two balloons shouldn't get tangled.

    As for the horizontal issue, I'm going with Albert G's self balancing strings dragging the gubbins around to balance it out. That and using a spring balance when filling the balloons with helium to get an approximate match on lift generated by each one before launch.

    < So simple even Paris could manage it.

  22. NoneSuch Silver badge

    You can remove a good portion of either end of the triangular support and mount the string from the balloon near the two cameras. The upside down V of the string as shown in the diagram would be well clear of the LOS for the camera lens and you would save a few inches of material at either end. Everything else outside of the cameras could be removed easily as it does not seem to serve any purpose beyond being a mount point for the string.

  23. VeganVegan

    Swivel mount

    How about mounting LOHAN, not directly on the girder, but on a rail hung off of a swivel mount, so that LOHAN will point up vertically, regardless of whether the main girder is horizontal or not. Have to make sure that the swivel doesn't freeze up, perhaps by using kel-f surfaces, and loose tolerances (bolt size << hole size). If you want to guard against the other axis tilting, you can put in a double swivel mount...

  24. Flocke Kroes Silver badge

    A long piece of fishing line.

    Nylon: Strength=78000000N/m^2, density=1150Kg/m^3. Gravity = 9.8N/Kg.

    Mass of Nylon = (Mass of payload) * (length) * 9.8 * 1150 / 78000000

    A 10Kg payload on a 100metre line costs 145g. Reliable real life figures are about double theoretical values, so 300g of fishing line for 9.7Kg of payload.

    Zylon, Spectra and Kevlar are all better materials if you can get them:

  25. Mr Young
    Thumb Up

    I said it before - sharp pin on top of LOHAN!

    Hopefully the turbulence won't send the LOHAN control system bananas when the ballon pops as she goes through it?

  26. M Gale

    I posted a stupendously badly drawn design to the SPB team a while back that called for balloon triplets tied to a central line at very long intervals. I know people have had success with the design, and the clusters can be positioned far enough apart on the line that as each cluster explodes it diesn't take the rest with it. Shouldn't be too hard to fill either, just make sure each cluster is tied down before filling and that you release the top ones first!

  27. Inventor of the Marmite Laser Silver badge

    Well if ya gotta have just one big orb

    It'll need an appropriate name. I offer

    M - onolithic

    O - perational

    N - avigation

    O - bject for

    T - ransit

    I - gnition and

    T - akeoff

    T - elemetry

    I - nstrumentation and

    E - lectronics

  28. Dave 32
    Thumb Up

    Be a little wary of the Helium you buy at Walmart. It may or may not be pure Helium. Since it's typically only used to inflate party balloons, maximal lift isn't required. Besides, those tanks are so small that you'd need several of them. It's probably cheaper to rent a real tank from a major gas supplier (Linde/AirGas/Scott Gross/etc. here in the USA).

    There are some groups around who use Hydrogen for high altitude balloons. While some care is needed to avoid the "Hindenberg" effect, it's not all that dangerous. And, it's typically a lot more available and less expensive. But, do some investigation first.

    I'm not a big fan of the two (or three or four) balloon idea. Given the extreme winds at altitude, trying to maintain any kind of stable flight pattern with multiple balloons (even if they are tethered onto the truss) will be difficult, if not impossible. Plus, there's that thing about having twice as many components means that there is twice as much chance of something failing.

    An "impossibly" long tether isn't completely outside the realm of possibility. When you're at 100K feet, so what if your tether is 1000 feet long? Even a more modest 250 foot tether will still keep the truss well away from the balloon. And, with the swaying of the flight train that it's going to experience, that very well may give adequate clearance for the vertical launch. Timing will be the tricky part.

    (more in a moment...)


    P.S. Cute intern.

    1. The First Dave

      "so what if your tether is 1000 feet long?"

      Well, the rocket will only reach 500 feet or so, so you do the maths...

    2. sisk

      Hydrogen should be ok. The hydrogen was only one variable in the death of the Hindenburg. More important was whatever started the fire in the first place. Since you're unlikely to paint your weather balloon with accelerants or have passengers who are smoking there should be no problem.

    3. Steve Hersey

      Another advantage of a Very Long Tether

      is that the natural frequency of oscillation of a very long pendulum is very low, which acts to your advantage.

      Put a small drag chute or streamer on one end of the truss, and it will remain pointed upwind, so the rocket will take off crosswind, rather than straight into the balloon. At that point, it matters not whether the balloon is upwind of the truss or downwind, it'll be over one or the other end of the truss and out of the way of the launch.

      1. Martin Budden Bronze badge

        Re: Another advantage of a Very Long Tether

        Wind? What wind? A free-floating helium balloon moves with the air it is floating in, so the baloon's lateral speed compared to the air is always zero.

  29. Dave 32
    Thumb Up


    Of larger concern may be the wind induced swaying. There are some groups which have flown gyroscopes as a stabilizing element, and some that have used air foils mounted on long rods to stabilize the platform. The truss would seem ideal for mounting some airfoils on the ends to help stabilize it. Otherwise, it will sway, and probably pretty violently.

    Of course, it may be possible to use the swaying to time the vertical launch so that the rocket misses the balloon. Bill Brown's group out of Huntsville has done some similar work with the rockoon they launched a number of years ago. Some research may help.

    For something really weird, have you considered mounting a motor (probably electric, given the problems with running a gasoline/diesel/methanol/etc. motor at that altitude) with a propeller on one end of the truss to give it a sideways push just prior to launching the rocket? That might make the airfoils even more useful on the truss for stabilizing it. The only downside is that that may change it from a balloon/rocket combination to a balloon/airplane/rocket combination. I suppose the same could be done with a few small rocket motors mounted on the end of the truss to give it a "forward" push just prior to the vertical launch of the primary payload. Yeah, it's be tricky. REAL tricky. But, it might just work.


    P.S. Still a real cute intern! :-)

    1. The Indomitable Gall


      At that altitude the air pressure's so low that you'd need a whacking great propeller to shift enough air to move the rig, surely?

  30. Paul F

    probably unfeasible

    What about an accelerometer or two rigged to an Arduino that's set to sense the angle of the platform, so that as it inevitably swings back and forth it senses an appropriate launch trajectory?

    1. M Gale

      Re: probably unfeasible

      I believe the existing plans are to use a readily available open source autopilot system and hack it to fit. That probably includes gyroes and accelerometers, and the solid state ones are tiny these days too.

  31. Owen Smith

    my brain hurts but...

    you could use 3 balloon/truss T formation and a launch tube for vulture 2 so it clears the balloons.

    you could add some complicated pulley system to keep things upright to compensate for imbalanced lift

    1. Dozer

      Re: my brain hurts but...

      This is what I was thinking. Plus the launch tube would assist with a higher muzzle velocity.

  32. M Gale


    Some kind of compressed gas nozzles on the aircraft. It's more controllable than solid fuel, and it only needs to last long enough to lift the craft from the launch vehicle and guide it upward while the main motor kicks in. Better if the whole lot can be jettisonned or be made as a sled that the aircraft rides on for the first 50 feet.

  33. The Indomitable Gall

    Feedback for apprentice boffin...

    A boffin's pipe should lie at least 15 degrees off the mouth's normal (otherwise known as "the nose"). This allows for a relaxed, comfortable light grasp when pondering a question put to you by a fellow intellectual or an inquisitive member of the public.

    A pipe held co-incident with the normal offend causes offense or injury when you inadvertently prod someone with it.

  34. Helena Handcart


    IANAE, but I suspect most suggested forms of counterbalance could form unwanted oscillations, especially active ones such as the mercury tilt switch idea. Also Hg's melting point is merely -38.87 degrees C (according to Google).

    I like the cross-rigged dual balloons idea of @wiggers, but the wires would get in the way. However, it was suggested by several people a while back that some sort of pre-launch guide rod could be used to catapult the rocket clear of the platform while the motors are firing up, this could be angled in such a way as to clear any rigging and expanded balloons.

    A possible problem with the cross rigging, or indeed any rigging of two balloons, is if one balloon is sufficiently quicker than the other, the rigging could jerk taut, straining the fixtures and jolting the whole platform.

    Perhaps, during the initial inflation of the balloons, strain gauges could be placed on either end of the truss and launch can only go ahead when they both measure the same amount of lift.

  35. Simon_E

    How big do they get?

    A quick search suggests a diameter at burst altitude for a (presumably large) 1,200 gram balloon is 30 feet (9.144 metres).

  36. drben

    Equalise pressure?

    If you had a pneumatic connection between the two balloons (i.e. a hose), that would keep the pressure equal in both...

    What I can't say is whether that would mean they had the same buoyancy - anyone?

    Perhaps overcomplicated at launch time (or perhaps easier as you could fill both at the same rate?), but no moving parts!

    1. M Gale

      Re: Equalise pressure?

      What would happen is that as soon as you connect the hose, the balloon with the greatest surface tension (ie: the smaller one) will squeeze air into the balloon with the weaker surface tension, which would be the larger balloon. Sounds counterintuitive until you think about it.

      1. The Indomitable Gall

        Re: Re: Equalise pressure?

        This seems wrong. For one thing, wouldn't the bigger one have the greater surface tension, because it's under tension from like, you know, the air in it...?

        I may have to go to the supermarket for balloons and drinking straws now....

        1. Vic

          Re: Re: Re: Equalise pressure?

          > This seems wrong.

          It does. It's counter-intuitive, and just "feels" wrong.

          But it's actually completely correct.

          > For one thing, wouldn't the bigger one have the greater surface tension

          Laplace's Law tells us that the larger a vessel, the greater the wall tension required to contain a given pressure. So for the same wall tension, a smaller balloon will have a higher internal pressure. It is the pressure difference between the balloons that drives the air migration, not the wall tension.

          > I may have to go to the supermarket for balloons and drinking straws now....

          Try the experiment several times - you'll spend your time after the first couple of gos looking for the experimental error that caused a result you weren't expecting...


          1. Amonynous

            Baloon Animals

            Anyone with kids will have had to endure numerous children's 'entertainers' making balloon animals, including the dog/poodle with the long thin tail with a 'ball' on the end (and numerous similar things). They are created *without* twisting off the ball at the end to keep it inflated.

            Whilst 'common sense' suggests that the air under pressure should want to distribute itself along the whole length of the balloon turning it in to a sausage, it is pretty much impossible to do so even if you squeeze the ball to do so.

            A practical example of a well known, but completely counter-intiutive, experiment.

  37. Alan Esworthy

    2-stage, sort of

    Put wings/stabilizers on the truss and a small rocket motor on one end, turning it into a flying launch platform. Lohan launch would consist of first lighting the truss-mounted motor and cutting loose from the balloon tether, followed some seconds later by launch of Lohan itself from the truss platform/aircraft.

  38. Vic

    How about a hinge?

    Some more deranged complexity for you...

    Build the truss with a hinge in the middle. Attach the balloon to both ends. Add a (weak) spring to pull the two truss halves together.

    The balloon will keep the truss halves apart - until it bursts. The truss halves then meet. There is your maximum altitude detector - fire up the ignition. The balloon is no longer in the way...


    1. Stoneshop Silver badge

      Re: How about a hinge?

      Even simpler: a leaf spring. One end of the leaf is fixed to some part of the launch platform structure, the other end is pulled free from that structure by the balloon cable. As soon as the balloon bursts, the leaf spring snaps back, hitting a contact pin causing the launch sequence to be initiated.

      1. Vic

        Re: Re: How about a hinge?

        > As soon as the balloon bursts, the leaf spring snaps back

        That was actually my first thought - but it won't work.

        It assumes that the force from the balloon will be strong enough at all times during the flight to counteract the spring tension.

        My (fairly minimal) flying experience tells me that it is common to hit turbulent air of one sort or another whilst in flight; it would only take a very brief down-draught on the balloon to cause the rocket to fire way too early.


        1. Stoneshop Silver badge

          Re: Re: Re: How about a hinge?

          Well, I am not an aeronautical engineer either, but I expect turbulence to work quite differently on a mass suspended under a balloon (and the balloon itself) compared to a plane which has a) lifting surfaces and b) relies on serious airflow across those surfaces to stay airborne.

          It's not clear from the PARIS video whether it encounters turbulence to the extent that the leaf switch idea won't work at all, or that it needs to be activated only after reaching some minimal altitude or something. The advantage I see is the simple construction, with very little chance of it fouling.

          Another thing I'd like to see is a video, with the cam pointing up towards the balloon, of the burst. Also, with a ruler in the field of view at, say, one meter from the cam you would be able to calculate the expansion just before that moment. Which means sending a balloon up for research purposes; a definite plus on the boffinry scale.

  39. CmdrX3

    Sidewinder missile style (except vertical)

    What about one single balloon in the centre of the platform with the avionics and camera where they are. At the tip of the platform a vertical launch guide rail and at the opposite tip a counterbalance. Not sure of the width of a fully inflated balloon but even so, placed at the tip of the platform it would allow the launch trajectory to be reduced and more vertical.

    1. This post has been deleted by its author

  40. Anonymous Coward
    Anonymous Coward

    Why not tie both balloons to a single cable

    and run the cable through the truss with a pulley at either end?

    Apologies if anyone else has suggested this, it didn't leap out while I scanned through the comments.

    1. Anonymous Coward
      Anonymous Coward

      Re: Why not tie both balloons to a single cable

      Even better: two cables of identical length running through the top tubes of the truss so it's triangulated and thus going to keep the truss level in both roll and pitch

  41. This post has been deleted by its author

  42. LoneWolfe

    Would a diamond cross truss system with the balloons mounted in the centre of the cross and LOHAN, avionics and camera plus counterweight mounted on poles at each point be a possible solution?

    . . . . . |

    . . . . . |

    . . . . / | \

    . _____/_ | _\______

    . . . . \ | /

    . . . . \ | /

    . . . . . |

    . . . . . |

  43. Starboard Tech


    How about a small rocket thruster on the truss that will fire to push it out to one side just before the Lohan is launched?

  44. jubtastic1

    One balloon



    .......................(............) balloon




    ..............................| single wire




    ......../\............../............\ dual wires


    ........|.|____/___________\__________OOO counterweight

    ........|V|V|V|V|V|V|V|V|V|V|V|V|V|V|V|V|V|V|V|. Truss

    Stick the rocket on one end of the truss so it's as far away from the centre of the ballon as possible, use the rest of the equipment as a counterweight thats extended further out the other side to account for the disparity between the weight of the rocket and the equipment.

    Jubs your uncle

  45. Glen 1 Silver badge
    Paris Hilton

    my two penneth worth

    single balloon

    tether to nearer the end of the truss

    tether in a triangular fashion as above, but with the truss extended farther out one side of the triangle

    Add counter weight to keep things balanced.

    Card fins on the truss to keep things stable

    (well, as stable as the wind... which should be marginally better than the payload pirouetting in said wind)

    Paris, because I'm not a qualified engineer either.

  46. Anonymous Coward
    Anonymous Coward

    Or you could use one balloon, an 80 foot tether and launch at 5 degrees off vertical.

    Do I get a KISS?

  47. RetiredGeek

    LOHAN Strut

    LOHAN will need a rail to ride until enough speed is built up to make the fins aerodynamically effective anyway. You could make the truss in the form of a "T" with relatively short horizontal bar attached to each balloon and the long vertical bar for the launch rail. The weight of the rocket etc at the base of the 'T' will (hopefully) keep the rig oriented vertically. The horizonatal arms of the T will serve to "lift and separate" your huge lifting orbs (and thus satisfy your editorial requirements).

    1. beast666

      Re: LOHAN Strut

      This touches on what I'm worried about... at the altitude of launch will the fins of the rocket be aerodynamically effective anyway? You'd certainly have to make them much bigger than would be needed at sea-level.

  48. nsld
    Thumb Up

    Mae a balloon doughnut

    get ten balloons and make a doughnut around a circular support frame leaving a big hole for the rocket to launch through.

  49. Long John Brass
    Paris Hilton

    It's not the montion of the LOHAN

    It's the angle of the dangle.

    1 or more balloons connected to a single a 20-30 meter tether

    the truss should be balanced to that it dangles at a near vertical (5-10deg) angle

    LOHAN can then ride a rail under the truss to allow a stable launch

    It might be a nice touch to build some sort of bra arrangement of you are using two balloons

    you could connect the teather to the bra-strap :)

    1. Captain DaFt
      Thumb Up

      Re: It's not the montion of the LOHAN

      "you could connect the teather to the bra-strap :)"

      I see what you did there...^ Freudian slip, or dirty wit?

  50. spegru

    T Shaped

    I suppose if it *must* be two balloons to get a vertical launch, then you could have a T shaped truss with a weight on the lowest end. That way when the truss stops being horizontal, the counterweight (as long as it's rigidly attached to the horizontal part) will tend to make it straighten out again.

    It would tend to make the whole truss a bit of a monster though....

    However I still think a single balloon with two long strings, plus a inclined launch of say 15% should be ok to miss the balloon

  51. Richard Altmann

    The Pilot?

    Any plans on how to extract the pilot from the Swedish Lesbian Enclave for his next mission?

    1. butting

      Re: The Pilot?

      Send them up with him, for LOADS of high-altitude nookie.

  52. Yet Another Anonymous coward Silver badge

    Two balloons

    The upward thrust of the massive inflatable fun bags would be restrained by them being held pressed together in some sort of flimsy lace net with straps attached to the payload

    An arrangement also known as the:

    Constrained Lifting Equipment And Vertical Anti Gravity Environment - CLEAVAGE

  53. Sceptic Tank

    So are balloons on strings above this contraption a definite requirement? Why don't you mount those balloons underneath the thing inside a basket of sorts where they cannot expand? Hang the batteries underneath to keep it pointing in the right direction.

    I also recommend training a space monkey to go along to handle unforeseen eventualities.

    1. The Indomitable Gall

      If you were to build a platform above the balloons, surely you'd want 3 balloons? 2 points describe a line, and the platform wouldn't be stable if it was only supported on one axis. 3 points describe a plane -- and that's what we'd be looking for here....

  54. saundby

    Balloon Restraint Apparatus needed

    To share lift, and separate orbs for passage of thrusting vehicle between.

  55. Vladimir Plouzhnikov

    How about

    Weighted canards on the vehicle?

    Launch horizontally, the canards will droop due to the weights, pitching the vehicle up.

    Once the trajectory becomes vertical, the weights will no longer deflect the canards and the rocket will go straight up.

    Will need some experimenting with the weights and limiters on the canards to give the turn radius large enough to clear the balloon but tight enough to make the turn while the motor is still going. Launch downwind, to make things easier.

    Here is what I mean:

    Aerofoils at 60,000ft will generate less lift than at sea level density, so the canards will need to be scaled up accordingly.

    1. M Gale

      Re: How about

      Unfortunately, in a tight loop, you will feel the right way up even when you're upside down. Nothing that relies on weights, balances, or anything that will stop working properly if gravity doesn't act like it should, will work on an aeroplane. This is why autopilot systems are a little more complex than attaching a pendulum to the ailerons.

      1. Vladimir Plouzhnikov

        Re: Re: How about

        Provided the vehicle is stable in roll, there is no reason for it not to work if the counterweight is calibrated properly. There is thrust, gravity, turning G-force. With horn-balanced canard the drag force's turning moment can be neutralised. Problem is that it may be too complicated to tune the system by trial and error for it to be practical.

        Also, after I posted the first message I remembered that LOHAN needs to fly back to a landing, which will be difficult with a system that wants to pitch up the craft into vertical all the time. It will just constantly stall and fall :-(

        1. M Gale

          Re: Re: Re: How about

          See here's the problem: You have a system that is relying on gravity to tell it where "down" is. WHile LOHAN is resting nicely on the launch platform, this system will be fairly, if not entirely accurate. As soon as the rockets kick in however, the aircraft will get a massive kick in the pants which will make any gravity-based system think that "down" is toward the rear of the aircraft, no matter what orientation the aircraft is in.

          Try it yourself with a bucket half full of water on a string. Swing it around your head. The water is being pressed into the bucket through centrifugal force, basically an accelerative force trying to push the water out of the bottom of the bucket. The bucket thinks "down" is straight up when it's above your head, so long as you keep that acceleration going.

          More than one pilot has died in a crash due to instrument failure in bad weather, because a human's built-in, gravity-derived senses cannot accurately tell where "down" is, and the pilot might well flop an aircraft upside down into a lake, believing themselves to be in level flight right up until the last moment.

          1. Vladimir Plouzhnikov

            Re: Re: Re: Re: How about

            Well, I know the basics of Newtonian physics. If you draw vectors of forces acting on the counterweight for different points in the trajectory you will see that it might just work, provided the thrust/weight ratio is high enough and the machine is not pulling more than, say, 2 Gs while turning. It will overshoot the vertical, the canard deflection will reduce, which will reduce the turning Gs, which will let the canards deflect into pitch-down and the whole thing will oscillate in this way around the vertical and, I believe, the oscillations will decay.

            P.S. All aircraft have slip ball indicators which are purely gravity (acceleration) based. :-)

            1. Vic

              Re: Re: Re: Re: Re: How about

              > P.S. All aircraft have slip ball indicators which are purely gravity (acceleration) based. :-)

              They're acceleration-based, not gravity-based except during level flight.

              In a turn, the ball doesn't point down...


              1. Vladimir Plouzhnikov


                Isn't that what I said?

                1. Vic

                  Re: @Vic

                  > Isn't that what I said?

                  I don't think so. You said they were "purely gravity (acceleration) based.". But they're not gravity-based...


                  1. Vladimir Plouzhnikov

                    Re: Re: @Vic

                    Let's not split the hairs here we both know we are talking about the same thing.

                    The ball senses total acceleration which includes free-fall acceleration due to gravity and which consists solely of free-fall acceleration in a straight and level flight. That's what I meant.

                    I also meant it to stress that the ball is an instrument which relies only on gravity (and acceleration) and not on any gyroscopic or magnetic forces, pressures or external references (radio or optical).

                    1. M Gale

                      Re: Re: Re: @Vic

                      That slip ball is there to measure acceleration forces, so therefore uses acceleration. It still doesn't know where "down" is, which is what anything connected to a control surface, robot or human, needs to know if it doesn't want to become a lawn dart.

                      That's why aircraft have artificial horizons kept in place with gyroscopes and other funkiness. If you don't know your orientation, you can't fly.

                      Besides which, LOHAN will have some kind of readily available autopilot on board anyway. That's if Lester doesn't just want to use a really long string and a slight angle from the vertical, which seems to be the KISS option.

  56. TRT Silver badge

    Couldn't you get payload higher still by carrying a second stage, under-inflated balloon? By the time the main lifting balloon bursts due to its size, the second stage balloon will have inflated. Sure, it'll be able to carry less mass, but with a bit of careful design, it might work. Any views anyone?

  57. Chris Glen-smith

    Why have verticle launch?

    Other than for the beautifull symboligy of thrusting between the magnificent orbs of course.

    Launch enough above horizontal to avoid losing height then have the autopilot convert to verticle.

    The idea of using the truss as a launch rail sounds good to me.

    1. Stoneshop Silver badge

      Re: Why have verticle launch?

      Because there's very little air for control surfaces to be even a little bit effective (so an attitude change should be achieved with a gimbaled exhaust), and the burn time of the rocket motor is not that long (so there's little time to achieve the change of direction, and you're wasting propulsion in a direction you don't want it)

  58. Reg J Mitchell

    Bent truss

    Similar to the T shaped truss idea, how about a V shaped truss. With all the weight at the bottom of the V it should be adequately stable with two similarly inflated balloons.

    More elegant would be a curved truss. A half circle or parabola would add a smile to the contraption (see icon!).

  59. Kieran Marsh


    Why not put a dihedral angle on the girder?

    Put your launch pad in the centre and the balloons a either end, the dihedral will tend to stabilise it, some damping would likely be necessary to prevent oscillation.

  60. pwibble

    Neat Triangular Truss

    Tricky problem - the essence of it boils down to the following:

    How do you get the launch platform to stay in the required geometry relative to the balloon(s) with 100mph winds blowing it all about?

    I like the idea of just using a very long cord between the balloon and the platform. Simple, effective. Low chance that the Vulture2 will hit the balloon, so this must be part of the solution. My guess is that 50m will be enough, but you guys can do the maths on this.

    Another aspect is that some kind of control electronics will be needed to assess the launch angle and only fire when the Vulture really is vertical - or exactly 10 degrees off vertical to avoid hitting the balloon. Tricky, but sounds possible to solve. I think if you don't do this then it could go off at almost any angle due to winds.

    The single straight truss doesn't look good to me. I like the construction concept, but I would go for a triangle with the three corners connected to a single balloon. Again, it gives more chance of clearance on launch because the Vulture will not be exacly underneath the balloon(s). Should be fairly easy to get the triangle in balance by positioning the cameras and Vulture 2 itself.

    So - the solution(!).... triangular launch platform (similar to current design, but three trusses linked together). Connect the corners of the triangle to a balloon (or balloons) on a long cable. Launch when Vulture2 is just off vertical. Should work :-)

  61. drben

    Single balloon, vertical beam?

    Didn't spot this mentioned anywhere above...

    Single balloon seems to me to be unavoidable, so put this with a long cable, as suggested, and suspend the beam vertically - i.e. from one end only.

    The rocket could have a nice long launch rail (to give you some confidence that it'll go where it's pointed), starting from the bottom and just missing the cameras at the top, at whatever angle you see fit.

    (PS @Equalise pressure?: Glad someone is awake!)

  62. S 11

    Can I buy your Magic Truss

    Every day I get in the queue (Too much, the Magic Truss)

    To get on the Truss that takes me to you (Too much, the Magic Truss)

    I'm so nervous, I just sit and smile (Too much, the Magic Truss)

    Your house is only another mile (Too much, the Magic Truss)

    Thank you, driver, for gettin' me here (Too much, the Magic Truss)

    You'll be an inspector, have no fear (Too much, the Magic Truss)

    I don't want to cause a fuss (Too much, the Magic Truss)

    Can I buy your Magic Truss? (Too much, the Magic Truss)

    Rock on Vulture.

  63. pwibble

    drben is Spot On

    Dr Ben,

    Sounds like a plan. Simple, efficient, beautiful. Like you say...just suspend the truss down from the balloon(s) and the truss inherently becomes the launch rails. Like it. Forget all that messing about with triangles I was ranting about.

    Slight challenge in terms of how to miss the balloon, but on the other hand as long as the cable between the truss and the balloon is long, should not be a problem. I mean, it will be difficult / impossible to get Vulture2 to really go exacly vertical anyway. And the launch rails can just have a slight incline at the end to push the rocket slightly to the side.

    Simple, less is more - this is the way to go. And you don't even need to change the parts you already built really. Brilliant.

  64. Schultz Silver badge

    "... the Vulture 2 launch trajectory, which needs to be as vertical as possible without any risk of the aircraft hitting the balloon."

    Don't worry about hitting the balloon, just make sure the launch has the necessary punch to pop the balloon. I want to see the video of that! Maybe add some explosive charge (type 'potato cannon') to get some rapid velocity .

    More seriously, you should bend the truss (inverted U), so it'll be in a stable position during launch.

  65. Acadene
    Black Helicopters

    Lohan's thrust may snap the member

    Just thinking thay you guys should test the bending moment and shear force of Lohan on the carbon fibre truss as she fires up. Even though carbon fibre rods are extremely flexible and strong, they don't react kindly to sudden shear forces - causing the truss to fail.

    1. M Gale

      Re: Lohan's thrust may snap the member

      So long as LOHAN has left the platform, who cares what happens? If the whole thing comes down on parachute looking like it just picked a fight with a polar bear, that's just awesome footage!

  66. Magnus_Pym

    Spinning control

    It seems to me that in order to control the spin there must be air moving over a control surface. In order for that to happen the device must be moving relative to the air around it. In other words some sort of motive power is required. Would it add too much weight to have a solar panel/electric motor/propeller combo on one end of the truss and a large rudder on the other? The motor could kick in at the upper altitudes to stabilize the rig before launch.

    I also add my vote to the design where a single string hangs down from the lifting force to a single central swivel. From the swivel two strings support the truss , one at each end. One of these string s is shorter than the other in order to set the whole truss at the required angle for launch. The rocket can be slung underneath on a short launch rail parallel to the truss. i.e. pointing upwards at the required launch angle.

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