back to article LOHAN to straddle meaty titanium rod

After much head-scratching, and a good number of beermat sketches, we're finally ready to unveil our concept for the Low Orbit Helium Assisted Navigator (LOHAN) Vulture 2 launch platform. Click here for a bigger version of the LOHAN graphic To recap, we've been pondering just how to attach our spaceplane to the carbon-fibre …

COMMENTS

This topic is closed for new posts.
  1. Anonymous Coward
    Anonymous Coward

    The Vulture 2 will simply slide off the rod

    Yes because two objects in free fall always repel each other.. its that well known scientific principle of illogicum.

    (PS parachutes and drogues have negligible effect until the atmosphere thickens up)

    1. Bill Neal
      Thumb Up

      Re: The Vulture 2 will simply slide off the rod

      Agreed. I see no need to counter-balance the electronics package. Love the design though! seems solid enough

  2. Pen-y-gors

    I am not an engineer...

    Will there be any effect on the position of the launch platform from the force of the exhaust hitting the plate behind it? Will it not make the support spin/tilt?

    1. Arrrggghh-otron

      Re: I am not an engineer...

      I was wondering that, and was considering the use of ducting to capture and direct some of the exhaust gas to act as stabilizing thrusters for the truss when I realised the idea was probably unnecessarily complex plus it's a Friday afternoon and I just couldn't be bothered with that thinking malarkey that is reserved the less fun parts of the week

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

        Re: Re: I am not an engineer...

        Agreed. Get back to me on your plan when you're feeling less fun-filled.

    2. Graham Bartlett

      Re: I am not an engineer...

      My worry about that isn't the force of the exhaust, it's the heat. For a short time, there's going to be a lot of flame coming out of the back of the rocket, bouncing off that plate and coming back at LOHAN. Drilling a hole in the plate for the flames to go through, or better yet just resting LOHAN on the back of the fuselage instead of covering the rocket exhaust, would seem like a good idea.

      1. Bill Neal
        Go

        Re: I am not an engineer...

        It seems there is only one way to resolve that question: a low altitude test launch/flight. It won't really matter until we know what mass the Vulture 2 will actually have in its final form. I would think some back pressure from the plate is a good idea to help push the whole rig out of the way.

  3. NoneSuch Silver badge
    Happy

    Looks like a solid design to me.

    Good luck with your skirt lifting thruster.

  4. TRT Silver badge

    I doubt that LOHAN would slide free of the truss by gravity, as the greater air resistance of the glider would cause it to be snatched free of the truss by the wind.

  5. Pete 2 Silver badge

    Premature ejection

    > The Vulture 2 will simply slide off the rod, its weight breaking the rocket ignitor wires (not shown in pic), and it can then fly back to base.

    Presumably if the igniter wires are broken in the situation described, that would boot up the electronics in Vulture 2, to that it's glide could be documented and its radio beacon used to find where it ends up.

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

      Re: Premature ejection

      Yes - the idea is that Vulture 2's guidance and tracking are active whether motor fires or not. That way, the mission's not a complete write-off if the balloon pops too soon.

      1. Anonymous Coward
        Anonymous Coward

        Re: Premature ejection

        If the weight of the craft is enough to break the ignitor wires then a good gust of wind would also be capable of the same and lifting it off the rod. I liked the idea of securing it with fishing line behind the motor which should melt on ignition but then again may crack at low temperature. Also I think you're putting too much faith in the truss remaining at the same attitude for the ascent, at times it might be tipped down.

        Whatever, I think relying on the ignitor wires is dodgy and the tethering needs more thought. It may be better to have a properly secured craft and a parachute descent so the craft lives to fly another day than half a flight.

        I'd also put some padded struts almost touching the wings to minimise roll during the ascent so if a violent gust catches a wing it doesn't slam into the truss causing a snapped wing.

  6. melt

    Looks spot-on to me. Perhaps provide a hole in the back plate for the motor to thrust through so the truss isn't affected by the takeoff?

  7. Anonymous Coward
    Anonymous Coward

    Two comments

    1) Why not keep the launch rail short and combine with a tethering system that is released on ignition; my own suggestion is based on pinholes at opposite sides of the exhaust tube and a loop of fishing line through these to tether the rocket. The line will be destroyed when the engine ignites, releasing the rocket to slide along the rail.

    2) Use a tension sensor (probably a DIY job) on the line holding the balloon to detect when the line goes slack; combine with a timer so that when the line goes slack for a suitable period (5 seconds?) the launch is triggered.

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

      Re: Two comments

      Interesting, but we're just trying to keep the thing as simple as possible, and without any sort of release mechanism at all.

      1. Anonymous Coward
        Anonymous Coward

        Re: Two comments

        OK, but my point 1) still stands. I think that a positive retention system will be better than relying on things always being the right way up.

        I'm also not sure whether, in free fall, the glider will slide free of the truss. To ensure this you need to retard the descent of the truss and ensure the correct attitude; with a drogue 'chute maybe (but I note earlier concerns about air density on this).

        1. Stoneshop

          @AC 14:44 Re: Two comments

          Drogue chute: it does not really matter if LOHAN slides off the rod immediately after the rubber bursting, only that she does so that they don't hit the ground together. So at what height the chute really comes into play is of little concern.

          Alternatively, simply firing the motor on loss of lift, no matter at what altitude, will ensure that LOHAN is at maximum height anyway, while alsosolving the separation problem.

    2. Roger Varley

      Re: Two comments

      Why would you need to monitor the tension on the balloon anchor line? Surely it would be enough to detect that upward motion has translated into downward motion?

      1. Anonymous Coward
        Anonymous Coward

        Re: Two comments

        Detecting the difference between upward and downward motion isn't always easy (look at what happened to Air France 447).

        Detecting when a line has tension or not is much simpler.

        1. Pete 2 Silver badge

          Icing on the cake

          > Air France 447

          Now that brings up the very real question of how to deal with ice forming on the launch rod, to the extent where it blocks the free running of V2. (Or weighs-down the whole kaboodle and makes it un-aerodynamic)

          I guess the pragmatic answer is to launch on a clear day, so the ascent is not through cloud: no matter how high/thin it may seem to be

  8. Adrian Challinor
    Thumb Up

    Let it swing

    When it comes to launch, the truss assembly will be swaying, and potentially rotating. Will this have an impact on the angle of attack when the rocket fires?

    It appears that Lohan will be resting against the sacrificial rubber pad during ascent. Is there any danger she will freeze to the rubber?

  9. dpb
    Thumb Up

    titanium rod mount

    The mount between the titanium rod and the aluminium plate will have to be pretty impressive to maintain the parallel line - you'll probably need a second point a bit back behind that plate.

    Other than that looks good to me.

    1. cliveski
      Alert

      Re: titanium rod mount

      Also, have you considered the relative thermal contraction rates of aluminium and titanium? Depending on how you attach the two this could have some effect on the integrity of the joint.

      Also, making the Teflon inserts of a considerably larger diameter than the titanium rod will reduce the resistance between the two (smaller surface area in contact).

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

        Re: Re: titanium rod mount

        Yup, we'll do some tests to make sure low temps don't cause a problem. Agreed about the Teflon diameter.

    2. The Axe

      Re: titanium rod mount

      It won't be parallel, the rod will be at 90 degrees to the plate.

  10. Paul_Murphy

    gyro?

    Would a gyroscope on the truss stop it from spinning, or at least control it a bit?

    It would be good to take some video of the departure of LOHAN from the truss - maybe a prism mounted to see above the rail?

    You _could_ mount LOHAN like a PIAT round, ie with a great big spring. That way even if the rocket doesn't fire you can get a launch.

    ttfn

  11. Sonny Winston

    Swingers Delight

    Is there any chance that the swinging motion will be violent at any point in the ascent? If freezing is deemed not to be a problem with materials used, would a two rod option provide mitigation against any unwanted swinger related damage?

    The deisgn is very elegant, top work. Although I do have zero experience in this field, apart from the fact I always wanted to build a rocket.

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

      Re: Swingers Delight

      I don't think the swinging will be violent - the whole thing goes with the wind, however fast that is.

      1. Anonymous Coward
        Anonymous Coward

        Re: Swingers Delight

        >the whole thing goes with the wind, however fast that is.

        Respectfully I disagree. The large surface area of the wing and the open truss will most likely not move together. You need a wind tunnel to see what might happen.

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

          Re: Re: Swingers Delight

          Fair enough. We'll do a wind tunnel test.

        2. Stoneshop

          @Chris W: Re: Swingers Delight

          I suggest you watch the video in this article: http://www.theregister.co.uk/2012/03/06/lego_shuttle/

          The launch day weather doesn't appear to be very clement, and still the swaying and turning doesn't show a level that would upset the LOHAN/truss combo.

      2. ian 22

        Re: Swingers Delight

        Kitchen utensil aside, I've no experience with Teflon. Will water ice adhere to Teflon? If not, a rail should be superior to a rod, eliminating potential wing-truss contact.

        1. Bill Neal

          Re: Swingers Delight

          Frost will form on teflon, but fall off at the slightest touch. A rocket should have no problem without serious icing. I don't see how you could prevent the same icing from forming on a rail.

  12. Markus Imhof

    Why titanium rod?

    Ok, it's sexy and allows for a few cheap puns.

    But wouldn't a tube serve the same purpose, at perhaps a quarter of the weight? And if it becomes a tube, are there any reasons against using a carbon fiber tube? Since you already have your low temperature test facility, dropping a piece of CF tube in there (in similar proximity to the exhaust as in the final launch setup) probably wouldn't be too much of a problem.

    1. Monkey Bob

      Re: Why titanium rod?

      If you used a tube could you fill it with whatever is in those chemical hand-warmer thingies, just before launching, & at that altitude would it do enough/anything to stop freezing?

      Ignore me if I'm talking shit, it's already beer 'o' clock round these here parts & I know nothing.

  13. Anonymous Coward
    Anonymous Coward

    Rod vs Rail

    Have you considered a C shaped teflon thing with the gap at the top instead of a ring shape?

    Then use a strip attached all the way along to a rod inside the C as the rail. This allows more attachment points to the truss to keep the rail straight. So, in pictures... C with a o-| rail inside it, all rotated left by 90 degrees.

    Now lets hope that doesn't get translated into some kind of smiley when I hit post.

    1. SImon Hobson Bronze badge

      Re: Rod vs Rail

      You mean ... like a lot of curtain tracks ?

    2. Stoneshop

      Re: Rod vs Rail

      Unneccessarily complex. Since the whole enchilada, truss and all, is hanging from a tether, you can't guarantee a specific direction and angle anyway, and the main function of the guide rod/tube/rail is to give LOHAN some sense of direction: more or less parallel to the truss, and especially not slamming into the underside of same. There is a minor thrust component forcing LOHAN nose-up, and to counter that a sufficiently stiff tube/rod looks to me to be quite adequate already. This allows simple attachment/guidance rings, and simple means the highest probability that there's separation at the right moment.

  14. John from the USA
    Alert

    That and don't bang the tail off

    I share the concerns regarding the "simple" dropping of LOHAN in the event of premature balloon rupture. I seriously doubt that the spaceplane would simply slide off the rail. I'll grant that it /might/, but more likely in my mind it will fall at about the same rate as everything else regardless of the orientation, only separating when it falls into thicker atmosphere and the truss assembly is slowed by the recovery system. What damage might the spaceplane suffer in the interim, and what affect would that have on the "flight altitude" record?

    The problem of motor exhaust changing the relative orientation of the truss is all but certain. The questions are how much and how important. The issue that I see is that it will cause the launch rail angle to decrease relative to the horizon and so you will lose some ultimate altitude. How much is the question. This can and should be tested for on the ground. Understanding how the platform will behave at the time of launch is important since it will determine the orientation of the spaceplane when it leaves the launch rod.

    Finally, I'm concerned that if sufficient winds and/or turbulence are incountered during the ascent, the spaceplane could be damaged by impact with the truss as it swings back and forth on the rail. This may or may not be easy to prevent depending on how far below the truss you can reliably mount the rod (insert appropriate LOHAN joke here). If the rod can be placed slightly more than 1/2 wingspan below the truss, LOHAN can swing any way she wants and not hit anything (potential future application in NAOMI project?). A slightly more complex alternative would be to build a cradle that the space plane would rest in and then slip out of during launch. The cradle would prevent LOHAN from swaying until the motor ignites.

    Great work lads, have a beer.

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

      Re: That and don't bang the tail off

      I need to clarify here - the truss comes down by parachute, so when that deploys the Vulture 2 should drop off the rod. That's the idea, anyway.

  15. Phil O'Sophical Silver badge
    Thumb Up

    alu plate/sacrificial pad?

    Isn't there a risk of that diverting rocket blast/debris to places you don't want? Why not just put a clamp on the titanium rod, so that the rearmost sliding mount rests on it? Then the nozzle has a clear line of fire.

    I am disappointed that there are no exploding bolts in this. I always wanted to build something with them.

    1. Zoniad

      Re: alu plate/sacrificial pad?

      Agree with the lack of need of the allu plate - that way you don't risk melting the structure of Vulture 2 with the any exhaust reflecting off the plate as well as not risking melting a plate? Plus you then remove mass from the end you want to be lighter in case of a downward slide launch...

      Is there some possibility that the v-tail could become entangled in the truss, if it rotates about the the rod? A possible way round this would be to have a predator drone style v-tail (upside down)...

  16. Anonymous Coward
    Boffin

    Backronym?

    You are obviously going to need one for this device. May I suggest:

    Titanium

    Assisted

    Direction-

    Guiding

    Exoatmospheric

    Release

    I therefore hope we can look forward seeing LOHAN riding into space astride a well lubed-up TADGER.

    1. TRT Silver badge

      Just call it what is is...

      A rigid shaft.

      If it's backronyms you want. It's a LOHAN Titanium Aerial Release Device.

  17. TeeCee Gold badge

    Tail.

    "For obvious reasons, the Vulture 2 must have a "V" tail elevon configuration."

    Nothing obvious there and no need for the dihedral tail. I'd have thought a conventional horizontal stabiliser / elevator configuration with a fin / rudder at each end would be simpler and more practical. Have a look at an Avro Lancaster for a practical implementation. You still have to tie the two rudders together (assuming rudder control to be a requirement at all), but you don't have to get into the horror of managing the synchronisation of the two "rudderators" independantly to produce the desired turn / pitch movements.

    Pedantry bit: An "elevon" is something found on a "tailless" aircraft (usually delta wing designs), being a combination of the elevator, for pitch control and the aileron, for roll control. Your design combines the rudder, for yaw control and elevator as mentioned. I've used "rudderator", there's probably a proper word for this..........

    1. Steve Hersey

      Elevons are not such a problem...

      We RC modelers operate V-tail configurations routinely. There are simple mechanical and simpler electronic methods for making this work well, so it's not really an issue. Most mid-range RC transmitters do elevon mixing, and an on-board controller could certainly do that as well.

    2. GBE

      Re: Tail.

      No need for either a V tail or a double fin. Just put a standard single-fin on the bottom.

      1. Martin Budden Silver badge
        Thumb Up

        Re: Tail.

        That's exactly what I came here to say. The only reason planes have their tails on the top is so the tail doesn't bump the runway. In this case there is no runway, so the tail can go underneath. K.I.S.S.

    3. John from the USA
      Boffin

      Re: Tail.

      The proper word is "Ruddervator", with a "v". It rolls of the tongue a bit more easily than rudderator.

  18. Anonymous Custard
    Thumb Up

    Secondary balloon line?

    Could some sort of second line be used, linked to the balloon and a tension-sensor (but not linked to the truss)? My thinking would be that if the balloon prematurely pops, that second line going slack would be sensed and that could be used as an "emergency" trigger for the rocket motor?

    Similar to the idea above, but by using a second line it can be thinner/lighter and not get in the way of the main line that the balloon is using to hold everything up.

  19. Sacha TF Padovani
    Boffin

    on the rod, again

    Just a few thoughts .. I know the guiding rod is a simpler setup, but I agree with the thermal expansion argument between titanium and alluminium alloy. I was also thinking of some sort of electrical antiicing device you counld use to avoid ice on the rod (thermally shielded common battery + big enough resistor attached to the rod?).

    OR, if you're willing to accept another suggestion, why not copy all air-launch systems on aircraft, and build a mechanically severable connection to the truss (...spring loaded blades in a thermally protected box?) and just -drop- V2? After drop, timer (thin cable?) ignites rocket, and off she goes. You'd have the advantage of not having the backplate/rod. BUT you should have a good idea of how V2 performs aerodinamically during the drop (tail first...), but since you'll be going in wind tunnel at Soton... After all, if a B52 can aerolaunch a pegasus rocket .. http://en.wikipedia.org/wiki/Pegasus_%28rocket%29

  20. Sacha TF Padovani

    On temperatures, again

    Sorry, forgot. Felix Baumgartner just jumped off a balloon today at 21 kms altitude, and reported he "could hardly move his hands" at -75°C. Dump the heated rod idea... too much power required.

  21. Robert Moore
    Go

    Simplify, simplify, simplify.

    Why not trigger the launch when the balloon breaks.

    It seems simple to me. Have a switch as the connection point to the balloon, when the balloon breaks, a spring flips the switch to the on position, and the rocket fires.

    Simple toggle switch, with a hole drilled through the toggle.

    Connect the balloon to the toggle.

    Spring pressing down on toggle.

    Tension from balloon holds the switch in the off position.

  22. Charles E

    Tail configuration, etc.

    I was surprised at this:

    >For obvious reasons, the Vulture 2 must have a "V" tail elevon configuration..

    No, actually it doesn't. The little tubes that guide the rocket down the rail can go on the bottom of the rocket, so the tail fins are facing away from the rail and truss.

    Another note: I would not attach the lines to the truss at only two points, top and bottom. This will allow the truss to rotate or wobble around the axis of the top rail. Make a two point harness at the top, and another at the bottom, like a kite bridle. This will prevent the truss from swinging. I would actually invert the truss and put the apex of the triangle pointing down, next to the launch rail. This will allow you to put the attachment points on the four corners of a flat face of the truss, which is facing up, for more stability.

    Some people have commented that the rocket could slip off the rail if it accidentally pointed down. There's an easy solution, you put a stopper on the rod, above the guide tubes, that is sufficient to keep the rocket from slipping off, but not sufficient to resist the force of the engine. That's tricky because if you make it too strong, the rocket will not get off the rail.

    I also notice this new method of deploying the launch platform is exactly the same as the standard rockoon system that has been in use for over 50 years. I wondered how long it would take you to figure out that this was the best way to do it.

  23. Dyspeptic Curmudgeon

    Simpler Still

    Sorry to invite you back to the drawing board., but there IS a better way.

    Invert the truss (again!) and make the lowest rail (bottom apex) from a strip of delrin shaped as an inverted keyhole. The truss' structural rods are inserted into holes drilled in the top section of the strip. LOHAN rides along the bottom rounded section. The lower truss then carries out both truss and launcher duties.

    You do not need a separte alu plate nor a titanium rod. In the present design, the plate must support the entire load of the rod and LOHAN and hopefully keep them in alignment. Good luck with that.

    With a shaped delrin truss tube, the static load of the LOHAN is spread throughout the length of the truss since the delrin is structurally strong. Any torque loads induced by the launch of LOHAN are immediately transmitted into the truss, and the alignment of the LOHAN vis-a-vis the truss is retained. The titanium rod however can bend the plate mounting under load. You need only place a small bolt through the keyhole head to stop LOHAN from sliding off 'backwards.

    And delrin because it is light, strong, easly machined, has useful high-temperature characteristics (needs a couple of hundred degrees before it deforms), has basically a nil co-efficent of thermal expansion and has an incredibly low coefficient of friction. In friction terms, its more slippery than ice. And ice is not likely to form on it due to its low thermal conductivity. Only problem is that it IS hard to glue: you do need two part epoxy, but then you probably need that to glue the carbon tubes together anyway.

    Attempted ASCII art description of the shape of the delrin truss:

    _____

    \ /

    \ /

    (____)

    Well I hope you get the idea! A variant would be to use an upside down T shape which might be easier to construct. Some passes with a router if constructing from a bar shape, or small screws to fix the 'head' of the T onto the shaft if constructiing from sheet material.

  24. Tempest8008
    Go

    Handling characteristics

    The sintered design is going to include the rod guides?

    Or they are going to be add-ons to the sintered body?

    They just smack to me of "little bits that can break off".

    It seems to me that if you're dead set on the single rod, that a hole piercing the long axis of LOHAN (that the rod would fit through) would be more secure and not require specially added guides. It just means you'd have to jigger around with the payload, as the launch tube would be going right through where all the fun stuff will want to sit.

    Now, if the design of LOHAN is still somewhat open, why not let her take TWO shafts!

    Include ellipsoid holes through the wing structure that shafts penetrate, but sit relatively loosely in.

    Would prevent the craft torquing during the ascent phase, hold her steady during launch, not run the risk of freezing (as any motion of the aircraft would "rattle" the shafts in their mounts) and give the opportunity for more puns.

  25. Steve 48

    Bending rods

    As mentioned elsewhere, using a supported guide rod with C shaped bearings would ensure that the rod remains parallel to the truss, otherwise you may end up with the nose of the orbiter hitting the truss during ascent and take-off, unless you have some cunning method of coutering the bending moment of a long rod! A cheaper option to using titanium might be something from the DryLin range from Igus - it's available in all sorts of shapes and sizes & it has good low-temperature characteristics. You might even be able to blag some "samples" - they're usually pretty accomodating.

  26. County

    Launch Rail again

    OK - so I don't know much about any of the specifics here, but would this count as an alternative to the Teflon strips on the truss ?

    On the back plate, add a 2nd small 'rail', more of a peg really, along with a matching receptacle on V2 (so the back plate would look something like an F in cross-section, with the top of the F representing your launch rail).

    My thinking is that if your not expecting much rotation around the rail anyway, a small peg would remove that, and if the peg wouldn't take the strain, surely similar unrestrained rotation would damage the wings?

    Feel free to poke holes in this, as I'd be interested in knowing where the flaws are.

  27. SW

    'Elf and Safety

    If the launch fails and LOHAN returns to our mighty globe without firing the motor - how are you going to be certain of reaching her before some local yokel comes along and inadvertently/accidentally manages to fire it up whilst holding it?

  28. C. P. Cosgrove
    Thumb Up

    Rails and lugs and grooves

    Tempest8008 makes a valid point about "little bits that can break off" and the Dyspeptic Curmudgeon has an interesting suggestion about a continously mounted keyhole shaped launch rail.

    Where are you on airframe development ? I have just had a look at the library and failed to find any details on the likely shape of the airframe, although Southampton Uni are down to make it out of sintered nylon.

    If it is still in the design/thinking stage, then, if you could mold a groove along the bottom of the fuselage, you could mount it upside down on DC's rail and a groove molded into the structure would avoid T8008's concerns about bits breaking off. It would also have the advantage of doing away with the elevon design and allowing a more conventional vertical rudder and horizontal elevators. I accept that there may be aerodynamic consequences to a lengthwise groove, but so would there be to a couple of 'ears' sticking up.

    Chris Cosgrove

    1. Eddy Ito

      Re: Rails and lugs and grooves

      I've got to agree with the concept of using a rigid guide attached securely along the length of the truss. My concern stems from the fact that the rod, as shown, looks to me like half a tuning fork and the devil only knows what it'll do when she lights off. Another advantage of using a "T" or "V" shaped guide is that you can pick the materials such that the mating parts get looser as they get colder and you can even use tiny rollers if desired. On the plane design, the rear stabilizers could extend up to act as the aft guide and as there won't be any motion on the roll axis there won't be any need to worry about wing strikes against the truss. Since I've come to stabilizers, have you considered a canard design which would only require the vertical rear stabilizer perhaps on the wing tips like the Berkut 360?

  29. Andus McCoatover
    Windows

    The concept of the plane being angled at over 90 degs...

    seems ace! Nice few pints/beermats well spent/drunk.

  30. Cagey

    Suggestions

    Just some suggestions based upon two decades of launching model rockets.

    (1) The plate and guide rod assembly should be re-thought. When LOHAN's motor ignites the exhaust gases will impinge on the plate and "splash" in a 360 degree arc. The plate needs to extend forward 5 or 6 centimeters to prevent the exhaust gases from cutting the truss.

    (2) The rubber bumper also needs to be relocated. If the base of the LOHAN is sitting on the plate at ignition it could be burned and/or twisted around the rod by the exhaust gasses. Moving the rubber bumper out to the rod would prevent the exhaust having any affect on the vehicle.

    (3) I'm not sure that LOHAN would slide off the launch rod in the event of a balloon failure. If the remains of the balloon exert any drag on the truss it would probably not rotate downward enough to release the air frame. I'd suggest incorporating a device to initiate the launch sequence in the event of a balloon failure. This should allow the LOHAN to separate from the truss and be recovered normally.

    (4) Also why use a titanium guide rod? Aluminum rods and rails have been in use for many years when launching model rockets with no reported problems? Does the titanium have any benefits over the use of a polished aluminum rod?

    Kenneth G. Holloway

  31. Vladimir Plouzhnikov

    Rod and stuff

    Firstly, I think the rod and plate idea is the best. It works well for launches off the ground, no reason for it not to work off a balloon other than possibly icing.

    Secondly, if there are fears that the vehicle or truss (who cares about that one?) can be damaged by exhaust the plate can be made out of metal mesh, like the one you can buy in any Robert Dyas store (to cover frying pans). You can also stick a foil strip on the truss near the plate.

    I am not concerned at all about backblast melting the vehicle - it will not be back blast but rather side blast and will last for only a fraction of a second before the thrust gets big enough and the vehicle starts moving.

    However, I would recommend to pay some attention to the igniter assembly. If the vehicle is swinging free the wires may be torn off.

  32. Tim Bergel

    Would it be a good idea

    to have the launching rail extend somewhat past the end of the truss so that by the time LOHAN becomes free from the rail it is sure to be completely clear of the truss?

  33. dpb
    Terminator

    tail on the truss?

    To reduce potential spin of the truss as it is suspended under the balloon why not add a tail? It won't stop all the sipn, but might at least reduce it.

    I know nothing of aerodynamics etc, so this may be a silly idea. I'm sure others will tell me. Also the extra weight may be prohibitive, and I'm not even sure that there would be any spin problem. But hey.

This topic is closed for new posts.