back to article LOHAN spaceplane project starting to shape up nicely

We at the Special Projects Bureau have been mulling just how our Low Orbit Helium Assisted Navigator (LOHAN) project is going to work and, having looked at your suggestions and ideas, have put together our initial thoughts. Click here for a bigger version of the LOHAN graphic To recap, we're going to launch a rocket-powered …

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  1. /dev/me
    Paris Hilton

    Vulture Evolution; or how we went from 2D to 3D printer .. ehm .. output material?

    ""Structure formed from composite material (eg, carbon-fibre-reinforced polymer), or selective laser sintered nylon.""

    I don't understand how this is still a question?

    Vulture 1 (PARIS) was created from high quality (but 2D) printer paper, providing it with the necessary IT angle. It's only a natural step in the evolution of the Vulture project that #2 (LOHAN) is created by a 3D printer.

    Objections? No? Then it's agreed :D

  2. Pete 31

    Space planes

    I've got a Spitfire in the loft constructed from balsa wood covered with tissue paper which I made years ago at school if you want a prettier aircraft design (and a rocket powered spitfire in space would be cool)

    On a slightly more serious note, the instructions (it was a very old kit) mentioned the use of a Jetex rocket motor. These don't produce a lot of power but burn at lower temperatures which might be useful if building the model out of burnable materials. http://en.wikipedia.org/wiki/Jetex_engine

    1. Dr Gerard Bulger

      just a little hydrogen?

      Would not a Helium/hydrogen mix be safe? If the hydrogen is dilute enough would it not reduce the risk of a firestorm...but give more lift? Are there other lighter than air gasses that could act as retardants to be added if SOME hydrogen was in the balloon.....

    2. Anonymous Coward
      FAIL

      Major Fail

      Don't call it a space plane! The last attempt reached 17 miles, whereas the widely recognized edge of space is about 62 miles (100 km), so El Reg whilst they should be applauded for trying, are still 237,600 ft short of reaching space!!!

  3. Peter Simpson 1
    Thumb Up

    So the angle of the dangle is key

    How appropriate.

    // and a very happy Sysadmin Day to all the BOFHs out there.

  4. RayG
    WTF?

    Stability

    And are you absolutely certain that nose-mounted rockets aren't the old http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy in a new form?

    1. James Hughes 1

      Absolutely right

      This is a pendulum fallacy in the making. It simply won't work. Not even a new form - Arca in Romania were about to launch a very similar rocket when they seemed to read up on the Pendulum fallacy and changed their minds....

      1. Stoneshop Silver badge
        Boffin

        Absolutely not right

        LOHAN will be equipped with functional stabilisers, unlike the rockets described in the Wikipedia article. Of course, the trick is to get them to keep the craft at roughly 45 degrees nose-up during engine burn (I can't readily find burn time numbers, but it appears to be just a couple of seconds max for most sizes). As long as your sideways momentum is small relative to the total length of the craft, nothing much is going to happen in that time, and even if it did pitch down immediately, it's at some 25km altitude, still quite some time and distance away from becoming a lawn dart.

        1. Poor Coco
          Boffin

          Burn time

          With the configuration I have suggested — 2 stages of 6, Aerotech E15 composite engines each — the burn time will only be about 5 seconds total. But that should be enough to get a 3 kilogram plane up to hundreds of kilometres per hour.... if it doesn’t completely tumble.

          A nose gyroscope may be a good idea for initial stability.

      2. Anonymous Coward
        Anonymous Coward

        What about this bit from the Wiki page

        "Even a Goddard-type rocket, with the engine at the front, will fly correctly if fitted with fins or another means of control. "

    2. Poor Coco
      Boffin

      Pendulum fallacy

      That is actually a new one for me. However, there are important differences in my LOHAN design; I think this will compensate. It would also not be impossibly difficult to have the top of the tower be a universal joint with servos that can alter the net thrust angle and guide the rocket-plane on its desired path.

      The long nose tower holding the rockets a safe distance from the plane will shift the CG forward a fair bit — probably 20–30 centimetres, I’d estimate — which will convert the gliding configuration into a stable boost configuration. After engine burnout, wing deployment and tower separation, the glider will naturally adjust itself (eventually, given the extreme altitude) into gliding mode.

      1. RayG
        Go

        As the icon says: proceed with this nonsense at flank speed!

        Your design is definitely not as unstable as the classic pendulum rockets - the wings, and consequently having the centre of mass ahead of the centre of aerodynamic pressure (I doubt you could avoid that with this design even if you wanted to!) will make this stable once it gets going - so it might well be OK. The start is the tricky bit, combining low speed with thin air... I'm not sure I'm qualified to predict what would happen there but it sounds like a job for very conservative design if ever I heard one.

        Steering the whole engine unit, though, sounds problematic to me - will moving the entire engine mass relative to the entire fuselage mass be able to respond fast enough? Isn't this why big rockets usually rotate small subsidiary thrusters rather than the main engine?

        I'm really looking forward to this... whatever happens I'm sure it will be fun to watch!

        1. Poor Coco
          Boffin

          W00T!

          Thanks for the vote of confidence!

          We may be able to get quite effective attitude control if we combine slight directional rocket-pod adjustments with a super-fast gyroscope in the pod..... This may take servos capable of delivering a lot of force, so using longish lever-arms is advisable. The lever arm could, for example, extend 50cm down the rocket tower to the servos, which would be able to make small directional changes and control the craft.

          — Murray Pearson

  5. Gavin Jamie
    Headmaster

    GPS at altitude

    Apparently all GPS units that can work over 18km (which is pretty feasible) are classified as munitions. Have you got access to unrestricted GPS? (of course you know all of this I'm sure)

    http://www.armscontrol.org/documents/mtcr (item 11)

    1. RayG

      And or Or?

      Isn't it only if you're going over 1,000 knots, too? The statement in that document is "AND".

      Wouldn't be surprised if many chipsets use an "OR" limitation though, and the altitude information on civilian GPS does not work too well up there.

      Time to start packing gyros, accelerometers, barometers, and compasses?

    2. Anonymous Coward
      Anonymous Coward

      GPS limits

      If you want to get around the traditional speed & height limitations of GPS, you should speak to the chaps that helped you with your hypobaric experiments on project PARIS.

    3. Patrick O'Reilly

      Phone home?

      "Time to start packing gyros, accelerometers, barometers, and compasses?"

      Sounds a lot like you need a smartphone for guidance. Recently I've had the urge to build an inertial navigation system which uses GPS for the initial reference and is then supplemented by data from the accelerometer and gyroscope to work out it's position in 3D space.

      Plus it could double as a downlink once it's in GPRS range

      AND it could be used to film the Playmonaut's adventure.

  6. Richard 12 Silver badge

    Single-engined tractor config would be more reliable.

    Trying to ignite two or more engines simultaneously is asking for trouble - if one engine fails to ignite, ignites later or burns out earlier than the other then the craft is forced into a pretty disastrous spin.

    A single-engined tractor means that the craft needs to be a slightly odd shape, however that didn't trouble the X-Prize winners.

    Aside from that, two 'cockpits' looks pretty cool - one for the Playmonaut and batteries (ballast), the other for the camera and electronics.

    Incidentally, don't go with SLS nylon. It's really quite heavy and fragile compared to carbon fibre matting.

    You work with carbon fibre matting much the same way as fibreglass, it's really easy to form and extremely strong. Obviously you need to use the right resin, but that's a simple detail.

  7. Graham Bartlett

    Alternative to angle-of-dangle

    What's wrong with a long horizontal pole? Plane at one end, counterbalance at other end, balloon in the middle. The plane can then launch straight up without any extra faffing about. If you know what altitude you're going to release at, Boyle's Law will even tell you how big the balloon's going to be, and hence how long the pole needs to be.

    Of course you need to keep the pole horizontal, but simply having two support cables running from the balloon to each end of the pole will sort that.

    1. Poor Coco
      Boffin

      Problem with a long pole:

      Weight. To hold the craft steady far enough away to ensure clear passage past the enormous balloon (at altitude), the beam would have to be very long indeed — especially if the counterweight was substantially less than the aircraft weight, which I am estimating at about 2 kilograms (the wing by itself, without ballast, is 900 grams). Hoisting that much dead weight will surely limit altitude. Furthermore, with my aforementioned aimable thrust-pod, it will be a far smaller penalty to launch at 45° slope and use thrust-vectoring to attain a near-vertical trajectory after, say, 50 metres of flight.

      — Murray Pearson

    2. Michael H.F. Wilkinson

      or a donut-shaped balloon

      for a really weird-looking solution. The rocket could fire straight through the centre hole. You might even be able to get sponsored by any well-known maker of donuts..

      I know such a balloon will not be available off-the-shelf, but it would look cool.

  8. Chris Rowland

    title

    A few thoughts:

    Could the aircraft be suspended directly from the balloon with the suspension arranged to give the 45 deg launch angle? This would avoid the additional mass of a separate module attached to the balloon.

    I wonder if the release method could be by running the attachment cable through the rocket exhaust so that when the rocket is fired the cable is burnt through and the craft is released.

    The suggested multi rocket design seems to be vulnerable to problems if the rockets don't all start at the same time.

    Are folding wings neccessary? It's additional complexity and there aren't any narrow spaces it has to fit through.

    1. Eastander
      Holmes

      Doughnut - Shaped Balloon allows vertical take-off - Thunderbird 3 is go!

      If you had a large doughnut-with-a-hole shaped balloon, then the rocket could be mounted vertically and take off through the middle - like Thunderbird 3 does when it launches :-) Means you wouldn't need to bother with all the 45 degree stuff. You could wait until the balloon burst for max height, then a small drogue parachute at the top of the rocket could keep it's attitude vertical until the engines could ignite.

      1. jubtastic1

        You don't need a doughnut

        Three balloons will form a hole at the centre as they firm up at altitude, a small hole granted but possibly big enough to shoot LOHAN through.

  9. Anonymous Coward
    Anonymous Coward

    Folding wings

    Those folding wings look like they are designed to keep the wings out of the way of the rocket exhausts. surely an easier way is to just have the rockets above and below, not left and right.

    1. Poor Coco
      Boffin

      That's exactly what is going on...

      The thrustlines are 2D projections of diagonal thrust, which was my initial idea and is, frankly, probably not the optimal configuration. But, say, if we have a 6-engine cluster per stage, then we can have four engines firing above the wings at a shallow angle, and two engines pointing over the folded wings at a greater angle, such that the horizontal thrusts balance out.

      One detail that Lester did not mention is the toughening of the wings from covering the foam with 1/64" (0.4mm) aircraft-grade plywood and heatproofing with a layer of aluminum foil, shiny side out.

      My concept was using two, 6-engine cluster stages with Aerotech E15 engines (http://www.jetboyrockets.com/motor/detail/23/) which have a relatively steady and long burn (2.6 sec, average thrust 15N, max 28N per engine) along with the specific impulse oomph of ammonium perchlorate composite propellant, and the advantage of having reloadable cartridges.

      — Murray Pearson

  10. Marcus Aurelius
    Devil

    Hindenburg

    IIRC, it wasn't the hydrogen so much as the flammable skin and other materials which made the aircraft crispy. Hydrogen burns and goes upwards rapidly

    Incidentally the biggest airship disaster wasn't the Hindenburg; it was the Akron, a helium filled vessel....

  11. TeeCee Gold badge
    Coat

    Tractor rockets?

    I have one major objection to this. It removes the need to shove a rocket up LOHAN's arse.

    Round here, that should be a showstopper.

  12. Matthew Smith

    Hydrogen vs Helium

    Just wondering, its much easier to make your own hydrogen than buy helium. Would this give extra lift, does anyone know?

    1. Stoneshop Silver badge
      Flame

      It's been stated before

      that due to the incompatibilities between hydrogen and several of SPB's members lifestyle, it's a no-go.

      1. Anonymous Coward
        Anonymous Coward

        Re: It's been stated before

        They need the helium for their funny voices?

    2. Nigel 11
      Boffin

      Hydrogen lift

      Slightly better than Helium. H2 molecular weight = 2 (plus a smidgeon for the Deuterium). He molecular / atomic weight 4 (less a smidgeon for the Helium-3). Air average molecular weight about 29. So 2/29 extra lift.

      I still think that a smallish rubber or polymer balloon filled with hydrogen in an open outdoors location is safe. Extreme incompetence or a lightning strike would result in a fire burning upwards, ie away from the people. Just put a small exclusion zone around the balloon during the initial fill (until it's bouyant enough to be tethered a fair number of feet above any human heads). Or get it to no-load bouyancy with Helium, float it upwards, switch the fill to Hydrogen.

      1. Richard 12 Silver badge
        Flame

        Helium is dead easy to buy and transport.

        Hydrogen less so - if nothing else, the insurance people don't appear to like it when you carry significant quantities of compressed flammable gases around.

        It's generally considered a bad thing if your hire car catches fire or explodes.

        1. Nigel 11

          Use acidified water, and a battery

          You can make Hydrogen as needed, by electrolysis of water (and throw the Oxygen away into the atmosphere). Don't store the stuff (apart from in the balloon).

          Outdoors, with any breeze, this is safe. There's nowhere for any leaking hydrogen to accumulate and mix with air to an explosive concentration. Indoors, this is a recipe for an explosion.

  13. Caffeineated

    Alternative to underslung rocket?

    It sounds like the plane itself will be light compared to the payload module, so would it be possible, instead of mounting it under the balloon, to mount it directly above it? The payload module would act as ballast to keep the whole structure stable during the assent, and LOHAN could then blast vertically.

    1. Stoneshop Silver badge
      Boffin

      @caffeinated

      The balloon is not a rigid platform. Furthermore, it's quite fragile, so putting anything on top of it *) will, providing it stays put in the first place, induce stresses that will cause the balloon to stop being one prematurely.

      *) this advice provided free of charge by a card-carrying member of the Society for Putting Things on top of Other Things.

  14. jonathan keith Silver badge

    Rocket

    Can the solid fuel rocket motor be detachable, like the Shuttle boosters? Then you can have LOHAN sitting on (or hanging under) the motor which drops away when spent, leaving LOHAN lighter and better able to glide?

    Possibly also avoids the issues of bits of LOHAN exposed to the rocket exhaust too.

    1. Poor Coco
      Boffin

      The rocket tower does jettison.

      See the diagram? The top plan view shows the glide configuration, the other plan views show the tower in place with unfolded and folded wings.

  15. Stoneshop Silver badge
    Boffin

    Multiple balloons

    With one balloon providing the main lifting force, and a cluster of three partially-inflated smaller balloons you could trigger on the main balloon bursting (IMO the best and simplest way to signal that maximum altitude has been reached) while still keeping the tether taut after bursting and thus the launch platform at the predetermined attitude.

  16. James Hughes 1

    Three balloons

    Plus a long cardboard (?) launch tube that goes up the middle gap between the three balloons, Vertical launch, avoid the balloons, and you have three for more lift.

    As to GPS and the like, check out the arocket archives - lots of stuff on rocket suitable GPS there. Generally you lose tracking at over 1000knt, but recover it pretty quick once speed decreases. Also lots of posts on rockoons etc.

    1. Poor Coco
      Boffin

      Problem with a launch tube....

      Where would the wings go? If there are slots wide enough to pass the glider wings, how would the tube be held together?

      1. Anonymous Coward
        Anonymous Coward

        Launch rail?

        The rocket could just go straight up a rail betwen the 3 balloons.

        1. Poor Coco
          Boffin

          Hmmmm

          I was going to point out the weight of a rigid launch rail, but in fact that might be a really good idea — provided the rail is made from extremely light materials, such as a basswood/thin plywood truss.

          A metal rail of sufficient thickness would be ludicrously heavy, but a carefully-made wooden launch rail / balloon-separating apparatus could be just what the doctor ordered.

          Hi-ho, I am gonna fire up my crappy CAD software tonight, and send Lester another file.

          — Murray Pearson

  17. Stoneshop Silver badge

    Conical rocket motor assembly

    Would an alternative (to get around the need for synchronous, reliable ignition of multiple motors) be a single large motor with a titanium cone sitting behind the exhaust?

    1. Poor Coco
      Boffin

      Nope...

      ...because the drag of the thrust on the titanium cone would essentially equal the motor’s thrust. It would be spectacularly inefficient.

      Besides, it’s really not too hard to get simultaneous ignition. In my test rig over the weekend — which was my first ever attempt at a cluster rocket — I achieved ignition of three engines with nothing more than a 6V lantern battery and parallel-wired Estes ignitors. Of course, for weight reasons you don’t want to use that for LOHAN, but a stack of supercapacitors kept charged up with lightweight high-tech batteries can source a spectacular jolt of current for a brief time, enough to get 6 engines going with no problem, and not weighing too much either.

      — Murray Pearson

  18. M Gale

    Diameter problem

    Launch near-horizontally. Have your guidance system point the nose up at 45 degrees as of say, 0.5 to 1 seconds after ignition and hold it there for the duration of the rocket burn. Then you can use as many balloons as you like!

    The tractor design seems a bit iffy. Nothing wrong with a little bizarreness, but this is going to mean that you have burning hot exhaust gasses flowing over your aircraft. Not to mention the Wikipedia link on pendulum rocketry that RayG posted! Don't forget that the tractor escape system on various NASA rocketry has never been put to use, and they probably have a much bigger budget to make sure it would work properly! If you're worried about getting up to a speed where control surfaces will work, then can't you put, say, a "sacrificial" flap or two in the rocket stream? Doesn't matter too much if they burn up, so long as they last long enough to get you going in the right direction. That or make the rocket nozzles directable.

    I still think balloon clusters would be an idea. You don't just have one cluster with all the balloons touching. The idea is that if an entire cluster does go bang, you still have redundant clusters. Have a heavily inflated lower set, a normally-inflated middle set and an upper set only just inflated enough that they will lift the rig on their own. You get the ballocket through all that turbulent weather nice and nippy-quick, plus footage from an upward-pointing camera of the staged balloon bursts would be pretty awesome. Plus the rig will most likely go higher, as the upper set only needs to just-about-barely carry the weight of everything. I would also think it pretty obvious that a cluster of three balloons needs to be inflated vastly less than a single balloon, and therefore will go much higher before burst.

    Off the shelf rocket motors also tend to have an ejection charge in the tip, and I don't know what that would mean with them mounted in a tractor config like that. It seems like you'd need your own extra method of removing the tractor scaffold after the burn completes. Mounted to the side or underneath in a more normal fashion, you could use the ejection charges to blow your rocket modules clear in a Shuttle SRB style.

    The folding wing idea is something. Perhaps have a design where the force of the air sweeps the wings back like a fighter? You're going to need something to keep wing surface area to a minimum during the rocket burn, as otherwise you will more than likely rip both wings off (or at least, limit your potential maximum speed) even up at that rarified altitude. Don't worry too much about fitting ailerons to a moving wing. Elevons work extremely well for controlling both pitch and roll, and you reduce your servo count by two. A simple V Mixer (available from most model shops for about a tenner) can turn your aileron/elevator signals into elevon signals easily enough. Just like this, and yes, that is me: http://www.youtube.com/watch?v=0x2mbEVqJW4

    Finally, and I've already said this but it bears repeating: Cameras. Cameras and more cameras. On the launch rig. On the Vulture 2. Hell, on the rocket boosters too. Cameras everywhere!

    1. M Gale

      a-whups

      On looking about, it seems the Launch Escape System was used in an emergency precisely once. Have a look at these pics and tell me whether Vulture 2 should really have a tractor rocket system:

      http://en.wikipedia.org/wiki/Launch_Escape_System

      Might get a little toasty, no?

    2. Poor Coco
      Boffin

      Good post!

      I agree with the launch angle idea but, given the short duration of the burn — only about 5 seconds, even with a 12-engine 2-stage cluster — a 45° initial angle seems like a good idea, with the flight angle increasing to 75° or so while the engines burn in order to maximize altitude.

      The exhaust gases burning the foam is definitely an issue, which is why I suggest a skin of thin strong plywood (1/64" birch aircraft grade is available) coated with aluminum foil for thermal protection (shiny side out).

      Ejection charges can be nullified in a couple of ways. The simplest is just to apply a layer of epoxy over the forward end of the engine, which turns the ejection charge into a little blip of forward thrust. Another alternative is to have plugs in the engine holder tubes, so the ejection charges eject the engines (thus reducing the mass by throwing out the engine cases). But, given that the burn time for Aerotech E15s is 2.6 seconds and the delay periods available are 4 and 7 seconds, using E15-7s for stage 1 and E15-4s for stage 2 would mean near-simultaneous firing of all the ejection charges — which may be useful for ripping the booster tower off the plane (or completely apart) at apogee.

      I'm glad you like the folding wing. I initially considered an F-14 style swing wing but rejected it due to weight and complexity. The Skua 1500 (which this plan uses) does use elevons, and there should be no need for a V-mixer since the autopilot should be a µcontroller with servo-compatible PWM output available — the V-mixer can be in software.

      I totally agree with cameras galore. Having a camera on the rocket pod feeding data to flash memory on the plane until the moment of tower jettison would make an insanely cool video!

      — Murray Pearson

  19. Comedy of Errors

    Frozen controls

    One problem I forsee is frozen control surfaces. That means the rocket will go in circles and the plane stage will not operate until lower altitudes de-ice it - assuming it has not already broken by then pushing against a non-moving surface.

    I think you will have to do one of these:

    1) provide heating, perhaps using wire through the hinge points

    2) use "wing warping" for steering instead, though it would take more power

    3) some other novel method of steering such as weight shift (as used by hang gliders) in a heated container. But I don't think it as ever been done in a model and is probably impractical.

    1. Poor Coco
      Boffin

      Freeze-proof controls

      You can make R/C control surfaces that are immune from binding by avoiding discrete hinges entirely. Instead, stitch the control surface to its mounting point using monofilament line in a figure-8 pattern, viewed in cross section. This should work well even at extremely low temperatures, as monofilament is really tough stuff — but of course, a trial is required.

  20. Eugene Crosser
    Boffin

    Tractor design

    may be a Right Thing given the launch platform may be unstable. Possibly, the configuration can be designed in such a way that it slowly turns upwards in the flight, then the initial launch angle will be unimportant. Maybe the launch even can be triggered by the burst of the balloon.

    How do you plan to overcome the problem of asymmetric thrust? Single chamber, multiple nozzles?

    If the GPS does not work at high altitude, you might just keep the right direction (via magnetic or solar sensor) until the GPS locks in.

    1. Poor Coco
      Boffin

      Asymmetric thrust

      Thrust asymmetry can mostly be solved with trigonometry: as mentined above, four engine4s firing away from the folded wingtips at a shallow angle providing the upward oomph, with two engines firing at a larger angle from the centreline in order to clear the folded wings and balance the thrust. A single combustion chamber with multiple nozzles would need custom manufacturing and would be extremely difficult to make, especially given weight constraints.

      The tricky part will be ensuring simultaneous ignition; this can be addressed by having highly charged supercapacitors for the igniters. They will provide a REALLY high-current pulse which should be enough to fire all 6 igniters within a millisecond or so of each other, especially if the igniters are all wired in parallel (the first igniters burning out will result in even more current through the laggards, triggering near-instantaneous completion of ignition).

  21. Anonymous Coward
    Anonymous Coward

    Smartphone > camera + video camera + gps + phone home beacon!

    Suggestion: replace the canon camera with something like an iPhone 4. It has 2 cameras: a reasonable rear still camera that can be used to take a snap every x seconds, and a VGA front camera that can capture video. I don't see any major difficulty in doing both at once (and I write camera apps for iOS).

    As a bonus, it happens to have GPS for tracking and a data connection for it to phone home. It's pretty small and light (especially once it's stripped of the case, and presumably the screen - you could set it going from a terminal connection before launch, and you'd have to modify it a little to get suitable angles on the cameras). Battery life might be enough as it is, if not external batteries are available (which again could be stripped).

    1. Anonymous Coward
      Anonymous Coward

      Launch trigger

      If there was likely to be a phone signal up there, you could connect the launch thing to the phone's vibration motor connections and ring it to launch the rocket. Telesales people could be an issue here though.

  22. Nexox Enigma

    Carbon Fiber

    If you're going to play with composites, do a bit of reading and testing - if you expect to need the sort of strength that carbon fiber is capable of, then you'll have to get a few things right. If you, say, make an unbalanced layup, your wings could twist subtly when loaded. If you don't expect those sorts of loads, stick with something cheaper than carbon fiber.

    Also, if you're looking for ways to insulate the electronics on the craft, maybe take a look at that aerogel matting you had an article on a few months back? In addition to apparently decent insulation and weight qualities, it's fire resistant.

    1. JimC

      few things right...

      Oh come on. There's nothing magic about carbon... Unbalanced layup, wing distortion etc etc will be just as much of an issue whether you're working with carbon layups or A4 paper... In fact probably more with lower tech materials... We amateur boat builders use carbon all the time, and one of the nice things about the stuff is that you can overbuild fairly dramatically to allow for limited facilities/operator capability and still end up with a lighter and stronger structure than you would with other materials.

  23. Charles E

    The Plane that Fell to Earth

    I suggest you first take a look at the flight plan, before designing the aircraft. This might address my criticism of PARIS which landed very close to the release point, indicating it did not really fly, so much as plummet. I noticed Samsung copied the PARIS flight concept as a commercial stunt, they sent up a balloon with hundreds of paper airplanes with memory chips affixed to them. They reported planes recovered hundreds of miles from the release point. This shows these simple fixed wing paper planes had a good glide slope, flying horizontally for a considerable distance. However, this is also a disadvantage in recovery, unless you have an international team to recover LOHAN across Europe (and perhaps the seas).

    So I suggest taking some design cues from model rocketry. There is a type of rocket known as a "boost glider" that somewhat resembles my proposed design goals for LOHAN. A boost glider has two flight phases. First, the rocket boosts to a high altitude, and the boost stage burns out and ejects. Then the glider stage deploys, the wing shifts its aerodynamic qualities from vertical flight to glider. The key factor here is that in order to not chase the glider to a distant landing point, the wings are designed to put the glider into a gentle spiral, circling the release point. This is intended to maximize flight duration without flying the thing in a straight line into another country. This also has the advantage that the characteristics of the spiral flight can be fixed into the design without need for autopilots. In some cases, a simple aileron adjustment is all that is necessary to create the gentle turn required for a circular flight path.

    The best boost glider kit I ever built will address some of the problems I see in Murray Pearson's proposal. His folding wing design seems to require a mechanism to unfold and fix the wings into flight position. The design I built was a kit from Estes, with a one-piece solid wing that rotated into place around a central pivot. During flight phase, the oval wing as inline with the rocket body. When the boost stage separated, it released the wing, which pivoted 90 degrees, pulled by a rubber band. This is a much simpler design than Pearson's which requires dual wing deployment. Vintage Estes model rocket plans are archived on hobbyist websites, but I was unable to find the rotating wing design. Still, that was perhaps more of a design stunt than would be necessary for LOHAN. Most boost glider designs have fixed wings that merely adjust ailerons during the flight phase. This would be sufficient for LOHAN, since the balloon will lift the glider during the initial lift phase, eliminating the need for aerodynamic characteristics needed for self-powered vertical flight. However, your proposal for a rocket powered initial flight stage would still require a stable flight platform. I might suggest using an example like the SEMROC Swift-BG design.

    http://www.cdimodelrocketry.com/proddetail.php?prod=SEMROCKV27

    It doesn't have any complex unfolding wing design, it's simple and looks effective.

    1. Poor Coco
      Boffin

      I know the boost-glider you refer to...

      ...and it works really well in the low-power low-weight regime but will not function so well for this. Why not? Because the payload listed by El Reg will be a significant fraction of a kilogram, compared to maybe 150g total launch weight for the Estes swing-wing boost-glider.

      Simple hinged wings can be accomplished with piano wire inside nylon tubes, which should become looser when chilled because the thermal coefficient of the steel wire is greater than the nylon tubes. The deployment force can come partly from aerodynamics (position the elevons in a drooped position to start it) along with, say, some mousetrap springs. I don’t recommend avoiding the folding wings entirely, as the triangular wing configuration will provide lateral stabilization and nullify net lift during the boost phase.

      — Murray Pearson

  24. HonourableTyr
    Mushroom

    Please use metric!

    Please use metric DAMNIT!!!

    Explosion because NASA knows what happens when you use imperial units.

  25. Steven Roper

    Folding wings = not good

    Moving parts have serious problems functioning in near-vacuum and at low temperatures. Ordinary lubricants freeze, joints contract in the cold, and so these wings are likely to cold-weld or seize up very quickly. NASA uses^Hd very expensive lubricants and specially engineered joints and hinges on movable items like the space shuttle doors, which you may or may not have trouble sourcing for LOHAN - even if you can, the cost is likely to blow your budget real fast.

    So I'd stay away from moving parts as much as possible. Obviously you need your release mechanism, but folding wings represent an unnecessary risk of failure.

    1. Poor Coco
      Boffin

      Mechanically, folding wings shouldn’t be a problem...

      ...as long as the hinge mechanism is one that tends to loosen up rather than tighten up in cold temperatures. A nylon tube with a steel piano wire is an example of this, with simple devices like mousetrap springs to add opening force along with aerodynamic forces.

      — Murray Pearson

  26. VeganVegan
    Thumb Up

    Thrust asymmetry?

    I would think that if the rocket thrust vector does not go straight thru the center of gravity of LOHAN, she will end up spinning (pitch, roll, or yaw).

    Lining up the thrust vector presents a challenge for both tractor and tail mounting, that are relatively distant from the cg. How about mounting the rocket just like a JATO, at an angle, immediately underneath the cg? The mounting angle might also take into account the size of the inflated balloon.

    True, there will be increased air resistance over the planform area of LOHAN, but, if you are really going that high, this might not be as great an issue as at sea level.

    1. Poor Coco
      Boffin

      Not straight through the CG!

      If the centre of pressure is directly through the CG then the rocket will be neutrally stable, i.e., it will keep going in whatever direction the nose is pointing at all times and will not be controllable. A JATO takeoff works because the airplane's tail is far back, allowing control.

      Passive aerodynamic stabilization makes the CP fall behind the CG. Mounting the rocket pod (with cameras, etc.) far ahead of the aircraft will shift the CG forward, resulting in stability — the folded wings and vertical stabilizers will cause a stabilization CP aft of that point.

      — Murray Pearson

  27. Rick Brasche

    dont be afraid of electronics

    electronics are inexpensive and rugged these days. solid state gyros are available that can handle quite a bit of abuse. I'd recommend an active swivel nozzle on the booster to give it actual drive control that can counter for strange winds, weird release angles, or other issues.

    Another problem is vehicle stability on the way down. you'll need to make sure it is stable and pointing (preferrably downward) and into thick enough air before wings deploy. there's a NASA concept about using dropped-from-orbit aircraft to explore Mars that has some concepts.

    I'd suggest a very robust, active and smart control system and sensors on board the flight vehicle itself. then all that is disposed of is the balloon, enpty fuel tube and the servos involved. the glide home will be the easy part. DIYDrones.com has ya covered there already.

    1. Poor Coco
      Boffin

      Electronics isn't the problem...

      ...weight is. Active swiveling nozzles, especially for the 8–12 engines I imagine for LOHAN, would be really bulky and heavy. However, servos providing two-axis pivoting of the entire rocket pod could compensate for the asymmetric thrust and also provide guidance in concert with the elevons on the folded wings, without much weight penalty.

      — Murray Pearson

  28. SteveD

    GPS

    It's not a problem getting hold of a GPS unit that works at over 18km. The Trimble Lassen IQ units used in PARIS are easy to get hold of. The restriction is 18km and 515m/s not or.

    The advantage of using APRS on the European 2M frequency, is that other than perhaps final recovery, the reception and tracking is all done by the APRS network. I have a plot showing that PARIS covered most of Spain. (Not sure it got published on the reg)

    @Lester. the 2M high power tracker is available should you want to use it.

    1. Nick Condon

      Maximum altitude at launch.

      Is it not possible to monitor the pressure in the HELIUM filled (presumably standard latex) meteorological balloon and launch on a sudden drop? As the balloon ruptures the pressure will fall by a very small amount but the balloon material will take a while to empty and collapse.

      I use solid state pressure sensors in model submarines and with a trivial quantity of electronics they will reliably pick up a very small pressure change.

      Such a trigger would provide an automatic abort launch in the event of early balloon failure. If all goes well would launch LOHAN at the absolutely maximum altitude.

      May not be worth the risk/complexity but perhaps worth thinking about?

      Nick.

  29. Hawkmoth
    Thumb Up

    Rocketry to the MOOON!

    I agree with the earlier posts about simultaneous ignition, whether in use in a tractor configuration or any other off-centerline multiple motor configuration. Don't forget, not only do the engines have to ignite simultaneously, they also have to come up to the same thrust along the same curve. Even small asymmetries will TOAST the mission. I like the short, fat configurations of several of the X-Prize entries that put the thrust above the CG by putting it in a hole in the middle of the craft.

    I agree that deploying the wings as illustrated in the Pearson model will be difficult. As with the rocket motors, keeping all the forces simultaneous and symmetric would be tough. I'm very familiar with the Estes sissorwing model mentioned by Charles E as I have a finished but never flown example in my attic. I'd be willing to mail it to the LOHAN fab bunker if it would help the mission.

    1. Poor Coco
      Boffin

      Simultaneous ignition: solved.

      If the igniters for one stage are all wired in parallel and triggered by a high-current SSR, then dumping the energy from highly-charged supercapacitors will result in essentially simultaneous ignition. Any slight asymmetry on launch can be corrected by aiming the engine pod with 2 servos.

      — Murray Pearson

      1. Richard 12 Silver badge

        I still think the thrust vectors from all engines should be parallel and close together

        With the thrust vectors as drawn, it'll be impossible to recover from an engine failure - you'd have to aim the remaining engines through the craft to get back to straight, and that is probably not good.

        Having the engines parallel and very close to each other means that engine failure or imbalance won't have a such huge effect as the vector sum would still very similar to the design angle.

  30. bkcokota
    Coat

    Rocket shape?

    I think using the tractor rocket idea is wrong, I do agree that it works on actual rockets, however, LOHAN is not a rocket it is too slow and does need to land right? I can think of very few rockets that have actually landed, it seems to be more similar to aircraft, as such I suggest use of a delta wing style instead, for example:

    the Avro Vulcan bomber- http://en.wikipedia.org/wiki/Avro_Vulcan

    the Concorde- http://en.wikipedia.org/wiki/Concorde

    The Blackbird- http://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird

    The space shuttle orbiter- http://en.wikipedia.org/wiki/Space_Shuttle_Orbiter

    All these aircraft use some style of delta wing, and a lot of them are used at extremely high altitude where due to their large wing area they have better maneuverability and lift and as such are more energy efficient at such altitudes, the aircraft shape itself is very easy to make and can be built extremely strong, there is also the fact that when landing the high drag produced with a high angle of attack means it can shear speed rapidly, and that is one of my main concerns for the tractor design, the actual landing will have to be done at a high speed because of the wing area. I believe that the shape of delta aircraft lend themselves to be rocket powered craft also, you could build a large cylindrical body with lots of room for the required kit and an internal engine and it would still be easy to balance and strong which is important if things go badly during any of the stages. I can produce model designs to show the proposed shape if so desired and seriously suggest that this be a better idea than a nose-heavy tractor.

    1. Poor Coco
      Boffin

      Have you actually exampled the plans?

      The design’s a flying wing; the tractor tower is there ONLY for the vertical upward portion, after which it’s jettisoned.... and then it won’t be nose-heavy any more. But on the upward flight, you definitely DO want a nose-heavy configuration for stability.

      The wing I chose for the concept is a flying wing slope racer, designed for high speed, with a fuselage added for payload capacity (and to make it look like a flying vibrator). The slight nose-forward positioning of the fuselage allows for the leading-edge ballast to be omitted and replaced with payload, while maintaining a proper CG for gliding flight after the nose tower jettisons.

      — Murray Pearson

  31. Mips
    Childcatcher

    "folding wing design" ?

    If it achieves any decent speed, yes they will, and probably a the most inconvenient time. They might even drop off. Anyway I thought this was to be a rocket not a plane.

    If you are using a tractor motor what is the fuel? I had assumed you would use solid fuel but even the largest commercial rocket achieves only a 2 second burn. If you has a conventional push motor you could stack the motors to get a longer burn and more range but not if it is in the head - what then?

    1. Poor Coco
      Facepalm

      *sigh*

      There are two stages, with 2.6 seconds burn time each, in this concept; total 12 E-class engines (which places it in the I power class overall).

      And if you read anything you would know the project is to build a rocket boost-glider.

  32. TopDog64
    Pirate

    Controling Vulture 2

    First of all I wish to express my disappointment at Helium being used as the lift medium. I fully understand the safety implications involved, but Hydrogen is not a gas which is in scarce supply on this planet and is much cheaper.

    You are batting on a sticky wicket if you think that a tractor rocket will be stable without any form of control. The WWII V2 rockets used graphite guidance control vanes in the engines exhaust (http://en.wikipedia.org/wiki/V-2_rocket) and modern SCUD missiles still use a similar system (http://www.astronautix.com/fam/r17.htm). I suggest using a rocket in pusher mode with graphite guidance control vanes using PTFE hinges (away from the exhaust gasses) and use of shape memory actuators instead of servo motors. Solid state gyros and accelerometers are available off the shelf (Nintendo Wii handsets) to provide electronic guidance.

    Best of luck.

  33. Anteaus

    Rocket stability...

    There are basically only two ways to stabilize a rocket's flight path, and those are to spin it, or to have some kind of autopilot.

    The rocket can be spun-up by an electric or gas motor prior to launch, or by gas or rocket jets on launch. Disadvantage of spin is that it's difficult to impose any steering on a spinning vehicle, you basically have to point it and hope. Photography ain't gonna work well from a spinning platform, unless a non-spinning camera mount is devised. Wings would need to be such as to not interfere with spinning until glide mode is commanded, at which point they cancel the spin.

    At low altitiudes spin can be achieved by way of canted fins or winglets (which is the usual approach on non/RC model rockets) but it's uncertain whether this would work at balloon altitiudes of ~100,000ft, the air possibly being too thin.

    The other option is a gyro platform and thrust vectoring. Gyros are relatively cheap these days, but the difficult bits would be devising a thrust-vectoring nozzle, and determining the right control-loop gains to give damped control. Plus, vectoring will only work until cutoff, after which (in near-vacuum) the rocket is likely to suffer attitude drift unless it has verniers to keep it pointing the right way. Although, this might not matter too much as the wings will reorient it once it re-enters the atmosphere.

    With vectored thrust, a somewhat nose-heavy vehicle is easier to control than a tail-heavy one. Again this is counterintuitive but it's the way things work.

    BTW, hydrogen gives substantially more lift than helium being much less dense, and for a project like this would seem the obvious choice, in spite of fire risk.

  34. Cliff

    Lots of technical questions and discussions

    I do love the fact that LOHAN is *our* LOHAN, much as we all had our dabs on PARIS previously :-)

    Aaaanyway, there seem to be a lot of technical discussions I am not qualified to celebrate or begrumble, so I have to address the more important questions - colour.

    What colour will we make the thing? I vote for brazen orangey-tan colour. And any chance we can have some less aerodynamic than PARIS but probably more comfy rounded curves on LOHAN?

  35. horsham_sparky
    Boffin

    offer still stands

    if you need help with the sparky stuff (firmware/hardware electronics),, the offer still stands, I still have time between worky "optical metrology" and hobby "uber-fast drag-racing model train" projects :-) you need but wave the sodden beer-mat of surrender above the bar

    my fee remains equal share of any booze that get handed around and the well earned kudos of something that actually works (assuming it does, and the mechy boys haven't made a balls-up :-)

    p.s.

    you can minimise your weight load by having a single battery for all your electronics and boost/buck converting for the various voltages that you need. there are plenty of low mass/volume devices kicking around for just that.

  36. Crash!

    45 degrees?

    Seems a waste.

    If you had a doughnut-ring shaped balloon you could go straight up through the middle.

    1. Anonymous Coward
      Anonymous Coward

      Multiple balloons

      Or 3 spherical ones would leave a nice vertical gap through the middle.

  37. Poor Coco
    Boffin

    Empirical Data

    Yesterday (Saturday), after reading about the pendulum fallacy, I built a small test rocket in tractor configuration without stabilizing fins or a launch-lug for guidance. It achieved a maximum altitude of about one foot and was completely unstable! I stand corrected.

    Clearly this needs some testing and research on attaining stable launch.

  38. acat

    Dumb question - why a spherical balloon? Why not a toroid?

    A toroidal (or "doughnut-shaped") balloon, with a launch tube through the doughnut-hole, would allow for avoiding the pendulum entirely - launch on a rail (or a guide rod, ala model rockets) to make sure the bird goes through the doughnut-hole, and don't launch until within 20 degrees of vertical.

    Probably need something like a stent through the balloon to keep it from collapsing, but .. even a double-layer of latex with some glass fibers (from common-as-dirt insulation) should do the trick - most of the expansion will happen on the non-reinforced part of the balloon. Could even get clever and use the toroid reinforcement to suspend the payload to ensure it stays in alignment.

    No "sacrificing the balloon", and less pendulum-problem.

    Just curious why this isn't in the comments.

  39. Anonymous Coward
    Anonymous Coward

    Thermal Materials

    Just a thought have you considered using DIY store type spray fire foam for insulation and construction? You could use it to mold items too that need to be heat resistant like the wings.

    Not sure on the weight v other materials, but it will fill in all the areas around non moving cold sensitive items and gives good impact protection for reuse of the payload.

  40. TopDog64

    Design

    Why not model Vulture 2 on Spaceship 2 which Virgin Galactic are to use.

    Its predecessor is a proven re-entry an glide design. I exppect that Scaled Composites would supply design and material info in return for data obtained during the flight.

  41. ThisIsNotMyHandle

    Stability

    The rocket will in all probability have issues with non-uniformity of thrust. A good way to compensate for this is to rotate the rocket (as stated above). The exhaust gases of the motor could be nozzled (passive nozzling rather than active) as to induce a rotational motion. Spin on the nose could be a problem for guidance (a gravity compensation will prob be required in order to maintain an escape trajectory), and for instrumentation. The nose however could be designed to be able to spin freely from the body (some form of roll control will be required). Thereby having a directed rocket burn and more stable flight. Lift will be hard to come by up there therefore gravity comp may be very difficult. A rotating body may also be harnessed to unfold any wings/control surfaces that require storing for ascent.

  42. Ironclad

    Vertical launch through a ring of balloons

    Just a thought but could you not tether say four balloons via a lightweight but rigid ring ?

    The ring would attach to the 'basket' holding the rocket which could be positions for a vertical launch.

    Assuming you know how much the ballons will expand before launch the ring would have to have sufficient diameter that there's still a hole to launch through.

  43. Intron
    Thumb Up

    F-19

    Love the Photo used as a mock up. took me ages to work out what it was I thought it was the X-19 GI Joe plane i used to have when i was a kid till i relised it was the F-19 model kit i used to have in the 80's Loved it but totally confused me for AGES working out what it was :)

    1. TopDog64
      Pirate

      Is this it?

      Is this the model kit you mentioned? http://homepage3.nifty.com/formodelersbywb/f19-11.jpg

      If it is, then this picture of the completed model certainly supports your opinion. http://www.fiddlersgreen.net/aircraft/Lockheed-F19/IMAGES/f-19.jpg

  44. Helldesk Dogsbody
    Boffin

    Wing Shape

    I'm really not sold on the delta configuration (although I don't actually see an issue with the folding wing proposal) as it isn't the best for stable gliding or control. Why not try for something more akin to the Barnes Wallis Swallow swing wing? Suitably modified, of course.

    That way you can get a nice, long lean rocket phase and a stable, broad spanned traditional glide phase while keeping the weight down nicely. Cut the wing sections from foam and skin them, as per current RC aircraft, and add a carbon fibre stiffening rod to each which will also give you something to attach the pivot to as well as a lever for the opening mechanism which could then be as simple as a restrained spring hooked up to a yoke for simultaneous opening. The catch releases, wings go *SPROING* and hey presto! one glider.

    Sticking with the tractor rocket motor proposal, rather than have a separate stage that is detachable mount the rockets to a Y shaped canard on the nose of the aircraft. The lower fin shouldn't create too much drag, the upper two should provide a touch of stability owing to the dihedral effect. Mount the rockets in a faired pod at the end of each canard and they should be far enough out from the fuselage that a simple foil sheath will protect what's underneath.

    A butterfly tail at the rear should provide the rest of the dihedral stability and at least partly counter a flat wing as well as providing the rear control surface without having to go down the elevon route.

    If you use a lifting body fuselage then you should get greater lift, better stability and greater load capacity than a simple cylinder. The mass of the fuselage can be kept low by shaping it from expanded polystyrene using a hot wire cutter, solar film skin and/or foil to keep a smooth surface as well as it's insulating properties preventing low temperature damage to the electronics gear inside it. Add carbon fibre stiffeners where required to take the structural load without increasing the mass too much.

    6 Aerotech E28s should give a nice amount of oomph for the boost phase as the model wieght ideally would be below 3 KG, even with all the electronics gear (approx 235 N thrust for 1.2 seconds). Alternatively use long burn ones like the Apogee E6 with a 5.8 second duration and a similar amount of overall thrust. You could even combine the two for an initially larger boost to start with going to a gentler, sustained boost afterwards.

    I believe that the abopve would be a touch more efficient but also should look significantly more elegant - think along the lines of a B1 fuselage with a Y canard added to the front and a butterfly tail to the rear rather than a conventional tailplane.

    1. Poor Coco
      Boffin

      Hmmmm, the Apogee E6 does look good...

      Here is a comparison of the Aerotech E15 (which I have been harping on about) and the Apogee E6:

      http://www.jetboyrockets.com/motor/compare/19/23/

      One REALLY nice thing about the Apogee engine (aside from the fact it’s from Apogee Components, who totally kick ass) is the fact there is the E6-P version which has no ejection charge at all (the P stands for 'plugged', it’s intended for use in boost-gliders). I wonder why I did not notice that earlier?

      I really do not think the E28 is a good idea — boost-gliders need long continuous thrust, not high thrust which greatly increases dynamic loading.

      — Murray Pearson

      1. Helldesk Dogsbody
        Boffin

        Good point

        Fair dos, the only reason I suggested the initial higher boost is as a separation charge, higher thrust initially to get it moving before applying more continuous thrust to gain altitude.

        It looks like that would be totally unnecessary with the E6 power curve though as it has a nice peak after about 0.4 seconds and then smooth power delivery after that. The E15 has a bit af a "KABOOM" factor to it which, as you quite rightly pointed out, would put a lot more stress on the structure.

        The E6-P definitely looks like a find as well. However, as it has no ejection charge it would appear to be even more suited to single rather than multi stage. Also one less thing to go wrong if there is no stage separation to worry about.

        I'm still a bit concerned about the design though. The typical loading of the Skua 1500 looks to be about 300 grams. OK, so the long glide time normally produced isn't needed but the amount of weight required for the GPS etc is probably going to be the best part of a kilo. That loading on that wing section I'd expect to lead to more of a barely controlled plummet rather than a glide back to earth.

        Folding the wings as well I'm finding a bit of a stumbling block. I don't dispute the necessity but I can't see how folding them downwards will reduce drag in any way, let alone how to rig an opening mechanism that doesn't either foul the fuselage or add way too much weight. A one or two piece swing wing still looks to be a better bet to me. Have a look at the NAR XP-2C (www.nar.org/competition/plans/pdf/xp-2c.pdf) as that seems to use a more conventional form and is specifically designed for rocket propulsion. Give it a lifting body fuselage above the wing and rocket pod and it might be easier than adapting the skua suitably.

  45. Hawkmoth
    Boffin

    stablization

    I think stabilization and attitude control at altitude (where almost no aerodynamic forces will be available) will be one of the biggest challenges. I like spin stabilization because of its simplicity.

    Photography on spin-stabilized space probes is accomplished either with a stable photography platform, which won't be possible on LOHAN but also by using the spin itself as to move the camera's narrow field of view across the subject in successive strips, building up a photo through a raster-type system.

    That said, I wonder if there's some fiendishly clever way to build a really crazy simple reaction control system using reaction wheels or set of simple thrusters. The X-15, an early fore-runner of LOHAN had reaction control thrusters to maintain attitude when it was flying too high to use aerodynamic control surfaces. You know, something made out of toy cars with their tyres replaced with metal flywheels or with aerosol cans pointed different directions and tiny actuators.

  46. Anteaus

    Simple but effective ideas...

    Talking of simple flight-stabilisation ideas, the early Sidewinder used rollerons - A notched wheel was spun to high RPM by the the airflow, and if the rocket rotated the wheel's precession force turned a tailfin the right way to cancel the rotation. Worked a treat and (in pre-IC days) saved a bulky lump of electronics.

    SInce the rolleron relied on airflow it wouldn't work in vacuo as designed, but a similar idea with a wheel spun-up by the rocket exhaust and turning a steering vane or gimbal might work.

    Though, I'm inclined to think that either spinning the vehicle up before launch, or else a non-spinning vehicle with 3-axis solid-state gyros and thrust vectoring are the approaches most likely to work. Gyros are more complex and need a lot more setting-up but they do allow you to determine, within a reasonable degree of precision, where the thing goes. They also allow for self-correction, up to a point, of a bad launch attitude.

    In principle a horizontal launch could be used if the vehicle is gyro-controlled, it being commanded to go into a climb after a few tens of feet of travel. This overcomes the issues of clearing the balloon. Though, the toroidal balloon idea is interesting, and could be a simpler solution than developing the necessary trajectory-control software for a horizontal launch.

  47. Anonymous Coward
    Anonymous Coward

    Spinning the rockets, not the whole thing?

    Spinning the thing gets you stability but the cameras a re a problem. So why not have the rocket motors at the front mounted so that the whole rocket assembly can spin. Mount the rocket motors at a slight angle to make it spin. I'd expect a small ignition system could be fitted in the spinning section to avoid wiring issues. If the spinning friction can be kept low enough the main plane should stay fairly stable for the cameras.

  48. Vladimir Plouzhnikov

    Wing

    I think the delta should be of higher angle (lower aspect ratio). Either that or consider adding large winglets. You need to somehow get LOHAN out of spin in which it will start its glide and high-angle delta is basically self-recovering (unlike the high aspect wing of PARIS, which never had a chance, poor soul...) if the CoG is sufficiently far forward.

  49. Dave Harris 1

    Launch slightly downwards?

    OK, this may be daft but a variation on this works for the Shuttle:

    Launch pointing slightly (a lot?) downwards so, being nose-heavy, LOHAN would dive stably and continue unpowered until it has acquired sufficient velocity to give the control surfaces sufficient authority, then start pointing the nose upwards & fire the rockets, continuing the pitch up until vertical. This totally avoids the possibility of impacting the balloon(s).

    I have no idea if this would mean sacrificing a significant amount of max height but a small loss may be worth it.

  50. Slay
    Facepalm

    How are you measuring attitude?

    What sensors do you have that will do this?

  51. deset rat

    Stability during burn

    Any difficulty in obtaining simultaneous ignition and thrust buildup on the multiple rockets would exacerbate stability problems of keeping it on course during the boost phase. See the "typical" curves given for one brand of model rocket engine (http://www.hobbylinc.com/rockets/info/rockets_enginefacts.htm) . No production tolerances are given.

  52. rwbthatisme
    Flame

    Napkin thoughts

    I've been jotting down some thoughts & designs on a handy napkin, and the main things I think we need to consider are the following:

    1. Weight, I think the the ballon can lift around a maximum of 3kg usable payload. To get the maximum altitude after a motor burn we need the plane & control systems to be bare minimum of no more than 500 - 700gm weight. An iPhone for example is 140gm, so electronics & control mechanism are going to have to be 300gm at most. The Ardino board has sufficient avionics to do the job including an airspeed & barometric altimeter (more later).

    2. Rocket Design, with 2.3kg of weight available for propellant / motors, the best option is to have a staged rocket motor assembly (ie Saturn 5 etc), this will give us the maximum burn time and potential altitude. By clustering 6 rocket motors in each stage and knozzle'ing them through a single chamber (shroud) we can overcome the vagiaries of motor ignition, so through the motors may not ignite symiltaneously they will be generally thrusting inline etc.

    Refering to this link: http://www.thrustcurve.org/motorsearch.jsp (My maths is a bit rusty), but clustering 6 x 5n AeroTech E7 rockets together should thrust around 3kg of lift force for 5 seconds of burn time, at a weight of 50gm each motor, each cluster would have a weight of 300gm so very rough maths we have 700gm of plane & 7 x motor assembly stages + 200gm spare and a burn time of 30 seconds which should get us up to around 500 - 700mph and an extra 10,000 feet altitute so perhaps we can get to 90,000feet? http://webalt.markworld.com/multistage.html

    3. Vertical launch; as long as the CoG is as far forward (nose) as posible and we have some drag to the rear of the rocket (ie fins). we should be able to launch using a fairly basic hook & eye mechanism. The avionics & barometric altimeter can be programmed to initialise the launch sequence before the baloon bursts, at which point the rocket assembly will be hanging in a reasonably vertical position (being that at 80,000 feet wind speed is going to be less chaotic, so any swing should be rasonably little) and as it shoots up into the inky blackness the hook drops from the baloon cable and we are gone!

  53. Hally

    Thin Atmosphere

    How do these solid rocket motors perform at such high altitudes? Are there any known tests that have been performed?

    1. rwbthatisme
      Go

      Thin Atmosphere

      That should not be an issue, rockets work in a vacuum, solid rockets combine the oxidiser& propellant in a homologous lump so it should do fine. The thin atmosphere will actually help, the launch and as there is less aerodynamic drag so accelleration should be better.

      The main issue is the cold at 80,000 feet its about -60 -> -70C. The best motors we can use (aluminium perchlorate) are electrically started and making sure there is sufficient current in the batteries / capacitors to kick them off is a headache. We'll need to include somekind of warming elelment & thermal insulation on the design to protect the avionics & battery pack.

  54. John Jennings Silver badge

    Umph

    Hi to lighten the load of LOHAN, would it be effective to put the ignition system on the launch platform, attached to the baloons, rather than the orbiter itsself. Anything you dont need to carry can stay on the baloon. Would advise a second GPS system and drogue to find the baloon in the event of launch when all these super caps etc are onboard...

    With 3 baloons, is there a lateral force which would reduce the altitude with the baloons pressing against each other? To avoid that, (if its an issus, I dont know the sums) a truss holding the lines appart, something like a yacht spreader might avoid that - launch weight is less concern if there are 3 baloons....

    For vertical stability, a small 4th baloon at very slightly hight pressure could run up the middle - when it pops, you launch up the centre...

    would it be feasable to launch the rocket with a mortar on the platform? (there would obviously be a shock) Wire spools unwraps the wings and fires the lgnition of the main rocket engine (from those Super caps on the platform ) when the rockets light, the speed is already such that the wings can stablise... Wires drop off lohan while flight is stablised....

    Probably also want to discard the rocket motors as they fire off...

    Foo

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