... does anyone else feel a bit dirty after realising we've all jumped on a very web 2.0 style crowdsourced project?
We sort of knew we'd rue the day we asked you lot for your suggestions as to how exactly to launch our Low Orbit Helium Assisted Navigator (LOHAN) spaceplane, and so it turned out to be, as were were buried under a veritable bucketload of ballockets. Click here for a bigger version of the LOHAN graphic What we're looking for …
Use the technique we have for CV selection.
Print out each design onto a separate sheet of A4. Throw them all up into the air at once. The luckiest design (or, in the case of CVs: applicant) is the one that lands on your desk. Pick that one.
Since you have no way of determining just by looking at the paper design whether it will "fly", you might as well pick one based on how inherently lucky it is. Since luck will play a heeee-ooooge part of the whole LOHAN project, you may as well get as much of it on your side as possible.
As far as using this method for job applications is concerned, there is some debate about it's efficacy. One school of thought is that the truly lucky applicants' CVs will land as far away from the selection zone as possible - thus minimising the chances that their owners would ever have to work for this organisation. In that case there's a conflict between the luck of the candidate and the luck of the employer. That's a quandry that has yet to work itself out.
very rich in ideas.
Set me thinking again. How about a "trapeze" below the instrument payload. Lohan aircraft on end (aligned horizontally). When the rocket engine is fired the trapeze is driven round in an arc and when it reaches the right angle (45ø) the release mechanism triggers and the aircraft flies away.
The engine has time to "get going" (if that's an issue) before release.
If the balloon fails before planned release point the aircraft could still launch (at the less than optimum angle.
A rigid trapeze means the aircraft is in a fixed orientation with the instrument package making for better photography on the way up.
I have a horrible feeling all those designs requiring some form of interaction with the atmosphere are overestimating just how much force a flight surface is going to produce. If LOHAN gets to 80k feet then atmospheric density will be about 3% of that at the surface, with an equivalent loss of pressure.
If you have a control surface of 10cm2 which works fine at the surface it will need to be roughly 3.3m2 to gain the same amount of authority at altitude. I would use an angled launch rail myself.
Well done everyone, lots of great and interesting ideas and quite some out-of-the box thinking.
I have no experience in any of this, but watching a lot of scrapheap challenge + general gut feeling (and LOHAN team design parameters) point towards the minimal design that will get the job done. So, no multiple / toroidal balloons (although as per one of the posts above I am tempted to go for 3-balloon arrangement just to be able to call it Eccentrica), no fancy mechanisms, minimum of moving parts.
Tim Harris' idea scores high points with me too, for all of the above reasons. No moving parts, the direction of the craft wrt wind direction is stable, and Vulture 2 can launch without needing retracted wings that unfold at a later stage. Also, having the main payload at some distance from Vulture 2 will allow a good field of vision for filming the launch
I agree with lawndart about the issues of aerodynamic stabilization. I have been working out a design (drawing coming in later today) with one main lift balloon, three smaller stabilization balloons at lower inflation and a vertical launch guide between the three stabilizer balloons. When the main balloon bursts, the plane launches between the three lower ones.
For weight concerns, obviously any struts have to be extremely light for their stiffness. A spaceframe made of basswood can meet these criteria; I can forward photographs of representative possibilities.
— Murray Pearson
How about a single modified balloon, with a vertical launch tube running through it for the full height? It's simple, it's always vertical (never involving any sideways forces), it's not going to be affected if the whole thing is spinning wildly (which I think the asymmetrical designs are mostly vulnerable to --- but is it going to happen?).
The rocket (at the bottom of the tube) will act as a stabilizing load to keep the balloon vertical during the balloon ascent, and if the tube is closed (or partly closed) at the bottom, the thrust on the tube bottom from the rocket exhaust during launch will continue to help to keep it vertically stable.
Honestly, I don't think launch will be the worst problem. It is easy enough to make a latch that releases once the balloon bursts and there is no longer any upwards pull. Then it is just a matter of balancing the plane so it is angled slightly upwards when suspended from a single point.
What is going to be a much more serious problem is how to avoid the plane just spinning round itself like a firework rocket without a stick. Also, how to make sure the lifting surfaces will work both under powered flight and for the glide down, which will (hopefully) happen at wildly different speeds.
Forget wind-driven orientation. If there is any wind, it will be blowing downwards (due to the ascent of the balloon relative to the air). Cross wind would only be transiently appreciable during transition from one altitude to another in which the winds are blowing in different directions. And, at high enough altitudes, the low air density is not much to count on (i.e., need large aero-control surfaces)
I would also cast doubt on methods that have no means to account for the rotation (about the vertical axis) and, worse, the pendulum-like swinging of the payload/LOHAN: even if you have a launch rail of some sort, it could be pointed at any of a large range of angles, in any direction.
It may be instructive to observe the behavior of a small toy balloon to get a feeling for the gyrations of a payload dangling from 1 versus multiple strings. That, or review the video of PARIS ascending to see how the payload might behave.
Has anyone considered zero-pressure balloons that do not burst like latex ballons? They are basically a giant polyethylene shopping bag partially filled with helium, with the bottom open to the atmosphere. They rise to a float altitude, and simply stays there.
I can't help but agree with lawndart (hangie pilot, perhaps?) in believing any idea of aerodynamic steering is pointless at that sort of altitude. Since the aim is to get the rocket aimed generally upwards as soon as things start happening in the balloon bursting department, it seems to me you have only two real options:
1) have it pointing in the right direction to start with, or
2) vectored thrust.
Good luck writing the flight control software for (2) - starting with an unknown position, attitude, and vector, and not very long to sort it all out before you lose all the thin-air friction advantage that the balloon's altitude gives you.
I'm not happy with triplet balloons, but even less happy with long carefully balanced struts, rails, and pointers: no-one seems to have remembered the good Doctor Newton and his 'equal and opposite reaction'. A passing fad, no doubt, but I can't help feeling that rocket going rapidly forwards is going to result in a certain amount of balloon going backwards - at the very least, it's going to tip in the reaction and that's going to cause the end of a launch ramp to tilt down. And that's ignoring the issue of a guide/release mechanism that is both light and able to force a direction change of better than sixty degrees without sticking.
Which leaves me with the launching upright approach. This has the advantage that it's gravity stabilised, assuming the mass of the payload is suspended somehow below the balloon(s).
What I would propose is not a three- but a six-balloon system. The balloons would be constrained in a light mesh into an annular shape - a poor-man's doughnut balloon.
This has the advantage that the balloons will automatically assume a hexagonal shape - with a space in the middle the size of the balloons, very suitable for a lightweight horizontal platform to be used for a vertical launch. It also has the advantage that a single balloon bursting doesn't shift the balance too much; the platform will still be vaguely horizontal and the hole won't fill.
BOTE calculations indicate that a 10 metre diameter balloon has a volume of about 105 cubic metres; a four metre balloon just over one sixth of that - very convenient. With six four metre balloons you have a four meter platform from which to launch vertically.
The question becomes then one of *when* to launch: ideally just before the first balloon pops. Presumably there is some sort of specification as to differential pressure for the balloons at bursting point; perhaps some sort of pressure sensor, and trigger just before the expected bursting point? Or, if the rocket motor can be ignited quickly enough, wait for the burst (a gyro will tell you you're tipping over) and then go.
You might want to arrange some automated bursting after launch; the balloon will of course rise faster once the load of the rocket is removed and might even catch up with it in the short term.
p.s. No hydrogen involved!
Trouble with hatching a plan is that we have not been given one, very important piece of information: will the rocket be guided or unguided? Seems to me that an unguided rocket is as likely to spend most of its time shooting straight downwards as upwards, and if you are going to use a guided rocket that works, then the angle of launch is not that important: 45degrees would be easy to rig up, and "good enough" in terms of direction.
PS Don't rely on any of the schemes that rely on gravity to orient the rocket...
PARIS reach a maximum of 90,000ft after about 5,000 seconds after release. At 4,400 seconds it was at 80,000 ft.
How about you hang a pair of suitable launch tubes from the balloon arranged in a V formation. Place inside each tube a firework rocket with 4,400 seconds of slow fuse hanging below. Release the balloon, light the fuse, watch fro the pretty. JD.
The only thing we can say about any configuration, given the turbulent environment from the high winds at 80km, is that the top of the balloon will be higher than the bottom (where the bottom is the bit the GPS etc. hangs off).
Now, if we replaced the spherical balloon with a long thin one, then it too will get errr, enlarged the higher LOHAN goes (oh do stop sniggering you at the back - any symbolism is the product of your dirty mind, I'm not even suggesting the balloon should be made from pink latex, even though there are obvious sponsorship possibilities there). So we have a long thin structure, pointing roughly skywards at all times. All that's needed is a way to get the spaceplane to launch up the side of that and it will automatically be headed upwards.
Go for simplicity. A big pin on the nose of a rocket plane that is aerodynamic and smooth (has nowhere for balloon debris to snag) and just fire the damn thing through the balloon and helium. At altitude the balloon will be stretched so thin that it becomes, to all intents, 'transparent' to a rocket with a sufficiently sharp point and powerful motor.
This way you only have to worry about the launch payload + trigger. Fire at a slight angle to avoid the string (or use a very thin composite pole to ensure you can guide past it) and thicker balloon material at the inflation point.
Why not just have a straight forward platform and balance them? LOHAN on one side, and maybe an identically weighted PARIS (give it a second flight - it's not like its a shuttle being retired for budget reasons).
One goes up (and then down) and one has another shot at the earth unguided (maybe this time with a working gps ;) ). Should give the chase crews an interesting couple of days.
I have built a test section of guiderail out of basswood and balsa: extremely strong (will test it to failure tonight and post a video for your edification).
There will only be one way to get enough speed for aero-stabilization at high altitude, and that is extremely fast acceleration off the line. The way to accomplish this is using a piston-launcher. See http://www.apogeerockets.com/sunward_piston_launcher.asp for an example at small scale.
The concept is this: by capturing the exhaust on engine ignition and using it to force two concentric tubes apart, we can use the mass of the main payload to create a dynamic force that accelerates the rocket much more rapidly. Then, using lightweight trusses to guide the rocket vertically between Eccentrica-style balloon clusters, we can have a long guided acceleration with a very high initial burst of speed.
Of course, this will place strain on the balloons, probably causing them to burst, but with bungee shock-cords this force can be attenuated; and the rig will stay reasonably straight during the fraction of a second that the plane’s traveling through it.
I just tested the guiderail section with the following results:
Mass 131 grams
Length 92cm (36")
Loading: 20kg gradually applied at midspan (simply supported at ends)
Result: Some cracking sounds, minor glue joint failure (easily improved part)
Loading: 40kg at midspan (my son sitting on it, then picking his feet off the floor)
Result: some cracking at ends, more minor glue joint failures
CONCLUSION: I still have the test rail (despite intending to load it to failure), and with moment resistance of 200Nm over this span, we have more than enough stiffness for guide rails. We will need four of these (2 per wing) which add up to about 500g per metre. We can probably get guiderails weighing 300g/m which will adequately guide the rocket-plane.
A piston launcher tube separates from the engine after ignition; but aside from that it's not too different from a mortar (or any other type of gun). The idea of capturing the gases on engine ignition and using that pressure to generate forward motion is identical.
There is of course an identical recoil force; this may be attenuated slightly by adding a very small exhaust port (or ports) on the outer tube, which redirect some gases downward. But I like the idea of the inertia of the payload providing launch oomph, and that kick-off is also an obvious way to trigger the release of the payload compartment and its recovery chute.
There's a very simple way of launching.
Have a 6 balloon design.
Put a PORG (Person Of Restricted Growth) on the launch platform with a box of matches and an air rifle. If a PORG is not available, just use a small child (but remember to tell their parents first...)
When the first balloon bursts said PORG lights match and ignites fuse of rocket. PORG then shoots out balloons one by one for a "controlled" descent.
If lack of oxygen is an issue for the matches, you could equip PORG with a magnifying glass to focus the sun's rays.
If lack of oxygen is an issue for the PORG, make the balloons really big, so it will get to altitude within 2 minutes (maximum breath holding time)....
....and an ambulance to deal with the bends and scrape them off whichever bit of the landscape they end up adorning..... :-)
Hey, at least it would be in a good cause....
Don't forget that there is a rocket motor in this and unless you are going to be exotic it will have to be a standard commercial unit. These gunpowder units have a very limited duration, probably not sufficient for an aeroplane to get clear of the balloon. A rocket might stand a chance but will only achieve another 300m or so altitude. The main altitude is provided by the balloon, for this reason the three tier partially inflated solution will be best if that is what you are after.
On the other hand it this is just about proving the technology then you are doing fine.
On the other hand it this is about the fireworks then I would favour a hydrogen balloon with the rocket firing as the balloon bursts passing through the gas cloud. Now that would be AWESOME.
I assume you mean low-impulse black powder engines. These top out at E power levels; but there are also composite (ammonium perchlorate) engines that go up to (ready for this?) N power. Yep, 500 times more impulse than the largest black-powder motors. They still only burn for about 4–5 seconds, but with an average thrust more like 4 or 5 kilonewtons: one of these will add tens of thousands of feet of altitude, provided we can keep it stable.
...the 'fire it through the burst balloon' option.
If you dangle everything a longish distance below the balloon, and use a tension-based trigger to detect when the balloon bursts, then you have a very simple system. You launch at maximum possible height and the balloon has a bit of time to spread out lots minimising the risk of entanglement.
Impressed though I am at the ambition of some of the submissions, I can't say they all look a doddle to implement.
With that in mind, I propose a somewhat prosaic waste pipe and curtain track based design.
This assembly would hang, nay, dangle, beneath a single balloon in an inverted T, with the main payload forming the base. A piece of rigid plastic waste pipe of say 32mm diameter would ascend vertically towards the balloon, with the tether at the top end, and with a piece of curtain track curving out and away from the riser, braced for rigidity, terminating at such an angle that a rocket-propelled vehicle leaving said track would clear the swollen balloon.
That angle would obviously depend on how big the balloon gets and how far below the balloon the launch assembly hangs. As already mentioned, the further below the balloon you start, the closer to vertical you can get and still clear it.
Vulture II would sit vertically atop the main payload until launch, in her track and ready to go, and upon reaching altitude she would simply ignite, run the rail and shoot up past the balloon and away.
To my thinking, the known unknown is to what extent the whole assembly would be tilted off vertical as the accelerating V2 rocket (ooh, that's unfortunate, isn't it?) transits the curve. I reckon that could be tested using an appropriately weighted firework with the assembly hanging off a lamp post though. That's assuming the SPB is prepared to spend time launching fireworks along curtain rails attached to waste pipes hanging off a lamp post, of course. I quite understand that as serious journalists you may not wish to get paid for such nonsense.
Looking at Screwfix.com, you'd be out ₤1.85 for a 3m length of 32mm pipe, and ₤7.65 for a curtain track with fittings, and that's before glue, so I grant you it's not cheap. With no moving parts other than the obvious, and no split-second timing required, it just might work though...
I have emailed Lester an appropriately simple schematic of something I like to call the Neatly Implemented Plastic Parabolic Launch Enabler.
Paris, because we don't have one for Lindsay yet.
..how about an inner tube from a large tracter or heavy earthmoving vehicle (such as this: http://www.ausbusiness.net/wp-content/uploads/mining-dump-truck-265x245.jpg).
The upside of one of those, (other than its ability to hold a bit of gas), is that it would already have the necessary valves in place to retain said gas once injected....
Well, not when you can get engines designed for multi-stage use off the shelf anyway. To elaborate on that awful MSPaint-derived sketch, the first stage (the bit with the 'pipe-shaped fin', directional nozzle or whatever you want to stick in the bottom) would just last long enough to eject the rocket+sabots from the tube, flip the whole thing to vertical and get it going fast enough for fins to work. Three seconds perhaps? The second stage would provide the main duration of thrust, and any little D or whatever-class engine you could put in the V2 (harhar) as a third stage would just be a bonus.
Detection of stage separation could be made relatively simple, along the same lines of how a jet-ski detects separation of rider: attach a jack lead between each stage that gets pulled out. For the first stage, the jack lead can double as a signal carrier for nozzle servos. Hopefully the guidance system can sense the jacks being pulled out to go from directed-thrust mode to canard mode, to final burn and coast mode. If the spaceplane's going to autopilot itself back to base then you'll need horizon detection anyway, so use that to detect apogee as well and go from (final burn and) coast mode to glide mode, hopefully at peak altitude.
Of course, I'm not the one writing the software for all this.
I am appalled at the designs with wings that depend on aerodynamic effects for lift. Remember that PARIS released at 89,000 feet, well into the stratosphere. There is insufficient air density at that altitude for a wing to create lift. That's why they use rockets for flight beyond the stratosphere. Rockets have fins to guide it through the lower atmosphere, but the fins have almost no effect once it hits the stratosphere. At that point, the rocket basically only has two forces acting on it, lift (the engine) and gravity. It takes careful design to get a rocket with an engine at the bottom to fly. You have to keep the center of thrust carefully aligned with the center of gravity.
So the LOHAN rocket stage cannot rely on wings during the boost phase. It's going to have to be basically a Congreve Rocket, the engine way up at the top, well ahead of the center of gravity. You could put a rocket on the end of a stick, like a bottle rocket, and it would perform adequately at stratospheric altitudes. The only force you can rely on at this height is gravity, you'll need it to keep the rocket oriented upwards.
Once the boost phase is over, the aircraft can basically tumble through the stratosphere. There is no air to provide lift and no drag that can orient the plane forward. It will need a wing design that has adequate lift, once it hits the denser lower atmosphere, and a good dihedral angle that can automatically correct a roll, and a good tail fin to correct spin. But none of those wing surfaces will have any effect at launch height.
IMHO the best design provided by readers is suspending an angled launch platform at the end of a 50 meter cable. This is enough distance to clear the balloon. Look at the wikipedia entry for Rockoon. It shows a photo of a Deacon Rockoon, it uses this design. It's been tested by real rocket scientists and it works. The wiki entry has a link to JP Aerospace, their Rockoon page has a similar design, and shows an actual launch photo.
Of course there's atmosphere up there. A balloon is a lighter-than-air vehicle, thus it requires air to be lighter-than, otherwise no lift.
If there's enough air to hold a balloon up, there's enough air to use for a bit of drag for stabilisation; only a small force is required. Nobody's looking to create aerodynamic lift to hold the rocket up.
Also, the "rocket on the top with no other stabilisation" is a failure waiting to happen: http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy
Flight stabilisation is needed. It's Big Fin or Gimballed Rockets. A rail isn't going to help at all once the rocket leaves the rail.
Nice discussion. There are a couple of failure modes that seem likely enough to warrant fool proof avoidance plans. A vertical launch through the center of a cluster of balloons seems sensible given the craziness of schemes to launch from below the rocket. A system that retards or accounts for the swing of the balloon should be paramount. Look at how much PARIS was swinging. Regarding thrust vectoring, I read the Armadillo Aerospace blog for years as they developed their attitude-maintaining, thrust-vectoring vehicle. An alarming number of sensors fed into a remarkably complex amount of code and it took scores of tries to work it all out. I don't believe for a minute that you'll be able to get software and hardware to work well enough to use vectored thrust, especially as all the sensor inputs, calculations, commands, and reactions have to be done in milliseconds if you're going to get through any significant number of cycles before a black powder model rocket motor burns out. I also think you should use the popping of the balloon(s) as the trigger to launch because if you trigger before the pop by even a little, you'll be throwing away far more altitude than you'll get from any normal sized rocket motor.
Complex perhaps, but I don't think the needs of the rocketry part of LOHAN are all that much. I don't think it needs to go at precisely N degrees from the vertical then fly through a street, stopping at the traffic lights. Simply "somewhere vaguely upwards" would suffice. So maybe launch at 45 degrees and have the rocket guide itself to a point where a few IR sensors are saying "the ground is down there, you're alright"?
Bear in mind that the Vulture 2 will have to be guided by GPS to get back to base, and even with existing autopilots that's not going to be a simple task. That and, well, amateur guided rockets have been done before. It's not too big a stretch to see it being done again for LOHAN, perhaps using some of the same concepts. Plus the onboard footage from a rocket that isn't spinning wildly (as unguided rockets tend to do) would be pretty awesome.
If there is going to be air at the launch altitude, there is not going to be a lot, and it is not going to provide a great deal of steerage, even at top speed.
Yet, at the same time, you want wings for descent control and range.
Concurrently, if they are not going to provide steerage, they are going to provide drag, thus reducing the final altitude.
Folding wings are clearly too complex and liable to failure.
So why not a flexible wing, like a hang glider, with either rigid or inflatable structural beams. ( I like the inflatable idea).
The wing sits inside the rocket casing until max height, then a small explosion, or the inflation of the tubes, blows off a casing and the wing deploys.
Elementary, my dear Watson.
"Folding wings are clearly too complex and liable to failure."
"The wing sits inside the rocket casing until max height, then a small explosion, or the inflation of the tubes, blows off a casing and the wing deploys."
And your's isn't more complex???
Your's would need inflatable structures to be designed, control valves, compressed air storage tank and this all assumes you can pack said inflatable structures so they deploy correctly.
See parachute packing.
A more realistic alternative:
If you have a wing the full length of the body inline for launch, with a spring loaded pivot bearing in the middle and a catch.
When the burn is completed and the wing is ready to deploy, release the catch and wing deploys, simple, clean, effective.
I think you're both right. In the (awful MSPaint) design of mine on page 7, you can see the idea of a spring-loaded pivoting wing. I can see this working, however it may well be possible that you'd get more lift by having full-length spars (possibly wing-shaped at the leading edge), with some thin nylon or silk fabric forming the rest of a membrane wing.
Advantage is a greater wing surface area, plus the silk/nylon would be strong enough to prevent the spars from snapping open too hard or too far and flying off. The membrane parts of the wings could probably be folded like a concertina within the Vulture 2's body until it's time to deploy. Essentially, once opened it would look like two right-angle triangles with the longest side facing forward.
Also, elaborating on rocket guidance: If it's shown that (say) an 80-degree-angled tube will align the rocket alright without any complex guidance, could Lester at least think of a single-axis anti-roll mechanism? Not guidance as such, but a pretty simple-to-implement way of stopping the rocket from spinning like a top and making any video footage worthless. Just one gyro, the feedback from which is used to directly control fins on the rocket. The hardest part would be calibrating the amount of gyro feedback so that you get a very s-l-o-w roll, without over-corrections that would cause wobbling. Basically, not very hard at all and probably within the range of many hobby rocket enthusiasts.
... using controlled fins for Aero feedback, will also not be that easy to set up. Settings that work fine up to 10k would be totally u/s at 80k. It would need to be tested in a low pressure wind chamber, (assuming that you can find one).
Also with all rail/tube launches, there remains the issue of icing up. It is probably not feasible to have heating elements all of the way along. For simpler systems, depending on the time to altitude, you could maybe use one of those Ski hand warmer packs for a particular component.
...a scale model of Scaled Composites' SpaceShipOne, complete with feathering mechanism. That would be cool.
Or, a scale model of the recently-retired Space Shuttle / Orbiter / whatever it's called. That would also be cool.
I was among the first to suggest vectored thrust and completely agree with everyone who said that it will be very hard to achieve, particularly if Vulture 2 has a similar flight-testing program to Vulture 1 (ie none at all). However, it would be cool to try.
Use Fresnel lens (lightweight) focussed onto Peltier junction module in order to split water (carried onboard) into H2 and O2 which is then piped via fishtank tubing into a pair of compressors.
This then fuels the craft in flight, which means that there is no rocket motor and therefore the CAA restrictions should be a non issue.
In the event of a leak it will "fail safe" i.e. the rocket won't ignite.
Once at altitude activate the ion drive using CO2 cylinder filled with argon or xenon as the ion source.
Even standard "black" gunpowder has it's own self contained source of oxygen (either sodium or potassium nitrate). Smokeless powder is Nitrocellulose based. Why do you think a sealed rifle cartridge still fires?
Anyway, you're going about this all wrong. Who needs balloons?
You could take the easy way out and buy Class M solid fuel rocket engines premade and with a proper multi stage design reach 100,000 ft.
But if you are REALLY SERIOUS, how about "rolling your own" rocket motors Mythbuster Style? No, not the Salami and Liquid Oxygen version. Think BIG or GO HOME!
Carbon Black (think copier toner), finely powdered Aluminium (a fine file and a lot of time), Ammonium Perchlorate (better have a liscense) and some latex rubber emulsion mixed in the right (but not disclosed, that you have to figure out for yourselves) proportions is what the Solid Fuel Boosters for most ICBM/NASA designs use.
Add the mixture to a clean cement mixer with a small amount of water. Just remember to make sure that the cement mixer and anything/one that touches it or the fuel, has anti-static protection. (VERY SURE!)
Use an appropriate tube that will contain the pressure, fill with the emulsified fuel and mold a star shaped tapered hole down the center about halfway. Vibrate the bubbles out, orient tube vertically until latex cures. Allow to dry over a significant time in a temperature controlled environment.
Get some high temp porcelain clay and mold an appropriate rocket nozzle that will fit in the end of the tube, fire it in the kiln, allow to cool, examine for cracks and affix with adhesives and mechanical fasteners.
NASA uses big sparklers (literally) to light the Shuttle Boosters because the sparks light the star shaped edges of the fuel evenly. (Very Important Fact, Uneven Combustion is highly undesireable)
Remember, DO NOT UNDER ANY CIRCUMSTANCES RELY ONLY ON THE USE OF RUBBER O-RINGS TO JOIN THE SECTIONS TOGETHER! (From NASA and Thiokol "Lessons Learned" archives)
Voila, cheap rocket engines of any size or thrust you want and no risky liquid hydrogen and oxygen. Obviously, there is a MUCH steeper learning curve making your own and the accompanying risks are (no pun intended) Astronomical.
Make the engines big enough and Vulture II could leave Earth Orbit from a standing start and no balloons would be required.
However, you might want to let NATO, USAF, RAF etc know that a home made, multi stage, ballistic missile with payload, is being launched. For some reason, they get a little touchy about that stuff.
Or if you want to take the easy way out, just appeal to Elon Musk to be the "Topper" on one of his "Birthday Candles".
Oh by the way no state secrets divulged here, only comonly available, somewhat arcane, knowledge. My father (RIP) told me this stuff. He used to work for Thiokol in Utah.
Flame Icon of Course - (Graphic was lifted from warning sticker for Oxidizers, No?)
"You could take the easy way out and buy Class M solid fuel rocket engines premade and with a proper multi stage design reach 100,000 ft."
Or, hang the lot under a triple triplet of balloons and reach truly insane heights due to not having to push through the troposphere and all that pesky weather. Sorta like what I drew on page 7.
Also I think Lester has ruled out home-brew rocket engines, possibly for the same reason he's ruled out inflating LOHAN's orbs with hydrogen. No matter, as you can get M-class engines pre-made. Stick one in the bottom of a fibreglass tube with fins on, light the thing up and watch it go.
And no, that's the warning for "Highly Flammable". The oxidizer warning is a flaming circle, sorta like this: http://us.123rf.com/400wm/202/261/chas53/chas530904/chas53090400023/4656700-united-states-department-of-transportation-oxidizer-warning-label-isolated-on-white.jpg
(excuse the long URL)
With that in mind, the whole launch vehicle could be stuck in a tube with a latex seal on either end. The air inside can be dehumidified on the ground, and when it's time to fire up the engines, the little rocketplane can burst through the latex.
Also, if LOHAN is the project and Vulture 2 is the spaceplane, what do we call the launch platform and the possible rocket vehicle that Vulture 2 sits in/on? I'm guessing "Falcon" might attract unwanted attention from a certain commercial rocketry outfit, but you get the idea.
Our El Reg designers are going to be hard pushed to develop that in a garden shed.
Get the ship to a speed that its control surfaces work (needs some sums here) BEFORE firing your rockets onboard.
Launch at any horizontal aspect (0-say 45 degrees) and let the wings provide the control system (known technology, off the shelf) when speed is adequate.
Use the payload as a launcher (mortar or a launched stack of rockets on a rod).
If launched on a mortar then Lohan needs to be strong enough that her wings dont rp off.
Wings CAN be folded - forward - on an titanium hinge and cross brace (simple design - not that expensive) and spring loaded to snap into place, (they are going backwards momentum will do it and simple construction.)
What size/weight and height is she to fly from, realistically, so that sums can be done?
1) Weather balloons increase dramatically in size as they rise. As the air pressure drops the volume of the gas inside the balloon increase. Some folks don't seem to have accounted for this.
2) Weather balloons are far from rigid or stiff in any way. They are made from latex if I remember correctly. Having seen one or two launched they squidge around and change shape like a soap bubble in the wind. There's an awful lot of solid, round looking balloons in the designs. I doubt any kind of "shaped" balloon will work as you have to cater for the increase in volume with altitude and deal with the inherent lack of rigidity in the envelope.
3) The couple of weather balloons I have seen launched with weather measuring / camera payloads underneath have had the payloads swing around rather a lot. I suspect there will be a pendulum / oscillation thing going on that has to be damped out to get any platform stable. This could be difficult to damp out at altitude if there is little air to react against.
4) I have no idea what size or make of rocket motor you intend to use but a few things are worth bearing in mind:
4.1) It is illegal in the UK to make "explosives"* thanks to the 1875 Explosives Act**. Moving commercial rocket motors around (Aerotech, Cesaroni) which are bigger than 20Ns total impulse or made from propellant other than black powder (i.e. Ammonium Perchlorate Composite Propellant) requires paperwork from the HSE . Estes black powder motors aren't an issue. However I doubt they would give the kind of oooomph you are looking for.
4.2) Commercially available rocket motors have burn times in the order of a couple of seconds excepting Boost Glider rocket motors but these are difficult to obtain in the UK due to not necessarily being Classified and Authorised by the HSE or CE marked (See Placing on the Market, Storage and Transport of Explosives Regulations or POMSTER / HSE). Essentially if the motor isn't C&A'd and CE marked it cant be bought or moved in the UK. Every EU country has different rules on rocket motors and what goes for the UK probably wont be the same for other countries so watch out for designing in something you cant fly elsewhere in the EU. I suspect your best bet would be a trip to the US but the rules there are different again.
4.3) Rocket motors and explosive charges are much more difficult to light at higher altitudes. Igniting solid motors depends on there being air present to conduct heat between the igniter and the propellant. This isn't as big a problem, to some extent and depending on motor system selected, for motors as it is for any kind of loose black powder based ejection charge which can be very unreliable at altitude.
4.4) There are 3 main types of rocket motor:
Solid Rocket Motors use a solid oxidiser and a solid fuel. Probably, for ease of use, best in this case.
Hybrid Rocket Motors use either a solid fuel and a liquid oxidise or a solid oxidiser and a liquid fuel. As far as I am aware nearly all hybrid rocket motors use the former.
Liquid Rocket Motors use Liquid Oxidiser (O2, N2O, HTP(H2O2)) and Liquid Fuel (H2, Kerosene Paraffin, Alcohol) or a Liquid Monopropellant (HTP(H2O2), Hydrazine (NH4))
While high altitude ignition of a hybrid is feasible I suspect the additional complexity and mass limits choice to a solid motor. Liquid Rocket Motors are fine for Space Shuttles and Saturn 5s but not for LOHAN. We have seen that LOHAN does not necessarily function well when alcohol is present.
5) Boost gliders are a bitch to design, build and get to work in the atmosphere at ground level (search YouTube for Boost Gliders i.e. http://www.youtube.com/watch?v=kbsafWNDiLo). They can and do work but they are challenging.
6) Issac Newton: An awful lot of the designs seem to assume that when your rocket motor lights and the rocket glider launches the platform some how stays put. That there is no drag between craft and launch guide and that for every action there isn't an equal and opposite reaction. As a lot of the platforms are dangling beneath the balloons and are necessarily going to have to be designed to be light even small amounts of drag between launch rail and craft will lead to the payload and launch guide being dragged around by the rocket plane. Icing on the launch guide could have to be accounted for. I have seen even small model rockets take the launch pad with them at lift off. Remember that commercial rocket motors are designed to give a fast hard kick in the trousers to a rocket. Not a glider. Not a long slow burn (a la Saturn 5 take off's and the TV show Salvage 1). On a 1m long launch rail a small rocket on a G Class motor (up to 160Ns total impulse) can be doing several hundred miles per hour before it leaves the launch rail. Obviously this depends some on motor selection, design of the craft, drag.....
7) Active stabilisation is tricky and vectored thrust is tricky too. Both are achievable http://www.rocketeers.co.uk/node/420 for example. But there is a significant mass penalty if you are considering it for a "Ballocket"
8) General rule of thumb at ground level is that a rocket has to be travelling at at least 30mph when it leaves the launch guide for air passing over the stabilising surfaces to be travelling fast enough to work. Below this speed the restoration forces on the fins/wings are insufficient for the flight to be stable. Quite how this translates to higher altitudes and lower air pressures I don't know. For passively stabilised rockets launched from the ground to this kind of altitude they will already have travelled a significant distance through the atmosphere during which time the fins will have worked to keep them going upwards and Newtons 1st law will keep it going in the direction the fins pointed it.
*Rocket motors, or rather solid rocket propellants, don't explode they deflagrate (burn very quickly) but for the purposes of the 1875 Explosives Act solid rocket propellants, regardless of their composition, are explosives.
** You can make small quantities for, I believe the wording is, "no useful purpose." This was included to allow the demonstration of compounds that may have vigorous reactions to students for educational purposes. I understand this to mean: mix up the constituent chemicals in the appropriate (small) quantities, tip out in to a loose unconstrained mound, ignite from a safe distance, watch it go WHOOOF, look suitably impressed. The moment you constrain it or use it to do something you are making it for a "useful purpose". You can make explosives if you have a licensed premises (not an easy licence to get) but then you still probably run in to C&A and CE marking to move anything from the point of manufacture.
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One of the main criteria should be to keep it simple!
My thoughts after working my way through the ideas and comments are.
Don't bother with folding wings. Many people have mentioned the reduced drag at that altitude, and it gets less as you go higher. Having the wings and tail permenantly deployed will aid the stability.
Why carry a spaceplane and a balance weight? Might as well make two space planes and increase the chances of a successful flight instead of dead weight. This way you could mount them either side of the balloon via a mesh bag around it, with the bonus that simultanious launches will cancel out the rolling motion caused by firing a single rocket off to the side.
It the mesh bag being loose on the ground when the balloon is small is an issue, small velcro ties or something can be used to gather it up, and will pop open as it expands. The avionics package on the base will keep it upright.
The shape and stability of the balloon shape will be much better at altitude when it has settled and has no other forces on it. Also, the mesh bag with a balloon tight inside it will actually form quite a rigid structure (like an inner tube inside a bike tyre).
There are a lot of valid points about the complexity of a guidence system (even one to fly it bak let alone one that will guide it straight up), and the size and power of the rocket required. I fly RC, but that wont help you much here, but you might want to take a tip from the free flight guys and make it glide in circles. If it flys in a straight line from that height, you might have to catch a ferry to go and get it :-)
I feel like designing one myself now :-)
Good luck chaps!
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