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 …
... does anyone else feel a bit dirty after realising we've all jumped on a very web 2.0 style crowdsourced project?
You know you love it
If the crowd was predominantly made up of Wile E Coyote and his family, then yes.
Heath Robinson would be proud.
How to decide
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.
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.
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.
Re: Lovely stuff
She flew through the air with the greatest of ease
That ballocket plane on the flying trapeze........
if your going to go with the triple orb launcher it should be named "Eccentrica Galumbits"
That is all
Well that was interesting...
Seems that most Reg readers aren't in fact rocket scientists...
Tim Harris' idea has to be the clear leader, with a simple straight angled launch rail for LOHAN.
Full marks to Shaun Esterhuizen for failing to spell balloon correctly.
Lots of cool stuff
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
Tim Harris FTW
Yup. IANARS, but his design was the closest to what I had in mind; if anything his is better (that asymmetry is rather nifty...)
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
The Torus balloon is the best idea, from a centre of gravity perspective, and from a style standpoint.
I for one welcome our doughnutty overlohan...
Shoot up through
/oo er, missus
A simpler torus
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.
Sounds a bit dodgy
I think "Lohan's Ring" sounds a bit innuendo laden.
We should keep it classy and use the latin instead.
Ever tried a wind turbine on a hot air balloon?
Throw out any of the ideas which use wind force to orient something since the entire assembly is going to be moving with the wind, so there will be no wind force applied on any of it...
Please remove the mandatory title field
Different parts of the balloon have different drag coefficients. -google
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.
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.
Centre of Aerodynamic Pressure
Surely that should be the Centre of Relative Aerodynamic Pressure?
Already had my coat on, the door is now swinging shut behind me :D
Too much is never enough...
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...
Re: Unknown launch attitude
Put horizon sensors on the launch platform as well?
I was liking this right up until the "no hydrogen" part.
Rats - volume correction:
10 metre balloon has volume 524 cubic metres.
You need six balloons of 5.5 metre diameter to match that volume.
(my envelope was having a bad day)
At least we've got one thing clear
namely exactly where everyone who would have gone on The Great Egg Race is now directing their energies.
BTW incase you hadn't seen it recently...
Watch it here:
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.
Looking through all that lot I think it would be simpler to forget about any balloons, launchers, toruses (tori?) etc and leave LOHAN where it is and just move the Earth out of the way instead!
A symbolic gesture
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.
A long thin balloon...
...perhaps with two spherical ones tied at the base?
Now that could be amusing.
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.
You assume that the rocket will make it through the balloon, not snag and catch fire on the rocket exhaust.
Wedged between balloons?
Jason Holloway's idea seems the most... appropriate.
Although we'd have to rename it from Lohan to Eccentrica Gallumbits.
That's eminently sensible indeed. Indeed, perhaps too sensible, maybe the balloon could be modelled on Rui's frock to make up for it.
That was meant to be a reply to Pete 2's post... the excitement must have got too much for me
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.
Maybe the balloon is misleading us?
Perhaps we should ditch the balloon entirely and just use a bigger rocket?
Liquid hydrogen fuelled for maximum hilarity of course.
Testing is underway in Canada!
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.
Static test results!
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.
what's the difference ?
between a piston launcher and a spigot mortar (eg http://en.wikipedia.org/wiki/Mortar_(weapon)#Spigot_mortar)
The piston launcher is intriguing - and this sounds like a great plan to sort out the problem of getting to a stable flight condition.
Also sounds like very impressive building on the truss front.... I'm looking forward to pictures!
They're not entirely different...
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.
With all the concern about launch orientation, I'm just curious, as I don't know anything about model rocket engines. . Is there enough oxygen at 80Km to support a solid rocket motor burn of decent thrust? The direction won't matter much if the engine suffocates.
Yes, there is.
Rocket motors, unlike jets, do not use atmospheric oxygen; their oxidizer is part of their fuel mixture. That’s why they use rockets to fly into space. A rocket can’t suffocate.
Vulture II, not LOHAN
Marks must be deducted for all designs in which the name of the aircraft was wrong. The project is LOHAN, the rocketyplane is the Vulture II. Have some respect, people. This is Lester's baby you be calling the wrong thing.
You're all wrong...
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....
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