Firstly, is there a specific forum for LOHAN ideas? Secondly, instead of releasing LOHAN at a pre-deteremined altitude, why not rig up a device to launch LOHAN as soon as the baloon bursts? That way you would get maximum altitude...

This topic was created by Joeman.

### Re: Two balloon

Does that really matter all that much?

### Re: Two balloon

If the ultimate altitude doesn't matter then why not tie a firework rocket to a toy a balloon and have it go off at 20 feet? It will have achieved a rockoon type thing.

### Re: Two balloon

No, it won’t — the total burn time will be ten seconds or less. We have to get as high as possible.

### measuring release altitude for launch

As you're intending to release at +27 - 30km 90,000 - 120,000ft we could use the increase in UV radiation to trigger the launch. The incidence of UVC radiation increases at about this level http://en.wikipedia.org/wiki/File:Ozone_altitude_UV_graph.svg so we need a sensor that can measure the mean UV incidence and calculate the approximate height of the ballon. I suggest we mount the sensor on the top of the ballon so it isn't shaded.

### Re: measuring release altitude for launch

The PARIS balloon got up to about 90,000 ft before it burst. Any pre-burst release would have to be considerably less that this to be sure of success.

### Re: measuring release altitude for launch

Can people please *READ* what's been said earlier, before barging in with a suggestion?

There's no way, no how to attach anything to the balloon, except at the neck. No launch platforms, no sensors, no tape holding a rope. NOTHING.

further to the UV measurment idea, as per http://www.who.int/uv/faq/whatisuv/en/index3.html UV increases approx 10% for every 1000m so about 17x higher than at ground level.

### Measure the balloon diameter.

If you know the largest diameter the balloon will get to before busting, you can use this to trigger the release. A length of string fixed at the top of the balloon down one side to a pull release switch fixed at the bottom would do it. As the balloon expands it gets to a point when the tension pulling on the string around the balloon pulls it taught. You could use a grenade pull pin type setup at the bottom as a release mechanism. This way you get to the highest altitude that the balloon can get to before releasing rather than a fixed altitude.

### Re: Measure the balloon diameter.

I think you underestimate the fragility of these balloons. As I understand it you can’t even handle them without gloves, because skin oil would make a weak spot that will cause premature rupture. A string being pulled taut would cut right through the latex as it got fairly high.

### Re: Measure the balloon diameter.

If you know the largest diameter the balloon will get to before busting,

You don't. At least not with sufficient precision to be able to use that as a trigger parameter.

### Why not just use Remote Telemetry response?

Look, Since there is mostly Real-Time telemetry coming from LOHAN; why not use a remote-fire method to launch said rocketplane at an expected altitude, with an Expansion module to act as backup? ASAP / KISS.

### Re: Why not just use Remote Telemetry response?

Who said anything about telemetry being used? That is far from a foregone conclusion, since transmitters take a lot of power which will be exponentially more costly as the temperature drops with altitude. The only really necessary telemetry is a phone to call in its GPS coordinates upon landing, or perhaps a short while before when it’s warmed up a bit and is in range of cell towers.

Laser tape measure. Point at the ground, hack to a trigger at the required distance

I've never seen a laser tape measure that measures up to 40,000 meters

### Two balloons revisited...launch control and maximising lauch altitude

Problems 1) launch altitude control, 2) Maximise launch altitude 3) Deal with problem of premature balloon burst.

Possible solution have two identical balloons with launch triggered by the angle between tethering ropes which form a 'Y' shape with the launch platform. As the balloons expand the 'Y' opens wider and at a certain level triggers launch mechanically or electrically. The launch also is triggered by one of the balloons bursting by the same method (as the burst balloon falls, the 'y' open and also triggers launch. This also allows the possibility of maximising the launch altitude as the system will not become unstable with a single balloon burst. The balloon burst also means that the tension on one of the tethers falls to zero, this could also be used to verify launch triggering condition, avoiding complex circuitry.

### Re: Two balloons revisited...launch control and maximising lauch altitude

Non-starter.

(1) The side-by-side configuration would be unstable. getting the two balloons to rise in lockstep is essentially impossible. (2) The loss of one balloon would set the platform swinging wildly, it would take at least a minute to settle down, and long before that (3) the stress spike on the second balloon will trigger a loss there too.

### Re: Two balloons revisited...launch control and maximising lauch altitude

As far as I understand it the explosive self destruction of a balloon at altitude could damage anything too close and would certainly cause another balloon next to it to burst. They would need to be some distance apart, probably one above the other. Difficult but not impossible to arrange. This arrangement would induce the platform to bounce rather than swing at the loss of one balloon (or set of balloons) which may or may not be better.

### Why re-invent the wheel?

If I only got 30m GPS accuracy, I would throw it in the bin.

Why are people re-inventing the wheel? GPS works perfectly well up into orbit, is cheap, light, low power, durable, flexible, and capable of being interfaced with similar cheap, light, low power (etc) systems like the Arduino, Mbed, PIC micros, in fact anything which has a serial interface.

Adafruit have a \$39 unit which measures 23x35mm and weighs 8.5 grammes. It is not altitude capped, and has an internal data logging capability. It draws a maximum 20-25mA whilst actively tracking. It also supports 10Hz updates.

This is a problem that was solved a long time ago.

### Re: Why re-invent the wheel?

the problem with GPS is that in a civil application the maximum altitude a GPS is specifically restricted to & rated is 60,000 feet http://www.fas.org/spp/starwars/offdocs/itar/p121.htm#C-XV This is because the ITAR regulations conclude that anything going higher must be some kind of missile (not that the North Koreans will get to test this theory...). That leaves only a few options;

1. Altimeter based - reasonably accurate, but as presure falls the accuracy tails off, so its difficult to calibrate, this is probably the most simple to achieve. Atlimeters are normally calibrated to standard flight levels & temperatures, 90,000 feet is quite a bit higher!

2. Ballon burst - accurate, but the causal effect would lead to a very unstable launch.

3. Horizon Curvature Measurement - Good but would require a lot of work to calibrate & computing power etc.

4. RDF & Telemetry - By placing an radio beacon on Lohan and measuring the inclination from two / three ground based positions (separated by a few mile or two) we can triangulate the approximate height. But this will require good two way telemetry to remotely launch Lohan.

5. Light metering / UV radiation - simple to impliment but may be difficult to calibrate accurately.

### Zero-pressure v. superpressure balloon.

After a post in one of the recent article forums, I've been doing some digging about home build zero pressure or superpressure balloons.

I can understand the reasoning for choosing a weather balloon. They are cheap (relatively anyway), easy to obtain, no fuss in getting them back down, lots of previous knowledge to go by.

But from what I can find, for rockoon flights the big boys (NASA and the likes) seem to be using zero-pressure or Polyethyleen film valved super-pressure envelopes. The advantages of using a zero-pressure design are big. The balloon soars to a maximum altitude and stays there until commanded to drop, thus giving you a much larger launch window and a lot less fuss about how to time the launch. (Just use a timer long enough that you can be sure the balloon reached (near) maximum altitude). There seem to be quite a few HAM radio enthusiast using homebuilt zero-pressure balloons for high-altitude flights.

For instance there is this "tutorial": http://diydrones.com/profiles/blogs/team-prometheus-how-to-make-a-zero-pressure-high-altitude-balloon (look in the comments, the author posted the tutorial amongst the comment thread, not the most readable, but it seems a good guide)

The University of Cambridge seems to have dabbled in high altitude ballooning as well, might be worth it to give them a ring. (http://youtu.be/uK80MXHQ5hA)

A variation is the valved super pressure balloon. This design maintains a slightly higher inside pressure, but limits the pressure differential through a spring loaded valve to just below burst pressure. This has the advantage of a slightly more rigid envelope, keeping its shape better in gusts of wind.

### Re: Zero-pressure v. superpressure balloon.

A zero pressure or vented balloon does sound like the way to go. The only downside is that is a lot more work for the SPB and as a casual observer I don't see that as much of a downside at all.

### Re: Zero-pressure v. superpressure balloon.

Having made a few non-rigid sky lantern style balloons out of bin bags, I think I know what kind of idea you're on about with a zero pressure balloon. I can't say it would be masses of extra effort to stick four or six big sheets of plastic together. The only real difficulty will be making sure the edges of the mylar sheets (or whatever you use) are heat-sealed properly so the helium doesn't leak out. Easy enough to test by plugging the neck section and sticking a weight on an air-inflated balloon body overnight. No significant loss == AOK for a four or six hour mission.

The rig can be attached to either a circular or #-shaped frame connected to the bottom opening of the balloon. Make the neck section long enough that a bit of swinging won't lose significant amounts of hydrog^Whelium, and the burst problem is solved.

Deflating can be via one of a number of mechanical or pyrotechnic methods people have already described here (I personally favour a few redundant lengths of fuse attached to the balloon), with the balloon being made of something photodegradable so if the worst happens, you don't have a launch pad cluttering up the upper atmosphere for months.

### Another two balloon idea

I haven't completely finished thinking this idea through yet, but anyway...

The basis of the idea is to use one balloon inside the other, both being partially inflated but so that the sum of their inflations equals that of a single balloon. The release is then triggered by the bursting of the outer balloon, which will be larger and therefore under more stress than the inner balloon. The inner balloon, being under less stress, should not burst and whilst having insufficient lift to maintain altitude, should result in a controlled and reduced rate of descent, at which point Vulture 2 is sent on its way.

Fabricate a short length of coaxial tubing with, at the upper balloon attachment end, the inner length of tubing being longer than the outer. The two coaxial tubes need to be brought to separate inflation feeds at the bottom inflation end of the combined coaxial tube. With both balloons deflated, attach one balloon to the inner coaxial tube and then carefully feed this balloon inside the other, which is then attached to the outer coaxial tube.

When the balloons are to be inflated, partially inflate the outer balloon first and then inflate the inner balloon, the aim being to achieve the same total volume and pressures in the combined balloons as you would in a single balloon.

The thinking behind this is that you start by imagining a single inflated balloon and then ask what would happen if there was an internal membrane separating the inner volume of the balloon from its outer volume? The pressure within the balloon was uniform within the total volume before introducing the membrane and just introducing the membrane should not change this, so the pressures inside and outside the membrane will still be equal. Where it gets more tricky is when you try to factor in the stresses on the envelopes of the two balloons when both are under positive but equal pressure and how the relationship between the pressure of the two balloons will change as they ascend and expand.

I can see two potential issues with this straight away: the risk of the shock of the outer balloon bursting triggering the inner balloon to burst as well, and detecting the bursting of the outer balloon.

I'm envisioning the two balloons being inflated to somewhere between 50:50 to 75:25 percent (inner:outer) so that there would be quite some clearance between the two balloon envelopes, which should increase in absolute terms as both balloons expand and which, I would hope, would provide sufficient safety margin against the shock of the outer balloon bursting triggering the burst of the inner.

As to detecting the bursting of the outer balloon, the best way I can think of is by some sort of shock gauge, although I suspect that this would need to be disarmed until the whole ensemble has reached relatively smooth high-altitude air, to avoid being triggered by low-altitude turbulence.

### Re: Another two balloon idea

I like the idea but I understand the a balloon burst can be quite powerful and would probably burst the inner balloon.

### Re: Another two balloon idea

Yes, that is one of the potential problems I mentioned. However, the outer balloon won't simply collapse when it bursts because it's under positive pressure i.e. the higher pressure gas that was inside it, and in most of the slow-mo films of bursting balloons that I can remember seeing the bursting envelope seems to mostly follow its pre-burst outline and not simply collapse inwards. Here's a youtube link to a good example: http://www.youtube.com/watch?v=ejWf8iXjXZk

If there's enough separation between the two envelopes then it _might_ work, remembering that the inner balloon, being much smaller, won't be under nearly as much stress as the outer balloon.

I'm quite happy to admit that I'm not totally convinced that this scheme would definitely work but it would be a relatively easy and inexpensive experiment to try, starting with ordinary air-filled party balloons and progressing to larger balloons if the smaller experiments are encouraging.

If it did work though, then it would allow a (relatively) stable launch at optimum altitude.

### Re: Another two balloon idea

I agree and if it worked it would be great. However the only way to find out if would work reliably would be to try it a few times. I'm just giving my opinion.

### Ultrasonic Altitude Measurement

Ok another very simple way of measuring the altitude, at sea level the speed of sound is 340ms at 30,000m it is 300ms. Therefor we attatch ultrasonic transducers on a plank 1m apart facing eachother and a simple arduino counter. Transducer A pings at a signal and when Transducer B recieves it it pings back to A and so on. At sea level you should get a signal of 340hz whilst at 30km it will drop down to 300hz.

### Re: Ultrasonic Altitude Measurement

Sorry I should have added that the speed of sound is affected by temperature, so we will need a thermocouple to allow us to calculate the correct reading. But this is fairly trivial, we can program the temperature ratios into the software etc.

### Mechanical Trigger Failsafe

I was thinking of utilising the fact that there'll be tension in the chords between the truss and the balloon just before it bursts and none just after. I was also thinking about those spring loaded tape measures that snap back when you pull out the measuring ribon. You could have some kind of spring loaded system such that there's a chord connecting the truss to the balloon at tension while the balloon is ascending, that will snap back into the truss when the balloon bursts. The end of the chord attached to the balloon could form an electricital contact for the trigger that will make contact with the other... um... contact when the chord retracts back into the truss.

### Re: Mechanical Trigger Failsafe

Chose a spring scale with a range of 1/2 to 1/4 (guesstimate) of the total weight of the truss (incl Vulture 2) so that once the balloon's inflated and the truss is suspended the spring scale will be fully extended and at the limit of its travel, so as to avoid bouncing off the upper stop during the ascent.

Botch a new lower limit stop, at about 1/8 (another guesstimate) of the full range, so that the spring is still under some tension when it fully retracts. Then epoxy an insulated contact onto the scale, beside the new lower stop, and another to the spring scale indicator so that when the balloon bursts and the spring scale retracts it makes a firing circuit.

I think the the idea of attaching anything to the parachute canopy is risky because of the possibility of it interfering with the opening of the canopy. As well as the risks of the canopy failing to inflate quickly at high altitude and of the long release cord getting twisted around the tethers, there's also a risk of it being blown taut and into a loop (think of a fishing rod with only a top eye and no intermediates) which may or may not interfere with its intended operation.

### Re: Mechanical Trigger Failsafe

Sounds good. it just needs the Register Acrynom (I humbly submit "Spring-Powered Automated Near-space Kinetic Emergency Release") and seal of approval before it is unveiled as the tool used to whip LOHAN into her 'explosive climax'

### Re: Mechanical Trigger Failsafe

I like it - how could it possibly fail with an acronym like that.

### Re: Mechanical Trigger Failsafe

Yep, as illustrated, I suspect the line of the trigger release mechanism will get wound round the chord/parachute/whatever, pull taught and lead to premature ejection of the rocket, given spinning seems to be such a problem. A spring-based system is likely to be a safer bet, barring jogging up and down during any violent spinning.

The concept of the parachute giving a tug to eject the rocket is so appealing, however, that I think it should be worked on further. Perhaps the swivel mechanism could be placed above the chute and the trigger chord placed inside a straw to keep it out of harm's way?

### QEX Article "Sensor Package for High Altitude Ballooning"

By coincidence, the ham publication QEX for May/June 2012 has an interesting article titled "A Simple Sensor Package for High Altitude Ballooning," by John Post, KA5GSQ.

He discusses how to normalize the output voltage of the Honeywell ASDXACX015PAAA5 pressure sensor at 100,000 feet, which was one of the previously discussed options.There is a lot more information that might be worth reading. You can download the article at

http://www.arrl.org/files/file/QEX_Next_Issue/May-Jun_2012/QEX_5_12_POST.pdf

### Photocell for launch

The baloon is white, space is black.

When the white goes away and black came along, couldn't you use this to trigger a photocell?

### LOHAN MUST FIRE... Before the balloon bursts...

LOHAN MUST FIRE before the balloon bursts because the balloon and connecting cables will WRAP AROUND LOHAN before it gets off the rod....

-------------------------------------------

I direct you to this video http://www.youtube.com/watch?v=kAhaIDNVyC0

at 5:20 the balloon bursts.

at 5:33 the remnants of the balloon are shown WRAPPED around the truss which held their camera...

at 5:37 you see the horizon at 90 degrees and the bag hold the control circuitry at 90 degrees to the camera... ie. the truss is tumbling...

at 1:31 you see the small chute they had on the contraption to act as a stabilizer during descent...

at 5:55 you see it open and working it's stabilizing magic... the camera is now facing upwards again...

-------------------------------------------

LOHAN MUST FIRE before the ballon bursts because no chute can stop the spin of the truss in a short enough amount of time to fire LOHAN:

----------------------------------------------

at 2:35 ice is shown flaking off the parachute... interestingly the metal can does not have any ice... What materials on LOHAN might ice up?

While this project's chute seems to have immediately stabilized the platform relative to the horizon, from 2:35 to 2:50 we see the a pronounced wobble which surely would cause LOHAN unhappiness whilst leaving the mighty rod...

Oh and one other thing... it is spinning like crazy...

------------------------------------------------------------------------

LOHAN MUST FIRE before the balloon bursts because upon burst the truss as designed will immediately fall forward (nasty gravity) and POINT DOWN allowing LOHAN to either fire straight down or just slide off:

-----------------------------------------------------

I direct you to this video of a contraption which was heavier in front of the camera... http://www.youtube.com/watch?v=ZCAnLxRvNNc

at 4:10 the balloon bursts and the we see an immediate pitch forward because of unequal weight ratios...

The inevitable tumbling begins....

at 4:14 the balloon bursts and the camera which was pointed UP... by 4:17 is pointed 90 degrees to the horizon and at 4:19 is pointed DOWN....

The inevitible tumbling begins....

FORGET THE PARACHUTE DEPLOYMENT GIZMO... I SAY THIS FOR YOUR OWN GOOD

Sincerely

Daniel

### LOHAN MUST FIRE... Before the balloon bursts... I forgot this other example

at 7:40 you see great example of your chute and balloon wrapped around your wildly tumbling near MACH 1 falling LOHAN of death...

Fire LOHAN before that balloon bursts...

### Re: LOHAN MUST FIRE... Before the balloon bursts... I forgot this other example

Uhh, you linked to a video which is only 5:48 long...

### Re: LOHAN MUST FIRE... Before the balloon bursts... I forgot this other example

Thanks... sorry bout that.... eh hem...

At 7:40 you see the balloon and parachute wrapped around the truss carrying the camera, etc etc...

Thanks again...

### Balloon to Platform... twist of cable, string, and rope...

I know the balloon in going to spin and that wind will also cause LOHAN to impart more spin....

But i have been thinking about the spin since watching a number of the balloon videos available.

Would it be worth it to use some form of rotation resistent rope and/or a swivel between the balloon and platform.

If you do just go with a standard twine or climbing rope, it might do a bit of good to pre-untwist it by allowing LOHAN to hang from it overnight prior to launch....

2cents

### Re: Balloon to Platform... twist of cable, string, and rope...

Best to simply use a woven rope (like climbing rope or similar) which has no twist.

### Re: Balloon to Platform... twist of cable, string, and rope...

Any sort of "rope" will be far too heavy, and a 'climbing' quality rope unnecessarily expensive as well.

I've previously suggested Dacron Big-game fishing line - a quick check on e-bay shows a spool of 180lb x 100ft braided Dacron line for £5.11.

### If the pull of the tethering line disappears - fire

Can't you just measure the weight of the truss + the plane maybe once every tenth of a second. If that weight is less than say 10% of the actual weight it would mean that the balloon has burst and the assembly is falling. If the weight stays below 10% for three (or more) consecutive measurements it's probably not just a wind gust but an actual balloon burst. Use the altimeter to only enable this system above most of the weather to ignore a bumpy start.

If that is not enough use the above to prime the system and then wait for the jerk in the tether line when the parachute deploys using the same weight measurement system and then fire.

Use a longer tether line from the parachute than the height of the balloon to prevent it from covering the plane...

### Re: If the pull of the tethering line disappears - fire

"freefall" conditions are expected during accent well before burst due to turbulence.

### Re: If the pull of the tethering line disappears - fire

@imanidiot

Use the altimeter to only enable this system above most of the weather to ignore a bumpy start.

Missed that bit?

### Another consideration.

Another cnsideration.

Has anyone thought of the volatiles that may be removed from the propellant at these low pressures? I’m sure that something will come off, the low temperature will help stabilise things. But it should be considered.

### Do you want your tail up or down?

Looking at the diagram I see that the Vulture 2 tail fins are pointed up toward the truss. Is there a greater risk of damaging them during ascent or launch vs having them pointed down like a Predator drone?

### ISS? Would be briliant..

..if the folks on it could be persuaded to try to 'snap' a couple of piccies. Your target height is 100 kilometres or so, which is about 300 Km below it, and as it does fly over Spain (I think)...Jut a thought...If they have something bettter than a couple of Kodak Instamatics, with accurate timing, they might get a decent shot...

### Power to the rocket motor heater thermofoil

Just reading the roundup article posted to the Reg. If the heater foil for the motor does need power during the ascent, could it be connected using something like the Magsafe connectors to ensure separation at launch? Article on a DIY setup (for a Thinpad as it happens):

http://www.instructables.com/id/E3DYNACRQAET9K6LXW/?ALLSTEPS

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