The matter of our LOHAN's substantial globes has kicked off a right old debate among you, our beloved readers, as rival viewpoints on just how to launch the Vulture 2 aircraft from beneath helium-filled funbags battle for our attention. Click here for a bigger version of the LOHAN graphic To recap, we need to work out just how …
I'm sorry I don't have anything to add to your plans, for I am not particularly proficient in manual tasks nor in practical maths and physics.
However, should you consider implementing the whole lot as a computer simulation instead, preferably one running on an 8-bit vintage CPU, then I'm your guy.
I don't know how to help with your question, but I do have a thought about the launch platform - watching videos of all those who have sent balloons to "near space", one thing is particularly clear, and that is it's a VERY rough ride up. It really wouldn't take much to rip something with a 2 metre wing span off a launch platform unless it was really firmly connected. And if it's really firmly connected, how exactly do you break that connection to launch?
Also, with the rapid (verging violent) spinning you see them doing, even in low oxygen/high atmosphere, you really couldn't guarantee a 5 degree launch angle would clear the balloon. It's just as likely it'll be spinning as the launch occurs and the rocket will fly straight into it.
It's a really, really tricky one.
REALLY wish good luck for this - can't wait to see it!
Re: Launch platforms
Yup, it is a rough ride, and the wind is a real problem. Agreed about the the launch angle, so we need to find a solution which will guarantee the Vulture 2 clears the balloon.
Difficult to come up with any guarantees when it is going to be hard to predict the relative positions and attitudes of the balloon and the rocketplane. Not unimaginable for the balloon to be several degrees offset from the plane in the direction of the launch.
Launching near (or below) horizontal would obviously work but I guess one of the aims is to attain maximum altitude. It's a bit like the Douglas Adams trick to flying - you want to aim directly at it and miss. It seems early rockoons did just that bar the actual missing and just spurted straight through the flimsy fabric - simple and direct if a bit messy but there's no way your wide load will achieve the required penetration.
Would be much simpler to just blast your rocket straight through LOHAN's doughnut (or pair of funbags as the case may be) but then you'd need folding wings and that just suggests a bloody mess - if you're not rigid to start with then there's timings and mechanics to consider and your chances of a flop are magnified.
Why not simply drop Vulture 2 off the balloon on command. Your balloon will float up, Vulture 2 will drop a sufficient distance to clear the balloon and then fire its motor, and you can use the control surfaces to get Vulture 2 flying at the right attitude....
If you drop it off the balloon, you don't need a large distance between balloon and payload, and you don't need a counterweight.
Now about the choice of helium over hydrogen.....
Then why launch upwards, at all?
Your last balloon reached 89km. Solid fuel rockets would give, what, in comparison to that? Another couple of hundred meters?
Launch the thing sideways for maximum cross-range velocity and best glide, when the inner atmosphere is met with.
Make that 30km, but still...
Still begs the question
That sounds really sensible
The only difficulty with that suggestion is making sure the plane doesn't tumble when it released, but it sounds relatively simple and would avoid too much spin damage on the way up.
That was 89k feet
So, 27km or 196 brontosauruses. And given that a decent rocket will easily reach 5km when launched from the ground (where air is much denser, so more energy is wasted to drag), it could, in my estimate, add several tens of km's to that.
Clearing the balloon isn't the problem...
There are a couple of ways to do this...
1) connect the aircraft to the balloon at the center of its mass. When you drop it, it should go in to a normal, 'flat' glide path. Delay, ignite the engine and then after a second delay you alter the control surfaces in to a climb. You should be clear of the balloon. (Someone says that the kit to do this exists already.)
2) You drop the aircraft with a weighted tail so that the aircraft drops tail first. (like a tail first stall.)
After a calculated delay, you start the engines which also removes the excess weight on the tail.
(Dry ice maybe?) This should launch the aircraft at a high angle but it should miss the balloon.
3) Look back at some physics of a rotating arm and the atlatl. At launch the arm and aircraft are parallel to each other hanging straight down. At launch, the arm swings the aircraft on an arc. You can calculate the length of the arm based on the size of the balloon. You can determine the launch point and use a small explosive bolt to release the plane from the launch platform. The engine ignites some time after detaching from the launch arm.
The key to #3 is that you need to have a strong flexible arm. My suggestion is a graphite pole like you see in a golf club. You also need an explosive bolt to aide in the release. And you'd have to deal with the timing of the release. (mercury switch or something...)
This allows you to have 1 balloon and a relatively simple launch platform. Also easier to test the components like the detaching bolt, and also ignition tests on the engine. You could also preset the launch altitude too.
But what do I know?
I'm not a rocket scientist. :-)
Would it be practical....
To plant a charge/valve of some kind ON the ballon, have that charge/valve detonate at the proper launch altitude and have LOHAN fire its engines a split second after the detonation of the charge/valve? It seems to me that the ballon would immediately vent all its gas at PARIS-launch altitudes, contracting to nothing and clearing the way for LOHAN to launch without the need for a boom and counterweight. At the same time, the parachute would barely deploy in the thin air at that altitude, so LOHAN would fly upward past the now tiny balloon and partially deployed chute.
The trick would be making sure that LOHAN went upwards after the ballon goes pop, but I imagine there is some kind of gyroscope or something that can assure that.
Black helicopters, because I design those for the UN, oil industry and the global investment banking cabal in my off-time. Wait...did I just post that on an open forum?? Damn!!, now they'll assign me a single digit number and pack me off to the village!!
Cant you just pop the balloon as soon as you have ignition?
Yeah, I did correct the altitude snafu: I typed without thinking.
However, your assertion about getting 5kms from the ground with a 'decent' rocket... Well, it's true, you can do it, but you're actually talking about something like an Aerotech M1550 Redline, or similar - which is a VERY decent rocket.
In fact, it's the most powerful type of rocket licensed for civilian use in some countries; and you launch from solid ground (i.e. not a balloon) to get over a mile of altitude, using a proper rocket shell (i.e. something capable of sustaining 8-12Gs of acceleration all the way). Take a look at the videos of Steve Jurvetson (of venture capitalism fame), to see what a real 'mile high' rocket looks like. You cannot launch one of them from any kind of balloon.
The Register will certainly need to be something like an ACPC-fueled burner, to even ignite, in a near vacuum - and Aerotech are a likely candidate, to provide such a charge - but the actual rocket or rockets are going to be nothing like on the scale of a Redline. It would tear both the plane and the balloon to shreds.
putting the launch payload at the top of the balloon and having a stabilising weight at 15m below it?
Like this? http://www.clicknetworks.co.uk/balloon.png
Please forgive the crudity of my model, mspaint isnt my storng point.
payload on top
Is that even stable?
Maybe the nearest aerodynamicist can put me right, but wouldn't a weight on top and a weight on the bottom just mean that with the slightest disturbance the balloon rolls over until the two weights are more or less horizontal?
No, they will arrange so that the center of gravity will be below the center of lift, which is not necessarily horizontal.
But the balloon is not stable enough to do that. If the weight on top shifts or the entire setup starts to lean over because of wind, the balloon will try to pop out from underneath, amplifying the shift.
A shorter launch boom and...
... some sort of spirit level-type device (mercury switch?) on the launch arm.
The launch arm will presumably see-saw around, and the exact moment of ignition should be set to only happen at an instant when the launchpad is tilting out from the centre (i.e not towards the balloon.
Cut the string at a predetermined point
Could you have the string to the ballon cut at a predetermined point (either timed, or by pressure - bladder expands an closes a pair of scissors or something!)? Then have a 5 second delay for the ballon to shoot off by itself, and then launch?
Obviously you'd need to shape / weight the payload so that it fell in a stable way? How about an inverted cone of card with a weight in the end?
...suspend the payload from the bottom to keep balloon upright. Rocket, fairing, and launching platform perched on top.
The big challenge to this approach, finding an attachment method that accommodates the expansion of the balloon as it ascends.
Maybe a mesh/string outer covering with the latex envelope freely moving inside. On the ground, the payload would hang well below, as the balloon expands, the payload would be drawn closer to the bottom of the envelope.
Beer makes it clear.
Could you not...
...could you not have the balloon under a cage of some-sort, with the launch platform atop it? Then use a counterweight to keep the balloon the right way up?
That's what I was wondering...
I'm unsure of how well it would work, but if the idea is for the LOHAND to get off without damaging her airbag, maybe she should be on top? Then again, if the ride is to rough, she may get smashed before she gets high enough...
...you know, I bet discussions about this project are VERY interesting to listen to.
Does it have to be one balloon?
Why not three balloons, arranged in a triangle, with LOHAN attached in a framework between them?
...placing the platform _on top_ of the balloon?
are anything but stable, rather fragile, and increase a fair bit in size between ground level and launch altitude.
Once you get around those three factors, a platform on top becomes viable.
Long dangly; launch a couple of degrees off vertical
Long dangly distance between payload & rocket - say 100M. Launch the rocket a few degrees off vertical to miss the balloon, say 80 degrees.
You'll need to launch off of vertical anyway as you need to move to orbit (OK, you're not going to orbit, but think big:-)
As the payload is pretty light, could use fairly lightweight line. Could have a stiff launch pole to ensure it goes in a straight line when you light the blue touch paper.
Would it be feasible to hang LOHAN from the balloon using a short line (to minimise dangly-type problems during ascent), which at the point of launch is cut, allowing the launch assembly to drop, unreeling a longer line (your 100m sounds quite sufficient), the end stop of which triggers the engine ignition, with a few seconds delay to allow the launch assembly to stabilise vertically again. As always, the problem is keeping the mechanism from icing up.
Just a quick thought.
If the plane was rotated by 90 degrees could you not knock the wingspan from the boom lenght?
Submitted a design
Inspired by equal parts Miss Lohan, Monty Python sketches and excessive caffine.
Keep it simple, shirley
Just release the rocket and allow it to fall for a few seconds before igniting the rocket. The chances of hitting the balloon - now rising faster - have to be pretty remote. Much lower in fact than the complicated multi-balloon/swinging arm contraptions simply going wrong.
Assuming that both balloon and rocket are in the same air stream, most likely they won't travel horizontally at the same speed. Ergo, after a few seconds the rocket will be clear and bingo!
Also gives you a chance to design a rocket that will fall in a vertical attitude but still glide down once the rocket propellant is all used up.
I was thinking this approach as well..... have a 2 stage launch process, where the bursting of the balloon (or the altitude release mechanism) allows stage 1 to freefall.
Stage 1 has a simple parachute or wing to make it fall vertically.
A few seconds later, stage 2 (the LOHAN rocket) fires.
By this time, it is well clear of the balloon, and the launch platform is vertical.
why not build a floating missile silo?
Have the whole payload, including the vulture 2, sit in a tube suspended between 3 balloons (for stability). you can have the payload at the bottom for the whole way up, keeping the center of gravity in the right place until it blasts off. You could even mount a camera to the outside of the tube to get a very nice view of the launch.
seems good to me
This was the answer I was thinking of, I suspect you will need folding wings though
The best counterweight
... would be another space-plane.
Not only does this double your chances of success (and the cost) but you don't have to worry about the effects of a counterweight sized thing plummeting to earth in the even the balloon's parachute doesn't play by the rules.
Plus, if the two planes' engines don't fire exactly simultaneously you have a nice bit of diversity in the trajectories.
I like this
and not in a facebooky way, but in a real way - and it doubles the chances of finding some remnants too :-)
No reason LOHAN couldn't handle that, I suppose.
A horizontal launch?
Would it be possible to have a horizontal launch, with the spaceplane having crude control surfaces and guidance that can orientate it into a vertical climb within a few seconds of launch?
The horizontal spar and especially the counterweight
will add a lot of weight.
What about taking a long boom hanging down from the balloon, with the plane at the lower end of it. Halfway down the boom is a hinge point created from a bit of rope (a real hinge would ice up at altitude). A ring or disc just over the hinge blocks the lower end swinging up past right angles respective to the upper part. The plane hangs horizontally underneath the lower part of the boom.
As the plane launches from the balloon it should initially stay attached to the boom which wil then cause it to swing from horizontal to somewhere near vertical, at which point the ring/disc blocks the boom from swinging further and the plane separates.
The tricky bit is designing the attachment so that the plane is pretty securely coupled during ascent, holds during the swing, but separates easily once the hinge hits the stop.
This idea is interesting, I think. But did you confuse "horizontal" and "vertical" in there somewhere?
The "horizontal" and "vertical" refer to the attitude of the plane, not the boom
Since the vehicle is a space plane it presumably has wings and some means of roll and pitch control. Why not simply launch it at 45 degrees (or possibly less) from vertical to clear the balloon envelope and then pitch to vertical? You could either use an accelerometer to determine time to pitch up, or simply do it on a timed basis. Experiments at ground level might be useful if you've enough dosh for the rocket motors.
Unfortunately I think this is a bit more complex than they're going for. I could be wrong, but to do what you're proposing you'd need hydraulically controlled wing flaps, etc.. I think that's probably outside the scope of this project.
It'd be great if it wasn't but.. yeah :) This one strikes me more as a 'fire at the sky and see what happens' experiment
No, all you need is a couple of micro servos available from any radio control hobby shop. I'd suggest a delta design with control surfaces configured as elevons to save weight. Keep the servos inboard in the warm and use appropriate pushrods.
Stabilising drogue on the main payload and delayed launch.
Nothing wildly sophisticated, just a small parachute or a l-o-n-g ribbon.
Release the main payload as a single lump and deploy the drogue a couple of dozen metres *above* the desired launch altitude.
Deploy Vulture 2 (with intrepid Playmonaut) a few seconds after seperation when the balloon is well out of the way and the payload has had a chance to (more-or-less!) stabilise itself under the drogue.
Optionally jettison the drogue (to avoid the main payload module drifting too far) and then deploy the main 'chute later as per normal for recovery.
Yes it's a little bit more complicated than just lighting the blue touchpaper while suspended from the balloon and "wastes" a few metres of altitude but I reckon it's going to be simpler, lighter, and more compact than any of the alternatives which have been mooted so far and no more complex than some of the stuff which people are already doing with multi-stage rockets in amateur rocketry.
3 balloons on the points of a large triangular frame/ring, with the vehicle slung centrally slightly below? Launch LOHAN through the ring fnarrr!
hang it out the side...
Something like this...
Obligatory use of sticking material, obviously (and it might even work!)
If spinning is an issue, a few lightwight hoops holding the three suspension ropes (red and green) wouls stop them twisting.
the line supporting the launch rail will always ensure Vulture 2 points a little outside the envelope, no matter how much it inflates.
what about a Parabolic Missile Slingshot Launch
or PMSL? Vulture 2 is held *horizontal* under the balloon at the end of a 5 and a bit m long lightweight pole which is hinged at the balloon attachment and with the Vulture set to detach from it once it's vertical (a simple switch tripped by contact points on the pole and balloon at the hinge would be an easy way to trigger the relay).
If you want to really try and be clever, you could fix some extra booster rockets to the Vulture end of the arm to assist in the Slingshot so Vulture 2 is already doing a decent rate of knots by the time the pole gets to the horizontal.
One possible issue would be in high winds as you get higher, the pole could be flung around a bit, but having extra weight (or the main payload) suspended from it to be dropped away before launch could be a solution.
this isnt the title you are looking for
You mean like some kind of inverted trebuchet? Or use an actual inverted trebuchet with the main payload as the counterweight in the system? Trebuchet assisted ballocket! Now were talking!
^ Mad Scientist
The answer is in the question.
"Call the total 5kg maximum"
Given that the counterweight must either equal the weight of the spaceplane, or be on a far longer boom itself (adding weight both in the length of the boom and the increased need for strength in same) the answer's there.
If you can't see the entire spaceplane assembly clocking in around 2kgs or less (allowing a kilo for the boom, other bits and some contingency), this plan's dead in the water.
 i.e. Glider bit, rocket bit and retention / release mechanism.
Oooooo Oooooooo Ooooooooooo
Place plane inside Balloon...
Bit of elastic band type tethery stuff to hold it in place and give it a gentle ride up. Sums to be done so the ones connected towards the top carry the load and do not distort the balloony thing too much. Added lump of something underneath to help out. [with cameras and shit for extra piccies and stuff]
When it is time to launch.... Cut the front elastic band and, if that does not burst it in the right spot, get PlaymoNaut One [Two] to smack a .22 round up the top end of the Balloon.
Now your Balloon explodes from the top and the cunningly placed tethers assist in removing the latexy stuff from the vertical launch area whilst giving upwards impetus.
4.03175624517 milliseconds later the rockets fire burning away the tethers and 'up she goes'.
I'll just pat myself on the back whilst you go an implement it.
+/- one MS
BOFH rule #372: Always state results with three or four more digits of precision than the original data.
A pint for you, mate.