Balloon Launch Discussion

//it also cuts as well as seals//
I think that is exactly what we want to do unless you are using the overlap as the suspension line. I plan on using fiberglass tapes as suspension lines, run only high enoug on the balloon to distribute the stress. The enemy here is weight. Depending on how wide you make the individual gores the extra seam material can add up and that is weight taken away from your vehicle. Remember this will be a BIG balloon.

John
Thank you so much for that input. I have used the model A400 before in the California desert sampling steam ejected from the oil wells. Some of the low flow well's did not have enough condensables in them to effect this type of flow meter. This is a bellows type of meter correct? It was probably 30 years ago when I worked for Radian at that time doing EPA work for the gov. as a chemist (17 years old) that will get back to what Stew said about condensables in the flow I forgot these are sensitive to that. They are designed to not explode with combustible gas that really helps with Hydrogen.

Stew if we zigzag the flow thru the evaporator that system will work fine to remove almost all of the moisture. I do not know if the condensables are corrosive to alum. any free sodium hydroxide in the condensables would attack the evaporator.
If we had a gas chromatograph or access to one we could determine exactly what was going on with system. We probably need one anyway.

Monroe

For the base system we fly 900 mhz maxstreams for command and control, 2 meter downlink only for backup position, a "spot" unit for post landing site verification and a two week carrier only beacon. Then each mission will is own set of transceivers depending on what is being tested or the project.

The team has left and I need to catch up. Rockoon flight tomorrow.

John
Ohhh. I have been looking at the MaxSTreams thank you. 2-Meter back up makes a huge amount of since. Really appreciate that it will save us some time and heartache and more importantly money. Very best of luck with the Rockoon mission. I would love to see success. I am learning that every mission is really a success as long as everyone is safe and we learn something. We have a great group of guy's that are really putting in the effort and I'm sure any wisdom you share is more than welcome.
I have a small machine shop and small foundry if there's anything we can make for you let us know. That’s really all we can offer. I was wondering if you were heating your rockoon silo to aid in the stability of your propellant. I was told that you have to do that is that true?

Monroe
Team Prometheus

[quote="stew_lilley"]Guys,

Overall we just need a way to cut gores accurately from thin polyethylene, and heat-seal the edges together. I know there have to be some tricks involved with the welding, because as you start joining the seam the shape becomes non-flat and is going to start curling. Plus the plastic is slick, and how do you hold it accurately? How do you join the final seam to close the balloon?

I usually work on the rude and crude side of life. Is it that important to have a pretty balloon? If it is then you need gores cut to a nice shape. If you want a quick and dirty approach just make a cylinder of plastic and seal the ends flat. Think of a great big green garbage bag. Seal the top and fill with gas. I learned years ago when I was a kid (Thats around 45 years ago) that if you put plastic sheeting between 2 sheets of newspaper and then Iron it you will heat seal the plastic. Simple and effective. The plastic can be bought in thousand ft. rolls 6 ft tall. It is used for wrapping items on skids for shipping,. I do not know the sizes but a request to a shipping supply company should give you a good source of plastic film. A kind benefactor that ships items wrapped this way may even donate a few hundred feet for the project for a decal on the payload package.
I do not see a problem building a straight seam welding machine to do the job. The problem will be controlling the sheeting going into and out of the machine. There is going to be a lot of plastic to manhandle. Unless you have a hundred ft long room it is going to be awkward and heavy. Perhaps a roller take up and delivery system will be required. 3 roller reels will be required. two to feed and one to accept the finished product. Plastic rolls will be vertical and the welds will be made on the vertical edge. This will keep wrapping equipment modification to a minimum. New thought. You will need 4 roller reels to be efficient What is the ultimate size of balloon you will be requiring?

Woody
I believe we may have access to a 200ft building! But we do need to figure out how to do the welding anyway I was thinking a device that slides down a long table.
This first one is about 20' long. We don't have enough data yet to calculate the final design yet.

Monroe

Any good Ideas?

What do you run for antennas? For power/weight/$$$ trimming I'd like to drop the output power and use high gain antennas, but worry about signal loss.

MisterQED
Team Daedalus

A 20 ft balloon will be easy to make. Butt the plastic sheet edges together and hold with 1 1/2 masking tape Fold them over and iron it shut. Maybe you will even be able to remove the masking tape, not real sure.Don't worry about fancy gores. Just make a big garbage bag, flat seams all around.
The big boy should be made on some kind of automated equipment to get it done right. I like take up reels to keep it from getting messed up and also for transportation after.

OK, here's a summary of our progress so far. I have made a set of tooling for cutting out balloon gores in a controlled, reproducible way. Imagine a plywood surfboard about 7' long by 1' wide and you won't be far off. Obviously, this is just a small scale prototype intended to test the process and method for making balloons, a 7' balloon won't be too impressive but it has the distinct advantage of fitting in my shop. The bottom table (the thing shaped kind of like a surfboard) is hollow in the middle and has little-bitty holes drilled all around the top, and a fitting on the bottom for attaching an air hose. Basically, you lay down a piece of plastic on it, turn on the vacuum (I'm using a shop-vac), lay down the plywood pattern in the actual shape of the gore on top of the plastic, clamp the pattern down, and then run a knife around it to cut out your gore. I've gotten that far with testing and it works very well. The vacuum holds the slick plastic down but lets you adjust it enough to smooth out wrinkles, it's just like an air hockey table in reverse.

I have started tests on sealing the seams with mixed results so far. Using the wood pattern itself as a guide, I run an iron around the seam, using a card-stock shield to keep the plastic from sticking to the iron. My first test stuck but didn't actually weld together except in a few places where apparently I was going slower. Some more experimentation is in order, but it looks like we are closing in on a viable method. Of course, it will be necessary to make some much larger tooling, and then we have to have a place to put it....

Stew

I like that little machine in a previous post. Instead of making a rail or table to run the machine on just run the plastic sheet past it while it is stationary. It will be a lot simpler. Any chance you could beg borrow or steal one of those gizmos?

Nice work with the reverse air table!

No luck at actually using the machine I mentioned as it is designed to do straight welds and I think you'd have problems attempting to modify it to do turns. Also the machine weighs too much to move easily, so you’d have to run the pattern by it and that would be very hard at full scale.

But...I don't think you should even try, as your way is better, with a little mod.

The piece I didn't have was the way to hold the sheet flat, so here is my idea…

What the machine does is hold each side of a length of two sheets of plastic so that they are flat and stretched taught so that they can both be run up on the heated angled rod so that the two sheets can be pressed together by being stretched tight as they run up on the heated rod to be welded and then cut.

As I said the machine was built to be stationary and make straight welds on plastic that has just come off a small roll and folded. We need a system that holds the two pieces of plastic steady and move the welder. A vacuum table is a great way to hold a sheet flat, now all you need is a way to hold the other side of the plastic outside of where the weld will be to leave a section stretched taught over a narrow gap then another nearly identical vacuum table hinged to allow the two tables to be aligned, the sides of the gaps clamped and then run a moving welder down the gap to weld the two sheets together.

So build two modified versions of the vacuum “surf boards” and then mount them like a shirt press by linking both with a long piano hinge. I say modified versions as the edge of the board away from the hinge has a half inch of the board shaved off. Then another area is added to each board to leave a 1 inch wide unsupported channel with the original cut line running down the middle of the channel. Put a model railroad rail down the bottom channel to power and guide the welder.

MisterQED
Team Daedalus

Sorry, missed crucial part, overall assembly...
From my previous post you take weld two surf board shaped gores together, but then what...
Open the press, turn off the vacuum, flip the new assembly over and fold the top sheet back away from the weld line.
Mount a new sheet on the top board and repeat the welding process until all the gores are welded together.
The toughest part is going to be designing the boards so that the partially assembled balloon can be folded flat and away from the weld line so the next weld can be set up.
The final weld will also be tough, but I think it will all work and leave you with a spherical balloon folded flat on all it's gores ready for inflation.
This system is scalable for any size balloon.
Did you think of peg board for the vacuum table?

Also an inflatable tube on the outside of the weld could actually draw the plastic even tighter if that was necessary.
I'm going to write this all up with illustrations on my new site, if none of this made any sense.

MisterQED
Team Daedalus

QED
Hey, that sounds interesting. I'm very busy at the moment and I’m leaving for California day after tomorrow. I would love to see that and will put some links around for you. Thanks for sharing your ideas with us! We are sharing ours in the hope that others can do what we have done or improve on what we have done.
We all have to get going into space and near space for this to work and our best bet is to show the lay men that there really is hope for dreams of exploration of space for everyone today! If we all start building the things that go into near space and beyond we will get better at it. If you build it they will come, faith can move mountains (but you have to bring your shovel!) Rome wasn’t built in a day and nothing worth doing is ever easy! If we do a little work every day we get a little closer to getting there!
Join us! or start your own Team! do something higher, farther, faster, cheaper, easier, better. Anything! CLICK your mouse right here: http://www.teamprometheus.org/ if nothing else and that will help! Tell another person you are interested in space exploration and watch the look on their face!

Monroe
Team Prometheus

QED,

> Open the press, turn off the vacuum, flip the new assembly over and fold the top sheet
> back away from the weld line. Mount a new sheet on the top board and repeat the welding
> process until all the gores are welded together. The toughest part is going to be designing
> the boards so that the partially assembled balloon can be folded flat and away from the
> weld line so the next weld can be set up. The final weld will also be tough, but I think it will
> all work and leave you with a spherical balloon folded flat on all it's gores ready for inflation.

That's pretty much exactly what I was thinking. You could assemble the balloon on the table one gore at a time, and the two being welded will lay flat against each other, although the rest of the balloon will assume a curved shape that will get increasingly awkward to deal with. Even with the final weld the two pieces being held should lay flat. Although, I actually hadn't thought of using another air table as the top, I was just using a flat pattern and clamping it shut. For more permanent/better tooling that would definitely be the way to go. It took me one afternoon with a jigsaw, drill, plywood, and wood glue to make the table, it's not particularly hard to do. You just need a bunch of clamps to hold it as the glue dries, or else screw it together instead.

Pegboard might have been easier than drilling about 80 3/32" diameter holes like I did, but one problem with pegboard is that the large holes will cause you to lose vacuum badly if a few of the holes aren't covered by the plastic. I chose the size and number of holes so that the total cross-sectional area of all the holes roughly equals the cross-sectional area of the hose on my shop-vac. It worked out nicely with 3/32" holes drilled every 2" around the perimeter, there aren't any holes in the middle. That way you still have good vacuum while you're lining up the sheet and the plastic is only covering some of the holes until you align it and get it smoothed down.

The construction was just three layers of plywood, a top, a bottom, and the middle hollow but with a plug in the middle to keep the whole thing from becoming concave when under vacuum. The holes are about 1/2" inboard of the gore pattern line, but I wish I'd but them closer, there tends to be a bit of wrinkling right there. I'm going to try to attach the pictures, we'll see how this turns out....

//You could assemble the balloon on the table one gore at a time, and the two being welded will lay flat against each other, although the rest of the balloon will assume a curved shape that will get increasingly awkward to deal with.//
No, and that is why this is so exciting. The gores are flat and will stay flat as long as the sheets are not separated, but since we can only have two sheets meeting at the welder, we will fold the ones not to be welded in half lengthwise.
Seem weird? Try this...
Take a some paper and cut 6 small identical gores. Now take 2 and "weld" them along one edge with a couple of pieces of tape.
Now flip them over and fold the top gore in half lengthwise.
Now lay another gore on top of the other two and "weld" another edge with some more tape.
Continue until all the gores are "welded".
What you should now have is four gores folded in half on one side and the last two as the top and bottom gores flat and welded at one edge. Now hold by open end and blow. The balloon should inflate into a nice round balloon.

MisterQED
Team Daedalus