Sign Task

[boomtech]

We're flying over. Too far to drive (it would take over a day non-stop to get there...). TSA hasn't been very friendly to our stuff in the past... and some of my stuff is so big that UPS won't ship it. But I think I have a solution now.

[bwy]

I feel like the balloon would reach it's terminal velocity rather quickly, thus it's momentum would be capped for a short enough string length such that ceiling height wouldn't matter. Is this not the case?

I too highly doubt they are using momentum to lift something. More likely, they are just using a really big balloon that they custom constructed (out of mylar or something) to maximize the lifting capacity. The absolute max a balloon the same size as a mission could lift is a bit over 200 grams (and that's discounting any tasks that obviously would take up some volume), so the winning Ohio team is well within that range.

They are definitely using the balloon's momentum.
The balloon will not, in fact, float if you just let it go with the weight. It will sink really quickly. But they allow some slack so the balloon is rising quickly before the string starts pulling the weight.
Their balloon must take up just about the entire thing. Half of the device is pretty tiny and definitely wouldn't cut it.
I used this balloon: http://www.partycity.com/product/camouf ... Set=176252
to lift a little over 31 grams without the momentum trick, which I didn't find out about till the day of the competition.
I also had a bigger one I could have used, that took up the entire device, almost literally-- it was rectangular, and about 75 cm x 45 cm x 45 cm. It only lifted about 5.5 grams more, and I didn't really want to risk having the judges rule it out as being a tiny bit outside the boundaries. Of course, the day of the competition, they're super chill about measuring the box. Just a couple quick checks with the measuring tape, etc.

[haverstall]

When it says the sign must be attached to the bottom of the balloon, I'm assuming they mean the bottom of the actual balloon correct? Not somewhere on the balloon string?

[marty3]

Any idea what the heaviest sign mass was at nats, and the winning score?

[chalker7]

Any idea what the heaviest sign mass was at nats, and the winning score?

Over 4000 points, nearly all of which came from the sign.
I did not see it, but from the descriptions I've heard it was a device that held the balloon underwater and shot it out of the box like a little rocket. It was appealed and discussed, but ultimately found legal.

[marty3]

Any idea what the heaviest sign mass was at nats, and the winning score?

Over 4000 points, nearly all of which came from the sign.
I did not see it, but from the descriptions I've heard it was a device that held the balloon underwater and shot it out of the box like a little rocket. It was appealed and discussed, but ultimately found legal.

Thanks. I was hoping a team would pull that off. I wanted to see it at states and was slightly disappointed. I'm glad it actually happened though. Still, I was expecting they would shoot for 500-1000 g. That would have been hilarious. Perhaps it's harder to do than I imagined, or the best you can do is less than 500g.

[chalker7]

Any idea what the heaviest sign mass was at nats, and the winning score?

Over 4000 points, nearly all of which came from the sign.
I did not see it, but from the descriptions I've heard it was a device that held the balloon underwater and shot it out of the box like a little rocket. It was appealed and discussed, but ultimately found legal.

Thanks. I was hoping a team would pull that off. I wanted to see it at states and was slightly disappointed. I'm glad it actually happened though. Still, I was expecting they would shoot for 500-1000 g. That would have been hilarious. Perhaps it's harder to do than I imagined, or the best you can do is less than 500g.

Apparently one team attempted ~1000 g, but a small mistake prevented the balloon from releasing (but supposedly worked during practice).

[Beard]

After toying with the idea of using water for the last two months, Northridge finally decided how they were going to utilize the buoyancy of water to lift their balloon. Their mission was already constructed with the dimensions of 76 cm (length) by 48 cm (width) by 47 cm (height), and was supposed to use the starting task,the eight highest scoring tasks (the sand timer being the eighth), and finish by using a 26" Transformers balloon to lift a weight in air. But after little success utilizing the momentum technique, the build team of about seven guys sat down and commenced yelling at each other, arguing, thinking, pondering, and contesting various ideas at midnight Thursday nigh/Friday morning. By around 2 in the morning on Friday, the group had dispersed to their various locations designated for sleeping with the idea of building a vessel resembling a bottle rocket from last season. In the morning, after traversing to a hardware store and Walgreens, the three guys of the Mission team proceeded to build a capsule that would fit over a balloon when using a two liter bottle with the bottom cut off, copper plates, and a ton of duct tape. The two liter bottle had holes drilled into it to make sure that no air would be trapped in the capsule, thus ensuring that only the balloon's buoyancy would lift the balloon as all air within the capsule would be drained. A hold was also drilled into the cap of the bottle for this same reason. Next two copper plates were bent to the shape of the two liter bottle, taped together, inserted into the bottle, and taped securely at to the inside. A not yet inflated balloon was inserted into the bottom of the two liter bottle and was then inflated with helium, this ensured that the balloon would take the shape of the two liter bottle, thus making an aerodynamic projectile. A launching mechanism was attached, as was a small sign stating "Northridge C-39", and testing began. A smaller 47" cm tall box had already been constructed to hold any such device should a water mechanism be used in the device. The watertight box held 15 gallons of water, and testing took place in a shower on the third floor of Ogg Hall. The entire process took less than a day to perfect and integrate into the Mission. The sand timer was not used in the device as a motor was necessary to pull the pin that was holding the balloon under the water. So the final Mission had only seven of the eight highest scoring tasks, but when the mass of the sign and attachments comes out to about 390 grams that one task doesn't really matter. There was one touch during the run in front of the National judges (on the circular to linear motion task), and of course some of the water in the tank left the box upon the release of the balloon.

[austinfhs]

That's pretty amazing.

[Littleboy]

congrats to them