Hot Air Balloon 2

Good thing this time we were allowed to use our own materials to build the hot air balloon.

After discussion with our group we had decided to build a smaller sized hot air balloon. The materials are as follows: one small, lightweight garbage bag, one piece of cardboard, some floss strings (only string we could find), two pieces of fuzzy, bendable wires, and four candles.

First, we bent the two fuzzy wires to form a circle and taped the ends together. Next we taped the wire circle to the plastic bag so it would retain its shape. 

Our idea was to make a "basket" similar to a real hot air balloon's. To make this we poked holes in the cardboard to fit in the four candles. Then we taped one end of the floss strings to the cardboard corners and the other end to the bag. This is our finished product.

It kind of looks like a jellyfish.

Anyway we thought our design was going to work because it was lightweight. However, when we lit the candles we realized the strings were too close to the candles. In the following picture you can see that some strings are burnt along the edges. If the strings were burnt, then our basket would entirely detach itself from the balloon. Also, the distance from the candles to the bag was still relatively large. We are positive that if we move up the candles a bit more while having sturdier strings (think yarn) that are farther from the candles the hot air balloon would've worked. We won't really know unless we build another one, but I think Mr. Chung has had enough with all these failures. Anyway, other groups' hot air balloons failed also so I guess we didn't do that bad. :D

Hot Air Balloon 1

With no success to our egg landers, we were determined to make a working hot air balloon this time.
The materials allowed were 10 straws, some tape, a plastic bag that you can cut to your preferred size.
The balloon was supposed to run on a maximum of 10 birthday candles. This was the tricky part: more candles meant more fuel, but they also meant a heavier mass. The trick was to find the right balance.

Our design was really simple. It consisted of five straws joining each other in a shape of a star. The bendy ends of the straws stood up perpendicularly to allow the bag to be taped on. Since our candle holder was quite large (and thus heavy), we decided to use all 10 birthday candles. We cut out small holes in the straws so that the candles can fit snugly in them. Next, we tried to tape our candle holder's perpendicular ends to the bag.

The problem was, the bag was too big (it was a regular sized garbage bin bag). We were running out of time, so we didn't bother to cut the bag into a smaller size and instead tried to tape the whole bag. However the tape wasn't sticky enough. Our attempts were fruitless as the tape just fell off. We didn't have time to test our balloon but it would've probably failed anyway.


To sum it up, our hot air balloon failed, but so did everyone else's. In my group's defence I guess we didn't do that bad. :)

Viewing the Night Sky

The night was chilly and a bit misty, but I was able to see a fairly round moon and several other stars. I was never really interested in the moon, but seeing it up close made me think otherwise. 

This is a picture of the moon taken with just my phone. It actually looks better than that, trust me.

Here are pictures taken with the telescope.

Pretty neat, huh? The Big Dipper was also visible that night, but it was too faint for my phone to capture an image of it. One of the astronomers showed us through the telescope the star Albireo. The speck of light we saw was actually two stars together, Albireo A and Albireo B, but the telescope cannot zoom far enough.

We were also lucky enough to see Neptune, the farthest planet from the Sun. It appeared as a tiny dot, however.

A very faint Triangulum galaxy can be seen through the telescope. Here's what the constellation looks like:

This is from a constellation book that the astronomers had supplied us. I flipped through the pages to find Leo, my horoscope sign.

The brightest stars in the constellation form an image of a lion, but I think it looks more like a dog. Oh well.

Anyway, I thought that the star gazing event was quite entertaining despite the cold temperature. One astronomer even gave us his Tumblr url: http://astrogeoguy.tumblr.com/. Have fun reading through astronomical posts!

Egg Lander 2

Egg Lander 2

With my new group, we have decided to build an hourglass shaped egg lander, with straws connecting each end to form a rectangular prism. It is composed of two identical trapezoidal pyramids with the egg secured in the middle between the two pyramids.

We thought that the hourglass shape was a good idea because it was symmetrical. Once again, we tried to emphasise flexibility of the structure, but we didn't have enough straws left to make a bouncy base. However, we did try to make the surface area of the pyramid greater so it would absorb more impact. The egg holder was the good old straws interlocking each other to hold it in place. The leftover straws were not enough to make bouncy paddings of the shape # but we did use them to connect each vertex of the pyramids to another.

However, one thing we neglected again was aerodynamics. Our structure was already pretty heavy, with 24 straws and a decent amount of tape, and it was in no way aerodynamic. Our structure also failed to keep a perfect shape. As you can see from the above picture, the top pyramid's square was bent compared to the bottom pyramid's square.

I don't have a picture of our egg lander after it's dropped, but to put it nicely the egg broke again. One group that did a similar design as ours had successfully protected the egg during the drop. They had a prism with straws holding the egg in the middle too, but they attached the straws from the edges, not from the vertex, where support was apparently weak. In my group's defence  I can say that our design was pretty good except we neglected aerodynamics and underestimated the structure of the egg holding mechanism. If in the future I ever build another egg lander, I would follow Mr. Chung's advice by making a sling shape egg lander since it uses very little straws and is also aerodynamic.

Egg Lander

Egg Lander

Hey guys. Welcome to my boring blog of what happened to an egg lander we built in class.

The materials we were allowed to use were twenty straws, a sheet of newspaper, and two table lengths of tape.

Within our group, we have decided to build a tetrahedron with the egg in the middle. Now I know this may sound a little crazy. Tetrahedron? What's that going to do? Well look, we didn't know what was going to happen, but there are reasons for our insanity.

1. We have learned in physics that triangle is the strongest shape. A triangular structure (the tetrahedron) when subject to a strong force will only collapse because of material fatigue and not of geometric distortion. It is really hard for a triangular structure to cave in on itself, but relatively easy for a square/rectangle to do so.

2. The tetrahedron also uses less straws to construct.

3. The tetrahedron is symmetrical which is important for a rigid structure. Mr. Chung said that "Do not assume the egg lander will drop a certain way". Since the egg is strapped and suspended in the middle of the tetrahedron, it doesn't matter which side it is dropped on, because the egg would still be smack in the middle.

Our logic in using triangles were correct. However, we didn't do enough to protect the egg. As we will soon witness, the structure survived the impact perfectly, but the egg...not so much.

Woopsies. We kind of knew beforehand that the egg wasn't going to survive, according to Mr. Chung's analogy of American vs Japanese cars. As you can see, the structure barely bent. It was the egg that couldn't survive a two-story-high fall.

I think what we could've done to make the egg lander better was to cover all sides. Having an extra "leg" on each vertex of the tetrahedron may have helped, as it would spread out when the egg lander is dropped, and absorb some of the impact.

We should have also cut up leftover straws into short stubs and surround the egg with them. These stubs would've served as cushioning for the impact, because before the force of gravity can get to the egg, it must get through the stubs first. These stubs also wouldn't pierce the egg when it falls, because the sharp ends aren't touching the egg. 

Finally, I think all sides of the lander should be covered with some type of springy mechanism made from straws.  It will certainly absorb a lot of shock when dropped.

Hopefully we can build a better model next time. I'm still baffled by how college students can build a successful egg lander with ten straws, though.