June 17, Wednesday

In an attempt to save some time, we scavenged 3 lightweight GS-9018 servo motors and an Arduino Nano board from the MNT lab and tested them out. A 4 x 1.5V battery pack was found to power up 1 servo, but we had to connect and program all 3 motors to see if it can power up all of them at once. However, the servos were unable to perform as what we had programmed them to. It is of no surprise as the servos left in the lab by others are usually old or broken.

The axles for the squid’s legs that are supposed to translate rotational energy from the servo to the non-segmented legs were printed out too and we attempted assembly for one of the legs. Axles were chosen due to their non-slip properties. The usage of a universal joint allows rotation to be translated to different planes since the legs would be arranged in a split hexagonal shape. Both designs are inspired from the parts in Lego Mindstorms, a robotics kit, that were found online.

 

In order to calculate the amount of helium needed to lift our balloon, we had to take into account the mass of the balloon, which was still an unknown at the point of time. We used Archimedes’ Principle to come up with a simple relationship between the mass of the balloon and the volume of the balloon, so as to come up with an estimate of the volume of helium required to keep the blimp at neutral buoyancy.

 

After this, we needed to decide on a shape for our blimp. Initially, we wanted to emulate an ellipsoidal shape for our blimp as it would logically be streamlined and suitable for flying. However, we soon realised that calculations with an ellipsoid would be inaccurate as inflating a Mylar balloon would likely not result in a perfect ellipsoid; there is likely to be a limit to how much it can be inflated by.

We found papers which demonstrated the estimated geometry of a Mylar balloon, and that it actually has a ‘depression’ on the top and bottom of the balloon. The papers concluded that there is a numerical constant that relates the deflated radius to the inflated radius. Hence, this piece of information helped us to estimate the volume of a Mylar balloon using the deflated radius (i.e. the radius of the piece of Mylar that we would cut out)