Abstract

Abstract

Home School: Glenelg High School

Project Name: Glenelg Lunar Habitat Shoes

Designers: Andrew Schaefer, Christopher Lewis, Reed Vilar

Problem Statement:

NASA is in the process of creating a lunar habitat on the Moon. In this habitat a team of four astronauts will stay for two months. To help with walking the astronauts will need special shoes that create greater friction with the ground. Since gravity on the Moon is 1/6th of the gravity on Earth, there is a lower maximum static friction. This means that it will take a lot more force to generate the amount of friction that we see on Earth. The problem is that astronauts can only put so much force into their step, so that means the shoes they wear must be able to make up the difference in friction. On earth we are able to get by with around a 0.5µ coefficient of friction for non-slip shoes, but on the Moon the friction of the shoes must be higher, around 3.0µ, to make up for the lower gravity. The lower gravity also causes astronauts to have to change their stride, sometimes taking shorter steps rather than long strides like on Earth to stay upright when walking. This stride change is important because when walking on the Moon you have much more momentum. So these shoes would increase the amount of friction generated between the floor and the shoe in order to prevent falling over or losing balance. These shoes also need to limit the amount of static electricity. Since on the Moon there is almost no atmosphere there are less water molecules in the air to diminish the electrons generated from walking. On Earth the amount of static electricity changes depending on what your walking on and what the environmental conditions are but on average each shoe will generate 10 watts (Science Daily, 2016) and while most of this is turned into heat It's important to limit static electricity generated to prevent sparks since they might cause dust to stick to equipment and also act as an ignition source

Design Statement:

Our shoe has three generic sizes, small, medium, and large, so that it could fit a wide range of foot sizes, while simplifying manufacturing. We used a pourable silicone rubber for our sole because of its high friction coefficient. The rubber material is a two part silicone that is poured into our vacuum formed mold. We made this by vacuum forming our CNCed foam base. The accompanying floor mat is made from the same silicone rubber since similar materials have a higher friction between themselves and generate less static electricity. The sole is glued to the Nomex fabric using a silicone glue poxy, the shoe is made of Nomex for its fire resistant, and strength properties. Our final design works by opening down the center of the shoe where the wearer can slide on the shoe and then secure it by using velcro straps along the gap to tighten the shoe.

Summary of Results:

We conducted several coefficient of friction tests were we tested what was the coefficient of friction between the sole of the shoe and the floor. We used three different methods to find the coefficient of friction. The first test was an angle test which got a value of 5.671, the second was a pulley test that got a value of at least 3.256, and that final test was a varied weight test which got a value of 2.08. These varying values are a cause for concern and requires more testing to get a more accurate number. We also did a test where a harness attached to a pulley from the ceiling would pull 5/6th of the test subjects weight to simulate the moons gravity. During that test the test subject was able to firmly take and hold on the floor and push themselves forward and walk. We also conducted a static electricity test. This test resulted in an angle of deflection only 4.857 degrees, all the built up charge quickly dissipated, and there was no arcing. We also tested the design to see if it fit multiple different sizes and found our shoe could fit people with a male foot size from 7 to 11.

Photos of Prototypes: