Element K: Reflection on the Design Project

Introduction

After our critical design review it's important for us to take all our critiques and suggestions to see what changes we should make in our redesign. It's also important to review the finalist of our categories and compare what set their shoes above ours and how we can improve.

Project Analysis

After testing and use of the shoe we found that the floor was building up dirt and begin to were and tear and accumulated dirt. We decided that after this testing to consider using a rubber gym mat or another high friction floor or mat that is easier to clean than the silicone floor mat. From what we see from the NASA HUNCH finalists is that they used some sort of rubber or vinyl mats. We went with a rubber mat since they are still a rubber material which might not be a silicone rubber. It is a more similar material to the silicone then vinyl so it still has that high friction between similar materials and lower static electricity generation. The rubber mat we were using was a natural rubber. So far we have tested this mat with our variable weight test, harness test, and angle test. While the variable weight test showed a coefficient of friction of 1.7, the harness test (Figure 1) showed significant control while under 1/6 gravity. While this harness test was only qualitative we were still able to get a better idea of how this shoe would perform with lower friction rubber mats. Our angle test (Figure 2) showed that using our shoe the angle at which it started to slip on the mat was 60 degrees, this comes out to be a coefficient of 1.73.

We also found that while on Earth a COF of .5 is a good standard for good friction, on Earth people usually only need a COF of .25 to .3. On the moon this COF would need to be 1.5 to 1.8. So while the test with the rubber mat did not get a COF of 3 which we wanted, the COF of 1.7 is still a good COF to be able to walk. The harness test shows that someone can still walk with this lower friction with only pushing on with 1/6th of their weight.

Analysis of Finalists

The NASA HUNCH Lunar Habitat Shoes finalists showed some common attributes in their shoes and flooring. Most of the teams used a form of silicone rubber or resin. The floor was often a vinyl or rubber sheet. The most common flooring was an electrostatic dissipative (ESD) sheet which takes the static charges from the mat and shorts it to ground. These mats are made of vinyl or rubber and are made to have high traction. One design that was unique was a design that had a design that had sole which folded up. The design seems to be meant to make sure the shoe is always pressed against the foot.

The finalists groups also had unique soles some of them being incredibly different than the typical shoe sole. Our design was a basic design that was designed for durability primarily but also was capable of functioning in the lunar habitats. The other designs included a design of circular extrusions on the sole. This is designed for even support around the entire shoe and parts for the uneven dirty surface to not prevent friction. Other designs include a design with a spring loaded sole of a shoe that partially folds in on itself. This design is to keep contact with the surface for longer periods of time and to allow for uneven surface walking. This allows for the shoe to be more adaptive to the surface it is walking on.

Comparison Between the Designs

While the finalist groups used ESD mats as their flooring our previous flooring material was a silicone sheet that would maximize friction. We changed this to a rubber foam gym mat which while providing a coefficient of friction around 1.7 it also had a tread on the mat which would improve grip in scenarios where dust or dirt would be on the flooring. The finalist groups also utilized hard sole designs while our silicone sole is flexible which provides more comfort and makes the size more universal.

Modifications to be Made

While the flexibility of our sole was helpful for comfort and sizing, we plan on changing our current silicone rubber to one with a higher durometer to be able to increase the shoe durability and stability. This change will lower our friction with the ground but its not feasible to have a low durometer rubber when it's important to have a shoe that is able function under stress and must be sturdy.

The last change we will make would be slightly change the tread on our sole, while the current tread is sufficient we have noticed a dip in the center of the shoe. This is because there is no supporting arches that follow the outside tread across the bottom of the shoe. We would add some supports to fix this dip. This would increase stability and help with surfaces that have dust or foreign objects on them.

Conclusion

The modifications we've made and plan to make, changing out our flooring for a rubber foam gym mat, using a higher durometer silicone for our sole, and changing the tread of our sole will help tweak our design and improve upon its viability as a high friction lunar shoe. While these are our current modifications that we plan to make we will continue to redesign and refine our design until our high friction lunar shoe is made to the best of our knowledge and ability.

Sources (APA)

Coefficient of friction. Global Floor Safety Network. (n.d.). Retrieved March 30, 2022, from https://www.gfsngroup.com/coefficient-friction/

Yo Gorilla Mats. (n.d.). Gorilla mats faq. Yo Gorilla Mats. Retrieved March 30, 2022, from https://gorillamats.com/pages/faq

Finalist 2021-2022. HUNCH Design and Prototype 2021-2022. (n.d.). Retrieved March 30, 2022, from http://www.hunchdesign.com/finalist- 2021-2022.html

Author admin. (2020, February 24). Everything you need to know about ESD matting (probably). Antistat ESD Protection. Retrieved March 30, 2022, from https://www.antistat.co.uk/blog/2017/12/05/everything-need-know-esd-matting- probably/#:~:text=ESD%20or%20Static%20matting%20is,but%20that%27s%20a%20secondary%20benefit