This project was a long-winded process of creating and testing a vehicle that would efficiently drive on Enceladus, and now, it is finally complete. This is my chance to share with you all the results from our vehicle in detail and how we can improve upon it next time.

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Please grab yourself four bags of flaming hot cheetos, two grande double sugar & cream lattes, and a pair of blue-light glasses in order to strap yourself in for some heavy-duty reading.

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What are we trying to do?

In this project, we were tasked with designing a vehicle that is able to travel on a specific moon within our solar system. In order to understand our problem, we researched and empathized during the start of this project, which you can read and explore in further detail here and here. Eventually, we selected Enceladus as our home moon and built our entire project around that while keeping Enceladus at the forefront of our design.

From this research and empathizing, we were able to build our definition statement: How might we efficiently transport 4 people and supplies a distance of 10km back and forth across the icy and uneven South Pole of Enceladus, while avoiding geysers and moving crevasses?

What’s the point of the test?

At the start of this project, we were tasked with testing and calculating our vehicles for their respective energy efficiency. This is the point of conducting the test, so that we may observe and get data through the results and conclude whether it was efficient or not and how we may improve next time around.

Energy efficiency is basically a measurement of how little energy is wasted in an action and is calculated by the energy output divided by the energy input. In our case, the energy output of this vehicle would be the kinetic energy at the end of our test. This means that our energy input would be the potential energy in how we power our vehicle (battery). This is the formula that we used in calculating our vehicle’s energy efficiency later on in our data analysis.

Key ideas to remember about energy:

• Energy is measured in joules (J)
• Energy is neither destroyed nor created, only endlessly transformed from one form to the next
• Kinetic energy is the energy of movement
• Potential energy is the amount of energy that could be exerted
• Energy efficiency is energy output divided by energy input

Through the test, we hope to learn how to improve on something like this in the future and increase our general knowledge and experience with completing the entire engineering design cycle.

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Our final solution!

Overview

In the end, we were able to successfully build and test our vehicle, which our design I will outline and explain in detail here.

As seen above, the 3D CAD (Computer-Aided Design) models of our vehicle are fitted out with:

• Rubber Tread Wheels
  • These wheels have rubber bands wrapped around them in the real model. This would simulate the tank treads that we originally planned for to gain traction on the actual Enceladus vehicle.
  • This is because everything needs some form of friction to move and hold on to. The reason track shoes have spikes on them is to better dig into the ground and give them that push that they need to run faster.
  • Because we need to hold on to our testing surface, we designed this wheel to accommodate rubber bands and give us more friction.
  • The axle hole could also be seen in the middle of the wheel here. This was created so that we may fit this onto the motor axle.

• Chassis
  • This chassis was designed to withstand the harsh conditions and temperatures of Enceladus while keeping our definition statement and constraints in mind from the empathy phase.
  • It features three main parts:
    • Lower hull
    • Upper hull
    • Cockpit

• Motor Spine + Mount
  • Because we didn’t have as much time as we would have wanted to design our motor mounts and spines, we ended up opting for a motor spine + mount that we would attach to the bottom of our chassis. We understand that this is definitely not the best solution and that we probably should have just integrated this into our lower hull.
  • This part of the vehicle creates a simple connection to the bottom of the hull and has a nice fit for the motors from the motor mounts.

One thing that is missing from all CAD designs is the M3 screws. These screws and nuts have a diameter of three millimetres and are what we decided to use in order to build and assemble our vehicle. We explored other options such as hot glue, or tape, but quickly realized that those had a more permanent effect, and adapted the CAD designs to accommodate the screws.

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Here was our final product that we were able to build and use to test:

As you can see in the picture, the upper hull and cockpit were not fitted onto the vehicle. When there was a big blockage and delay in getting the parts out for 3D printing, we realized that these two are not essential for testing the vehicle and let other more important parts print first.

This follows a concept called Minimal Viable Product, first coined by Eric Ries as part of a business methodology called Learn Startup. This concept basically says to do the least amount of work required to the point that the customers can use and test this product in order to get data and feedback. This is an important concept for us to follow because we have to keep in mind that our end goal is testing energy efficiency, and we have to realize the path of least resistance in order to get there.

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Procedure & Logistics of Testing

In the test, we have to simulate a surface similar to one on Enceladus, our target environment. After research, this surface is one out of water ice, frozen and hard. We were originally going to just use a big slab of ice but quickly realized that this would not be the optimal set-up since the school does not have a big enough freezer. Of course, in an ideal world, we would have access to an large ice slab to most accurately simulate the surface of Enceladus, but we worked with what we got.

The software that we used for this test was Logger Pro, a data analysis tool capable of determining the speed and duration of each trial; however, with this method, a recording of the trial has to be recorded and later uploaded to the software, which is outlined in the procedure below.

Procedure

1. Place mirror on flat ground
2. Set up tapes A&B 30cm apart for Logger Pro
3. Set up a birds-eye view camera for video analysis that encaptures the entire experiment area
4. Line the back of the wheel on the back of the vehicle with the back edge of a determined starting place (marked using tape from step 2)
5. Connect the motors of the vehicle with the camera recording
6. Let the vehicle travel until the back of the wheel is at the end of the meterstick
7. Repeat steps 5-7 three times for the accuracy of the results
8. Use either manual calculation of speed or Logger Pro in order to calculate the kinetic energy of the vehicle at the end of the test for all three trials
9. Calculate the potential energy of the battery to conclude energy efficiency and compare results

What happened during the test?

This section of the blog post aims to explain the processes of two different trials and why we decided to do a second iteration: Ice Spike Wheels & Rubber Band Tread Wheels.

Trial One: Ice Spike Wheels

During this trial, the ice spike wheels that we originally designed were not able to get a grip on the mirror as we planned. The concept of the ice spike wheels was that they would be heavy enough to actually dig into the surface of the ice on Enceladus and provide it with propulsion, but on a light vehicle such as this one, the ice spike wheels didn’t have enough friction to overcome the inertia of the mirror surface.

Inertia is a force following the first of famous Sir Isaac Newton’s laws, that an object will not change its motion unless a force acts upon it. In our case, this would translate to the vehicle not moving unless the wheels generate enough force and grab onto the surface and thus overcoming the inertia.

Here is a video of the vehicle with the ice spike wheels attached. As one is able to observe, the vehicle simply does not move at all because of how little the wheels grip the mirror, even when spinning fast in the air beforehand.

Slightly disappointed, we regrouped and decided that we had to improve our wheels to grip the mirror better and also overcome the inertia of the mirror. This brings us perfectly to the second round of testing, where we 3D printed and assembled the rubber band tread wheels.

Trial Two: Rubber Band Tread Wheels

These trials went a lot better, with the vehicle actually making contact with the mirror, we were able to get data and have the vehicle move. Below is a video of one of our trials with our final prototype. It was able to start on the mirror and overcome the inertia of the mirror with just the change in the wheels.

How might we improve our test next time around?

Although this test design did yield data, there are numerous ways to improve the procedure and overall accuracy for next time:

• A more set camera angle, trying to be as close to an absolute bird’s eye view of the camera as possible
  • This would help us get more accurate test results. Currently, a person has to hold this camera up, and all humans are unreliable in being perfect each time, so I believe technology should be used in place for that next time.
• A longer mirror for a longer trial and therefore more accurate test results
  • The longer the vehicle runs, the better we can estimate its average speed and kinetic energy in order to test for its energy efficiency.
• Lining up the tapes and vehicle as straight as possible for a direct line of movement
  • This will increase the accuracy of our 30cm measurement and get better data in Logger Pro analysis later on

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SHREK BREAK!

Feel free to get yourself a plus-sized bag of assorted gummies and two raspberry-filled doughnuts. If you’ve already finished your latte up to this point, get yourself a cup of hot chocolate with exactly eight marshmallows. Carry on!

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The Construction Process of our Prototype

The assembly process of our prototype was a long and rewarding journey leading to our test. This section of the blog will first start by discussing the general assembly process, followed by discussing the change between ice spike wheels and rubber tread wheels, as mentioned in the testing process above.

General Assembly Process:

• Fabrication & Acquisition
  • 3D printing was the most important tool in building our prototype. The 3D printers ejecting hot plastic in a predetermined fashion is what enabled our team to successfully actualize our CAD designs in real life. Without 3D printing, we would have not been able to assemble anything except a couple of wires, motors, and two batteries. Definitely not a vehicle.

• Soldering
  • Soldering is the process of melting solder, a soft filler metal, to connect circuits together and allow electricity to flow through. This process was crucial in connecting our two parallel circuits of two motors each to their respective batteries and allowing them to be powered and work. Aside from the motors, we also soldered wires together to join them in their parallel circuit.

• Screwing
  • As mentioned before, we used M3 screws to fasten everything together in our vehicle. Without these, the motor mount could not be connected to the motor spine, which in turn could have not been connected to the Chassis. These screws are what gave this vehicle structure.

• Fitting + Taping
  • Our teacher jokingly mentioned to us that an engineer’s toolbox consists of two things: lubricant and duct tape. I think what he meant by that is when there is too little tolerance, one would use lubricant, and too little, duct tape.
  • This is exactly what we did with the motor mounts. The mounts proved to be too big for the motors and we ended up having to tape them to the mounts. Originally, the ice spike wheels also had to be taped, but when we switched to the rubber tread wheels, this issue did not arise.
  • We also taped the batteries and some wires together to better manage them in the future.

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Ice Spike Wheels vs. Rubber Tread Wheels

From the test results section above, you would have heard about the different wheels used in our prototype and how it would have affected the movement of the vehicles. After the first set of trials with the ice spike wheel, we quickly redesigned in CAD a wheel capable of fitting rubber bands, which eventually became our final design.

Materials & Energy Sources Used in Prototype

In our final prototype, the lower hull, motor spines, and motor mounts are made of PLA, which is a type of plastic commonly used in 3D printers, which was the mode of fabricating used in this case. PLA plastic is also good in the sense that it is quite manipulatable and soft, which is especially important for the tolerance of fitting axles and the M3 screws.

Obviously, there are parts of our prototype that are not PLA plastic, namely, the rubber bands, motors, wires, M3 screws, and solder. These were all individually ordered or acquired in some form in correspondence with the rest of the vehicle.

The energy source that we opted for during our prototype building was two nine-volt batteries. This was because it was the most convenient energy source for us to use and the school had a ready supply of them already. This allowed us to use these batteries with no delay in our project and moved things along more quicker.

Material Implications on Enceladus

Obviously, on Enceladus, keeping in mind the freezing temperatures and harsh conditions, we would not 3D print our chassis. Instead, we are theorized to utilize aluminum alloy as it is the same material used in many NASA spacecrafts, navigating in much of the same environment that we will encounter on Enceladus.

The electronics of this part would also be a problem. In such cold conditions, most electronics malfunction and break down. We hope to combat this through our insulation and the material used to build the hulls of the vehicle.

As for the energy source, we hope to utilise the tiger stripes and the geothermal activity on the South Pole of Enceladus, outlined in our empathy phase blog. In order to reach there, however, we are hoping to simply use a charged battery or even perhaps a nuclear energy source.

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• What does the data mean?  How did you analyze the data?  Show all of your math including any formulas you used in spreadsheets.

Data Analysis

Obviously, through recording and analyzing, we were able to conclude a whole range of data for each trial and other general measurements. This section of the blog aims to showcase this data and how they all fit in with each other to draw our conclusion.

Firstly, we have to cover some measurements of our vehicle, batteries, and motors (how they all fit in together will be explained shortly):

• Mass of final prototype vehicle: 0.2891 KG
• The difference in voltage after the test: 0.05 Volts
• Current that battery outputs while motors are connected: 0.9 Amps

What data did we get from our test?

This is the data that is available after the video analysis from Logger Pro with no calculations just yet.

Trial One:

• Speed: 0.53427 m/s
• Duration: 2.687 seconds

Trial Two:

• Speed: 0.54095 m/s
• Duration: 2.49 seconds

Trial Three:

• Speed: 0.50797 m/s
• Duration: 2.67 seconds

What does the data mean?

We have the data. Now it’s time to use it and finally get to the answer: energy efficiency.

Kinetic Energy of Vehicle

The kinetic energy of something can be calculated using this formula:

From our previous measurements, we may plug values in and calculate respective kinetic energy values for each trial:

Potential Energy of Batteries

The potential energy of the batteries proved to be a harder value to calculate, but will with some research from here, we were able to use some formulas to calculate the potential energy of the battery. Basically, we first calculated the coulombs (represented by Q) by multiplying the Amperes (I) by the duration of the test (t). Then we multiplied by the difference in volts (V) before and after the test in order to get the potential energy of the battery. Since we have two batteries,

Calculating Energy Efficiency

Getting the kinetic energy and potential energy allows us to calculate the energy efficiency of each trial. If we plug these two values into the formula, we can finally get these energy efficiency rates:

Trends, Patterns & Themes in Data

Well, I don’t need to be a genius to tell you that our vehicle is pretty gosh darn inefficient. There are no clear trends/patterns except for the fact that they are all between 15% and 19% energy efficient (I know, super awesome).

I believe the reason that the data varies is from many factors that could have been inaccurate. From calculating the different energy values to analyzing the videos in Logger Pro, there could have been inconsistencies in the data that occurred and compounded up throughout each calculation and step of the analysis.

I think the more prominent reason for a difference in the data values, aside from human errors, is the fact that the voltage in the battery goes down each time, and we forgot to measure after each test so the 0.05 V actually ended up being an educated estimate from a later measurement. This value for the difference in voltage could have been more accurate for one trial than the other and will result in inaccurate potential energies and subsequently the energy efficiency.

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Conclusion

Wow. What a project!

Although we can tell that we didn’t create the most efficient vehicle (with an average energy efficiency of 17.15%), we may look into these aspects of the vehicle to improve its efficiency:

• Stronger motors could have maybe overcome the inertia of the surface better
• Rubber bands could have been fitted onto the edge of the wheel a bit better in order to decrease the amount of unnecessary friction created
• Other forms of gripping the ice could be used such as tank treads that could potentially work better than 4 separate wheels

If we are to implement our current prototype onto Enceladus, it would be able to grip the ice and move around but would perhaps encounter trouble while trying to cross the moving ice crevasses. In the final design, we could theorize using adjustable tank treads to provide the most amount of versatility on the moon of Enceladus.

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Get yourself a large bowl of spaghetti bolognese with meatballs and marinara sauce, a caesar salad with croutons and grilled chicken breasts, and a large glass of almond milk because this blog post has finally come to an end, and you can go eat dinner now.