The goal was to determine the best possible way to traverse the lunar regolith for a distance of at least 500 meters. To do this we began with the general process of breaking down the project into a set of goals for the locomotion, and coming up with the best possible solution for these goals. The goals we developed for the project were to make a wheel and motor system which would be able to travel the distance, survive the lunar environment, be as light as possible, and to be energy efficient.
Through our research, we were able to determine that the best possible way to accomplish our goals was to make an in-wheel motor design with a multi-v tread. The reasons that we decided on the in-wheel motor tread is because it gives the rover the best torque control and is a more energy efficient system than a centralized system. We decided to go with a V tread design as this would give us the best traction in the lunar regolith. After further consideration, the tread was changed to a multi-V to make sure that it could travel in forward or reverse efficiently. This gave us a basic idea of how the wheel needed to be made. Finally, we needed to decide which material to make the wheel out of. After doing the research, our group decided that using aluminum 6061. This material gives us the needed strength and gives us favorable thermal qualities.
Next, we needed to build a model of our design using SolidWorks and run stress analysis on it to be able to determine if our design would be able to handle the strains which were placed on it. CosmosWorks was used to get the stress models and the factor of safety for the model. These confirmed that our design was able to handle the loads which would be placed on it. These can be seen in the stress analysis photos.
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Wheels
I do agree, that a vehicle that can avoid the lunar surface all together may prove to be an easy method for making that 500 meters, or it may have other inherent problems that make it a bad design. Regardless, we are not designing a vehicle to merely travel 500 meters. We are going with a typical wheeled rover because we feel that the journey is just as, or maybe more, important than the destination. Sure the destination holds with it the prize, but let's not forget that prize should not be the only motives for going. We are building a technology that is far cheaper and far superior to what is currently available. A catapult or slingshot system seems like a one shot deal whereas our design will have sustainability to it.
Thanks for the interesting comment.
Jason Dunn, BSAE
Omega Envoy | Engineering & Space Concepts Director
Wheels
I have calculated that the easiest way to go the 500 meter distance is with a catapult, slingshot, or shelled rover. A surface-to-surface rocket rover would also work well. At a 45 degree angle, going 500 meters in Moon vacuum is equal to going 82 meters in Earth vacuum. Thus, it will not take a very powerful catapult to send the rover the distance. Also, unlike Earth rovers, the Moon rover does not have to worry about aerodynamics since there is no wind resistance.
As far as your wheel design goes, it looks sharp. But from a practical perspective, you have to remember not to make your wheels too small. So if you rely on too small a wheel to keep the weight down in your in-wheel motor design, you may run into mobility problems once on the moon.
Another question is whether you want v-shaped fins or treads. Reports describe the regolith as being very powdery. Think of very dry powder snow. I would think the fins will work better than the treads. Here is a photo of wheel fins on Lunakhod 2.
http://en.wikipedia.org/wiki/File:Lunokhod_detail.jpg