Lunar Rover Design Challenges - Environmental Issues
Environmental Issues - Lunar Rover Design Challenges:
The temperature on the moon varies roughly from -400°F (-240°C) at night to 250°F (121°C) during the day. Our rover will have to survive in these extreme conditions in order to fulfill its mission. Electronics can only operate within certain temperature ranges. Temperature failures are most commonly experienced when a device is left out in the snow overnight or in a closed car on a hot summer day. Our rover will need to keep its electronics warm in order for them to operate. Many spacecraft use the onboard computer(s) to generate heat. As electronics function some of the electricity flowing through them is converted into heat. This is why you see cooling fans on electronics. Sometimes the heat generated by the onboard computers is enough to keep the inside of the spacecraft warm enough for the electronics to operate and other times a heater is needed to keep everything warm. It’s possible that a spacecraft can get too hot and will need a radiator in order to cool itself. We are working on some modeling and simulation programs that can help us calculate how hot or cold our rover will get so that we can plan to counteract any temperature problems. The chassis materials of the rover will also need to be able to survive in these extreme conditions without turning brittle, cracking, or shrinking and expanding too much.
In outer space there are many kinds of radiation that the Earth’s atmosphere blocks or absorbs for us so that we are not affected. The moon does not have an atmosphere to block radiation from the rover. So while in transit from Earth to the moon and while on the moon our rover will be exposed to radiation. Radiation can interfere with electronic systems by injecting electrically charged particles. This can cause sensors to give false readings or the computer to calculate incorrectly. There are two ways to solve this issue. All the electronics can be enclosed in a protective material such as lead or we can “harden” the electronics from the effects of radiation. Lead is heavy, consumes part of our small rover space, and is unsafe to handle. Hardening electronics to the affects of radiation is expensive but necessary in order to operate in outer space. Hardening is a special fabrication and treatment process that helps electronic systems to block stray charged particles from radiation.
Dust on Earth is an annoyance that can be cleaned. Unfortunately we cannot just walk over to the rover on the moon and wipe it down with a rag. Dust on moon will pile on the rover and its solar panels. As the layer of dust thickens over time the solar panels will generate less and less power for us. When the dust gets on our cameras it will begin to block our view. Since the moon does not have any erosion its dust is very sharp and abrasive unlike dust on Earth. It’s possible that dust could get inside our motors and gears and grind against them causing deterioration. Investigations into the affects of dust on our rover and the amount of dust we expect to kick up while moving is under way.
The dust also affects our wheel designs. The lunar surface is covered in a thick layer of dust. Imagine trying to run in fine sand or a pile of table salt. The ground moves beneath you and makes keeping your balance and maintaining traction tricky. Our rover will have the same trouble due to a very thick layer of dust covering the entire moon. Our wheels will have to dig into the dust in order to maintain traction like cleats on sports shoes.
“V” wheel tread design idea.
Paddle wheel tread design idea.
Bring it all together
All these different design challenges compete for space, weight, and power on our rover. We have to find a compromise for all these things in order to make a rover that will explore the lunar surface on beyond. Finding the best compromise will require lots of modeling and computer simulations as well as physically creating these small prototypes for testing in mock terrain environments.
Complete rover CAD model for simulating sizes, weights, and physical forces on the rover.
Rover Systems Integrator