ENAE
483/788D - Lecture #08
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Space Systems Laboratory - Department of Aerospace Engineering - University of Maryland |
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Home>Academics>ENAE 483 Fall 2007
Lecture slides (PDF; 3.4 Mb, 27 pgs.) [revised 071016]
As part of your pressurized rover system, you need an emergency "bail-out" option that will allow the crew to return to the lander after a failure of the primary rover. You decide to approach this by creating a "lunar ATV": a simple, small four-wheeled rover designed to carry a single pressure-suited individual up to 50 km at 10 km/hour, and which can be easily deployed and used following a failure.
a) Assume this ATV has an empty mass of 50 kg, and has four wheels which are each 50 cm in diameter and 20 cm wide. The wheels have grousers such that two are always in contact with the surface, and each are 5 cm long. The EVA crewman has a mass of 150 kg. Assume the coefficient of rolling friction is 0.15. What is the limiting slope this vehicle can climb? (Use all other parameters from the examples in this lecture.)
b) Calculate the typical wheel force required for travel over level ground.
c) Power required is force times velocity. Assuming the drive train is 50% efficient, find the required power for the drive motors in each wheel.
d) What is the total energy (power times time) required for six hours of travel at 10 km/hour on level ground?
e) In the event that one of the two ATVs fail, both crew can ride on a single vehicle in an emergency. How would your answer to (a) change in this case?
f) Given your answer to (e), if you only had one working ATV from the beginning, what would be your limiting range?