One thing I try to use in all my projects now is a sturdy base, and this one is no exception. If you look at the outer mainframe, it's reinforced in several places.
The NXT is placed sideways, something I don't really like doing, but it opens up other possibilities in building.
The 40-tooth gears are positioned just far enough from each other so that the tires won't rub. They also don't have any gearing to adjust speed or power, so the motors have to work a little harder, especially on carpet. The middle tire sticks out from the rest because of the connection between the two 11m beams (see pics.).
Next, I wanted to make this robot actually look like more than a "skeleton". So I attached this platform that uses both 15m beams and TECHNIC bricks, creating an almost flat surface.
The Ultrasonic sensor is positioned in this place to avoid missing low objects, while still maintaning clearance of the ground.
The Light sensor's only purpose is to detect ambient(non-reflecting) light, serving as a solar collector.
The arm above the US is merely representing a probing tool that would be used for drilling and analyzing rocks and any other objects Voyager would encounter.
The LDD doesn't have everything put together, so the pic. is to help you fix it.
The first .rbt is Voyager's program, the second is the receiver (second NXT). There is one problem with the program, but I can't figure out how to fix it. The robot will run the program normally until it gets to the part where the second NXT chooses what to do about probing or not. Then, after the second time it comes to that part, I press either button for choosing, and it doesn't respond. Please, if you can fix this, go right ahead and either tell me how to fix it or post the fixed program. Please.