Outline

The Lunar Rover Race (LRR) is a huge public awareness, interest and education mission. Since funding will be almost entirely by sponsorship and advertisement, adequate media coverage is an important issue. In conjunction with the requirement that all ten rovers shall send a video signal of predefined frame rate and resolution to Earth, there will be an eleventh rover that is entirely dedicated to producing high quality video coverage of the finish of each daily stage. This rover is called the media vehicle and is not a participant of the race. The media vehicle will travel to each checkpoint before the next stage of the Rover Race starts. Each stage of the LRR will be approximately six hours, and one race stage will be held per day on average.

The media vehicle will have to be highly reliable and will therefore be designed and built in a controlled fashion, and not by participating rover teams. The rover will have an allowed mass of 15 kg, and is confined to a volume of 300 mm by 800 mm by 600 mm. The media vehicle will have more broadcasting power than the racing rovers through the use of deployable solar panels. These panels are deployed only when the media vehicle is stationary. Since the media vehicle does not participate in the race it will take the shortest and safest route between any two successive checkpoints and may deviate from the actual race track.

Basic Concept

The basic concept of the media vehicle is shown in Figure 4-30. The media vehicle travels in a "clean" configuration: there are no extending poles or solar arrays. An outline of the idea is shown in the figure, however, the position of the solar is not shown. The deployable solar panels shall be stowed in a manner that allows for easy and safe movement through the lunar environment. Upon arrival at the checkpoint, the media vehicle searches for a flat surface. It will then level itself to cancel any remaining surface incline by adjusting its suspension. A vertical structure will then be deployed to a height of 5 m. The video camera at the end of this pole will be able to cover the approach of the rovers from a maximum distance of 4 km. At the same time, a video camera on the body of the vehicle will give live video coverage of the finish of the rovers.

Figure 4-30: Media Vehicle will Provide Media Coverage from 4 km (drawing not to scale)

Video Pole Design Concept

Figure 4-31 shows one of the triangular truss elements that build up the camera pole. The pole is extended by electric motors at its base. Shortening the base (db in the figure) will cause the element to increase its height.

The height to which the element is extended is limited by the required stiffness of the pole. The stiffness should be very high, because the pole should not be allowed to sway in all directions by video camera actuation. Determination of the deployment angle is a trade-off between pole stiffness and pole mass. If the angle is too small the number of elements will need to be high to achieve the desired height, but the structure will be more rigid. If the angle is too large, few elements are needed but the structure may become unstable. Estimation of the actual stiffness of the structure is beyond the scope of this conceptual outline of the media pole and will not be discussed. Instead, an engineering assumption is made with the following considerations:

• The media pole is not loaded in a lateral manner provided that the media vehicle is able to place itself in a horizontal position,
• The gravity level on the Moon is relatively low, and
• By using high precision bearings, play in the structure is kept at a minimum.

Based on these considerations the vehicle can have a base that is slightly smaller than the height of the extended element. This therefore means that more importance is given to the minimum mass requirement, at the cost of a slight decrease in flexibility.

It is assumed that the element extends to a height of 250 mm. For a 5 m high structure, 20 triangular truss elements are required. The height of the pole in stowed position is then 240 mm. As the maximum allowed height of the total media vehicle is 300 mm, the pole will have to be contained within the vehicle.

Pole Mass

The u-shaped bars that make up the element are assumed to measure 300mm by 5mm by 0.5mm. If made of aluminum, one bar would have a mass of 3 g. Each triangular truss element contains six bars. The total mass of the media pole then becomes 0.7 kg. By using more lightweight materials like carbon fiber reinforced plastics, this mass could be brought down considerably. A mass of 0.7 kg will be used as a worst case value in the stability consideration of the next paragraph.

Rover Stability

It is assumed that the video camera with pan, tilt and zoom capability weights approximately 200 g. The camera is mounted at the top of the 5 m pole. As the media vehicle is constrained to a mass of 15kg the body can weigh approximately 14 kg. The center of mass of the body is assumed to be 15 cm above ground. The center of mass of the complete MV with deployed video pole then becomes 0.3 m above ground. As the maximum allowed value of base of the vehicle (500 mm3) is larger than the height of the center of mass, the deployed system is inherently stable. By letting the deployed solar arrays rest on the lunar soil, extra stabilization can be obtained.

Video Image Stability

Because the boom is flexible by nature, it will be excited by the actuation of the video camera. The slight movement that is introduced can be removed from the video signal by computer post processing.

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