Lunar Torch

Last crawled date: 2 years, 7 months ago

This mobile heliostat uses a polished spring-tempered stainless-steel sheet for its mirror.

The deployment of the mirror is a slow and controlled “un-furling” towards the springs free state. Cables let out by brake motors provide this controlled motion.

The cable system also doubles as a control mechanism for the mirrors "shape". The mirror can be made perfectly flat using the motors, which allows compensation for tolerances associated with fabrication, stress relaxation, or thermal expansion. As an additional “bonus” feature, the mirror can be controlled to be slightly convex, or slightly concave, which allows adjustment of the intensity of light hitting the target.

The structural support for the mirror is provided by side bends (for vertical beam strength), tubes across the top and bottom (for horizontal stiffness and flatness), and by the internal stress of the material in balance with the tension in the cables (the free state of the mirror is slightly concave to ensure cables are always in tension). If needed, additional horizontal support can be added in the form of battens tack welded across the back of the mirror. Similarly, vertical stiffness can be increased by adding "tape springs" to the back of the mirror, i.e. thin strips of sheet metal with transverse curvature. During the design phase, FEA can be used to optimize the exact material thickness and support structure of the mirror to ensure flatness.

In the stored state, the mirror is rolled into a large diameter coil. The large curvature allows thicker material to be rolled while remaining above the material yield point. i.e. the "spring" free state of the mirror is maintained.

Pitch and yaw tracking motion is produced by a two axis slew drive, which is connected to control system including a sun sensor.

The overall system has low mass and a low rotational inertia with respect to the rover, due to the mirror in large part “supporting itself”. This makes for reduced rocket fuel required for the trip to the moon, and, allows for transport to different locations on the lunar surface while deployed.

The heliostat includes solar panels below the mirror, and battery energy storage. This provides the power to the motors, controls, and heat management systems.

Supplemental benefits of this design:

- The energy of the springs, which is released as the mirror unfurls, can be used to deploy leg support mechanisms. This would be useful for stand-alone heliostats not mounted to rovers.

- The ability to increase or decrease the reflected light intensity by changing the shape of the mirror. (as mentioned above)

- The tape spring features can produce a controlled "popping action" of the mirror spring by intentionally pulling them past the buckling point with the cables. This can be used to "shake" lunar dust off the mirror if it accumulates over time.


See the attached PDF files for more engineering details of this concept.