We have studied the feasibility and scientific potential of zenith observing liquid-mirror telescopes having 20Y100 m diameters located on the Moon. They would carry out deep infrared surveys to study the distant universe and follow up discoveries made with the 6 m James Webb Space Telescope (JWST ), with more detailed images and spectroscopic studies. They could detect objects 100 times fainter than JWST, observing the first high-redshift stars in the early universe and their assembly into galaxies. We explored the scientific opportunities, key technologies, and optimum location of such telescopes. We have demonstrated critical technologies. For example, the primary mirror would necessitate a high-reflectivity liquid that does not evaporate in the lunar vacuum and remains liquid at less than 100 K. We have made a crucial demonstration by successfully coating an ionic liquid that has negligible vapor pressure. We also successfully experimented with a liquid mirror spinning on a superconducting bearing, as will be needed for the cryogenic, vacuum environment of the telescope. We have investigated issues related to lunar locations, concluding that locations within a few kilometers of a pole are ideal for deep sky cover and long integration times. We have located ridges and crater rims within 0.5 of the north pole that are illuminated for at least some sun angles during lunar winter, providing power and temperature control. We also have identified potential problems, like lunar dust. Issues raised by our preliminary study demand additional in-depth analyses. These issues must be fully examined as part of a scientific debate that we hope to start with the present article.

The force of levitation experienced by a magnet on top of' a superconductor depends on position and how fast the magnet was put into that position. As a result, when the levitation force is measured as a function of the height of the magnet above the superconductor, a plot of the force versus height also depends on the rate at which the magnet position was changed during the experiment. We have measured this dependence of the levitation force (as a function of position) on the average rate of moving the magnet towards the superconductor under zero field cooled conditions. This dependence is appreciable only when the magnet is close to the superconductor. After the magnet is brought to a stop a t the nearest position, we continued to observe the relaxation of the magnetic stress between the magnet and the superconductor. The gross characteristics of the relaxation process after the magnet stops are similar for different speeds of approach before the magnet stops. This study aims a t determining how the long term reliability of a superconductor magnet bearing depend on the process of setting it up.

We have developed a small reaction wheel, designed to be lightweight, compact and energy efficient. The main innovation is the use of the HTS magnet's bearings that promise low friction so that high momentum storage can be achieved with high spin speed. The bearings consist of seeded growth superconducting discs arranged in rings located above and below the rotating levitated wheel containing ring-magnets embedded at the top and bottom. The reaction wheel is in the shape of a hollow stainless steel cylinder. A brushless dc motor is installed inside the hollow cylinder to provide the necessary torque to the reaction wheel. The maximum design spin speed is 15 000 RPM to store 3.5 J s−1 of angular momentum. Spin-down test of the reaction wheel was performed in air. We have also measured the input power required to sustain rotational speed of the reaction wheel in air. Results from both of these measurements, when extrapolated to full speed in vacuum, indicate that power consumption, even accounting for the needs of the cooling system, is significantly smaller than that for state of the art commercial reaction wheels using mechanical ball bearings.

Abstract--A telescope to be installed on the lunar surface in the near futere mast work in a cold and dusty vacuum environment fur long periods without on site human maintenance.. To track stars, the drive mechanism must be capable of exceedingly fine steps and repeatability.Further We report on the first prototype I-ITS bearing module built at the University of Houston in collaboration with Chert to be assembled as an azimuth mount for a levitated lunar telescope, see Fig. 1. II. LUNAR BEARING REQUIREMENTSTo track the position of a celestial object, the telescope must be able to change orientation as the moon rotates about Earth and its own axis. In general, the bearing module would have rotation capability in three directions.

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