Multi-Functional Rectenna for a Lunar Rover

Current and previous lunar rovers are powered solely by batteries. These batteries are charged up during the lunar day and the rover is powered down during the lunar night to conserve energy. The rover can be made operational at all times by powering the rover wirelessly using a microwave beam. This microwave beam being transmitted to the rover can also be used to navigate the rover. The theory of a multi-functional rectenna array is presented in this article. Eight symmetrical nodes on the circumference of the rectenna and one node in the center of the rectenna are fitted with sensors which calculate the power density constantly. The central node communicates with the other 8 nodes calculating the relative power density. The central node is assigned to send movement commands such as faster speed in the direction of movement, slower speed in the direction of movement, forward, reverse, left turn, right turn, start and stop to the rover. These commands are triggered when the microwave beam is moved to focus one of the 8 nodes. For example, when the microwave beam is focused towards node 1 which is programmed to trigger the ‘stop’ command, the central node detects that node 1 has the highest relative power density and send the ‘stop’ command to the rover. Similarly, the microwave beam can be focused on other nodes to trigger the respective movement commands. While the beam is required to be returned back to the center before a new command is used, a return to center policy is employed, that sends data signals back to the transmitter so that the beam is moved back to the center of the rectenna after a movement has been triggered. The data signal contains the delta x and delta y of the beam position from the center of the rectenna. This data signal can also be used to relay other information collected by the rover to the ground station. Thus, the proposed multi-functional rectenna can power the rover at all times increasing its operational time, can be used to navigate the rover and also relay information collected by the rover to the ground station, all at once

Wireless Power Transfer to Sitallite Stratospheric Platform

The following topics are dealt with: artificial satellites; ionospheric electromagnetic wave propagation; Global Positioning System; satellite navigation; ionospheric techniques; radiowave propagation; space vehicle electronics; ionospheric disturbances; total electron content (atmosphere); and magnetic storms

Performance Estimates for a Fuel-Free Stationary Platform in the Stratosphere

High-altitude pseudo-satellites (HAPS) may be kept aloft indefinitely with station-keeping provided by plasma air thrusters (PAT) using wireless power transfer (WPT) from a terrestrial phased array antenna (PAA). One example is the patented “Sitallite” superpressure balloon with a rectifying antenna (rectenna) covering its underside, with thrusters around the periphery. Such a stationary platform can provide continuous observation and communications capabilities covering vast areas for a fraction of the cost required for an orbiting satellite. This work builds upon the design and safety study published elsewhere to provide performance estimates for a long-duration, persistent HAPS powered by electronically-steerable microwave beams. Newly-derived efficiency equations are used to provide accurate estimates of free-space WPT transfer efficiency based on the dimensions of the ground-based PAA and the rectenna. Calculations of air drag for a spheroidal bouyant shape are used to derive PAT power requirements, and these, together with power conversion circuitry, are used to size the overall system. Accurate estimates of cost are derived. These performance estimates can be used to help make economic and logistic decisions, as a fuel-free HAPS with PAT and powered by WPT can be lofted in less time, and with lower risk, than an orbital satellite of comparable capabilities