Robert C. O'Brien

The Mars Hopper: an impulse-driven, long-range, long-lived mobile platform utilizing in situ Martian resources

The requirements for performance by planetary exploration missions are increasing. Landing at a single location to take data is no longer sufficient. Due to the increasing cost, the missions that provide mobile platforms that can acquire data at displaced locations are becoming more attractive. Landers have also had limited range due to power limitations, limited lifetime of subsystems, and the inability to negotiate rough terrain. The Center for Space Nuclear Research has designed an instrumented platform that can acquire detailed data at hundreds of locations during its lifetime — a Mars Hopper. The Mars Hopper concept utilizes energy from radioisotopic decay in a manner different from any existing radioisotopic power source — as a thermal capacitor. By accumulating the heat from radioisotopic decay for long periods, though, the power of the source can be dramatically increased for short periods. Thus, a radioisotopic thermal rocket is possible. The platform will be able to ‘hop’ from one location to the next every 2—3 days with a separation of 10—20km per hop. Each platform will weigh around 50kg unfuelled which is the condition at deployment. Consequently, several platforms may be deployed on a single launch from Earth. With a lifetime estimated at 10 years, the entire surface of Mars can be mapped in detail by a couple dozen platforms. In addition, hoppers can collect samples and deliver them to the Mars Science Laboratory for more detailed analysis. Furthermore, the basic platform can be deployed to Europa, Titan, and even Venus with alterations — the propulsion system and operations essentially will be the same.

Current Development of Nuclear Thermal Propulsion technologies at the Center for Space Nuclear Research

Nuclear power and propulsion has been considered for space applications since the 1950s. Between 1955 and 1972 the US built and tested over twenty nuclear reactors / rocket engines in the Rover/NERVA programs1. The Aerojet Corporation was the prime contractor for the NERVA program. Modern changes in environmental laws present challenges for the redevelopment of the nuclear rocket. Recent advances in fuel fabrication and testing options indicate that a nuclear rocket with a fuel composition that is significantly different from those of the NERVA project can be engineered; this may be needed to ensure public support and compliance with safety requirements. The Center for Space Nuclear Research (CSNR) is pursuing a number of technologies, modeling and testing processes to further the development of safe, practical and affordable nuclear thermal propulsion systems.

Improving quantum efficiency and spectral resolution of a CCD through direct manipulation of the depletion region

Future generations of X-ray astronomy instruments will require position sensitive detectors in the form of charge-coupled devices (CCDs) for X-ray spectroscopy and imaging with the ability to probe the X-ray universe with greater efficiency. This will require the development of CCDs with structures that will improve their quantum efficiency over the current state of the art. The quantum efficiency improvements would have to span a broad energy range (0.2 keV to >15 keV). These devices will also have to be designed to withstand the harsh radiation environments associated with orbits that extend beyond the Earths magnetosphere. This study outlines the most recent work carried out at the University of Leicester focused on improving the quantum efficiency of an X-ray sensitive CCD through direct manipulation of the device depletion region. It is also shown that increased spectral resolution is achieved using this method due to a decrease in the number of multi-pixel events. A Monte Carlo and analytical models of the CCD have been developed and used to determine the depletion depths achieved through variation of the device substrate voltage, Vss. The models are also used to investigate multi-pixel event distributions and quantum efficiency as a function of depletion depth.