The physical price of a ticket into space

As a direct consequence of exposure to microgravity astronauts experience a number of physiological changes, which can have serious medical implications when they return to Earth. Most immediate and significant are the head-ward shift of body fluids and the removal of gravitational loading from bone and muscles, which lead to progressive changes in the cardiovascular and musculoskeletal systems. Cardiovascular adaptations result in an increased incidence of orthostatic intolerance (fainting) post-flight, decreased cardiac output and reduced exercise capacity. Changes in the musculoskeletal system contribute significantly to the impaired functions experienced in the post-flight period. The underlying factor producing these changes is the absence of gravity. Countermeasures, therefore, are designed primarily to simulate Earth-like movements, stresses and system interactions. Exercise is one approach that has received wide operational use and acceptance in both the US and Russian space programmes, and has enabled humans to stay relatively healthy in space for well over a year. Although it remains the most effective countermeasure currently available, significant physiological degradation still occurs. The development of other countermeasures will therefore be necessary for longer duration missions, such as the human exploration of Mars.     

A low-cost femtosatellite to enable distributed space missions

A new class of distributed space missions is emerging which requires hundreds to thousands of satellites for real-time, distributed, multi-point sensing to accomplish long-awaited remote sensing and science objectives. These missions, stymied by the lack of a low-cost mass-producible solution, can become reality by merging the concepts of distributed satellite systems and terrestrial wireless sensor networks. However, unlike terrestrial sensor nodes, space-based nodes must survive unique environmental hazards while undergoing complex orbital dynamics. A novel sub-kilogram very small satellite design is needed to meet these requirements. Sub-kilogram satellite concepts are developing elsewhere, such as traditional picosatellites and microengineered aerospace systems. Although viable technical solutions, these technologies currently come at a high cost due to their reliance on high-density technology or custom manufacturing processes. While evaluating these technologies, two untapped technology areas became evident that uniquely encompass low cost and mass producibility by leveraging existing commercial production techniques: satellite-on-a-chip (SpaceChip) and satellite-on-a-printed circuit board (PCBSat). This paper focuses on the design, build, and test results of a prototype PCBSat with a prototype unit cost less than $300. The paper concludes with mission applications and future direction.     

Tactical cockpits-the coming revolution

A cockpit revolution is in the making. Many of the much ballyhooed, much promised, but little delivered technologies of the 70's and 80's will finally come of age in the 90's just in time to complement the data explosion coming from sensor and processing advances. Technologies such as helmet systems, large flat panel displays, speech recognition, color graphics, decision aiding and stereopsis, are simultaneously reaching technology maturities that promise big payoffs for the third generation cockpit and beyond. The first generation cockpit used round dials to help the pilot keep the airplane flying right side up. The second generation cockpits used multifunction displays and the HUD to interface the pilot with sensors and weapons. What might the third generation cockpit look like? How might it integrate many of these technologies to simplify the pilot's life and most of all: what is the payoff? This paper examines tactical cockpit problems, the technologies needed to solve them and recommend three generations of solutions     

Galaxies at the detection limits of deep X-ray surveys

The great sensitivities of the Chandra X-ray Observatory and XMM-Newton have allowed us to begin to explore the X-ray emission from galaxies at moderate to high redshift. By using the stacking method, we show that we can detect the ensemble emission from normal elliptical, spiral and irregular galaxies out to redshifts approaching unity. The average X-ray luminosity of these galaxy types can then be compared with the results of models of the evolution in the numbers of low-mass and high-mass X-ray binaries and can possibly be used to constrain models of star formation.     

How well does voice interaction work in space?

The methods and results of an evaluation of the Voice Navigator software package are discussed. The first phase or ground phase of the study consisted of creating, or training, computer voice files of specific commands. This consisted of repeating each of six commands eight times. The files were then tested for recognition accuracy by the software aboard the microgravity aircraft. During the second phase, both voice training and testing were performed in microgravity. Inflight training was done due to problems encountered in phase one which were believed to be caused by ambient noise levels. Both quantitative and qualitative data were collected. Only one of the commands was found to offer consistently high recognition rates across subjects during the second phase     

Use the water: In-situ resource technology for icy-surface landers

Robotic landers serve vital reconnaissance roles in the exploration of planetary surfaces, but are constrained by deliverable payload size and environment survivability. Although the Mars exploration rovers (MER) have shown incredible survivability, their solar power source limits the science output per sol. Future landers will be larger, and will incorporate more sophisticated data-collection and analysis packages, which will likely bring with them an increased demand for power. Anticipating this demand, we propose an innovative hybrid power system combining a primary radioisotope thermoelectric generator (RTG) with a secondary alkaline fuel cell. This combination provides the opportunity to utilize more effectively the energy produced by the RTG, to produce and store O₂ and H₂ via electrolysis of melted ice, and use this obtained O₂ and H₂ in a variety of ways, including as fuel for a regenerative fuel cell. This hybrid system has applications ranging from planetary rovers and deep-space probes to human habitats.     

The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.     

An adaptive strategy for active debris removal

Many parameters influence the evolution of the near-Earth debris population, including launch, solar, explosion and mitigation activities, as well as other future uncertainties such as advances in space technology or changes in social and economic drivers that effect the utilisation of space activities. These factors lead to uncertainty in the long-term debris population. This uncertainty makes it difficult to identify potential remediation strategies, involving active debris removal (ADR), that will perform effectively in all possible future cases. Strategies that cannot perform effectively, because of this uncertainty, risk either not achieving their intended purpose, or becoming a hindrance to the efforts of spacecraft manufactures and operators to address the challenges posed by space debris.