Lunar precursor missions for human exploration of Mars--III: studies of system reliability and maintenance

Discussions of future human expeditions into the solar system generally focus on whether the next explorers ought to go to the Moon or to Mars. The only mission scenario developed in any detail within NASA is an expedition to Mars with a 500-day stay at the surface. The technological capabilities and the operational experience base required for such a mission do not now exist nor has any self-consistent program plan been proposed to acquire them. In particular, the lack of an Abort-to-Earth capability implies that critical mission systems must perform reliably for 3 years or must be maintainable and repairable by the crew. As has been previously argued, a well-planned program of human exploration of the Moon would provide a context within which to develop the appropriate technologies because a lunar expedition incorporates many of the operational elements of a Mars expedition. Initial lunar expeditions can be carried out at scales consistent with the current experience base but can be expanded in any or all operational phases to produce an experience base necessary to successfully and safely conduct human exploration of Mars.     

Overcoming barriers to space travel

This viewpoint argues that the barriers preventing human expansion into space are not scientific but political and legal - an inability to secure funding; artificially high costs created by punitive insurance premiums and excessive bureaucracy; and uncertainty and disagreement about the extent and implications of legal regulation of space activities. Construction on Earth of a ‘metanation’ to oversee the governance of outer space is advocated as a possible solution.     

Analytical solutions for the relative motion of spacecraft subject to Lorentz-force perturbations

A spacecraft capable of producing higher-than-natural electrostatic charges may achieve propellantless orbital maneuvering via the Lorentz-force interaction with a planetary magnetic field. Development of maneuver strategies for these propellantless vehicles is complicated by the fact that the perturbative Lorentz force acts along only a single line of action at any instant. Relative-motion dynamical models are developed that lead to approximate analytical solutions for the motion of charged spacecraft subject to the Lorentz force. These solutions indicate that the principal effects of the Lorentz force on a spacecraft in a circular orbit are to change the intrack position and to change the orbit plane. A rendezvous example is presented in which a spacecraft with a specific charge of ?3.81 $\times$ 10^?4 C/kg reaches a target vehicle initially 10 km away (on the same equatorial low-Earth orbit) in 1 day. Fly-around maneuvers may be achieved in low-Earth orbit with specific charges on the order of 0.001 C/kg.     

Near-infrared detection of potential evidence for microscopic organisms on Europa

The possibility of an ocean within the icy shell of Jupiter's moon Europa has established that world as a primary candidate in the search for extraterrestrial life within our Solar System. This paper evaluates the potential to detect evidence for microbial life by comparing laboratory studies of terrestrial microorganisms with measurements from the Galileo Near Infrared Imaging Spectrometer (NIMS). If the interior of Europa at one time harbored life, some evidence may remain in the surface materials. Examination of laboratory spectra of terrestrial extremophiles measured at cryogenic temperatures reveals distorted, asymmetric nearinfrared absorption features due to water of hydration. The band centers, widths, and shapes of these features closely match those observed in the Europa spectra. These features are strongest in reddish-brown, disrupted terrains such as linea and chaos regions. Narrow spectral features due to amide bonds in the microbe proteins provide a means of constraining the abundances of such materials using the NIMS data. The NIMS data of disrupted terrains exhibit distorted, asymmetric near-infrared absorption features consistent with the presence of water ice, sulfuric acid octahydrate, hydrated salts, and possibly as much as 0.2 mg cm(-3) of carbonaceous material that could be of biological origin. However, inherent noise in the observations and limitations of spectral sampling must be taken into account when discussing these findings.     

ESA developments in life support technology: achievements and future priorities.

Following an enthusiastic start in 1985, ESA's life support technology development programme was re-assessed in the mid- to late-1990s to reflect the strong reduction in European manned space ambitions which occurred at that time. Further development was essentially restricted to activities that could constitute ISS upgrades or enhancements, or support ISS utilisation/operations, together with a single, limited, activity (MELISSA) aimed at bioregenerative life support, in the continuing hope that there might be "life after Station". The paper describes the current status of these activities and summarises the main priorities for future development that were identified at the April 1999 Workshop on Advanced Life Support.     

Reflections on human presence in space.

Humankind's exploration of Space has until now been understood as analogous to that of planet Earth: sending out crews to far-off, unknown lands in the hope of finding supplies of food, water or energy along with shelter and living-space. But Space is turning out to be much less hospitable than our earthly milieu in terms of resources as well as energy costs. It seems appropriate to ask what level of adaptation is needed for humans to travel and live in the cosmos, and to assess if the next logical step should necessarily be a programme of conquest analogous to that of the Moon--for example, towards Mars. Should we not rather be making more use of Earth's immediate neighbourhood, namely the sphere of a million of kilometres we call "Greater Earth"? In the same way, it is appropriate to ask questions about the conception of human beings which will from now on sustain the conquest of Space. The astronaut of the last forty years is the direct heir of the explorers of Ancient and Modern times; now, through the influence of science and technology, humanity has been put "into motion" not only geographically, but also in its most essential foundations: culture, psychology, philosophy. If the development of telepresence technology now gives us the ability to talk about a "Greater Human Being", it is chiefly through freedom of choice for oneself, for humanity and even for Earth.     

Cylindrical heterogeneous detonation waves

Further experimental studies of blast wave initiated cylindrical heterogeneous (liquid fuel drops, gas oxidizer) detonation waves are described. A pie-shaped shock tube, used for these studies, was altered in certain ways so as to improve the modeling of cylindrical waves. These modifications, along with some operational aspects, are briefly discussed. The breech of the facility, where the blast wave is generated by an explosive, became distorted with usage. Results are presented which show that lower detonation velocities are realized with the damaged breech (other conditions being the same). A photographic and pressure switch wave time of arrival study was made to ascertain the wave shape. Photographs are shown which show that the waves, blast as well as detonation, are close to cylindrical. However, in some cases there is appreciable distortion of the wave front by debris ahead of the wave. Presumably this debris comes from the blasting cap used to ignite the condensed explosive. A series of experiments was conducted using kerosene drops of 388 μm diameter dispersed in air through use of a large number of hypodermic needles. Radial fuel void regions were established by cutting off the fuel flow to a number of needles. Preliminary results relating to the effect of the size of the cloud gap on detonation velocity, quenching, and the initiator energy levels required for detonation are discussed.