Occurrence of brain tumors in rhesus monkeys exposed to 55-MeV protons.

Twenty-year observation of monkeys exposed to single doses of high energy protons simulating solar particles revealed that the most prevalent fatal cancers were brain tumors in the group of animals exposed to 55-MeV protons. Of 72 animals (50 males and 22 females) receiving 0.25 to 8.0 Gy total body surface dose, nine developed fatal tumors classified as grade IV astrocytoma or glioblastoma multiforme. The latent period for tumor development ranged from 14 months to 20 years, with a median of 5 years. Doses associated with the tumors were 4.0 to 8.0 Gy. Eight males and one female were affected. Depth-dose determinations suggest that the high incidence of cerebral neoplasia is associated with the Bragg Peak energy distribution of the 55-MeV protons. Comparison of the tumor incidence with that in humans with brain exposures incidental to radiotherapy indicates a high biological effectiveness compared with gamma radiation. Studies are in progress to attempt to replicate the results in rodents and establish a dose-response curve for proton-induced brain tumors.     

Skill maintenance in extended spaceflight: a human factors analysis of space and analogue work environments

This paper discusses the implications of increasing mission lengths of manned spaceflight for the design of future space systems from a human factors point of view. It is argued that the increase in mission duration has brought about a number of new problems, which have not been sufficiently addressed in space research. Therefore, a review of analogue work environments is carried out to make up for the paucity of space research found in the area of human performance in long-duration spaceflight. This resulted in an evaluation of seven analogue environments concerning their similarity to space with industrial process control and nuclear submarines coming out as the closest match on the technical dimension. Finally, some recommendations are given from the lessons learned in spaceflight, simulation studies and appropriate analogue environments.     

Analytical definition and proposed concept for the manned infrastructure of a lunar outpost

A recent study made by ESA has reviewed the scientific investigations to be only, or best, performed on the Moon (Return to the Moon, ESA SP-1150, June 1992), and has identified the need for a manned lunar outpost to provide support to field geologists in sampling and in-situ observations of the lunar surface, and to allow the refurbishments of surface stations and rovers. Planning and development for a manned outpost on the Moon requires an in-depth understanding and analysis of the functions this outpost is expected to perform. We therefore analyzed the impact of the proposed scientific investigations on the design of a manned lunar outpost. The specific questions raised in our study were: What are the medical, physiological and psychological risks for a crew to stay and to work on the Moon? What transit and lunar surface infrastructures (habitats and vehicles) are needed to minimize those risks?     

Adaptational changes in the neural control of cardiorespiratory function in a confined environment: the CNEC#3 experiment

The goal of the study was to characterize the changes in neurovegetative control of the circulation, attending the presumed physiological and psychological stress originated by the isolation and confinement typical of the living condition of space stations, as simulated in a ground based unit, using time and frequency domain analysis. As a secondary goal we sought to verify the implementation of real time data acquisition, for off line spectral analisys of R-R interval, systolic arterial pressure (by Finapres) and respiration (by PVF2 piezoelectric sensors).

We addressed the cardiorespiratory and neurovegetative responses to standardized, simple Stressors (active standing, dynamic and static handgrip) on the EXEMSI 92 crew, before, during and after the isolation period.

On average the appropriate excitatory responses (to stand, dynamic and static handgrip) were elicited also in isolation and confinement.

Active standing and small masses muscular exercises are easy to be performed in a confined and isolated environment and provide a valuable tool for investigating the adaptational changes in neural control mechanisms.

The possibility there exists of using this time and frequency domain approach to monitor the level of performance and well being of the space crew in (quasi) real time.     

Chronic hyperhydration and hematological changes in trained subjects during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the hemoglobin content of endurance trained athletes during hypokinesia (decreased number of steps from 10,000 to 3000 steps per day). The studies were performed on 30 long-distance runners who had a VO2max average of 66 ml kg-1 min-1 and were in the age range of 19-24 years. Prior to their exposure to hypokinesia (HK) of 364 days, all volunteers were on an average of 10,000 steps per day. All volunteers were divided into three equal groups: the first group underwent normal ambulatory life (control subjects), the second group was kept under continuous restriction of motor activity (hypokinetic subjects), and the third group was placed under continuous restriction of motor activity and consumed 26 ml water kg-1 body weight daily and 0.1 g sodium chloride kg-1 body weight in the form of supplementation (hyperhydrated subjects). For simulation of the hypokinetic effect, the number of steps taken per day by the second and third groups of volunteers was restricted to an average of 3000. During the hypokinetic period we determined reticulocytes (Rt), hemoglobin (Hb), hematocrit (Hct), plasma volume (PV), red blood cell (RBC) mass and VO2max. In hyperhydrated volunteers the content of Hb and Hct decreased significantly, while PV, RBC mass and Rt count increased significantly. In hypokinetic volunteers Hb and Hct increased, while PV, RBC and Rt decreased significantly. It was concluded that chronic hyperhydration may be used to attentuate an increase in the Hb content of physically conditioned subjects during prolonged restriction of motor activity.     

Solar wind charge states measured by ULYSSES/SWICS in the south polar hole

The Ulysses mission now has an extensive data base covering several passes of the south polar coronal hole as the spacecraft proceeds to higher latitudes. Using composition measurements from the SWICS experiment on the Ulysses spacecraft, we have obtained charge state distributions, and hence inferred coronal ionization temperatures, for several solar wind species. In particular, we present an overview of Oxygen ionization temperature measurements, based on the O⁷⁺/O⁶⁺ ratio, for the period January 1993 until April 1994 (23°S to 61°S heliographic latitude), and detailed Oxygen, Silicon and Iron charge state distributions of the south polar hole during a two month period of nearly continuous hole coverage, Dec 1993–Jan 1994 (45°S to 52°S heliographic latitude).     

Study of distribution functions of interplanetary particles accelerated at co-rotating interaction region at∼5A.U.

We report the results of a study of the 12-hour average distribution functions of high Z nuclei as measured over a 10-day interval on the Ulysses spacecraft at a helioradius of5.2 A.U. We use the good time and atomic mass resolution of the composition aperture of the HI-SCALE instrument to determine the form of the distribution functions for C, O, Ne, Mg, Si, and Fe over the energy range 0.5–16 MeV/nucl. We find that the distribution functions of these ions can be organized by characteristic velocities that have values ranging between2000–3500 km/sec over this interval.     

Astrobiology from exobiology: Viking and the current Mars probes

The development of an Astrobiology Program is an extension of current exobiology programs. Astrobiology is the scientific study of the origin, distribution, evolution, and future of life in the universe. It encompasses exobiology; formation of elements, stars, planets, and organic molecules; initiation of replicating organisms; biological evolution; gravitational biology; and human exploration. Current interest in life on Mars provides the scientific community with an example of scientific inquiry that has mass appeal. Technology is mature enough to search for life in the universe.     

A systems and concurrent engineering framework for the integrated development of space products

This paper proposes a framework for the integrated development of space products. The framework is called ‘total view framework’ because it provides the total set of product, process and organisation elements and their interactions from the outset in the development process. It uses systems engineering (SE) and concurrent engineering (CE) in an integrated manner, as part of the same framework. The framework extends the application of the SE process to life cycle processes and their performing organisations and applies CE at all levels of the hierarchical product breakdown structure. The ‘total view framework’ is supported by a method, called ‘concurrent structured analysis method’, that consists of the three analysis processes: requirements, functional and physical. These processes mirror the bulk of the SE process and are applied concurrently to product, process and organisations. The outputs of the method are requirements, functional attributes, physical attributes and the interactions among them. These outputs are then analysed using a clustering algorithm and a complexity metric based on cohesion and coupling shows the clustering effects.