CRV investment offers safe return

The development and testing of a new emergency Crew Return Vehicle (CRV) prototype is discussed. The new CRV is being developed by NASA and ESA and is designed for use on the International Space Station as a supplement to the Soyuz ships of the Russians, which accommodate only three passengers. The new vehicle will provide a shirt-sleeve environment for up to six astronauts and will allow for emergency medical treatment to be provided.     

Effect of microgravity on Escherichia coli and MS-2 bacteriophage disinfection by iodinated resins

Experiments on chemical disinfection by iodinated resins were conducted on STS 50 (USML-1), which flew a 13 day mission during 1992. Fluid processing apparatus containing microorganisms and iodinated resins was assembled in either Manhattan, Kansas, or Boulder, Colorado, and loaded on-board the Space Shuttle for the mission. Pentaiodide resin was more effective than the triiodide resin against Escherichia coli. Both resins were more effective bactericides at unit gravity than microgravity because of cosedimentation of bacteria and iodinated resin beads. In bacteriophage experiments, the triiodide resin reduced the viable titer of MS-2 by nine logs. The few viable phage surviving chemical disinfection were associated with precipitant formation in the fluid processing apparatus.     

Radiative and hybrid cooling of infrared space telescopes

The designs of cold space telescopes, cryogenic and radiatively cooled, are similar in most elements and both benefit from orbits distant from the Earth. In particular such orbits allow the anti-sunward side of radiatively-cooled spacecraft to be used to provide large cooling radiators for the individual radiation shields. Designs incorporating these features have predictedT _tel near 20 K. The attainability of such temperatures is supported by limited practical experience (IRAS, COBE). Supplementary cooling systems (cryogens, mechanical coolers) can be advantageously combined with radiative cooling in hybrid designs to provide robustness against deterioration and yet lower temperatures for detectors, instruments, and even the whole telescope. The possibility of such major additional gains is illustrated by the Very Cold Telescope option under study forEdison, which should offerT _tel5 K for a little extra mechanical cooling capacity.     

Biological responses to space: results of the experiment "Exobiological Unit" of ERA on EURECA I.

Spores of different strains of Bacillus subtilis and the Escherichia coli plasmid pUC19 were exposed to selected conditions of space (space vacuum and/or defined wavebands and intensities of solar ultraviolet radiation) in the experiment ER 161 "Exobiological Unit" of the Exobiology Radiation Assembly (ERA) on board of the European Retrievable Carrier (EURECA). After the approximately 11 months lasting mission, their responses were studied in terms of survival, mutagenesis in the his (B. subtilis) or lac locus (pUC19), induction of DNA strand breaks, efficiency of DNA repair systems, and the role of external protective agents. The data were compared with those of a simultaneously running ground control experiment. The survival of spores treated with the vacuum of space, however shielded against solar radiation, is substantially increased, if they are exposed in multilayers and/or in the presence of glucose as protective, whereas all spores in "artificial meteorites", i.e. embedded in clays or simulated Martian soil, are killed. Vacuum treatment leads to an increase of mutation frequency in spores, but not in plasmid DNA. Extraterrestrial solar ultraviolet radiation is mutagenic, induces strand breaks in the DNA and reduces survival substantially; however, even at the highest fluences, i.e. 3 x 10(8) J m-2, a small but significant fraction of spores survives the insolation. Action spectroscopy confirms results of previous space experiments of a synergistic action of space vacuum and solar UV radiation with DNA being the critical target.     

Biochemical constraints for survival under Martian conditions.

A wide variety of terrestrial organisms, the so-called "anhydrobiotes," has learned to survive in a state of extreme dehydration in dry environments. Strategies for survival include the accumulation of certain polyols and nonreducing saccharides, which help to prevent damage to membranes and proteins, but at low water partial pressure DNA is also progressively damaged by various lesions, including strand breaks and cross-linking to proteins. These lesions, if they are not too numerous, can be repaired before the first replication step after rehydration, but long-term exposure to dry conditions finally diminishes the chances of survival as these lesions accumulate. If an organism has no chance to repair the accumulated DNA damage during intermittent periods of active life, survival will not exceed a few decades. The restriction of survival by dryness-induced DNA lesions is corroborated by new data on conidia of Aspergillus and the free plasmid pBR 322. Our results will be discussed with respect to the chance of finding dormant life or biochemical fossils on the surface of Mars.     

Human productivity in space and systems costs

Human productivity during assembly operations in-orbit is dependent on limits set by fatigue, metabolic rates, learning, and assembly techniques. In order to quantify these effects, tests were conducted in the NASA MSFC Neutral Buoyancy Simulator, in the NASA KC-135 in parabolic flight, and in space with the EASE program during the Shuttle Atlantis mission 61-B. A separate program attempted to relate productivity to system costs. Because of the surprisingly high productivity which had been demonstrated in orbit, it was shown that assembly operations would have only a small effect on system costs at the present level of launch costs. The results of these continuing studies have been reported in a recent paper(1). They will be briefly summarized here and the results updated to include additional cost elements and to examine the effects of reductions in transportation costs, resulting from advances in technology and from increased demand, on system costs. It is shown that, as launch costs are reduced, the assembly costs could become an increasingly important component of the total system costs.     

Influence of graviceptives cues at different level of visual information processing: the effect of prolonged weightlessness

We evaluated the influence of prolonged weightlessness on the performance of visual tasks in the course of the Russian-French missions ANTARES, Post-ANTARES and ALTAIR aboard the MIR station. Eight cosmonauts were subjects in two experiments executed pre-flight, in-flight and post-flight sessions.

In the first experiment, cosmonauts performed a task of symmetry detection in 2-D polygons. The results indicate that this detection is locked in a head retinal reference frame rather than in an environmentally defined one as meridional orientations of symmetry axis (vertical and horizontal) elicited faster response times than oblique ones. However, in weightlessness the saliency of a retinally vertical axis of symmetry is no longer significantly different from an horizontal axis. In the second experiment, cosmonauts performed a mental rotation task in which they judged whether two 3-D objects presented in different orientations were identical. Performance on this task is basically identical in weightlessness and normal gravity.     

The effect of head-down tilt on brain potentials related to visual attention

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) in a simple visual selective response task were compared between HDT and HUT in 9 normal subjects. The results were: The Target(T) and non-Target(NT) flash signals both induced significant slow positive potentials which were supposed to related to the attention state; the amplitude of the positive potentials in frontal regions decreased significantly especially for NT-ERPs during HDT comprared with that during HUT. The data reported provide new evidence indicating that more attention should be paid on the brain function study during space flight.     

Life in space may help life on Earth

Teams of chronobiologists from the U.S., Russia, and Japan are working toward a remote computerized health care system which, once tested in space, may change how doctors diagnose and treat cardiovascular diseases, including hypertension and conditions predisposing stroke. The system is based on ongoing research indicating that swings in blood pressure charted over a span of 24 hr or longer, rather than a single systolic and diastolic reading, can reveal a new major risk factor for heart disease.     

Effect of potassium and calcium loading on healthy subjects under hypokinesia and physical exercise with fluid and salt supplements

The objective of this investigation was to determine the acute responses to the electrolyte challenges under hypokinesia and physical exercise (PE) of different intensities with fluid and salt supplementation (FSS). The studies were performed on 12 physically healthy male volunteers aged 19-24 years under 364 days of hypokinesia (decreased number of steps per day) with a set of PE with FSS. The volunteers were divided into two equal groups. The first group was subjected to a set of intensive PE and the second group was submitted to a set of moderate PE. Both groups of subjects consumed daily water and salt supplements that aimed to increase the body hydration level. For simulation of the hypokinetic effect all subjects were kept under an average of 3000 steps per day. Functional tests with a potassium chloride (KCl) and calcium lactate (Cal) load were performed during the hypokinetic period of 364 days and the 60-day, prehypokinetic period that served as control, while both groups of subjects consumed daily calcium and potassium supplements. The concentration of electrolyte and hormone levels in the blood and their excretion rate in urine were determined. Renal excretion of calcium and potassium and the blood concentration thereof increased markedly in both groups of subjects. With the potassium chloride load tests the increased potassium excretion was accompanied by higher aldosterone and insulin blood levels, and with the calcium lactate load tests the increased calcium excretion was accompanied by a decreased parathyroid content in the blood. FSS and PE, regardless of intensity, failed to attenuate calcium and potassium losses. Additional intake of KCl and Cal also failed to normalize potassium and calcium abnormalities. It was concluded that during the KCl and Cal loading tests, the increased losses of potassium and calcium in the hypokinetic subjects were due to the inability of their bodies to retain these electrolytes, and that electrolyte abnormalities could not be reversed by PE or rehydration in individuals subjected to prolonged restriction of motor activity.