Engineering topics
Publications and source records attributed to Vernikos, Joan.
Based on the summaries presented in the above sections of what is still to be learned on the effects of artificial gravity on human functions, this chapter will discuss the short- and long-term steps of research required to understand fundamentals and to validate operational aspects of using artificial gravity as an effective countermeasure for long-duration space travel.
A human powered centrifuge has independently established turntable angular velocity and human power input. A control system allows excess input power to be stored as electric energy in a battery or dissipated as heat through a resistors. In a mechanical embodiment, the excess power is dissipated in a friction brake.
The National Aeronautics and Space Administration (NASA) has led the development of advanced imaging sensors and image processing technologies for space science and Earth science missions. NASA considers the transfer and commercialization of such technologies a fundamental mission of the agency. Over the last two years, efforts have been focused on the application of aerospace imaging and computing to the field of diagnostic imaging, specifically to breast cancer imaging. These technology transfer efforts offer significant promise in helping in the national public health priority of the early detection of breast cancer.
Continuous exposure to gravity may not be necessary to prevent the deconditioning effects of microgravity. It is not known, however, what the minimum gravity (G) exposure reguirements are, whether they vary for different physiological systems, or whether passive Gz (gravity in the head-to-toe vector) or activity in a G field is more effective in preventing deconditioning. It is also not known what the optimal characteristics of the G stimulus should be in terms of amplitude, duration, and frequency. To begin to address these questions, a 4-day -6 deg head-down bed rest (HDBR) study was conducted. Nine males (aged 30-50 yr) were subjected, over a period of seven months, to four different +1 Gz exposure protocols (periodic standing or controlled walking each for a total of 2 or 4 hr/day in individual 15-min doses), plus a control (0 Gz) of continuous HDBR. The study consisted of one ambulatory control day, 4 full days of -6 deg HDBR, and a recovery day when subjects were released at the end of HDBR after completion of tests. A battery of tests was selected and standardized in order to evaluate the known early responses to HDBR. Dependent variables of interest included orthostatic tolerance (30 min at 60 deg head-up tilt) and hemodynamics during head-up tilt, peak oxygen consumption (VO2(sub peak)) plasma volume (PV), and urinary calcium (Ca). The results were as follows: 4 hr standing completely prevented and 2 hr walking partially prevented post-HDBR orthostatic intolerance. Walking at 3 mi/hr for 4 hr/day provided no additional benefit. Intermittent walking attenuated, but did not prevent, the decrease in VO2(sub peak). Both 4 hr conditions showed less PV loss by the end of HDBR; both 2 hr conditions were without effect. Both 2 and 4 hr walking essentially prevented urinary Ca excretion and were more effective than standing. It is concluded that different physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz, and the intensity of the stimulus may be an important contributing factor.
With the advent of sophisticated space facilities we discuss the overall nature of some biological questions that can be addressed. We point out the need for broad participation by the biological community, the necessary facilities, and some unique requirements.
The nature of biological issues which can be addressed during long-term space missions is briefly discussed. These issues include structure, from cell to organ to organism; function, the regulation of systems such as immunology, neural sciences, and behavior; and reproduction and development.
The preparations for a manned mission of the length associated with travel to Mars will strongly focus on the human crew, in order to best support their technical, physical, and psychological needs. Advanced life-support systems for both internal and external operations will be critical in both the transit vehicle and planetary surface habitat. Not only individual systems, but how they mutually interact and in turn affect the crew, will shape not only habitats but realistically foreseeable mission objectives. The long-term habitability of all accommodations will be a far more prominent design criterion than heretofore for the relevant engineering disciplines.
The study of man in spaceflight has consistently indicated changes in fluid and electrolyte balance. Sodium (Na), Potassium (K), and Calcium (Ca) excretion are increased, accompanied by changes in the levels and responsiveness of adrenal hormones and the sympathetic nervous system (SNS). These hormones and neurohumors are critical to the regulation of blood pressure, blood flow, and blood volume. The primary objectives of the research conducted under this task have been to use -6 deg head down bedrest (BR) as the analog to spaceflight, to determine the long term changes in these systems, their relationship to orthostatic tolerance, and to develop and test suitable countermeasures.
Gastric ulceration produced by aspirin and indomethacin was compared in acutely stressed and non-stressed rats. We found a synergism between these anti-inflammatory agents and acute stress in the production of gastric ulcers. Even at relatively high doses, neither agent caused appreciable gastric damage in non-stressed rats, whereas moderate doses of both agents produced massive ulceration in stressed rats. The synergism appears unrelated to the effect of these agents on the pituitary-adrenal response. The size and regional distribution of ulcers produced by aspirin and indomethacin in stressed rats were comparable. However, the dose--response curves of the two drugs were markedly dissimilar. Furthermore, the ulceration produced by indomethacin was attenuated by both H(sub 1) and H(sub 2) histamine receptor antagonists, whereas ulceration produced by aspirin was attenuated only by an H(sub 2) antagonist. The results suggest that the ulcerogenic mechanism of indomethacin may differ from that of aspirin and add to the growing evidence on the importance of endogenous histamine in various forms of gastric ulceration.