Scientific Prerequisites for the Human Exploration of Space (1993) / Chapter Skim
Currently Skimming:
2 CRITICAL RESEARCH REQUIREMENTS
2 CRITICAL RESEARCH REQUIREMENTS
Pages 15-32
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 15... ...
Please use the print version of this publication as the authoritative version for attribution. 2 Critical Research Requirements The cardinal consideration in any discussion of prolonged human exploration is the safety and well-being of the crew.
|
From page 16... ...
CHEX recommends that those implementing a Moon/Mars program commit to and lead a comprehensive program of basic and applied life-sciences research on the effects on human physiology of the microgravity, reduced gravity, and space-radiation environment prior to finalizing spacecraft designs or undertaking long-duration flights. For this purpose, a long-term research program in adaptation to microgravity and reduced gravity, properly conducted in a suitably equipped space station in low Earth orbit, will be required.
|
From page 17... ...
Please use the print version of this publication as the authoritative version for attribution. RADIATION Bombardment by energetic particles is a major hazard facing space travellers.4 Indeed, NASA has recognized that the cumulative radiation dose "will probably be the ultimate limiting factor for human exploration."5 Humans conducting extended space voyages face two different radiation hazards: a protracted exposure to galactic cosmic rays at a low dose rate and some probability of exposure to considerably higher doses of solar energetic particles.
|
From page 18... ...
NASA's current limits correspond to a 3% excess risk of eventual death due to cancer and are about 10 times that allowed for terrestrial radiation workers and about 100 times that allowed for the general population. Sources of Hazardous Radiation As mentioned above, two types of radiation are hazardous to astronauts -- galactic cosmic rays and solar energetic particles.
|
From page 19... ...
of the radiation dose equivalent received from galactic cosmic rays at a depth of 5 cm in body tissue (representative of, for example, bone marrow) versus aluminum shielding thickness during the 1977 solar activity minimum.
|
From page 20... ...
Before any final conclusions on mission timing are drawn, the probability of solar-flare occurrence must be considered along with the uncertainties in cosmic-ray fluxes, their modulation, attenuation, and fragmentation in shielding, and biological effects. Solar Energetic Particles The intensity, spectra, and composition of energetic particles from solar flares are much more variable than those of galactic cosmic rays.
|
From page 21... ...
Tsao, "Galactic Cosmic Radiation Doses to Astronauts Outside the Magnetosphere," in Terrestrial Space Radiation and Its Biological Effects, P.D. McCormack, C.E.
|
From page 22... ...
These include the following: • The fluxes of cosmic-ray nuclei (especially oxygen through iron) should be measured throughout the 22-year magnetic solar cycle using a new generation of instruments with large geometric factors, such as NASA's planned Advanced Composition Explorer; • Measurements of the intensities of the electron and positron components of galactic cosmic rays over most of a 22-year cycle would separate charge-sign-dependent effects from other cosmic-ray propagation effects, thereby leading to better understanding of the modulation process; • Measurement of the galactic cosmic-ray intensities beyond the boundary of the heliosphere would establish an upper limit to the radiation intensity independent of its modulation by the solar wind and magnetic field.
|
From page 23... ...
warning system because it would allow modeling and predictions of the paths taken by energetic particles as they are channeled from flare sites into interplanetary space. The coronagraph would allow coronal mass ejections (CMEs)
|
From page 24... ...
At present, our understanding of the causes of space-induced osteopenia and muscle atrophy is inadequate to devise effective countermeasures to be taken on long-duration space missions. Also lacking are data on the temporal sequence of bone remodeling and muscle atrophy in prolonged exposure to microgravity and the ways in which these processes may depend on other risk factors such as age, gender, race, or nutrition.
|
From page 25... ...
Although such an environment could correct bone degeneration, muscle atrophy, and other changes due to microgravity, it could also exacerbate other effects not now perceived to be major problems. Head movements made in a spinning environment or Coriolis effects can lead to disturbing vestibular sensations and motion sickness.
|
From page 26... ...
following short flights but can take as long as 30 days following long flights. The potential exists for permanent impairment following prolonged adaptation to microgravity.
|
From page 27... ...
; 5. Peripheral resistance (resistance offered to blood flow through the circulatory system)
|
From page 28... ...
Only limited progress has been made since publication in 1987 of the Committee on Space Biology and Medicine research strategy, which included a chapter on human behavior. Because of the limited number and duration of American spaceflights, systematic research in this field could be conducted in analog environments such as polar stations, undersea habitats, and aviation settings.
|
From page 29... ...
Studies are needed to determine the optimal environmental conditions necessary to create the sense of normal circadian rhythms within the body during long-duration space missions. Group Factors Even the most technically competent and highly motivated individuals do not necessarily perform effectively and harmoniously when sequestered for prolonged periods in a confined environment.
|
From page 30... ...
The protocols for the preparation of Mars-bound craft or the handling of martian samples returned to Earth will depend both on the relevant planetary protection regulations promulgated by the Committee on Space Research (COSPAR) and on public perception of the risks.
|
From page 31... ...
How to detect the presence of indigenous microorganisms (potential pathogens) and their activities in samples returned to Earth prior to a human visit to Mars.
|
From page 32... ...
Streitmatter, "The Absolute Spectra of Galactic Cosmic Rays at Solar Minimum and Their Implications for Manned Space Flight," Galactic Cosmic Radiation Constraints on Space Exploration, NRL Publication 209–4154, Naval Research Laboratory, Washington, D.C., November 1991.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.