BIOLOGICAL EFFECTS OF SPACE RADIATION1Radiation sources in space are of three types: galactic cosmic radiation, Van Allen belts, and solar flares with an intense proton flux. Cosmic radiation has higher energy levels than radiation produced by manmade accelerators.The Panel on Radiation Biology, while recognizing the need for radiobiological studies of an applied nature with reference to manned flight programs, stated that it would be shortsighted for the United States to confine its efforts to the solution of immediate problems since, in the long run, successful exploration of space will be aided by the contributions of basic research. Both the immediate biological research program and the continuing program for basic studies should be built upon the large body of existing knowledge of radiation effects. The attitude that all radiobiological experiments need be repeated in the space environment should be resolutely rejected. Since fundamental radiobiology cannot be performed easily in space, it has been recommended that, wherever possible, these investigations be carried out in ground laboratories in preference to flying laboratories.Space environment does vary from the terrestrial environment, but the variations are not so great as to lead to the expectation of strikinglydifferent biological effects of radiation in space. However, it is conceivable that radiations whose effects are well known under terrestrial conditions may have some unsuspected biological effects when combined with unusual features of the space environment: e.g., zero g. Previous space radiobiological studies have depended solely on very low and inaccurately measured doses of ambient space radiation. It has been difficult to distinguish between the observed response levels and the random noise; thus, experiments have been inconclusive.Biological Effects of Heavy Ions and MesonsThe biological effects of heavy ions (especially Z>2) and mesons are of specific interest to space radiobiology.Controlled Radiobiological Experiments in SpaceThere is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study. Experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability: (1) the use of well-known biological systems, e.g., mutation induction or chromosome breakage; (2) the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results; (3) the exposure of the system to known quantities and qualities of radiation; (4) the use of adequate controls.High-altitude balloon ascents of the 1930's initiated study of the biological effects of cosmic rays. They were limited to the exploration of secondary cosmic radiation effects. After World War II, the research extended to the use of V-2 rockets fired from the White Sands Proving Ground. Interest returned to balloons and a significant program was underway by 1950, first using mice and then hamsters, fruit flies, cats, and dogs. These flights gave no evidence of radiation damage. However, it was realized that the flights were too far south to obtain a significant exposure, and more northerly flights began in 1953. Mice and guinea pigs were flown on these later flights. Chase ([ref.68]) showed the most unequivocal results to that time, a statistically significant increase in light hairs on black animals and the streaks of white hair up to 10 times wider than expected. Brain lesions were detected in the guinea pigs flown on Man High in 1957. Many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation.From the earlier V-2 rocket flights to the Jupiter missile launchings of the monkeys Able and Baker, cosmic-ray research was continued, but theshort flight durations of these vehicles did not provide substantial information. The USAF Discoverer satellite program has given impetus to cosmic-ray research and provided for longer "staytimes."It has been difficult to separate radiation effects from other space-flight factors: therefore, some of the alterations observed are still subject to debate. Vibration, acceleration, and weightlessness appear to be the three most important additional parameters. Measurements of radiation dosage have been made by chemical and photographic dosimetry, ion chambers, and biological dosimetry. All evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to 200 nautical miles. Most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects. The biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man. The studies have required much of the space and weight resources allotted biology by the U.S.S.R. and the United States. They have been accompanied by ground-based controls.The Vostok series provided the following data:A small, but statistically significant, increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination. In this case only, the increase did not depend on flight duration.Lysogenic bacteria exhibited an increase of genetic alterations and increased phage production. Length of flight was associated with increased bacteriophage production by the lysogenic bacteria. There was an increase of recessive lethals coupled with nonconvergence of chromosomes (sex linked) in the fruit fly. A stimulation of cell division in wheat and pea seeds was observed. Cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate, percentage of mortality and morphological, antigenic, and cultural properties. Repeated flights of the identical HeLa cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all.The most definite radiation effects observed were only revealed in genetic tests. No harmful influence on those characteristics affecting the viability of the organism has been discovered.The Air Force Discoverer series launched from the west coast had a few successful flights incorporating organisms. With severe environmental stress and long recovery times, data on radiation exposure were equivocal up to Discoverer XVII and XVIII when cultures of humantissue were flown, recovered, and assessed for radiation exposure effects. Comparison with ground-based controls revealed no measurable differences.Radiation dosimetry from the Mercury series established that minimal exposures were encountered at those orbital altitudes. A typical example is the MA-8 flight of W. M. Schirra, Jr., during which the body surface dosage was less than 30 millirads.NASA has supported fundamental radiation studies at the Oak Ridge National Laboratory and the Lawrence Radiation Laboratory. Emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators.At the NASA Ames Research Center extensive fundamental studies are being carried out on the effects of radiation, especially in the nervous system. It has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after X-irradiation. These deposits, referred to as a "chemical lesion," result from an accumulation of glycogen. The formation of these deposits during exposure to large doses of X-irradiation was not increased in environments of 99.5 percent oxygen and increased atmospheric pressure.
BIOLOGICAL EFFECTS OF SPACE RADIATION1Radiation sources in space are of three types: galactic cosmic radiation, Van Allen belts, and solar flares with an intense proton flux. Cosmic radiation has higher energy levels than radiation produced by manmade accelerators.The Panel on Radiation Biology, while recognizing the need for radiobiological studies of an applied nature with reference to manned flight programs, stated that it would be shortsighted for the United States to confine its efforts to the solution of immediate problems since, in the long run, successful exploration of space will be aided by the contributions of basic research. Both the immediate biological research program and the continuing program for basic studies should be built upon the large body of existing knowledge of radiation effects. The attitude that all radiobiological experiments need be repeated in the space environment should be resolutely rejected. Since fundamental radiobiology cannot be performed easily in space, it has been recommended that, wherever possible, these investigations be carried out in ground laboratories in preference to flying laboratories.Space environment does vary from the terrestrial environment, but the variations are not so great as to lead to the expectation of strikinglydifferent biological effects of radiation in space. However, it is conceivable that radiations whose effects are well known under terrestrial conditions may have some unsuspected biological effects when combined with unusual features of the space environment: e.g., zero g. Previous space radiobiological studies have depended solely on very low and inaccurately measured doses of ambient space radiation. It has been difficult to distinguish between the observed response levels and the random noise; thus, experiments have been inconclusive.Biological Effects of Heavy Ions and MesonsThe biological effects of heavy ions (especially Z>2) and mesons are of specific interest to space radiobiology.Controlled Radiobiological Experiments in SpaceThere is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study. Experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability: (1) the use of well-known biological systems, e.g., mutation induction or chromosome breakage; (2) the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results; (3) the exposure of the system to known quantities and qualities of radiation; (4) the use of adequate controls.High-altitude balloon ascents of the 1930's initiated study of the biological effects of cosmic rays. They were limited to the exploration of secondary cosmic radiation effects. After World War II, the research extended to the use of V-2 rockets fired from the White Sands Proving Ground. Interest returned to balloons and a significant program was underway by 1950, first using mice and then hamsters, fruit flies, cats, and dogs. These flights gave no evidence of radiation damage. However, it was realized that the flights were too far south to obtain a significant exposure, and more northerly flights began in 1953. Mice and guinea pigs were flown on these later flights. Chase ([ref.68]) showed the most unequivocal results to that time, a statistically significant increase in light hairs on black animals and the streaks of white hair up to 10 times wider than expected. Brain lesions were detected in the guinea pigs flown on Man High in 1957. Many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation.From the earlier V-2 rocket flights to the Jupiter missile launchings of the monkeys Able and Baker, cosmic-ray research was continued, but theshort flight durations of these vehicles did not provide substantial information. The USAF Discoverer satellite program has given impetus to cosmic-ray research and provided for longer "staytimes."It has been difficult to separate radiation effects from other space-flight factors: therefore, some of the alterations observed are still subject to debate. Vibration, acceleration, and weightlessness appear to be the three most important additional parameters. Measurements of radiation dosage have been made by chemical and photographic dosimetry, ion chambers, and biological dosimetry. All evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to 200 nautical miles. Most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects. The biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man. The studies have required much of the space and weight resources allotted biology by the U.S.S.R. and the United States. They have been accompanied by ground-based controls.The Vostok series provided the following data:A small, but statistically significant, increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination. In this case only, the increase did not depend on flight duration.Lysogenic bacteria exhibited an increase of genetic alterations and increased phage production. Length of flight was associated with increased bacteriophage production by the lysogenic bacteria. There was an increase of recessive lethals coupled with nonconvergence of chromosomes (sex linked) in the fruit fly. A stimulation of cell division in wheat and pea seeds was observed. Cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate, percentage of mortality and morphological, antigenic, and cultural properties. Repeated flights of the identical HeLa cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all.The most definite radiation effects observed were only revealed in genetic tests. No harmful influence on those characteristics affecting the viability of the organism has been discovered.The Air Force Discoverer series launched from the west coast had a few successful flights incorporating organisms. With severe environmental stress and long recovery times, data on radiation exposure were equivocal up to Discoverer XVII and XVIII when cultures of humantissue were flown, recovered, and assessed for radiation exposure effects. Comparison with ground-based controls revealed no measurable differences.Radiation dosimetry from the Mercury series established that minimal exposures were encountered at those orbital altitudes. A typical example is the MA-8 flight of W. M. Schirra, Jr., during which the body surface dosage was less than 30 millirads.NASA has supported fundamental radiation studies at the Oak Ridge National Laboratory and the Lawrence Radiation Laboratory. Emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators.At the NASA Ames Research Center extensive fundamental studies are being carried out on the effects of radiation, especially in the nervous system. It has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after X-irradiation. These deposits, referred to as a "chemical lesion," result from an accumulation of glycogen. The formation of these deposits during exposure to large doses of X-irradiation was not increased in environments of 99.5 percent oxygen and increased atmospheric pressure.
BIOLOGICAL EFFECTS OF SPACE RADIATION1Radiation sources in space are of three types: galactic cosmic radiation, Van Allen belts, and solar flares with an intense proton flux. Cosmic radiation has higher energy levels than radiation produced by manmade accelerators.The Panel on Radiation Biology, while recognizing the need for radiobiological studies of an applied nature with reference to manned flight programs, stated that it would be shortsighted for the United States to confine its efforts to the solution of immediate problems since, in the long run, successful exploration of space will be aided by the contributions of basic research. Both the immediate biological research program and the continuing program for basic studies should be built upon the large body of existing knowledge of radiation effects. The attitude that all radiobiological experiments need be repeated in the space environment should be resolutely rejected. Since fundamental radiobiology cannot be performed easily in space, it has been recommended that, wherever possible, these investigations be carried out in ground laboratories in preference to flying laboratories.Space environment does vary from the terrestrial environment, but the variations are not so great as to lead to the expectation of strikinglydifferent biological effects of radiation in space. However, it is conceivable that radiations whose effects are well known under terrestrial conditions may have some unsuspected biological effects when combined with unusual features of the space environment: e.g., zero g. Previous space radiobiological studies have depended solely on very low and inaccurately measured doses of ambient space radiation. It has been difficult to distinguish between the observed response levels and the random noise; thus, experiments have been inconclusive.Biological Effects of Heavy Ions and MesonsThe biological effects of heavy ions (especially Z>2) and mesons are of specific interest to space radiobiology.Controlled Radiobiological Experiments in SpaceThere is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study. Experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability: (1) the use of well-known biological systems, e.g., mutation induction or chromosome breakage; (2) the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results; (3) the exposure of the system to known quantities and qualities of radiation; (4) the use of adequate controls.High-altitude balloon ascents of the 1930's initiated study of the biological effects of cosmic rays. They were limited to the exploration of secondary cosmic radiation effects. After World War II, the research extended to the use of V-2 rockets fired from the White Sands Proving Ground. Interest returned to balloons and a significant program was underway by 1950, first using mice and then hamsters, fruit flies, cats, and dogs. These flights gave no evidence of radiation damage. However, it was realized that the flights were too far south to obtain a significant exposure, and more northerly flights began in 1953. Mice and guinea pigs were flown on these later flights. Chase ([ref.68]) showed the most unequivocal results to that time, a statistically significant increase in light hairs on black animals and the streaks of white hair up to 10 times wider than expected. Brain lesions were detected in the guinea pigs flown on Man High in 1957. Many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation.From the earlier V-2 rocket flights to the Jupiter missile launchings of the monkeys Able and Baker, cosmic-ray research was continued, but theshort flight durations of these vehicles did not provide substantial information. The USAF Discoverer satellite program has given impetus to cosmic-ray research and provided for longer "staytimes."It has been difficult to separate radiation effects from other space-flight factors: therefore, some of the alterations observed are still subject to debate. Vibration, acceleration, and weightlessness appear to be the three most important additional parameters. Measurements of radiation dosage have been made by chemical and photographic dosimetry, ion chambers, and biological dosimetry. All evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to 200 nautical miles. Most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects. The biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man. The studies have required much of the space and weight resources allotted biology by the U.S.S.R. and the United States. They have been accompanied by ground-based controls.The Vostok series provided the following data:A small, but statistically significant, increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination. In this case only, the increase did not depend on flight duration.Lysogenic bacteria exhibited an increase of genetic alterations and increased phage production. Length of flight was associated with increased bacteriophage production by the lysogenic bacteria. There was an increase of recessive lethals coupled with nonconvergence of chromosomes (sex linked) in the fruit fly. A stimulation of cell division in wheat and pea seeds was observed. Cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate, percentage of mortality and morphological, antigenic, and cultural properties. Repeated flights of the identical HeLa cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all.The most definite radiation effects observed were only revealed in genetic tests. No harmful influence on those characteristics affecting the viability of the organism has been discovered.The Air Force Discoverer series launched from the west coast had a few successful flights incorporating organisms. With severe environmental stress and long recovery times, data on radiation exposure were equivocal up to Discoverer XVII and XVIII when cultures of humantissue were flown, recovered, and assessed for radiation exposure effects. Comparison with ground-based controls revealed no measurable differences.Radiation dosimetry from the Mercury series established that minimal exposures were encountered at those orbital altitudes. A typical example is the MA-8 flight of W. M. Schirra, Jr., during which the body surface dosage was less than 30 millirads.NASA has supported fundamental radiation studies at the Oak Ridge National Laboratory and the Lawrence Radiation Laboratory. Emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators.At the NASA Ames Research Center extensive fundamental studies are being carried out on the effects of radiation, especially in the nervous system. It has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after X-irradiation. These deposits, referred to as a "chemical lesion," result from an accumulation of glycogen. The formation of these deposits during exposure to large doses of X-irradiation was not increased in environments of 99.5 percent oxygen and increased atmospheric pressure.
Radiation sources in space are of three types: galactic cosmic radiation, Van Allen belts, and solar flares with an intense proton flux. Cosmic radiation has higher energy levels than radiation produced by manmade accelerators.
The Panel on Radiation Biology, while recognizing the need for radiobiological studies of an applied nature with reference to manned flight programs, stated that it would be shortsighted for the United States to confine its efforts to the solution of immediate problems since, in the long run, successful exploration of space will be aided by the contributions of basic research. Both the immediate biological research program and the continuing program for basic studies should be built upon the large body of existing knowledge of radiation effects. The attitude that all radiobiological experiments need be repeated in the space environment should be resolutely rejected. Since fundamental radiobiology cannot be performed easily in space, it has been recommended that, wherever possible, these investigations be carried out in ground laboratories in preference to flying laboratories.
Space environment does vary from the terrestrial environment, but the variations are not so great as to lead to the expectation of strikinglydifferent biological effects of radiation in space. However, it is conceivable that radiations whose effects are well known under terrestrial conditions may have some unsuspected biological effects when combined with unusual features of the space environment: e.g., zero g. Previous space radiobiological studies have depended solely on very low and inaccurately measured doses of ambient space radiation. It has been difficult to distinguish between the observed response levels and the random noise; thus, experiments have been inconclusive.
Biological Effects of Heavy Ions and MesonsThe biological effects of heavy ions (especially Z>2) and mesons are of specific interest to space radiobiology.
The biological effects of heavy ions (especially Z>2) and mesons are of specific interest to space radiobiology.
Controlled Radiobiological Experiments in SpaceThere is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study. Experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability: (1) the use of well-known biological systems, e.g., mutation induction or chromosome breakage; (2) the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results; (3) the exposure of the system to known quantities and qualities of radiation; (4) the use of adequate controls.High-altitude balloon ascents of the 1930's initiated study of the biological effects of cosmic rays. They were limited to the exploration of secondary cosmic radiation effects. After World War II, the research extended to the use of V-2 rockets fired from the White Sands Proving Ground. Interest returned to balloons and a significant program was underway by 1950, first using mice and then hamsters, fruit flies, cats, and dogs. These flights gave no evidence of radiation damage. However, it was realized that the flights were too far south to obtain a significant exposure, and more northerly flights began in 1953. Mice and guinea pigs were flown on these later flights. Chase ([ref.68]) showed the most unequivocal results to that time, a statistically significant increase in light hairs on black animals and the streaks of white hair up to 10 times wider than expected. Brain lesions were detected in the guinea pigs flown on Man High in 1957. Many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation.From the earlier V-2 rocket flights to the Jupiter missile launchings of the monkeys Able and Baker, cosmic-ray research was continued, but theshort flight durations of these vehicles did not provide substantial information. The USAF Discoverer satellite program has given impetus to cosmic-ray research and provided for longer "staytimes."It has been difficult to separate radiation effects from other space-flight factors: therefore, some of the alterations observed are still subject to debate. Vibration, acceleration, and weightlessness appear to be the three most important additional parameters. Measurements of radiation dosage have been made by chemical and photographic dosimetry, ion chambers, and biological dosimetry. All evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to 200 nautical miles. Most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects. The biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man. The studies have required much of the space and weight resources allotted biology by the U.S.S.R. and the United States. They have been accompanied by ground-based controls.The Vostok series provided the following data:A small, but statistically significant, increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination. In this case only, the increase did not depend on flight duration.Lysogenic bacteria exhibited an increase of genetic alterations and increased phage production. Length of flight was associated with increased bacteriophage production by the lysogenic bacteria. There was an increase of recessive lethals coupled with nonconvergence of chromosomes (sex linked) in the fruit fly. A stimulation of cell division in wheat and pea seeds was observed. Cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate, percentage of mortality and morphological, antigenic, and cultural properties. Repeated flights of the identical HeLa cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all.The most definite radiation effects observed were only revealed in genetic tests. No harmful influence on those characteristics affecting the viability of the organism has been discovered.The Air Force Discoverer series launched from the west coast had a few successful flights incorporating organisms. With severe environmental stress and long recovery times, data on radiation exposure were equivocal up to Discoverer XVII and XVIII when cultures of humantissue were flown, recovered, and assessed for radiation exposure effects. Comparison with ground-based controls revealed no measurable differences.Radiation dosimetry from the Mercury series established that minimal exposures were encountered at those orbital altitudes. A typical example is the MA-8 flight of W. M. Schirra, Jr., during which the body surface dosage was less than 30 millirads.NASA has supported fundamental radiation studies at the Oak Ridge National Laboratory and the Lawrence Radiation Laboratory. Emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators.At the NASA Ames Research Center extensive fundamental studies are being carried out on the effects of radiation, especially in the nervous system. It has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after X-irradiation. These deposits, referred to as a "chemical lesion," result from an accumulation of glycogen. The formation of these deposits during exposure to large doses of X-irradiation was not increased in environments of 99.5 percent oxygen and increased atmospheric pressure.
There is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study. Experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability: (1) the use of well-known biological systems, e.g., mutation induction or chromosome breakage; (2) the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results; (3) the exposure of the system to known quantities and qualities of radiation; (4) the use of adequate controls.
High-altitude balloon ascents of the 1930's initiated study of the biological effects of cosmic rays. They were limited to the exploration of secondary cosmic radiation effects. After World War II, the research extended to the use of V-2 rockets fired from the White Sands Proving Ground. Interest returned to balloons and a significant program was underway by 1950, first using mice and then hamsters, fruit flies, cats, and dogs. These flights gave no evidence of radiation damage. However, it was realized that the flights were too far south to obtain a significant exposure, and more northerly flights began in 1953. Mice and guinea pigs were flown on these later flights. Chase ([ref.68]) showed the most unequivocal results to that time, a statistically significant increase in light hairs on black animals and the streaks of white hair up to 10 times wider than expected. Brain lesions were detected in the guinea pigs flown on Man High in 1957. Many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation.
From the earlier V-2 rocket flights to the Jupiter missile launchings of the monkeys Able and Baker, cosmic-ray research was continued, but theshort flight durations of these vehicles did not provide substantial information. The USAF Discoverer satellite program has given impetus to cosmic-ray research and provided for longer "staytimes."
It has been difficult to separate radiation effects from other space-flight factors: therefore, some of the alterations observed are still subject to debate. Vibration, acceleration, and weightlessness appear to be the three most important additional parameters. Measurements of radiation dosage have been made by chemical and photographic dosimetry, ion chambers, and biological dosimetry. All evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to 200 nautical miles. Most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects. The biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man. The studies have required much of the space and weight resources allotted biology by the U.S.S.R. and the United States. They have been accompanied by ground-based controls.
The Vostok series provided the following data:
A small, but statistically significant, increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination. In this case only, the increase did not depend on flight duration.
Lysogenic bacteria exhibited an increase of genetic alterations and increased phage production. Length of flight was associated with increased bacteriophage production by the lysogenic bacteria. There was an increase of recessive lethals coupled with nonconvergence of chromosomes (sex linked) in the fruit fly. A stimulation of cell division in wheat and pea seeds was observed. Cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate, percentage of mortality and morphological, antigenic, and cultural properties. Repeated flights of the identical HeLa cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all.
The most definite radiation effects observed were only revealed in genetic tests. No harmful influence on those characteristics affecting the viability of the organism has been discovered.
The Air Force Discoverer series launched from the west coast had a few successful flights incorporating organisms. With severe environmental stress and long recovery times, data on radiation exposure were equivocal up to Discoverer XVII and XVIII when cultures of humantissue were flown, recovered, and assessed for radiation exposure effects. Comparison with ground-based controls revealed no measurable differences.
Radiation dosimetry from the Mercury series established that minimal exposures were encountered at those orbital altitudes. A typical example is the MA-8 flight of W. M. Schirra, Jr., during which the body surface dosage was less than 30 millirads.
NASA has supported fundamental radiation studies at the Oak Ridge National Laboratory and the Lawrence Radiation Laboratory. Emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators.
At the NASA Ames Research Center extensive fundamental studies are being carried out on the effects of radiation, especially in the nervous system. It has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after X-irradiation. These deposits, referred to as a "chemical lesion," result from an accumulation of glycogen. The formation of these deposits during exposure to large doses of X-irradiation was not increased in environments of 99.5 percent oxygen and increased atmospheric pressure.