altitude of 50 miles. Twelve pilots (5 Air Force, 5 NASA, one Navy, and one contractor pilot) flew the X-15 aircraft during the more than nine-year flight program. (Fig. 4-17)

A total of 200 NASA technical reports and papers presenting information obtained during the flight program were published before the end of 1968, and four NASA-Industry technical conferences were held during the course of the program to present results to the technical community.

BIOTECHNOLOGY AND HUMAN RESEARCH

Human Research

Ames Research Center directed studies of ways to apply the fluorescent antibody technique for detecting microbial infections to the preclinical diagnosis of viral infections. The work underway will extend the technique to provide almost instantaneous detection of viral agents and rapid diagnosis of a variety of viral infections. It will be valuable in preflight examinations of astronauts preparing for space flights since it will enable doctors to detect

disease in the preclinical stage, minimizing the chance that the astronauts will suffer clinical illness in flight, as happened during the Apollo 7 flight and perhaps also during Apollo 8.

Ames was also developing toxicity criteria for gas environments in closed ecological systems. Studies indicated that prolonged breathing of pure oxygen causes a decrease in the circulatory red blood cell mass, even at the pressures now used in spacecraft, the collapse of alveolar air spaces (atelectasis), resulting in inadequate ventilation, and damage to the alveolar capillaries. Research was continuing to increase knowledge of the mechanism of oxygen toxicity.

The physiological and biochemical effects of candidate diluent gases for extended manned space flights were also being investigated. In long term exposure of rats and mice to helium-oxygen and nitrogen-oxygen mixtures, the only difference found was that in the helium-oxygen environment more food, water, and oxygen were consumed with no attendant increase in growth rate. The disparity is believed to be due to the differing thermal properties of nitrogen and helium.

The threat of incapacitating postural hypotension following prolonged weightlessness continued to cause concern. From studies of human volunteers subjected to two weeks of absolute bed rest (to simulate weightlessness), it was concluded that bed rest reduces bodily tolerance to standing erect, probably resulting from a decrease in plasma volume caused by extravascular dehydration. It is believed that some protection could be afforded astronauts by administering a drug (9-alphafluorohydrocortisone) which causes an increase in plasma volume, during the last 48 hours of a prolonged flight. A 30-week bed-rest study confirmed loss of body calcium and phosphorous; other findings included profound muscular weakness, pain in the feet on resumption of walking, decreased overall endurance, and psychological depression. On the basis of the findings in the shorter bed-rest study, it was determined that further work must be done on the possibility that decreased heart muscle strength and kidney stone formation can result from prolonged weightlessness.

Radiobiology research continued to concentrate on the effects of protons on specific parts of the body and on systemic effects resulting from whole body exposure. For example, exposure of the eye to radiation can result in opacity or cataract formation in the lens. Recent studies conducted for NASA at the Medical College of Virginia, examined the effects of fractionated proton irradiation

on the lens of rabbit eyes. At the doses where definite blood changes start to appear, between 25 and 50 rads, in both the acute and fractionate exposures, some lens damage was found but no loss of visual acuity.

Man-Systems Integration

Design, construction, and man rating were completed of ICARUS, a flying vehicle developed to evalaute the handling characteristics of a backpack flying device in lunar gravity. It is controlled by hand and arm manipulations which vary the magnitude and direction of thrust of two independent rocket motor assemblies pivoted to rotate in the fore-aft plane. Flight training was started, using an inclined plane lunar gravity simulation technique. (Fig. 4-18) ICARUS will be used to determine the effects on handling of various control systems and pressurized space suits; the use of the pilot's feet as landing gear with a burden of approximately 300 earth pounds (50 lunar pounds) will also be ested.

Life Support and Protective Systems

Techniques used to supply oxygen to spacecraft crews were un

der study for application to tactical military aircraft as a means of eliminating the need for liquid oxygen systems. An electrochemical technique which uses a water electrolysis module and a carbon dioxide concentrator to produce oxygen was being developed. (Fig. 4-19) The system package, which will operate on a small amount of aircraft power, will include a rebreather to conserve the oxygen normally discarded in open-loop breathing and provision for a pressure breathing mode in a depressurized cabin. Design goals call for the system to generate oxygen at a rate equal to approximately 1.5 times the 0.10 pounds/hour metabolically consumed by the crew, to have an operating time of 10 hours (plus a 25 percent reserve) and a 5-minute turn-around time (water refill), to weigh less than 50 pounds and have a volume of less than one cubic foot, and to require less than 700 watts of power. Tests of an engineering prototype indicated that the system will meet or exceed the requirements.

A matrix-type water vapor electrolysis cell capable of operating directly from humid cabin air was designed, and a unit producing about 1/4 a man's daily requirement was being evaluated. (Fig. 4-20) The device has several advantages: it can produce more than enough oxygen to fulfill a man's requirement (about 2 pounds

per day) and at the same time control humidity, the by-product hydrogen can be used for reducing carbon dioxide to generate additional water, and it is independent of gravity, eliminating the gas-liquid separation problem. Multi-man units were in the design stage.

The NASA Eighteenth Semiannual Report (p. 90) reported a joint NASA/Federal Water Pollution Control Administration project on removal of organic wastes from water by oxidation. The special catalyst required for the process was developed. It oxidizes the organics in the gas phase at temperatures below 200°F and one atmosphere of pressure, but it appears that pretreatment of the liquid effluent with the catalyst will make it possible to reduce the power and pressure requirements.

In another cooperative effort, this time with the federal Office of Saline Water, NASA investigated a technique for waste water purification which has space applications and may also help solve the problem of river pollution. In this technique, called reverse osmosis, water is forced through a membrane which removes impurities. The membrane must not rupture under the osmotic pressure of urine with its high concentrations of organic constituents. Such a membrane, consisting of porous glass hollow filaments, was developed and incorporated in a reverse osmosis water reclamation unit which will be evaluated in 1969 with both brackish water and human waste water. (Fig. 4-21)

Langley Research Center combined gas chromatograph and