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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Advanced thrust chamber designs

A regeneratively cooled thrust chamber has been designed and fabricated, consisting of an inner TD nickel liner which was spin formed, welded, and machined and an outer shell of electroformed nickel. Coolant channels were produced in the outer surface of the inner liner by the electric discharge machining process before electroforming the shell. Accessory manifolds and piping were attached by welding. Manufacturing processes employed are described.

Dietrich, F. J.↗
NASA NTRS1971

Fabrication methods for TD nickel.

Spin-forming, welding, machining, electric discharge machining, and electroforming operations in th e construction of a TD Nickel rocket thrust chamber are described. TD Nickel was one of the first commercially available dispersion hardened alloys. Dispersion hardened alloys are being given prominent consideration in the construction of the space shuttle; therefore, fabrication experience gained with the TD Nickel material is of current interest.

Leach, A. E.↗
NASA NTRS1971

Biochemical and physiological consequences of the Apollo flight diet.

Six male subjects subsisting on a typical Apollo flight diet for five consecutive days were evaluated for changes in biochemical and physiological status. Laboratory examinations failed to demonstrate any significant changes of the kind previously attributed to weightlessness, such as in serum electrolytes, endocrine values, body fluid, or hematologic parameters.

Hander, E. W.↗
NASA NTRS1971

A generalized method of active RC network synthesis.

A completely general active RC network synthesis technique using a grounded gyrator and a summing amplifier is described. The technique overcomes serious limitations of previous RC-gyrator realizations and offers advantages o ver other general active RC synthesis methods. The technique is well suited for construction using thin-film RC networks and integrated circuit operational amplifiers, and provides a configuration which is quite insensitive to element variations.

Leach, D. P.↗
NASA NTRS1972

Effects of bedrest and centrifugation of humans on serum thyroid function tests.

Changes in plasma volume and protein concentration have been reported when normal subjects are bedrested or centrifuged. Since thyroid hormones are transported by specific plasma proteins, each of these procedures could be expected to change plasma levels of these hormones. In this study centrifugation of normal healthy human subjects produced an increased concentration of total protein and albumin. When these same subjects were bedrested for six days, no change in total protein, albumin or thyroxine binding globulin were found although there was an eight per cent decrease in plasma volume. Centrifugation and, to a lesser extent, bedrest produced changes in serum T-4 levels and the T-3 test results. The direction of these changes (decreased % T-3 values and increased T-4 levels) indicate that these two situations produce an increased plasma concentration of thyroxine binding sites.

Leach, C. S.↗
NASA NTRS1972

Endocrine Laboratory Results Apollo Missions 14 and 15

Endocrine/metabolic responses to space flight have been measured on the crewmen of Apollo missions 14 and 15. There were significant biochemical changes in the crewmen of both missions immediately postflight. However, the Apollo 15 mission results differed from Apollo 14 and preflight shown by a normal to increased urine volume with slight increases in antidiuretic hormone. Although Apollo 15 was the first mission in which the exchangeable potassium measurement was made (a decrease), results from other missions were indicative of similar conclusions.

Leach, C. S.↗
NASA NTRS1972

Circadian rhythm asynchrony in man during hypokinesis.

Posture and exercise were investigated as synchronizers of certain physiologic rhythms in eight healthy male subjects in a defined environment. Four subjects exercised during bed rest. Body temperature (BT), heart rate, plasma thyroid hormone, and plasma steroid data were obtained from the subjects for a 6-day ambulatory equilibration period before bed rest, 56 days of bed rest, and a 10-day recovery period after bed rest. The results indicate that the mechanism regulating the circadian rhythmicity of the cardiovascular system is rigorously controlled and independent of the endocrine system, while the BT rhythm is more closely aligned to the endocrine system.

Winget, C. M.↗
NASA NTRS1972

Thyroid and adrenal cortical rhythmicity during bed rest.

The effects of prolonged bed rest on adrenocortical and thyroid function were assessed in eight healthy males, aged 20-40 years, who were submitted to bed rest for 56 days on a 14L:10D regimen (lights-on, 9:00 AM). Four of these subjects exercised three times daily throughout the experiment. Circulating cortisol, triiodothyronine, and thyroxine, concentrations were determined in blood samples drawn at four hourly intervals for 48-hr periods before, 10, 20, 30, 42, and 54 days during, and 10 days post-bed rest. Significant fluctuations in the circulating levels of all three hormones occurred with peaks at 7:30 AM. The suggestion is advanced that thyroid rhythms may be posture dependent.

Vernikos-Danellis, J.↗
NASA NTRS1973

Bioassay of body fluids, experiment M073

Body fluids were assayed in this experiment to demonstrate changes which might have occurred during the 56-day chamber study in fluid and electrolyte balance, in regulation of calcium metabolism, in overall physiological and emotional adaptation to the environment, and in regulation of metabolic processes.

Leach, C. S.↗
NASA NTRS1974

Circadian, endocrine, and metabolic effects of prolonged bedrest: Two 56-day bedrest studies

Two bedrest studies of 56 days each have been conducted to evaluate the effects of prolonged bedrest on circadian synchrony and endocrine and metabolic function. Measurements included the pituitary-adrenal, thyroid, parathyroid, insulin-glucose-growth hormones, catecholamine excretion, body temperature, and heart rate. The results indicated that a rigorous regimen of exercise did not prevent the endocrine and metabolic effects of prolonged bedrest. Changes in circadian, endocrine, and metabolic functions in bedrest appear to be due to changes in hydrostatic pressure and lack of postural cues rather than to inactivity, confinement, or the bleeding schedule. Prolonged bedrest, particularly beyond 24 days, resulted in rhythm desynchronization in spite of well regulated light/dark cycles, temperature, humidity, activity, and meal times and meal composition and in increased lability of all endocrine parameter measured. It also resulted in an apparent insensitivity of the glucose response to insulin, of cortisol secretion to ACTH, and of growth hormone secretion to hypoglycemia.

Vernikos-Danellis, J.↗
NASA NTRS1973

Estimates of fluid and energy balances of Apollo 17

Fluid and caloric balance has been calculated for the Apollo 17 crew. This included measurement of nitrogen, water, and caloric value of the ingested food and the volume and nitrogen content of the excreted urine and feces. Body composition changes were determined from total body water and extracellular fluid volume differences. The body composition measurements made it possible to divide the weight loss into lean body mass and adipose tissue losses. From this division a caloric equivalent was calculated. These tissue losses indicated that the caloric requirements of the mission were considerably greater than the actual caloric intake. The 3.3 kilo mean loss of body weight represented 1 kilo of lean body mass and 2.3 kilos of adipose tissue. Calculated fluid balance was more positive during the mission than during the control period. These changes are unlike the body composition and fluid balance changes reported in bedrested subjects.

Johnson, P. C.↗
NASA NTRS1973

The effect of bedrest on adrenal function

Eight male subjects were subjected to continuous bedrest for 24-80 weeks for the purpose of studying metabolic responses. Three of the subjects did supine exercises daily during part of the study. Adrenal function was examined in relation to adrenal cortical and medullary excretions. The results reveal an increase in hydrocortisone throughout the test period, a decrease in norepinephrine and no change in epinephrine. These data suggest that exercise could decrease the severity of deconditioning caused by bedrest.

Leach, C. S.↗
NASA NTRS1974

Adrenocortical responses of the Apollo 17 crew members

Changes in adrenal activity of the three Apollo 17 crew members were studied during the 12.55-day mission and during selected post-recovery days. Aldosterone excretion was normal early and elevated later in the mission, probably causing a loss in total body exchangeable potassium. There was decreased 17-hydroxycorticosteroid excretion only during the early mission days for the two moon landers and throughout the mission for the other astronaut. Cortisol excretion was elevated on physically stressful mission days. At recovery, plasma ACTH was elevated without a similar increase in plasma cortisol. Angiotensin I activity was elevated at recovery in only one crewman. This crewman was the only one with a decreased extracellular fluid volume. These results indicate that the mission and its activities affect adrenal function of the crewmen.

Leach, C. S.↗
NASA NTRS1974

Hydrocortisone and ACTH levels in manned spaceflight

The plasma hydrocortisone, plasma ACTH, and urinary hydrocortisone values were recorded for each man of the crews of Apollo flights eight through fifteen, 30, 14, and 5 days before flight, immediately after spaceflight recovery, and on future days until the return of most variables to preflight values. The plasma and urinary preflight hydrocortisone values were significantly higher than the postflight values. This result is discussed in terms of three possible explanations: (1) the adrenal-cortical function is suppressed during spaceflight; (2) the activity in flight may amount to stressful exercise, which tests have shown can cause a decrease in plasma adrenocortical hormones; and (3) the in-flight work-rest cycles may be such as to affect the circadian periodicity of the pituitary-adrenal function.

Leach, C. S.↗