Taking gravity into space.
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Aerospace Medicine↗
Biomedical subjects
L J Meeker
Publications and source records attributed to L J Meeker.
A human-powered, small radius centrifuge for space application: a design study.
The necessity of preventing physiologic deconditioning of astronauts exposed to long duration space flights is well known. A method under consideration to prevent this deconditioning is the use of periodic exposure to artificial gravity which could be provided by a centrifuge. This paper presents a design study for a human-powered centrifuge which could be used aboard the NASA Space Shuttle with analyses which quantify many of the forces produced. Consideration is given to managing reaction forces to changes in centrifuge angular velocity, centrifuge imbalance effects, the effects of gyroscopic moment on spacecraft orientation changes, and torque and power requirements as a function of centrifuge performance parameters. A design concept for a "human powered" centrifuge which could provide both exercise and artificial gravity exposure is also considered.
Acceleration↗
Physiologic validation of a short-arm centrifuge for space application.
A short-arm centrifuge (SAC) of 5-6 ft (1.5-1.8 m) radius may be useful in space to measure tolerances to acceleration (G) and to stimulate the cardiovascular system, thereby reducing cardiovascular decompensation that occurs in weightlessness. Relaxed rapid (1G/s onset rate, ROR) and gradual (0.1 G/s onset rate, GOR) G tolerances were measured on seven men using a 5-ft (1.5 m) radius centrifuge and compared with their G tolerances obtained on the 20-ft (6.1 m) radius human-use centrifuge at the Armstrong Laboratory, Brooks AFB, TX. Since the subjects were required to flex their legs to assume a squatting position on the SAC, a similar position was used on the 20 ft (6.1 m) centrifuge called feet up (FU), and compared with normal-seated +Gz tolerances (controls). The subjects tolerated the SAC exposures without any problems. ROR and GOR tolerances were as follows: control, 3.6 G and 4.2 G; FU, 4.5 G and 5.6 G; and SAC, 4.6 G and 6.4 G. We concluded that a 5-ft radius centrifuge can be used to measure G tolerances. The increases in the SAC GOR tolerances over ROR tolerances indicate that the baroreceptors were stimulated by the G, and the SAC exposure would be useful in preventing cardiovascular decompensation in microgravity.
Adult↗
Unpredictability of fighter pilot G tolerance using anthropometric and physiologic variables.
Correlation and regression analyses were used to study relationships between centrifuge G tolerances of 1,434 fighter pilots during High-G Training (HGT) and anthropometric and physiologic variables. Multiple regression analyses yielded a four-variable model in which gradual onset run (GOR) relaxed-G tolerance was inversely correlated with height and directly correlated with age, weight, and diastolic blood pressure. Although the four-variable model was able to predict more of the variation in G tolerance than any single variable, neither method showed a correlation (r) of greater than 0.35 with GOR relaxed or straining G tolerance. No subject variable was significantly different between the pilot groups that did and did not experience G-induced loss of consciousness. We conclude that prediction of G tolerance during centrifuge HGT is unreliable using anthropometric and physiologic variables. The anti-G straining maneuver remains the major determinant of an individual's G tolerance.
Adult↗