Engineering topics

Krutz, R. W., Jr.

Publications and source records attributed to Krutz, R. W., Jr..

5 records

NASA NTRS1994

Comparative performance of a modified Space Shuttle Reentry Anti-G Suit (REAGS) with and without pressure socks

In a prior study, the Armstrong Laboratory (AL) demonstrated that +G(sub z) protection during simulated shuttle reentry could be improved with an extended coverage anti-G suit with pressure socks but no abdominal bladder (REAGS). In a subsequent study conducted at the NASA Johnson Space Center it was shown that REAGS had a down side which included restricted mobility (during simulated shuttle egress) and a larger boot size needed for the pressure socks. The present study was conducted using a modified REAGS to increase mobility during egress. The size of the crotch opening was increased, and the fabric covering the buttocks was replaced with more elastic material. Six healthy male members of the AL centrifuge panel served as subjects for the study. As in the earlier study, subjects received 20 to 35 mg of IV Lasix approximately 6 hours before being exposed to a simulated space shuttle reentry +G(sub z) profile on the AL centrifuge, which induced a mean weight loss of 2.8 percent, range 2.1 percent to 3.7 percent. The REAGS was inflated to 1.0 psig 10 minutes prior to G onset. The G-profile was identical to that used in the previous REAGS study. Physiologic parameters monitored were also the same, i.e., eye-level systolic blood pressure (ELBP) using the Finapres digital cuff technique and heart rate and rhythm. Subjective comments were obtained from questionnaires administered after the increased G exposure. Systolic ELBP was maintained at 60 mm Hg or above by pressurizing the anti-G suit in 0.5 psig increments up to a maximum pressure of 2.5 psig. There were no significant differences in mean G-suit pressure required to maintain systolic ELBP at 60 mm Hg or above between the REAGS worn with and without pressure socks. Maximum mean G-levels achieved during the GOR were also the same under both experimental conditions, i.e., 4.7 G with socks and 4.6 G without socks. These G-levels were essentially the same as recorded earlier with the unmodified REAGS. There were no significant differences in comfort rating during the G exposure assigned by subjects when they wore the modified REAGS with or without the pressure socks.

Krutz, R. W., Jr.↗

NASA NTRS1992

An evaluation of three anti-G suit concepts for shuttle reentry

A study was conducted to compare the standard anti-G launch-entry suit (LES) with a reentry full-coverage anti-G suit (REAGS) and a REAGS without an abdominal bladder (AB). (The inflated AB is the most uncomfortable G-suit component). Intravenous Lasix, a diuretic, was used to induce the fluid loss seen during space flight. Using the Armstrong Laboratory Centrifuge, data collected from seven subjects have shown that less anti-G suit pressure is required to maintain eye-level systolic blood pressure above 70 mmHg when the REAGS or REAGS without AB is worn during simulated shuttle reentry G-profiles when compared to the current LES G-suit. The REAGS without AB was significantly more comfortable than the standard anti-G suit.

Krutz, R. W., Jr.↗

NASA NTRS1989

Determining a bends-preventing pressure for a space suit

Research conducted to determine the proper pressure for preventing bends during EVA without preoxygenation is examined. Male and female subjects with different breathing gas mixtures and pressures are studied in order to define the pressure. Visual and auditory Doppler ultrasonic signals are utilized to monitor intravascular gas bubbles. The workload, which simulates EVA, consists of a handturned bicycle ergometer, a torque wrench operation, and a rope pull. The experimental data reveal that the minimum space suit pressure needed to prevent decompression sickness is 9.5 psi.

Krutz, R. W., Jr.↗

NASA NTRS1985

Minimum pressure for a zero-prebreathe pressure suit

There are two current approaches to reducing the risk of decompression sickness during repeated extravehicular activity (EVA) without prebreathing 100 percent oxygen. One approach suggests the use of different pressures in the transfer vehicle, the station, and the suit. The other would use advanced pressure-suit technology to build a suit that will make different pressures unnecessary provided the bends-free suit pressure is reasonable and can be readily determined. Research at the USAF School of Aerospace Medicine since November 1982 has been directed at determining this suit pressure using human subjects at simulated altitudes of 16,500 to 10,000 feet (7.8 to 10 psia). An earlier report of this ongoing research showed that bends is not totally eliminated at 7.8 psia. The present study is a continuation of this effort to define a 'bends-free' suit pressure with the initial results suggesting that this pressure begins at around 9.5 psia (from a 14.7 psia station).

Krutz, R. W., Jr.↗

NASA NTRS1975

Comparison of techniques for measuring +Gz tolerance in man

Two objective methods and one subjective method for measuring +Gz tolerance (inertial vector in a head-to-foot direction) were compared on the human centrifuge. Direct eye-level blood pressure (Pa), blood flow velocity in the superficial temporal artery (Qta), and subjective visual symptoms were used to determine tolerance to rapid-onset acceleration (1 G/s) on the USAFSAM human centrifuge. Seven 'relaxed' subjects with extensive centrifuge experience were exposed to gradually increasing +Gz plateaus until the subject reported 100% loss of peripheral centrifuge gondola lights (PLL) and 50% loss of central light (CLD); viz., blackout. Zero forward Qta occurred 6 s (range 4-9 s) before subjective blackout and when mean eye-level blood pressure had reached 20 + or - 1 mm Hg (SE). The results of this study indicate that flow changes in the superficial temporal artery reflect flow changes in the retinal circulation during +Gz stress.

Krutz, R. W., Jr.↗