Factors affecting human tolerance to sustained acceleration.

Area of Science:

• Aerospace Medicine
• Human Factors Engineering
• Physiology

Background:

• Understanding the effectiveness of anti-G suits (AGS) is crucial for protecting aircrew from high G-forces.
• Previous research suggests G protection from different techniques may be additive.
• The hydrostatic model of circulation is often used to predict physiological responses to acceleration.

Purpose of the Study:

• To investigate the relationship between anti-G suit (AGS) bladder inflation pressure and G tolerance in different body positions.
• To evaluate the impact of G onset time and AGS valve control on G tolerance and comfort.
• To test the additive nature of G protection techniques and the validity of the hydrostatic model.

Main Methods:

• Subjects were exposed to acceleration plateaus on a centrifuge in upright (15° SBA) and supine (60° SBA) positions.
• Anti-G suit (AGS) bladder inflation pressure was systematically increased.
• G onset time was varied, and a new servo-controlled anti-G valve was tested.

Main Results:

• A linear increase in G tolerance was observed with increasing AGS bladder inflation pressure in both upright and supine positions.
• Supine G tolerance decreased significantly with slower G onset times (2x and 4x increase).
• The servo-controlled anti-G valve's operational mode did not affect G tolerance or comfort; higher AGS pressures reduced comfort.

Conclusions:

• The findings support the hypothesis that G protection from simultaneously applied anti-G techniques is additive.
• The simple hydrostatic model adequately predicts the required AGS bladder pressure changes for G protection across different body positions.
• Optimizing AGS inflation pressure and understanding the effects of G onset are key for maintaining aircrew G tolerance and comfort.