Commercial spaceflight participant G-force tolerance during centrifuge-simulated suborbital flight

Introduction: Medical knowledge of the human body in microgravity and hypergravity is based upon studies of healthy individuals well-conditioned for such environments. Little data exist regarding the effects of spaceflight on untrained commercial passengers. We examined the responses of potential spaceflight participants (SFP) to centrifuge G-force exposure. Methods: There were 77 individuals (65 men, 12 women), 22-88 yr old, who underwent 6 centrifuge runs over 48 h. Day 1 consisted of two +G_z runs (peak = 3.5 +G _z, run 2) and two +G_x runs (peak = 6.0 +G_x, run 4). Day 2 consisted of two runs approximating a suborbital spaceflight profile. Data included blood pressure, electrocardiogram, and postrun questionnaires regarding motion sickness, disorientation, greyout, and other symptoms. Results: Of the 77 participants, average age was 50.4 ± 12.7 yr. Average heart rate (HR) varied by sex and direction of G-exposure ( +G_z: F 150 ± 19, M 123 27; +G_x: F 135 ± 30, M 110 ± 27). Age and peak HR were inversely related (HR, 120bpm: 60.2 ± 12.2 yr, HR. 120: 47.1 ± 10.9 yr). HR during peak G-exposure for the final run was associated with post-run imbalance (no imbalance: HR 126 ± 26, imbalance: HR 145 ± 21); no other significant hemodynamic change, sex, or age variation was associated with imbalance. Age and greyout were inversely associated; there was no association between greyout and vital sign change, sex, or G-force magnitude. Baseline/pretrial mean arterial pressure (MAP) was not associated with any symptoms. Discussion: The results suggest that most individuals with well-controlled medical conditions can withstand acceleration forces involved in launch/landing profiles of commercial spaceflight vehicles. Further investigation will help refine which conditions present significant risk during suborbital flight and beyond.