Comparison of operating conditions for U-2 aircraft, ISS EVA, and proposed exploration EVA_
| U-2 Aircraft | ISS EVA | Exploration EVA | |
|---|---|---|---|
| Baseline pressure | 14.7 psia | 14.7 psia19 | 8.2 psia24 |
| Operating Pressure | Before CARE: 4.4 psia | 4.3 psia / 5.8 psia19 | 4.3 psia25 |
| After CARE: 8.4 psia | |||
| Pressure delta | Before CARE: 10.3 psia | 10.4 psia | 3.9 psia |
| After CARE: 6.3 psia | |||
| Pre-breathe | 100% O2 for one hour15 | Various | 100% O2 for 15 mins25 |
| Operating FiO2 | 100% O216 | 100% O219 | 100% O225 |
| Gravity | Minimal | 0 G | Moon: 0.16 G |
| Lower limb movement | Minimal | Minimal | Significant |
| Exposure frequency | Frequent, no more often than every third day10 | Up to four times per year, usually weeks/months apart20 | Frequent, upto multiple times per day |
| Exposure duration | Up to 9 hours10 | 4-8 hours20 | 4-8 hours with intermittent recompression26 |