最隐蔽的方式

The atmospheric pressure as we climb is getting so low that without any air supply, I'd be unconscious within 20 seconds.

I have to breathe 100% oxygen to avoid getting nitrogen bubbles in my bloodstream, which could be fatal. Last time I was up at 30,000 feet was on the summit of Everest.

Jumping at this altitude is a technique used by special forces for covert insertions. Mimicking the flight path of commercial jets is an effective concealment and deploys troops fast without detection.

It's known as high-altitude-low-opening, or HALO. I've got t-minus two. Two minutes to jump.

The temperature has plummeted to minus-40. Exit the plane without my goggles, and my eyes would freeze instantly.

Down on the desert floor, it's over 100. I'm about to put myself through a temperature change of 140 degrees in less than 5 minutes.

I'm wired up so that my team can measure my body stats on my descent. Okay, let's go. In six seconds, I hit terminal velocity.

It's impossible to fall any faster. And because the air is thinner at this altitude,

I'm falling at just under 200 miles an hour. We're in HALO free fall! Just amazing. Okay, altitude check.26,000 feet and falling fast.