It began in a taxi going up Manhattan. My wife and I had gone over for a friend’s party, and were sharing the ride with another out-of-towner going to the event. After some gentle probing she – reluctantly – revealed that she was an astronaut. For some years I had been investigating movement in the absence of peripheral feedback with a man, Ian Waterman, who had no sense of touch and was unable to sense movement below the neck. I immediately started asking Marsha Ivins, the astronaut, whether, without the normal force of gravity, it was harder to sense the position of joints in space. She thought it was and, in fact, we have provided some evidence of this.

I wondered how Ian might manage under ‘zero g’, since with no peripheral feedback and his altered limb inertia we would be able to look at his ability to control his movements in a new way. To my surprise Ian was, if anything, even more enthusiastic to find out than I was.

Some of the best work on the neurophysiology of movement in altered gravity has been done by Professor Jim Lackner and his group at the Ashton Graybiel Spatial Orientation Lab at Brandeis University near Boston. Jim was as keen to fly Ian as I was. A Wellcome travel grant covered our travelling costs and Jim’s grant covered the rest, so last summer Ian and I went out for a week’s ground-based experiments at Brandeis before flying onto Houston for a further week. Jim’s lab is a wonderful underground treasure trove, with a startling variety of imaginative ways to induce sickness in experimental subjects. They produce hyper-gravity in a huge rotating room mounted on the bearing from an old German battleship’s gun turret. We did four experiments in Brandeis, then loaded the equipment into a van and set off on the 1800 miles to Houston.

For three decades or so, NASA has been training astronauts for weightlessness in its famous KC135 plane, a modified Boeing 707 nicknamed the ‘Vomit Comet’. It describes a parabolic flight trajectory between 23 000 and 32 000 ft. As it goes over the top, passengers experience 25 seconds of weightlessness followed by nearly double that time at 1.8g. Each two-hour flight includes 40 parabolas, every one an invitation to empty one’s stomach contents into the ‘barf bags’ NASA has the foresight to provide.

Before our flights we are ushered into a hut for a short but rather scary training video about what to do if the plane decompresses. We are also informed casually that the KC135 is not a scheduled IATA flight and that our insurance is invalid. Fortunately, I had anticipated that one and arranged some through a friend at Lloyds.

Once airborne we all went to our positions, four experimental subjects and four researchers. We carried out two experiments on reaching, one on knee bends and one on estimating the length of a rod held in an outstretched and unseen hand. The aim of the experiments was to test movement trajectories and accuracy during 0g and 2g and during the rapid transitions between the two.

As the plane went over the top the first time, and we entered 0g, it was like the biggest humpback bridge you could imagine. My guts came into my throat...and stayed there. Things settled a little and I left my arm outstretched and amazingly it stayed there effortlessly. I looked down at the table to make a reaching movement and, despite knowing what would happen, I could not prevent my arm going high and too far. I looked at the others further down the plane and realised that they now appeared upside down, on the ceiling. More than that, I felt upside down as well, a common inversion illusion in 0g. Then the plane shuddered a bit, the 25 seconds were up and 1.8g was upon us. I felt extraordinarily heavy; my reaching movements were short and straight into the table.

Initially I was very wary of the transitions, and nervous of vomiting. But as I relaxed the nausea faded and I began to enjoy weightlessness, a feeling of great serenity and relaxation. Two hours later we touched down having carried out four complex experiments: no mean feat. Ian had been sick and his discomfort was not helped by my own insufferable smugness at not barfing. The NASA photographer was disappointed, for Marsha had wanted a photo of me vomiting she could download onto the net for my family to see. But the photographer did ask me to stand in front of the plane. I put on my shades and my best ‘Top Gun’ pose. Physiology, I thought, can be fun.

Acknowledgements: Jonathan Cole acknowledges the Wellcome Trust for the travel grant, and Professors Jim Lackner and Paul DiZio for their local support. Jonathan Cole is in the Department of Clinical Neurological Sciences, University of Southampton and Poole Hospital.

External links

• NASA