Sir

The News item on NASA's Bion programme of flying restrained and heavily instrumented rhesus macaques into space portrayed it in a light that the programme does not deserve (Nature 387, 4; 1997). In fact, Bion's design is such that meaningful results about “how musculoskeletal and regulatory mechanisms respond to and recover from space flight” (Bion 11/12 Integrated Science Proposal and Discipline Proposals, 1996) are virtually precluded.

Both restraint and microgravity result in osteopenia and disuse atrophy of muscles, which makes it impossible to determine the specific impact of microgravity (or any other cosmic factor) on bones and muscles in the restrained animals sent into space.

The ‘regulatory physiology’ protocol contains no hypotheses, which, in conjunction with the interference from restraint and psychological stress, the sample size of two, and dramatic individual differences in response (as documented by previous missions), reduces Bion to ‘parametric tinkering’, generating a spiral of inconclusive animal studies that are only vaguely, if at all, applicable to free-moving, relatively comfortable astronauts.

To be most useful for future missions, experimental data of this nature should be obtained from humans. The head-down tilt bed rest model simulates the physiological effects of microgravity and accurate non-invasive techniques, and osteoblast cultures are now available to study the cellular and biochemical mechanisms of osteopenia. All the musculoskeletal tests and eight out of nine ‘regulatory physiology’ tests could have been done in consenting humans. Eight measurements taken from astronauts are far more valuable than nine from strait-jacketed monkeys in pain and distress.

We believe that sending animals into space is one of the most ineffective ways of studying the effects of microgravity on astronauts, and that subjecting conscious mammals to extreme trauma in the name of technological progress is unethical.

Bion involved some of the most invasive instrumentation ever imposed on a conscious primate. In addition to extensive wiring of the body and 10 incisions (including a perforation of abdominal muscles), each of the two flight and 10 control macaques had 11 holes (eight for Evarts crown, three for epidural cannulae) drilled in the skull roof and two depressions and canals in the zygomatic bones for an electro-oculogram. As well as the pain and terror of being strait-jacketed in these circumstances, the flight animals were exposed to motion sickness and shock from the dramatic concomitance of launch and landing. After returning to Earth, one macaque choked to death under anaesthesia.