Space is no place for Pac-Man
Until space engineers learn to protect today's densely packaged, ultra-miniaturized electronic equipment from cosmic rays, Pac-Man won't make it as an astronaut. What's more important, scientists won't make full use of the sophisticated new instruments that are becoming available for earth satellites, either. According to physicist Peter J. McNulty, cosmic-ray danger has put a damper on satellite-instrumentation design.
McNulty, a professor at Clarkson College of Technology, has outlined the problem in Physics Today.
The only way to avoid cosmic-ray upsets now, he says, is ''by severely restricting the types of devices flown and, thereby, limiting the speed and memory capacity of the experiment. Considerable work, including the development of error-correction techniques, must be carried out before sophisticated integrated circuits like those used routinely in such arcade games as Pac-Man . . . can be trusted to function reliably in space.''
Cosmic rays cause two kinds of damage. ''Hard errors'' permanently change equipment, and may even burn out a circuit. ''Soft errors'' change computer memory without equipment damage, turn things on or off, and otherwise create data mayhem. McNulty notes that this kind of mischief has already hit a number of US satellites, since they're orbiting above the ionosphere, which shields Earth from damaging cosmic rays.
Engineers have only begun to grapple with the problem. McNulty says their efforts are hindered by lack of awareness of the cosmic-ray threat and by industrial secrecy. Exposing electronic devices in particle accelerators can simulate cosmic-ray damage. But to use such data to predict damage in space, engineers need the kind of detailed knowledge of a device's structure that manufacturers consider proprietary information.
''With the present state of affairs, system designers are understandably reluctant to incorporate newer and more sophisticated RAMs (random-access computer memories) and microprocessors without previous flight experience,'' McNulty says.
He explains that one of the biggest needs is for algorithms (mathematical procedures) for using test data obtained on the ground to predict cosmic-ray error rates in space. The US Air Force and NASA are planning a project to develop such algorithms and test them in orbit. It's called CRRES, the Chemical Release and Radiation Effects Satellite.
The CRRES test flight, probably in 1986, will be preceded by extensive ground-based testing and simulation. Once in space, the satellite will sample effects near Earth within the Van Allen radiation belts. Here the main danger is from protons and electrons. Then the satellite will carry the test equipment deeper into space, where cosmic rays are the main threat. Meanwhile, Pac-Man had better stay inside the arcade. Plants with memories
Like animals, at least one plant may have memories. It stores learned information and later acts on it, according to experiments at the University of Clermont, France, carried out by Marie Desbiez and co-workers.
They used the Bur-Marigold (Bidens pilosus)m plant. A fine needle was used to puncture leaflets so as to disrupt the plant's natural symmetry. This was done when young plants were at a symmetrical stage of growth. Both the punctured and untreated leaflets were removed. This ensured that the results would involve memorization and not be a response to the wounding. Subsequent new growth then ''remembered'' the asymmetry and continued to grow in that pattern.
Through these and other experiments, the French botanists recorded what they consider evidence of both short-term and long-term memory in this plant species. According to a New Scientist report, the experiments suggest memory ability even though the plant has no nervous system as such. This suggests basic mechanisms for memory and information transmission at the cell level may be widespread in earthly organisms.