I’ve touched upon the subject of science fiction becoming science fact once or twice in this column. One wonders whether human imagination is boundless or whether human ingenuity will ultimately see even the wildest imaginings becoming commonplace at some distant point in time. Such thoughts crossed my mind last week when I spotted an irresistible, not to say, compelling piece of science fact from the pages of a learned journal.
A team of international researchers lead by the Rutherford Appleton Laboratory’s plasma specialist, Ruth Bamford, has demonstrated that an artificially induced ‘force field’ - the invisible barrier that protected the Star Ship Enterprise from all manner of unwanted intrusions in the hit TV and film science fiction drama, Star Trek - may one day be achievable.
According to a recent paper, published by the Institute of Physics’ Plasma Physics and Controlled Fusion journal, and currently available for reading on the Science and Technology Facilities Council’s ‘Mini-Magnetosphere’ website, the team showed that it may be possible for astronauts to shield their spacecrafts with a portable magnetosphere, scattering the highly charged, ionised particles of the solar wind and flares away from their space craft. This recent work was based on 50 years worth of knowledge gleaned from research into the containment of nuclear fusion.
The international space agencies, which are seriously considering robotic and even manned missions to Mars, cite ‘space weather’ as the single greatest obstacle to deep space travel. Radiation from the sun and cosmic rays pose a deadly threat to astronauts in space. The solar energetic particles (mostly protons), while making up just part of the ‘cosmic rays’ spectrum, are of greatest concern because they are the most likely cause of radiation damage. Large numbers of these energetic particles occur intermittently as ‘storms’, against which the Earth – and in particular, its biosphere - is protected by its own natural force field, the magnetosphere (a magnetised plasma structure created as a consequence of the Earth’s magnetic dipole field as it extends out into space).
The Apollo astronauts of the 1960s and 1970s are the only humans to have travelled beyond the Earth’s magnetosphere. With journeys to the moon lasting only about eight days it was possible to miss an encounter with such a storm; a journey to Mars, however, would take about eighteen months, during which time it is almost certain that astronauts would encounter a solar storm and run the real risk of exposure to ionising radiation. Interestingly, if you study a record of solar activity over the period of the Apollo programme, the mission timing (coinciding with relatively low levels of activity) proved exceedingly fortuitous for the crews!
On the International Space Station there is a special thick-walled room to which the astronauts retreat during times of increased solar radiation. However, on longer missions, astronauts cannot live within shielded rooms, since such shielding would add significantly to the mass of the spacecraft, and hence the cost and complexity of its launch. It is also now known that the ‘drip-drip’ of even low levels of radiation can be as dangerous as a large, acute dose arising from a solar storm. But the Rutherford Appleton laboratory experiments show that it may be possible to reduce the threat to tolerable levels, making a manned mission to Mars more likely.
Space craft visiting the Moon or Mars could maintain some of this protection by taking along their own portable ‘mini’-magnetosphere. The idea has been around since the 1960s but it was thought impractical because it was believed that only a very large (in excess of 100km diameter) ‘magnetic bubble’ could possibly work, and vastly large power supplies and coil assemblies would have been required to achieve the necessary field strengths. But what this early work neglected to take into account were the plasma effects that are likely to dominate under such conditions.
Using 3D computer simulations of plasma-dipole field interactions, one of the team members has demonstrated that more modest field strengths may be effective at creating diamagnetic-like cavities (regions in which energetic ionised particles are essentially absent), offering the potential for spacecraft shielding. The work showed that, theoretically at least, a very much smaller magnetic bubble of only several hundred meters across would be enough to protect a spacecraft.
Last week, the Rutherford Appleton team confirmed these initial findings under laboratory conditions in the UK, on a rig measuring just 1.5m long.
So, what’s next? Teleportation? Now, I read somewhere that a group of Japanese physicists had claimed the possibility that matter.......but then, that’s another story, possibly for another day.
Beam me up Scotty!
Les Hunt
Editor