Shepardsport Pirate Radio

It’s easy to think of the Sun as something eternal, unchanging. And from a perspective at the bottom of Earth’s protective blanket of atmosphere, the day star does appear as an unchanging disk of light moving across the sky from east to west. Yes, from time to time it appears to be devoured and regurgitated by some unseen entity, resulting in darkness in daytime, but as humans began to observe the movements of the other celestial bodies in the sky, they began to realize that it was in fact the Moon moving before the Sun and casting a shadow. As a result, it became possible to predict eclipses and avoid the panic that had previously accompanied these events.

It was only when Galileo trained a telescope upon the Sun that it was discovered that, far from being a perfect disk of light, it is in fact marred by dark patches, which we call sunspots. Over time, it was discovered that these sunspots follow regular patterns, and by the beginning of the Space Age, it was understood that these markings are magnetic storms caused by kinks in the Sun’s magnetic field, and they appear dark only in comparison to the rest of the solar disk.

It was also the Space Age that made sunspots and their effects in the solar neighborhood of more than abstract scientific interest. Even before the development of modern radio astronomy, there was an awareness that sunspots had effects on the operation of telegraphs, as witnessed the famous Carrington Event. Even more markedly, radio transmissions were affected by changes in the charge states of the upper atmosphere both as a result of the Earth’s diurnal cycle and the Sun’s much longer sunspot cycles.

But as human activity began to move beyond the Earth’s atmosphere, it became increasingly necessary to take solar activity into account. Even the relatively primitive satellites of those first years could be affected by space weather, and the more sophisticated microminiaturized components only became ever more vulnerable unless they were specifically hardened against system-generated electromagnetic pulse from charged particles in the solar wind.

In retrospect, the first decade of human spaceflight was incredibly lucky. That was a period of relatively low solar activity, often called the Years of the Quiet Sun. It helped that those early flights, particularly those which went beyond Earth’s protective magnetosphere, were of relatively short duration, which reduced the odds that crews would be exposed to elevated radiation.

All that changed with Zond 12, which was returning from an aborted attempt at a lunar landing when a major solar flare occurred. The thin-walled Soyuz spacecraft was little protection against the charged particles streaming toward the Earth-Moon system, and while the cosmonauts were able to reduce their radiation exposure somewhat by reorienting their spacecraft to put the service module between themselves and the Sun, it may well have only delayed the inevitable. Instead of dying immediately of life-support failure or radiation sickness, the cosmonauts survived to die some years later of leukemia and other cancers.

Although the Soviet space program sought to keep this disaster under wraps, enough information leaked out that NASA undertook a major redesign of the Manned Venus Flyby spacecraft to ensure that the astronauts would be protected against all but the most severe of solar storms. In the following years, as long-duration lunar missions developed into permanent moonbases, radiation shielding was always a consideration. While the Apollo Lunar Module might be adequate for a two or three day stay on the lunar surface, stays stretching into weeks or even months should have some form of shelter, even if it was nothing more than a space large enough for the astronauts to sit, covered by a protective blanket of lunar regolith.

With the development of actual settlements on the Moon, it became customary to bury all structures under a layer of regolith. With an expanded presence on the Moon, it became possible to use more extensive excavating equipment and to actually build within mountain ranges and the rim walls of craters, as well as inside lava tubes and other types of natural lunar caverns.

But even with this natural protection, it is necessary to remain continually aware of space weather and the hazards it poses to both humans and machines. Even with the extensive use of robotics, it is still necessary for human beings to suit up and make EVA’s on the lunar surface to do things robots cannot. And travel between settlements invariably involve a measure of exposure to potential radiation hazard. As a result, we keep a careful watch over the activity of the Sun, and issue watches and warnings as necessary, much as terrestrial weather forecasters issue tornado and severe storm watches and warnings.

Even within the largest of settlements, we have shelters to provide a measure of safety against the strongest of solar storms. With adequate warning, we can suspend operations that expose personnel to unnecessary hazards, and if necessary, withdraw into these areas deep under the water reservoirs which provide additional shielding.

—- Ursula Doorne, PhD, Leland Professor of Astronomy, Kennedy University Tycho, notes for an article on solar weather in the Space Age.