A new study conducted by researchers shows that space radiation may provide a bigger danger than first predicted. According to Nathan Schwadron (Physics professor at the university of New Hampshire's Space and Science Center) "The Radiation dose rates from measurements obtained over the last 4 years exceeded trends from previous solar cycles by at least 30 percent, showing that the radiation environment is getting far more intense". Reseachers used NASA's Lunar Reconnaissance Orbiter (LRO), which has been circling the moon since 2009. specifically, they looked at dose rates of galactic cosmic rays Measured over the past for years by LRO's Cosmic ray telescope for the Effects of Radiation
Galactic cosmic rays or GCR's, are super energetic particles that are mostly protons and atomic nuclei. They have been accelerated to extremely high speeds by distant and dramatic events taking place in our galaxy. Supernova's for example, Can be very damaging to spacecraft electronics and with long term exposure can cause radiation sickness and can lead to cancer. Researchers now know that there is currently more radiation in deep space than there was during the Apollo Missions. The rise in galactic cosmic rays can be explained by the low solar activity over the past 11 year cycle. During active phases, the suns magnetic filed extends out word a great deal and deflects the galactic cosmic rays; which prevents the build up of deep space radiation. Currently there is only one way to protect astronauts from radiation in deep space, and that is to use passive radiation shielding.
Passive space radiation shielding consists of placing a physical material in between a person and the source of radiation. Its main advantage over other forms of radiation shielding is its ability to shield against any form of radiation, be it positively charged, negatively charged, or neutral, and it is widely-employed in Earth-based shielding applications, since weight is not an issue. on the other hand this is not really a good fit for space applications, because every kilogram of mass has a significant impact upon the mission cost and feasibility. Many spacecraft designers have proposed innovative designs that form large electromagnetic fields around a spacecraft, in order to mimic the protection of Earth's magnetosphere. This would be an example of active radiation shielding and there are many types being considered.
Electrostatic Shielding: This approach creates an electric field around an astronaut habitat, with the negative potential facing outwards to slow down negatively charged radiation. Engineering trade-offs to consider when designing such a system include the dielectric breakdown strength of the electrostatic material, the maximum voltage capabilities of the power supply, and the mechanical limits of the support structure in comparison to the internal coulomb forces generated by the charged components of the shield. Finally, there are no known major physiological issues associated with humans in large electrostatic fields, but further investigations are required in order to verify astronaut safety with a sufficient degree of certainty.
Magnetic Shielding. Magnetic shielding consists of forming a large magnetic field around the spacecraft, usually through the use of superconducting solenoids. Unlike with electric fields, there are known and suspected physiological effects of moving within a strong magnetic field. In order to use this approach for space radiation shielding, the design must allow for a habitable region without significant magnetic field strengths. Usually, this is done by using a torus-shaped design that has a shielded region internal to the torus. These layouts allow for a small region between the solenoids that is free of magnetic fields, while still generating a magnetic field that is comparable to an ideal dipole at large distances. Charged particles are either deflected by the magnetic field, or trapped along the magnetic field lines, well before they approach the internal shielded region of the torus.
Plasma Shielding. Plasma shielding is a field of ongoing research, fundamentally consisting of a mass of ionized particles that is entrapped by electromagnetic fields, swirling around a spacecraft enclosure and serving to deflect or ensnare charged particles. The protection is threefold: first, an electrostatic field with a positive potential repels positively charged radiation. Next, a magnetic field is added to ensnare the negatively charged particles that are drawn to the positive potential. Finally, these negatively charged particles would be drawn towards the positively charged surface, which could neutralize the surface; thus, a passive current-absorbing shield is placed at the magnetic poles, to absorb the negatively charged particles before they impact the positive surface. While the system is more complex, it leverages the strengths of passive, electrostatic, and magnetic shielding, and combines them into a highly effective solution.
Comparing the three types of active shields, electrostatic shields are relatively lightweight when compared to magnetic shields, but since they only repel negative particles, they also pull in positive particles, which creates a current influx that must be counteracted. Additionally, electrostatic shields are limited by voltage level, which in turn limits the energy level of the particles that they can deflect. Magnetic shields, on the other hand, do not collect currents and can achieve effective shielding for all expected radiation levels. Finally, plasma shields, are the most lightweight and the least power-consuming of all three approaches, but are also the least mature design approach. They have the potential to outperform the other two designs in terms of radiation shielding capability, but are experimentally unproven, and their functionality is hotly debated.
Examining the different methods of space radiation shielding, it is clear that no single good solution currently exists to adequately protect astronauts from the radiation environment of space. If we wish to travel to Mars, asteroids, or even to the moon for long duration missions, major developments must be made. However, the ideas being examined now lay a solid foundation to grow into feasible solutions in the future.
