Space exploration is one of the most sought out goals for humans, but this in turn has been faced with hostile environment which is a drastic effect on the space craft that then affects man’s desire to explore space.
The paper identifies that for manned space exploration to be achievable, protection from effects of ionizing radiation should be properly looked at. Two major sources of ionizing radiation received in space were identified in this research paper and were termed: Solar Particle Events (SPE) and Galactic Cosmic Rays (GCR).
- Solar particle Events (SPE) is regarded as abrupt, comparatively diminutive and unusual, but of extremely intense flares of low energy (1-100MeV) particles which without safe guard produces lethal dose levels.
- Galactic Cosmic Rays (GCR) termed by a firm dose released by ionizing particles involving energy in the order of 1GeV precisely the highly ionizing high Z ions.
For this effects on the space exploration on manned travels, the paper categorized shielding methods that was considered as ways to help combat these issues. They are Passive and Active shielding.
Passive shielding involved application of sufficient thick plate or slab of an appropriate elected element that could be used to exponentially reduce the effect of radiation. This method was used for the SPE due to the fact that it could be used for low energy particles. But there was a drawback to this method, which was that for greater effect of energy, the shielding material would keep interacting with the ions and then produce secondary particles which can be more detrimental to astronauts health than the incident radiation itself.
Another method was employed for shield which was called bulk shielding, but this ultimately creates load or weight issues on the space crafts, this in turn can cause mass penalty and even increase the expenditure for such space mission. An alternative method for such bulk shielding method was to use light hydrogenated materials like polyethene, which are excellent for space radiation shielding but also was not used for a long mission but within a time frame of 3-6 months.
Active shielding was an option that was explore in this research paper were it involved shielding of ionizing radiation by the principle of deflecting charged particles outside the protected volume using electromagnetic field organized in a suitable configuration. This was a great option instead of carrying additional bulky material for shielding but then it was faced with technical limitations. Other methods for this type of active shielding was also explored but proved not so convincing and effective they include: Electrostatic field, Plasma field, Confined/Unconfined field.
For this method that involved superconducting systems, electric current flows without dissipation, the power requirements is comparatively little and dominated by the cryogenic system that maintains the super-conductor at low temp. This made them the most viable option as termed by the paper for active shielding. But as all other methods, the limitation to this approach was with the mass of the superconducting material and cryogenic system necessary to maintain the superconducting state.
Other previous studies was also looked at in this paper and showed that research has been carried out by some notable bodies such as the ESA and NASA as regards active shielding.
For NASA, under the NAIC program a dual toroidal Solenoid design was brought forward that shield a 7m long and 7m diameter field free cylindrical volume in the center of the habitat able region. The idea was to provide protection in all orientation. They proposed that for a field of 9.2T and a path of 1.7m, the annual dose could be dropped off by 10% of the entire predicted dose.
In the case of the ESA, an Active Radiation Shield for space exploration was termed. They introduced a Racetrack toroid system, this was going to be a magnetic cut-off. In this preference, the superconducting cable, the design of the coils, the evaluation of the generated forces and the torques both in the case of static operation and quenching conditions were deliberated in the study as a function of the shielding performance.
Other designs were also acknowledged in the paper, they include but not limited to: Advanced toroidal magnetic design (Double helix Cool technology) were it gave a 45% reduction with respect to free space (an astronauts without any protection). Also a pumpkin configuration that involved a multiple toroid system where each toroid should be constructed with 3 racetrack coils and also the toroid axes are radial with respect to the space craft’s habitable module.
Conclusion: The various methods shows that active shielding proves better than passive shielding as regards the safeguard of crews from radiation offered in space.
Sources: Md. Abdullah Al Zaman, H.M.A.R. Maruf, M.R. Islam, Neelufar Panna. (2021) Study on superconducting magnetic shield for the manned long termed space voyages. https://doi.org/10.1016/j.ejrs.2021.01.001