Toroidal magnetic fields for protecting astronauts from ionizing radiation in long duration deep space missions

Among the configurations of superconducting magnet structures proposed for protecting manned spaceships or manned deep space bases from ionizing radiation, toroidal ones are the most appealing for the efficient use of the magnetic field, being most of the incoming particle directions perpendicular to the induction lines of the field. The parameters of the toroid configuration essentially depend from the shape and volume of the habitat to be protected and the level of protection to be guaranteed. Two options are considered: (1) the magnetic system forming with the habitat a unique complex (compact toroid) to be launched as one piece; (2) the magnetic system to be launched separately from the habitat and assembled around it in space (large toroid).     

Superconducting magnets and mission strategies for protection from ionizing radiation in interplanetary manned missions and interplanetary habitats

First order evaluations for active shielding based on superconducting magnetic lenses were made in the past in ESA supported studies. The present increasing interest of permanent space complexes, to be considered in the far future as ‘bases’ rather than ‘stations’, located in ‘deep’ space (as it has been proposed for the L1 libration’s point between Earth and Moon, or for Stations in orbit around Mars), requires that this preliminary activity continues, envisaging the problem of the protection from cosmic ray (CR) action at a scale allowing long permanence in ‘deep’ space, not only for a relatively small number of dedicated astronauts but also to citizens conducting there ‘normal’ activities.Part of the personnel of such a ‘deep space base’ should stay and work there for a long period of time. It is proposed that the activities and life of these personnel will be concentrated in a sector protected from Galactic CR (GCR) during the whole duration of their mission. In the exceptional case of an intense flux of Solar Energetic Protons (SEP), this sector could be of use as a shelter for all the other personnel normally located in other sectors of the Space Base.The realization of the magnetic protection of the long permanence sector by well-established current materials and techniques is in principle possible, but not workable in practice for the huge required mass of the superconductor, the too low operating temperature (10–15 K) and the corresponding required cooling power and thermal shielding.However the fast progress in the production of reliable High Temperature Superconducting (HTS) or MgB₂ cables and of cryocoolers suitable for space operation opens the perspective of practicable solutions. In fact these cables, when used at relatively low temperature, but in any case higher than for NbTi and Nb₃Sn, show a thermodynamically much better behavior. Quantitative evaluations for the protection of the sector of the ‘Space Base’ to be protected from GCRs (and therefore from SEPs also) are presented.For possible large outer radius solutions it must in the meantime solve the problem of the assembling or deploying in space the conductors for returning the electric current.     

Active shielding for long duration interplanetary manned missions

For long duration interplanetary manned missions the protection of astronauts from cosmic radiation is an unavoidable problem that has been considered by many space agencies. In Europe, during 2002–2004, the European Space Agency supported two research programs on this thematic: one was the constitution of a dedicated study group (on the thematic ‘Shielding from cosmic radiation for interplanetary missions: active and passive methods’) in the framework of the ‘life and physical sciences’ report, and the other an industrial study concerning the ‘radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars’. Both programs concluded that, outside the protection of the magnetosphere and in the presence of the most intense and energetic solar events, the protection cannot rely solely on the mechanical structures of the spacecraft, but a temporary shelter must be provided. Because of the limited mass budget, the shelter should be based on the use of superconducting magnetic systems. For long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole mission period. This requires the protection of a large habitat where they could live and work, and not the temporary protection of a small volume shelter. With passive absorbers unable to play any significant role, the use of active shielding is mandatory. The possibilities offered by superconducting magnets are discussed, and recommendations are made about the needed R&D. The technical developments that have occurred in the meanwhile and the evolving panorama of possible near future interplanetary missions, require revising the pioneering studies of the last decades and the adoption of a strategy that considers long lasting human permanence in ‘deep’ space, moreover not only for a relatively small number of dedicated astronauts but also for citizens conducting there ‘normal’ activities.     

Manned exploration and exploitation of solar system: Passive and active shielding for protecting astronauts from ionizing radiation—A short overview

In deep space manned missions for the exploration and exploitation of celestial bodies of Solar System astronauts are not shielded by the terrestrial magnetic field and must be protected against the action of Solar Cosmic Rays (SCRs) and Galactic Cosmic Rays (GCRs). SCRs are sporadically emitted, and in very rare but possible events, their fluence can be so high to be lethal to a unprotected crew. Their relatively low energy allows us to conceive fully passive shields, also if active systems can somewhat reduce the needed mass penalty. GCRs continuously flow without intensity peaks, and are dangerous to the health and operability of the crew in long duration (>1year) missions. Their very high energy excludes the possible use of passive systems, so that recourse must be made to electromagnetic fields for preventing ionizing particles to reach the habitat where astronauts spend most of their living and working time. A short overview is presented of the many ideas developed in last decades of last century; ideas are mainly based on very intense electrostatic shields, flowing plasma bubbles, or enormous superconducting coil systems for producing high magnetic fields. In the first decade of this century the problem began to be afforded in more realistic scenarios, taking into account the present and foreseeable possibilities of launchers (payload mass, diameter and length of the shroud of the rocket, etc.) and of assembling and/or inflating structures in space. Driving parameters are the volume of the habitat to be protected and the level of mitigation of the radiation dose to be guaranteed to the crew. Superconducting magnet systems based on multi-solenoid complexes or on one huge magnetic torus surrounding the habitat are being evaluated for defining the needed parameters: masses, mechanical structures for supporting the huge magnetic forces, needed equipments and safety systems. Technological tests are in preparation or planned for improving density of the current, lightness and stability, to increase working temperature of superconducting cables, and for finding light supporting structures and suitable safety architectures, delineating a possible development program for affording this difficult problem.     

Passive cooling of superconducting magnetic systems in space

The equilibrium temperature of a system in space can be lowered by a suitable choice of its geometry and its attitude. This remark is important for devices based on medium temperature and high temperature superconducting materials, and offers the possibility of their fully passive cooling without or with a marginal recourse to active systems. General parameterizations are given and simple schemes discussed. The adopted geometrical configuration and the attitude can enhance the role of passive cooling of the large superconducting magnetic systems required for protecting from ionizing radiation manned habitats in deep space. A specific example based on MgB₂ cable for protecting large volume habitats (500 and 1000 m³) is treated. The systems can be run in deep space at equilibrium temperatures around 20 K mainly by passive cooling, provided that their geometry and attitude would be suitably chosen.     

The European space exploration programme: current status of ESA's plans for Moon and Mars exploration

After a large consultation with the scientific and industrial communities in Europe, the Aurora Space Exploration Programme was unanimously approved at the European Space Agency (ESA) Council at ministerial level in Edinburgh in 2001. This marked the start of the programme's preparation phase that was due to finish by the end of 2004. Aurora features technology development robotic and crewed rehearsal missions aimed at preparing a human mission to Mars by 2033. Due to the evolving context, both international and European, ESA has undertaken a review of the goals and approach of its exploration programme. While maintaining the main robotic missions that had been conceived during Aurora, the European Space Exploration Programme that is currently being proposed to the Aurora participating states and other ESA Member States has a reviewed approach and will feature a greater synergy with other ESA programmes. The paper will present the process that led to the revision of ESA's plans in the field of exploration and will give the current status of the programme.