Only 24 humans have ventured beyond Earth's protective magnetosphere, briefly during the Apollo missions to the Moon. Deep space radiation exposure has a high liklihood of significant biological consequence to astronauts when they explore deep space beyond the magnetosphere such as during a mission to Mars Fig. 1. Human hibernation is not a new concept, with 1950s scientific literature and movies demonstrating its potential use for deep space travel. Synthetic hibernation known as “torpor” would improve the amount of supplies required and therefore lessen fuel...

We investigated radiobiological factors which could be present during torpor and hypothesised their interaction with cosmic radiation. A model of radioresistance with variation in circadian rhythm and temperature was generated. To investigate the effect of decreasing transit time to limit astronaut radiation exposure we used the General Mission Analysis Tool (GMAT). We compared chemical Fig. 3, nuclearFig. 4and electrical Fig. 5 propulsion systems with equal mass to create a reasonable comparison Table 1. Transit times from Earth to Mars using chemical, nuclear and electrical propulsion...

We hypothesised that whilst synthetic torpor for astronauts could lower metabolic rate, create a hypoxic and cooled environment to facilitate radioprotection, an enforced circadian rhythm may also be beneficial. This concept is shown graphically in Fig. 7. Rhythmic control of cells may be acheived by lighting schedulesand regular feeding intervals. Estimated transit times with the different propulsion systems and resultant effective dose to astronauts are summarised in the table below. Propulsion method Transit time Radiation dose received Chemical 258 days 165.9mSv Nuclear 209 days 134.4mSv...

A state ofhibernationfor astronauts in the form of induced torpor may provide a radioprotective strategy in addition to improved weight and therefore fuel requirements for deep space travel. An enforced circadian rhythm with lighting and feeding schedulesmay play a significant role in cellularresistance to cosmic radiation beyond the magnetosphere. Our simulation demonstrated a 70% reduction in effective dose received by the phantomwhen an electrical propulsion system was used compared with current day chemical propulsion.

T. Squire. Department of Radiation Oncology, Canberra Region Cancer Centre. Yamba Drive. Garran. A.C.T. 2605. Australia mail to: [email protected] @SpaceRadOnc Fig. 8 A. Ryan. Applied and Plasma Physics Research Group. School of Aerospace Mechanical and Mechatronic Engineering, University of Sydney. Camperdown. N.S.W. 2006. Australia S. Bernard. National Centre for Scientific Research. Institut Camille Jordan. Université de Lyon. Villeurbanne & Inria Grenoble. France

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