Space Radiation and Human Flight to Mars

Abstract

Space radiation affects the design and operations of all systems launched above Earth's ionosphere. Numerous research articles in this journal over the years have discussed such issues. Radiation is of particular concern for human flight to low Earth orbit and beyond. Since the earliest days of the U.S. space program, many NASA missions have been devoted wholly or in part to better understand the radiation environment that can affect human flight. The most recent of these is the Lunar Reconnaissance Orbiter that carried a comprehensive instrument (Cosmic Ray Telescope for the Effects of Radiation; CRaTER) to characterize, with modern detection technologies, the radiation environment of the Moon in anticipation of future lunar missions, including the Moon as a way point to an eventual human landing on Mars. A special section of Space Weather is devoted to CRaTER measurements of the linear energy transfer (LET) radiation spectra behind shielding material (http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1542-7390/specialsection/CRATER1). The CRaTER LET spectra provide a direct link between the radiation environment and biological effectiveness. Looking to the future of human flight to Mars, the recent congressionally requested (NASA Authorization Act 2010) report of the National Research Council (Pathways to Exploration: Rationales and Approaches for a U.S. Program of Human Space Exploration; http://www.nap.edu/catalog.php?record_id=18801) includes considerable discussion of space radiation for mission success. This report is the most comprehensive examination to date of where U.S. capabilities currently stand and what is required for a Mars mission and considers three operational stepping stone theaters: (a) cislunar space, including the lunar surface, (b) near-Earth asteroids, and (c) Mars, including a flyby mission, Martian moons, and Martian surface. Solar energetic particles (SEP) and galactic cosmic rays fill all of these theaters of operation. Thus, “radiation safety” is one of three major recommendations in the report for high-priority technology development (the other two being “entry, descent, and landing for Mars” and “advanced in-space propulsion and power”). The report importantly concludes that the “technical challenges” for addressing astronaut radiation safety is “high” because no suitable approach has as yet been identified for providing such safety. Further, the “capability gap” is rated “high” for the reason that “the ability to provide the level of radiation safety required for a human mission to the Mars surface is so far beyond the state of the art.” These conclusions of this important report provide challenges to the space weather research community as to how best to aid in addressing the technical challenges and the huge capability gap. Are better measurements of the radiation environments needed? What are the current capabilities for forecasting deleterious SEP events, and are they sufficient? How best to interface with designers of shielding and with medical investigators? Many opportunities thus exist for important contributions to overcome the challenges and to fill the capability gap. I hope that these opportunities will be seized and significant contributions made. Louis J. Lanzerotti is Editor of Space Weather and a distinguished research professor of physics at the New Jersey Institute of Technology in Newark. He is retired from Lucent Technologies Bell Laboratories. Email: [email protected]