The Radiation Assessment Detector (RAD) on the Mars Science Laboratory’s Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars, and provide an anchor point to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient Martian environment.

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Mars’ Surface Radiation Environment Measured with the Mars Science Laboratory’s Curiosity Rover

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.

https://science.sciencemag.org/content/sci/340/6136/1080.full.pdf

Measurements of Energetic Particle Radiation in Transit to Mars on the Mars Science Laboratory

Personnel representing several NASA field centers have formulated a "Reference Mission" addressing human exploration of Mars. This report summarizes their work and describes a plan for the first human missions to Mars, using approaches that are technically feasible, have reasonable risks, and have relatively low costs. The architecture for the Mars Reference Mission builds on previous work of the Synthesis Group (1991) and Zubrin's (1991) concepts for the use of propellants derived from the Martian Atmosphere. In defining the Reference Mission, choices have been made. In this report, the rationale for each choice is documented; however, unanticipated technology advances or political decisions might change the choices in the future.

https://spacecraft.ssl.umd.edu/design_lib/nasa-sp6107.mars_drm.pdf

Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Study Team

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment. RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.

The Radiation Assessment Detector (RAD) Investigation

Astronauts on a mission to Mars would be exposed for up to 3 years to galactic cosmic rays (GCR)--made up of high-energy protons and high charge (Z) and energy (E) (HZE) nuclei. GCR exposure rate increases about three times as spacecraft venture out of Earth orbit into deep space where protection of the Earth's magnetosphere and solid body are lost. NASA's radiation standard limits astronaut exposures to a 3% risk of exposure induced death (REID) at the upper 95% confidence interval (CI) of the risk estimate. Fatal cancer risk has been considered the dominant risk for GCR, however recent epidemiological analysis of radiation risks for circulatory diseases allow for predictions of REID for circulatory diseases to be included with cancer risk predictions for space missions. Using NASA's models of risks and uncertainties, we predicted that central estimates for radiation induced mortality and morbidity could exceed 5% and 10% with upper 95% CI near 10% and 20%, respectively for a Mars mission. Additional risks to the central nervous system (CNS) and qualitative differences in the biological effects of GCR compared to terrestrial radiation may significantly increase these estimates, and will require new knowledge to evaluate.

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How Safe Is Safe Enough? Radiation Risk for a Human Mission to Mars

This paper provides a summary of the 2007 Mars Design Reference Architecture 5.0 (DRA 5.0) [1], which is the latest in a series of NASA Mars reference missions. It provides a vision of one potential approach to human Mars exploration, including how Constellation systems could be used. The strategy and example implementation concepts that are described here should not be viewed as constituting a formal plan for the human exploration of Mars, but rather provide a common framework for future planning of systems concepts, technology development, and operational testing as well as potential Mars robotic missions, research that is conducted on the International Space Station, and future potential lunar exploration missions. This summary of the Mars DRA 5.0 provides an overview of the overall mission approach, surface strategy and exploration goals, as well as the key systems and challenges for the first three concepts for human missions to Mars.1,2

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Human exploration of Mars, Design Reference Architecture 5.0

This report serves as the second Addendum to NASA-SP-2009-566, "Human Exploration of Mars Design Reference Architecture 5.0." The data and descriptions contained within this Addendum capture some of the key assessments and studies produced since publication of the original document, predominately covering those conducted from 2009 through 2012. The assessments and studies described herein are for the most part independent stand-alone contributions. Effort has not been made to assimilate the findings to provide an updated integrated strategy. That is a recognized future effort. This report should not be viewed as constituting a formal plan for the human exploration of Mars.

Human Exploration of Mars Design Reference Architecture 5.0, Addendum #2

Human Missions to Phobos and Deimos Using Combined Chemical and Solar Electric Propulsion

Engineering concepts for inflatable Mars surface greenhouses

There are many ways to send humans to Mars Credible technical reports can be traced to the 1950's More recently, NASA has funded major studies that depict a broad variety of trajectories, technologies, stay times, and costs Much of this data is still valid with direct application to today's exploration planning This paper presents results comparing these studies with particular emphasis on the in-space transportation aspects of the mission Specifically, comparisons are made on propulsion systems used for getting the crew and mission equipment from Earth orbit to Mars orbit, descending and ascending from the surface, and returning to Earth orbit Areas of comparison for each of these phases include crew size, mission mass, propellant mass, delta v, specific impulse, transit time, surface stay time, aero-braking, and others Data is analyzed to demonstrate either strong trends toward particular technologies or diverging solutions

/pdf/a-comparison-of-transportation-systems-for-human-missions-to-17rf78vzz4.pdf

Bret G. Drake

Papers

Human exploration of Mars, Design Reference Architecture 5.0

Human Exploration of Mars Design Reference Architecture 5.0, Addendum #2

Human Missions to Phobos and Deimos Using Combined Chemical and Solar Electric Propulsion

Engineering concepts for inflatable Mars surface greenhouses

A Comparison of Transportation Systems for Human Missions to Mars