Fifty years after Neil Armstrong and Buzz Aldrin set foot on the moon, setting health and safety standards for space-flight risks remains a challenge

Recent television programmes celebrating the 50th anniversary of man’s lunar landing have aroused interest regarding the ability of astronauts to stay safe and healthy in space. While the broadcasts made the trip appear exciting and at times anxious, the risks involved in getting Apollo 11 and its crew members to the moon were immense.

According to the National Aeronautics and Space Administration (NASA), human space flight inherently involves a high degree of known risks, as well as uncertain and unforeseeable risks. “Risks to astronauts exist during all phases of any space mission, including terrestrial training and vehicle testing, launch, inflight during the mission, and landing,” the organisation admits.

So, how does NASA address health and safety risks associated with space flight? According to a media statement, the organisation has developed an extensive research portfolio – managed and implemented through its Human Research Programme, the National Space Biomedical Research Institute and other agencies – designed to examine, prevent and mitigate health and safety risks in space.

The risk-management policy comprises two integrated efforts: risk-informed decision-making and continuous risk-management processes. The processes are used across the organisation and apply to engineering, safety and health standards.

Risks are identified based on historical precedence – lessons learned and empirical data – on possible failures in laboratory and other tests, and in discussions with subject-matter experts. Risks are extensively documented and, if possible, quantified.

When a risk is considered to be unacceptably high, alternative designs and mission scenarios are considered, and the risk assessment continues iteratively. The process is not unique to NASA and represents best practice across a number of industries.

In new or emerging areas of concern about space-related health risks, risk assessment may first be based on expert opinion and then be informed by experience gained in a new environment, or through case reports and lessons learned from prior space missions – for example, vision impairment has recently been identified as a risk of space flight.

NASA’s risk-assessment processes initially use a wide margin of uncertainty that, with continued experience, is generally narrowed. Decisions regarding the design and implementation of a mission are made based on a combination of available evidence and best risk estimates.

According to the statement, NASA makes numerous decisions that balance health and safety risks, technological feasibility and financial costs against mission necessity and the lost opportunity that comes when missions are not undertaken.

The organisation states, in part: “An adequately safe system is not necessarily one that completely precludes all conditions that can lead to undesirable consequences.” According to NASA policy, adequately safe systems follow two primary safety principles:

• They meet a minimum threshold level of safety, as determined by analysis, operating experience, or a combination of both;

• They are as safe as reasonably practicable (ASARP).

An assessment of whether a system is ASARP involves weighing its safety performance against the impact of the changes that would need to be done to further improve it.

NASA states: “The system is ASARP if an incremental improvement in safety would require a disproportionate deterioration of system performance in other areas.” Moreover, informed decision-making by those affected is an essential component.

Similar to risk assessment for hardware and software, there is a risk-assessment process for human health risks, and concomitant strategies for mitigating the risks. By necessity, these two processes are connected and iterative.

For example, if radiation exposure in a particular mission is considered too high, this drives the design of the vehicle and the mission design. If there is no engineering or mission design solution to mitigate the risk, then other alternatives are considered, such as redesign of the mission, delays in the mission until technology is available, or making exceptions to the standards.

Fairly early in space-flight development, NASA established a Bioastronautics Roadmap as a framework for identifying and assessing the risks to spacecraft crews from health perspectives, as well as from engineering, technology and system performance aspects.

In the roadmap, “risk” is defined as “the conditional probability of an adverse event from exposure to the space flight environment” and a “risk factor” as a “predisposing condition that contributes to an adverse outcome”.

Specific issues regarding risks have been detailed in the roadmap as they pertain to three design reference missions: a one-year tour of duty on the International Space Station, a month-long stay on the lunar surface, and a 30-month mission to Mars. Design reference missions describe the orbit, mission duration, environments and proposed operations.

There may be multiple design reference missions to a single destination, and each is assessed for challenges, benefits and risks. The scenarios provide context for mission design and risk identification and assessment, and include information on potential transit times, communication lag times, microgravity-exposure and radiation-exposure levels, vehicle requirements, and the extent of proposed extra-vehicular activity.

The Bioastronautics Roadmap has since evolved into the Human Research Roadmap, which categorises health risks into five categories – behavioural health and performance; human health countermeasures (which include bone metabolism and physiology, nutrition, immunology, cardiac and pulmonary physiology, and injury); space radiation; space human factors and habitability; and exploration medical capabilities.

For each of the areas, the roadmap provides research reviews and ratings on risk mitigation and control. The ratings system categorises the risks as controlled, acceptable, unacceptable or insufficient data. The state of research on each of the risks is summarised in a set of evidence reports, with each report updated and reviewed on a regular basis.

These research reviews and ratings provide starting points for identifying gaps and research directions for NASA’s Human Research Programme, and progress on this research is monitored by NASA’s Human System Risk Board.

A number of health risks are known and are mitigated, to the extent feasible, through prevention and intervention strategies, which are continuously evaluated for effectiveness. The seriousness of other likely risks is largely unknown. Still other risks have not yet been anticipated, and will be uncovered only through experience. Thus, 50 years on from the lunar landing, setting health and safety performance standards for a wide array of space flight risks remains a challenge.

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