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ESDMD #0308: Radiation Countermeasures

Mass-efficient shielding and other countermeasures, including medical ones, to protect crew from space radiation on long missions (bin 5, rating 47 of 57). Shielding against solar particle events (SPEs) is "relatively well understood", but galactic cosmic radiation (GCR) "is very difficult to mitigate": passive shielding is too heavy and active methods are "very low maturity". The gap's impacts note "Using lunar proving ground to prove out Mars" (Tech gaps spreadsheet, ESDMD #0308).

Quotations below are from row ESDMD #0308 of the tech gaps spreadsheet. ADD Rev C's Appendix D prints the same table for this gap, and it matches the row field for field (ADD Rev C, p. 217).

Description

"Solar Particle Event (SPE) radiation shielding is relatively well understood and passive shielding can be applied to small volumes of habitat. Galactic Cosmic Radiation (GCR) is very difficult to mitigate. Passive shielding is mass-prohibitive, while active methods are very low maturity and utilize substantial vehicle mass and power. New shielding techniques as well as other potential mass-efficient countermeasures for ionizing and non-ionizing radiation are needed to reduce the risk of adverse medical impacts on crew. GCR shielding will also help shield for SPE radiation."

Impacts and benefits: "With gap closure, the benefits are reduction in crew lifetime radiation dose and reduction of detrimental crew health effects from radiation exposure during long-duration exploration missions. Using lunar proving ground to prove out Mars."

Current state of the art

"Operational and physical mitigation strategies are used to reduce crew doses on the ISS. Current ionizing radiation mitigation strategies are based on the application of the As Low As Reasonably Achievable (ALARA) principle to protect the crew from severe long-term effects from radiation exposure (NASA-STD-3001-Vol 2) but there have been minimal medical radiation countermeasures that have been identified/validated to fully protect crew against long-term health effects from radiation exposure. Additionally, current radiation analysis tools closely align with predicted space measurements, but are less accurate for thick shielding which would be found in long duration mission vehicles and habitats. GCRs cannot be effectively mitigated against with the SOA."

Performance target

  • Moon/Mars: "Develop long-duration, mass-efficient passive and active shielding, time, and distance countermeasures to mitigate adverse crew health outcomes to ionizing and non-ionizing radiation including SPE and GCR conditions (reference NASA-STD-3001 V1 4030, 4031)."
  • Mars: "In addition, increase in performance target for longer duration missions."

Child gaps

  • 0308-01: Solar Particle Event (SPE) radiation effects mitigation and shielding
  • 0308-02: Radiation risk models for crew health and performance
  • 0308-03: Biomedical countermeasures to mitigate health effects from exposure to space radiation
  • 0308-04: Galactic Cosmic Radiation (GCR) effects mitigation

Traceability

  • Use cases and functions: UC-H-102 M -- FN-H-106 M; UC-H-103 M -- FN-H-110 M; UC-X-105 M; UC-X-106 M; UC-X-109 M
  • Against the Mars decomposition: the gap lists the three countermeasure use cases with no function, but the Mars spreadsheet gives each two: UC-X-105 M has FN-X-101 M and FN-X-103 M, UC-X-106 M has FN-X-102 M and FN-X-105 M, UC-X-109 M has FN-X-105 M and FN-X-108 M. This is the Mars counterpart of #0307's lunar case (Mars use cases; open question 60).
  • Definition tasks: Mars: Maximum Total Crew Mission Duration

All the use cases listed are Mars ones (ending "M"), although the performance target is "Moon/Mars" and the segments include Sustained Lunar Evolution. The first two pairs also appear under the radiation monitoring gap #0307.

Segments and sub-architectures

Priority

Priority bin 5, overall prioritization rating 47 of 57. The rating is "the gap's location in the prioritized list of gaps", so 1 is the highest priority, and bins group gaps of similar priority, bin 1 highest. Criticality, urgency, breadth and depth set the order; cost is not considered (ADD Rev C, pp. 78, 199; method on the gaps index).

Moon Base relevance

Not established by the sources so far. The Users Guide does not name #0308 among its near-term Moon Base challenges (Technology and knowledge challenges).

Sources

Tech gaps spreadsheet, ESDMD #0308 · ADD Rev C, pp. 78, 199, 217