American Institute of Aeronautics and Astronautics 1 RadWorks Storm Shelter Design for Solar Particle Event Shielding Matthew A. Simon, Jeffrey Cerro, and Martha Clowdsley NASA Langley Research Center, Hampton, VA, 23681, USA In order to enable long-duration human exploration beyond low-Earth orbit, the risks associated with exposure of astronaut crews to space radiation must be mitigated with practical and affordable solutions. The space radiation environment beyond the magnetosphere is primarily a combination of two types of radiation: galactic cosmic rays (GCR) and solar particle events (SPE). While mitigating GCR exposure remains an open issue, reducing astronaut exposure to SPEs is achievable through material shielding because they are made up primarily of medium-energy protons. In order to ensure astronaut safety for long durations beyond low-Earth orbit, SPE radiation exposure must be mitigated. However, the increasingly demanding spacecraft propulsive performance for these ambitious missions requires minimal mass and volume radiation shielding solutions which leverage available multi-functional habitat structures and logistics as much as possible. This paper describes the efforts of NASA’s RadWorks Advanced Exploration Systems (AES) Project to design minimal mass SPE radiation shelter concepts leveraging available resources. Discussion items include a description of the shelter trade space, the prioritization process used to identify the four primary shelter concepts chosen for maturation, a summary of each concept’s design features, a description of the radiation analysis process, and an assessment of the parasitic mass of each concept. Nomenclature Acronyms AES = Advanced Exploration Systems BEO = Beyond Earth Orbit BNNT = Boron Nitride Nanotubes CAD = Computer-Aided Design CQ = Crew Quarter CTB = Cargo Transfer Bag DSH = Deep Space Habitat FAX = Female Adult voXel GCR = Galactic Cosmic Ray HAT = Human Spaceflight Architecture Team HDU = Habitat Demonstration Unit HMC = Heat Melt Compactor HZETRN = High charge (Z) and Energy TRaNsport code ISS = International Space Station KPP = Key Performance Parameter LEO = Low Earth Orbit OLTARIS = On-Line Tool for the Assessment of Radiation in Space SPE = Solar Particle Event I. Introduction he ability to affordably and sustainably mitigate the risks associated with exposure of human crews to space radiation is a major challenge in designing for human exploration of the Solar System beyond Earth orbit (BEO). Exposure of astronaut crews to the deep space radiation environments increase the risk of deleterious physiological effects such as radiation sickness and late-term effects, central nervous system damage, and increased incidence of debilitating or fatal cancers. Current design and operational strategies for mitigating radiation-related risks include: 1) the deployment of radiation monitoring instrumentation to enable a measured, balanced, real-time response to radiation events during human missions, and 2) the addition of “shielding” to spacecraft designs to protect the crew directly. Legacy approaches of each strategy, while valid in concept, do suffer from shortcomings in their current and past engineering implementations. NASA’s RadWorks Advanced Exploration Systems (AES) Project builds upon past lessons and advances real-world solutions to radiation risk mitigation through analysis, design, demonstrations and operational implementation on future missions. The RadWorks Project consists of two top-level elements. The first of these is the maturation of advanced, miniaturized radiation measurement technologies, or dosimeters. The second is the development of a radiation storm shelter which leverages the design of multi-functional habitat structures and logistics to minimize radiation shielding mass at launch. This paper focuses on the second of these, the Storm Shelter. T https://ntrs.nasa.gov/search.jsp?R=20170002287 2020-05-30T03:34:36+00:00Z
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American Institute of Aeronautics and Astronautics
1
RadWorks Storm Shelter Design for
Solar Particle Event Shielding
Matthew A. Simon, Jeffrey Cerro, and Martha Clowdsley
NASA Langley Research Center, Hampton, VA, 23681, USA
In order to enable long-duration human exploration beyond low-Earth orbit, the risks
associated with exposure of astronaut crews to space radiation must be mitigated with
practical and affordable solutions. The space radiation environment beyond the
magnetosphere is primarily a combination of two types of radiation: galactic cosmic rays
(GCR) and solar particle events (SPE). While mitigating GCR exposure remains an open
issue, reducing astronaut exposure to SPEs is achievable through material shielding because
they are made up primarily of medium-energy protons. In order to ensure astronaut safety
for long durations beyond low-Earth orbit, SPE radiation exposure must be mitigated.
However, the increasingly demanding spacecraft propulsive performance for these
ambitious missions requires minimal mass and volume radiation shielding solutions which
leverage available multi-functional habitat structures and logistics as much as possible. This
paper describes the efforts of NASA’s RadWorks Advanced Exploration Systems (AES)
Project to design minimal mass SPE radiation shelter concepts leveraging available
resources. Discussion items include a description of the shelter trade space, the prioritization
process used to identify the four primary shelter concepts chosen for maturation, a summary
of each concept’s design features, a description of the radiation analysis process, and an
assessment of the parasitic mass of each concept.
Nomenclature
Acronyms
AES = Advanced Exploration Systems
BEO = Beyond Earth Orbit
BNNT = Boron Nitride Nanotubes
CAD = Computer-Aided Design
CQ = Crew Quarter
CTB = Cargo Transfer Bag
DSH = Deep Space Habitat
FAX = Female Adult voXel
GCR = Galactic Cosmic Ray
HAT = Human Spaceflight Architecture Team
HDU = Habitat Demonstration Unit
HMC = Heat Melt Compactor
HZETRN = High charge (Z) and Energy
TRaNsport code
ISS = International Space Station
KPP = Key Performance Parameter
LEO = Low Earth Orbit
OLTARIS = On-Line Tool for the Assessment of
Radiation in Space
SPE = Solar Particle Event
I. Introduction
he ability to affordably and sustainably mitigate the risks associated with exposure of human crews to space
radiation is a major challenge in designing for human exploration of the Solar System beyond Earth orbit (BEO).
Exposure of astronaut crews to the deep space radiation environments increase the risk of deleterious physiological
effects such as radiation sickness and late-term effects, central nervous system damage, and increased incidence of
debilitating or fatal cancers. Current design and operational strategies for mitigating radiation-related risks include:
1) the deployment of radiation monitoring instrumentation to enable a measured, balanced, real-time response to
radiation events during human missions, and 2) the addition of “shielding” to spacecraft designs to protect the crew
directly. Legacy approaches of each strategy, while valid in concept, do suffer from shortcomings in their current
and past engineering implementations. NASA’s RadWorks Advanced Exploration Systems (AES) Project builds
upon past lessons and advances real-world solutions to radiation risk mitigation through analysis, design,
demonstrations and operational implementation on future missions.
The RadWorks Project consists of two top-level elements. The first of these is the maturation of advanced,
miniaturized radiation measurement technologies, or dosimeters. The second is the development of a radiation storm
shelter which leverages the design of multi-functional habitat structures and logistics to minimize radiation shielding
mass at launch. This paper focuses on the second of these, the Storm Shelter.
There is no change in concept ranking order for equal FOM weighting vs. Baseline FOM weighting for either the 50%
or 70% radiation reduction cases. Though there is difference in going from the 50% to the 70% condition.
Wearables drop to mid to low ranking for the 70% radiation conditions.
For 70% radiation reduction, individual deployables are the second most favored concept. Note this is tempered by the
fact that HMC bricks were not used for the crew quarters option and a large amount of water is parasitic for the case of
70% radiation reduction.
For a mass savings only weighting set, in the case of 50% radiation reduction, the reconfigurable structures and
logistics approach is best (Figure 20 red bar only)
For a mass savings only judgment, in the case of 70% radiation reduction, the individual deployable approach is best
(Figure 21 red bar only)
Filling wearables on an as needed basis is not an attractive option.
The use of the decision analysis process is useful for group discussion and understanding of each protection
mechanism’s pros and cons from a system viewpoint. Based upon the results, the crew quarters-derived shelter
concept has consistent merit and should be investigated in future work. The deployable concept, despite achieving
fairly good ratings, is considered somewhat similar to a crew quarters approach without the inherent habitability
advantages a crew quarters. However, the deployable concept also shows the advantage possible with incorporating
HMC bricks and food for protection in crew quarters-derived concepts to reduce the amount of parasitic water
required. The reconfigurable structures approach was somewhat poorly rated, but is unique in that it demonstrated
the merit of a single protection region for the full crew. The wearable approach, which was well rated for the 50%
radiation reduction condition, is seen as a useful means to provide augmentation to other concepts and short duration
mission situations.
VIII. Conclusions
In summary, several viable concepts were identified and assessed to protect astronauts from SPEs. 50% and
70% reductions in effective dose over an unprotected habitat were achieved with practical amounts of shielding
leveraging available logistics and consumables to provide reasonable parasitic masses. Several additional
conclusions from this work include:
The development of mass-efficient, multifunctional elements that facilitate the deployment, utilization, and disposition
of a shelter with sufficient shielding properties is an enabling technology for long duration space exploration beyond
Earth orbit.
The decision analysis tool allows the decision maker to determine sensitivity of selection ranking to figure of merit
importance, or changes in figure of merit ratings. A selection process has been demonstrated to quantify storm shelter
performance from a system level viewpoint. Replications of this process may require resetting of FOMs, weightings, or
alternatives to be used on additional habitat elements not considered here, but should hold as an effective assessment
tool.
Water shielding is non-parasitic only if the water can be used, at least in contingency if not in daily living. To be
useable as non-parasitic the water must be extractable from the water wall such as by being plumbed into the existing
water system, or by the water wall segment having a positive expulsion device.
o For assumed conditions, 30 day supply – 1300 lbm contingency water, water wall solutions were
advantageous if the radiation requirements were not severe, or if logistics also assist in shielding.
o In conditions requiring moderate radiation protection requirement, the wearable option may be sufficient as it
easily can hold the required contingency water.
o If only contingency water is used for radiation shielding, the water container should simply be one that is of a
bladder nature such that it can be manually drained.
In comparison to water, HMC brick shielded designs were not considered parasitic. As a result, conditions which
require large amounts of shielding water (e.g., 70% radiation reduction) are biased on a mass savings basis towards
HMC bricks. However HMC bricks are not available early in the mission timeline. It was assumed food packets or
other logistics packages would have to be available for pre-placement in a radiation shield which will over mission time
transition to HMC brick coverage.
Recommendations for Habitat Design and Use:
o In general for deep space habitat design, keep crew surrounded by logistics and element systems, Ex: Crew
quarters down the center of a cylinder with logistics surrounding in an annular manner.
16
o If using HMC brick type solutions, is it feasible to keep brick dimensions and food packet dimensions of
similar nature (or perhaps of an even multiple) such that food can easily be used for radiation protection until
utilized when it is then replaced by bricks.
Future collaborations with other habitation subsystems are critical for implementing low mass solutions to deep space
habitation challenges such as SPE radiation protection.
IX. Recommendations and Future Work
The following concepts are being carried forward into FY ’13: Develop a full scale model of a crew quarters waterwall protection mechanism to be incorporated into the waypoint
DSH design.
Develop a full scale model of a centralized storm shelter constructed from dual use panels and reconfigured logistics to
be incorporated into the waypoint DSH design.
Maintain the wearable approach as a possible demonstration item for augmentation of the two primary concepts
selected.
There is a need to increase each of these shelter concepts’s definition with respect to deployment operations,
subsystem needs, ventilation, comfort (heat, humidity), lighting, power, etc. Operational risks and system integrity
issues associated with water based shielding concepts were not quantified in this phase of the project. Such work
should be continued through the crew quarters selected approach.
Finally, knowledge of the amounts of logistics on hand through a mission timeline is important to know if
sufficient radiation protection is available for reconfiguration during an SPE. It is suggested to perform Discrete
Event Simulation (DES) to quantify logistics, food product, and waste product usage over time. DES scenarios can
answer operational questions such as how much of a particular item is required at mission start, how much is
available throughout the mission and where at any point in time are the items located. Manpower is not currently
unidentified for such work, but it may prove crucial in future design efforts.
Finally lessons learned from the FY’12 Storm Shelter radiation assessment and design process should be
leveraged to influence the design and layout of future habitation concepts. Tightly coupled integration of all
subsystems will be necessary to enable future deep space habitation challenges.
Appendix A – Parasitic Mass Estimates
17
Table 11 – Parasitic mass estimate for wearable protection concept (50% dose reduction, 2.8 inches water)
Table 12 - Parasitic mass estimate for wearable protection concept (70% dose reduction, 6.1 inches water)
Table 13 - Parasitic mass estimate for individual, deployable protection concept (50% dose reduction)
deploy in less than 60 minutes facilitates egress during an SPE design for ops in 1g env.
added mass % of baseline protection deployable by 2 persons or less integrates with FY14 HDU
habitability protects 4 astronauts
Preference Set = Baseline
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Deployable Reconfigurable Structure Reconfigurable Structure & Logistics Adjustment Wearable Prefilled Wearable Fill as Needed
Utility 0.898 0.820 0.766 0.741 0.678 0.435
deploy in less than 60 minutes added mass % of baseline protection facilitates egress during an SPE
protects 4 astronauts design for ops in 1g env. deployable by 2 persons or less
habitability integrates with FY14 HDU
Preference Set = All Weights Equal
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Wearable Prefilled Deployable Reconfigurable Structure Reposition Structure & Logistics Adjustment Wearable Fill as Needed
Utility 0.963 0.835 0.800 0.788 0.766 0.666
protects 4 astronauts added mass % of baseline protection facilitates egress during an SPE
habitability design for ops in 1g env. deployable by 2 persons or less
deploy in less than 60 minutes integrates with FY14 HDU
Preference Set = All Weights Equal
24
50% Radiation Reduction 70% Radiation Reduction
Mass Savings
Emphasis
Figure 20
Figure 21
Minimum
Deploy Time
Emphasis
Figure 22
Figure 23
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Deployable Reconfigurable Structure Wearable Prefilled Reconfigurable Structure & Logistics Adjustment Wearable Fill as Needed
Utility 0.804 0.695 0.566 0.549 0.465 0.090
deploy in less than 60 minutes facilitates egress during an SPE design for ops in 1g env.
added mass % of baseline protection deployable by 2 persons or less integrates with FY14 HDU
habitability protects 4 astronauts
Preference Set = KPP_Ops_Bias
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Wearable Prefilled Deployable Reconfigurable Structure Reconfigurable Structure & Logistics Adjustment Wearable Fill as Needed
Utility 0.927 0.722 0.657 0.608 0.511 0.479
deploy in less than 60 minutes facilitates egress during an SPE design for ops in 1g env.
added mass % of baseline protection deployable by 2 persons or less integrates with FY14 HDU
habitability protects 4 astronauts
Preference Set = KPP_Ops_Bias
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Deployable Reconfigurable Structure & Logistics Adjustment Wearable Prefilled Reconfigurable Structure Wearable Fill as Needed
Utility 0.748 0.734 0.552 0.540 0.535 0.195
added mass % of baseline protection facilitates egress during an SPE design for ops in 1g env.
deploy in less than 60 minutes deployable by 2 persons or less integrates with FY14 HDU
habitability protects 4 astronauts
Preference Set = KPP_Mass_Bias
Ranking for Select Concept Goal
Alternative CQ Waterwall Prefilled Wearable Prefilled Deployable Reconfigurable Structure & Logistics Adjustment Reconfigurable Structure Wearable Fill as Needed
Utility 0.931 0.720 0.677 0.622 0.597 0.518
added mass % of baseline protection facilitates egress during an SPE design for ops in 1g env.
deploy in less than 60 minutes deployable by 2 persons or less integrates with FY14 HDU
habitability protects 4 astronauts
Preference Set = KPP_Mass_Bias
25
Appendix C – RadWorks Storm Shelter Project Requirements
Reqt # Shall Statement RationaleKPP?
(Y/N)
Threshold
Value (for
KPP)
Goal Value (for
KPP)Verification Success Criteria Verif. Method
SS001Storm sheltering shall protect 4
astronauts.
Sheltering must be adequately sized to
accommodate all personnel anticipated
to inhabit the HDU simultaneously.
Demonstrate that storm sheltering is of
sufficient size to accommodate TBR
astronauts.
Demonstration
SS002 <Deleted>
SS003
Storm sheltering shall provide crew
protection for a nominal 36 hour
habitability period.
Storm sheltering configuration should be
reasonable for astronaut habitation given
the limited space of the shelter.
No
Astronauts remain sufficiently
comfortable and accommodated for a 36
hour SPE.
Demonstration
SS004Storm sheltering shall be deployed/
assembled in less than 60 minutes.
Sheltering set-up should be easily
achievable based on time between
warning and SPE event.
Yes 60 min 15 min
Demonstrate that storm shelter can be
deployed/assembled in the time
required.
Demonstration
SS005Added mass shall be less than 20% of
the raw shielding mass.Avoidance of parasitic mass. Yes 20% 10%
Show analysis results that verify
adherence to mass requirements.Analysis
SS006The astronauts 90% percentile SPE
exposure shall be reduced by 50%.
Effective protection will increase
allowable astronaut time in space and
operational flexibility.
Yes 50% 70%Analysis results document required SPE
protection.Analysis
SS007
Storm sheltering shall be designed for
space operations loads equivalent in a
1-g environment.
For handling demonstration, the
operational environment should be
replicated as closely as possible.
Reduced-g will be tracked analytically.
NoShow analysis results that verify
adherence to gravity requirement.Analysis
SS008 <Deleted>
SS009Storm sheltering shall integrate with
FY14 HDU configuration.
Storm sheltering must effectively
integrate with the HDU without impact to
HDU functionality.
NoDemonstrate integration of storm
sheltering with HDU.Demonstration
SS010A minimum of 3 storm sheltering
design concepts shall be identified.
Multiple concepts provide means for
users to understand benefits and risks
associated with each concept.
NoShow design concepts via CAD models
and/or sub-scale models.Inspection
SS011Storm shelter features shall facilitate
astronaut egress during SPE.
Personnel may need brief access to other
areas of the habitat during a storm event
for purposes of personal hygiene, to
perform a short term maintenance task,
or to maintain habitat safety.
NoDemonstrate that storm shelter features
facilitate egress during a storm event.Demonstration
SS012
Deployment/assembly of storm
sheltering shall require not more than
2 persons.
So as to have minimum impact on
mission operations, it is necessary that
the number of persons required for
assembly of the storm shelter be
minimized.
No
Demonstrate that storm shelter can be
deployed/assembled by not more than 2
persons.
Demonstration
26
Acknowledgments
The authors wish to acknowledge the contributions of all of the members of the AES RadWorks Storm Shelter
Team:
Thomas L. Jordan (Technical lead), H. Lee Abston, Robert C. Andrews, Heather L. D. Altizer, Sherry B.
Araiza, Vincenzo M. Le Boffe, W. David Castle, Jeffrey A. Cerro, Adam M. Gallegos, Kara Latorella,
Nicole A. Hintermeister, Samuel James, William M. Langford, Lee Noble, Allison S. Popernack, Edward J.
Shea, Judith J. Watson, and Sandy R. Webb.
The authors also wish to recognize the contributions of the AES RadWorks Leadership Team, both past and
present, for championing this work and providing valuable guidance:
Bobbie G. Swan (project manager), Deborah M. Tomek (former deputy project manager), M. David
Moore, (acting deputy project manager), Catherine D. McLoed (system engineering and integration lead),
E. Neal Zapp (former project scientist), and Edward J. Semones (project scientist).
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