and healing, and active shape control. Improved cryogenic boil-off protection, for instance, would considerably reduce the mass required for a Mars mission. Such multifunctional materials and structures will require new design analysis tools and might exhibit new failure modes; these should be understood for use in systems design and space systems operations.

2. Reduced Mass. Reduce mass of launch vehicle, spacecraft, and propulsion structures to increase payload mass fraction, improve mission performance, and reduce cost.

Lightweight materials and structures are required to enhance mission performance and enable new mission opportunities. Advanced composites and revolutionary structural concepts would substantially reduce structural weight in launch vehicles, cryo-tanks, propulsion systems, and spacecraft, increasing the payload mass fraction. More energetic propellants would reduce fuel mass in solid motors, and higher-temperature and lower-erosion materials would reduce the weight of engine nozzles. Reduced mass of inflatable habitats and space structures, deployable space systems, and large-scale structures would enable new exploration and science missions.

3. Computational Modeling. Advance new validated computational design, analysis, and simulation methods for materials and structural design, certification, and reliability.

First-principles physics models offer the game-changing potential to guide tailored computational materials design. Multi-scale models are needed to encompass composite materials, interfaces, failure, multi-component and deployable structures, and integrated control systems; multi-physics models are needed to address manufacturing processes, operation in extreme environments, and active materials. Conservatism is embedded in established design methodology in several ways, including statistics-based material allowables and traditional factors of safety. Uncertainty management and quantification, if supported by an experimental foundation, offers the potential to reduce weight as well as certification and life-cycle costs by rationalizing sometimes excessive conservatism. Physics-based and computation-based errors can be quantified and compared to required accuracy and confidence levels. A validated computational modeling methodology could provide the basis for certification by analysis, with experimental evidence, as available, used to verify and improve confidence in the suitability of a design. Computational models will be needed to design-in improved reliability, as well as to interpret measurements made by health-monitoring systems. Structures may need to be designed differently to accommodate health monitoring, including unobtrusive sensors and sensor integration, and to enable materials and structures health assessment and sustainability for long-duration missions.

4. Large-Aperture Systems. Develop reliable mechanisms and structures for large-aperture systems. These must be stowed compactly for launch, yet achieve high-precision final shapes.

Numerous NASA missions employ mechanical systems and structures that must deploy reliably in extreme environments, often to achieve a desired shape with high precision. Such systems include instrument arms, antennas, optical surfaces, solar sails, and some re-entry thermal protection systems. These can be deployed, assembled, or manufactured in space, and may involve flexible materials. Modularity and scalability are desirable features of such concepts, and may require development of autonomous adaptive control systems and technology to address critical functional elements and materials. Concerns include sliding joints and bearings, friction and tribology, coatings and lubrication, as well as their performance and durability over extended periods in storage and extreme operational environments. Performance of large precise space systems cannot be directly verified in the 1-g ground environment, so the ISS would be useful for verification of such concepts.

5. Structural Health Monitoring. Enable structural health monitoring and sustainability for long-duration missions, including integration of unobtrusive sensors, and responsive on-board systems.

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