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Components for Extreme Environments

Description:

Scope Title:

Mechanisms for Extreme Environments

Scope Description:

A return to the Moon to extend human presence, pursue scientific activities, use the Moon to prepare for future human missions to Mars, and expand Earth’s economic sphere will require investment in developing new technologies and capabilities to achieve affordable and sustainable human exploration. From the operational experience gained and lessons learned during the Apollo missions, conducting long-term operations in the lunar environment will be a particular challenge given the difficulties presented by the extreme environments. The Apollo missions and other lunar exploration have identified significant extreme environment-related problems that will challenge future mission success.

Mechanisms in extreme environments must function in the presence of lunar regolith and charged dust, micrometeoroids, extreme temperature variations, plasma, high-energy cosmic rays and other ionizing radiation, solar ultraviolet (UV) and other electromagnetic (EM) radiation, changing gravitational conditions, and other electrically induced effects.

Mechanical systems will need to operate on the dusty surface of the Moon for months to years. These systems will be exposed to the harsh extreme environments and will have little to no maintenance.

New environmentally hardened mechanism technologies also need to be scalable from small exploration-type devices moving a few grams of materials, to larger scale equipment used for materials handling and transport for in-situ resource utilization (ISRU) activities with the capability to move hundreds of kilograms of materials.

This scope seeks scalable mechanism technologies that can function in these environments, including:

  • Actuators and power transfer components (motors, pistons, shape memory alloy, gear, belt, chain, steering, suspension, hinges, bearings, etc.).
  • Fastening, joining, and securing components and hardware (structural connections, threaded fasteners, quick pins, latches, restraint systems).
  • Sealing materials and techniques that can keep out regolith and operate in the extreme Moon/Mars environments.
  • Dust-tolerant fluid and electrical connectors (quick disconnects, umbilicals, modular commodity interfaces).
  • Moving components for dust protection (iris, hatch, covers, airlocks, closures, fabric/flexible protection).
  • Tools and devices for exploration and ISRU (sample tools, dust cleaning, landing gear, pointing actuator).
  • Materials handling and transportation components (hoist, lift, pallet, pick and place, common transport interface, etc.).
  • Implements for regolith moving, digging, pushing, transporting, compacting, and for construction work with regolith in general.

Successful solutions will have the following performance characteristics:

  • Operational for extended service of 10 to 100 months with limited or no maintenance.
  • Linear and static joints will function and perform the designed actuation/motion/mate-demate cycles of 1,000 or higher.
  • Linear and static joints will function with minimal solid film or without lubrication.
  • Rotational joints will have operational lifetimes on the order of hundreds of thousands of cycles.
  • All mechanisms will function throughout lunar temperature cycles between 127 °C (260 °F) and -173 °C (-280 °F).
  • All mechanisms will function in the extreme cold of permanently shadowed regions (‑238 °C) (-396 °F).
  • All mechanisms will function reliably with lunar regolith (simulant) coating the exposed mechanism surfaces.
  • All mechanisms will function in the high vacuum lunar environment of 10-9 Torr.
  • All mechanisms and materials will function in the lunar electrostatic and radiation environment.

Expected TRL or TRL Range at completion of the Project: 2 to 6

Primary Technology Taxonomy:

  • Level 1 07 Exploration Destination Systems
  • Level 2 07.2 Mission Infrastructure, Sustainability, and Supportability

Desired Deliverables of Phase I and Phase II:

  • Research
  • Analysis
  • Prototype
  • Hardware
  • Software

Desired Deliverables Description:

Research should be conducted to demonstrate technical feasibility during Phase I and show a path toward Phase II demonstration, with delivery of a demonstration package for NASA testing in operational test environments at the completion of the Phase II contract.

Phase I Deliverables: Research, identify, and evaluate candidate technologies or concepts for cold- and dust-tolerant mechanisms. Simulations or laboratory-level demonstrations are desirable. Deliverables must include a report to document findings.

Phase II Deliverables: Emphasis should be placed on developing, prototyping, and demonstrating the technology under simulated operational conditions (regolith, thermal, vacuum). Deliverables shall include a report outlining the path showing how the technology could be matured, scaled, and applied to mission-worthy systems; functional and performance test results; and other associated documentation. Deliverable of a functional prototype is expected at the completion of the Phase II contract. The technology concept at the end of Phase II should be at a TRL of 6 or higher.

State of the Art and Critical Gaps:

Previous solutions used in the Apollo program did not address the current need of long-term usage. Terrestrial solutions often employ materials or methods that are incompatible with the lunar environment.

Critical Gaps:

  • Seals at rotary and linear joints are very common for actuation in dusty environments. Most of these seals, however, use elastomers that would off-gas and become brittle in a lunar radiation environment and at lunar temperatures. Solutions are needed that employ advanced materials, metallic seals, or nontraditional techniques that can operate in the lunar environment for an extended period of time (months to years).
  • Bearings that are tolerant of dust infiltration are needed. Regolith getting past the protective seals and into bearings is a common failure point. Solutions are needed for bearings that are highly dust tolerant to reduce the risk of failures due to dust intrusion.
  • Lubrication required for mobility freezes at operational temperatures.
  • Operations on the lunar surface will include assembly, construction, and extravehicular activity (EVA) tasks. These tasks will involve the mating/demating of various structural, electrical, and fluid connections. Dust on the surface of these joints will impede their proper function and lead to failures. Solutions are needed to protect these joints from dust contamination.
  • Dust-protective enclosures, hatches, and moving covers are needed to protect delicate components. Materials and coatings are needed that eliminate or minimize the adherence of lunar dust to these surfaces. Solutions are needed for self-cleaning shapes, materials, and mechanisms that can clean/remove/reject regolith from vital moving parts of mechanisms as they operate.

Relevance / Science Traceability:

Developing mechanisms for extreme environments will be one of the biggest challenges for operation on the lunar surface for the Artemis program.

References:

Dust Mitigation Gap Assessment Report, International Space Exploration Coordination Group (ISECG): https://www.globalspaceexploration.org/wordpress/docs/Dust%20Mitigation%20Gap%20Assessment%20Report.pdf

Scope Title:

Freeze-Tolerant Radiators and Heat Exchangers

Scope Description:

Proposals are sought to develop freeze-tolerant radiators and heat exchangers that can freeze and thaw without suffering damage or performance degradation on human-rated spacecraft on the lunar surface. Current ground rules and assumptions (GRAs) for lunar pressurized habitats include 1) Single-phase nontoxic external and internal active thermal control system (ATCS) coolant loops; 2) Heat exchangers and deployable radiators operating at turbulent flow to remove and reject heat; 3) Operate near the lunar South Pole and survive the lunar nights (lasting up to 14 days), where environmental temperatures can drop below the freezing point of heritage and candidate ATCS coolants (e.g., ammonia, water, Freon, HFE 7200) and as low as -213 °C (-351 °F); and 4) Total heat loads varying between 2 and 15 kW, or 6,824 to 51,182 BTU/hr.

Based on these GRAs, the risk of loss of mission (LOM) due to rupturing radiator and heat exchanger coolant tubes because of freeze-thaw cycles is high, and the development of freeze-tolerant radiators and heat exchangers is necessary to reduce this risk and reduce heater power during Artemis missions.

Specifically, developments in radiators and heat exchangers are sought in these areas:

  • Lightweight, corrosion-resistant, freeze-tolerant metallic coolant tubes ranging from 0.127 to 3.81 cm (0.05 to 1.5 in.) inner diameter, 51 to 304 cm (20 to 120 in.) long, and operating under turbulent flow conditions.
  • Lightweight, high-strength, corrosion-resistant, freeze-tolerant nonmetallic flexible coolant tubes ranging from 0.127 to 3.81 cm (0.05 to 1.5 in.) inner diameter, 51 to 304 cm (20 to 120 in.) long, and operating under turbulent flow conditions.
  • Radiators and exchangers with variable thermal resistance that can temporarily eliminate or reduce heat rejection. Examples include, but are not limited to, low-power (less than 1 kW) devices that are capable of suctioning, temporary storing, then refilling the coolant to and from a radiator or heat exchanger and variable emissivity devices or materials (e.g., louvers, thermochromic and electrochromic coatings).

Expected TRL or TRL Range at completion of the Project: 3 to 6

Primary Technology Taxonomy:

  • Level 1 14 Thermal Management Systems
  • Level 2 14.2 Thermal Control Components and Systems

Desired Deliverables of Phase I and Phase II:

  • Analysis
  • Prototype
  • Hardware

Desired Deliverables Description:

Phase I Deliverables: A proof-of-concept or breadboard demonstrating technical feasibility and operability in a laboratory environment, and a report that includes analytical and model simulations in a relevant environment and heat loads to answer critical questions focused on reducing the risk of freezing radiators or heat exchangers. In addition, the report shall include recommendations for brassboard or prototype development during Phase II.

Phase II Deliverables: Delivery of a brassboard or prototype with a goal of achieving TRL 5 or 6, and laboratory testing demonstrating operability over the range of expected environmental conditions and heat loads. A report shall be written that includes functional, performance, analytical and test results; an evaluation of the technology’s maturity level (i.e., TRL); risk of proceeding with the development; and a well-developed flight demonstration and infusion plan.

State of the Art and Critical Gaps:

SOA ATCS on human-rated spacecraft like the Apollo Service Module (SM) and International Space Station (ISS) used mechanically pumped, single-phase coolant to collect, transport, and reject heat, and the components that are most vulnerable to rupturing due to freeze-thaw cycles are the radiators and heat exchangers because they are exposed to the environment. The Apollo SM radiators were designed to partially stagnate, and only the coolant tubes, not the manifolds, in the ISS radiators were designed to withstand the high-pressure transients induced by freeze-thaw cycles. This requires small inner diameters (0.18 cm or 0.07 in.) metallic (Inconel or stainless steel) coolant tubes with thick walls (0.32 cm or 0.125 in.) outer diameters), optimal spacing between tubes, and turbulent flow. Bigger inner diameters may be required for future radiators to enhance hydraulic and thermal performance, but increasing the outer diameter to enable freeze tolerance will increase the mass and counter the thermal performance. Similarly, the Apollo SM and ISS heat exchangers used metallic coolant tubes with large inner diameters (2.5 cm or 1 in.) and thin walls to achieve high heat transfer coefficients, but increasing the outer diameter for freeze tolerance will impact thermal performance. Inconel and stainless steel coolant tubes were used in these systems for their higher thermal conductivity, corrosion resistance, and strength for micrometeoroid and orbital debris (MMOD) protection but consequently limit freeze protection. Therefore, nonmetallic flexible coolant tubes that are corrosion resistant with high strength are also desired to enable freeze tolerance while meeting thermal and hydraulic requirements. There are no SoA ATCSs that can vary the thermal resistance of a radiator or heat exchanger to temporarily eliminate or reduce heat rejection, but this capability is desired to enable freeze tolerance.

Relevance / Science Traceability:

Pressurized habitats or rovers stationed near the lunar South Pole for future Artemis missions will be exposed to extremely cold environmental temperatures as low as -213 °C (-351 °F) during lunar nights (up to 14 days), which are below the freezing point of heritage or candidate ATCS coolants (e.g., ammonia, water, Freon, HFE 7200). Preliminary analysis results of the conceptual lunar Surface Habitat ATCS architecture showed significant heater power (up to 4 kW or 13,648 BTU/hr) is required to prevent the coolant from freezing and maintain operations. Thus, freeze-tolerant radiators and heat exchangers are needed to reduce heater power, avoid rupturing the coolant tubes, and reduce the risk of loss of mission (LOM).

References:

  • Babiak, S., Evans, B., Naville, D., Schunk, G., "Conceptual Thermal Control System Design for a Lunar Surface Habitat," Thermal Fluids & Analysis Workshop (TFAWS), August 24-26, 2021.
  • Binns, D., Hager, P., "Thermal design challenges for lunar ISRU payloads," 50th International Conference on Environmental Systems (ICES), July 12-15, 2021. 
  • Samonski, F.H., Jr., Tucker, E.M., “Apollo experience report: Command and service module environmental control system,” NASA Technical Note (TN) D-6718, March 1, 1972.
  • International Space Station (ISS) Active Thermal Control System (ATCS) Overview. https://www.nasa.gov/pdf/473486main_iss_atcs_overview.pdf
     

Scope Title:

Freeze-Tolerant Water Containers

Scope Description:

Proposals are sought to develop flexible, freeze-tolerant water containers that can survive the extremely cold environmental temperatures at unpressurized and pressurized conditions on the lunar surface. Water recovered from in situ devices may be contained in bags that are subjected to an unpressurized environment on the lunar surface and will be exposed to temperatures from -213 to 127 °C (-351 to 260 °F). The water containers may be brought inside a pressurized habitat or rover at atmospheric conditions, then processed and treated to produce potable water for contingency use. Therefore, the containers need to withstand pressure and thermal cycles, prevent the water from freezing while on the lunar surface, and be flexible so they can shrink when empty to reduce volume and expand when full; full to empty container ratio >100:1 and maximum water mass of 250 kg (555 lbm).

Expected TRL or TRL Range at completion of the Project: 3 to 6

Primary Technology Taxonomy:

  • Level 1 07 Exploration Destination Systems
  • Level 2 07.2 Mission Infrastructure, Sustainability, and Supportability

Desired Deliverables of Phase I and Phase II:

  • Research
  • Analysis
  • Prototype
  • Hardware

Desired Deliverables Description:

Phase I Deliverables: A proof-of-concept or breadboard demonstrating technical feasibility and operability in a laboratory environment, and a report that includes analytical and model simulations in a relevant environment. In addition, the report shall include recommendations for brassboard or prototype development during Phase II.

Phase II Deliverables: Delivery of a brassboard or prototype with a goal of achieving TRL 5 or 6, and laboratory testing demonstrating operability over the range of expected environmental conditions and water volume. A report shall be written that includes functional, performance, and analytical test results; an evaluation of the technology’s maturity level (i.e., TRL); risk of proceeding with the development; and a well-developed flight demonstration and infusion plan.

State of the Art and Critical Gaps:

SOA contingency water containers (CWCs) used on the space shuttle and the International Space Station (ISS) were designed to be stored in an atmospheric environment and were not rated for the vacuum conditions, pressure cycles, and extreme environmental temperatures expected at the lunar South Pole. Current containers have a reasonable water mass to empty volume ratio of 25:1, and the internal space on the ISS and space shuttle constrained the maximum water mass to 45 kg (99 lbm). Critical gaps are the flexible, freeze-tolerant water containers for unpressurized and pressurized conditions at temperatures ranging from -213 to 127 °C (-351 to 260 °F); full to empty container ratio >100:1; and maximum water mass of 250 kg (555 lbm).

Relevance / Science Traceability:

NASA is developing in situ water retrieval technologies to excavate or drill into regolith-based water deposits from various regions on the lunar surface, then transport, store, and process into potable water, propellant, fuel cell reactants, and life support consumables for Artemis missions.

References:

  1. Carter, Layne et al., “Status of ISS Water Management and Recovery,” 49th International Conference on Environmental Systems (ICES), July 7-11, 2019.
  2. Tobias, Barry et al., “International Space Station Water Balance Operations,” 41st International Conference on Environmental Systems (ICES), 2011.
  3. Li et al., “Direct evidence of surface exposed water ice in the lunar polar regions,” PNAS, 115, 2018, pp. 8907-8912, https://www.pnas.org/content/pnas/115/36/8907.full.pdf
  4. Colaprete, A., Schultz, P., Heldmann, J., Wooden, D., Shirley, M., Ennico, K., and Goldstein, D., “Detection of water in the LCROSS ejecta plume,” Science, 330 2010, pp. 463-468.
  5. Schultz, P.H., Hermalyn, B., Colaprete, A., Ennico, K., Shirley, M., Marshall, W.S., “The LCROSS cratering experiment,” Science, 330, 2010, pp. 468-472.

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