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NASA Thermal Management Systems Technology Area Roadmap

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NASA Thermal Management Systems Technology Area Roadmap National Aeronautics and Space Administration DRAFT TheRmAl mAnAgemenT SystemS RoadmAp Technology Area 14 Scott A. Hill, Chair Christopher Kostyk Brian Motil William Notardonato Steven Rickman Theodore Swanson November • 2010 DRAFT This page is intentionally left blank DRAFT Table of Contents Foreword Executive Summary TA14-1 1. General Overview TA14-5 1.1. Technical Approach TA14-5 1.2. Benefits TA14-6 1.3. Applicability/Traceability to NASA Strategic Goals, AMPM, DRMs, DRAs TA14-6 1.4. Top Technical Challenges TA14-6 2. Detailed Portfolio Discussion TA14-7 2.1. Cryogenic Systems TA14-8 2.1.1. Passive Thermal Control TA14-8 2.1.2. Active Thermal Control TA14-10 2.1.3. System Integration TA14-12 2.2. Thermal Control Systems (Near Room Temperature) TA14-13 2.2.1. Heat Acquisition TA14-13 2.2.2. Heat Transfer TA14-14 2.2.3. Heat Rejection and Energy Storage TA14-16 2.3. Thermal Protection Systems (TPS) TA14-19 2.3.1. Ascent/Entry TPS TA14-19 2.3.2. Plume Shielding (Convective and Radiative) TA14-22 2.3.3. Sensor Systems and Measurement Technologies TA14-23 3. Interdependency with Other Technology Areas TA14-23 4. Possible Benefits to Other National Needs TA14-23 Acronyms TA14-25 Acknowledgements TA14-25 DRAFT Foreword NASA’s integrated technology roadmap, including both technology pull and technology push strategies, considers a wide range of pathways to advance the nation’s current capabilities. The present state of this effort is documented in NASA’s DRAFT Space Technology Roadmap, an integrated set of fourteen technology area roadmaps, recommending the overall technology investment strategy and prioritization of NASA’s space technology activities. This document presents the DRAFT Technology Area 14 input: Thermal Management Systems. NASA developed this DRAFT Space Technology Roadmap for use by the National Research Council (NRC) as an initial point of departure. Through an open process of community engagement, the NRC will gather input, integrate it within the Space Technology Roadmap and provide NASA with recommendations on potential future technology investments. Because it is difficult to predict the wide range of future advances possible in these areas, NASA plans updates to its integrated technology roadmap on a regular basis. DRAFT exeCuTive Summary perature radiators for pre-cooling gas, two phase The Thermal Management Systems Technology flow radiators that serve as passive liquefiers) op- Area (TA) cross-cuts and is an enabler for most timized for the given environment is important. other system-level TAs. Technology development Thermal control systems maintain all vehicle in the Thermal Management Systems TA is cen- surfaces and components within an appropriate tered on the development of systems with reduced temperature range throughout the many mission mass that are capable of handling high heat loads phases despite changing heat loads and thermal with fine temperature control. Technologies with- environments. Effective thermal control systems in the Thermal Management Systems TA are or- provide three basic functions to the vehicle/sys- ganized within the three sub-areas of Cryogenic tem design: heat acquisition, heat transport, and Systems, Thermal Control Systems, and Thermal heat rejection while being mindful of the opera- Protection Systems. tional environment and spacecraft system. Tech- Cryogenic systems require special care for nu- nology advances for heat acquisition devices are merous reasons. The primary reason is the large centered on high thermal conductivity materials range of temperatures to which the cryogenic sys- with a high strength-to-mass ratio and increasing tem is subjected. Secondarily, the maintenance the specific energy density of the systems (i.e. high and production of cryogenic propellants requires thermal performance and low mass). Once waste large amounts of power which can be a driver for heat has been acquired, it must be transported to some systems of the spacecraft. Due to the Carnot a heat exchanger or radiator for reuse or ultimate penalty, 1 watt of heat at 20K most likely requires rejection to space. The specific technology em- 150-200 W at 300K to maintain it. This dictates ployed for transport is dependent on the temper- the need for very efficient systems so power re- ature and/or heat flux and thus a wide variety of quirements are not increased. Without effective equipment and techniques can be used. The de- insulation, large flow rates of gases will be vented velopment of single loop architectures could save from the tank. Fortunately, the high vacuum and significant weight, reduce system complexity, and low temperatures of the space environment sim- increase reliability of the thermal design of crewed plifies the thermal control of cryogens in some as- systems. An additional heat transport technology pects. requiring development is in the area of heat pipes. The performance and efficiency of cryogenic Loop Heat Pipes (LHP) and Capillary Pumped systems will have to significantly increase in order Loops (CPL) provide significant heat transport to enable the missions being considered over the over long distances with low temperature drop. next twenty-years. New materials capable of as- Thermal energy can also be stored for later use or cent venting without performance loss or physical rejection into a more favorable environment, thus damage and self-healing Multi Layer Insulation significantly reducing the thermal control system (MLI) or other insulation concepts must be devel- mass by smoothing out the effects of peak and oped and demonstrated. Insulation systems that minimum thermal loads as well as the extreme en- are built into cryogenic tank structure and the use vironments. A method of coping with the peri- of low-conductive composite materials will offer odic long-duration extremely-cold environments reductions in the combined structure and insu- that will occur on planets that do not have an at- lation mass fraction while significantly reducing mosphere is to devise a method of ameliorating cryogen boil-off losses. In addition, techniques for the thermal environment which can significant- tailoring regolith properties to increase the ther- ly reduce the required mass of the thermal system mal performance as an insulation system will have design. to be developed as a mission enabler for space- Thermal protection consists of materials and craft operating on other planetary or near-Earth systems designed to protect spacecraft from ex- objects. The development of cryocoolers and oth- treme high temperatures and heating during all er active cryogenic fluid management systems for mission phases. Reusable thermal protection sys- thermal control of cryogenic propellants in space tems (TPS) are also key technologies for hyper- is a high priority and mission enabler for cryogen- sonic cruise vehicles. Despite the current trend to ic fuel depots and long duration missions outside move away from systems requiring this kind of of low Earth orbit (LEO). Overall system goals TPS there is a national need to not only maintain for these systems are for reduced vibration, lower this technology and its manufacturing, but also to mass, and lower specific power. Also, development advance the state of the art (SOA) in several ar- of large capacity liquefaction cycles (e.g., low tem- eas, particularly maintainability, system size, mass, DRAFT TA14-1 and system robustness. Additional technology de- ments would impact almost every figure of merit velopment is needed to increase the robustness (e.g., mass, reliability, performance, etc.). Some and reduce the maintenance required for reus- advancements in TPS technology fall under the able TPS. In the area of hot structures, high tem- category of “game changing,” while others would perature heat pipes hold the promise of providing represent significant advancements in technolo- high heat flux capability far in excess (5-10x) of gy currently available. Implementation of a sin- high temperature materials. Large inflatable/flex- gle-loop thermal control system is a significant ible/deployable heat shields enable the consider- system simplification thereby increasing the sys- ation of an entirely new class of missions – flexi- tem reliability while decreasing integration efforts ble TPS is enabling for deployable entry systems. for the system. Finally, 20 K cryocoolers capable For many exploration missions rigid ablative ma- of 20 W of refrigeration would offer a significant terials are an enabling technology and are need- mass savings in cryogen storage through a signifi- ed for dual- heat pulse reentries and for very high cant reduction of cryogen boil off and would be a velocity entries. Advances are required to signifi- mission enabler for long term cryogen storage for cantly lower the areal mass of TPS concepts, dem- long duration missions. onstrate extreme environment capability, high re- In summary, the Thermal Management Sys- liability, improved manufacturing consistency and tems TA cross-cuts and is an enabler for most oth- lower cost, and dual-heat pulse capability. From er system-level TA’s with specific interdependen- an analytical perspective, recent efforts have re- cies identified with ten of the remaining fourteen vived ablation analysis capabilities but these need TA’s. The primary benefits from investment in the to be further developed to include development technologies outlined for cryogenic systems, ther- of material response/flow field coupling codes, in- mal control systems, and thermal protection sys- tegration of
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