Linda Del Castillo

Extreme environment capable, modular and scalable power processing unit for solar electric propulsion

This paper is to present a concept of a modular and scalable High Temperature Boost (HTB) Power Processing Unit (PPU) capable of operating at temperatures beyond the standard military temperature range. The various extreme environments technologies are also described as the fundamental technology path to this concept. The proposed HTB PPU is intended for power processing in the area of space solar electric propulsion, where reduction of in-space mass and volume are desired, and sometimes even critical, to achieve the goals of future space flight missions. The concept of the HTB PPU can also be applied to other extreme environment applications, such as geothermal and petroleum deep-well drilling, where higher temperature operation is required.

Robust, rework-able thermal electronic packaging: Applications in high power TR modules for space

The higher output power densities required of modern radar architectures, such as the proposed DESDynI [Deformation, Ecosystem Structure, and Dynamics of Ice] SAR [Synthetic Aperture Radar] Instrument (or DSI) require increasingly dense high power electronics. To enable these higher power densities, while maintaining or even improving hardware reliability, requires improvements in integrating advanced thermal packaging technologies into radar transmit/receive (TR) modules. New materials and techniques have been studied and are now being implemented side-by-side with more standard technology typically used in flight hardware.

Insulation Materials Development for Potential Venus Surface Missions

Any potential mission that operates on the surface of Venus requires a unique thermal protection system unlike those found on traditional spacecraft. This paper describes the results of thermal and mechanical testing of insulation materials that may be used to protect a conceptual Lander for Venus surface operations. The thermal control strategy for a conceptual Venus Lander does not rely upon developing new technology; it utilizes the efforts pioneered by the Soviet Venera missions. A new investigation of insulation materials is warranted because many of the practical design and implementation details of the Venera thermal system are unavailable and the present generation of thermal expertise lacks specific knowledge to claim heritage with validity. Thermal conductivity testing of three different classes of insulation materials was made at earth-like and Venus-like conditions. The material classes were porous silica, TiO2 filled aerogel, and silica fiber blankets. Earthlike test conditions were carried out in an oven at ambient pressure air at 470C. Venus-like test conditions were performed in a heated pressure vessel capable of providing a CO2 atmosphere up to 470C and 92 bar pressure. In all material classes, the thermal conductivity under Venus-like conditions increased significantly over the earth-like values. Data from these tests can be used in thermal design to determine the required insulation thickness to protect the Lander for the mission operating life. Mechanical testing of the insulation materials was performed because the atmospheric entry and landing of the vehicle can generate significant deceleration forces. Insulation bonding techniques have been developed for attaching insulation to the exterior surface of a Lander pressure vessel. Data on shear and tensile loading capacity have been collected for various adhesives and bonding techniques. Furthermore, insulation restraint using an exterior skin of stainless steel foil has been developed to enable the insulation material to handle up to 150g’s of deceleration forces. Data from these tests can be used in the mechanical design of the insulation system to ensure it would survive the high body forces of atmospheric entry and landing.

Flexible electronic assemblies for space applications

This describes the development and evaluation of advanced technologies for the integration of electronic devices within membrane polymers. Specifically, investigators thinned silicon die, electrically connecting them with circuits on flexible (liquid crystal polymer (LCP) and polyimide (PI)) circuits, using gold thermo-compression flip chip bonding, and embedding them within the material. The influence of temperature and flexure on the electrical behavior of active embedded assemblies was evaluated. In addition, the long-term thermal cycle resistance of the passive daisy chain assemblies was determined within the Mil-Std (-55° to +125°C), extreme low #1 (-125° to +85°C), and extreme low #2 (-125° to +125°C) temperature ranges. The results of these evaluations will be discussed, along with the application of this technology for future NASA missions.

High Temperature Boost (HTB) Anode Power Supply for a modular and scalable power processing unit

A concept of a modular and scalable 10kW to 80kW High Temperature Boost (HTB) Power Processing Unit (PPU) capable of operating at temperatures beyond the standard military temperature range was proposed for solar electric in-space propulsion. Within the PPU, the Anode Power Supply (APS) module is a 10kW modular power stage and is the key to the HTB PPU. This paper is to present the design, development, fabrication, testing and thermal demonstration of the 10kW HTB APS. The system architecture and the paradigm shift of the HTB PPU is also to be described. In addition, the extreme environments electronic and packaging technologies are addressed as the fundamental technology path. The HTB PPU is intended for power processing in the area of space solar electric propulsion, where reduction of inspace mass and volume are desired, and sometimes even critical, to achieve the goals of future space flight missions. The concept of the HTB PPU can also be applied to other extreme environment applications, such as geothermal and petroleum deep-well drilling, where higher temperature operation is required.

Advanced housing materials for extreme space applications

Thermal stresses have a significant impact on the mechanical integrity and performance of RF hybrid circuits. To minimize this impact, a series of spray deposited Si-Al alloys were evaluated for use in electronic housing applications. Current housings for RF modules in space-based applications are generally made from either Kovar or 6061 Al. Although Kovar has a coefficient of thermal expansion (CTE) close to those of GaAs and Si, it also possesses a 10x reduction in thermal conductivity and a 3x increase in density compared with those of 6061 Al. Although it provides improved heat dissipation properties, 6061 Al has a CTE that is nearly 4x that of Kovar. The controlled expansion (CE) spray deposited Si-Al housing materials discussed herein combine a CTE approaching that of Kovar, with a thermal conductivity approaching that of 6061 Al, and a density that is less than that of both materials. The mechanical behavior of select Si-Al alloys was evaluated along with the application of these materials for direct attachment of active devices. Assemblies were thermal cycled from −55 to +125°C.1 2

Advanced embedded active assemblies for extreme space applications

This work describes the development and evaluation of advanced technologies for the integration of electronic die within membrane polymers. Specifically, investigators thinned silicon die, electrically connecting them with circuits on flexible liquid crystal polymer (LCP), using gold thermo-compression flip chip bonding, and embedding them within the material. Daisy chain LCP assemblies were thermal cycled from −135 to +85°C (Mars surface conditions for motor control electronics). The LCP assembly method was further utilized to embed an operational amplifier designed for operation within the Mars surface ambient. The embedded op-amp assembly was evaluated with respect to the influence of temperature on the operational characteristics of the device. Applications for this technology range from multifunctional, large area, flexible membrane structures to small-scale, flexible circuits that can be fit into tight spaces for flex to fit applications.

Advanced thermal packaging for high power TR modules

The higher output power densities required of modern radar architectures, such as the proposed DESDynI [Deformation, Ecosystem Structure, and Dynamics of Ice] SAR [Synthetic Aperture Radar] Instrument (or DSI) require increasingly dense high power electronics. To enable these higher power densities, while maintaining or even improving hardware reliability, requires advances in integrating advanced thermal packaging technologies into radar transmit/receive (TR) modules. New materials and techniques have been studied and compared to standard technologies.

Thermal Control Technology Developments for a Venus Lander

The thermal control system for a Venus Lander is critical to mission success and the harsh operating environment presents significant thermal design and implementation challenges. A successful thermal architecture draws heavily from previous missions to the Venus surface such as Pioneer Venus and the Soviet Venera Landers. Future Venus missions will require more advanced thermal control strategies to allow greater science return than previous missions and will need to operate for more than one or two hours as previous missions have done. This paper describes a Venus Lander thermal architecture including the technology development of a phase change material system for absorbing the heat generated within the Lander itself and an insulation system for resisting the heat penetrating the Lander from the Venus environment. The phase change energy storage system uses lithium nitrate that can absorb twice the amount of energy per unit mass in comparison to paraffin based systems. The insulation system uses a poro...

High temperature anode power supply parts and packaging reliability and survivability

The power processing unit (PPU) of a solar electrical propulsion system for in-space propulsion is developed as a high power, temperature, and efficiency, modular, high specific impulse, and non-isolated converter topology unit for future deep space and manned missions. Overall, the High Temperature Boost (HTB) PPU has 87% improvement in PPU specific power/mass and 38% improvement in-space solar electric system mass saving. The objectives of this Phase 1 study are to develop a High Temperature Anode Power Supply 10kW Prototype module with new extreme environment component and packaging technology and determine the component reliability and packaging survivability for at least 50 cycles in the temperature range of -55°C to +160°C. After cycling, the functionality is tested at room temperature and elevated temperature (base plate at 100°C). Selection of high temperature components and advanced packaging techniques enables operation at a higher base plate temperature of 100°C. SiC MOSFETS and diodes were chosen as well as high temperature capacitors designed to operate at 1kV and 2μF at 150°C.