Venus Surface Missions Research Articles

Pt/HTCC Alumina based Electronic Packaging System and Integration Processes for High Temperature Harsh Environment Applications

Electronic devices capable of operation at 500°C are required for long term Venus surface missions, as well as for in situ monitoring and control of next generation aeronautical engines. High temperature sensors and electronics can also find many applications in military, and energy and automobile industries. Various silicon carbide (SiC) sensors and electronic devices have been developed for operation at 500 °C, and a compatible packaging system is needed for long term test and deployment of these high temperature devices. High temperature co-fired ceramics (HTCC) alumina with platinum (Pt) conductor was proposed for high temperature electronic packaging. A prototype Pt/HTCC alumina packaging system including chip-level package and circuit board has been briefly reported previously for long-term electrical testing of SiC integrated circuits at 500 °C, and brief testing at much higher temperatures. HTCC alumina is an excellent dielectric material with acceptable dielectric constant and low dielectric loss over wide temperature and frequency ranges. Pt is chemically noble and can be co-fired with HTCC alumina in air ambient producing a viable electronic packaging material system for high temperature applications. This paper presents a more detailed description of this packaging system including prototype low power packages and circuit boards based on HTCC alumina and Pt metallization for 500°C and other harsh environment applications. The key technical considerations for chip-level packaging and circuit board assembly, including materials and processes for 500 °C durable wire-bonding and SiC die attach, and integration of multi-chip circuit boards, are presented. Experimental test results of this packaging approach applied to SiC integrated circuits at 500 °C and 700°C are discussed as well.

High Temperature Batteries for Venus Surface Missions

In-situ exploration of Venus is seriously hampered by its severe environment, which is benign (28oC) at an altitude of 55 km, but rapidly becomes hostile, with increasing temperature and CO2 pressure at lower altitudes, eventually reaching ~465°C and 90 bars at the surface.1 These challenging conditions have limited the previous Venus surface missions, e.g., the Russian Venera series and Vega-2 Landers,2 to barely two hours after deployment with lithium-primary batteries, despite the use of considerable insulation, phase-change materials, and similar heat sinks to isolate batteries and avionics from high surface temperatures. The recent decadal survey, ‘Vision and Voyages for Planetary Science in the Decade as well as the more recent Venus Exploration and Analysis Group (VEXAG) study3 emphasized the need to gather basic information on the crust, mantle, core, atmosphere/exosphere, and bulk composition of Venus, to understand the evolutionary paths of Venus in relation to Earth and recommended long-duration landers and probes for future missions.In order to enable extended surface missions on Venus, e.g., landers, probes and seismometers, NASA has initiated the development of high temperature electronics and power technologies, under its ‘Hot Operating Temperature Technology’ (HOTTech) program. Under this program, we have been developing advanced primary batteries resilient to the hostile conditions on the Venus surface and operational for several days with high specific energy (>100 Wh/kg) and energy density (>150 Wh/l). Here, we will describe the development of high temperature batteries based on lithium alloy (e.g., Li-Al) anodes, molten salt electrolytes containing binary/ternary mixtures of alkali metal halides, cathodes consisting of transition metal sulfides, and designs similar to the aerospace thermal batteries.4 With FeS cathode and appropriate changes in the electrolyte, binder and active material ratios, we have demonstrated the operation of the high temperature battery in prototype cells for 30 days in primary mode, and >150 days in rechargeable mode at 475oC. Further, with suitable thin coatings of inorganic compounds, e.g., Al2O3, AlF3 and AlBO3 on the cathode particles, the utilization of the cathode, and hence the operational life of the cells have been improved by another 50%.AcknowledgementsThe work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the NASA’s HOTTech project. The information in this document is pre-decisional and is provided for planning and discussion only.References Basilevsky, J. W. Head, "The surface of Venus". Rep. Prog. Phys. 66, 1699 (2003).Gilmore, et al., “Venus Surface Composition Constrained by Observation and Experiment”, Space Sci. Rev. 212, 1511–1540 (2017); doi:10.1007/s11214-017-0370-8.A. Bullock, et al., “A Venus Flagship Mission: Report of the Venus Science and Technology Definition Team," 40th Lunar and Planetary Science Conference (Lunar and Planetary Science XL), The Woodlands, TX, March 23-27 (2009).E. Glass, J.P. Jones, A. V. Shevade, D. Bhakta, E. Raub, R. Sim, R. V. Bugga, “High temperature primary battery for Venus surface missions”, J. Power Sources. 449, 227492 (2020). doi:10.1016/j.jpowsour.2019.227492.

Power systems for Venus surface missions: A review

Future missions to Venus will require electrical power, but providing power systems that work in the high temperature environment of the surface of Venus is difficult. Power system choices include solar power from photovoltaic arrays, batteries, radioisotope power systems, and wind. The current state of power technology for operation on the Venus surface sources is surveyed and assessed.

High temperature primary battery for Venus surface missions

The hostile environment of high temperature and CO2 pressure has limited previous Venus surface mission durations to less than 2 h giving only a glimpse of the Venus surface, despite the use of considerable insulation, phase-change materials, and similar heat sinks to isolate the payload and avionics from high surface temperatures. NASA has initiated studies to develop new power technologies that can tolerate the high Venus surface temperature of 465 °C and pressure of 92 bar, and operate for future long-duration Venus landers and probes. Such in-situ investigations are crucial to gather basic information on the crust, mantle, core, and bulk composition of Venus for understanding the evolutionary paths of Venus in relation to Earth. In this paper, we describe the development of high temperature primary batteries based on lithium alloy anodes, transition metal sulfide cathodes, and molten salt electrolytes. Among the various cathode materials examined for thermal stability and for electrochemical activity, FeS has emerged as the most suitable cathode. With optimized cell components, cell design, and operational parameters, laboratory test cells were fabricated, which demonstrated continuous operation of ~26 days at 475 °C. These batteries will enable new long-duration surface missions for detailed surface exploration of Venus.

High Temperature Primary Batteries for Venus Surface Missions

Because of the hostile environments of high temperature and pressure, previous Venus probes survived for just two hours. Future Venus surface missions need to survive for much longer durations of several days, in order to return useful science. NASA’s LISSE lander concept has been proposed to operate on the surface of Venus for 60 days. Operating at a temperature of 465 °C and an ambient (CO2) pressure of 92 bar for up to 60 days is a significant challenge and requires new battery chemistries and cell designs. With this objective, we have been investigating high temperature lithium primary batteries with lithium alloy anodes, transition metal sulfide cathodes and molten salt electrolytes. Various cathode materials were screened for thermal stability at high temperature, in contact with the molten salt. Among these cathodes, FeS exhibited the highest stability and laboratory cells were fabricated and tested at 475 OC at various discharge rates to demonstrate long-term operational capability. Initial single cell designs have been shown to be operational for up to 15 days, with the cathode utilization decreasing at the low rates of discharge. Factors determining selection of cathode material, electrolyte composition, separator, etc. will be discussed, along with plans to achieve a full 60 day discharge.

Operational Testing of 4H-SiC JFET ICs for 60 Days Directly Exposed to Venus Surface Atmospheric Conditions

Prolonged Venus surface missions (lasting months instead of hours) have proven infeasible to date in the absence of a complete suite of electronics able to function for such durations without protection from the planet’s extreme conditions of ~460°C, ~9.3 MPa (~92 Earth atmospheres) chemically reactive environment. Here, we report testing data from a successful two-month (60-day) operational demonstration of two 175-transistor 4H-SiC junction field effect transistor (JFET) semiconductor integrated circuits directly exposed (no cooling and no protective chip packaging) to a high-fidelity physical and chemical reproduction of Venus surface atmospheric conditions in a test chamber. These results extend the longest reported duration of electronics operation in Venus surface atmospheric conditions almost threefold and were accomplished using prototype SiC JFET chips of more than sevenfold increased complexity. The demonstrated advancement marks a significant step toward realization of electronics with sufficient complexity and durability for implementing robotic landers capable of returning months of scientific data from the surface of Venus.

Ground tests with prototype of CeBr3 active gamma ray spectrometer proposed for future venus surface missions

The results of a series of ground tests with a prototype of an active gamma-ray spectrometer based on a new generation of scintillation crystal (CeBr3) are presented together with a consideration to its applicability to future Venus landing missions. We evaluated the instrument's capability to distinguish the subsurface elemental composition of primary rock forming elements such as O, Na, Mg, Al, Si, K and Fe. Our study uses heritage from previous ground and field tests and applies to the analysis of gamma lines from activation reaction products generated by a pulsed neutron generator. We have estimated that the expected accuracies achieved in this approach could be as high as 1–10% for the particular chemical element being studied.

Combustion-based power source for Venus surface missions

The National Research Council has identified in situ exploration of Venus as an important mission for the coming decade of NASA's exploration of our solar system (Squyers, 2013 [1]). Heavy cloud cover makes the use of solar photovoltaics extremely problematic for power generation for Venus surface missions. In this paper, we propose a class of planetary exploration missions (for use on Venus and elsewhere) in solar-deprived situations where photovoltaics cannot be used, batteries do not provide sufficient specific energy and mission duration, and nuclear systems may be too costly or complex to justify or simply unavailable. Metal-fueled, combustion-based powerplants have been demonstrated for application in the terrestrial undersea environment. Modified or extended versions of the undersea-based systems may be appropriate for these sunless missions. We describe systems carrying lithium fuel and sulfur-hexafluoride oxidizer that have the potential for many days of operation in the sunless craters of the moon. On Venus a system level specific energy of 240 to 370 We-hr/kg should be possible if the oxidizer is brought from earth. By using either lithium or a magnesium-based alloy fuel, it may be possible to operate a similar system with CO2 derived directly from the Venus atmosphere, thus providing an estimated system specific energy of 1100 We+PV-hr/kg (the subscript refers to both electrical and mechanical power), thereby providing mission durations that enable useful scientific investigation. The results of an analysis performed by the NASA Glenn COMPASS team describe a mission operating at 2.3kWe+PV for 5 days (120h), with less than 260kg power/energy system mass total. This lander would be of a size and cost suitable for a New Frontiers class of mission.

Batteries for Venus Surface Operation

The surface of Venus is one of the most challenging environments for the operation of spacecraft. With a surface temperature of around 460°C and a surface atmospheric pressure of 92 bar of carbon dioxide, conventional power technologies are not usable. A number of battery technologies can be adapted to the high-temperature environment. A new primary-battery technology for Venus surface operation is proposed, which uses the in situ carbon dioxide atmosphere as a reactant. This technology would allow high-specific-energy density and, thus, extend the operating time of a battery-powered Venus surface mission.