Exploration & Observational Systems

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Survivable Systems for Extreme Environments

A number of planned or potential planetary science missions have elements that must survive and operate in extreme environments. Environments are defined here as “extreme” if they involve exposure to extremes in pressures, temperatures, ionizing radiation, chemical and/or physical corrosion, and the impact of hypervelocity particles. In addition, certain missions would induce extremes in heat flux or deceleration, leading to their inclusion as missions in need of technologies for extreme environments.

The environments for solar system in situ exploration missions cover extremes of temperature, pressure, and radiation that far exceed the operational limits of space-rated electronics, electronic packaging, thermal control, sensors, actuators, power sources, and batteries. All space missions recommended by the NRC’s Decadal Survey on Solar System exploration require operations in extreme environments of very high and very low temperatures, high and low pressures, corrosive atmospheres, or high radiation.

Current Challenges

Future JPL missions are expected to require operations in environmental extremes that are beyond current technologies. Mechanical and electronic systems need to be developed to survive in these extreme environments.

Extreme Temperatures

The heat shield left behind after MER successfully descended through the Martian atmosphere.

The environments for solar system in situ exploration missions cover extremes of temperature, pressure and radiation that far exceed the operational limits of space-rated electronics, electronic packaging, thermal control, sensors, actuators, power sources and batteries.

In one extreme, candidate Venus lander missions would need to survive at 460 degrees Celsius and 90-bar pressures and have to pass through corrosive sulfuric acid clouds during descent. The current state of the art technology would limit the duration of Venus surface exploration to only 1–2 hours.

In the other extreme, Titan, Europa, asteroids, comets, and Mars missions would require operations under extremely cold temperatures (–180 to –120 degrees Celsius).

For potential missions to comets that are close to the Sun, high-velocity impacts are a real concern, with impact velocities reaching greater than 500 kilometers/second (310 miles per second) at 4 solar radii (perihelion for a solar probe mission).

High-radiation environments

High levels of radiation present yet another concern. Missions to Europa present a challenge of surviving mega rad radiation levels behind typical shielding thicknesses. In fact, all space missions recommended by the National Research Council (NRC)’s Decadal Survey on Solar System Exploration require operations in extreme environments of very high and very low temperatures, high and low pressures, corrosive atmospheres or high radiation.

Survival in these environments requires not only testing and modeling of the effects but also systems solutions, including fault tolerance, thermal management, systems integration, functional redundancy, etc., if JPL is to be successful. Investments in technologies for developing these systems and for operations and survivability in extreme environments would enable JPL to successfully develop future NASA missions, strengthen JPL’s capabilities in systems design for survivability in extreme environments, and open the way to new, superior, and more reliable future mission architectures.

Long Life

Survivable systems need to have extensive reliability for extended lifetimes. Electronics are generally not designed to be functional for more than 10 years unless specially fabricated. Long life systems ultimately need a 20-year (or more) lifetime, and would be critical for extended lunar stay missions, deep and interstellar space missions and some Earth-orbiting missions.

Dust Lastly, an important consideration when building survivable systems is the reliability, extended functionality and operation of systems in lunar dust, such as in lunar surface missions, as well as for astronauts. Hypervelocity impact environments Impacts by meteoroids or Earth space debris at velocities of 20–40 kilometers/second short term, >500 kilometers/second long term (solar probe). Current state of the art limits the duration of Venus surface exploration to only 1–2 hours. Thermal Cycling Because survivable systems operate in wide temperature ranges, such as –extreme cycling between -128 and +20°C, as well as lunar cycling from -230 to +130°C, factors such as electronics performance, fatigue issues, and material fabrication are crucial in the development of these systems.
	An animation showing Martian dust concentrations. Like lunar dust, dust storms on Mars can cause problems for many spacecraft subsystems.

Survivable systems need to achieve maximum reliability to operate in micro- meteoroid environments as well as encountering other orbital debris in transit.

Mission Applications

Low Temperature and Temperature Cycling Resistant Electronics (TCRE) and Packaging Technologies

This task develops electronic components and electronics packaging technology that would be capable of operating in the ambient temperature of Mars without thermal control. Mars surface temperature changes from ~120° C at night to 20° C during the day. Robotics systems, such as Mars Exploration Rovers (MER), employ a WEB to shield their electronic subsystems from the temperature changes of the environment. Unfortunately, WEB-based electronics require point-to-point wiring harness and a complex mesh of interconnects between the WEB and unshielded loads (motors, actuators and sensors). An alternative approach is to deploy 'plug-and-play' modules consisting of electronics integrated with motors and sensors. These modules, able to operate in a Mars environment, would be located at the extremities of the robotics system and would be connected with a standard communication bus interface that would significantly reduce the number and simplify the interconnects and cablings for motors and actuators.

The TCRE electronic task has developed a rad-tolerant, wide-temperature, quad operational amplifier for the Mars environment. We have undertaken this effort because commercially available operational amplifiers failed to provide performance needed for sense and control of analog signals in the motor-drive electronics. JPL has developed the design rules by examining the reliability of individual transistors in the SOI CMOS technology at low temperatures and modeled the life of the transistors as a function of its geometric parameters (transistor channel width and length). An amplifier developed on this program is now baselined for use in the MSL rover.

The TCRE packaging develops a reliable, low-temperature packaging technology that can survive for an extended mission in a Mars environment. More specifically, this electronic packaging technology must survive thermal cycling from ~120° C to 85° C for 1,500 cycles. This extreme temperature range and extended cycling environment exceeds the survivability requirements of conventional packaging used in military (~55° C to 125° C for only 100 cycles) and commercial applications. Material properties of these packaging materials, such as modulus of elasticity and thermal coefficient of expansion, are not known at low temperatures. The continuous change of temperature in the Mars environment introduces electronic reliability factors resulting from thermally induced fatigue of the IC package.

The packaging scheme developed by TCRE is currently a baseline for MSL electronic subsystems, such as the motor cold encoder, that will operate in the Mars environment without thermal control. Research in these areas has led to the development of design guidelines and materials recommendations for low- temperature environments that would be available for all future Flight Programs.

High Temperature Survivable Electronic Systems for the Venus Environment

Previous Venus Landers employed high-temperature pressure vessels with thermally protected electronics, which had a maximum surface lifetime of 127 minutes, to achieve successful missions. Extending the operating range of electronic systems to the temperatures (485° C) and pressures (90 bar) of the Venus ground ambient would significantly increase the science return of future missions. Toward that end, current work endeavors to develop an innovative sensor preamplifier capable of working in the Venus ground ambient and designed using commercial components (thermionic vacuum devices; wide-band-gap, solid state devices; thick film resistors; high-temperature ceramic capacitors; and monometallic interfaces). To identify commercial components and electronic packaging materials capable of operation within the specified environment, a series of active devices, passive components, and packaging materials were screened for operability at 500° C, assuming a 10x increase in the mission lifetime.
Venus Missions and Atmospheric Probes to Gas Giants were among six New Frontiers Missions proposed in the Decadal Solar System Exploration Survey. Currently, there are two Venus mission types planned:

1. The Venus In-Situ Explorer, which would require the operation of sensors, actuators and electronic interfaces at Venus temperatures.
2. A Venus surface explorer, which would require long-term survivability of more complex sensor systems capable of operation within the ambient conditions of the Venus surface.

The technology developed in this project could also be used for Jupiter deep probes, which reach pressures of up to 100 bars at temperatures of 450° C. Therefore, survivability and operation of electronic systems in extreme environments would be critical to the interests of future NASA missions. Mission requirements for planets such as Venus would cover the extremes of the temperature spectrum, greatly exceeding the rated limits of operation and survival of current commercially available military and space-rated electronics, electronic packaging, and sensors. In addition, the desire to incorporate distributed electronics into future missions would necessitate that disciplines for making such systems are investigated as soon as possible.

Labview modeling for high tempearture electronics and packaging

High-temperature electronics and packaging reliability methodology and cabling issues

The goal of this project is to create a systematic reliability methodology with a physics-based predictability model for high-temperature technology operating up to 500 degrees Celsius. Using Lab view, this model has been tested on Gann and SiC devices that are common components of analog and digital circuit boards. Both devices were characterized between 500 – 525° Celsius. Additionally, this methodology is used to evaluate Al2O3 and AlN substrates used in packaging materials. Research on this reliability study and modeling are ongoing.

Designed-in-Reliability for low-temperature electronics

Sponsored as a JPL internal Research & Development effort, a significant amount of attention is being directed at creating methodology and model to evaluate a COTS (consumer over-the-counter) electronic system for low-temperature applications. This would help engineers design electronics with existing fabrication processes templates, while still being able to tailor electronics to their specific requirements.

Contacts

Andrew Shapiro - Management Contact and Electronics Packaging
E-Mail: Andrew.A.Shapiro@jpl.nasa.gov
Phone: 818.393.7311

Yuan Chen - Extreme Environment Reliability
E-Mail: Yuan.Chen@jpl.nasa.gov
Phone: 818.393.0940

Jason Heidecker - Design-in-reliability Matlab
E-Mail: Jason.L.Heidecker@jpl.nasa.gov
Phone: 818.393.7567

Rosa Leon - Cryogenic Chamber
E-Mail: Rosa.Leon@jpl.nasa.gov
Phone: 818.393.9066

Linda del Castillo - High Temperature Chamber
E-Mail: Linda.Y.Delcastillo@jpl.nasa.gov
Phone: 818.393.0418

Links

• Extreme Environments Technologies for Future Space Science Missions Report

• JPL Assurance Technology Program Office (internal JPL only)