July 07, 2015

SCEPS in Space - Non-Radioisotope Power Systems for Sunless Solar System Exploration Missions

Stored Chemical Energy Power Systems (SCEPS) have been used in U.S. Navy torpedoes for decades. NASA has given Michael Paul of Pennsylvania State University a phase 2 NIAC funding.

SCEPS works by combustion, just like when you burn natural gas, says Michael Paul, except in this case the fuel is lithium. The technology is not new, according to the US Navy, which says that it experimented with the process as early as the 1920s, and put SCEPS to work the Mk 50 torpedo in 1972. The Mk 50 is steam-driven using an exothermic chemical release to produce steam. With SCEPS there isn’t a problem of not making enough energy, but in scaling the energy down to manageable levels, according to the project description. Torpedoes like the Mk 50 could use thousands of kilowatts at a time, but NASA says that expeditions like the Phoenix Mars Lander only require hundreds of watts.

This high-energy-density, high-power technology can be reliably stored for years. In Phase I they analyzed the applicability of SCEPS to in situ solar system exploration, looking to see if it could be adapted to power a lander sent to a target with no usable sunlight as an energy source. They developed a candidate mission to the surface of Venus, showing that SCEPS could be used for powering spacecraft and landers. The team compared it to conventional battery and Plutonium powered systems, both of which have deficiencies that are overcome by SCEPS. Their concept holds the promise of a power solution that could far exceed the operational capacity of existing batteries, allowing exciting exploration to continue despite the lack of available Plutonium.

They propose to continue the research into applying SCEPS to exploration missions that can't be powered by sunlight. In this study we will mature the Venus mission studied in Phase I. They will also expand their understanding of the usefulness of SCEPS to exploration of moons, comets, asteroids and other targets where sunlight is not sufficient to power the mission. They will engage with the leaders in science planning for small bodies, outer planets, and robotic missions to our own Moon and make a determination of the first, most high-impact use of SCEPS in space. An experiment will be performed to determine SCEPS performance when using CO2 as an oxidizer, approximating the in situ resource utilization of the Venusian atmosphere. Venus science goals will be revisited to prepare the Venus concept for the next level of study.

Two key risks stand out. The first is their ability to scale down the power from current SCEPS implementation to levels more in family with spacecraft. Landed systems on Mars, for example, have had power levels on the order of hundreds of watts, far less than the many thousands of kilowatts that SCEPS provides for a U.S. Navy torpedo. The work proposed here would lead to better understanding of SCEPS operations at power levels appropriate to space exploration. The second risk is combustion with in situ resources.

In the case of the ALIVE mission, the atmospheric CO2 is proposed as the oxidizer. The analysis performed in Phase I indicates that the reaction would give of the necessary heat to power the lander. The use of in situ resources has its benefits: in the case of the ALIVE mission it reduces the mass of consumables that would otherwise have to be included on launch day by hundreds of kilograms.

In Phase II they seek experimental confirmation that this reaction can be initiated and sustained at the power levels required for such a lander. They see an opportunity to expand our understanding of the impact that SCEPS could have on solar system exploration. The sunless environment of Venus may indeed be explored through the use of SCEPS, but many cold, sunless regions may also benefit. Sending a SCEPS system to power a lander on the surface of Europa or the lakes or dunes of Titan may return substantial science that would be otherwise left unknown, or at least greatly delayed as the community works to solve the Plutonium-availability problem.

They will develop a multi-variable model for SCEPS function and performance using advanced trade space visualization and exploration tools and techniques. The trade space will include the information gleaned from the stakeholders. The trade space tools will allow us to see the intersection of SCEPS capability and mission utility. The collective results of the study will be used to create a roadmap for further maturation of SCEPS for use in space. In Phase II they seek to expand the understanding of how best to target this technology and plan a path for development by developing a roadmap for TRL advancement of SCEPS in space that mirrors NASA’s solar system science goals in this decade.

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