ATTACHMENTS.pdf

ATTACHMENT A

All potential/ interested parties planning to participate in this solicitation shall have successfully demonstrated real-time discharge performance under the LLISSE power profile in excess of 135 Earth-days of operation with over 400 discharge pulses in a five-cell battery design and at least 110 Earth-days of operation with over 330 discharge pulses in a 17-cell battery stack design. Due to the schedule limitations, there is no time to develop a new thermal battery chemistry with a low self-discharge rate.

Task A. Baseline Venus Thermal Battery LLISSE-based design

The awarded contractor shall develop and deliver to NASA a baseline design of a thermal battery. The design shall be based upon a mixture of state-of-the-art technology plus advanced components and shall consider the evaluation of battery system level impacts, i.e., watt-hour efficiency, thermal effects, materials compatibility, weight and volume and their effects on total power system mass and volume.

Design Life

The battery shall be designed for a minimum operational design life of 2.0 Earth-months (60 Earth-days) (under the discharge-only mode of operation), when operated at the discharge power levels described above in the “Electrical Power Demand” and Appendix A Table 2. “Key Performance Parameters” and Table 3. “Reference Venus Surface Atmosphere for LLISSE” at the temperature specified therein, and after storage.

Storage Life

The battery shall be capable of meeting the requirements of this specification after a storage period of up to 4 years at room temperature and one (1) atmosphere pressure after the battery final manufacturing date.

AA. Component Design

For the purpose of the Baseline battery design, internal stack elements shall be identified using state-of-the-art components. Attributes that shall be considered in the selection of the components include performance, weight, component availability, manufacturability, qualified processes, and cost. Materials compatibility shall also be considered. The Contractor shall support selections and identify advantages, disadvantages, difficulties and limitations associated with the selections. Selection of the baseline candidates shall be in consultation with, and with the approval of, the NASA Project Manager.

The following cell components are required:

a. Cathode

b. Separator

c. Anode

d. Electrolyte

AB. Battery Mechanical Design

The design of the advanced thermal battery shall address the mechanical design of the following structural components to survive the expected shock and vibration environmental loads during entry, descent, and landing on the surface of Venus:

a. Thermal Battery containment/housing and compression

b. Electrical feedthrough terminals

c. Mechanical support of internal cell components

d. Seals

e. Other components as necessary for internal thermal battery electrical connections

Task B. Screening “Baseline” Thermal Battery

BA. Fabrication of Screening Batteries

The Contractor shall fabricate five (5) batteries that operate between 25 volts and 19 volts and possess an ampere-hour capacity to meet the design life with a similar operational current density for the LLISSE mission using representative manufacturing and assembly techniques subject to the review and approval of the NASA Project Manager.

The Contractor shall continue with LLISSE thermal battery research in sub-scale hardware to conduct the cell stack redesign to improve overall performance. Based upon satisfactory development at the sub-scale level, the Contractor shall proceed with full-scale battery development subject to the review and approval of the NASA Project Manager.

BB. Testing of Preliminary Batteries

The Contractor shall test each of the Screening batteries fabricated in Task BA following completion of their manufacture under the LLISSE discharge power profile until failure.

Task C. Electrical Feedthroughs

CA. Development of Venus Surface Environment Compatible Electrical Feedthroughs

The Contractor shall develop and incorporate fully functional electrical feedthroughs into the thermal battery header to provide minimal electrical resistance. The electrical feedthrough shall survive the 94 bar Venus surface pressure and the corrosive gaseous environment contained in Appendix A, Table 3.

“Reference Venus Surface Atmosphere for LLISSE” for a minimum of 60 Earth-days. Based upon material compatibility test results contained in the NASA/TM-219437 report, it is suggested a titanium alloy or molybdenum electrical current conducting pin be utilized in an alumina or sapphire seal utilizing a pure gold or gold-titanium braze. The Contractor shall ensure the coefficient of thermal expansion is properly matched between the header material of construction and the gold braze/alumina/sapphire seal.

CB. Feedthrough Fabrication

The Contractor shall design, develop, and fabricate the Venus surface environment feedthroughs in either stainless steel or titanium battery thermal battery headers and a cylindrical battery containment vessel preferably consistent with the 1/3 scale battery design to demonstrate survivability in the Venus environment. The Contractor shall deliver 5 identical units without any electrochemical components inside the battery container. A minimum of 4 electrical feedthroughs per battery header are required.

Fixed resistors shall be welded to the interior feedthroughs to monitor any seal failures during life testing under the Venus temperature, pressure, and supercritical gaseous environment.

CC. Test Report

The Contractor shall submit a report for review and NASA approval covering the Contractor’s successful development activities of the new electrical feedthroughs pertaining to the braze, gland seal, and electrical pin material selection, drawings, and manufacturing processes pertaining to LLISSE performance testing.

Task D. Sensitivity Analysis/Trade Study

The Contractor shall conduct a sensitivity analysis/trade study investigating the specific energy, energy density, mass, length, and volume metrics for the 60 Earth-day LLISSE mission. The Contractor shall utilize their battery sizing programs to calculate and estimate battery design and performance based on engineering inputs of the LLISSE performance requirements. The Contractor shall investigate the material of construction of the battery container over a range of standard diameters. The baseline 1/3 scale diameter must be included as a design point. The Contractor shall investigate anode and cathode electrode pellet active loading ranges, electrolyte pellet binder and salt ratios along with pellet thickness. The Contractor shall consider peak discharge load requirements in detail to ensure the battery discharge voltage remains within the operating voltage window. Ensure the range of electrode pellet diameters maintain a uniform current density at the peak discharge rate. The Contractor shall provide an updated mass properties list, updated design trade-off studies (thermal, structural, manufacturing, and relative costs) associated with the LLISSE mission.

The Contractor shall determine the mass and volume impact of multiple parallel batteries to support the full LLISSE power level over the 60 Earth-days.

A recent option for the LLISSE surface probe modifies the low power continuous drain on the thermal battery. While the baseline discharge power load is 0.015 Watts, an alternate concept has been proposed called the “Listen Mode” which draws 0.045 Watts of power. In addition, there is a possibility of both concepts could be utilized simultaneously. This implies a discharge power level of 0.060 Watts. The Contractor shall determine the impact of these three continuous discharge power levels on the mass and volume of the sizing on the LLISSE thermal battery concept.

The Contractor shall provide graphical output comparisons to assess the range of component variables associated with the thermal battery on the overall mass, length, volume, specific energy, and energy density of the LLISSE energy storage system. A narrative summary shall be provided to address manufacturing, development, and cost impacts. The Contractor shall submit a report for review and NASA approval covering the Contractor’s Sensitivity Analysis/Trade Study.

Task E. Thermal Battery Electrochemical Component Exposure to Venus Atmosphere

The Contractor shall design and fabricate two identical 1/3 scale thermal batteries comprised of 5 cells in series based upon the successful electrochemical design. The stainless-steel header shall be modified to include a ½” diameter fill port outfitted with a manually operated valve that can be opened and closed under room temperature and 1 atmosphere conditions. The open end of the valve shall include a burst disk designed to fail at approximately 20 to 30 psi external pressure. The purpose of these two thermal batteries is to assess the impact of the supercritical CO2 Venus environment on the material compatibility of the electrochemical components inside the thermal battery. The Contractor shall fabricate the thermal batteries under their standard manufacturing processes. The selection of the fill tube, manually operated valve, and burst disc will be in consultation with the NASA Project Manager.

After exposure of the 1/3 scale thermal battery to the supercritical CO2 Venus environment, the manually valve sealed units will be returned to the Contractor for post-test X-ray and a teardown via a destructive physical analysis. Components from the thermal battery shall be appropriately sealed from moisture and oxygen exposure and shipped back to NASA Glenn for further analytical chemical analysis.

Task F. Destructive Physical Analyses

The Contractor shall provide a cost estimate for conducting destructive physical analysis of the 1/3 scale multi-cell thermal batteries previously fabricated for NASA’s LLISSE project. The contractor shall perform their standard destructive physical analysis including X-ray, inspection of components, and a narrative summary of the physical changes that occurred during the testing. The Contractor shall provide a cost estimate on a per cell basis and a blanket cost for a minimum of three battery units to the maximum of 6 battery units. NASA shall ship the failed batteries to the Contractor’s facility for the destructive physical analysis. The Contractor shall provide a written narrative summary, X-rays, and component images associated with the failure investigation. The Contractor shall submit the destructive physical analysis report for review and NASA approval for each thermal battery.

ATTACHMENT B

Pertinent Minimum Performance Requirements

Table 2. Key Performance Parameters

Energy Storage Mass and Volume Allocations

Maximum Outline Dimensions = 4.0 inch outside diameter X TBD length per battery

Maximum Allowable Mass = 5.72 kg

Minimum Battery Level Specific Energy = 28.6 Wh/kg

Minimum Battery Level Energy Density = 40.45 Wh/l

Operating Voltage = +25V +0/-6 volts and -25V +6/-0 Volts (TBR)

Self-Discharge Rate = (TBR) at +4600C

Non-operating Environment

Long Term Storage at Room Temperature and 1 atmosphere

-930C during transit to Venus under hard space vacuum

Operating Environment

Surface Temperature Target value is +4600C (+100C/-300C)

Surface Pressure 95 atmospheres

Impact shock 12g (with 5 cm crush pads)

Table 3. Reference Venus Surface Atmosphere for LLISSE

Reference Venus Surface Atmosphere for LLISSE

Mole Fraction

Percent Conc.

Carbon Dioxide CO2 9.65E-01

Nitrogen N2 3.50E-02

Water H2O 3.00E-05

Sulfur Dioxide SO2 1.80E-04

Carbon Monoxide CO 1.20E-05

Carbonyl Sulfide COS 5.10E-05

Hydrogen Sulfide H2S 2.00E-06

Hydrogen Chloride HCl 5.00E-07

Hydrogen Fluoride HF 2.50E-09

1.00E+00 Total