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NASA Marshall Space Flight Center and the Johns Hopkins University Applied Physics Laboratory have developed several mission concepts to place scientific and exploration payloads ranging from 10 kg to more than 200 kg on the surface of the moon. The mission concepts all use a small versatile lander that is capable of precision landing. The results to date of the lunar lander development risk reduction activities including high pressure propulsion system testing, structure and mechanism development and testing, and long cycle time battery testing will be addressed. The most visible elements of the risk reduction program are two fully autonomous lander flight test vehicles. The first utilized a high pressure cold gas system (Cold Gas Test Article) with limited flight durations while the subsequent test vehicle, known as the Warm Gas Test Article, utilizes hydrogen peroxide propellant resulting in significantly longer flight times and the ability to more fully exercise flight sensors and algorithms. The development of the Warm Gas Test Article is a system demonstration and was designed with similarity to an actual lunar lander including energy absorbing landing legs, pulsing thrusters, and flight-like software implementation. A set of outdoor flight tests to demonstrate the initial objectives of the WGTA program was completed in Nov. 2011, and will be discussed.

Tests were conducted to investigate the recovery of capacity lost during open circuit storage of negatively precharged nickel hydrogen batteries. Four Eagle Picher RNH-90-3 cells were used in the tests. Recovery procedures and test results are presented in outline and graphic form.

Negatively precharged nickel hydrogen cells will experience a useable capacity loss during extended open circuit storage periods. Some of the lost capacity can be recovered through cycling. Capacity recovery through cycling can be enhanced by cycling at high depths of discharge (DOD). The most timely procedure for recovering the faded capacity is to charge the cell fully and allow the cell to sit open-circuit at room temperature. This procedure seems to be effective in part because of the enlarged structure of the active materials. The compounds that formed during storage at the low electrode potentials can more easily dissolve and redistribute. All of the original capacity cannot be recovered because the lattice structure of the active material is irreversibly altered during storage. The recommendation is to use positively precharged cells activated with 26 percent KOH if possible. In aerospace applications, the benefits of negative precharge are offset by the possibility of delays and storage periods.

The test setup consists of four major elements: the programmable power supplies and load banks, the data acquisition and control system control computer, and the NiH2 specimen test cells. A simplified block diagram of the test setup is shown. The test setup provides complete battery isolation should a fault occur, and fusing as necessary to protect the battery cells and other equipment. Front panel switches provide for power supply configuration and battery isolation. Front panel meters provide continuous real-time visual monitoring of the voltage and current for each pack of cells. A strip chart recorder provides a hard copy of the voltage and current profiles for each of the packs. The test operates continuously with minimal human interface, except during special tests. The two power supplies are controlled by resistance programming. A bank of resistors and relays was built which can be switched by the control computer to provide control over the charge current to the batteries. The load banks are controlled by the 3497A. The 3497A is equipped with a 0.5 volt programmable power supply which is used to voltage program the load banks. A Hewlett-Packard Vectra 9000 running an HP Basic program is used as the control computer to remotely instruct the 3497A (data acquisition and control) to scan the data channels and retrieve test data. The program then reads, calculates, and stores the data. If an anomaly occurs, the program will disconnect the cells and shut down the test to avoid damage to the cells or equipment.

Two NiH2 two-cell packs made up of engineering cells built according to the Hubble Space Telescope design (EPI RNH 90-3) are currently being low-earth-orbit (LEO) cycled at 20-50 percent depth of discharge (DOD). The cells were manufactured by Eagle-Picher Industries, Inc., and activated with electrolyte (KOH) concentrations of 26 percent (pack No.1) and 31 percent (pack No.2), for use during evaluation of the HST cell design. The cells have been grouped according to electrolyte concentration but follow the same test schedule for comparison. This test was set up to study the behavior of NiH2 cells having differing electrolyte concentrations, when operated at relatively high DOD (20-50 percent) in a LEO cycling program. The test was designed specifically to allow the cells to pick their own recharge ratio for varying DOD and varying EOC (end of charge) voltages. The cells are being cycled in a simulated 96-min orbit with 60-min charge and 36-min discharge where an EOC cutoff voltage controls high-rate charging. EOC cutoff voltages vary between 1.48 V and 1.56 V.

The primary objective of the testing is to characterize Ni-H2 cells for successful integration into the electrical power system (EPS) of the Hubble Space Telescope (HST). A broad spectrum of Ni-H2 design technology is encompassed by the testing configurations; tests include cells with dates of manufacture as early as 1976. The database includes cells of varied storage times, capacity, plate design, stack design, terminal configuration, pressure vessel thickness, separator material, potassium hydroxide (KOH) concentration, and thermal control. Currently, 196 Ni-H2 cells are being tested, grouped as follows: 12 RNH-35-3, 14 RNH-30-1, 22 HST cells (1 battery, flight spare lot), 132 HST cells (6 batteries, test modules 1 and 2, called TM1 and TM2), 12 HST cells (3 four-cell packs, TM1, TM2, flight spare module FSM), and 4 HST cells (engineering lot). In addition to the characterization and life testing, an extensive thermal vacuum and purge test was conducted in November 1989 and February 1990 using the HST FSM (3 batteries composed of 69 HST cells from the flight spare lot) to help verify thermal design. A report is presented of the progress, significant findings, and future objectives of the testing.