From: Clay Naiser ME_CHN@hal.lamar.edu
This week the group continued to develope a spreadsheet to size the regenerative fuel cell system. After a meeting with Michael Le, a power specialist at NASA's JSC in Houston, more information was gained as to how to size the system components. Also, information was received from solar array vendors and electrolyzer vendors with specifications on their products. As of right now, the fuel cell is be designed to provide a maximum of 573.5 Watts. This is the maximum power required during lunar transit. Both Alkaline and PEM fuel cells are being considered. In order to provide this much power the Alkaline fuel cell will weigh approximately 46.68 kg. With a volume of .0611m^3. The PEM fuel cell will weigh approximately 39 kg and have a volume of .0288 m^3.
To date, the PEM fuel cell is not space qualified, however, it is expected to be space qualified in the next couple of years. The alkaline fuel cell is currently being used in the space shuttle, however is much more bulky than the PEM fuel cell. This is the reason that both fuel cells are being considered.
The operating temperature of the PEM fuel cell is 356 K and the operating pressure is 690 kPa, or 100 psi. The heat rejected will be .258075 kJ/h. For the Alkaline fuel cell, the operating temperature is 356 K, and the operating pressure is 413.7 kPa, or 60 psi. The amount of reactants required for the mission will be approximatly 30.5 kg of O2 and 4 kg of H2. These reactants will be stored in high pressure, composite tanks. Materials and masses of the tanks are yet to be determined.
The size of the solar array was determined by the power requirements during the lunar day. The requirement is 442.73 Watts. The type of solar cells being used are the GaAs/Ge. By using equations provided by Wertz and Larson, it was determined that the area of the solar array needs to be 2.64 m^2, and will have a mass of approximately 18 kg.
As of right now, total system weights using the two different fuel cells have been determined. However, this excludes the mass of the electrolyzer, mounting brackets, as well as pipes, pumps, valves, etc. If the Alkaline fuel cell is used the total system mass to date is 146.90 kg. If the PEM fuel cell is used, the mass of the system is 139.22 kg.
It is obvious that this exceeds the power system mass budget of 50 kg. However, this budget was determined from the Artemis mission which only survived on the moon for 1 hour and was able to rely on solar arrays for power during lunar transit. In order to bring the mass of the power system down, it is recommended by the power team to significantly reduce the duration of the mission. The power system of a one year mission being compared to that of a one hour mission makes no sense, thus either the duration must be decreased to a recommended 40 days, or else the power budget must be increased to at least 150 kg.
Next week will be mainly devoted to sizing the electrolyzer and completing the mid-term report. Also, storage tank vendors will be contacted in order to obtain their specifications.
Mass: 140 kg