Thermal - Lamar 3/1/96 Progress Report

From: Mark A. Magee

This Week:
Active Thermal Control System (ATCS)

To date, a general schematic for the ATCS has been drafted, and I will send it to you as soon as possible. For a brief explanation the system, it will consist of two separate loops, one for lunar day, and one for lunar night. This will help simplify the analytical model. The combination of these loops will be looked into in the future once the analysis begins. The loop for the lunar day will incorporate the fuel cell, the fuel cell input lines of the H2 and O2 tanks, and the H2O storage tank before entering the radiator to reject the remaining waste heat. The loop for the lunar night will incorporate the electrolyzer unit, the H2O input line to the electrolyzer, and then be routed to the radiator to reject the rest of the waste heat. The lamar power team is visiting with NASA engineers today (2-29-96), and I will meet with them in order to be informed on any new information they have gathered.

Information Still Needed:
Optimal Temperature of entering lines (H2O) into the electrolyzer. Optimal Temperature of entering lines (H2, and O2) into the fuel cell. Radiator Area available for use on top of spacecraft. Waste heat amounts from both the Fuel Cell and Electrolyzer units.

Now that concise literature pertaining to Aerogel has been received, I will begin to analyze how this material will hold up in the lunar environment. Rebecca Martin, the thermal control subsystem integrator, sent valuable physical and practical data about Aerogel that will allow me to begin a meaningful model. Different thicknesses of Aluminized Mylar and Aerogel will be modeled to determine the ideal insulation for the structure of the lander.

At this time, I still do not have an abundant amount of information pertaining to the thermal requirements for the propulsion systems. I do know the temperature limits of the propellant (MonoMethyl Hydrazine (fuel) and Nitrogen Tetra-Oxide (oxidizer)) that will be used . Next week, I plan to begin looking at what active and/or passive thermal control systems will be feasible, given the space allocated on the structure to sustain the temperature of the propellant. My main concern at this time also, is developing a thourough understanding of the functionality of the Main Propulsion System (MPS) so I can determine what portions of the MPS need thermal control. To address the previous problem I have, thermal requirements for the MPS have been requested from Rebecca Martin.

Next Week:
During the next week work will be completed on the mid-term progress report. Also, there are still many heat-loads that have yet to be determined. An approximation will be given to these areas until I hear otherwise from the respected systems. This will allow a start on the analytical model. There has been a question of where the best place for the radiator would be on the spacecraft. My recommendation for this question is to place the radiator on top of the spacecraft. This positioning will make it much easier to reject low-to- moderate temperature waste heat. The reasoning for this is that with the radiator positioned on top of the craft, it in effect does not "see" any radiation except for the direct solar flux (approximately 315 W/m^2). This will be explained in detail in the mid-term report.

mass: 45 kg
power: 45 W