Thermal Phase C Testing

Introduction

This page is used to document all tests performed on the thermal subsystem and its components throughout the Phase C. Phase C testing includes the thermostat qualification vibration test and the primary heater prototype test.

The verification activites are

V-THE-0171-Test prototype primary (Datec) heater installed in battery pack to verify sufficient heat flow is occurring (gradient less than 5 degrees C from heater surface to batteries). -Completed

V-THE-0810-Vibration test engineering model thermostats to qualification levels to verify they can withstand the vibration environment of launch. -In progress, delayed due to equipment malfunction.

Thermostat Qualification Vibration Test

We are performing vibration testing on one thermostat. 6 thermostats were procured at the same time (considered same lot). We first tested all six thermostats to determine the actual cut in and cut off temperatures of each unit. The thermostats have an expected cut in temperature of 10C, an expected cut off temperature of 21.1C, and a tolerance of +/- 2.8C on these settings. The following two tables show the test plan and results of these tests.

We used this data to select the thermostat with the optimal cut in and cut off temperatures to be used as the flight unit (Thermostat 5). We selected a second unit to be used for vibration testing (Thermostat 2).

Datec (Primary) Heater Prototype Test

The objective of the Datec heater test is to observe the performance of the heater in the full saddle and battery assembly. The test plan consists of installation and temperature measurements . Since the Pre-CDR, the saddle has been manufactured and the test was carried out. The test results meet verification activity V-THE-0171 with a maximum gradient of 3.1 °C.

The test plan is described below. The data logger used has four channels therefore, four locations were measured. A sampling rate of 2 seconds was used. The heater was left on for approximately 50 minutes before left to cool down.

Probe locations

Temperatures were measured using the following probe locations:

1. Heater: located directly on top of the heater, in between the saddle and board.

2. Thermostat: located on the underside of the image, between the clearance holes of the thermostat fasteners .

3. Saddle: located at the furthest point away from the back face of the heater.

4. Battery: located across a side face of the battery.

Results

The temperature profiles collected during the test are shown in the figure below along with a sample of the data collected. The biggest temperature gradient exists between the battery probe and the heater.

The smallest temperature gradient is between the heater and thermostat. Which are only separated by the saddle surface, the heater was laying flash with the surface creating a direct conductive path with the thermostat probe.

The results show a mild temperature gradient with a maximum of 3.1 °C occurring at the peak of the curve.

Discussion

The verification activity has successfully been closed.

The heater was also tested individually to test its performance. It heated to its maximum operational temperature from room temperature in just under 3 minutes.

The prototype test allowed me to assemble the saddle components and as a result, a few observations and improvements have been made.

1. The soldering and electrical wiring adds to the height of the heater and does not allow the top part to be flash with the board. An air gap exists. The saddle board piece has been modified with a rectangular cut out around the soldering points. This allows the harassing to be easily accessible and not interfere with the design.

2. The electrical connections were directly soldered to the heater pads. This however created a strain on the wires, and they had to be carefully handled. I am concerned about the wiring disconnecting during a vibration test. Therefore, this topic of soldering will be revisited with the manufacturer for the final flight model. Ideally, they would complete the soldering professionally on their side.