SMITH Payload

The main purpose of this payload is to take biological samples at a range of altitudes in the mid stratosphere. Since HASP will float at 120,000 ft, this will be the targeted altitude for this flight. The payload will consist of a sample chamber and a flight control chamber. The flight control chamber measures the background contamination throughout the flight without actively sampling. The sample chamber actively samples at the target altitude. Both chambers will be physically identical, but the flight control chamber will remained sealed. In the event the sample chamber fails to operate during flight it will be possible to use the flight control chamber to actively sample as the sample chamber. Since we would lose our flight control, this will be done only as a last resort.

Before flight, both chambers will be sterilized and sealed. They will remain in this state until HASP reaches float. At this point two commands will be sent to the payload to enable the sample chamber heaters. This will ensure the motors are in operational temperature range before use. Once at float, a command will be sent to begin sampling. This command opens the sample bay and begins the sampling procedure. Confirmation of a successful opening will be relayed to the ground station, at which point a command will be sent to disable the door heater. The reel heater will remain enabled to maintain the motor's temperature. Data on all sensors, including door and sampling status, will be relayed to the ground station throughout the flight.

Shortly before cut down, the door heater will be enabled to ensure it is in operational range before use. A command to stop sampling will then be uplinked to the payload. This will fully reel in the sampler and close the door, sealing the bay again. Once confirmation of a successful closing is received, a command will be uplinked to disable all heaters. The payload will then remain in this state until recovered. If for some reason the sample bay fails, commands can be relayed to the flight control bay that follow the same procedure as stated above.

The sampling device requires a minimum of 1000 L of atmosphere to pass across each rod during the entire flight. Since SMITH will be at float during active sampling, a volume needs to be passed across the sampling device. Two systems were analyzed to produce flow: pump and yo-yo. A trade off study was done between the two to determine which was best for our needs. The yo-yo system uses a rod chamber suspended below the payload. The rod chamber is lowered and reeled back up repeatedly throughout the flight to provide the necessary flow. The volume sampled is calculated by the horizontal cross-sectional area multiplied by the vertical distance traveled in a single up or down cycle.