Payload #2

Launch Date: Saturday, May 29, 1999

June 11, 1999

June 4, 1999

Payload assembly photos now online!
New calculations based on ground scale features and lens focal length put the height of the highest photo at 83,000 feet.

May 29, 1999

Mission successful!
Launch occured today at 10:15 A.M., Central Time from a farm just west of Manville, North Dakota. All systems functioned perfectly. Temperature telemetry was recorded and will be decoded and put on this website as soon as sensor calibration is calculated. The 35mm camera worked as planned, and took 18 aerial shots. Unfortunately, two of them were ruined when it appears the camera slipped a few gear teeth while advancing the film. This caused three pictures to be taken on two frames. All air photos from the flight are available here. The recovery team found the payload in a ditch approximately 6 miles outside of Warren Minnesota. It was discovered by a farmer who at first suspected it was a bomb (the writing on the gondola explaining that it was a harmless experiment was lying face-down, and the outer shell had come loose, exposing the beeping internal electronics). Additional images from the chase and recovery of the payload will be scanned and added soon. For now, you can look at the design of the gondola housing here. The new flight control software can be viewed here. More updates to follow.

May 20, 1999

Construction of the second payload is nearly complete. Pictures will be put on the website as soon as they are processed and scanned.

Items completed:

New dust collectors have been built. These are passive units, requiring no power or control from the microcontroller. This simplifies coding of the control program, as well as helping to conserve power.
Flight battery pack is complete. This unit is made of three lithium cells, outputs 9 VDC, and contains an internal fuse.
New camera mount is complete and has been installed in the gondola.
Transmitter keying circuit has been installed.
Modular CPU unit and seperate wiring harness have been built and are currently in testing.
External speaker is wired and functional.
New parachute has been constructed and tested.
New gondola design has been mostly built and gear is currently being installed on it. It is made from pink foam insulation sheeting, assembled with 'liquid nails' latex adhesive and bamboo shish-kabob skewers. The base plate has plastic risers supporting shelves that contain all the flight hardware except the dust collectors. The remaining shell is lowered over the assembly and held to it via strings running from the bottom plate through the gondola and out holes in the top. These strings then meet and are attached to the parachute, lanyard, and finally balloon. The dust collectors will be mounted to the outside of the gondola.
Temperature sensors. Two Radio Shack thermistors have been attached to two of the microcontrollers input lines. These two sensors will be used to sense the temperature inside and outside the payload, which will then be transmitted via Morse code along with the ID and tracking signals.
Transmitter to main flight pack tie-in. One charging socket has been modified to allow it to be attached to the main payload power system. This will allow the main pack to continuously top off the charge of the transmitter's built-in battery.

Items still under construction:

CPU to transmitter audio interface.
Main power busses.
Gondola shelves.
Flight sequencing software.
Dust collectors.
Balloon filling ballast. The payload must be assembled and weighed before this can be made.
Scale calabration.

Things will be a bit tight time-wise, but we believe we can still make our early Saturday launch target.

May 6, 1999

Our second balloon payload is currently under construction. This time I promise to take pictures of the hardware and post them on this website, as well as (possibly) some wiring diagrams and program listings.

The design of the mission this time is basically identical to our first mission, with fixes added. The current list of things to change is:

Transmitter battery power - the radio transmitter will run off the main flight battery pack this time, rather than rely on the tiny built-in battery in the radio.
Lighter flight battery pack - the first payload carried no less than 8 lithium cells. This was in part due to miscommunication about voltage requirements of experiments, and poor planning of the power harness. This flight will carry only three cells (not counting internal cells in the camera and radio).
Lighter physics experiment - the new dust collector should be smaller and lighter than the first one, as well as demand a lower voltage from the flight battery pack.
Gondola construction - rather than trying to convert an unweildly foam box for use, we will design and build a payload container using foam sheeting.
Microcontroller -> transmitter audio interface - a mistake involving signal level calculations caused me to build an interface that lead to massive overloading of the microphone input on the radio (my fault). The radio's limiting circuitry clipped the level, causing the Morse code ID signal to be very faint.
Ballast - not having proper calibrated ballast weights caused us to fill the balloon with insufficient helium to lift the package the first time, and may have played a part in the first balloon not reaching proper altitude and bursting as it was designed to do. Carefully weighing the payload and filling a gallon water jug with the same mass of water (plus the weight of the prefered free lift amount) will make filling the balloon a much less hit-or-miss affair.
Balloon nozzle seal - on the first balloon, the nozzle was tied shut with cotton twine. It was difficult to determine if the knots were tight enough to prevent escape of gas from the balloon. For the next mission, we plan to use nylon cable ties to secure the nozzle and attach the payload tether to the balloon.
Launch site - we may move the balloon launch site further west from Grand Forks. It's not that we don't mind driving in Minnesota, but trying to hunt for a downed balloon in the woods is a pain.
Telementry - if time allows, we will attempt to have the balloon transmit temperature telemetry data during its flight (as well as the tracking and ID signal).
Launch date - the first balloon was launched on what we later found out was amateur radio field day. This was helpful in that many hams were on the air, but unhelpful in that there weren't many hams available for chase teams. Better coordinating with our hams will help avoid this problem.
Checklist - on the first launch, everyone kept everything in their heads. This only lead to a few screw-ups, none of them particularly severe. Thankfully some in the group were on the ball and remembered to do things like double check tracking signals and bring everything needed to the launch site. Using a list will help us keep everything more organized and minimize the chances of forgetting something vital.
Overfill balloon - we will be using a larger amount of positive lift in the next balloon to try to ensure the balloon functions properly. It is suspected that insufficient gas and/or an improperly sealed balloon nozzle were to blame for the balloon rising to about 10,000 feet and staying there, rather than shooting up to 90,000 feet and bursting like it was supposed to. If the first balloon had behaved in the proper manner, the likelyhood of recovering the first payload would have been much higher.

In summary, as well as fixing some bugs in the first design, we will be sacraficing maximum altitude and time aloft for a better chance of payload recovery this time. Design of a reliable cut-down system is still progressing, but one will not be included on this flight because of lack of time. Overfilling the balloon should make the cut-down mechanism redundant, but including it on future designs that would carry more expensive equipment (like GPS receivers and APRS systems) will make their loss less likely.

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