Turn up the heat and the pressure's on!

After a 3 hour test run of my flight computer and cameras I had a lot of success and one problem. I ended the test by putting the whole payload in my freezer. The flight computer came out just fine, but the cameras shut down from being too cold. I've added insulation and space blanket wrapping to keep them warm, but I don't know if it will be enough for the -50 F temperatures. My freezer read as -2 C (about 30 F). Below are graphs of pressure and temperature during the testing.

Pressure in PSIA

Temperature in degrees C

With the data gathering out of the way I've been covering the payload casing in space blanket to make it reflective to radar. I wouldn't appreciate it if an airplane hit my project, but I think they would be even more angry. I've also done more flight predictions and come up with a tentative launch site. The site is east of Billings just off of the freeway on Yellowstone Trail Rd. You can see the launch spot in the picture below. The other picture shows the University of Wyoming's flight prediction (http://weather.uwyo.edu/polar/balloon_traj.html) and the Near Space Venture's landing spot prediction (http://nearspaceventures.com/w3Baltrak/readyget.pl). The difference is that the University of Wyoming won't let me put in my ascent or descent rates. I expect the actual landing site will be somewhere in-between the two, which would be great. I hope to see a ton of people at the launch site and be completely surprised...by the one person following this blog I thing it's going to be just me, Arhan, and my dad though. I'll post the final launch site as soon as it is solidly established and I'm thinking about a twitter feed.

Launching East of Billings, MT on Yellowstone Trail

The flight predictions have the balloon going further east

Put it all together, and what have you got?

The answer is a somewhat shabby looking near space balloon payload. It is all working brilliantly though! You can see in the pictures below how the parachute bay folds open and how there is a string that wraps around the soda bottle to a 2 prong hook to hold the hatch closed during the ascent. There's a servo motor inside that pulls the hook closed during ascent and pushes the hook out when the set altitude is crossed twice (once going up primes the circuit and then on the way down the servo pushes the hook out letting the parachute hatch be opened by the force of wind).

Parachute bay open, cameras in the green section

GPS antenna on the left, pressure sensor where the coiled wires are in the middle

2 prong hook holding parachute bay closed by the string

Cellular antenna from EAD-LTD.com

Last weekend I also did a test inflation and tethered flight of the payload I had completed at the time. During that inflation I used a nitrogen regulator on a 130 cubic foot helium tank. In-between the regulator and the balloon was just a section of air hose, which worked alright to inflate. The problem with that setup is that I had no idea how much weight the balloon was lifting. I had to use my hand to keep the balloon sealed to the air hose, so we just filled the balloon until the tank was empty. I've seen on a few websites that 1 extra pound of weight is enough to give the balloon a 1000 ft/minute ascent rate. Sure, I could just inflate the balloon all the way and let it rocket up until it bursts, but the less helium I put in the higher it will go (it has to be able to lift the payload of course and it has to make it through the cold tropopause without getting too brittle). With all that in mind I created a new end for the filling hose that weighs just under 1 pound. The filling end fits snugly in the balloon opening and with the help of a hose clamp it will add exactly one pound of weight to my payload. Now I just hang my payload from the red lever on the filling end, fill up the balloon until it starts to lift the payload off the ground, tie everything off, and let it go.

Regulator, hose, and filling end

The filling end is a 3/4" brass plumbing shutoff valve, and a 3/4" to 1/2" adapter to connect to the hose. On the balloon end of the shutoff valve I have added some automotive gasket material and silicone to make the end round instead of the hex bolt shape. It's very difficult to get a good seal on the balloon with the hex shape.

Looks like this time I was early on my deadline! Tomorrow I'm going to do lots of testing and then put the finishing touches on the payload. It will look a lot nicer once I get the space blanket wrapped around it. It's kinda like a classic car without the chrome bumpers right now. See you next time space cowboys!

GPS Tracking and Logging...finally

Well it's about time that things are coming together. I have one week left before the launch, so it's getting a bit tense. I have decided to scrap the idea of steering the payload back to the launch location. I don't have the time to make the mechanical pieces, the code would be simple though. I also scrapped the SD cards since they were not being very reliable. I am now logging the data to the microcontroller's flash memory. I have three things left to finalize. The first is the parachute ejection system, the second is the pressure sensor logging, and the final one is the finishing touches of the payload. I should have it all tidied up by the end of the weekend...I think I've said those words several times on this blog and have yet to live up to it...
Anyway, below are some pictures of a car trip I took with the flight computer GPS logging and my computer tracking the trip live. I've written a windows application to read the serial data coming from my GM862 cellular module. It displays the most current reading and writes all the captured data to a .kml file to be displayed in Google Earth. In Google Earth you can create a network location that points to the .kml file and has a refresh rate so the data is updated in "real time."

• My windows tracking application and source code
• My AVR Studio project for the flight computer firmware
• The tracking application .kml file
• A .kml file created from the flight computer log

My glorious tracking application!

The track generated by my tracking application (~1 GPS point per second)

The track generated from the flight computer log (10 seconds of averaged data per point)

Oh, to make a CSD call...

Well, it's been a tough week. The balloons and parachute came in over the weekend, so I was very excited at the start. Then, I spent $50 on an AT&T SIM card only to find out that they don't support CSD calls (it's like a fax machine or a dial-up modem). I borrowed two T-mobile SIM cards to test them for CSD calls and it worked! I quickly went to the T-mobile store and tried to buy two prepaid cards, but this store locks their prepaid cards in a time-lock vault after 5pm. I showed up bright and early the next morning to buy the cards and when I went to test them they didn't actually get activated. Since I'll never be able to get to the store before 5pm before my test launch on Saturday I had to get a refund and go shopping elsewhere. I found another T-mobile store and ended up paying twice as much for the SIM cards as the first store. I was also told that CSD calls would definitely work. By this time it should be no surprise to you that CSD calls do not work with T-mobile prepaid SIM cards. Tomorrow I am going to attempt to get the SIM cards converted into a one month family plan, wish me luck!
Since I don't want to leave you with a bad taste in your mouth (it should be about poopy flavored lollie pop by now), I'm going to attach the balloon and parachute photos below. You'll notice that the parachute is not the normal circular shape. The "x-form" parachute is used by high powered amateur rockets because it reduces the drifting caused by wind. That sounds like a brilliant thing to use on this project. We'll see how it turns out in about two weeks!

6' in diameter!!! 1200 gram balloon from Kaymont

Inlet is about 2.5" in diameter and very stiff

60" x-form parachute from Top Flight Recovery (purchased from Performance Hobbies)

60" chute folds to about 4"x2"

Dismantled Argus Bean camera

Deeper inside

All back together with wires soldered across the shutter switch so I can virtually snap photos with the microcontroller.

FAA

Before I start talking about who you need to notify about your launch I'm going to tell you that you should read Part 101 Subpart D of the FAA regulations. You can find the current version on the FAA's website. If you read the whole Part 101 regulation you'll notice at the very start that the regulation only applies to free balloons with payloads heavier than 4 pounds, so most amateur projects won't really fall under the scope of the regulation. You should still follow all of the rules in Subpart D to remove yourself from as much liability as possible. Not following the rules can lead to fines, imprisonment, and more importantly could seriously injure or kill someone.
Now, on to who you need to talk to. I have to admit that I've heard horror stories about dealing with the FAA and I was very nervous about calling. It doesn't help that I didn't really know what office I should call or who I needed to talk to about this project. I started by calling the FISDO (flight inspection safety district office) in Helena, MT. They seemed to be the most prominent FAA presence in Montana, and it turned out to be a pretty good choice. The FISDO doesn't have anything to do with small balloon launches, but they did point me to the right ATC (air traffic control) office. The ATC office doesn't actually have anything to do with small free balloons either, but information about your launch will get communicated to them through the NOTAM system. NOTAM (notice to airmen) is a system of hazardous condition reporting for the skies. It covers things from air shows to volcano eruptions...yes we're looking at you Iceland. The ATC office I talked to gave me a phone number for Prescott Flight Service Station (877-487-6867). They apparently handle all of the NOTAM reporting for the "West US." I have no idea what is included in "West US" so you should call the FAA ATC office closest to your launch and ask what the NOTAM reporting number is for your area. When you launch your balloon you should be ready to give your launch location, launch time, time to 60k feet ascending, time of reaching 60k feet descending, expected landing location, and expected landing time. You need to make this call no earlier than 24 hours before the flight and no later than 6 hours before the flight. If you cancel or change the times you need to update the NOTAM immediately. You should also notify the NOTAM station when you actually reach 60k feet up and down, if you lose communication with your balloon, and when your payload has landed if possible. That's all the reporting you need to do.
The 60k feet barrier is important because 99% of aircraft can't fly above that altitude. Unless you're hanging out in Korea or Russia there won't be too many U-2 spy planes cruising past your balloon and there's only one X-37 space plane in existence right now. So, once you're above 60k feet you can breath a little bit easier knowing that you won't be ingested by a jet engine. One note about launch site selection is that you need to make sure you are more than 5 miles away from any airport. It's also a good idea to plan your flight path so that it doesn't cross over any airports. This is in the Part 101 regulations, but it's easy to miss. My launch is still on for 3 JULY 2010 at 1 PM from the Billings, MT area (actual location to be selected about 4 days ahead of launch for weather reasons).