Category Archives: FAQ

Predict the flight path and contact the FAA

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It’s Legal

The first thing to know is that it is legal. It’s regulated by the FAA under Part 101 Subpart D of their regulations.

If you read the whole Part 101 regulation you’ll notice at the very start that the regulation only applies to unmanned balloons with payloads heavier than 4 pounds. Note that  you should still follow all of the rules in Subpart D to make the experience as smooth as possible.

I was a little worried about talking with the FAA. Especially since I was not sure of the phone number and requirements.

If you were to send a big balloon to Near Space, you would have to contact the right ATC (air traffic control) office. But in our case, the ATC office doesn’t actually have anything to do with small unmanned balloons.

What you need to do is create a NOTAM (Notice To Airmen).

NOTAMs are notifications issued for hazardous reasons, such as:

  • Air-shows,
  • Parachute jumps
  • Closed runways
  • Erupting Volcanos
  • …

Who do I need to call?

The ATC office I talked to gave me the phone number for Prescott Flight Service Station (877-487-6867).

I believe that they handle all the NOTAM reporting for the West side of the US. Where does West start? No idea, you should call your ATC office to make sure. I know that many people launching  balloons from different states (CA, UT, NV, …) called that specific office.

What does the FAA need to know?

What they ask you differs from one person to another.

What they asked me was:

  • Date and time of the launch ?(You need to notify the FAA between 24 hours and 6 hours before the launch)
  • Location of the launch? (City, States + GPS coordinates in both Decimal Degree and DMS formats). Converter can be found here.
  • How far it is from any major city, airports, air force base? (It needs to be 5 miles away from everything)
  • What is the ascent rate?

That was it for me. It was pretty straightforward.

However depending on who you talk to, be prepared to be asked:

  • At what time will it reached 60,000ft up?
  • At what time will it reached 60,000ft down?
  • At what time will it land?
  • Where will it land?

Theoretically, 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. Realistically, no one cared when I called and that was fine by me.

Why 60,000ft? Because most of the air traffic flies below this altitude.

How to choose your launch location and predict the flight’s trajectory?

When looking for your launch site, you need to think about 3 main factors:

  1. You must not have any fence, phone pole, electric pole, tall tree around you.
  2. You must take into consideration the winds (when you fill the balloon and during the flight) which can carry your payload up to 200 miles away.
  3. You must take into consideration the estimated landing area.
  4. You must take into consideration the estimated flight path.

1) You really do not want all your work to end up stuck in a tree or attached to a 100ft high electric line.

2) This is critical. There are 2 web tools: This one and that one. Their prediction are, of course, not 100% similar or accurate but they will give you a good idea of the flight direction.

3 & 4) Remember that you need to be able to recover the payload quickly (Batteries might die) and be able to receive signals from the landing location. Avoid highly populated areas or areas with lakes, mountains or dense vegetation.

Note that  you need to make sure your launch site is more than 5 miles away from any airport/AFB.

Take pictures

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To take pictures in Near Space, you can either:

  • Program a system with servo to push the camera’s shutter automatically or remotely
  • Program the camera to take pictures automatically

The latter is by far the easiest way to take pictures in Near Space.

The most famous way to program your camera is to use CHDK. CHDK (Canon Hack Development Kit) is basically a firmware enhancement software allowing you to control additional features and options of your camera.

The tool supports a lot of Canon digital cameras. So you really want to use a Canon camera. You can find the supported list here.

Note that it’s an enhancement tool, it is non-permanent and non-destructive. You load it from your SD card and it makes no actual changes to your camera and firmware.

Installing CHDK is pretty straightforward if you have an SD card of 4GB or less. You can find the step by step instructions here.

CHDK was created to run on FAT partitions and SD cards that are higher than 4 GB run on FAT32 partitions. For 8GB SD card or larger, things get more complicated. You can find how to install it here.

Note that despite all my best efforts, I have not been able to make it work on my 8GB SD card. It just would not work. (Maybe due to my SD Card brand…)

Once installed, you can create a script to take pictures with the desired settings every X seconds until the SD card is full or until the battery dies. You can find some intervalometer scripts here. Another interesting feature is that you can save the battery voltage and the different temperatures recorded by the camera sensors (optical elements , battery and charge coupled device (CCD)) in a log file. More info under get_temperature.

Track your balloon

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There are many tools with different pros and cons to track your balloon.

I am only describing the ones I have personally tried. This list will be updated as I launch additional high altitude balloons.

GSM GPS Phone with Tracking Software

A GSM Phone will only work up to a couple of thousand feet high. Therefore it’s mainly a way to find your payload once it landed.

The first criterion to think about when choosing the phone is its service network. You need to verify the phone will have a good signal where you plan to launch and retrieve it. No signal, no location.

In the Bay Area, Verizon is known to have the best network. However Verizon is known to sometimes block the GPS access requests from third party applications. The type of network (GSM, iDEN, CDMA…) doesn’t matter as long as the carrier provides an unlimited Internet data plan (GPRS, EDGE, EV-DO, UMTS, or HSPA…) for the phone. You’ll need to get a data plan from your carrier for the tracking software to transmit its position over the Internet.

The cheapest, lightest GPS phone I found is currently the Motorola I296. Its previous model which has been used in many high altitude balloon launches, the Motorola I290, has been discontinued. However you can still find on ebay. The I296 costs about $60.

Pros:

  • Inexpensive
  • Simple and Light

Cons:

  • Requires a signal upon landing

There are two out of the box tracking softwares:

I chose Accutracking because it simply offers more features and flexibility than InstaMapper.

  • Customizable buffer for store positions while out of coverage (100 max points for InstaMapper)
  • More details about the phone at each point (location + GSM Signal strength + GPS signal strength + Battery level)

In this screenshot, the dates in red shows positions that were initially stored because of the lack of coverage

Installing the software on the phone is straightforward. Instructions can be found here.

Satellite Tracker

The cheapest and most convenient is the SPOT Personal Tracker. This tracker does not need cell tower coverage. It communicates its position by satellite. You log on the SPOT website to see the received locations.

Pros:
  • No cellphone tower signal required
  • Tough built : Operational temp -45C to 85C (-40F to 185F) and waterproof
Cons:
  • 10 min update frequency
  • Max operational altitude is 6,492m (21300 ft)
  • The altitude is not recorded
  • Device + Activation + Tracking option : >$200

Note: The Spot Tracker needs to be facing up towards the sky. I highly recommend you to build a gimbal system for your Spot Tracker. This can make all the difference. Do some real tests with your tracking devices activated and inside the payload as it would be during its flight (closed and tapped).

APRS Transmitter (updated 10/02/2011)

To learn the basics about APRS, click here.

An APRS beacon is basically a device (transmitter + GPS) which emits a radio signal containing its current location.

These messages are received by listening radio stations called digipeaters. There are thousands of digipeaters across the US. Digipeaters repeat the message received to other digipeaters until it reaches one radio station that has access to the Internet. These Internet gateways are called an Igates and publish the received messages on the Internet. You can then follow the location of your beacon online at websites such as Google Aprs.

There are plenty of APRS transmitters available. I chose Byonics’ Micro-Trak 8000 FA for its light weight and flexibility. Byonics has other models though.

The Micro-Trak 8000 FA operates on amateur radio frequencies, and requires a valid amateur radio license to use. To get one, take the technician HAM radio license test.  To take it, go here. Most centers propose a one day combo: class + test.
You can just show up in the morning not knowing anything, study in the morning with them and take the test in the afternoon.

You will need a GPS that works above 60,000ft. Because of ITAR regulations, most GPS do not work above 60,000ft. Make sure yours do. I bought the Byonics GPS4 (works up to 84km = 275,000 ft).

Pros:

  • Reports: location + altitude + speed during the entire flight
  • Locations saved online at aprs.fi and can be exported afterwards.
  • Power up to 10W
Cons:
  • Fairly fragile
  • Requires a lot of batteries
  • Fairly expensive (>$200)
Note: The MT 8000FA has been discontinued and replaced by the Micro-Trak RTG.

Balloon and Helium

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There are two kinds of balloon that you can use:

  • Sounding balloons
  • Cold Weather balloons

Sounding balloons will typically weigh in at 200 grams to a full kilogram and lift 250 grams of payload. They will also go up to 20 – 30 km.

The cold weather balloons can carry a good kilogram and are made to go to the stratosphere (from 10 to 50 kilometers high where temperatures can be lower than -75 degrees C)

The balloon I used for MSP-1 & MSP-2 was a Kaymont Cold Weather KCI TX1200 balloon.  It cost about $105 (shipping included). I now use Hwoyee‘s 1600g balloons from Scientific Sales.

Kaymont’s balloon has a 12 cm long thick neck used to fill the balloon and attach the load lines.

When you manipulate the balloon, I highly recommend that you use latex gloves. It’s not to protect you but to prevent you from damaging the balloon with your nails and your sweat.

Remember: The balloon is very fragile. Find an area that’s very protected from the wind otherwise, it will bounce against you and the ground a lot and may be damaged before even launching it. Because it’s so fragile, you must launch it from somewhere with no possible contact with fences, trees, phone or electric lines.

How much Helium?

To fill the balloon, I highly recommend to use Helium over Hydrogen.

Hydrogen is lighter than Helium but the difference is ridiculous when you think about the risks. Hydrogen is extremely flammable whereas helium is an inert gas. Moreover Helium is easy to obtain and you do not need any special permits if you decide to start transporting several tanks of it around in your truck.

You can find helium tanks at local party stores or welding supply stores.

I found mine at SF Party in San Francisco.

One cubic foot of helium will lift about 28.2 grams. Kaymont recommends a gross lift of 3440g. So I needed 3440/28.2= 122 cf of helium. I took the 244cf tank + a dolly. It cost me $148. Be careful the tank is very heavy.

How to to fill the balloon from the Helium Tank?

Helium tanks from party stores usually come with special regulators for party balloons. It’s not the best thing in our case because the flow rate is low, you need to constantly bend the valve  and consequently it slows the filling process down.

The obvious issue is to link the small regulator’s mouth to the 3 cm wide balloon’s neck.  You need to build the joint/adaptor yourself.

You need:

To make sure the dimensions are correct, bring with you the balloon and the regulator when you go shopping. You can find the materials at Lowe’s or Home Depot.

The reason you want to a long plastic tube is to be able to inflate the balloon on a clean plastic cover away from everything.

The balloon’s neck is about 3cm (1.2 inch) wide, a 1inch wide PVC tube is large enough to keep it tight. Make sure to secure it with 2 tie wraps and a solid pair of hands.

Since the inflating process can take up to one hour, the person responsible for the balloon can get very tired. The reason you want an Elbow shape is to attach the inflating balloon to something heavy to prevent it to fly away and to measure the lift.

How much Helium is enough?

The tank regulator may or may not have a volume gauge. To measure the balloon’s lift, I found very hard to use a hanging scale. It’s great to weight your payload but absolutely not convenient to measure the lift. The scale is not accurate if there is any wind. It requires at least 2 person and tends to recalibrate itself each time you switch it on.

The best way I found was to attach the regulator joint to a jug of water. Add the desired amount of water to match the lift (3440g -> 3.5 liters). When the balloon is at equilibrium you know you have reached the desired lift.

Remember: It’s always better to have more lift that not enough. (More Lift = Faster ascent rate = Shorter flight time = Fewer problems)

About sealing the balloon, Dave Mullenix has the best instructions: using tie wraps or heavy twine, tie the balloon neck off tightly above the filling adaptor. Remove the joint. Tie the neck again, four to six inches below the first piece of twine. Tie your payload cord to the neck between these two pieces of twine. Now bend the neck over double and tie it again, twice. You will now have the neck of the balloon bent over double, with the payload suspension cord nestled in the bottom of the bend and the whole thing securely tied.

You’re ready to go over your pre flight checklist.