Introduction: Low-cost Near Space Without HAM Radios or Cellphones

After researching near space balloon projects and launching two of my own I've found that the major hurdle is in communication with the balloon payload. Many near space ballooners are using HAM radio equipment to track their balloons through triangulation or APRS data transmissions. That's all well and good if you have a HAM license and the experience to know what equipment and frequencies to use. The non-HAM ballooners are using cellphones or cellular modules to send SMS messages for tracking the flight. Cellular modules work pretty well up to 40k feet altitudes with good external antennas, but above that altitude there will be no communication from the payload. It's a bit nerve racking not knowing what's going on with the payload for more than half of the flight. Cellular coverage isn't always available in the best launch locations in the U.S.

I discovered that the communications challenge is very simple with the right hardware. The XTend900 radio from Digi ( ) and a high gain patch antenna ( ) can keep you in communication with the payload for the entire flight and can even provide enough bandwidth to transmit small pictures. This instructable will focus on the minimum set of hardware to get you into near space, capture those spectacular photos, and track your payload to recovery.

For information on my last near space flight, Night Sky, visit

Step 1: GPS Tracking

Your near space project will be a disaster if you don't know where the payload lands. The easiest way to track the flight is with a GPS receiver. Not all GPS receivers are equal, though. Some receivers can track 30+ satellites at a time, report the position 10 times a second, and output the raw data from the satellites. We aren't making an unmanned aerial drone, and even if we were there are only 12 GPS satellites in view of a hemisphere at one time...don't get suckered into buying an expensive GPS because the numbers are impressive. The one important thing is to get a receiver that can operate above 60k feet altitudes. Many receivers stop working above that altitude due to international export restrictions and what not.

For my projects I have used the GS407 receiver ( This is a small receiver with a helical antenna that gets great reception. The U-Blox chipset can interface with the U-Center software to set all the device parameters and update the satellite almanac for faster startup times ( Using U-Center you can also update the "dynamic platform Model" which allows this receiver to operate above 60k feet. You must set the dynamic platform model to "Airborne < 2g" or higher to operate above 60k feet. I'll discuss how to change that setting after we have the GPS and radios connected.

For now all we have to do to the GS407 is solder 4 wires on. In the picture you can see that the serial communication comes out of pins 3 & 4 of the U-Blox module. Pin 6 is VCC or power and pin 14 is ground, which you also need as a reference for the serial bus. Solder a wire to each of these pins, you should be able to do it without a microscope using 30 gauge solid core wire. If you use 4 different color wires you'll make your life easier, too. If you feel nervous about soldering these wires you can buy a breakout board ( for the GS407 that will provide slightly larger holes to solder to, but you're still going to have to solder.

Step 2: The Radio Communications

Radio communication is a difficult thing on Planet Earth. Radio waves won't travel through water or dirt very well (this includes hills and plants). To keep communication with an object you typically need "line-of-sight." The further away from an object you get the larger window you need to have line-of-sight. This is what's known as the Fresnel zone ( Luckily for us the balloon flight will be high in the sky and the only challenge will be staying close enough to the balloon's ground position to have line-of-sight when it lands. If you aren't close to the payload when it lands you may have to search a long time to find it because you won't have the exact GPS location of where it landed.

My last balloon used the XTend 900 radio module from Digi ( as the main communication system. This 1 watt, 900 MHz radio allowed me to keep communication with the payload for the entire flight while getting flight data updates once every 5 seconds. The XTend 900 can interface to the XCTU configuration software to change the serial data rate in a user friendly GUI way (

On the PC side of things you need to connect the XTend 900 to the PC's USB port. The best way to accomplish that is to get the uUSB-MB5 USB to serial converter from 4D Systems ( and the XTend breakout board from Sparkfun ( Solder the breakout board onto the XTend 900 or buy the proper connector. Then solder wires from the uUSB-MB5 to the breakout board in this order:
-uUSB-MB5 RX to breakout DO
-uUSB-MB5 TX to breakout DI
-uUSB-MB5 GND to breakout GND
-uUSB-MB5 +5V to breakout VCC
-On the breakout board you will also need to solder a 10k resistor between SHDN and VCC.

The balloon payload is similar and you'll need another breakout board to make things easy. Solder between the GS407 and XTend 900 breakout board like so:
-GS407 RXD to breakout DO
-GS407 TXD to breakout DI
-GS407 GND to breakout GND
-GS407 VCC to breakout VCC
-On the breakout board you need to solder a 10k resistor between SHDN and VCC

We almost have a fully functional radio link between the GPS and PC. Keep going to the next step to fire it up!

Step 3: The Power!!!!

For my Night Sky balloon payload I discovered lithium thionyl chloride batteries. These batteries have an amazing power density, but aren't rechargeable like lithium polymer batteries are. You'll only need one LSH14 battery from Saft ( Make yourself up a connector to attach and detach the battery from the XTend 900 breakout board on the balloon payload. Solder one wire of the connector to the VCC on the breakout and the other to GND. Do the same on the battery with the other side of the connector.

Connect the other XTend 900 to your PC through the USB port and bring up U-Center. In U-Center open the text console by selecting View->Text Console. Then connect to the receiver by selecting Receiver->Port->(whatever COM your XTend 900 is on). When you connect the battery the NMEA sentences should start showing up in the text console if everything is correct.

At this point you can use U-Center to change the GS407's configuration. Select View->Configuration View and a whole host of options will show up. The one you must change is in the NAV (Navigation). Click on "NAV (Navigation)" on the left and select "6 - Airborne < 2G" from the Dynamic Platform Model drop-down box. Now click Send at the bottom of the window and you're ready to operate above 60k feet!

Step 4: Pictures

I won't spend too much time on pictures because there's a whole Wiki about Canon and the CHDK open source firmware ( On Night Sky I used the Canon SD1100 camera set to infinite focus and pictures on a 6 second interval. You can do much more interesting things with videos and focus, but I'll leave that for you to investigate.

Step 5: Radio Antennas

When you're working with the payload there probably isn't any reason to use antennas on the radio. In fact using high gain antennas too close to each other could cause the receiving radio to be damaged! So, when working with the payload in the same room as your receiving PC, keep the antennas disconnected.

The best antenna option I've found is a high gain patch antenna from L-Com ( This antenna gives an 8dBi gain and radiates in all forward directions. There's no need to worry about which direction the antenna is rotated as long as the fronts of the antennas are pointing at each other. At close range the fronts don't even need to be pointed at each other (very helpful when finding the payload on the ground). With this setup I tracked the Night Sky payload to 116,750 feet altitude and over 30 miles ground distance!

The antenna also provides a nice base to build your payload on. You want the antenna pointing down towards Earth during flight, so just glue your GPS, radio, and camera to the back side, get some "foam core" (it's poster board with a small layer of foam on the inside) to enclose the electronics in (not the antenna), and wrap the foam core in a space blanket. Leave an access panel to plug in the battery and setup your camera to start taking pictures. Your payload is now fully assembled!

Step 6: Tracking

Tracking the balloon flight is going to be very easy since we're getting standard NMEA sentences from the payload into the serial port of our PC. You really should be using a laptop and a power inverter in your car. Get a friend to be your navigator, don't be foolish and try to drive while watching the laptop screen...

To track the flight use Google Earth and have it use the XTend 900 radio as a GPS device. Simply select Tools->GPS. Then click the Realtime tab. We're using the NMEA protocol, so select that. Set the Track point import limit to the maximum (currently 100) and the Polling interval to 1 second. You can have the map center on the balloon's position by checking "Automatically follow the path" but it may be easier to navigate without that. Click Start and Google Earth will search through all the COM ports looking for your GPS receiver. If the XTend 900 is plugged in and the payload is operating you'll start getting a track of your payload location.

You may be thinking, "How am I going to use Google Earth in the car without an internet connection?" The answer is that Google Earth will cache up to 2 GB of data for you. If you know the general area of where you're going to be driving, just zoom the map into that area until you see the roads and scroll around to cover the expected balloon flight path. Now you'll be able to see those maps the next time you open Google Earth even if you don't have an internet connection. How do I know where the balloon is expected to go? Read on to the next step and find out!

Step 7: Flight Predictions

This is a surprisingly simple step. Go to

- In the "GFS model time" drop-down, pick the time that most closely matches your launch time (note the times are in Zulu).
- Leave the forecast period on Analysis.
- Enter the decimal degrees for the latitude and longitude of your start location (you can get these from Google Earth, look at the bottom of the screen while moving your cursor over the map).
- Pick the height you expect your balloon to go (this is usually given by the balloon manufacturer).
- Lastly select GoogleEarth KML as the output and click Submit. You'll get a KML file that you can open in Google Earth and see the expected flight path.

Note that this prediction assumes a 1000 foot per minute ascent and descent rate. The altitude in the KML file also appears to be shown in meters, but the text labels are in feet...

Step 8: Balloon, Parachute, and Helium

I highly recommend Kaymont for latex sounding balloons. Their 1200 gram balloon will get this payload well above 90k feet and that's pretty good for a first time balloon. Check them out at

The parachute is somewhat of a personal choice, but I like the x-type parachutes from Top Flight Recovery ( Have a look at their "Descent" page and pick a parachute that fits the weight of your payload. The new automated post office kiosks at the USPS are a great way to weigh your payload for free!

Now you have three separate parts to attach. You need to attach the parachute to the payload and the balloon to the parachute. The chute should always be open and ready to slow the payload's descent in case the balloon bursts. 50 lb test fishing line is the easiest way to attach everything. Find a convenient way to tie the parachute loops to the payload using one strand of fishing line about 4 feet long. Next loop an 8 foot strand of fishing line through the x-type chute. This loop should catch the X in the armpits and not prevent the chute from opening all the way when there is no tension on the loop. When your balloon is filled you'll attach this loop to the balloon and everything will be ready to go.

Helium can be found anywhere there are welders and sometimes at party stores. The helium tanks from party stores typically have a small rubber outflow valve that is very annoying. You must hold the valve to the side and it takes a long time to fill the balloon. Welding bottles and industrial bottles don't have that type of valve, but you must buy your own regulator and hose. Don't try to fill the balloon without a will pop the balloon. I like to use the industrial gas bottle to reduce the balloon filling time from 30+ minutes to less than 5.

Filling the balloon to the proper amount is pretty easy. To get the 1000 feet per minute ascent rate you need about 1 pound more lift than your payload weight. So, make a temporary attachment for your payload and a 1 pound girly weight (could be manly too, but the extra hair is disgusting). Fill the balloon until it can easily lift the payload and the extra pound. Zip tie the top of the balloon's filler neck, zip tie the bottom of the filler neck, attach the loop of fishing line from your parachute to the filler neck between the two zip ties, fold the filler neck over the fishing line and zip tie the whole thing again. Your balloon is now attached to the payload and you're ready to launch!

Step 9: Bill of Materials and Final Thoughts

Bill of Materials:
1 - GS407 GPS Receiver
2 - XTend 900 radio modules
2 - XTend 900 breakout boards
2 - L-Com 8dBi patch antennas with RPSMA connectors
1 uUSB-MB5 USB to Serial Converter
2 - 10k ohm, 1/4 watt resistors
- as many cameras as you want

As long as your payload weights less than 8 pounds and you aren't launching at night there are really no FAA restrictions. I highly recommend that you file a NOTAM (notice to airmen) report with your local air traffic control. You can find the NOTAM hotline phone number for your area by calling a local FAA FISDO office. You will need to know your launch location as a heading and distance from the closest airport and the maximum distance the balloon will travel over ground from that location. FAA regulations are always subject to change and I take no responsibility for you not checking on the latest rules. If in doubt call the local FAA office and don't launch until you're sure.

I hope this instructable helps you with your near space balloon. Please vote for me in the Celestron Space Challenge so I can continue to share awesome pictures and experiments from space with you! Don't forget to visit the Night Sky project website at to see pictures and data from my last near space balloon launch. Thanks!


NadeemH2 made it!(author)2017-06-04


Can I use XTend900 radio to keep providing me GPS data even the balloon goes 34 - 37 km up & then it burst. I mean can i use this radio till 37 km height. What if I am not precisely pointing my antenna towards it. Will it still work ? Please help

JoeyS46 made it!(author)2017-05-01

Thanks for the reply. I ended up using an iPhone and Find my iPhone app. Worked well! Watch video here:

NearSpaceLuke made it!(author)2017-05-01

I'd like to point out that not all places you would want to launch a balloon have good cellular coverage. If you launch in the middle of Montana you will probably not find your payload if cellular is your only communication method (talking from experience here).

JoeyS46 made it!(author)2016-05-25


Is there an easier/cheaper way to retrieve the location of my payload if I don't need to know its location at high altitudes? (If I only know it's location at the begginingg and end of the flight?)



JoeyS46 made it!(author)2017-05-01

Thanks for the reply. I ended up using an iPhone and Find my iPhone app. Worked well! Watch video here:

Mechtronic made it!(author)2017-05-01

Stupid but effective way is to throw on an old android phone with a power bank, it works but is heavy and inaccurate but you will surely find your payload

Jack+Issac made it!(author)2016-02-14

Hi, great work. I am curious that if I need to get a HAM license for the XTend 900 radio modules?

NearSpaceLuke made it!(author)2016-02-14

You probably guessed by the title that you don't. 900 MHz is in the ISM (industrial, scientific, and medical) band. This is an unregulated frequency. The down side is that someone else with a higher powered radio may interfere with your transmissions. The XTend 900 uses spread spectrum, so you should be able to receive no matter what.

Jack+Issac made it!(author)2016-02-14

So I don't need to get a license, right? But why doesn't it need a license? just because that spread spectrum won't influence other wave bands?

NearSpaceLuke made it!(author)2016-02-15

You don't need a HAM license. As to just isn't required. Has nothing to do with spread spectrum.

Jack+Issac made it!(author)2016-02-15

I am very appreciate about your assistance. A simple question, I saw other people who launch HAB usually use Arduino or Raspberry Pi. Why didn't you use them?

NearSpaceLuke made it!(author)2016-02-15

Since this design only needs to transmit the GPS, there is no need for an extra processor. If you want to add on sensors and transmit that data, then you will need to read all sensors into a processor and compile a serial data stream to send over the radio. Launching and recovering a balloon is much more difficult than you expect. Be sure you take your time and do your research. It's very deflating when you lose a $500 payload because of a silly mistake.

Jack+Issac made it!(author)2016-02-17

I am very interested in HAB, and I really wanna launch this thing. So if there is personal email or something else that I can contact with you? I may encounter some problems in the future when I make my own design.

Jack+Issac made it!(author)2016-02-14

and I don't either get a license from FAA as long as I make sure the weight of the payload is below 8 pounds?

NearSpaceLuke made it!(author)2016-02-15

There are some rules about unmanned balloons in the FAA regulations. I can't give you the answer for your particular situation, but typically a balloon under 8 pounds with a tether that breaks at 50 pounds pull does not need FAA approval. Be sure you do not launch or land within 5 miles of an airport, and you should file a NOTAM report. You can google search for the NOTAM hotline number in your region

joe.briggs.752 made it!(author)2015-04-27

JoshuaM1 made it!(author)2014-10-12

So the GS407 is now discontinued. Any alternate advice you might recommend? I assume hookup will be different as well... Great work by the way!!!

NearSpaceLuke made it!(author)2014-10-13

You'll have to do your homework on this one. The U-blox chipset allows you to get position above 60k feet. That's really the only thing you need to find in the new GPS receiver. Good Luck!

007dna made it!(author)2014-09-16

Hi, great ible. Quick question: I am wanting to have a photo stream transmit to me from the balloon during flight. I am very new to this area, what do I need for that? I assume I can't just hook up a camera to the breakout, I need to connect it to a Pi or Arduino. Also, what is the point in having the radio module on the ground? You are not transmitting TO the balloon, so all you should need is just a receiving antennae....

Help is greatly appreciated, thank you.

NearSpaceLuke made it!(author)2014-09-17

I give the same advice to everyone doing this for the first time. Keep it simple, or you'll lose a lot of expensive equipment. Balloons seem very simple, but you'll be panicking on launch day. Launch your first balloon with just the tracking information coming at you. Once you can track and find your balloon on the ground, then move on to multiple data streams.

When you get to trying to transmit the picture, you'll find you need to convert the picture to a serial data stream. That is going to be a lot of data, and the data rate you get over a 40+ mile radio link is very slow. You're not going to be getting real time video or more than a picture a minute with inexpensive radios. Do your research on picture formats and baud rates. A little math will tell you just how long it takes to transmit a picture.

As for having a transciever on the ground, it was easy to write the firmware once and use the same module on the balloon and on the ground. Keep it simple, reuse known equipment and code, things will fail on launch day, and with some luck you'll find your first balloon.

afry2 made it!(author)2014-04-14

I am running through these links and I have come across a bad one. Is there a website that I can be directed to instead of


NearSpaceLuke made it!(author)2014-04-15

cvsa made it!(author)2014-02-17

That tracking software you use it is accurate? I am North West of you in Southern BC. I have played around with this other website but it gave me a completely different flight path from the one that you use. I figure if it is accurate for you it should work for me here too.


Great instructable!

NearSpaceLuke made it!(author)2014-02-17

I found their prediction to be right on the money. What wasn't on the money was my ascent and descent calculations... The balloon ended up traveling twice the distance over ground because the ascent rate was half what I planned for.

Wind patterns at different elevations and different locations are extremely variable. You should run predictions right up to your launch date just to see what might happen if something changes.

cvsa made it!(author)2014-02-17

Good to know. Any suggestions on adjusting for the ascent rate? Don't want to get caught in the mountains before I clear the valley bottom.

NearSpaceLuke made it!(author)2014-02-18

My ascent rate was 16.5 ft/s, which seemed to be half of what the prediction expected. If you can't get your balloon to the 33 ft/s that the model expects, then you should find a different predictor that you can adjust the ascent and descent rates. It's always good to get a second opinion, so using two models from different sources is a good idea anyway.

cvsa made it!(author)2014-02-19

Thanks again.

aallar made it!(author)2013-12-07

Also would the RFD 900 Radio Modem work instead of the xtend 900?

NearSpaceLuke made it!(author)2013-12-08

Looks like a good radio. I haven't used the RFD900, though. It has enough output power and TTL serial interface, which are the most important things for this application.

aallar made it!(author)2013-11-25

I have this for my gps would this work work instead of the GS407?

NearSpaceLuke made it!(author)2013-11-26

The description says it has been tested up to 88k feet altitude. I can't say for sure that it will work, but it seems like that should do for you.

rdx227 made it!(author)2013-05-07

Hello, I'm slightly confused as to which parts go onto the payload and which stay on the ground. From your descriptions I got:
- 1 GS407
- 1 breakout board w/ resistor
- 1 battery
- 1 antenna
- 1 XTend 900 radio module
- 1 uUSB-MB5
- 1 breakout board w/ resistor
However, the numbers don't match up and I can't seem to find where/how the second XTend 900 radio module connects. Any mention of the XTend 900 radio module only refer to it being connected to the PC. Could you please clarify?
If I follow the numbers you give in step 9, would that would suggest that the second antenna is on the ground connected to the XTend 900 radio and the second XTend 900 radio is in the payload, connected to the antenna (by the way, does that connection need an adapter?) and the breakout board. Since the GS407 also needs to be connected to a breakout board, do they share one?
Thank you

NearSpaceLuke made it!(author)2013-05-08

Step 2 says that you need to solder the wires from the GS407 to the XTend breakout board. I assumed you'd know to plug in your second XTend radio to that breakout board. You'll have this set of connections when you're done:
Balloon payload:
-GS407->XTend breakout->XTend radio->antenna

Ground Station:
-Antenna->XTend radio->XTend breakout->uUSB-MB5->Computer

omass made it!(author)2013-04-14

Hey! Great tutorial but I was wondering- how could get immidiate data transactions?
If you live on a small island, it tends to fly into the sea :P Any suggestions will be appreciated!

NearSpaceLuke made it!(author)2013-04-16

There won't be a way to stop it from flying into the water, unless you plan on a payload that can fly itself back to you (this is illegal in the U.S. without impossible to get waivers from the FAA).

You can increase the rate of NMEA messages from the GPS reciever to 5 per second on the GS407. Your best bet, if you must launch from an island, is to make your payload waterproof and buoyant. Do very careful flight plan predictions, fill your balloon precisely to get the rate of ascent right, pick your parachute for proper rate of descent, and get a fast boat so you can be at the landing zone before the payload lands. If you make the payload so it floats with the antenna facing up, you should be able to receive the signal well over a mile away from the payload. If the antenna is under'll never hear from it again.

Might be cool to make the payload an autonomous boat that drives itself back to the closest shoreline.

jkarimi made it!(author)2013-03-31

what was the peak altitude that your gps module was able to function at? Many of the devices I see on spark fun show that they have an upper limit of 18,000 ft due to COCOM regulations. Also the module you used is retired however there is a new model GS407, will the Airborne adjustment work on this new model?

NearSpaceLuke made it!(author)2013-04-01

The altitude measurements aren't actually limited by regulations and neither are the speed of movement...unless you plan on exporting your device outside the country (this statement is sure to get a bunch of comments from armchair experts). Using the dynamic platform setting of <2G airborne for the GS407 I had, you can get altitude readings from ground to the maximum theoretical GPS altitude.

With the new GS407, the setting is the same <2G airborne, but it is no longer under the NAV section. It's now in the NAV2 or NAV5 depending on the firmware version you have. You'll still see the NAV, NAV2, and NAV5 sections with any firmware version, so the easiest thing to do is set it in all three. Then it's done and you didn't have to worry about reading out the firmware version.

buckeyeguy made it!(author)2013-03-09

How about an update on connecting the GPS with the new model GS407. It doesn't look like the same connectors are available to solder to? I'm pretty much electronically challenged, so figuring it out is way beyond me.

NearSpaceLuke made it!(author)2013-03-10

Ok, so it's a bit easier now actually. The GS407 uses a better connector and Sparkfun is offering cables with the connector attached. Get yourself one of the cables. Then clip off the connector that you don't need, strip the wires for TX, RX, VBAT, and GND. Then follow the rest of the instructions in this instructable using those wires. You can see the pinout of the connector in the GS407 datasheet on page 4. Pin 3 -> RX, Pin 4 ->TX, Pin 6 -> VBAT, Pin 1 -> GND.

CaPhysicsTeacher made it!(author)2013-02-08

Dear NearSpaceLuke,
I am an AP Physics teacher. I want my students to do this as a class project. I will get all the materials then they will follow your instructions. Do you think 17-18 year old students would be able to complete this project?
Thanks in advance for your advice.

NearSpaceLuke made it!(author)2013-03-10

This is a good project for 17-18 year olds until the balloon gets in the air. Small balloons take about 4 hours to launch, track, and recover. The kids will probably get tired of waiting for it to land. If you aren't paying attention to the balloon and following it closely you may not be able to recover it.

ninfan1 made it!(author)2012-10-20

Hello everyone. I've been researching and preparing for my first launch for weeks and recently have been scouting launch and landing sites. I'm working with the CUSF Landing Projector program now and have a minor question. When inputting my launch date, it already shows the date one day ahead of where I'm located now (I live in Florida ). I'm having a few issues converting EST to UTC time when it crosses over to the next day. For instance, if it's 9 pm here in Florida right now and I'm planning on a 10 am launch, what would I need to do. How far ahead will the program let me predict? Thank for any insight.

** I'm just running simulations to get used to the program for now as I research and build my payload etc. I do seem to be able to run current simulations if I leave the date as it is and launch tiem by default.

ninfan1 made it!(author)2012-10-21

In regards to the CUSF Landing Predictor, I'm following the step by step instructions I saw on this page and inputting my payload weight info etc correctly I believe. The projector y path and landing site look correct, but when compared to the wind directions I see on local Dopler it seems to be going to wrong direction. Is this normal, or am I doing something wrong. Local wind directions are out of the NE which I would think would make my payload travel SW. Thank you for any insight.


ninfan1 made it!(author)2012-10-21

Ok, so I apparnetly was not looking at the jetstream wind direction! Looking closer at my projected path, I now can see the lower level winds effecting the path correctly and then the upper level winds taking over. Learning more each day:


robotkid249 made it!(author)2012-08-23

If you're interested my new instructable on near space balloons is published!

Dg613 made it!(author)2012-02-23

Hi nearspaceluke

It would be great if you help me build the tracker. I am based in Australia and would love your input.

Up to it?

tstowe made it!(author)2012-02-07

Here is a better site:

NearSpaceLuke made it!(author)2012-02-08

I actually don't like that site at all. The predictions come out just fine, but the user interface is garbage. The plot track to Google Maps never works, either.

tstowe made it!(author)2012-02-08

That's the only one I use. It's usually VERY accurate. I've had it the prediction be off by less than a mile. I also like that you can look at the raw data and see lat., long. and alt. throughout the prediction (so I can compare it to the actual numbers during the flight).

I also don't think I've ever had a problem looking at the prediction in Google Map.

Jack+A+Lopez made it!(author)2011-08-23

Is there a reason why you are using helium, rather than hydrogen, as the lifting gas? I kinda thought that H2 would be cheaper, and provide more lift for the same volume balloon, but maybe there's some other reason, like maybe your local welding store won't sell you hydrogen.  Just curious about that part, I mean your choice for lifting gas.

About This Instructable




Bio: Just your typical electrical engineer with an addiction to space and the Cabinet Mountains Wilderness.
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