Anyone Can Launch a Balloon to Fly Over China

Anyone can launch a balloon to fly over China, including you and me. We do not need to ask for permission from the US government. In some cases, we do not even need to tell the authorities. For around $100,000 or less, a normal person can use a balloon to take high-quality pictures and listen to radio signals over the Chinese mainland. For just $1,000, a smaller balloon can fly over China and gather some information. You could even put your name on the side of the balloon!

In May 2022, I went with one of my sons to the Dayton Hamvention in Dayton, OH. This yearly convention is the largest amateur radio convention and show in the US. One of the people we wanted to meet there was Tom Medlin. His ham call sign is W5KUB. Google him. I have been interested in balloons for many years and Tom is probably the foremost expert on high altitude balloons carrying amateur radio and other payloads. Here are a few thoughts based on my research and Tom’s seminar:

Regular birthday balloons made of mylar, like the ones you can buy at Party City, can travel around the world. They are usually 18 to 24 inches in diameter and filled with helium. If you choose carefully, you can attach things like solar panels, a computer, GPS, and a low-powered shortwave radio to the balloon. They may even have a temperature sensor. You can find plans for this online.

The amount of helium in the balloon and the weight of the electronics are carefully chosen. The relationship between the two determines the cruising altitude of the balloon. There are fairly simple mathematical formulas for this. Typical balloons intended to float around the world fly at around 40000ft above the ground. This keeps them above most thunderstorms but still in the upper currents of the jet stream. The jet stream propels them naturally. No engines or fuel are required.

Balloons like that, launched from the US, will almost always fly over the Atlantic, through Southern Europe or North Africa, through the Middle East and Central Asia. Before crossing the Pacific and reappearing over the United States, they fly over China. My United States shot down a balloon over Alaska with this flight pattern on February 10, 2023. Another was shot down over Canada the next day. Each shoot down costs well over $1M.

Remember that there are no permits required for such a balloon. And there is no requirement to notify the government. Design it and then let it go. That’s it! The total cost is $1,000 or less.

Larger balloons are also readily available for purchase online. The larger the balloon, the more helium it can hold. The more helium it can hold, the larger the payload can be. Huge balloons are available for $100-$200. A larger balloon could carry a high-resolution camera, purchased from Amazon, and even a radio receiver capable of recording a wide swatch of frequencies – from Chinese TV to cell phone and military communications. Decent receivers are also available on Amazon for less than $100. Most are Made in China and are marked that way. US made ones are available, though.

Several people have spoken with me about the possibility or need to jam the radio signals from spy balloons. If there is interest, I am happy to explain why jamming is certainly possible but with severe damage to our own communications infrastructure. Having said that, the wind patterns for balloons flying around 40000ft reduce the need to even have communications on the balloon. Since the winds blow the balloon back over the United States after they have circled the earth and flown over China, a balloon would simply have to detect its re-entry into US air space and then deflate itself. Simple. Once the contents are retrieved, high-definition pictures of China as well as recordings of Chinese communications could simply be read from an SD Card.

Before concluding, I must mention balloons that operate at higher altitudes. To operate at a higher altitude, a balloon either has to be bigger, or its payload weight has to be reduced. Based on information gathered during the on-going flight of the W5KUB-112 balloon at 50000ft, winds at this altitude are very light and the direction is variable. Balloons at this altitude drift all over the Northern Hemisphere at slow speeds. A medium size balloon could easily be steered with a propeller from a drone, powered by solar panels. The cost to do this would be low and the components are readily available at Hobby Lobby or online.

I personally have the technical knowledge to make something like this with limited help from others.

All of the parts are readily available in the US.

Parts are available in most countries in the world to do this.

Undoubtedly, many private, commercial, and government balloons are currently aloft. And convention has always been to allow them to stay afloat and do whatever they are doing. The bottom line is that any private citizen can send a balloon around the world – and across China, North Korea, Russia, or any other place of interest. What intelligence the balloon gathers all depends on how much the hobbyist is willing to spend. And the balloon owner can even decorate the balloon with letters or words in any language.

Battery Voltage vs Percent Charged

The charge state of a lead acid battery (% charged) can be estimated from the voltage measured at the terminals of the battery.  The chart below shows the relationship.

First, it is important to understand the terminology.  “C” is the capacity of the battery in amp-hours.  For example, this battery has a rating of 215AH when discharged over 20 hours.  Note:  The Duracell GC2 battery is a 6V golf cart battery.  So, the chart is applicable to two of these batteries connected in series.

For easy reference, here are calculations of the currents shown on the chart:

Curve Current Draw/Charge Approximate Wattage Draw/Charge

Here are several examples of interpreting voltage:

Scenario 1

It is night and no solar energy is available to charge the battery.  Several small pieces of electronic equipment are connected to the battery.  They consume about 25W or so.  The battery voltage is 12.5V.  This means that the battery is about 60% charged.

If the battery voltage were 12.0V, then the battery would only be 10% charged.  Likewise, if the voltage were about 12.7V, the battery would be pretty much fully charged.

Scenario 2

It is night and no solar energy is available to charge the battery.  An inverter, which draws about 2A (~25W) of current is powering a small air conditioner and 6 high intensity recessed LED lights.  The air conditioner consumes 500W of power and the lights consume 75W.  So, the total power drawn from the battery is about 600W, which is between the C/3 and the C/5 curve – but closer to the C5 curve.

If the battery voltage measures 12.0V, then the battery is almost certainly fully charged.  If it measures 11.5V, the battery is about 60% charged.  And if it measures 10.5V, it is somewhat less than 10% charged.

Note that discharging a battery at the C/3 or even the C/5 rate decreases the life of the battery.  C/10 or C/20 is much safer.  In addition, battery life is shorted by discharging a battery below 50% of its capacity.  600W represents 50A of current.  So, using a Duracell G2 battery pair like this for more than two hours decreases life because of the discharge rate as well as discharging too deeply.  For usage such as this, it is advisable to use at least 4, if not 6 of these batteries, in series/parallel combination.  6 batteries would reduce the discharge rate to C/16.7 and would increase the safe usage time to about 6 hours.

In the chart below, the area in green represents the safest discharge rates and amounts for best battery life.  Note that battery terminal voltages under 12.0V are always suboptimal.

Scenario 3

It is a sunny day, nothing is using power from the battery, and a solar panel system is producing about 10A of current.  The voltage at the battery terminals measures 14.0V.  This means that the battery is approximately 90% charged.  On the other hand, if the voltage at the battery terminals measures 13.0V, the battery is approximately 50% charged.

Vertamax 3000W Inverter Review

I have used the Vertamax 3000W inverter on and off over the past two months with various types and configurations of solar panels and batteries. It performs well under a load of up to 1200W and probably performs well beyond that, although I have not tried. It is well built.

One thing that I have noticed is that, as stated in the description, it does shut off under low voltage. However, the shutoff voltage is around 11.8V or 11.9V – not the 10.5V (+/- 3V) shown in the instruction manual. Of course, this is good for a lead acid battery under load because the inverter will shut down before the battery completely runs down. Running the battery completely down will dramatically shorten its life.

The description/manual also states that “When the input voltage rises to approximately 11.4 – 11.9V DC, the inverter restores to normal operation and the red FAULT indicator will turn off.” This is not correct. Even after a battery is fully charged to 12.9V, the fault like still blinks and the inverter does not come back on. I called WindyNation and spoke with a knowledgeable gentleman who verified that the only way to get the inverter to resume normal operation is to manually toggle the ON/OFF switch. This means that, at a remote unmanned site, a low voltage condition will cause the power to be off until someone can visit and reset it.

WindyNation told me a good rule of thumb to minimize the likelihood of batteries being run down below 50% – which is about as low as it is safe to go without damaging lead acid batteries. The rule of thumb is that choose a bank of deep cycle batteries that have as many amp hours as your solar panels have wattage. For example, six 100 watt solar panels should have a battery system rated at 600AH. This is general guidance and the exact ratio depends on the amount of sunshine in your location and the season. But, my experience over the past few months in North Texas is pretty much in line with this recommendation.

Renogy Rover Monitoring with the Raspberry Pi

The information, below, was posted on the Renogy Forum by a user with the screenname lindsey.  The forum recently moved and the documentation was temporarily lost.  The information was reposted; but I wanted to put it here for easy reference in case it gets lost again.

This information is about connecting the Renogy Rover to the Raspberry Pi for monitoring.

First, here is a general link discussing connection of the Raspberry Pi to a solar battery charger.

Here is the wiring diagram that the Renogy Forum post provided:

Here is a sample output on an Android from the Python scripts.

Here is a sample database query.


The diagram, below, is a diagram of how the Rover’s RJ-12 port splits out into RS-232 signals.  Note that only TX, RX, and ground are used.

The link below was put together by lindsey.  It describes the needed hardware (in addition to the Pi) as well as the general functionality of the Python code.

Raspberry PI Writeup

Finally, here is a zip file with the Python code.  Unfortunately, I do not have a way to contact lindsey.  The code comments say that her name is Lindsey Crawford.  If anyone knows how to contact her, please let me know.


Solar Panel Performance

Here is a link to a website put together by the California Energy Commission to provide evaluations of solar panel performance:

I find it interesting that there does not seem to be much of a difference between monocrystalline and polycrystalline panels.   Both seem to produce about 90% of their rate values under standard test conditions of:

  • 20C air temperature
  • 1 meter/sec wind speed (2.2mph)
  • 10 meters (33 ft) above the ground
  • Air mass of 1.5
  • ASTM G173-03 standard spectrum
  • 1000 watts/sq meter solar irradiance

Ok.  So, how is that practical?  Well, here is a calculator, based on historical data, of how much irradiance is expected in a given location.

For Dallas in September, expected solar irradiance of a South facing panel is 4.96kWh/sq meter/day.  So, it appears that a real world 100W panel should be expected to produce 9% of this amount – or 446Wh.

To put this in perspective… 446Wh would allow a person to use 18.6 watts of electricity constantly over a 24 hour period, assuming that the system has a battery to store energy for use at night and cloudy days.

Note that solar irradiance is about half that amount in the winter.

Bottom line:  An ideal 100 watt solar electric system in Dallas allows a person to constantly use about 18 watts of power during the month of September; about 9 watts in the winter.  Real world results are almost certainly less.