Why don’t WindBorne balloons pose a risk to airplanes?

The quick answer is our constellation of Global Sounding Balloons (GSBs), which we call WindBorne Atlas, doesn’t pose a threat to airplanes or other objects in the sky. It’s not only highly improbable that a WindBorne balloon could even collide with an aircraft in the first place; but our balloons are so lightweight and safe that they wouldn’t impact an aircraft even if they did interact.

Before we dive into collision physics, it’s worth zooming out to note that we’re fully airspace compliant, domestically and internationally (more on this in our next FAQ). We also go above and beyond to be good stewards of the sky: we take extra measures to coordinate with airspace authorities when we launch balloons. We also openly share the real-time location data of our aloft constellation with our government and regulatory partners, so they can easily and precisely view our balloons’ location at any time.

Now, back to the question of aircraft: let’s first dig into the probability (or rather, the improbability) of a collision with a WindBorne balloon. Our balloons have the unique ability to navigate the atmosphere for weeks (or even over a month) without any propulsion. (This is part of what makes our atmospheric sensing system the most sustainable and cost-effective). However, even though our balloons are aloft for long periods of time, the overall density of our balloon volume relative to the size of the atmosphere is extremely low. What’s more, our balloons only fleetingly and infrequently intersect with the altitudes at which aircraft fly (between about 30,000-40,000 ft), dropping the probability of path intersection even further.

In the very unlikely event that a balloon and airplane were to get close, generally the propulsion of the airflow around the plane alone would rapidly push a light object like a WindBorne balloon away (at its heaviest, a WindBorne balloon is about 4.4 pounds, or 2 kg). By comparison, the average Canadian goose weighs 8.5 pounds).

Now, for the sake of exploring the scenario, let’s unpack what would happen in the extremely unlikely event of an actual collision with an aircraft. Thankfully, it’s pretty simple: our balloon would disintegrate upon impact, without causing damage or any impactful kinetic force to the vessel.

This is due to the light, dispersed composition of both the ballast (the heaviest part of our balloon, which is primarily sand housed in a thin film), and our main, made of the same thin, transparent film we call the envelope (the “balloon” part of our apparatus). This film is just 20 microns thick, less than half the thickness of a single human hair. At the point of a collision, it’s worth noting that our balloon would likely weigh even less than 4 pounds, and potentially much less. Our balloons become lighter throughout flight because they drop sand ballast and vent gas to autonomously change altitude and navigate to their target location(s).

This interaction would be different, for example, if the object were a hard, dense solid, like a brick or ball, and not a balloon. However, our unit is more akin to one of the 40 million ducks worldwide, which weigh a similar amount to our balloons and share the sky with aircraft every day.

Importantly, our balloons also do not fly in flocks, unlike birds. They always fly solo, which means they don’t carry the same potential for hazard that multiple birds do: the ability for multiple strikes to one aircraft. So rest assured, the 2009 Hudson River plane landing incident couldn’t be repeated with a WindBorne balloon: our balloon is 100x lighter than even a relatively small flock of geese. (It’s worth noting we also have no incentive to increase our balloon density to the point where a “flock effect” could be problematic. That level of balloon density would be redundant for data collection.)

As an extra precautionary measure, we also don’t fly at low altitudes around highly populated areas. (We’re also not incentivized to do this. Weather measurement systems like ground stations are usually present throughout densely populated areas).

Still after 1,000+ launches, a WindBorne balloon has never collided with an aircraft (or any other vessel, and remains highly unlikely to in the future).

What does it mean that WindBorne is airspace compliant?

We’re proud to be fully compliant with both U.S. airspace regulation (via the Federal Aviation Administration’s (FAA) Part 101), as well as international airspace regulation (via the United Nation’s International Civil Aviation Organization’s (ICAO) "Rules of the Air,” Appendix 4). Both entities set safety rules and guidelines for aircraft, as well as the operation of free-floating balloon systems like ours.

In addition to following FAA and ICAO rules and recommendations, we go above and beyond to be good stewards of the sky. For example, we maintain active lines of communication with the FAA to ensure our operations satisfy all relevant regulatory requirements. We also provide government partners with direct access to our comprehensive, real-time balloon tracking system via our proprietary software, WindBorne Live. (WindBorne government partners and collaborators can contact us for access here.) Additionally, though not required, we frequently issue Notices to Airmen (NOTAMs) and coordinate with local air traffic control when conducting launches to keep relevant partners informed of our operations.

So, what’s the gist of balloon requirements? WindBorne’s Global Sounding Balloons (GSBs) fall under a few categories. First, they’re meteorological balloons, meaning they’re used for gathering weather data. Second, they don’t have “active propulsion,” meaning our balloons don’t use any type of motor or onboard fuel to fly. Instead, our balloons are powered through a combination of a small solar panel and the autonomous ability to surf the wind by changing altitude by dropping ballast or releasing gas.

For balloons without active propulsion (like ours), the FAA and ICAO define a threshold for the payload weight, below which the balloon is considered light enough to not pose significant hazards in the air or on landing. If the balloon is below this weight, which is less than 4 pounds (2 kg) in the U.S. and internationally, then the balloon falls into the exempt category. (By comparison, the average Canadian goose weighs 8.5 pounds). FAA and ICAO regulations also deem a balloon exempt if it has a payload weighing less than 6 pounds (3 kg) and has weight-to-size ratio of less than three ounces per square inch (13 g/cm^2) on any surface. Per these rules, WindBorne balloons fall into the exempt category globally (barring any unique, temporary restrictions that sometimes affect specific regions).

Why is the presence (or lack) of active propulsion so significant? Active propulsion can make unmanned aerial vehicles (UAVs) like drones more dangerous for several reasons:

  1. Active propulsion usually requires high-speed spinning blades, which present a number of safety hazards.
  2. If the active propulsion system fails or loses power, the unmanned aerial vehicle (UAV) would fall out of the sky and could cause damage to something upon landing.

By contrast, a balloon does not require any active power to stay aloft.

How does WindBorne approach flying over country lines? ICAO permits lightweight, meteorological flights like ours over countries other than the country of launch, as long approval for a launch was obtained in the launch country. WindBorne routinely and successfully receives this approval across all of our international launch sites, which span three continents.

It’s worth noting that the suspected China balloon that the U.S. Air Force shot down in February 2023 was not in compliance with ICAO regulations, which is why it caused an international incident. It was an entirely different type of balloon than WindBorne’s. The China balloon’s payload was estimated by the North American Aerospace Defense Command (NORAD) to weigh several thousand pounds, about 1,000x heavier than WindBorne’s balloon.

Incidents like this underscore why WindBorne is proud to make easy-to-use, live balloon tracking software available to government agencies like NORAD. We believe it should be easy for government and regulatory partners to track the location of all balloons and are excited to continue supporting this transparency.

Regulations can always shift over time; we at WindBorne will always be committed to being fully compliant and communicative stewards of the sky.

How does WindBorne track its balloon constellation and share location data with government partners?

At WindBorne, we are deeply committed to offering transparent, seamless visibility into the location of our active and past global sounding balloons (GSBs) to our government partners, regulators, and customers. This is why we built our state-of-the-art data viewer, WindBorne Live.

WindBorne Live enables users to view our global constellation, individual GSBs, search soundings by geographic region, and compare GSB readings to NOAA and the Global Forecast System (GFS)’s model data.

Our software platform is regularly used by hundreds of meteorologists and partners, including the North American Aerospace Defense Command (NORAD), the National Oceanic and Atmospheric Administration (NOAA), the Department of Defense, the National Center for Atmospheric Research (NCAR), the U.S. Air Force, and the Scripps Institution of Oceanography.

If you’re a WindBorne partner or government agency interested in exploring WindBorne Live, please get in touch to request access at windbornesystems.com/access

What are key safety and security features of WindBorne balloons?

In addition to making all of our active and past global sounding balloons (GSBs) viewable and trackable by our government and regulatory partners (see more in our FAQ on location data sharing), WindBorne balloons are also equipped with several key safety and security features.

By design, WindBorne maintains both autonomous and manual control over each individual balloon at all times. Our proprietary AI-powered flight system is designed to enable balloons to autonomously navigate toward targets with the option to dynamically retarget as needed. WindBorne Atlas, our global constellation, is monitored by WindBorne personnel 24-7, with the ability to make manual, expert intervention at any time from our Mission Control Center (MCC).

WindBorne has achieved unparalleled precision for balloons without active propulsion. The balloons’ unique, smart altitude control allows them to autonomously shift into different wind layers to catch the right currents in order to reach their assigned target. A WindBorne balloon, for example, collected data directly within the eyewall of Hurricane Ian. We can also smoothly avoid specific regions. For example, we choose not to fly over active conflict regions.

In the unusual event that a WindBorne balloon experiences an issue, such as the loss of satellite communication of a certain threshold, our platform has systems in place to automatically and safely conclude flights.

What makes WindBorne balloons so sustainable?

WindBorne balloons (officially named Global Sounding Balloons or GSBs) are purpose-built to be both extremely sustainable and cost-effective. We’re proud to power the only atmospheric sensing technology that can sustainably and safely observe the atmosphere anywhere around the world.

While a WindBorne balloon uses a similar amount of material as a conventional weather balloon, our balloons’ unique long-duration capabilities enable them to gather up to 150x more data per cost dollar than alternative collection methods such as conventional weather balloons and aircraft-carried dropsondes. (An aircraft-carried dropsonde is a sensing device with a small parachute, which piloted aircraft can carry and release over oceans or directly into extreme weather. This is a highly costly effort that poses risk to human operators.)

How is that possible? Conventional weather balloons, which are typically single-use, can only ascend vertically from a launch point on land, travel for a few hours to collect one vertical slice of atmospheric data, pop, and descend straight back down. By comparison, WindBorne balloons can fly for weeks at a time, even double-circumnavigating the globe, to gather dozens of vertical profiles in a single flight. This is the result of our team’s rigorous engineering efforts to reduce parts and waste, as well as our unparalleled, proprietary full-stack flight system, which spans hardware, communications technology, and proprietary, autonomous flight software.

While we’re proud of our sustainability break-throughs, we see significant room for improvement, which is a top priority. As WindBorne Atlas, our global constellation scales, WindBorne is committed to ultimately collecting at least 80% of our balloons after flight to enable as much reuse and recycling as possible. We’re uniquely positioned to do this thanks to the autonomous nature of our flight system, which can navigate balloons to chosen landing sites.

In the meantime, WindBorne continues to be plastic negative. In partnership withrePurpose Global, we retrieve and recycle 2x more plastic than we use. We also continue to innovate on our underlying balloon design and manufacturing processes,which are fully California-based and compliant, in order to continuously reduce our apparatus size and minimize material use and waste.

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