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Comment by dlcarrier | Hacker News Reader

A reminder to those who presume regulators make the right decisions, a cheap ADSB out transponder would have prevented this incident, but putting one on a weather balloon is prohibited by the FAA.

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An ADSB transponder, along with supporting electronics and battery will add to the weight of the aircraft. It makes it safer in one way, and less safe is another. This isn't quite the "slam dunk" you seem to believe.

Weather balloons already have restrictions on weight to minimize the consequences of collisions. The issue is that even if you can add a transmitter and meet the weight requirements, it's currently not possible to legally broadcast ADS-B data from a weather balloon.

They would need to increase the weight requirements if they're to add ADSB. Current ADSB transponders weigh as much as the entire weather balloon's package. Then add on the pounds of weight for batteries.

The uAvionix ping200X weighs 50 grams according to its datasheet.[1] With a 1.5W continuous power draw, a 60 gram lithium battery would power it for 8 hours, for a total of 110 grams. WindBorne balloons weigh 1.1kg at launch (including ballast), and the FAA limit for such balloons is 2kg.

1. https://uavionix.com/wp-content/uploads/dlm_uploads/2025/07/...

The balloons likely already have batteries and GPS receivers. An extra radio and antenna would add a few grams of weight and tens of mW of power consumption. That could be well under one percent more weight.

It's much, much lighter than a radar reflector, which aircraft weather radar displays aren't even designed to display.

Prohibited? Why?

Will air travel become safer because we don't know where they are?

What happens to the payload mass when you add the transponder?

It could easily be less than a percent of added weight, considering that there's probably already batteries and a GPS receiver on the balloon.

The FCC requires that airborne transmitters identify themselves by broadcasting the an FAA designator such as the aircraft registration number.[1] The FAA has no identification or registration process for small weather balloons. So this effectively prohibits them from broadcasting. It's possible to add a radar reflector, but they add significant weight and bulk to the balloon's payload. I think reflectors are only required for larger weather balloons.

1. See § 87.107: https://www.govinfo.gov/content/pkg/CFR-2024-title47-vol5/pd...

I'm confused about where the prohibition is. N991SS is an example of an FAA aircraft registration number for a balloon; I looked it up myself on the FAA N-number inquiry site to confirm. Your link does not talk about balloons at all. Where does the FAA prohibit weather balloons here? It sounds like it's just physically not possible to carry a transponder or reflector on a small weather balloon? But that's different than what the earlier posts were suggesting. It seems like it's physics preventing ADS-B on small balloons, not the FAA. If you did manage to get ADS-B on your balloon somehow, could you not register the balloon like the owners of N991SS did?

That balloon has a payload of up to 55lbs, so it follows different rules. WindBorne balloons are 1.1kg including the initial ballast.

There are ADS-B transmitters that weigh 50 grams and would require 60 grams of batteries to power them for 8 hours, so payload limitations are not an issue for WindBorne.[1]

The CEO of WindBorne replied to a comment about the inability to use ADS-B on weather balloons saying, "Yea, the FAA does a lot and I think overall they do a great job, but I wish there was better systems for communications here."[2] So I'm reasonably confident that my understanding is correct.

1. https://news.ycombinator.com/item?id=45660400

2. https://news.ycombinator.com/item?id=45660577

Sorry to drive by, but weather balloons like Windborne produces are deployed for a lot longer than eight hours. Many are up for more than two weeks, some even exceeding a month.

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