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Comment by neilv | Hacker News Reader

How does one operate a balloon like that in US airspace, both legally, and otherwise without being a threat to other aircraft?

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Balloons are exempt from the ADS-B requirements to broadcast location. Most balloons are above 60,000 ft, away from all airplanes. Larger ones need to get exclusion zone when they launch. Small ones are assumed to be safe from small size.

To launch balloons you buy balloon, build tiny payload, inflate it, and launch. Most balloons transmit location in other ways. They also explode when get too high, and then payload parachutes back to Earth, where it is collected.

Amateur radio high-altitude ballooning:

https://en.wikipedia.org/wiki/High-altitude_balloon#Amateur_...

https://arhab.org/

You contact the FAA…

Anytime you do weather balloons, rockets, anything that goes above 500ft AGL, you need to notify FAA ahead of time. Get permits. Approval. And on launch day, have them on the phone.

If it will show up on radar, you better believe they will scramble the fighters.

Oh sweet local rocketry club Jesus. It’s only 500ft?

I could be wrong, but 500ft is the minimum recommended altitude for helicopters. That might have something to do with it.

depending on where you are. Yes. That's the moment you enter controlled airspace. Obviously it depends on where you are. In NYC, it's 500ft. In NM, it's FL10 or 10,000 ft. Either way, you should get the FAA involved so they don't waste tax payer dollars on F-16s. If you're flying an amateur rocket above minimums, it must adhere to Part 101 or be waived by FAA.

Everything below 500 is Class G (the G is for ground!) except right near airports, where controlled airspace goes down to the ground.

Class G can go much higher than 500 feet in some places.

I know, but someone in Class A, or B, that gets a drone for christmas might want to do some research before flying (some will prevent you from flying at all!). As too with amateur rockets (not the little model hobby kind) but anything that would show up on radar. ATC doesn't like it when things magically appear.

Long, long ago when I did a bit of rocketry we simply worked on a basis of no launching if there was anything in the sky. We were behind mountains from any radars, almost nothing would have been visible and hobby rockets are almost devoid of metal anyway. I know the guys shooting the high power stuff need FAA clearances.

Back then, ATC were a little more relaxed. “Was that a bird? I dunno. It just popped up and then disappeared. Strange” could have been what was said. Now, any blip is a phone call upstairs. Radar is a lot more accurate and ATC have the nerves. A balloon, a rocket, someone’s potato gun, anything that hits airspace on radar is going to be investigated, at minimum. More than likely, for small hobby rockets, you’ll get away with it or maybe talk to a local law enforcement officer but fly anything large enough, you’ll get a visit from the G men.

As I said, we were behind mountains. Not to hide from the radars but to find a sufficiently large open space that we could be confident everything would fall in said open space and flat enough we could pursue rockets without worrying about being inhibited by the terrain. And with vegetation sparse enough that if something did catch fire it couldn't spread.

Please provide the citation for this requirement? What laws or regulations have this requirement?

7400.2P - https://www.faa.gov/air_traffic/publications/atpubs/pham_htm...

They list the air space requirements, the MSL's, the procedures, etc. 500ft AGL isn't set in stone but it's the moment when you would enter an airspace should you be in one. This is why people go out to the deserts where there's no airspace and the minimums are FL10.

That entire section is about amateur rockets; nothing there applies to balloons.

Jesus, fine, here’s the parts about unmanned balloons since you need explicit instructions.

https://www.faa.gov/air_traffic/publications/atpubs/atc_html...

In aviation, the onus is on you to lookup the right regulations for flight. Ignorance isn’t a valid defence.

You linked to the wrong section (again); that covers how ATC should handle unmanned balloons, not what the balloon operator should do. You probably meant [FAR part 101](https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F...), of which subpart D covers unmanned balloons. But it looks like for anything under 6 lbs, most of the requirements don't apply, except to file NOTAM and notify the nearest ATC when you launch/descend and a few other things.

It varies around the world. In the US, Class E begins at FL600. Most of Europe, it's FL660.

It would be best if all objects in the sky that could harm aircraft had transponders, including vintage aircraft without electrical systems and balloons.

ADS-B transponders are expensive and big, but they are made for the aircraft market. It should be possible to do cheap ADS-B transponder like the cheap and tiny APRS transmitters that the balloons currently use. Assuming that they don't have follow the regulation for aircraft-grade electronics.

I've worked in industrial GNSS products. Electronics shrink all the time. A ruggedized module needing only antenna(s), SIM (for remote access), and power probably should or does already exist. The main barrier is the lack of harmonization and consistency in the CFR mandating it.

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