I guess my concern is from my using a metal detector on public land and the crazy things i have run into. Like a state park tell me i have to take
valuables to the office and they hold it 30 days. What makes a valuable? i know property like land or a building that says historic is something
you don't screw with. Anyway, I forgot the town has a field it uses for the hot air balloon festival to setup and take off..
Metal detecting and flying model rockets are very different (in terms of feeling the need to ask for permission) and there are several reasons for this.
One, some types of public lands specifically prohibit metal detecting, whether by statute, regulation or case law. Such prohibitions can exist for model rocketry, but I'm under the impression they're far less common.
Two, metal detecting will inherently involve the modification of the land, ie digging. Assuming you clean up after yourself after a launch, no such "alteration" of the land takes place with model rockets.
Three, there are no "archies" or academics that are opposed to the hobby of model rocketry (that I'm aware of). None of this, "but wait, you can't fly that rocket until some history or archeaology professor looks at the rocket first!" arguments to worry about with model rocketry.
Four, it's easier for a metal detectorist (don't ask me how I know) to trigger a "Karen." How many people launch rockets carring a conceal pistol and wearing camo? I've never seen or heard of this happening. But metal detecting? It's a common occurence, unfortunately. Also, seeing some stranger walking around by himself carrying a shovel can be a bit more alarming to some, compared to someone carrying colorful plastic, cardboard and/or fiberglass.
Five, the average "civilian" thinks metal detectorists might get rich with a find. Most metal detectorists know that this almost never happens and they hunt for the thrill of it, not to get rich. But I don't think the average "civilian" sees someone flying model rockets and thinks that person is about to get rich off of something they find on public land.
So I get your concern because of your metal detecting experience, but metal detecting is a hobby (unfortunately) that's more likely to draw side eye from someone compared to model rocketry...at least in my experience and from stories I've heard.