Inspired by this question and others I've seen like it. Do we want to steer clear of advising people who are asking questions about performing experiments that are clearly dangerous beyond their recognition, other than a solid "Do not do this"?
Custom off-topic close reason:
Questions about dangerous amateur experiments, such as constructing your own engine or propellants are off-topic. Rockets and their propellants are INHERENTLY DANGEROUS and can pose hazards to not just yourself, but others around you (friends, family, neighbors, etc). It may also be illegal. Please see this meta post for more information.
I think this is an area that maybe we should decide if we even want on topic at all. Maybe something like:
Questions relating to amateur experiments of extremely dangerous matter, such as home-brew rocket propellant, are off topic
Then, we would have something in the Help Center to point people to and we could immediately close such questions. We could even include a notice in the Help Center saying something like:
DO NOT DO THIS! Extreme risk to your life or health.
I like it, but in keeping with the other closure reasons on other sites I'd like to propose this
Questions about constructing your own rocket or propellants are off-topic. Rockets and their propellants are INHERENTLY DANGEROUS and can pose hazards to not just yourself, but others around you (friends, family, neighbors, etc). It may also be illegal. Please see this meta post for more information.
I linked back to this question just so it would have one, but I would suggest rolling up a separate Meta for this, elaborating why building your own rocket is dangerous. Once it looks good, tag it faq, and lock it (lest people want to debate it).
The Help Center link really doesn't cut it. We need a page dedicated to just this subject.
I disagree with the decision to declare all discussion of home engine development to be off-topic. That decision means we're sending people off into the wilderness instead of informing them.
See this question for example. The decision to close as off-topic means we've lost a chance to inform this person. This person would have been better served with an answer that explains the risks of LOX/RP and a recommendation to take the more traditional part of the rocket hobbyist i.e. going from bottle rockets to solid motors intended for the purpose of flying model rockets.
I don't believe that making it offtopic is a good idea.
- Also the youtube is full with similar videos. A disclaimer is enough there. And we have a more narrow visitor group.
- Legality is heavily dependent on the actual country. It might be legal or not, it is not our business to say it. On this reason, the whole politics SE could be closed, because practically all of its posts are illegal in at least one country of the world.
- Typically, making the topic of the site narrower, we expand a gap between (1) What good-standing visitors think this site is about, and (2) what about it really is. The difference causes users leaving us with bad feeling, and these are typically expert users, at least enough expert users to ask about home improvised rocket experiments. And I think we want to improve, expand, both in quality and quantity, to once mature the site. It is our most elemental group interest.
- Home-built rocketry is an interesting topic, it is a way to learn about the practical space technology, which is by nature a HQ topic here, attracting visitors and improving the site, both in quality and in quantity.
- Citing Benjamin Franklin: He who sacrifices freedom for security deserves neither.
- How could we improve the safety of anybody by cutting them off from information? The best way for safety is if you have all the required information.
I think a disclaimer is far more than enough in this case, or at least a FAQ entry with a warning, but not a close reason.