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"?

  • $\begingroup$ All right, I added a bullet and warning to the off-topic section of the help center and the tour. I also created the custom off-topic close reason below. $\endgroup$ – called2voyage Jun 27 '18 at 16:07
  • $\begingroup$ @called2voyage In parallel -- should we remove the [sugar-rocket] tag? $\endgroup$ – Tristan Jun 27 '18 at 18:22
  • $\begingroup$ The tag does seem to have one non-problematic question: space.stackexchange.com/q/21211/58 $\endgroup$ – called2voyage Jun 27 '18 at 18:23

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.

  • $\begingroup$ Note: The actual custom off-topic close reason may not be in sync with this community wiki, as edits require the effort of two moderators. Ping a moderator in chat for significant changes. Minor changes will be incorporated at that time. $\endgroup$ – called2voyage Jun 27 '18 at 17:14

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.

  • $\begingroup$ It'd be hard to argue the 'Space' part of Space Exploration for amateur rocketry too ;) $\endgroup$ – Jack Jun 27 '18 at 14:00
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    $\begingroup$ @Jack We do allow questions about rockets that don't go to space, but we are allowed to define the scope here however we want as a community--we are not limited to what does or doesn't fit the title. In this case, I think it would be to our benefit to make such questions off topic, even though they might be in line with other questions that are on topic. $\endgroup$ – called2voyage Jun 27 '18 at 14:02
  • $\begingroup$ I agree - it's kind of dangerous territory to be condoning homemade explosives. I was just having a sly joke about the likelihood of the rocket getting off the ground :) $\endgroup$ – Jack Jun 27 '18 at 14:05
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    $\begingroup$ @Jack Got it. :) I just thought I should be clear about how the topic scope works here for any onlookers. $\endgroup$ – called2voyage Jun 27 '18 at 14:07
  • $\begingroup$ I believe that Chemistry SE may have some policy about questions that may involve danger or even nefarious activity. I remember a question about the stoichiometry of air plus natural gas for example, it quickly received a comment with a reminder and link to something. $\endgroup$ – uhoh Jun 27 '18 at 15:42

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 , 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.

  • $\begingroup$ Constructing your own rocket (the entire vehicle) that uses a COTS motor is a widely-adopted hobby. Building your own rocket motors, on the remaining hand.... (pun intended) $\endgroup$ – Tristan Jul 10 '18 at 18:57
  • $\begingroup$ I like the looks of this, but since we only get three custom close reasons I'd like the reason to be broader than just amateur experiments of constructing homemade rocket engines/propellants. I want to cover any life-threatening amateur experiments. That said, with a change to broaden it in that way, I'd be comfortable with making this the new close reason after the suggested meta faq is created. $\endgroup$ – called2voyage Jul 10 '18 at 20:50
  • $\begingroup$ @called2voyage I've created a FAQ Meta question. Feel free to edit as needed. I kept it as broad as possible while still highlighting the dangers involved. $\endgroup$ – Machavity Jul 10 '18 at 23:45
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    $\begingroup$ @Machavity All right, you can see the change at the community wiki: space.meta.stackexchange.com/a/1028/58. It will be a while before the change is live. I submitted the new close reason, but it requires another moderator's approval. $\endgroup$ – called2voyage Jul 16 '18 at 15:50

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.

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    $\begingroup$ I share the way you feel about this but there are problems including providing people the opportunity to mis-inform others as well, see this comment for why SE isn't the right place to allow anybody on the internet to post bad advice along with the good. Down voting only because of this reason. $\endgroup$ – uhoh Dec 25 '18 at 12:45
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    $\begingroup$ I quite agree, @hobbes, I feel questions are being closed for this reason that don't match either "asking questions about performing experiments that are clearly dangerous beyond their recognition" (from the OP) or "dangerous amateur experiments" (from the close text) $\endgroup$ – JCRM Dec 27 '18 at 21:54

I think it's important and worthwhile to distinguish merely potentially hazardous amateur questions from people who actually are intent on blowing themselves up.

High power rocketry, experiments with small liquid fueled engines, and the like are all things that highly skilled people can do with a reasonable level of safety. Some of these might be more appropriate for Engineering than Space. People who are smart will do their own research and may ask specific questions that indicate knowledge of the field and the risks they are encountering. Other people, like the linked post, will ask incredibly basic "if you have to ask you don't know" questions or questions about the quickest and easiest way to catch a hypergolic tiger by the tail.

Not answering at all will have the biggest effect of driving people to less-reputable places where they will answer.

I think we should be as liberal as possible with this kind of thing.


I don't believe that making it offtopic is a good idea.

My arguments:

  1. Also the youtube is full with similar videos. A disclaimer is enough there. And we have a more narrow visitor group.
  2. 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.
  3. 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.
  4. 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.
  5. Citing Benjamin Franklin: He who sacrifices freedom for security deserves neither.
  6. 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.

  • $\begingroup$ We do allow questions on home-built rocketry, just not home-built engines/motors or homemade propellant. $\endgroup$ – called2voyage Jul 20 '18 at 18:28
  • $\begingroup$ @called2voyage I am not sure, (1) how could a home-built rocket work without a drive or propellant, (2) where could I buy rocket drives on the ebay, how does it improve safety, (3) how could we call a rocket "home-built" if neither its drive and propellant is home-built, (4) how could improve the safety of anybody by cutting them off from the information from anything, and (5) the notice is about "amateur experiment of extreme danger", which is a very broad formulation with the deadly potential to get the site to self-mutilate itself by overmoderation. $\endgroup$ – peterh - Reinstate Monica Jul 20 '18 at 18:42
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    $\begingroup$ 1) You can get model rocket motors that are single-use engines with the propellant included when you're making homemade rockets. You do not have to make your own engine or propellant. 2) You can buy them online (this varies with locality), and it improves safety because they are built to be reliable. 3) There is more to rockets than just the propulsion: shape, staging, fins, number of engines, etc. 4) Refusing to share information on homemade engines or propellant does not improve safety for those who do, but it does communicate that we disapprove. Professional development is safer. $\endgroup$ – called2voyage Jul 20 '18 at 18:47
  • $\begingroup$ @called2voyage If you want to become once a mod of the matured SpaceSE, I strongly suggest to avoid this topic-narrowing, overmoderating direction with all the influence you have. $\endgroup$ – peterh - Reinstate Monica Jul 20 '18 at 18:49
  • $\begingroup$ 5) The formulation is intentionally broad to allow us to be judicious and not get into rules lawyering. It is not intended to allow closure of any question one thinks is dangerous. If you disagree with the closure of any question under this reason, you can take it to meta--just like anything else that is closed. We have already closed questions for being dangerous before without this reason, the custom reason just makes things more clear which is good. $\endgroup$ – called2voyage Jul 20 '18 at 18:49
  • $\begingroup$ In response to your last statement, the decisions here are made by the community. The community has been firmly against these types of questions for some time, which is why I made the proposal that I did on this question. I am not overmodding because I am not stepping beyond what the community desires, just helping communicate it. $\endgroup$ – called2voyage Jul 20 '18 at 18:51
  • $\begingroup$ If you want to know how the community decides such things: votes. For example, the votes in this meta discussion. You can see what was upvoted and what was downvoted. For the record, I didn't downvote your post. $\endgroup$ – called2voyage Jul 20 '18 at 18:52
  • $\begingroup$ @peterh nobody is cutting anybody off from information. But SE is not a good platform for this because there is no control over how wacky, litigious users (or those they injure) may get or how bad advice in answers or comments can get. We can flag stuff but once it's been read it can't be unread. Try to ask how to make explosive mixtures in Chemistry and see how quickly you get shut down. Like several other kinds of question, this kind is not a good fit for Stack Exchange. $\endgroup$ – uhoh Dec 25 '18 at 12:26
  • $\begingroup$ Personally I don't think we should be "cut off" from parade questions 1, 2 but the voters have spoken :-( $\endgroup$ – uhoh Dec 25 '18 at 12:34
  • $\begingroup$ @uhoh On some mysterious reason, as sites are growing, always a psychotic "core team" appears, whose first task is to make the site terrible for the possible largest group of visitors. Yes, they have always their "reasons". I don't know, what could be done with it. I think, the SE should intervene and eliminate them, but they are mainly ignoring this problem, and their public communication even supports them. Well... somewhere I've heard, "fish is stinking from its head". That means, yes, structural problems of a system are the fault of its top-level controlling body. $\endgroup$ – peterh - Reinstate Monica Dec 25 '18 at 14:24

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