What kind of security while using solid propellent? was asked at 2018-06-27 00:06 UTC, I flagged it at 01:28 and it was closed by moderators at 16:09. This ultimately lead to the drafting of a community specific 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.

We have both that meta post and a previous one:


While the specific risk discussed in those is rocket fuel or the handling of explosive/dangerous chemicals, and "constructing your own engine", the expressed goals in these posts and the close reason is to close questions that ask about doing things that are inherently dangerous and/or illegal, and therefore preventing (further) answers to these questions from being posted.

How to make a model rocket that doesn't spin? asks about a rocket with articulated fins connected to servo motors, which are presumably connected to some control system with at a minimum some inertial feedback. The question asks about roll control (avoiding spinning) as a side issue, so presumably the main purpose goes beyond just avoiding the spinning that the adding of articulated fins near may cause.

Can we explore the following two questions:

  1. Could building a model rocket with maneuverability and/or guidance under power have some reasonable potential to be inherently dangerous? (please consider how many launches this would take to get working by trial and error; servo systems with millisecond response control loops are not beginner projects, and once perfected, this thing starts looking like a small missile)
  2. Would some model rocket question that was deemed potentially inherently dangerous and five people would like to close it be properly closed under the current existing close reason?
  • $\begingroup$ You can delete the post until I don't get an up. $\endgroup$ – peterh Jan 8 at 14:13
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    $\begingroup$ @uhoh Thanks for raising the meta post. I was thinking about it myself but I'm new to the ways Meta things are done. The rest of my thoughts are in my answer below which I hope is the right approach. $\endgroup$ – Puffin Jan 8 at 18:14
  • $\begingroup$ Given the things you argue should be included on this stack, I am amazed at the things you don't think should be on it. $\endgroup$ – user20636 Jan 10 at 20:09
  • $\begingroup$ @JCRM I'm amazing! :-) $\endgroup$ – uhoh Jan 11 at 1:39
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    $\begingroup$ CMs, this is another one that may need legal to weigh in. Reference the discussion under this answer: space.meta.stackexchange.com/a/1709/58 $\endgroup$ – called2voyage Jan 22 at 17:02
  • $\begingroup$ Thanks for escalating, @called2voyage — will update y'all once someone picks this up. $\endgroup$ – JNat Jan 29 at 11:04

My concern in the OP was directed towards the specific issue of there being a question asked out of context and and then potentially answered out of context - which did indeed happen in the comments.


  • in the OP there was no clue as to the test environment (town backyard vs. licensed club area in a desert)
  • no context about the size of the rocket or propellants (it could have been a footpump water rocket)
  • a negative statement about the OP author's self-rating (I'd look at this two ways, it was at least potential right for inviting comments from people to get the OP to set out their experience more clearly)
  • no context for other safety features.

Anyway, to answer the questions in this Meta post:

  1. Yes, it could be inherently dangerous to the uninvolved public but its complex. Its not that different from forum websites where people give advice about fixing your car brakes, except that (in the UK at least) cars are tested for safety by a licenced tester every year. It comes down to context and I would simply vote to close something like this where there is no context given. I'd do that rather than waste time waiting for the OP to improve their question because, in that time, everyone and their dog is chipping in with out-of-context advice.

  2. I'm not sure whether you are referring to should-we-have-a-canonical-response-for-folks-intent-on-blowing-themselves-up or why-cant-i-ask-my-question-about-amateur-space-projects-and-development and, actually, the close votes dialogue refers to "A community-specific reason - This question doesn’t meet a Space Exploration Stack Exchange guideline." which I presume means on-topic. To cut it short, I think that page does just cover it but could be improved so as not to narrow things down to just rocket propellant mixing. If it helps, I would like to see a slightly broader guideline that relates to perceived danger in conjunction with context.

As an aside, I put in a close vote on the OP based on insufficient clarity in the question because I got distracted with the various references to Meta posts and couldn't find the main on-topic guidelines.

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    $\begingroup$ I could see wisdom in forming guideline for answering in a way that delineates what might be risky behavior to avoid, in cases where describing such wouldn't assist someone who wanted to endanger others. I'm not sure this should lead to question closure in the general case, but I think you're operating well within the existing system to cast a close vote if you find the current question unclear. To me, the demand in most cases should be on the answerers to be professional and complete in their consideration of the risks, not the asker. $\endgroup$ – called2voyage Jan 8 at 19:13
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    $\begingroup$ Prior art for safely broadcasting technical recipes is the 1980's TV show MacGyver, whose on call scientist John Koivula would "omit at least one key element" of dangerous recipes. $\endgroup$ – Camille Goudeseune Jan 10 at 1:03

This answer is not intended to compete with @Puffin's answer but rather to supplement it. Issues of whether we as a community think questions about rocket guidance are "safe" aside, this starts getting dangerously close to export control issues, both under ITAR and EAR.

It's important to note that ITAR and EAR do not necessarily prohibit building or possessing items covered by these regulations. They do, however, restrict export of those items. What is important to note here is that an export is more than just a transfer of hardware outside the country. Simply discussing certain items with non-US persons would constitute an export, as would discussing those items in a venue where non-US persons would be able to access the information (i.e., here).

The following is a not-exhaustive list of items requiring careful attention.

EAR-controlled items relevant to this question are as follows:

  • 7A001: Accelerometers
  • 7A002: Angular rate sensors
  • 7A003: Inertial measurement equipment
  • 7A101 through 7A103 are similar but less likely to be applicable
  • 7E004: "Technology" related to guidance and control of air vehicles -- multiple items covered in this one
  • 9A004: Spacecraft and launch vehicles (particularly under subheading h: sub-orbital craft)
  • 9E002: "Technology" related to 9A004

For ITAR, the relevant USML items are as follows:

  • IV(a)(5): Rockets, SLVs, and missiles not meeting the categories of paragraphs (a)(1) through (a)(4)
    • Particular attention needs to be paid to Note 3 to Paragraph (a) of category IV of the USML (emphasis added):

      This paragraph does not control model and high power rockets (as defined in National Fire Protection Association Code 1122) and kits thereof made of paper, wood, fiberglass, or plastic containing no substantial metal parts and designed to be flown with hobby rocket motors that are certified for consumer use. Such rockets must not contain active controls (e.g., RF, GPS).

  • IV(h)(1): Flight control and guidance systems (including guidance sets) specially designed for articles enumerated in paragraph (a) of this category

While you might be interested in quibbling over the details of whether any of these items actually apply, I would find it wise as a site to stay back to a degree where we aren't acting as armchair lawyers, especially when violations would require hiring real ones. This is especially important for those of us who work in the space industry, where penalties for violating ITAR and EAR include debarment in addition to various other traditional government punishments.

  • $\begingroup$ Being very familiar with ITAR myself, I understand your concern, but we can't reasonably expect users to determine whether questions run afoul of ITAR. I think the burden on export-sensitive information is on the information holders to ensure they do not provide any such information in answers. I think that's the only way we can really avoid being armchair lawyers. But if you have further concerns about it, I can flag this meta discussion for the CMs to pass on to SE legal for review. I've already done that once for the sci-hub discussion (the CMs passed it to legal, but no response yet). $\endgroup$ – called2voyage Jan 22 at 15:58
  • $\begingroup$ @called2voyage I think my bigger point is that export laws provide a justification for closure beyond "we think it's dangerous" -- namely, we do not want to put SE at risk, test its indemnification clause, or put our users in a position of having export controlled material elicited from them and inadvertently committing a violation. My preference would be to have a closure policy that steers well clear of the line of what is or is not under ITAR/EAR. $\endgroup$ – Tristan Jan 22 at 16:32
  • $\begingroup$ Given that your concern is about putting SE at legal risk, I'm going to flag this for the CMs to pass to legal. $\endgroup$ – called2voyage Jan 22 at 17:00
  • $\begingroup$ Seems like a logical conclusion of this would be to close the site. $\endgroup$ – user20636 Jan 22 at 18:36
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    $\begingroup$ There's plenty of stuff that is space exploration related that doesn't come close. Note I've only brought up export control concerns related to two topics: amateur propulsion development, and amateur attempts at active guidance and control of rockets. To wit: could you use this knowledge to also build a missile to hurt somebody or something with? $\endgroup$ – Tristan Jan 22 at 19:30

The idea is bad, it is so bad that even talking about it is dangerous. It can lead to an accumulation of evil people wanting to make the site always more and more restricted.

Many other SE sites are ruled by such bad actors, the Space SE was so or so exempt from them (well, the another bad idea about the banning of rocket fuels was already a very bad signature).

I won't ever accept such a rule and I will vote always against it, ignoring the consequences. Consider it some type of a "civil disobedience".

I am also thinking that you are likely collecting voters for an once coming election after the site graduation. You lost my vote now.

  • $\begingroup$ So "even talking about it is dangerous", but helping random readers on the internet make guided missiles isn't? $\endgroup$ – uhoh Jan 8 at 16:26
  • $\begingroup$ @uhoh I think you've experienced something, how things went on the PSE some years ago, and how things are going on the MSE now. Please do not make the site ruled by an inner circle actively working on to make the site the possible most unpleasant for everybody, except themselves. I've also seen that you were targeted by some series of close-down-del votes in the past, here. This is what you want? A hird of monkeys, randomly picking up a topic and initiating to make it off-topic, because the collectively committed hostility serves as teambuilding for them? $\endgroup$ – peterh Jan 8 at 16:36
  • $\begingroup$ @uhoh Or there is the ServerFault. It is a site for professional sysadms. They made off-topic the so-named "control panels", i.e. packaged server solutions with a web-based configuration gui. Why??? Or there is the Android SE. There is (in theory) off-topic if you want to install a better android version. Or the Unix SE, where even unix-oriented programming questions are off-topic. But these sites are yet salvageable, there are many ways to circumvent the rules, mostly because a large part of the reviewers simply don't keep the so-named "meta community consent". $\endgroup$ – peterh Jan 8 at 16:42
  • $\begingroup$ @uhoh And making a really working, and really dangerous giuded missile is a very big, and very costly work. Check the drone prices, while they were completely reusable and manufactured massively! Imagine how would it cost if you would need to create a (single-usage) guided missile! If you have the resources for that, it is sure, not that will be your blocking problem, that you don't understand that the servo motors - fin configuration in the spin control. If you want to build a simple home rocket which can photo your city from a km height, it would cost tens of thousands $ and months of work! $\endgroup$ – peterh Jan 8 at 16:52
  • $\begingroup$ @uhoh It is like the nuclear technology would be off-topic on the PSE / Engineering SE only because some wonderful people thinks it can help others to build a nuclear bomb. No, such a site where this is off-topic, is not "secure" or "safe", it is horribly hostile and incompetent. $\endgroup$ – peterh Jan 8 at 16:53
  • $\begingroup$ @uhoh And there is also a deeper reason. This is about, how do we consider the people around us. Are they children, are they crazy, are they irresponsible? Yes, consider them so and they will be. But I don't want that. So, I will fight this until my last breath. $\endgroup$ – peterh Jan 8 at 16:55
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    $\begingroup$ @uhoh But honestly, I know very well, what will happen. You know, and I know. My this post will be likely moderated out, or deeply downvoted, and your idea will be soon "law". I've seen that already $\approx$ ten times on the site network, once even here (I fought also the previous braindead idea about banning the rocket fuels). I will fight it until my last breath, and some others with me, too. The bastards will be more. You are written down, this is what really happened, the collective social mechanics brings us into a yet more darker and more hostile SE, that is all. $\endgroup$ – peterh Jan 8 at 16:58
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    $\begingroup$ @peterh-ReinstateMonica I actually agree with your fourth-to-last comment. I personally don't understand the risk in this case, because I think it is unlikely the average person would be able to endanger themselves or others with this information. $\endgroup$ – called2voyage Jan 8 at 17:01
  • $\begingroup$ Also, while I don't agree with all of your points, I don't see anything that needs to be removed here (aside from the comment about braindamage, but I don't think that's really instrumental to your point). Downvotes, of course, are up to users. $\endgroup$ – called2voyage Jan 8 at 17:02
  • $\begingroup$ @called2voyage In the criminal law, there is some like "incompetent try" (sorry it is mirror translation). For example, if the offender curses the victim, and the victim dies, then the offender is not punishable for murder. | Really bad guys often become moderate after they get their long-fought diamond. But I have no idea, what are they, as mods, doing among each other. Possibly their vehemence needs a huge effort from the CMs/other mods to cool them down. But this is behind walls I can not see through. $\endgroup$ – peterh Jan 8 at 17:16
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    $\begingroup$ On the Security SE, there was a problem that most defensive tactics are well-usable also for attack. As far I know, the practice is now that if the post is not clearly about attacking, it remains open. I did not read the huge amount of pro-contra arguments but imho the de facto their reason was that the site did not want to kill itself. I want a well-going Space SE. I love it. Once, if I will have the time + money for that, I want to build guided rockets. Not as weapons. I just want to photo my city from a km height and I want to show it to my son. $\endgroup$ – peterh Jan 8 at 17:28
  • $\begingroup$ And, I know very well, how can I ask the correct questions which would circumvent even this "law". I won't ask what I really want to know, instead what is on-topic. If it is needed, then I fragment the question into multiple little one and ask them in parts. If some of them would be closed, I could fight for them on the meta and get a reopen. But others don't know these. I want a friendly site which can attract with x content yet another x, resulting an exponential growth. $\endgroup$ – peterh Jan 8 at 17:31
  • $\begingroup$ Thanks for your response. I understand and support your concerns about limiting questions and I posted the question in order provide a space for this discussion, not to try to make a rule. I think some of your points here are articulate and important and could be moved up into your answer post for better visibility. My personal bias is towards safety and fear of homemade dangerous objects. I posted the question looking for other views that might balance mine. I can absolutely guarantee you I have no political aspirations and will never, ever consider being anything more than a normal user. $\endgroup$ – uhoh Jan 8 at 23:17
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    $\begingroup$ I think some of the down votes may be due to the strong language; "talking about it is dangerous" and "an accumulation of evil people" and "other SE sites are ruled by such psychos". It's of course up to you, but if you would like users to vote on your answer to this question and not be distracted by those, you might move specific concerns about limiting "questions adding maneuverability and/or guidance under power" to the beginning and more global and long-term concerns about SE trends across multiple sites to a second paragraph. $\endgroup$ – uhoh Jan 8 at 23:23
  • $\begingroup$ @uhoh But I want homemade "dangerous objects". I love them. This is one of the best things one can do with his free time & money. And this whole site is about these "dangerous objects". If rockets are "dangerous objects" for you, you might start a "do nothing in harmony with the nature" site on the A51. Do not reduce site topicality because it leads to incredible amount of hostilities, and to deadly bad stats! You are going to expel exactly the best users among us! $\endgroup$ – peterh Jan 8 at 23:23

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