v1.0 - Safety Procedures and Requirements

Added by Jeremy Wright almost 11 years ago

A link to the NAR Model Rocket Safety Code can be found here

I also found this resource, which might be worth looking at for the Openeering Wiki. Skip down to the "SAFETY" section to see what's relevant to this discussion.

Here's a rough draft from the resources that I've listed above. I just made a quick revision of the items to adapt them to test stand usage.

  1. A chemical fire extinguisher (or, at least, a plentiful supply of water) should always be on hand.
  2. The operator should always wear the appropriate safety apparel like safety glasses when firing the motor. REMEMBER, the primary danger is from shrapnel in the event of an explosion.
  3. The test stand should be shielded on the sides to reduce shrapnel projection in the event of an explosion.
  4. No smoking is ever permitted anywhere near a test area when motors are also present.
  5. Use only lightweight, non-metal materials for parts of the stand that come in contact with the motor.
  6. Use only certified, commercially-made model rocket motors, and do not tamper with these motors or use them for any purposes except those recommended by the manufacturer.
  7. Fire a motor with an electrical launch system and electrical motor igniters. The launch system should have a safety interlock in series with the launch switch, and will use a launch switch that returns to the "off" position when released.
  8. If a rocket motor does not fire when the button of the electrical launch system is pressed, remove the launcher's safety interlock or disconnect its battery, and then wait 60 seconds after the last launch attempt before allowing anyone to approach the test stand.
  9. Use a countdown before launch, and ensure that everyone is paying attention and is a safe distance of at least 15 feet away when firing D motors or smaller, and 30 feet when firing larger motors.
  • A check-off list is helpful when conducting a rocket engine firing and should be made up of both technical events and safety items to be completed prior to the firing.

Replies (12)

RE: v1.0 - Safety Procedures and Requirements - Added by Ben Barnett almost 11 years ago

I have questions about 5 above (materials in contact with the D-U-T). I understand the need to minimize shrapnel, but why non-metal materials? For example acrylics like "Plexiglas" shatter easily under tensile stress and tend to produce sharp-pointed shards. Polyethylene is highly shatter resistant, but also flammable. Explosion is possible, but unlikely, while fire is part of the objective of the project.

What is wrong with materials like 3003 aluminum? It will stretch at least 100% before rupture under tensile stress, then tends to peel back without shedding significant mass. Aluminum has a specific gravity of about 2.0, which is <2X most plastics. I have very limited experience with safe dissipation of explosive energy, but it seems to me that materials like the "softer" alloys of aluminum or even copper would be highly useful in directing a blast wave without danger of shedding projectiles.

While I consider polycarbonate hazardous where it may be exposed to direct flame, it seems an ideal material for stopping small projectiles while maintaining good visibility of the D-U-T. I consider polymers that produce highly toxic combustion products hazardous where a significant potential for fire exists. If someone must use a fire extinguisher, they should be able to approach the fire without fear of long-term toxic hazards.

-Ben

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright almost 11 years ago

Thanks for the input Ben. I assembled this list to give us a starting point for discussion, and I'm glad you've joined in. Keep the comments and constructive criticism coming, and please post any additional safety items that you can think of.

Item 5 was designed to conform to NAR safety code item 1 which states that you should "use only lightweight, non-metal parts for the nose, body, and fins of [your] rocket." Notice that the NAR guidelines were designed for rockets, so we're having to adapt them for use with a test stand. You make very good points about the problems with alternative materials, including the possibility of toxic combustion products. Your point is also well taken about using something like a softer aluminum or copper that will deform before breaking. Part of the reason that I added item 3 to the above list was to reduce the risk of shrapnel being thrown laterally towards the operator and observers. Maybe that, coupled with the issues that you've mentioned, is enough to negate NAR safety item 1 in this context.

In putting the list together I attempted to make this test stand's safety guidelines something that NAR could endorse, and the above list is my first stab at that. We need to talk much more about this, and hopefully J and Greg will have time to let us know what they think too. I'm also interested in seeing if NAR would be willing to join in this conversation, but I need to check first to see if it would be best if a Mach 30 board member contacted them. I'll ask J about that.

RE: v1.0 - Safety Procedures and Requirements - Added by Ben Barnett almost 11 years ago

Item 6 "Launcher" of the NAR list, and related item 3 of our list lead to a bunch of design questions.
1. Who is the design engineer on our team? Am I the only one thinking about design details?
2. For NAR the rocket IS a projectile, while everything else is relatively stationary. What happens to the igniter, where does it go and at what velocity? (The ground is an ultimate projectile blocker.)
3. We propose to direct exhaust horizontally to eliminate the engine mass component from the force equations. How do we propose to handle exhaust gasses and associated particulates? How about a blue-iron stove-pipe with an elbow directed upward, and extending well above head-height? [OK, make it pretty and use stainless-steel :-) ]
4. Does the Test Stand include a physical perimeter shield? At what distance from the D-U-T? How close may observers approach the shield?
a. If the shield material can stop a .22-short slug, is nose-print distance safe? (I believe that 3/8" polycarbonate sheet will stop a .22-short, but that needs verification.)
b. I prefer transparent shield material for visual observation, what do others think?
5. May the Test Stand be used indoors with adequate ventilation (e.g. Nutter Center)?
a. What is "adequate ventilation"?
6. Oh yeah, then there is the parachute ejection charge. How do we deal with that?

This is probably just a start. At what point in the project is it appropriate to consider design details?

-Ben

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright almost 11 years ago

1. Who is the design engineer on our team? Am I the only one thinking about design details?

We're trying to follow the Systems Engineering Process (SEP) as closely as we can, so we're trying to avoid discussing design details at this point. I've been working with J and Greg on step 1 of the SEP (requirements) through the forum, and we're getting close to having them wrapped up. After that we should get into the design process starting with laying out a block diagram. Then we can start to address some of the design details. It may be that the safety procedures will have to be developed as the test stand is being designed, or we may just have to finalize/revise them after we have the design set.

What happens to the igniter, where does it go and at what velocity? (The ground is an ultimate projectile blocker.)

That's a good question, and one that needs to be addressed. I don't really have any experience with model rockets (something I'm going to have to remedy soon), so I don't have a feel for how exactly the igniter will react. We'll need to address this though which will probably require some experimentation.

3. We propose to direct exhaust horizontally to eliminate the engine mass component from the force equations. How do we propose to handle exhaust gasses and associated particulates? How about a blue-iron stove-pipe with an elbow directed upward, and extending well above head-height? [OK, make it pretty and use stainless-steel :-) ]

Those are good thoughts and I would love to be able to jump into a discussion on this, but I'm trying to be good and follow the SEP :) We'll need to make sure we include this in the design discussion when we get there though. I've responded to the handling of exhaust gases (and indoor operation) below.

4. Does the Test Stand include a physical perimeter shield? At what distance from the D-U-T? How close may observers approach the shield?

Item 3 on our list was intended (by me) to relate to physical shielding on the sides of the stand that in my mind were transparent (like Lexan), but I'm not sure about an entire perimeter shield. If we're sticking with the $200 budget on this, a perimeter shield may or may not be in the cards. Again, something that we'll have to work through. With the rocket motors that we'll be working with I would think that a perimeter of 5 feet would be sufficient if we have side shielding. That's just my own estimate though and isn't based on any tests that I've done.

b. I prefer transparent shield material for visual observation, what do others think?

I agree. This is to be an experimental, outreach, and educational tool, and so I think that clear shielding is important.

May the Test Stand be used indoors with adequate ventilation (e.g. Nutter Center)?
a. What is "adequate ventilation"?

Very good questions that aren't addressed in the questions above. We'll need to talk to J and/or Greg to see if they envision this being used indoors at all for demonstration purposes. As you would expect, model rocket guidelines don't cover this since rockets are launched outdoors.

6. Oh yeah, then there is the parachute ejection charge. How do we deal with that?

Very good point. Again, my lack of experience with model rocketry was a hindrance, so I hadn't considered that. I'm guessing that it's not easy to remove the ejection section of the motor without destroying it or changing its operational behavior. A couple of ways to deal with this in the design come to mind, but I'll hold off until we're further along in the SEP.

This is probably just a start.

You've brought up some really good questions that I think will be great to help move this discussion along. I don't think there are any easy or quick answers for some of your questions, so it will just take some research and discussion.

At what point in the project is it appropriate to consider design details?

I think that after we get the requirements and block diagram set it will be appropriate to start in on more of the design details. I don't know about anyone else, but I had kind of envisioned starting forum threads for each section of the block diagram so that we can have more focused discussions. It's still to be decided if that's the best way to go or not.

RE: v1.0 - Safety Procedures and Requirements - Added by J. Simmons almost 11 years ago

Just want to echo these are good questions and good early answers. Clearly we will need to adapt some of the NAR safety material to fit our project. My objectives with looking to the NAR safety material are to learn from others who work with these materials way more than we do and to produce a project NAR could be comfortable endorsing. Jeremy has pointed out we should open a dialog with NAR early in the process to smooth the way for these objectives, and I agree with him.

A couple of more specific comments:

  • Ditto re: a clear safety shield where required (both for operator visibility and for audience visibility at public events)
  • Great point about looking at how/if we need to redirect the flame (I am starting to think the physical mounting system should be something we address and test early in the design process to cover issues like this)
  • re: indoor operations, great question. I am also not sure what additional safety considerations would be required to operate an estes motor indoors, but we should find out.
  • re: ejection charge, I think we need to find a way of dealing with it that does not require modifying the motors. I am sure that will be an interesting challenge to overcome.

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright almost 11 years ago

I was poking around on NAR's site and found this:

http://www.nar.org/safety.html

That document actually has a section called "The NAR Conducts Rocket Motor Testing". Within that section is a link which shows a small scale test stand.

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright over 10 years ago

I already posted the first link in the Resources topic, but I thought I would repost it here. NFPA 1125 is apparently what the NAR (National Association of Rocketry) uses for their static motor testing safety standards.

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1125

There is also 1122 for moving model rockets:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1122

...and 1127 for high power rocketry:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1127

RE: v1.0 - Safety Procedures and Requirements - Added by J. Simmons over 10 years ago

Jeremy Wright wrote:

I was poking around on NAR's site and found this:

http://www.nar.org/safety.html

That document actually has a section called "The NAR Conducts Rocket Motor Testing". Within that section is a link which shows a small scale test stand.

Super awesome. Test stand image is included inline above. I see it is horizontal, and pretty small (I find its height to be surprisingly small).

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright over 10 years ago

When I talked to the NAR representatives they mentioned that they prefer the horizontal orientation to take the weight of the motor and its mounting off the load cell. That would be one less thing to mess with when doing data reduction. I have seen designs that allow you to tilt the stand up into a vertical orientation too. I don't know if there's any value in that, but it's kind of interesting.

RE: v1.0 - Safety Procedures and Requirements - Added by J. Simmons over 10 years ago

Not to get ahead of ourselves in the process, but I will admit a strong preference for horizontal designs for the same reason. I still can't get over how small the thing appears to be. It is very encouraging for Shepard.

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright over 10 years ago

I'm starting to revisit this issue so that we can finalize our requirements definition and move on with the design process. I'm personally concerned about copyright issues with using NFPA 1125 and wanted to take a pass at adapting the test stand safety requirements from other sources (NASA, other space flight groups, etc). In the process I came across the material safety data sheet for the Estes motors.

http://www2.estesrockets.com/pdf/MSDS-Estes%20Engines.pdf

Please post links to any test stand safety requirements and procedures you find here. There's already one resource link listed in the first post of this thread that has some test stand safety info that may be adaptable for our uses. Look at the "SAFETY" section on page 51.

RE: v1.0 - Safety Procedures and Requirements - Added by Jeremy Wright over 10 years ago

Page 2 of this doc for the Pasco Scientific motor test bracket (ME-6617) has some decent safety info.

ftp://www.pasco.com/Support/Documents/English/ME/ME-6617/012-06418A.pdf

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