Department of Transportation Regulations and Rocketry

Explosives are classified according to their properties for purposes of shipping. The basic classification is a two digit number and describes the basic hazard.

United Nations Explosive Hazard Codes
1.1 Substances with a mass explosion hazard
1.2 Substances which present a projection hazard but no mass explosion hazard
1.3 Substances which present both a fire hazard and a minor blast or projection hazard (or both) but not a mass explosion hazard
1.4 No significant hazard
1.5 Very insensitive substances with a mass explosion hazard
1.6 Very insensitive articles with no mass explosion hazard

Before any explosive material can be shipped, it must be classified by the Department of Transportation (DOT) so that its hazards are known. This process can be quite expensive. This site provides a quick background on the process. For more details than you probably want, look through the UN classification procedures. I don't know which specific test causes APCP to be classified as an explosive, but I suspect it is simply that it is designed to produce an "explosive or pyrotechnic effect". Which include such mundane things as producing heat, smoke, or fire. Test 6(c) is the one which decides which division it is in. Since APCP burns really well, this test puts it into division 1.3.

Just because something is classified by the DOT with an explosive hazard class, does not mean that it goes "bang". For example, road and aerial flares are classified as 1.4 explosives. (See Material Safety Data Sheets for Orion flares.)

Because the materials used in hobby rocket motors are hazardous materials (except for a few hybrid motors), shipping is complicated. For the most part only trained and certified shippers can ship HAZMAT. This prevents the average rocketeer from shipping motors legally.

But you can transport your own motors to the launch site because the DOT exempts private non-commercial transport:

49 CFR 171.1(d) Functions not subject to the requirements of the HMR. The following are examples of activities to which the HMR do not apply:

(6) Transportation of a hazardous material by an individual for non- commercial purposes in a private motor vehicle, including a leased or rented motor vehicle.

Some smaller motors can be shipped via USPS but even this requires prior authorization.


There has been a lot of noise lately (September 2011) about this special permit. Apparently the Pipeline and Hazardous Material Safety Administration (PHMSA) which is part of the DOT and regulates transport of hazardous materials, sent a letter to the various parties to SP-7887. The actual letter has not been published anywhere that I could see which makes it difficult to know what is in it. But DOT apparently plans to eliminate this permit.

SP-7887 allows for the shipment of items classed as NA0323 or NA0276 (the NA means these classifications are not acceptable for international shipments) as if the were division 4.1 flammable solids rather than their actual 1.4 explosives division. The response from Estes complains not about increased costs (because they are equally expensive) but that some naive customers will see the word "explosives" and be frightened. So frightened that they will flee the hobby in terror. Or something. Which seems a little odd as most Estes motors can be shipped via USPS as Toy Propellant Devices. Which not only eliminates any scary terms (USPS Pub52 explicitly prohibits marking the package with DOT labels.) but avoids significant HAZMAT fees.

PHMSA has been making changes to their special permit process as a result of a DOT Office of Inspector General Audit which revealed several problems. One of which was that the process did not ensure that an equivalent level of safety was maintained. Revoking SP-7887 might be a response to that but without the DOT letter, I can't tell for sure.

Estes letter in response (posted to the vendors area at The Rocketry Forum) has a section titled "Problems with the UN standard" which while it discusses aspects of that standard, never identifies it. But I was able to find it in the UN Model Regulations. That is about excluding items from Class 1 completely. It has a tougher test than that required in test series 6(d) for compatibility group S which tests them as packaged for transportation.

The Manual of Tests and Criteria has all of the tests to determine the proper classification of explosives and other hazardous materials. Including test series 6(d) mentioned above.

While searching the PHMSA website for the show cause letter I instead found a Penalty Action Report which showed that Estes had been fined $1,250:

Offered class 1.4S hazardous materials as Division 4.1 materials, under the provisions of DOT SP-7887 and failed to satisfy the requirements outlined in the special permit. [173.22(a)(2)(v); DOT SP-7887] Case No: 09-0106-SE-CE

So it appears that Estes shipped something under this permit at least once and screwed it up. I could find no other details.


Someone finally posted a copy of the letter at Rocketry Planet. The key sentence in that short letter is: "PHMSA has determined that DOT-SP 7887 does not meet a level of safety that is at least equal to that required by the regulation from which relief is sought." So this does appear to be a result of the OIG report. Alas, while it talks about a new criteria for exclusion from Class 1, it doesn't provide a detailed citation. It might be the test added at in Rev. 17 of the UN Model Regulations. (This addition is a good thing. It is not immediately obvious looking at the Manual of Tests and Criteria how to decide if something should be excluded from Class1. Not that BP or APCP rocket motors will ever be anything other than Class 1.) But if so, I think that is more appropriate as that is about testing in a packaged condition.