Crimson Powder Deployment Charge

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I was browsing The Chemistry Store web site last week, I had bookmarked the site because they sold pure propylene glycol, and of course I've been using food flavoring to thin my KNSU propellant believing the propylene glycol was the actual thinning agent. Anyway, I noticed they sold ascorbic acid (vitamin C). I had done a few tests of Peter E.'s crimson powder some time ago, using vitamin C tablets as the source of ascorbic acid. I wasn't overly thrilled with the results, so I wondered if using a pure form of ascorbic acid would work better. So I ordered some ascorbic acid and some propylene glycol for testing. This is the preliminary test of the crimson powder.

I mixed the ingredients as per the instructions on Nakka's web site.

6.2 grams KNO3

4.5 grams ascorbic acid

.5 grams red iron oxide

I lightly mixed the dry chemicals in a paper cup. Then added the dry chemicals to 30 ml of boiling water in a small stainless steel pot. The mixture was stirred over low heat and held at a light boil until most of the water was boiled off. What was left was a dark red paste. The paste was then smeared in a thin layer on a sheet of heavy aluminum foil, and placed in a pre heated oven at its lowest setting (about 175 degrees F.).

After a good hour in the oven I removed the foil. Once cooled I broke the dried chunks from the foil. I wanted a fairly consistent particle size, so I used a stainless steel strainer/sifter, breaking the chunks and working them through the strainer.

On the left is commercial 2F black powder, on the right is the crimson powder.

As you can see in the picture above, the black powder and crimson powder are similar in particle size, with the crimson powder having some smaller particles in it.

A quick check of the density showed crimson powder had only about 55% the density of the 2F black powder. Using my soda straw measure, the 2F black powder weighs .6 grams per inch, the crimson powder only weighs .33 grams per inch.

For a close to real experiment, I loaded up the upper body tube of the soon to be launched dual outboard rocket. The deployment charge holder was filled almost full with 2 grams of crimson powder. I inserted the largest parachute I had handy, thinking that would be about as much as I would ever try to push out the nose of a rocket that size. I used two .5" wide strips of aluminum foil tape to retain the nose cone. I set up the upper body tube by tying it to a fence post.

I set up both of my cheap digital cameras in the video record mode, and started the timer. At the preset 14 second mark, the charge went off. The nose cone blew off cleanly and fully extended the shock cord, but the parachute remained in the body tube. Upon inspection after the test, the parachute had a few small burns on it, and there was blackening of the area around the charge holder, much the same as would be found using black powder.

To set a benchmark, I performed the same test using 2F black powder. Of course, the 2 grams of black powder didn't come near to filling the charge holder, as the crimson powder had. Again, with cameras rolling I turned on the timer. At the set 14 seconds the charge went off, this time crisply blowing off the cone and deploying the parachute. I wouldn't say the parachute launched out the tube, but it did come out fully by about 4 or 5 feet, although it didn't reach the end of the shock cord. I think I'd use closer to 3 grams of black powder with this parachute, and a lot more crimson powder than that. Of course I'm not using a piston with this rocket, and a piston would reduce the amount of deployment charge considerably.

Nakka had reported crimson powder being more energetic than black powder. I'm not sure why I'm seeing the opposite. Perhaps my process is flawed somehow. Perhaps I need to make the particle size smaller, or perhaps all the moisture wasn't out of the powder. I'll do some more tests and post the results here.

Update: 8 September, 2006

I'm running a little low on commercial black powder for ejection charges and decided I should do a little more testing of crimson powder. So I made up a larger batch of 50 grams. Now, this is a slightly hazardous process, so I took all the need safety precautions such as full protective clothing, face shield, fire extinguisher...

I measured by weight 55% KNO3, 40% ascorbic acid and 5% red iron oxide. I mixed the chemicals in a small Pyrex bowel and added 100 ml of water. The mixture was then stirred until all the components were well mixed. The mixture was poured into a small pan and heated to boiling until the mixture was reduced to a medium thick paste. Then the mixture was spread onto a layer of aluminum foil. I folded the foil onto itself and applied pressure to compact the mixture as best I could.

The unfolded foil was then placed in a preheated oven at 200 F. to dry. Drying time was about three hours.

I thought perhaps I needed a finer particle size, so I broke off some dried clumps and ground them to a course flour texture. A couple of small samples were burned unconfined, they burned very rapidly without the huge cloud of smoke associated with black powder. So I decided to do a deployment test on my old rebuilt fiberglass rocket. This rocket is 3.5" inside diameter with a 20" long section, the rocket also uses a piston to push out the parachute. I used a 4.5" long section of 1/4" ID latex tube as a charge holder.

Click Here for a short video of the test.

I was very pleased with the results of this test. Only 2 grams did a fine job of deploying the recovery system. The reduction of residue and nasty smell of black powder is an added benefit. The lower density means you need a larger charge holder, but other than that this batch of crimson powder seems to work very well.