< Serge77 - My Rocket Workshop >

Part 1

Summary: the task is to develop effective method for ignition of BATES grain ends in multigrain motor. (See Part 1 for description of the problem and experiment setup)

Two types of samples were prepared. Type I - with uncoated core for insertion of different secondary ignition compositions (SIC), as was described in Part 1.

Type II - with flat core, coated with different ignition compositions. Preparation is shown on the pictures:

 Samples, coated with BP-NC-acetone slurry:

 Samples, coated with KNO3-C-ethanol slurry:

Finished type II samples: first row - uncoated core; second row - core coated with BP-NC-acetone slurry; third row - core coated with KNO3-C-ethanol slurry.

Prepared samples:

1-3 SIC-1: KNO3-C-sucrose-iron oxide 75-15-5-5. Red, yellow or brown iron oxide may be used with equal success.

4-6 SIC-3. KNO3-Al-S-iron oxide-wallpaper glue(modified starch) 57-30-10-1-2.

7-9 Jimmy Yawn's fuse paper. Two pieces of paper were inserted in the core (actually, each piece of paper is two-layered, it is usual paper towels). I use 65-35 KNO3-paper composition.

10-12 BP-NC slurry, as suggested by Flint Hapirat. Commercial black powder was milled to dust and mixed with solution of smokeless powder in acetone. The ratio of BP-NC (dry mass) is 100-5.

13-15 Richard Nakka's KNO3-C slurry. KNO3-C composition was prepared from milled pharmaceutical activated charcoal and KNO3 by evaporation of water solution/suspension. Dry composition was milled to dust and mixed with ethyl alcohol.

16 KNO3-C-ethanol slurry, same as above, but KNO3-C composition was milled down to the mixture of 0.1-0.3 mm granules and smaller particles. It is leftmost sample on the above photo of samples, coated with KNO3-C-ethanol slurry.

17-19 empty core.

Ambient temperature was +20C. Measured burn rate at this condition of this propellant batch was 2.6 mm/s.

Samples were fixed vertically and ignited with propane torch.

Sample with SIC-1 in the core:

Burn video: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 (300-1400 KB).

Total burn time and SIC burn time were measured from the video.

SIC burn rate was calculated as (core length) / (SIC burn time).

Core ignition time was calculated as (total burn time) - 3.1, where 3.1 is calculated burn time of 8 mm layer of KNSB.

Core ignition rate was calculated as (core length) / (core ignition time).

It is not possible to measure SIC burn time from the video in the case of KNO3-paper, because its burning is not distinguishable from the KNSB burning.

Very fast burning of BP-NC leads to the overpressure and detachment of paper Scotch tape from the shell' seam. I believe it did not affect very much on the burn time, as can be seen from comparison of sample 13 (overpressure) and 14-17 (no overpressure).

Compositions SIC-1, SIC-3, BP-NC and KNO3-C show almost equal performance. The most effective are SIC-3 and KNO3-C.

KNO3-paper is far less effective, at least in my hands.

Very fast burn rate of ignition composition (BP-NC) does not automatically leads to the fastest core ignition rate.