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Serge77 - My Rocket Workshop >KNSB Igniteability Experiment
Part 2
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)
Preparation
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.
Experiment
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).
Results
# |
Secondary ignition composition type |
Core length, mm |
Total burn time, s |
Secondary ignition composition burn time, s |
Secondary ignition composition burn rate, mm/s |
Core ignition time, s |
Core ignition rate, mm/s |
1 |
SIC-1 |
67 |
4.12 |
0.32 |
209 |
1.02 |
66 |
2 |
SIC-1 |
67 |
4.92 |
0.56 |
120 |
1.82 |
37 |
3 |
SIC-1 |
67 |
4.24 |
0.48 |
140 |
1.14 |
59 |
4 |
SIC-3 |
67 |
3.68 |
0.36 |
186 |
0.58 |
116 |
5 |
SIC-3 |
67 |
3.80 |
0.28 |
239 |
0.70 |
96 |
6 |
SIC-3 |
67 |
3.68 |
0.28 |
239 |
0.58 |
116 |
7 |
KNO3-paper |
67 |
8.12 |
- |
- |
5.02 |
13 |
8 |
KNO3-paper |
67 |
7.72 |
- |
- |
4.62 |
15 |
9 |
KNO3-paper |
67 |
8.04 |
- |
- |
4.94 |
14 |
10 |
BP-NC |
67 |
4.32 |
0.12 |
558 |
1.22 |
55 |
11 |
BP-NC |
67 |
4.16 |
0.12 |
558 |
1.06 |
63 |
12 |
BP-NC |
67 |
4.08 |
0.12 |
558 |
0.98 |
68 |
13 |
KNO3-C |
67 |
3.76 |
0.28 |
239 |
0.66 |
102 |
14 |
KNO3-C |
67 |
3.40 |
0.20 |
335 |
0.30 |
223 |
15 |
KNO3-C |
67 |
3.68 |
0.20 |
335 |
0.58 |
116 |
16 |
KNO3-C |
67 |
3.48 |
0.24 |
279 |
0.38 |
176 |
17 |
empty core |
67 |
16.52 |
- |
- |
13.42 |
5.0 |
18 |
empty core |
67 |
20.00 |
- |
- |
16.90 |
4.0 |
19 |
empty core |
67 |
14.02 |
- |
- |
10.92 |
6.1 |
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).
Comments
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).
Conclusions
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.
03.06.2007 Serge77