3 Trying again using KNSO with our new casting bases. We also have a real
4 eye-dropper now for measuring the surfactant. 4 38mm grains of
5 1.875" length, using formula of
14 The multi-cooker was preheated to about 250F with the lid on. Temp was
15 increased during melting to 275F indicated.
17 Individual casting tubes with fill marks, coring rod inserted after pour,
18 cap installed and grain tapped down.
30 Propellant : propellants/knsb.xml
31 Nozzle diameter : 0.739 cm (0.291") (19/64")
34 Port-to-throat ratio : 2.952
35 Mass Flux : 1.374 lbs/inch^2
37 Propellant length : 18.440 cm (7.260")
38 Web Thickness (max) : 1.026 cm (0.404")
39 Burn rate : 0.773 cm/s (0.304"/s) (a=7.852mm/s; n=-0.013)
41 Total propellant weight: 216.00 g (7.619 oz/0.476 lbs)
42 Average grain weight : 54.00 g (1.905 oz)
43 Theoretical density : 1.841 g/cm3 (0.067 lb/in3)
44 Actual density : 1.582 g/cm3 (0.057 lb/in3)
45 Density ratio : 85.953%
46 Specific impulse (Isp) : 106.342 s (estimated)
47 Initial Thrust : 169.37 N (38.08 lbs)
48 Peak Thrust : 182.21 N (40.96 lbs) at 34.00% (0.45 s)
50 Kn Ini : 309.48 (488.04 psi)
51 Kn Max : 330.39 (520.59 psi)
52 Kn Fin : 248.87 (393.56 psi)
53 Kn Avg : 309.70 (488.40 psi)
55 Total Impulse : 225.104 Ns (40.69% H)
56 Burn Duration : 1.328 s
57 Average Thrust : 169.555 N
62 ![simulation data](test5-sim.png)
66 These four grains were assembled in an AT 38/480 case with a random AT
67 delay grain from the pile of left-overs, and flown in Robert's Madcow
68 Little John at Tripoli Colorado Spring Fling 2015. We used a Slim Gem
69 igniter from Quickburst. Great flight! The motor seemed to come up to
70 pressure quickly, and burned brilliantly.
72 The airframe weighed 1200 grams ready to launch, and 982 grams post-flight,
73 of which 1g or so was BP in the ejection charge, and a few grams were in
74 the Aerotech delay grain.
76 Post-flight measurement of the phenolic nozzle showed approximately an
77 0.330" throat, which clearly indicates some erosion from the 0.291" starting
80 ![flight acceleration data](test5-altosui.png)
84 Pour went really smoothly. One grain looked "perfect" with the propellant
85 settled evenly and a couple mm of open gap at the top of the casting
86 tube. We think this one may have been slightly under-filled compared to
87 the others, all of which had some evidence of propellant sticking to the
88 cap and leaving an uneven top surface. This resulted in some quick trim
89 work with a knife, ergo final grain masses not matching all that well.
91 We were totally stoked that the burn time matched simulation (once we factor
92 in a tenth of a second or two before the motor came up to pressure!). We
93 were also pleased that the max pressure was "right on time" at about 0.4
94 seconds after coming up to pressure. The regressive curve seems a bit
95 exagerated in the flight accel data, which seems completely explainable by
96 the nozzle throat erosion causing pressure to faill during that period.
98 Pretty cool for our first real flight test!