• Created by Unknown User (astrocrg@mit.edu), last modified by Unknown User (reilleya@mit.edu) on Mar 31, 2019 18:46

Overview

Ocean Water is the team's second composite propellant. It uses higher solids loading and fewer additives than our first formula to achieve improved performance.

Find the Grain Log here.

Formula

Appropriately certified individuals can find the formula here.

Performance and Combustion Properties

Typical ISP: 205-225s
a: 0.018 in/s
n: 0.383
Density: 0.057416 lb/in^3
gamma: 1.25
molar mass: 

Mechanical Properties

Main article here.

Mixings

Mixing Date
Serial Numbers
Site
Result
9-29-201798-PT #1, #217-110First two 98 mm grains mixed. Improper equivalent weight calculation lead to soft cure.
11-7-201798-PT #317-110Mixing to characterize EZ-Cast. Used old mixer.
11-12-201798-PT #417-110Used old mixer. Improvements to casting process. Slightly lower solids loading
11-14-201798-PT #5-717-110First mixing with new mixer. 3 characterization grain for characterization testing.
11-22-201798-PT #8-1017-1103 grains for characterization testing. Stopped using EZ-Cast (Failed Project).
11-28-201798-PT #11, #1217-110Used finalized casting procedures
12-6-2017OW-152 #1, #217-110First 6 inch grains. Densities were consistent with the 98mm grains used for characterization.
12-8-2017OW-152 #3-517-110Next 3 6 inch grains. 2 dogbones were also cast. Results pending.
12-20-2017OW-152 #6-8, OW-98-FIN117-110The "MegaMix"
1-30-2018OW-152 #9-1217-110Grains 1-4 for the Full Scale test motor. Each grain had a 1.7" core.
2-2-2018OW-152 #13-1617-110Grains 5-8 for the Full Scale test motor. Core diameters were 1.7" (2), 1.9" (1), and 2.25" (1)
3-??-2018OW-152 #17-2017-110Grains 1-4 for 8G motor test.
4-1-2018OW-152 #21-2417-110Grains 5-8 for 8G motor test.
5-17-2018OW-152 #25-2817-110Final mix of the school year, made four grains for a flight motor.

Motors

Identifier
Date
Site
Result
Characterization Static Fire #1November 25, 2017Crow IslandNozzle Failure
Characterization Static Fire #2November 25, 2017Crow IslandNozzle Failure
Characterization Static Fire #3November 25, 2017Crow IslandMotor success, pressure transducer failure
Characterization Static Fire #4November 25, 2017Crow IslandSuccess
Characterization Static Fire #5December 2, 2017Crow IslandSuccess
Characterization Static Fire #6December 2, 2017Crow IslandSuccess
OW-152-4G #1Janurary 14, 2018Crow IslandSuccess
OW-152-4G #2Janurary 27, 2018Crow IslandSuccess
OW-98-FIN1 #1Janurary 27, 2018Crow IslandSuccess
OW-152-8G #1Feburary 24, 2018Crow IslandNozzle cracked, but motor still delivered expected impulse. Thrust curve was not the correct shape.
OW-152-8G #2April 7, 2018Crow Island

Failure. Liner Burnthrough at T+3.

OW-152-4G #3July 21, 2018FARSuccess. First Flight Motor.

Discussion

Expand this: Much better, but not as good as we had hoped. Solids loading is lower than originally designed due to difficulty with vacuum casting. Now that we aren't vacuum casting, solids loading should go back up to regain performance. Though more testing is needed to prove it, a theory behind the increased burn rate seen in OW-152-8G #1 is that the high pressure cracked the 400u AP leading to increased surface area. This failure mode, in addition to the relative high cost and limited availability of 400u AP, suggests that we should ditch it altogether. To slow down the burn rate of the resulting bimodal propellant, we should replace the burn rate catalyst with a burn rate supressor such as oxamide. Without the burn rate catalyst we may need to add an opacifier, but it is also possible that the Al fills this role (link literature). The only other issue is that bimodal propellants may be more difficult to cast, but this isn't much of an issue because there would still be three different particle sizes, two of AP and one of Al. 

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