Held on Sunday, November 12, 1995 at the HALO Rocket Motor Test Facility
The following text was taken, with permission, from an article by Tim Pickens and Ronnie Lajoie, which was published in the November-December 1995 issue of the Southeastern Space Supporter, newsletter of HAL5.
The ninth Project HALO rocket motor test day was held on Sunday, November 12. Armed with two full bottles of nitrous-oxide (N2O), we really were ready this time to test our three remaining new enlarged hybrid rocket motors.
November 12 turned out to be a very cold day. We came prepared with some large kerosene heaters. It was so cold that our N2O tank pressure was only 450 psi, not good for a test motor that requires 550 psi to be optimized. We would quickly rectify this problem with band heaters.
We even had problems with our 386-PC not wanting to boot up because of the extreme cold temperature. This was nipped in the bud by a heating pad that Chris Pickens (our great host) so graciously loaned us to place under the computer. Our PC must have had a head cold! Get it? Anyway, this too was overcome. We took a lunch break while the equipment warmed up.
Once the test stand and data acquisition equipment was set up and successfully checked out, we prepared a motor (all-asphalt, a 11/2-inch core diameter, and a 16-inch length), started the video cameras rolling, cleared the test area, remotely loaded the oxidizer tank, performed one final range-safety check, then sounded the final 5-second warning alarm.
The count down went 5-4-3-2-1-IGNITION! First, we heard the pop of our igniter, then the genie hiss of the fuel slug, followed by the main N2O dump valve opening, and the roar of the motor coming to life. It was very intense and exciting watching our hybrid rocket motor burn with a thrust of over 300 pounds for a full six seconds!
The second test started off with a bad ignition. To ensure a good ignition on the next attempt, we doubled the amount of solid fuel. BOY, DID WE GET A GOOD IGNITION! The cloud of black smoke which resulted obscured the test, but we could tell from the loud noise that the motor was thrusting at full force.
After about 3 seconds, flame began to pour out from the side of the motor casing, near the top (much to our surprise). It turns out that the extra solid fuel served to superheat and weaken the aluminum motor casing. We wont make that mistake again! At a minimum, we will insulate the casing with an additional thermal barrier to protect it from the heat.
Using the backup steel motor casing, the third motor test (all-asphalt, a 11/2-inch core diameter, and a 17-inch length) went flawlessly. The thrust was so powerful that it punched a hole right through our half-inch-thick steel flame deflector plate and left melted steel in a small crater in the concrete pad! Wow!
The acquisition data from all tests revealed that we had a peak thrust of about 350 pounds and an average thrust of 302 pounds. This is about what was predicted by Steve Mustaikis. The average chamber pressure was about. 514 psi. Our C* (characteristic exhaust velocity) was about 4,561 ft/sec. All other data was very satisfactory and pleasing.
The data also showed that we were somewhat fuel rich, which manifested itself in the form of black smoke and motor performance inefficiencies. This problem will be corrected for the next, and hopefully the final, test firing for this phase of project HALO.
One final test we were able to perform involved another trail usage of HAN with McDonnell Douglas hybrid fuel. Dr. Dean brought a better container. This second test went better than the first, including another small purplish flame; but still the fuel did not ignite. Speculation is that the HAN requires much higher pressure and/or a much finer injector nozzle.
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This file was last modified on Saturday, 15-Apr-2017 13:19:40 EDT