Held on Saturday, February 24, 1996 at the HALO Rocket Motor Test Facility
The following text was taken, with permission, from an article by Tim Pickens, which was published in the March-April 1996 issue of the Southeastern Space Supporter, newsletter of HAL5.
The tenth Project HALO rocket motor test day was hald on Saturday, February 24, at our test facility in Gurley. We had hoped this would be a very successful and final test day for Project HALO, Phase 0. This was to be a test day to confirm the total impulse of our propulsion system, and to test the durability of our components. Many of our objectives were achieved, but some were not.
Many of us arrived at our usual 9-10 am time. We had hoped that this day would really go smooth -- and it did until we started working! I had grand visions of testing by lunch, enjoying the cook-out festivities, and relaxing on the farm while taking an evening stroll. This was going to be the best day of testing to date! Why, I had even gone and gotten a 70-lb bottle of N2O so we would definitely not run out as we had in times past. We all met at my garage two nights before to test out our data aqusition system, stage all the necessary test support equipment, prepare two motors for testing, and to finalize the details of our upcoming test day.
This would be the first time that we would be testing the total propulsion system, with no means to stop the burn. This was a very exciting endeavor considering that we had never burned a motor of this size for over 6 seconds. We would be able to record the thrust, chamber pressure, nitrous flow pressure, temperature, and burn time as we had done in the past. We would also test our igniter, valve, nozzle extension, double tank configuration, and the ability of the system to handle the loads of up to 350 pounds of thrust. The loads would be distributed through the entire structure because of the way we secured the motor to the test stand.
We spent hours getting the data aqusition to work properly. The cables and the connectors do not seem to like the moisture that the country conviently offers. Thanks to the fine group of problem solvers that we have, we were back in business before long. The stand, plumbing, and associated hardware were assembled, while others worked getting the calibration finalized. We were finally back on track.
We mounted the rocket into the stand and connected all the fill hoses, chamber pressure hose, igniter, etc. We were finally ready to start the N2O loading. This was expected to go well because the Nitrous Pump that I had frabricated was supposed to help us. The idea was to fill the tanks on the rocket without having to vent.
Previously, during filling, we would have problems getting the desired amount of N2O into the vehicle tank without venting. The pressure from the supply tank would near the pressure ont the target tank thus reducing flow to near zero. We would vent in order to reduce the target fill tank pressure, thus creating a pressure differential, which promoted N2O flow. The valves we were using in the past increased the vehicle weight, which is not desirable. The new pump would also increase the safety in our loading procedure.
We were finally to begin testing; nothing could stop us now. We began loading the N2O into our vehicle, Al and I stayed down at the pad behind the wall in order to try the new pump system out. Steve was talking to us via intercom to keep us posted on the rate of loading, which he was monitoring on the computer. After 5 minutes of loading, only 2 pounds of N2O was in our vehicle. We decided that something was not right; we should have easily been able to load at least ten pounds of N2O with no venting. We tried the pump to see if the bypass was restricting flow. It seemed to work at first; we saw another pound go in, but then it quit filling. We new that we had a new bottle, so being out of N2O was not an option. Or so we thought.
We tried everything from turning the bottle upside down just in case there was no pickup tube, to our old method of venting. We finally went straight to the horses mouth only to learn that it was dry and not wet. In other words, we only had gaseous N2O left in the bottle - which meant that we had been sold an empty bottle for the second time! We were delirious at this point and totally frustrated. It was Saturday, and no gas supply companies were open. I wonder why they call it laughing gas!?!
Anyways, we had enough in our other N2O tank to do a partial test. We loaded about 5 pounds, which was mostly gas. We decided that we were going to burn something, no matter what! We all took our places (hiding behind trees or whatever was at a safe distance away), and the countdown began. 3-2-1-FIRE! Smoke billowed from the nozzle for what seemed to be an eternity, and then the motor roared as it came to life. The motor flamed for 15 seconds! Only two of those 15 seconds was usable thrust because the N2O was in a liquid state, which our system requires. The rest of the burn was gaseous tail off.
We were very pleased with the results of the test although we did not obtain a total impulse. The chamber pressure was where we expected it to be. The thrust was low during the liquid and gaseous phase because of our 44-to-1 expansion ratio on our new nozzle extension, which was not optimized for a sea level atmosphere. We used it anyway because it would be a great reliability test to see how it survived under heat and shock. I am happy to report that it did great, and our new ablative coatings did an excellent job also at providing protection for our nozzle extension, premixing chamber, and post-mixing chamber. All of these areas were of great interest to the propulsion team. These will be key issues to address when we move on to HALO Phase 1 -- Rockoon Proof-of-Concept.
We were going to burn two motors, but instead only burned one because of NO NITROUS! One motor was to have the extension; one would not. We would then compare the data, and adjust to account for the over expansion on one motor, which was more of a hardware test than a total impulse test.
Nonetheless, we are pleased with the test and are looking forward to a Manchester ground launch on April 13. Much work is needed to be completed in all areas. I encourage all to get involved and be apart of our history making project. We are in our final stretch now, and it would be a good time to get in the race so we can all cross the finish line together. Ad Astra!
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This file was last modified on Saturday, 15-Apr-2017 13:19:40 EDT