The Swank Aerospace facility was awoken from a deep sleep. I beautiful spring day was Sunday May 20th as we arrived at 8:30 AM to cloudless sky full of sunshine. Four of us Ken, Don, Don and myself greeted the site with a good feeling that we where going to see something big today.
Ken and Don had worked through the winter to solve the ignition system with a total redesign. Ken added two pressure regulated tubes in the injector plate as well as a spark plug ignition system. The tubes where used to pipe in propane and nitrous at a very low rate. The spark plug gave the gases an ignition source that when lit, sounded like a throaty blow torch. Other refinements such as stepper motor controlled flow valves for the nitrous and the helium charged kerosene also improved the odds of the motor lighting on the first try.
After a couple of hours of prep time hooking up all the data collection and control devices it was time to start filling the tanks. We also brought up mission control which consisted of a gauge and data collection PC, an ignition control and valve control PC and a motor video monitoring system. Right before the first test we also sprayed the trees and surrounding area with water just in case. We also setup four video cameras in different places to capture the whole event.
After everything was ready and a couple of tense moments of some choice words, Ken finally decided to start the ignition sequence. The igniter system was started and lit right away. You could hear the blow torch action of the propane and nitrous bellowing in the combustion chamber and a couple of seconds later Ken started the valve opening sequence. The first bang and small fireball helped to raise our heart rates a bit but was somewhat expected. The motor lit and ran with a very rich kerosene mixture. Then there where several small popping sounds like a solid motor chuffing. Then another bigger fireball and bang as the nitrous valve allowed more of the gas to flow into the chamber. I believe the motor was running. All I can say is that it was loud. Then after about 3 seconds was another bang with an even bigger fireball. At that point Ken shut down the system and vented the remaining gas. Everyone checked their shorts because that was not expected.
After we ran around to make sure there weren't any fires we all kinda relaxed a bit. We walked back around expecting to see the motor split open or in pieces. The smoke was still coming out of the bunker and as it slowly cleared , I was surprised to see the motor for the most part was intact. The cooling jacket had migrated down about two inches. I happened to look down at the ground around the outside of the bunker and found the bottom cooling jacket O-ring. “How did that get there?” was the big question.
Since the big fireball was about thirty feet wide and about forty feet in the air, we decided to disconnect all the gear and head home sooner rather than later. Ken decided he would do a postmortem analysis the next weekend. He wanted time to sort through all the data he collected as well to explain what really happened. Ken will post the data once he figures out what happened based on the video and data together.
Here is Ken's assessment of the what happened during the burn:
“My theory without more detailed post-mortem examination (to occur tomorrow) is: Motor ran for approximately 4-5 seconds with rather unstable combustion (popping sounds) and a lot of exhaust flame. Jacket seal O-rings overheated and became soft. An unknown force, perhaps a water hammer or vibration caused an upward vertical force on the jacket overcoming the small hold down screws and the o-ring friction. The jacket slid up until it was stopped by the motor mount. Then an unknown vertical downward force acted on the jacket driving it down. The jacket caught the softened aft o-ring on its way down and pulled the softened o-ring out of its groove. This allowed kerosene to spew out of the aft end of the motor from the jacket causing the first fire ball. The second fireball was due to increased kerosene flow as the kerosene tank became empty and kerosene was blown out of the lines.”
Video's from the day
Pictures from the Motor Teardown
Pictures from Ken's Liquid motor tewardown with his comments on what really happened after the teardown.
"Post mortem examination showed that the motor ran for 4-5 seconds until the nozzle throat burned through. The aft end of the motor (throat and nozzle) blew off tugging the jacket with it. Don has pics. Cooling of that region of the chamber as totally inadequate. LRM 2 is already in the works."
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