By Timothy Raney…Bald Engineer Guy with Glasses
This time, we’ll wrap-up this mesmerizing series with its exhilarating conclusion – final preparation and the first flight. Golly, who knows what will happen?
The Final Preparations
Yes, the beginning of the end. I began the final preparations by finally configuring the payload bay. It was only a two minute task since I had already made the bulkhead some weeks ago. Once again, I used two-part epoxy and spread it circumferentially with a small spatula within the payload bay. With the epoxy spread about 2” in from the forward end, the bulkhead was then slid into place. Afterwards, I cut a piece of foam to hold the altimeter securely and cushion it. Wow, I should patent it: a piece of foam with a hole in it for the altimeter. I could make millions. Well, maybe not. Sometimes I have these delusions, kind of like the exceedingly ingenious, but ill-fated laser guided window fan or the “sporf” – a combined spoon and knife. Ouch. Moving along to more constructive pursuits, I attached the 24” diameter recovery parachute to the shock cord about 2-feet from the nosecone. Nothing magic here, nor I can offer an in-depth scientific explanation beyond citing some experience in this topic. Wait a minute, it’s coming to me.
Oh yeah, there is another factor. The very real desire to avoid a recovery system failure where the rocket plummets to earth and becomes one with the ground. It’s not pretty and it is dangerous. So, I then loaded the parachute and shock cord, ensuring it could slide out easily once ejected by the expulsion charge. I then printed the technical materials for the first flight and made a “High Power Rocket Level-1 Certification” binder. The materials included the NAR certification form, results from the simulation attesting to the rocket’s stability, instructions for loading the Cesaroni H100 reloadable motor, the flight simulation with the predicted performance/altitude and motor specifications. No, I didn’t go overboard – at least in my simple mind.
By reviewing this information, running the simulations and generally studying this topic, I felt ready for the certification attempt. And importantly, I could answer most or all questions about the rocket. This is important. You must demonstrate a good grasp of the details involved with building and launching a high power rocket safely. You must also ensure you convey this knowledge to the Level-1 certifier since they are the ones to decide if your rocket is safe to fly….before it’s ever flown. Though not to the same degree as designing a rocket to reach Mars, this is still rocket science. Yes, it is. After all, I’m not just a chimp with opposable thumbs. No offense to chimps – I saw one ride a bicycle once. And they’ve been in space too.
With the rocket loaded, I drove to our launch site. Our “launch facility” is actually a spot in a pasture – sometimes among cows and llamas. It just depends on the farm’s schedule for rotating the pastures. Yes, the Heart of Virginia Association of Rocketry (HOVAR), NAR Section #704 conducts its monthly launches in a cow pasture. It’s a very beautiful location too – we are very lucky the landowner has given use permission to launch there. Well, once we had all the equipment set-up, I met with Kevin to begin the certification process. It was informal, but I was still required to discuss the rocket’s construction and the simulation results attesting to its stability and so.
As a Level-1 certifier, Kevin can determine if the rocket is potentially safe or dangerous by examining its construction too. He did just that as I answered his questions. He then provided me with a Cesaroni H100 reloadable motor, its casing, spacers and igniter. We also discussed the simulation results that showed the parachute would eject when the rocket’s velocity was too high. In one case, it showed parachute deployment at 160mph. A speed this high could cause the chute to fail. You really want the chute to deploy when the rocket’s speed is in the 40mph range. So, as it turned out, I had not adjusted the ejection charge delay from its default 15 seconds to a lesser value before running the simulations. Thus, the rocket was beginning to accelerate due to the inevitable forces of gravity. The mystery was solved. Kevin showed me how to use the expulsion charge delay setting tool next. We then used the graphed flight simulation to determine the delay – 7.5 seconds in this instance. I used the tool to remove enough of the delay train composition to equal a 7.5 second delay. Lastly, I loaded the adjusted delay module, two propellant grains and a spacer into the motor casing. Thus completed, the motor was inserted into its mounting tube within the rocket’s aft airframe and the retainer was secured.
All Systems Go – It’s Time
With everything checked, I took the rocket to the launcher. I lowered the launch rail to the loading position and slid the rocket into place. The rocket’s launch buttons fit the rail nicely too. I raised the rail, locking it into position. I ensured the 12-volt battery power supply was “cold” with its switch in the off position. Inserting the igniter into the H100 motor was next. Lastly, I connected the igniter’s wire leads to the power supply. All connections were checked again before turning on the battery switch. I took a last look at Rocket #10 as I walked towards the launch controller sitting on a table 100 feet away. Ambient wind speed was ~4mph. Excitement was mounting – at least in my mind.
We Have Ignition
The five second countdown began: 5, 4, 3, 2, 1 – ignition! Yes, we have ignition! The rocket streaked upward – it was a beautiful (stable) flight. The recovery parachute deployed seconds later. The crowd went wild. Though we could barely see it – the rocket’s apogee was estimated at over 3400-feet given the previous flight simulations. Likely the highest flight yet at this field. And we have to contend ourselves with the estimated maximum altitude since stupid me someone did not set the altimeter correctly. I kept my eye on the rocket as it descended. The wind blew it into the next pasture, but I saw where it landed. Some minutes later, I found the rocket – it had landed undamaged – the last criterion for a successful flight and earning a NAR Level-1 High Power Rocket (HPR) certification. Rocket #10 was a success. I hope you enjoyed this series.
“I’m not a rocket scientist, but I could play one on TV.”