The Hydra Saga

I originally got the Formula 98 rocket, which I have lovingly named “Hydra,” to get some experience with launching level 2 high-powered rockets. I had previously gotten my M1 high-powered rocket certification, which allowed me to launch rockets of any level up to the level of my dad’s license. At the time, my dad only had a level 1 high-powered rocket license but was planning to start working on getting his level 2 license, which involved showing that he could build and launch a level 2 high-powered rocket. Since I wanted to get experience from this as well, we decided that we would both build level 2 high-powered rockets at the same time.

The construction of Hydra proceeded mostly as planned, with a few minor hiccups, but nothing too major. The rocket itself was made out of 98 mm fiberglass. It has a 54 mm motor mount capable of holding a J-class rocket engine, the lowest type still considered “level 2.” Since I was working towards a level 2 certification, I wanted to start on the lower end of the qualifying motor size. This rocket was significantly more complicated than all of the previous rockets I had built, as it incorporated a feature known as “dual-deploy” to minimize the drift distance as the rocket descends. Normally, when a rocket is stopping its ascent, a parachute is deployed that slows the rocket’s descent to an acceptable speed so the rocket does not break. However, this can lead to a drift distance comparable to the altitude reached, which is obviously not ideal for flights with maximum altitudes of over a few thousand feet. As such, this rocket utilized a “Telemetrum” avionics system made by Altus Metrum. It is designed to detect the maximum altitude, or apogee, at which time it deploys a very small “drogue” parachute to slightly slow and stabilize the rocket’s descent. At a specific lower altitude, a second, much larger parachute is deployed, to slow the rocket to a final landing speed so it can land safely. This system is much more complicated than a single parachute deployed at apogee by the motor, but it decreases drift distance significantly.

The first launch of the Hydra began well – all of the components were in place, the telemetry was working, and so on. The rocket was on the launch pad for a considerable amount of time in the heat waiting for other launches to complete and for high winds to die down. All the time, the altimeter was transmitting, sending telemetry. I was somewhat unfamiliar with the chemistry of the lithium-ion battery being used and did not recognize that the battery voltage had fallen to a sub-optimum level. The rocket lifted off the pad, burned through its motor, ascended nearly a kilometer, and then the drogue chute ejected. There was immediately a problem -- although the rocket had separated and ejected the drogue chute as planned, the drogue chute tangled, and did not fully deploy. Even worse, the main parachute did not deploy at all, and the rocket simply fell back to the ground at a higher-than-planned speed. It landed on concrete sustaining moderate damage. The tip of the nosecone was slightly damaged, and two of the three fins were knocked loose. Upon examining the telemetry, I discovered that the battery voltage had fallen to a point that the altimeter was reset when it tried to fire the apogee ejection charge, resulting in the altimeter not knowing when to fire the main charge to release the main parachute.

After examining the data available from the first launch, I determined that the best course of action would be to implement a dual-redundant, dual-deploy system. The new system consists of the Telemetrum with a dedicated battery, and a backup system, a Stratologger CF made by PerfectFlite, with its own dedicated battery. The two systems operate independently, sharing no components.

Once a plan was in place, I got started repairing the damage to the rocket. The damaged portion of the nosecone had to be rebuilt and reshaped. Replacement fins were procured and installed, and I updated the electronics bay to hold the additional components.

Stay tuned for results of the second launch coming soon.