Back in 2005, USC's Rocket Propulsion Lab launched its first ever rocket: Del Carbon. Nearly ten years later, RPL launched Del Carbon's new and improved sister: Del Carbon Extreme, or DCX. Designed to reach nearly 264,000 feet and speeds up to Mach 6, DCX would soar more than twice as fast and 26 times higher than Del Carbon. At 11:53am, October 18th, 2014, DCX took to the skies above Black Rock Desert, Nevada, to demonstrate the amazing progress RPL has made.
Before launch, the lab worked tirelessly to make DCX a reality. Smaller than our spaceshot vehicle Traveler, DCX had a six-inch diameter carbon-fiber motor case containing 80 inches of solid rocket propellant. Featuring a three-part stainless steel/phenolic/graphite nozzle and topped by a 31-inch nose cone with a beautiful Titanium tip, DCX stood tall at an impressive 12 feet. Improving upon the famed Traveler, DCX incorporated several changes that made its flight even more promising.
First, our ever-improving filament winder created DCX's motor case. In the past, creating a rocket motor case took at least three days of continuous effort using the most ambitious Rocket Lab members. Sheets of carbon fiber were layered over each other and wrapped around a mandrel by hand, a labor-intensive process. With the filament winder, an elaborate computer code took the reins, and DCX's motor case was completed in less than a day. Quickly and efficiently, the filament winder wrapped continuous strands of carbon fiber at different orientations around the mandrel. Human error was eliminated! In fact, the filament-wound DCX motor case immediately passed our hydrostatic pressure test and was deemed flight-worthy.
DCX also contained upgrades to our standard avionics package. Per usual, DCX sported a Raven Altimeter, which measured altitude, velocity, and acceleration of the rocket. In addition, DCX served as a platform for testing another commercial unit, a RealFlightSystems GPS. The RealFlightSystems GPS combined a GPS and transmitter system and could transmit live telemetry and GPS data over a 40 mile range, operating on a different frequency from our other telemetry units. The addition of the RealFlightSystems product increased redundancy of the system and would allow us to qualify a new GPS chipset and telemetry transmitting method.
Now, for Rocket Lab's favorite part of DCX: the propulsion system. DCX added oxamide to RPL’s standard ammonium perchlorate/aluminum propellant. Oxamide acts as a burn rate suppressant, slowing down the propellant's burn while minimally impacting motor efficiency. For high-altitude flights, a longer burn is desirable. A longer burn results in less momentum lost to drag in the lower atmosphere. By slowing down our trip through the lower atmosphere, oxamide also reduces the maximum aerodynamic loading on the vehicle. Most importantly, the addition of oxamide helps our rockets fly higher with the same amount of propellant, cutting costs and saving mass.
Now, with an understanding of DCX's design, return to the morning of October 18th, 2014. The launch day began early, with a 7:00am wake up to prep for our 11:00am flight window. After munching on PopTarts around the campfire, the lab shook off the cold desert air and got to work. With a team of wide-eyed freshmen, Preston Fegley, leader of the launch tower team, erected the 16-foot tall aluminum launch rail on a tripod of steel legs. After successful rocket integration, Jake Hunter and Allie Gehris prepared igniters from left-over propellant while Carter Allen, Nick Orenstein and Jason Silverman kept busy preparing the avionics system for flight. The three musketeers of rocket recovery, Alex Coco, Tyler Ahlf, and Merritt Opdycke, crunched the drogue parachute, main parachute, two Go-Pro cameras, and shock cord into a small package and placed them upon the forward motor bulkhead. At around 11:10am, Brandon Edelson, our fearless leader, had the honor of securing the nose cone into place atop DCX with shear pins. DCX was complete and ready to fly!
Fast forward to 11:53am. A loose e-match used to trigger parachute deployment pushed back the launch time, but thanks to some miracle working by the avionics team, DCX was back on the launch rail and pointed towards the Black Rock sky in less than a half hour. Igniters in place and pre-launch safety protocols complete, Brandon inserted the key into the launch box and started the countdown sequence. As Brandon shouted ignition, flames shot from the nozzle, and DCX soared towards the sun in a cloud of dust and exhaust. As DCX rose, the rocket stood in stark contrast with the barren desert and surrounding mountains, a beautiful scene capturing two months of hard work.
T-plus 9 seconds (9 seconds after launch), we heard a pop coming from the sky. Suddenly, DCX's speed noticeably decreased, and its main parachute surprisingly emerged just above 10,000 feet. Gravity took over, and DCX plummeted towards the desert floor about a half mile from our launch site. Despite being incredibly overbuilt, DCX had failed to operate as expected, and the lab wanted answers.
For the next two hours, the lab banded together to form a search party, combing a two-mile wide stretch of desert looking for clues as to why DCX failed. Most prevalent were pieces of propellant grains and the carbon fiber motor case, which were dispersed in a fan-like pattern across the lakebed. The motor bulkheads were found hundreds of yards from each other, and the main parachute had been completely shredded. Back in the launch operations trailer, Carter and Jason watched launch footage, attempting to piece together visual clues with the rocket remains.
Back at the lab, several weeks of CSI-style investigation and a full rocket reconstruction revealed the cause of failure. By examining the charring on the propellant grains and motorcase interior, we realized that the motor thermal protection system had failed. Hot combustion gases from the motor burned through the carbon case near the forward bulkhead, essentially shearing the case in half. The ensuing explosion ejected the forward motor bulkhead, main parachute, and avionics package. From there, DCX did not stand a chance, falling ballistically back to Earth in shreds.
Some may say DCX was a failure. We don't think so. DCX marked another successful Rocket Lab launch. We had a great launch day that demonstrated the competency and growth of the lab. On launch day, no engineering leads scrambled for parts or had subsystems that failed to be integrated on time. Systems were seamlessly integrated with each other, allowing us to launch early in the flight window. A minor wiring failure was the only mishap- pretty impressive for a large-scale amateur rocket launch. Then, even after the explosion, the lab came together to pick up the pieces, learn from our mistakes, and become better prepared for the next launch. Perhaps more impressive were the new faces getting involved in Rocket Lab- Allie, Carter, Merritt, Tyler, and Preston are only sophomores. A new generation of rocket scientists proved they are hungry to make an impact on the future of Rocket Lab. And who knows what they can achieve! Another try for space is in the lab's near future. The progress RPL has seen from Del Carbon to DCX is truly awe-inspiring, and we cannot wait to discover what another ten years of Rocket Lab evolution will bring us.