American students’ amateur rockets reach record heights

The Aftershock II rocket, 4 m high and weighing 150 kg, was launched from the Black Rock desert, Nevada, on October 20. This rocket was designed and built by a group of students at the Rocket Propulsion Laboratory (RPL) of the University of Southern California (USC). RPL is run entirely by university students.

Just 2 seconds after launch, Aftershock II surpassed the sound barrier and reached a maximum speed of about 5,800 km/h (Mach 5.5) after 19 seconds. The engine then stopped working, but the rocket continued to rise due to gradually decreasing atmospheric resistance. Aftershock II left Earth’s atmosphere after 85 seconds and reached its peak at 143,300 m after the next 92 seconds.

This altitude far exceeds the previous record of 115,800 m set by the GoFast rocket of the China Civil Space Exploration group in 2004. USC representatives said this is the “farthest altitude in space of any group”. non-governmental and non-commercial has ever achieved”.

“This achievement represents some of the first technical advances,” said Ryan Kraemer, a mechanical engineering student at USC and executive engineer on the RPL team, who will soon join SpaceX’s Starship team. Aftershock II features the most powerful solid fuel engine ever built by a student and the most powerful composite-shell engine built by an amateur.”

The rocket also reached a top speed of 5,800 km/h (Mach 5.5), slightly faster than GoFast’s 20-year record. It wasn’t just the height and speed records that Aftershock II broke.

To achieve this achievement, the Aftershock II team applied new advances in thermal protection technology, an important factor when the missile moves at supersonic speeds (above Mach 5). They coated the Aftershock II with a new heat-resistant paint and equipped it with titanium fins instead of the carbon material of previous models.

“Thermal protection at hypersonic speeds is a major challenge at the industry level. The upgrades the team made worked flawlessly, allowing the rocket to return nearly intact,” said Kraemer. However, the thermal effect was so strong that the titanium blades turned from silver to blue due to an “anodizing” process, in which the metal reacts with atmospheric oxygen to create a layer of titanium oxide.

The team also designed a new controller for sensing, telemetry and electronic recovery (HASMTER) to monitor the rocket’s flight and parachute deployment.

In 2019, another group of RPL students became the first group of students to launch a rocket across the Kármán Line, the boundary between Earth and space. Aftershock II is the second student rocket to achieve this milestone.

“This is an extremely ambitious project not just for a group of students but for any engineering group,” said Dr. Dan Erwin, aerospace engineer and chair of the USC Department of Space Engineering. any non-professional rocket engineer. It demonstrates the excellence we seek to develop in our future space engineers.”