US student's amateur rocket reaches record height

A team of students from the University of Southern California launched the Aftershock II rocket, reaching an altitude of 143.3 m above the Earth's surface, breaking many records of previous amateur groups.

The 4-meter-tall, 150-kilogram Aftershock II rocket was launched from the Black Rock Desert in Nevada on October 20. The rocket was designed and built by a team of students at the University of Southern California's (USC) Rocket Propulsion Laboratory (RPL). RPL is run entirely by university students.

Just two seconds after launch, Aftershock II broke the sound barrier and reached a top speed of about 5,800 km/h (Mach 5.5) after 19 seconds. The engine then stopped working, but the rocket continued to fly as atmospheric drag gradually decreased. Aftershock II left the Earth's atmosphere after 85 seconds and reached its peak altitude of 143,300 m after another 92 seconds.

Afterschock II reached a maximum altitude of 470,000 feet (143,300 m) above the Earth's surface, higher than any other amateur rocket. (Photo: USC Viterbi School of Engineering).

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

'This achievement represents a number of technical firsts, ' 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-hulled engine ever 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-old record. It's not just altitude and speed records that Aftershock II has broken.

To achieve this feat, the Aftershock II team applied new advances in thermal protection technology, which is important when the missile is traveling at hypersonic 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 industry challenge,' Kraemer said . 'The upgrades the team made worked perfectly, allowing the rocket to return almost intact.' However, the intense heat caused the titanium fins to turn from silver to blue due to a process called 'anodization,' in which the metal reacts with atmospheric oxygen to form 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 RPL student team became the first to launch a rocket across the Kármán Line, the boundary between Earth and space. Aftershock II is the second student rocket to reach this milestone.

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