Welcome to the Treasure Valley Math and Science Center's Near Space Club. This club designs experiments for exploring near space, which is that region of Earth's atmosphere between 60,000 feet (the top of controlled airspace) and below 328,000 feet (the FAI defined boundary for outer space).
Near space is reached via weather balloons. Yep, our rocket is a huge balloon and the propellant is a lifting gas like hydrogen and helium. An ascent into near space takes around 90 minutes while the descent adds another 45 minutes to the mission. Once in near space, conditions are closer to those found in outer space than to conditions we experience on Earth's surface.