Sounding Rocket

Overview

A sounding rocket is an unguided suborbital vehicle that carries instruments into the upper atmosphere and back, following a steep ballistic arc rather than reaching orbit. The name comes from the nautical sense of "to sound", to probe, and the rockets fill the altitude gap between balloons and satellites, sampling regions too high for aircraft and too low for spacecraft. Because the vehicle is fin-stabilised and unguided, simplicity and reliable recovery matter more than precision.

The rocket is a stack of body tubes around a propulsion core. The Solid Rocket Motor is a reloadable solid motor that provides all the impulse in the first few seconds of flight. Above it the Airframe carries structural loads and the stabilising fin can, the Recovery System system brings the vehicle down safely, the Payload Bay holds the science instruments and telemetry, and the Avionics Bay runs the flight computer and event sequencing beneath the Nose Cone.

How it works

At ignition a pyrogen igniter lights the propellant grain. The composite propellant burns from its exposed surfaces, generating high-pressure gas that accelerates through the graphite-throated nozzle to produce thrust. The four fins set well aft of the centre of gravity keep the rocket pointed into the airflow, stabilising it aerodynamically as it accelerates off the launch rail.

After burnout the rocket coasts upward to apogee, where the science package samples the atmosphere and radiation environment while telemetry streams to the ground. The avionics detect apogee from the onboard barometer and inertial sensors and fire the first ejection charge to deploy a small drogue parachute, limiting descent speed. At a preset low altitude a second charge releases the main parachute for a soft landing, allowing the airframe and instruments to be recovered and reflown.