Sounding rockets

A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to carry instruments from 50 to 1,500 kilometres (31 to 932 mi) above the surface of the Earth; the altitude generally between weather balloons and satellites (the maximum altitude for balloons is about 40 kilometres (25 mi) and the minimum for satellites is approximately 120 kilometres (75 mi)). Certain sounding rockets, such as the Black Brant X and XII, have an apogee between 1,000 and 1,500 kilometres (620 and 930 mi); the maximum apogee of their class. Sounding rockets often use military surplus rocket motors.NASA routinely flies the Terrier Mk 70 boosted Improved Orion lifting 270–450-kilogram (600–990 lb) payloads into the region between 100 and 200 kilometres (62 and 124 mi).

The origin of the term comes from nautical vocabulary to sound, which is to throw a weighted line from a ship into the water to measure the water's depth. The term itself has its etymological roots in the Portuguese / Italian / Spanish and French words for probe, which are "sonda" and "sonde", respectively. Sounding in the rocket context is equivalent to taking a measurement.

A common sounding rocket consists of a solid-fuel rocket motor and a science payload. Larger, higher altitude rockets have 2 to 3 stages to increase efficiency and payload capability. The freefall part of the flight is an elliptic trajectory with vertical major axis allowing the payload to appear to hover near its apogee. The average flight time is less than 30 minutes, usually between five and 20 minutes. The rocket consumes its fuel on the first stage of the rising part of the flight, then separates and falls away, leaving the payload to complete the arc and return to the ground under a parachute.

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