Sounding rocket

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A sounding rocket, sometimes called a research rocket, is an instrument-carrying suborbital rocket designed to take measurements and perform scientific experiments during its flight. The origin of the term comes from the nautical term to take a sounding, meaning to take a measurement.<ref name=what>Marconi, Elaine M. (April 12 2004). What is a Sounding Rocket?. Research Aircraft. NASA. Retrieved on October 10, 2006.</ref>

The rockets are commonly used to take readings or carry instruments from 50 to 1,500 kilometers (30–932 mi) above the surface of the Earth, the altitude in between weather balloons and satellites, the region above the maximum altitude for balloons is approximately 40 km and the minimum for satellites is approximately 120 kilometers (75 mi)<ref name=overview>NASA Sounding Rocket Program Overview. NASA Sounding Rocket Program. NASA (July 24 2006). Retrieved on October 10, 2006.</ref>. Certain sounding rockets, such as the Black Brant X and XII, have an apogee between 1,000 and 1,500 kilometers (621–932 mi), well above Low Earth Orbit. Sounding rockets often use military surplus rocket motors.<ref name=what/> NASA routinely flies the Terrier Mk 70 boosted Improved Orion lofting 270–450 kilogram (600–1000 lb) payloads into the exoatmospheric region between 100 and 200 kilometers (62–124 mi).

A common sounding rocket consists of a solid-fuel rocket motor and a payload.<ref name=what/> The freefall part of the flight is an elliptic trajectory with vertical major axis allowing the payload to appear to hover near its apogee<ref name=overview/>. The average flight time is less than forty minutes, usually between 5 and 20 minutes<ref name=overview/>. 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 with a parachute.<ref name=what/>

Sounding rockets are advantageous for some research due to their low cost<ref name=overview/>, short lead time (sometimes less than six months)<ref name=what/> and their ability (as mentioned above) to conduct research in areas inaccessible to either balloons or satellites. They are also used as test beds for equipment that will be used in more expensive and risky orbital missions.<ref name=overview/> The smaller size of a sounding rocket also makes launching from temporary sites possible allowing for field studies at remote locations, even in the middle of the ocean, if fired from a ship.<ref>General Description of Sounding Rockets. Johns Hopkins University Sounding Rocket Program. Retrieved on October 10, 2006.</ref>