What Are Sounding Rockets?

Sounding rockets take their name from the nautical term "to sound" which means to take measurements. They are basically divided into two parts -- a solid fueled rocket motor and the payload. Many of the motors used in program are surplus military motors which keeps down the cost of the rocket. The payload is the section which carries the instruments to conduct the experiment and sends the data back to Earth.

NASA currently uses 14 different sounding rockets. The rockets come in a variety of sizes from the single-stage Super Arcas which stands 7-feet (3 meters) high to the four-stage Black Brant XII which stands at 65 feet (20 meters) tall. These rockets can carry scientific payloads of various weights to altitudes from 30 miles (48 km) to more than 800 miles (1,287 km).

Wallops is responsible for all aspects of a mission, from the launch vehicle, to payload design and development, to data retrieval. Scientific data are collected and returned to Earth by telemetry links, which transfer the data from the sounding rocket payload to the researchers on the ground. In most cases, the payload parachutes back to Earth, where it is recovered and reused.

Why NASA Uses Sounding Rockets

Sounding rockets are low cost and the payload can be developed as quickly as six months. These rockets allow scientists to conduct investigations at a specified time and place and they provide the only means of making in-situ measurements at altitudes between the maximum altitudes for balloons (about 30 miles or 48 kilometers) and the minimum altitude for satellites (100 miles or 161 kilometers).

The experiments provide a variety of information, including chemical makeup and physical processes taking place in the atmosphere; the natural radiation surrounding the Earth; and data on the Sun, stars, galaxies and many other phenomena. In addition, the sounding rocket provides a reasonably economic means of conducting engineering tests of instruments and devices used on satellites and other spacecraft prior to their use in more expensive activities. Also, because of their low cost and short mission lead time, they are valuable tools for students conducting graduate work in scientific fields.

NASA launches an average of 30 sounding rockets each year with a success rate of about 98 percent. They are launched routinely from established sites such as Wallops Island; White Sands Missile Range, New Mexico; and Poker Flat Research Range, Alaska, as well as sites in Canada, Norway and Sweden.

Sounding rockets also can be launched from temporary launch ranges. In the past, launch programs have been conducted from Peru, Puerto Rico, Greenland, Australia, and even from an aircraft carrier in the Pacific Ocean.

Flight Profile

The flight profile of a sounding rocket follows a parabolic trajectory -- it goes up and comes back down. Flight time is less than 30 minutes.

Following launch, as a rocket motor uses its fuel it separates from the vehicle and falls back to Earth. The payload continues into space after separating from the motor(s) and begins conducting the experiment. When the experiment is completed, the payload reenters the atmosphere and a parachute is deployed bringing the payload gently back to Earth. The payload is then retrieved. By retrieving the payload, a tremendous savings can be achieved because the payload or parts of the payload can be refurbished and flown again.