General Description of Sounding Rockets

Introduction

Sounding rockets take their name from the nautical term "to sound", which means to take measurements. NASA currently launches 14 different sounding rockets, ranging from the Arcas (7ft tall, 30 mile apogee) to the Black Brant XII (65ft tall, 800 mile apogee).

Sounding rockets are used to study the Earth's atmosphere at many different altitudes and the Earth's ionosphere and aurora. Also, since sounding rockets can get above the atmosphere, they are used to study astronomical targets in the ultraviolet and x-ray portions of the electromagnetic spectrum.

Why use Sounding Rockets?

Sounding rockets have an advantage over other forms of space-borne experiments for the following reasons.

Cost - Compared to large orbital satellites and shuttle based experiments, sounding rockets are relatively inexpensive.
Development Speed - Sounding rocket payloads can be developed quickly and from pre-existing equipment used on previous flights.
Opportunity - Since sounding rockets can be developed quickly and at low cost, they are perfect for making observations of "targets of opportunity," such as comet Hale-Bopp, which could not be observed by the Hubble Space Telescope near perihelion, due to the sun avoidance rule.
Mid-Altitude - Sounding rockets are uniquely qualified to study the Earth's atmosphere in the altitude range inaccessible to balloons (maximum altitude ~30 miles) or satellites (minimum altitude ~100 miles).
Instrument Development - Sounding rockets can also provide a test bed for the development of instruments that may be used on some of the larger missions. For example, the International Ultraviolet Explorer (IUE), the Hopkins Ultraviolet Telescope (HUT), and even the recently launched TRACE satellite were based on sounding rocket payloads.
Education - Also, because of the short development time and low cost, sounding rockets provide experience for graduate students to learn the valuable tools of the scientific field.

NASA Facilities

NASA maintains the following sites for the development and launch of sounding rockets.

Wallops Flight Facility ( WFF), Wallops Island, Virginia - Wallops is responsible for many aspects of the rocket flight, including payload design and integration of the experiment. Integration involves the testing of all payload components as well as the hand-shaking between the experiment and the rest of the payload.
White Sands Missile Range (WSMR), New Mexico - Provides further integration facilities, launch vehicles, and launch site.
Poker Flat Research Range, Fairbanks, Alaska - Same facilities as WSMR, but used more often for auroral studies.
Also, temporary launch facilities have been set up in places such as Puerto Rico, Peru, Greenland, Australia, and even an aircraft carrier in the Pacific Ocean.

ANATOMY OF A SOUNDING ROCKET

A sounding rocket comprises two main sections:

Solid-fueled rocket motor(s)
Payload

Rocket Motor

As mentioned earlier, NASA launches 14 different sounding rockets, however the Johns Hopkins Rocket Program has mostly been using the Black Brant IX of late. This is a two stage solid-fueled rocket. The first stage is a Terrier booster, originally developed by the Applied Physics Laboratory (APL) of the Johns Hopkins University. The second stage is a Black Brant motor, built by Bristol Aerospace.

Payload

The specific make-up of a sounding rocket payload will depend on the mission, however there are some components that most payloads have in common. The following is a list of the payload sections flown on recent JHU Rocket Program flights:

Nose Cone/Ogive Recovery System Assembly (ORSA) - The ORSA contains the parachute and the ACS pitch and yaw jets.
Attitude Control System (ACS) - Aerojet Mark VI. The ACS controls the payload orientation using a programmed microcomputer and pitch, yaw, and roll jets. It has an accuracy of +/- 2-5 arcmin on nontrackable targets and a 10 arcmin/min drift rate.
S-19 Boost Guidance Control System - Boost phase guidance made by Saab. Its main purpose is to reduce impact dispersion and acquire accurate trajectories. With the S-19, the rocket is able to launch to higher altitudes and in higher winds. Gyros detect pitch and yaw angles and pneumatic servos turn pairs of canards to adjust the trajectory during the boost phase of the flight.
Telemetry - The Telemetry section is the "central nervous system" of the rocket payload. It transmits all the data down to the ground station, including the "housekeeping" data, the science data, and any other signals. It can also receive uplink commands that steer the rocket.
Experiment - The experiment section most recently flown by the Rocket Program was designed and developed at JHU and comprises a 40 cm diameter f/15 Dall-Kirkham telescope and long-slit spectrograph.
High Velocity Separation System (HVSS) - The HVSS connects the rest of the payload to the motors by a v-band. This v-band is held together with four screws which at the appropriate time are cut by explosives and the v-band released. This allows four springs (~400 lbs of force each) to expand and push the payload from the Black Brant at about 10 feet per second.
Ignitor Housing - This section contains the yoyo-despin system and the thrust termination system. After the Black Brant has burned out, the rocket is spinning at about 4 cps. The yoyo-despin releases a weight attached to a long wire coiled about the rocket, thus carrying away angular momentum. Any residual spin is adjusted for by the ACS roll jets. The thrust termination system, consisting of explosives affixed to the motor, is used if the impact dispersion is greater than the safety limits.

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