General Description of Sounding Rockets
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
Why use Sounding Rockets?
Sounding rockets have an advantage over other forms of space-borne
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
- 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
Ultraviolet Telescope (HUT), and even the
recently launched TRACE satellite
were based on sounding
- 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 maintains the following sites for the development and launch of
- 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
- 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)
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.
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
- 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
- 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
- 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.