The ocean is a logistically remote environment, in the sense that
conventional combustible fuels can’t be used underwater unless supplied
with their own sources of oxygen. It is usually extremely costly to take
anything heavy or bulky into the deep ocean. Even if the two essential
components of combustion—fuel and oxygen—could be delivered economically
to an undersea base or craft, the extreme back pressure of the depths
would present serious exhaust problems. Yet deep beneath the sea is just
where we now propose to do large amounts of work requiring huge supplies
of reliable energy. The lack of reliable and extended duration power
sources is perhaps one of the most critical requirements for expansion
of underwater and marine technology. For example, the pressing need for
measurements of atmospheric and oceanic data to support scientific,
commercial, and military operations will in the future require literally
hundreds of oceanographic and meteorological buoys deployed throughout
the world to take simultaneous measurements and time-series observations
at specific sites.
Some of these buoys will support and monitor up to 100 sensors each.
These devices record a variety of physical, chemical, and radiological
phenomena above, at, or below the surface. Periodically the sensor data
will be converted to digital form and stored on magnetic tape for later
retrieval by distant shore-based or shipboard radio command, by
satellite command (for retransmittal to ground stations), or by physical
recovery of the tapes. Individually, each buoy will not require a great
deal of energy to operate, but will have to operate reliably over long
periods of time. Conventional power sources are being used for the
prototype buoys now under development and testing, but these robot ocean
platforms in the future will make excellent use of nuclear energy
supplied by isotopic power sources.
[Illustration: _The world’s first nuclear-powered weather buoy
located in the center of the Gulf of Mexico. This weather station,
part of the U. S. Navy’s NOMAD system, is on a barge 10 feet × 20
feet, and is anchored in 12,000 feet of water._]
[Illustration: diagram]
RADIO ANTENNA
WEATHER SENSORS
WARNING BEACON
NUCLEAR GENERATOR
The SNAP-7D isotope power generator has been operating unattended since
January 1964 on a deep-ocean moored buoy in the Gulf of Mexico. This U.
S. Navy NOMAD (Navy Oceanographic and Meteorological Automatic Device)
buoy is powered by a 60-watt, strontium-90 radioisotope source, which
was developed by the AEC Division of Reactor Development and Technology.
This weather station transmits data for 2 minutes and 20 seconds every 3
hours. This data includes air temperature, barometric pressure, and wind
velocity and direction. Storm detectors trigger special hourly
transmissions during severe weather conditions. The generator operates
continuously and charges storage batteries between transmissions. Some
power is used to light a navigation beacon to alert passing ships.
Energy from the heat of radioisotope decay has been used on a
“proof-of-principle” basis in several other instances involving ocean or
marine technology.
An experimental ⁹⁰Sr isotope-powered acoustic navigation beacon
(SNAP-7E) now rests on the sea floor in 15,000 feet of water near
Bermuda. Devices such as these not only will enable nearby surface
research or salvage vessels to locate their positions precisely
(something very difficult to do at sea) and to return to the same spot,
but the beacons also will aid submarine navigation (see page 48).
A U. S. Coast Guard lighthouse located in Chesapeake Bay has been
powered by a 60-watt, ⁹⁰Sr power source, SNAP-7B, for 2 years without
maintenance or service. This unit was subsequently relocated for use in
another application (described below).
[Illustration: _Engineers prepare to install the SNAP-7D
generator._]
The first commercial use of one of these “atomic batteries” began in
1965 when the SNAP-7B 60-watt generator went into operation on an
unmanned Phillips Petroleum Company offshore oil platform, 40 miles
southeast of Cameron, Louisiana. The generator operates flashing
navigational lights and, in bad weather, an electronic foghorn (see page
49). This unit will be tested for 2 years to determine the economic
feasibility of routinely using isotopic power devices on a commercial
basis.
[Illustration: Acoustic pulses.]
Buoyancy tank
Sound amplifier
Nuclear-powered sound source
Ocean bottom
[Illustration: _The SNAP-7E isotopic generator powers an undersea
acoustic beacon, which produces an acoustic pulse once every 60
seconds. In addition to being a navigation aid, the beacon is used
to study the effects of a deep-ocean environment on the transmission
of sound over long distances._]
[Illustration: Diagram.]
Total height: 10 ft 2 in
Armored cable
Pressure vessel
Capacitor bank
Fuel capsules
Biological shield
Equipment package
Voltage converter
Depleted uranium
Thermoelectric generator
System support structure
[Illustration: _Details of the Phillips Petroleum platform, which
uses the SNAP-7B nuclear generator._]
[Illustration: _The final electrical connection is made from the
nuclear generator to the platform’s electronic foghorn and two
flashing light beacons._]
[Illustration: Diagram]
Fog Horn
Beacon
Beacon
Snap-7B nuclear generator
The radioisotope-powered devices previously described were developed by
the AEC under the SNAP-7 Program.[16] The testing of these units has
demonstrated the advisability of developing reliable and unattended
nuclear power sources for use in remote environments without compromise
to nuclear safety standards. As a result of the success of these tests,
a variety of potential oceanographic applications have been identified.
A study, conducted by Aerojet-General Corporation in conjunction with
Global Marine Exploration Company and Northwest Consultant
Oceanographers, Inc., described ocean applications including underwater
navigational aids, acoustic beacons, channel markers, cable boosters,
weather buoys, offshore oil well controls along with innumerable
oceanographic research applications. This study was sponsored by the AEC
Division of Isotopes Development.
In order to satisfy the requirements for these and other applications,
the AEC has begun developing a series of compact and highly reliable
isotope power devices that are designed to be economically competitive
with alternative power sources. Currently underway are two specific
projects, SNAP-21 and SNAP-23.
SNAP-21 is a two-phase project to develop a series of compact
strontium-90 power systems for deep-sea and ocean-bottom uses
(20,000-foot depths). The first phase of design and component
development on a basic 10-watt system already has been completed, and a
second phase development and test effort now under way will extend
through 1970. A series of power sources in the 10- and 20-watt range
will be available for general purpose deep-ocean application.
The SNAP-23 project involves the development of a series of economically
attractive strontium-90 power systems for remote terrestrial uses. This
project will result in 25-watt, 60-watt, and 100-watt units capable of
long-term operation in surface buoys, offshore oil platforms, weather
stations, and microwave repeater stations.
In addition to the above, effort is underway by the AEC to develop an
isotope-fueled heater that will be used by aquanauts in the Navy’s
Sealab Program (see page 12). Future activities, now being planned, will
involve the development of large isotope power sources (1-10 electric
kilowatts) and small nuclear reactors (50-100 kilowatts) for use in
manned and unmanned deep-ocean platforms.