The most impressive nuclear propulsion program to date, and
indeed one of the most impressive US technology-building programs of all time,
is on the verge of collapse. It is not a victim of failure—quite the contrary:
It has achieved an essentially perfect record in meeting or exceeding all
technical, cost/ effectiveness, and budgetary goals over its ten-year life.
The program is Project Pluto. It is aimed at proving the
feasibility of the nuclear-ramjet engine. It has become a key test case in a
running fight between the executive and legislative branches of the government
over how to manage advanced technology programs. In this test-case role,
despite its extremely fine record and great future potential for weapon
systems, Pluto is in imminent danger of being mothballed.
Congress has wholeheartedly supported Pluto in the past and
continues to praise both its technical achievements and potential. But
Congress is now using Pluto to goad the Administration into clarifying its
advanced technology philosophy and military requirement system as currently
The immediate target under congressional attack is an Atomic
Energy Commission request for $8 million to be spent in fiscal year 1965 to
make ground tests of the new flight-weight Pluto reactor, the Tory II-C, and to
begin work on an improved version, the Tory III.
Late in April the Joint Committee on Atomic Energy
recommended a $1.5 million reduction in the AEC's Pluto request. The Joint
Committee explained that it wanted to fund the complete series of Tory II-C
tests, but was not going to back any Tory III development. It agreed fully with
the vast majority of its technical witnesses, who stated that Tory Il-C tests
would prove the feasibility of the nuclear-ramjet engine as well as it would
ever be proven on the ground without flight tests. In other words, Congress is
trying to speed up flight testing by withholding funds for further, and
unnecessary, ground-based development.
Administration spokesmen, including Dr. Harold Brown, DOD
Director of Research and Engineering, have supported a continuation of Pluto
study work and ground tests at a low level of funding (approximately $20
million per year total from USAF and AEC budgets) to keep the technology
The Joint Committee, after several years of criticizing
this philosophy, now completely rejects it. The Committee believes it would be
grossly wasteful to continue a policy that has consumed a little more than $200
million in nearly ten years and kept the program creeping at a minimum pace.
Most Joint Committee members agree with Dr. Theodore Merkle
of the AEC's Livermore Laboratory, the program's technical leader. Late in 1958
Dr. Merkle said flatly that a nuclear ramjet could be built with technical
knowledge that then existed. According to him at that time, "It is just a
question of do you want it or not?" Pluto work during the past five years
has proved Dr. Merkle's contention, and the committee is maneuvering to get the
Administration to answer his question, "Do you want it or not?"
After cutting the FY '65 budget to allow only the completion
of the Tory II-C tests, the Joint Committee stated in its report, "Unless
a decision is made within the next year to flight test the Tory II-C device, it
is an unavoidable conclusion that the [Pluto] program should be
In effect such a decision would mean that the breakup of
the Pluto development team of scientists and engineers would begin on July 1,
at the end of FY '64. Many design and laboratory specialists not directly
connected with the Tory II-C tests would have to be switched to other programs
because the Tory III would not be funded.
The Department of Defense, in an effort to prevent the Pluto
break-up, is studying plans for a flight-test program which would satisfy a
number of diverse factions in the DOD as well as the congressional critics.
Date for a decision was scheduled for July 1, although there is little
likelihood that this schedule will be met —or that the decision will be
announced at that time even if made. The decision must be a tricky one, with
great import for the military. The program will cost between $200 and $500
million, depending upon its sophistication and the number of flight vehicles involved.
If tests should prove successful it would be difficult to
explain why development of an operational system should not be authorized. It
is generally agreed that major strategic weapon systems in the future will be
very expensive and few in number, so the Navy and the Air Force, as well as DOD,
have an intense interest in any potential system which is receiving large development
funds. Many atmospheric, spaceborne, and underseas systems are competing for
the Administration's blessing as the next major strategic weapon system and
to advance from the relatively cheap ground-test stage into a major test
program in the operational environment.
The chances of DOD coming up by July 1 with a Pluto
flight-test program that will be acceptable to the Joint Committee have to be
rated as slim. During the past three years the only clear position that has
emerged from the Pentagon's third floor is that new strategic weapons really
aren't of interest. The current systems, especially the ICBM and the Polaris
missiles, are considered to be invulnerable for far into the future.
Development of improved systems to overcome weaknesses in these weapons and to
present new defensive problems to an enemy generally have been described as
unnecessary and wasteful by Mr. McNamara.
Consequently, it appears highly unlikely that this policy
will be altered to produce a Pluto flight-test program of which the Joint
Committee will approve. The Joint Committee objective, before considering the
authorization of further funding, was to obtain reasonable assurances that the
DOD wanted to go ahead with weapon-system development and could get all the information
it needed out of the prototype flight vehicles.
Early in June a more formidable congressional challenge seems
to have dashed all hope that Joint Committee pressure could have brought about
a Pluto flight-test program. This new challenge is based largely upon the fact
that the first full-power run of the Tory Il-C on May 22 was a complete
success. This was the first of several such runs planned next year for the Tory
Il-C test program which the Joint Committee funded.
The challenge came from the powerful House Appropriations
Committee in a report issued on June 11. The Committee said that the May 22
test "amply demonstrated the successfulness of the ramjet propulsion
reactor powerplant. Since there is still no military system or requirement for
this powerplant and no engine system or vehicle to carry it has been developed
up to this time, the Committee sees no reason why further development and
testing work is necessary." The Appropriations Committee thereupon cut
$5.5 million from the Joint Committee's authorization and said, "The $1
million which has been allowed for this program is for the purpose of 'mothballing'
the project until such times as there is a military system and a requirement
In calling for the generation of a weapon-system requirement
before further funds are made available, the Appropriations Committee has given
Mr. McNamara the task of coming to Capitol Hill and explaining his policy,
unless he wants Pluto to die at once. Mr. McNamara must also justify his
entire technology-building policies. Many congressmen do not believe that the
Secretary is getting maximum effectiveness from his R&D dollar when he
continues to call for $20 million a year for a system that is never going to be
an operational weapon. They cite Mr. McNamara's own extensive statements
about the overriding need for conserving technical resources and investigating
the widest variety of concepts and systems to ensure US technical superiority
into the future. The Congress certainly agrees with this basic objective, but
few of its members will continue to support the expenditure of hundreds of
millions of dollars on systems that the Administration is going to ignore
after they are tested successfully and proven feasible.
It is no accident that the Congress is using Project Pluto
to challenge the Administration. Pluto is revolutionary in every sense.
Militarily, it opens the possibility of operating bombardment/reconnaissance
vehicles in a completely new speed-altitude regime Mach 3, or about 2,300 mph,
at altitudes as low as 500 feet. For practical purposes the range can be
considered as infinite, because there is no technical doubt that the
nuclear-ramjet vehicle could operate for at least twenty-four hours before
radiation and heat would begin to deteriorate any of its subsystems. Therefore,
the vehicle could travel around the world at the earth's maximum diameter while
making extensive dogleg maneuvers. No nation is close to possessing a defense
which could intercept such a high-speed, low-altitude vehicle attacking from
any direction. Developing such a defense would be difficult and costly, at
least in the same class with an anti-ICBM system.
The cost/effectiveness rating of Pluto vehicles must be
very high compared to existing systems. One major advantage is that a
low-altitude nuclear-ramjet vehicle has by far the largest payload of any
flight system yet envisioned. Over twenty-five percent of its weight could be
carried in the form of weapons or other payload. A Mach 3, low-altitude,
vehicle powered by a Tory II-C type reactor would weigh 150,000 to 200,000
pounds or more, and its payload would be more than 50,000 pounds. It could
carry more nuclear weapons, and larger weapons if desired, than a Polaris
submarine, which has a normal complement of sixteen missiles each with a
warhead of under ten megatons. By the same reasoning one Tory II-C powered
vehicle could be more potent than a dozen or so Minutemen.
A second major advantage is a very high guidance accuracy rating for the low-altitude vehicle, even better accuracy than is being attributed today to the inertially guided ICBM. The system consists of a programmed inertial system which is corrected at regular intervals by measuring the differences in height of prominent terrain features along the vehicle's route. Distances from the vehicle to the geographic features also are measured, and the distance and height differential information is fed into a computer which determines the vehicle's exact position and corrects the inertial system.
Ling-Temco-Vought, Inc., developers of the equipment for correcting an inertial-guidance package, already have tested it successfully in flight under all-weather conditions.
These two features—a large payload and an exceptionally
high guidance accuracy—combine to give the nuclear-ramjet vehicle a
high-effectiveness rating compared to current strategic missile systems. The
nuclear vehicle also has aircraft-type advantages in that it can be recalled or
given alternate assignments after a flight has been initiated. And it is vastly
superior to the manned aircraft in range and speed at low altitude and,
consequently, in ability to penetrate enemy defenses.
Initial cost of a Tory II-C powered vehicle purchased in
quantity probably would be considerably less than a B-52 bomber—say $5 million
or less. This estimate seems valid despite the ramjet's requirement for a large
quantity of expensive nuclear fuel. The extreme simplicity of the nuclear
ramjet, plus the fact that its total empty weight would be considerably less
than that of a B-52, would have a controlling influence on cost.
Operational costs also should be relatively low. Keeping
such unmanned vehicles in a state of constant readiness certainly would be much
cheaper than operating a submarine or a large bomber and probably comparable
to the cost of operating one missile silo.
Many perils are inherent in drawing cost/effectiveness
generalizations when a great deal of detailed information is not available on
the weapon system in question, the other offensive systems it must be rated
against, or estimates of the military environment it would have to operate
against in the next five to fifteen years. However, the information available
on low-altitude nuclear-ramjet vehicles, reviewed above, indicates that the
Pluto system offers some unique cost/ effectiveness advantages.
For instance, it appears that a force of 100 nuclear-ramjet
vehicles could be produced for a total cost of under $1 billion in new funds.
Such a force would have a striking strength equivalent to a fleet of sixty
Polaris submarines or more than the entire complex of 950 Minuteman missiles
that is in operation or on order. A nuclear-ramjet vehicle force also would
have another great advantage. It could not be stopped by any existing air
defense or any AICBM system which might be under development. Therefore, it would
place a new and highly complex problem on the shoulders of enemy defense
planners. In contrast, all new offensive system proposals which are pure ballistic
or semiballistic with lifting, maneuverable warheads would be vulnerable to any
successful anti-ICBM system.
Technically, the Pluto case is strong in support of the
cost/ effectiveness arguments. First and foremost, the project's
research-and-development record has been virtually spotless so far. Pluto has
not been plagued by failures and technical setbacks such as those which
hindered the nuclear-aircraft program and continue to hinder the nuclear-rocket
Compared to the other nuclear propulsion programs Pluto has
been a low-priority project with limited funding. Most of its effort has gone
toward reactor development. The primary objective has been to prove that it is
feasible to power a Mach 3 low-altitude vehicle with a nuclear ramjet. The
scientists and engineers at the AEC-University of California Lawrence Radiation
Laboratory and their principal contractors, Ling-Temco-Vought and Marquardt
Corporation, have exceeded this original objective. Their Tory II-C reactor
design has been proven in full power tests at the Nevada Test Station at
Jackass Flats. Its detail design has stood up to the rigors of a
1,060-degrees-Fahrenheit, 50,400-pound-per-square-foot airstream, the same as
would pass through the reactor during Mach 3 flight.
As a flight-weight reactor the Tory II-C has several
features which distinguish it from stationary power reactors on the ground, or
reactors used in submarines, aircraft carriers, or merchant ships. Most
important is a very high power-to-weight ratio. Powerplants in high-performance
flight vehicles must deliver high power for minimum possible weight. Nuclear-powered
vehicles are no exception.
Power-to-weight ratios for nuclear powerplants are sensitive
information. But it is known that the nuclear turbojets in the nuclear-powered
airplane program were about fifty times better from the power-to-weight standpoint
than the engine system in the Nautilus, the first nuclear-powered submarine,
and about 200 times better than the atomic-powered merchantman, the NS
Savannah. The Pluto powerplant's power-to-weight ratio is many times superior
to any planned for the nuclear airplane. One major reason is the difference in
shielding weight. The airplane had to carry more than 100,000 pounds of
shielding to protect the crew. Pluto vehicles need only a "shadow"
shield (see page 33) weighing a few thousand pounds to stop radiation from
streaming directly from the reactor into the payload bay, the guidance system,
automatic pilot, cooling system, etc., all of which are thousands of times more
resistant to radiation than are humans.
Pluto also gets a weight advantage because it is a
throw-away unit. It is intended to operate for about twenty-four hours at the
most and then to be either incinerated in an enemy target or to be sent to the
bottom of the sea on command from base. There are no plans to bring a Pluto
vehicle back to a base, service it, and use it again. The requirements for a
long service life and ground maintenance added many thousands of pounds to the
Another weight advantage falls to Pluto because its reactor
wall temperatures must be around 2,200 degrees Fahrenheit or higher. This is at
least 500 degrees Fahrenheit hotter than the wall temperatures required in
nuclear turbojets powering a high subsonic-speed airplane.
The nuclear ramjet must operate at around Mach 3 to have
enough ram pressure to overcome the high pressure losses associated with
airflow through the reactor. At this speed the air enters the engine at 1,000
degrees Fahrenheit, and the reactor must be much hotter to produce the required
thrust. Thrust-to-weight ratio of the nuclear ramjet depends heavily upon the
maximum wall temperature achieved in the reactor. If it could be pushed up to
2,500 degrees Fahrenheit, then the payload percentage probably could go up to
more than fifty percent of the total vehicle weight.
The high temperature requirement meant that Pluto reactors
could not be made of the low melting point metals used in aircraft, shipboard,
and ground power reactors. And the ramjet reactor could not be made of
graphite, the nuclear rocket reactor material that operates to very high
temperatures in the 3,000-degreeFahrenheit range. Graphite and most other
high-temperature materials oxidize and deteriorate rapidly when exposed to hot
air. The nuclear environment also imposed severe requirements, and the
materials which conceivably could be used in the ramjet reactor were severely
Beryllium oxide, a ceramic, was virtually the only
candidate. It has two serious disadvantages, and a large percentage of Pluto
funds have gone toward overcoming them. First, beryllium oxide is extremely brittle.
Yet it has to withstand terrific thermal shock loads during reactor start-up,
and heavy gust loads and vibrations during Mach 3 flight at sea level in rough
air. The key technical accomplishments of the Pluto program have been to improve
the mechanical properties of beryllium oxide and to devise design techniques
which would hold the brittle reactor together for at least one trip around the
The second problem is that beryllium oxide releases fission
fragments, radioactive particles, into the airstream when the reactor is hot.
Reportedly, the rate of release has been reduced to the point that there would
be no hazard to persons on the ground because the particles would be released
over a very large area by a Mach 3 missile.
Successful use of beryllium oxide has resulted in a relative
light, high-power density reactor compared to any manned aircraft system. The
Tory TI-C reactor is only 4.7 feet in diameter and 8.5 feet long yet it
produces 600 million watts of power.
Much of the low cost, light weight and relatively high
payload percentage of the nuclear-ramjet vehicle can be attributed to the fact
that low-altitude, Mach 3, vehicles have no need for wings. Under these flight
conditions a body of approximately cylindrical shape has as high an aerodynamic
efficiency (lift-to-drag ratio) as the best winged aircraft. Usually the wings
count for ten to fifteen percent of the total weight of an aircraft. If they
are removed the payload can be increased
by this percentage. On Mach 3 vehicles there is the added bonus of reducing the
structural heating problems when the
wings are eliminated.
Pluto also has benefited from significant advances in
high-temperature airframe structures. Eight years ago there would have been
some legitimate doubts about building even a wingless airframe which would hold
together for twenty-four hours of rough sea-level flight under the combined
heating effects of a Mach 3 airstream and heavy nuclear radiation. Today, it is
considered within the state of the art to build the Pluto vehicle out of sheet
steel that formerly was available only to turbine wheel designers.
All subsystems needed in Pluto vehicles have been reported
in congressional testimony to be ready or well within the state of the art.
Some of them, such as the basic inertial-guidance system, have been developed
to a high state of perfection outside of the Pluto program. Others have been
studied intensely with project funds. One of these is an automatically
controlled air-inlet system with low reaction time, and a wide range of
allowable operating conditions which compensate for the low power response time
of the reactor. Another is a pneumatic actuator which sits on the front of the
reactor and controls its power output by moving hafnium control rods into and
out of the core. All the electronic components necessary for Pluto's
communication, navigation, and bombing system have been developed in the
project or in the nuclear airplane program.
Expert testimony before the Congress has indicated that
Pluto cannot make any more significant progress without flight tests. Studies
of military vehicles such as the SLAM (Supersonic Low Altitude Missile) and
LASV (Low Altitude Supersonic Vehicle) also are at the point of bogging down
without more definite data from Pluto flight tests.
Most congressmen familiar with the program are highly
critical of the Administration because no formal requirement has been generated
in the Department of Defense. Undoubtedly, the House Appropriations Committee
will have substantial support in its move to cut off Pluto funds unless a
requirement is generated.
Rep. Melvin Price (D.-Ill.) reflected the general tenor of
the Congress when he recently discussed the point. He said. "...
consistently, the Department of Defense and the Air Force have stated that one
of their main requirements is a low-altitude, supersonic aircraft manned or
unmanned. ... They have stated this year after year. They still state it. They
stated it again in the military posture hearings this year.
So they do have a requirement for it. Whether they state it
as a requirement officially or not, they certainly have stated it many times in
presentations before the Armed Services Committee of both Houses of
In backing the Pluto development for several years
Representative Price and most of his colleagues believed they were meeting a
military requirement. Now that there is considerable doubt about this point
they apparently are going to push for clarification of the military
requirements that actually exist today and of DOD policies used to establish
requirements. Until such clarification Project Pluto seems destined for cold
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