From the Lab to the Battlefield ? Nanotechnology and Fourth-Generation
Nuclear Weapons
By André Gsponer
Introduction
In Disarmament Diplomacy No. 65, Sean Howard warned of the dangers of
enhanced or even new types of weapons of mass destruction (WMD)
emerging from the development of 'nanotechnology', an umbrella term
for a range of potentially revolutionary engineering techniques at the
atomic and molecular level.1 Howard called for urgent preliminary
consideration to be given to the benefits and practicalities of
negotiating an 'Inner Space Treaty' to guard against such
developments. While echoing this call, this paper draws attention to
the existing potential of nanotechnology to affect dangerous and
destabilising 'refinements' to existing nuclear weapon designs.
Historically, nanotechnology is a child of the nuclear weapons labs, a
creation of the WMD-industrial complex. The most far-reaching and
fateful impacts of nanotechnology, therefore, may lie - and can
already be seen - in the same area.
The Strategic Context
Two important strategic lessons were taught by the last three wars in
which the full extent of Western military superiority was displayed:
Iraq, Yugoslavia, and Afghanistan. First, the amount of conventional
explosive that could be delivered by precision-guided munitions like
cruise missiles was ridiculous in comparison to their cost: some
targets could only be destroyed by the expenditure of numerous
delivery systems while a single one loaded with a more powerful
warhead would have been sufficient.2 Second, the use of weapons
producing a low level of radioactivity appears to be acceptable, both
from a military point of view because such a level does not impair
further military action, and from a political standpoint because most
political leaders, and shapers of public opinion, did not object to
the battlefield use of depleted uranium.3
These lessons imply a probable military perception of the need for new
conventional or nuclear warheads, and a probable political acceptance
of such warheads if they do not produce large amounts of residual
radioactivity. Moreover, during and after these wars, it was often
suggested that some new earth-penetrating weapon was needed to destroy
deeply buried command posts, or facilities related to weapons of mass
destruction.4
It is not, therefore, surprising to witness the emergence of a
well-funded scientific effort apt to create the technological basis
for making powerful new weapons - an effort that is not sold to the
public opinion and political leaders as one of maintaining a high
level of military superiority, but rather as one of extending human
enterprise to the next frontier: the inner space of matter to be
conquered by the science of nanotechnology.
The Military Impact of Nanotechnology
Nanotechnology, i.e., the science of designing microscopic structures
in which the materials and their relations are machined and controlled
atom-by-atom, holds the promise of numerous applications. Lying at the
crossroads of engineering, physics, chemistry, and biology,
nanotechnology may have considerable impact in all areas of science
and technology. However, it is certain that the most significant near
term applications of nanotechnology will be in the military domain. In
fact, it is under the names of 'micromechanical engineering' and
'microelectromechanical systems' (MEMS) that the field of
nanotechnology was born a few decades ago - in nuclear weapons
laboratories.
A primary impetus for creating these systems was the need for
extremely rugged and safe arming and triggering mechanisms for nuclear
weapons such as atomic artillery shells. In such warheads, the nuclear
explosive and its trigger undergo extreme acceleration (10,000 times
greater than gravity when the munition is delivered by a heavy gun). A
general design technique is then to make the trigger's crucial
components as small as possible.5 For similar reasons of extreme
safety, reliability, and resistance to external factors, the
detonators and the various locking mechanisms of nuclear weapons were
increasingly designed as more and more sophisticated
microelectromechanical systems. Consequently, nuclear weapons
laboratories such as the Sandia National Laboratory in the US are
leading the world in translating the most advanced concepts of MEMS
engineering into practice.6
A second historical impetus for MEMS and nanotechnology, one which is
also over thirty years old, is the still ongoing drive towards
miniaturisation of nuclear weapons and the related quest for very-low
yield nuclear explosives which could also be used as a source of
nuclear energy in the form of controlled microexplosions. Such
explosions (with yields in the range of a few kilograms to a few tons
of high-explosive equivalent) would in principle be contained - but
they could just as well be used in weapons if suitable compact
triggers are developed. In this line of research, it was soon
discovered that it is easier to design a micro-fusion than a
micro-fission explosive (which has the further advantage of producing
much less radioactive fallout than a micro-fission device of the same
yield). Since that time, enormous progress has been made, and the
research on these micro-fusion bombs has now become the main advanced
weapons research activity of the nuclear weapons laboratories, using
gigantic tools such as the US National Ignition Facility (NIF) and
France's Laser Mégajoule. The tiny pellets used in these experiments,
containing the thermonuclear fuel to be exploded, are certainly the
most delicate and sophisticated nano-engineered devices in existence.
A third major impetus for nanotechnology is the growing demand for
better materials (and parts made of them) with extremely well
characterised specifications. These can be new materials such as
improved insulators which will increase the storage capacity of
capacitors used in detonators, nano- engineered high-explosives for
advanced weaponry, etc. But they can also be conventional materials of
extreme purity, or nano-engineered components of extreme precision.
For instance, to meet NIF specifications, the 2-mm-diameter fuel
pellets must not be more than 1 micrometer out of round; that is, the
radius to the outer surface can vary by no more than 1 micrometer (out
of 1,000) as one moves across the surface. Moreover, the walls of
these pellets consist of layers whose thicknesses are measured in
fractions of micrometers, and surface- smoothnesses in tens of
nanometers; thus, these specifications can be given in units of 1,000
or 100 atoms, so that even minute defects have to be absent for the
pellets to implode symmetrically when illuminated by the lasers.
The final major impetus for MEMS and nanotechnology, which has the
greatest overlap with non-military needs, is their promise of new
high-performance sensors, transducers, actuators, and electronic
components. The development of this field of applications is expected
to replicate that of the micro-electronic industry, which was also
originally driven by military needs, and which provides the reference
for forecasting a nano-industrial boom and a financial bonanza. There
are, however, two major differences. First, electronic devices which
can be manufactured in large quantities and at low cost are
essentially planar, while MEMS are three-dimensional devices which may
include moving parts. Second, the need for MEMS outside professional
circles (medical, scientific, police, military) is quite limited, so
that the market might not be as wide as expected. For example, the
detection and identification of chemical or biological weapon threats
through specificity of molecular response may lead to all sorts of
medical applications, but only to few consumer goods.
Near and Long-Term Applications and Implications of Nanotechnology
Considering that nanotechnology is already an integral part of the
development of modern weapons, it is important to realise that its
immediate potential to improve existing weapons (either conventional
or nuclear), and its short-term potential to create new weapons
(either conventional or nuclear), are more than sufficient to require
the immediate attention of diplomats and arms controllers.
In this perspective, the potential long-term applications of
nanotechnology (and their foreseeable social and political
implications) should neither be downplayed nor overemphasised. Indeed,
there are potential applications such as self- replicating nano-robots
('nanobots') which may never prove to be feasible because of
fundamental physical or technical obstacles.7 But this impossibility
would not mean that the somewhat larger micro-robots of the type that
are seriously considered in military laboratories could never become a
reality.8
In light of these extant and potential dangers and risks, every effort
should be made not to repeat the error of the arms-control community
with regard to missile defence. For over thirty years, that community
acted on the premise that a ballistic missile defense system will
never be built because it will never be sufficiently effective - only
to be faced with a concerted attempt to construct such a system! If
some treaty is contemplated in order to control or prohibit the
development of nanotechnology, it should be drafted in such a way that
all reasonable long-term applications are covered.
Moreover, it should not be forgotten that while nanotechnology mostly
emphasises the spatial extension of matter at the scale of the
nanometer (the size of a few atoms), the time dimension of mechanical
engineering has recently reached its ultimate limit at the scale of
the femtosecond (the time taken by an electron to circle an atom). It
has thus become possible to generate bursts of energy in suitably
packaged pulses in space and time that have critical applications in
nanotechnology, and to focus pulses of particle or laser beams with
extremely short durations on a few micrometer down to a few nanometer
sized targets. The invention of the 'superlaser', which enabled such a
feat and provided a factor of one million increase in the
instantaneous power of tabletop lasers, is possibly the most
significant recent advance in military technology. This increase is of
the same magnitude as the factor of one million difference in energy
density between chemical and nuclear energy.9
In the present paper, the long-term impact of nanotechnology will not
be further discussed. The objective is to emphasise the near- to
mid-term applications to existing and new types of nuclear weapons.
Nanotechnological Improvement of Existing Types of Nuclear Weapons
Nuclear weapon technology is characterised by two sharply contrasting
demands. On the one hand, the nuclear package containing the fission
and fusion materials is relatively simple and forgiving, i.e. rather
more sophisticated than complicated. On the other hand, the many
ancillary components required for arming the weapon, triggering the
high-explosives, and initiating the neutron chain-reaction, are much
more complicated. Moreover, the problems related to maintaining
political control over the use of nuclear weapons, i.e. the operation
of permissive action links (PALs), necessitated the development of
protection systems that are meant to remain active all the way to the
target, meaning that all these ancillary components and systems are
submitted to very stringent requirements for security, safety, and
reliable performance under severe conditions.
The general solution to these problems is to favour the use of hybrid
combinations of mechanical and electronic systems, which have the
advantage of dramatically reducing the probability of common mode
failures and decreasing sensitivity to external factors. It is this
search for the maximisation of reliability and ruggedness which is
driving the development and application of nanotechnology and MEMS
engineering in nuclear weapons science.
To give an important example: modern nuclear weapons use insensitive
high- explosives (IHE) which can only be detonated by means of a small
charge of sensitive high-explosive that is held out of alignment from
the main charge of IHE. Only once the warhead is armed does a MEMS
bring the detonator into position with the main charge. Since the
insensitive high-explosive in a nuclear weapon is usually broken down
into many separate parts that are triggered by individual detonators,
the use of MEMS-based detonators incorporating individual locking
mechanisms are an important ingredient ensuring the use- control and
one-point safety of such weapons.10
Further improvements on existing nuclear weapons are stemming from the
application of nanotechnology to materials engineering. New
capacitors, new radiation-resistant integrated circuits, new composite
materials capable to withstand high temperatures and accelerations,
etc., will enable a further level of miniaturisation and a
corresponding enhancement of safety and usability of nuclear weapons.
Consequently, the military utility and the possibility of forward
deployment, as well as the potentiality for new missions, will be
increased.
Consider the concept of a "low-yield" earth penetrating warhead. The
military appeal of such a weapon derives from the inherent difficulty
of destroying underground targets. Only about 15 % of the energy from
a surface explosion is coupled (transferred) into the ground, while
shock waves are quickly attenuated when travelling through the ground.
Even a few megatons surface burst will not be able to destroy a buried
target at a depth or distance more than 100-200 meters away from
ground zero. A radical alternative, therefore, is to design a warhead
which would detonate after penetrating the ground by a few tens of
meters or more. Since a free-falling or rocket-driven missile will not
penetrate the surface by more than about ten meters, some kind of
active penetration mechanism is required. This implies that the
nuclear package and its ancillary components will have to survive
extreme conditions of stress until the warhead is detonated.
Fourth-Generation Nuclear Weapons
First- and second-generation nuclear weapons are atomic and hydrogen
bombs developed during the 1940s and 1950s, while third-generation
weapons comprise a number of concepts developed between the 1960s and
1980s, e.g. the neutron bomb, which never found a permanent place in
the military arsenals. Fourth-generation nuclear weapons are new types
of nuclear explosives that can be developed in full compliance with
the Comprehensive Test Ban Treaty (CTBT) using inertial confinement
fusion (ICF) facilities such as the NIF in the US, and other advanced
technologies which are under active development in all the major
nuclear-weapon states - and in major industrial powers such as Germany
and Japan.11
In a nutshell, the defining technical characteristic of
fourth-generation nuclear weapons is the triggering - by some advanced
technology such as a superlaser, magnetic compression, antimatter,
etc. - of a relatively small thermonuclear explosion in which a
deuterium-tritium mixture is burnt in a device whose weight and size
are not much larger than a few kilograms and litres. Since the yield
of these warheads could go from a fraction of a ton to many tens of
tons of high- explosive equivalent, their delivery by precision-guided
munitions or other means will dramatically increase the fire-power of
those who possess them - without crossing the threshold of using
kiloton-to-megaton nuclear weapons, and therefore without breaking the
taboo against the first-use of weapons of mass destruction. Moreover,
since these new weapons will use no (or very little) fissionable
materials, they will produce virtually no radioactive fallout. Their
proponents will define them as "clean" nuclear weapons - and possibly
draw a parallel between their battlefield use and the consequences of
the expenditure of depleted uranium ammunition.12
In practice, since the controlled release of thermonuclear energy in
the form of laboratory scale explosions (i.e., equivalent to a few
kilograms of high- explosives) at ICF facilities like NIF is likely to
succeed in the next 10 to 15 years, the main arms control question is
how to prevent this know-how being used to manufacture
fourth-generation nuclear weapons. As we have already seen,
nanotechnology and micromechanical engineering are integral parts of
ICF pellet construction. But this is also the case with ICF drivers
and diagnostic devices, and even more so with all the hardware that
will have to be miniaturised and 'ruggedised' to the extreme in order
to produce a compact, robust, and cost-effective weapon.
A thorough discussion of the potential of nanotechnology and
microelectromechanical engineering in relation to the emergence of
fourth- generation nuclear weapons is therefore of the utmost
importance. It is likely that this discussion will be difficult, not
just because of secrecy and other restrictions, but mainly because the
military usefulness and usability of these weapons is likely to remain
very high as long as precision-guided delivery systems dominate the
battlefield. It is therefore important to realise that the
technological hurdles that have to be overcome in order for laboratory
scale thermonuclear explosions to be turned into weapons may be the
only remaining significant barrier against the introduction and
proliferation of fourth-generation nuclear weapons. For this reason
alone - and there are many others, beyond the scope of this paper -
very serious consideration should be given to the possibility of
promoting an 'Inner Space Treaty' to prohibit the military development
and application of nanotechnological devices and techniques.
Notes and References
1. Sean Howard, 'Nanotechnology and Mass Destruction: the Need for an
Inner Space Treaty', Disarmament Diplomacy No. 65 (July/August 2002),
pp. 3-16.
2. The decades-long "change from the importance of the big bang to the
importance of accuracy" was emphasised by Edward Teller in a paper
written shortly after the 1991 Gulf War: "Shall one combine the newly
acquired accuracy with smaller nuclear weapons (perhaps even of yields
of a few tons) to be used against modern weapons such as tanks and
submarines?" Edward Teller, American Journal of Physics, Vol.59,
October 1991, p.873.
3. Depleted uranium (DU) munitions were primarily designed to stop a
massive tank attack by the nuclear-armed Warsaw Pact Organisation.
Their first use during the 1991 Gulf War broke a 46-year long taboo
against the intentional use or induction of radioactivity in combat.
4. Most literature related to earth-penetrating weapons refers to
devices with a yield in the low kiloton range. However, some experts
have argued that much less powerful devices would suffice: "A
small-yield nuclear weapon (15 tons or less) would be militarily
useful: it could destroy deeply buried targets that otherwise could be
readily reparable, and it would do so without placing US forces at
greater risk. It would also be politically useful, serving notice to
the proliferant that the United States will engage it and, if
necessary, escalate the conflict." Kathleen C. Bailey, 'Proliferation:
Implications for US Deterrence', in Kathleen C. Bailey, ed., Weapons
of Mass Destruction: Costs Versus Benefits, Manohar, New Delhi, 1994,
pp. 141-142.
5. The smaller an electro-mechanical system, the higher its resistance
to acceleration. This explains why it is possible to design a
shock-proof wrist- watch, while a wall-clock falling on the ground is
certain to be damaged.
6. Pictures of the 50-micrometer gears of Sandia's intricate safety
lock for nuclear missiles were published in Science, Vol.282, October
16, 1998, pp. 402-405.
7. Richard E. Smalley, 'Of chemistry, love and nanobots', Scientific
American, Vol.285, September 2001, pp. 68-69.
8. Keith W. Brendley and Randall Steeb, 'Military applications of
microelectromechanical systems', Report MR-175-OSD/AF/A, RAND
Corporation, 1993, 57 pp. Johndale C. Solem, 'On the mobility of
military microrobots', Report LA-12133, Los Alamos National
Laboratory, July 1991, 17 pp.
9. Using the language of Endnote No. 7, one can say that photons
(i.e., particles of light) are, contrary to atoms, neither "fat" nor
"sticky": they can be concentrated in unlimited numbers so that a very
localised and brief light pulse can contain huge amounts of energy -
so large that a table-top superlaser can initiate nuclear reactions
such as fission or fusion.
10. As routinely defined by the US Department of Defense: "A nuclear
weapon is one-point safe if, when the high explosive (HE) is initiated
and detonated at any single point, the probability of producing a
nuclear yield exceeding four pounds of trinitrotoluene (TNT)
equivalent is less than one in a million." See, for example,
http://www.dtic.mil/whs/directives/corres/pdf/3150m_1296/p31502m.pdf
11. André Gsponer
and Jean-Pierre Hurni, The Physical Principles of
Thermonuclear Explosives, Inertial Confinement Fusion, and the Quest
for Fourth Generation Nuclear Weapons, INESAP Technical Report No.1,
Presented at the 1997 INESAP Conference, Shanghai, China, 8-10
September 1997, Seventh edition, September 2000, ISBN: 3-9333071-02-X,
195 pp.
12. André Gsponer,
Jean-Pierre Hurni, and Bruno Vitale, 'A comparison
of delayed radiobiological effects of depleted-uranium munitions
versus fourth- generation nuclear weapons', Report ISRI-02-07, due to
appear in the Proceedings of the 4th Int. Conf. of the Yugoslav
Nuclear Society, Belgrade, Sep.30 - Oct.4, 2002, 14 pp. Available at
http://arXiv.org/abs/ physics/0210071
Dr. André Gsponer
is Director of the Geneva-based Independent
Scientific Research Institute (ISRI), founded in 1982 to study the
arms- control/disarmament implications of emerging technologies. The
author thanks his colleagues at ISRI for their research and comments
related to this paper.