A document discusses the effects of nuclear weapons in space, including their effects on personnel and potential communication effects. It finds that in space, without an atmosphere to absorb radiation, nuclear radiation would be the dominant effect over long ranges, with lethal doses reaching hundreds of miles for multi-megaton weapons. High-frequency radio communications were also disrupted for hours by nuclear tests in 1958, demonstrating potential communication impacts. While shielding could protect manned vehicles, unmanned spacecraft would be less vulnerable to nuclear defenses in potential future space warfare.

1. PROJECT SPACE LASER AWEAPONS
CONCEPT BY ZEDRICK KHAN

Nukes In Space

2. 
As you should know, there are two types of nuclear weapons. An "atomic bomb" is a weapon
with a war-head powered by nuclear fission. An "H-bomb" or "hydrogen bomb" is a weapon
with more powerful warhead powered by nuclear fusion. In some military documents they will
refer to the nuclear warhead as the "physics package."
You can read all about the (unclassified) details of their internal construction and
mechanism here.
Occasionally you will find a fusion weapon referred to as a "Solar-Phoenix" or a "Bethe-
cycle" weapon. This is a reference to the nuclear scientist Hans Bethe and the Bethe-Weizsäcker
or carbon-nitrogen cycle which powers the fusion reaction in the heart of stars heavier than Sol.
SECTION 9: OTHER WEAPONS
Lasers and kinetics are standard reference weapons, and for good reason. All other
proposed weapons suffer from serious problems which render them ineffective
compared to lasers and kinetics.
The most common alternative weapons described for space warfare are nuclear in
nature. There are several myths about nuclear weapon use in space, the most common
of which is that they are ineffective if not in contact with the target. The logic behind this
theory is that in the atmosphere, most of the damage comes from the shockwave, which
obviously cannot propagate in space. An alternative is that the damage will be inflicted

3. by the plasma that used to be the device casing. The flaw is that the shockwave is not
a property of the device itself, but instead results from the absorption by the air of the X-
rays emitted by the device. The superheated air then expands and produces the
shockwave. In space, the X-rays are not absorbed and instead go on to damage the
target directly. They still obey the inverse square law, and are not likely to be effective
against mass objects such as spacecraft beyond a few kilometers, depending on the
yield of the device. This makes them essentially point-attack weapons, given the scale
at which spacecraft maneuver.
However, there is another mechanism by which nuclear weapons do damage in space,
namely radiation poisoning of the crew. Even a 1 kT nuclear weapon will inflict a lethal
dose of radiation on an unprotected human out to about 20 km, depending on the type
of weapon. Larger weapons will have greater lethal ranges, scaled with the square root
of weapon yield. It is possible to armor against this radiation, reducing the lethal range
by an order of magnitude or more. All spacecraft will have some radiation shielding
because of the environment they operate in, although neutron radiation (probably the
biggest killer) generally does not occur in nature. Civilian ships are thus likely to be far
more vulnerable than military ones to nuclear weapons killing their crews, unless they
themselves are nuclear-powered and manage to face their shadow shield towards the
initiation.
It has been suggested that the great lethality of the radiation against the crew is likely to
make enhanced-radiation weapons (commonly known as neutron bombs) the nuclear
weapons of choice in space. This might well be the case, particularly as soft X-rays
(such as might be produced by nuclear weapons) are significantly easier to shield
against than the neutrons emitted by nuclear weapons, particularly the fusion neutrons
produced by an enhanced-radiation weapon. The vulnerability of the crew to nuclear
weapons is another factor that would make drones attractive, as electronics are easier
to harden and generally more resistant to radiation.
The biggest disadvantages of nuclear weapons are their size and short range. Even the
smallest of modern nuclear weapons are considerably larger than the SCODs described
above, which makes them easy to detect and target, given that their destruction would
logically take priority over that of more typical kinetics. At the same time, the nuclear
weapon has to get to within a few kilometers, virtually touching the target. Given typical
closing velocities, a fraction of a second is not going to significantly improve survivability
vis a vis a typical kinetic. And a kinetic of the same size as the nuclear weapon (100 kg
or more) is almost as lethal against a typical target. This ignores the questions of cost,
which is almost certainly far higher for a nuclear weapon then an equal mass of kinetics,
and of politics. Many people go into a frenzy whenever they hear the word ‘nuclear’,
and would likely oppose the deployment of such weapons. Pushing said deployment
through would require political and fiscal capital that might be better spent on
conventional weapons.
Possibly the best use of nuclear weapons is in a defensive role. A typical kinetic will be
quite vulnerable to surface and sensor damage, not to mention the relative lack of

4. defenses against kinetics. Even then, squeamishness about nuclear weapons might
well prevent their use.
The use of the X-rays from the device to pump a laser is also a common suggestion,
most notably used in David Weber’s “Honor Harrington” series. The same drawbacks
that apply to conventional nuclear weapons apply to these devices, though to a lesser
extent. Much of the information regarding this concept is classified, which has led to
conflicting views of its effectiveness. Depending on the source, the effective range is
between 100 km and several thousand kilometers. Particularly at the lower end of this
range, the utility is questionable. The device gains a few seconds of standoff, but still
has the other disadvantages of conventional nuclear weapons. At longer ranges,
particularly with low-end defenses, the idea becomes feasible.
There are two possible drawbacks to the use of nuclear weapons in orbit. The first is
the well-known High-Altitude ElectroMagnetic Pulse (HEMP) generated when a nuclear
weapon is detonated in the upper atmosphere. This results from the interaction
between the products of the bomb, and both the Earth’s atmosphere and the Earth’s
magnetic field. In deep space, neither would exist, removing the HEMP. HEMP is
relatively easy to protect against, adding between 5 and 10% to the price of military
electronic gear. High-quality civilian surge protectors are also adequate shielding,
though low-quality models have problems dealing with the rate at which the pulse
occurs. Any spacecraft will almost by definition be hardened against such effects. That
said, the effect does exist, and would be a consequence of orbital nuclear weapon use.
The second drawback is the lesser-known Argus Effect, in which charged particles are
trapped by the Earth’s magnetic field and form artificial radiation belts, damaging or
destroying satellites. These particles are mostly electrons, and tend to cluster between
1000 and 2000 km altitude. They pose a threat similar to a greatly-enhanced Van Allen
Belt, and would reduce the operational lives of satellites. There is a possibility that the
belts could be used as a defensive weapon, but establishing them would mean
sacrificing a large portion of one’s orbital (and quite possibly planetary) infrastructure. It
is also possible that an “Argus Blockade” could be implemented. This would be the
intentional creation of such an effect by an attacker, intended to impair the defender’s
space infrastructure and prevent him from rebuilding quickly. The effect persists for a
month or so before fading back to levels that are unlikely to impair space operations.
EMP weapons have occasionally been suggested for space use. These use some non-
nuclear method to generate an EMP, hopefully disabling the target’s electronics. The
generation of such a pulse requires a large amount of power, which can either be
generated by high explosives (most useful in a missile) or large capacitor banks, which
are far better suited for shipboard use. There are two major problems with this concept,
however, which will likely limit its use. The first is that any EMP will be generated using
microwaves or radio waves. As discussed in Section 7, diffraction is greater for beams
with longer wavelengths. This limits the range of any EMP weapon, which is hardly
desirable given the ranges at which space combat is likely to occur. The second is that
there are a number of natural effects encountered in spaceflight that are similar to

5. EMPs. Solar storms in particular can produce induced currents in much the same
manner, requiring spacecraft to be hardened against them. This hardening would also
be effective against EMPs, requiring massive amounts of power to have any chance of
working. The only really practical use for EMP weapons might be during hostile
boarding missions against civilians or disabled warships. A civilian ship is likely to be
somewhat less hardened then a military vessel, and the boarding ship can get very
close without getting shot to pieces by the target.
by Byron Coffey (2016)
Warhead



6. 
As far as warhead mass goes, Anthony Jackson says the theoretical limit on mass for a fusion
warhead is about 1 kilogram per megaton. No real-world system will come anywhere close to
that, The US W87 thermonuclear warhead has a density of about 500 kilograms per megaton.
Presumably a futuristic warhead would have a density between 500 and 1 kg/Mt. Calculating the
explosive yield of a weapon is a little tricky.
For missiles, consider the US Trident missile. Approximately a cylinder 13.41 m in length by
1.055 m in radius, which makes it about 47 cubic meters. Mass of 58,500 kg, giving it a density
of 1250 kg/m3. The mass includes eight warheads of approximately 160 kg each.
Wildly extrapolating far beyond the available data, one could naively divide the missile mass by
the number of warheads, and divide the result by the mass of an individual warhead. The bottom
line would be that a warhead of mass X kilograms would require a missile of mass 45 *
X kilograms, and a volume of 0.036 * X cubic meters (0.036 = 45 / 1250). Again futuristic
technology would reduce this somewhat.
Nuclear weapons will destroy a ship if they detonate exceedingly close to it. But if it is further
away than about a kilometer, it won't do much more than singe the paint job and blind a few
sensors. And in space a kilometer is pretty close range.
Please understand: I am NOT saying that nuclear warheads are ineffective. I am saying that the
amount of damage they inflict falls off very rapidly with increasing range. At least much more
rapidly than with the same sized warhead detonated in an atmosphere.
But if the nuke goes off one meter from your ship, your ship will probably be vaporized.
Atmosphere or no.

7. George William Herbert says a nuke going off on Terra has most of the x-ray
emission absorbed by the atmosphere, and transformed into the first fireball and the blast wave.
There ain't no atmosphere in space so the nuclear explosion is light on blast and heavy on x-rays.
In fact, almost 90% of the bomb energy will appear as x-rays behaving as if they are from a point
source (specifically 80% soft X-rays and 10% gamma), and subject to the good old inverse
square law (i.e., the intensity will fall off very quickly with range). The remaining 10% will be
neutrons.
The fireball and blast wave is why nuclear warheads detonating in the atmosphere will flatten
buildings for tens of kilometers, but detonations in space have a damage range under one
kilometer.
For an enhanced radiation weapon (AKA "Neutron Bomb") figures are harder to come by. The
best guess figure I've managed to find was up to a maximum of 80% neutrons and 20% x-rays.
If you want to get more bang for your buck, there is a possibility of making nuclear shaped
charges. Instead of wasting their blast on a spherical surface, it can be directed at the target
spacecraft. This will reduce the surface area of the blast, thus increasing the value for kiloJoules
per square meter.
According to John Schilling, with current technology, the smallest nuclear warhead would
probably be under a kiloton, and mass about twenty kilograms. A one-megaton warhead would
be about a metric ton, though that could be reduced by about half with advanced technology.
Eric Rozier has an on-line calculator for nuclear weapons. Eric Henry has a spreadsheet that does
nuclear blast calculations, including shaped charges, on his website. For bomb blasts on the
surface of the Earth or other planet with an atmosphere, you can use the handy-dandy Nuclear
Bomb Effects Computer. But if you really want to do it in 1950's Atomic Rocket Retro style,
make your own do-it-yourself Nuclear Bomb Slide Rule!
NUCLEAR WEAPON EFFECTS IN SPACE
A. NUCLEAR WEAPON EFFECTS ON PERSONNEL
In addition to the natural radiation dangers which will confront the space traveler, we
must also consider manmade perils which may exist during time of war. In particular,
the use of nuclear weapons may pose a serious problem to manned military space
operations. The singular emergence of man as the most vulnerable component of a
space-weapon system becomes dramatically apparent when nuclear weapon effects in
space are contrasted with the effects which occur within the Earth's atmosphere.
When a nuclear weapon is detonated close to the Earth's surface the density of the
air is sufficient to attenuate nuclear radiation (neutrons and gamma rays) to such a
degree that the effects of these radiations are generally less important than the effects

8. of blast and thermal radiation. The relative magnitudes of blast, thermal and nuclear
radiation effects are shown in figure 1 for a nominal fission weapon (20 kilotons) at sea
level.1
The solid portions of the three curves correspond to significant levels of blast,
thermal, and nuclear radiation intensities. Blast overpressures of the order of 4 to 10
pounds per square inch will destroy most structures. Thermal intensities of the order of
4 to 10 calories per square centimeter will produce severe burns to exposed persons.
Nuclear radiation dosages in the range 500 to 5,000 roentgens are required to produce
death or quick incapacitation in humans.
1 The Effect of Nuclear Weapons, U. S. Department of Defense, published by the
Atomic Energy Commission, June 1957.
132 ASTRONAUTICS AND ITS APPLICATIONS

Fig. 1 - Weapon effects at surface (20 KT)

9. If a nuclear weapon is exploded in a vacuum-i. e., in space-the complexion of
weapon effects changes drastically:
First, in the absence of an atmosphere, blast disappears completely.
Second, thermal radiation, as usually defined, also disappears. There is no longer
any air for the blast wave to heat and much higher frequency radiation (x-rays and
gamma rays) is emitted from the weapon itself.
ASTRONAUTICS AND ITS APPLICATIONS 133
Third, in the absence of the atmosphere, nuclear radiation will suffer no physical
attenuation and the only degradation in intensity will arise from reduction with distance.
As a result the range of significant dosages will be many times greater than is the case
at sea level.
Figure 2 shows the dosage-distance relationship for a 20-kiloton explosion when the
burst takes place at sea level and when the burst takes place in space. We see that in
the range 500 to 5,000 roentgens the space radii are of the order of 8 to 17 times as
large as the sea-level radii. At lower dosages the difference between the two cases
becomes even larger.

10. 
Fig. 2 - Nuclear radiation intensities (20 KT)
134 ASTRONAUTICS AND ITS APPLICATIONS
A yield of 20 kilotons has been used here as an example to show the dominance of
nuclear radiation effects in space; however, it may well be that multimegaton warheads,
rather than 20-kiloton warheads, will be far more representative of space defense
applications. With such weapons the lethal radii (from nuclear radiation) in space may
be of the order of hundreds of miles. The meaning of such huge lethal radii in possible
future space warfare cannot now be assessed. It does seem clear, however, that
manned space combat vehicles, unless heavy shielding is feasible, will be considerably
more vulnerable to nuclear defense weapons than their unmanned counterparts.
B. POSSIBLE COMMUNICATION EFFECTS
On August 1 and 12, 1958, nuclear warheads were detonated in missiles over
Johnston Island in the Pacific.2-3 These detonations were accompanied by impressive
visual displays seen over wide areas, leading observers to the opinion that the

11. detonations took place at very high altitudes.4-7 These displays were even seen on
Samoa, some 2,000 miles from Johnston Island.
The visual displays were accompanied by disruptive effects on radio
communications. Specifically, most commercial communication systems operating on
the high-frequency (about 5 to 25 megacycles) bands in the Pacific noted substantial
disturbances. Most links within a few hundred miles of Johnston Island experienced
"outages" for as long as several hours, at various times over a period of about a day. In
general, the effects on high-frequency communication links appear to have been quite
similar to the effects produced by giant solar flares.
2 Note to Editors and Correspondents, U. S. Atomic Energy Commission, Department
of Defense, Joint Office of Test Information, August 1, 1958
3 Note to Editors and Correspondents, U. S. Atomic Energy Commission, Department
of Defense, Joint Office of Test Information, August 12, 1958.
4 Atomic-Like Flash Seen Here-Nuclear Rocket Test Indicated, The Honolulu
Advertiser, August 1, 1958.
5 Samoa Bulletin, August 1, 1958.
6 Samoa Bulletin August 15. 1958.
7 Cullington, A Man-Made or Artificial Aurora, Nature, vol. 182, No. 4646, November 15,
1958, p. 1365.
From NUCLEAR WEAPON EFFECTS IN SPACE
KILOTONS PER KILOGRAM
(ed note: this is a historical look at the kiloton per kilogram alphas of actual nuclear
weapons. Also see his interactive Yield To Weight explorer)
What makes nuclear weapons impressive and terrible is that their default yield-to-weight
ratio — that is, the amount of bang per mass, usually expressed in terms of kilotons
per kilogram (kt/kg) — is much, much higher than conventional explosives. Take TNT
for example. A ton of TNT weighs, well, a ton. By definition. So that’s 0.001 kilotons per
1,000 kilograms; or 0.000001 kt/kg. By comparison, even a crude weapon like the Little
Boy bomb that was dropped on Hiroshima was about 15 kilotons in a 4,400 kg package:
0.003 kt/kg. That means that the Little Boy bomb had an energy density three orders of
magnitude higher than a regular TNT bomb would. Now, TNT isn’t the be-all and end-all
of conventional explosives, but no conventional explosive gets that much boom for its
buck compared to a nuke.
The Little Boy yield is much lower than the hypothetical energy density of uranium-235.
For every kilogram of uranium-235 that completely fissions, it releases about 17 kt/kg.
That means that less than a kilogram of uranium-235 fissioned in the Little Boy bomb to
release its 15 kilotons of energy. Knowing that there was 64 kg of uranium in the bomb,
that means that something like 1.3% of the uranium in the weapon actually underwent

12. fission. So right off the bat, one could intuit that this is something that could
probably be improved upon.
The Fat Man bomb had a much better use of fissile material than Little Boy. Its yield
wasn’t that much better (around 20 kilotons), but it managed to squeeze that (literally)
out of only 6.2 kilograms of plutonium-239. Pu-239 releases around 19 kilotons per
kilogram that completely fissions, so that means that around 15% of the Fat Man core (a
little under 1 kg of plutonium) underwent fission. But the bomb itself still weighed 4,700
kg, making its yield-to-weight ratio a mere 0.004 kt/kg. Why, despite the improve
efficiency and more advanced design of Fat Man, was the yield ratio almost
identical to Little Boy? Because in order to get that 1 kg of fissioning, it required
a very heavy apparatus. The explosive lenses weighed something like 2,400 kilograms
just by themselves. The depleted uranium tamper that held the core together and
reflected neutrons added another 120 kilograms. The aluminum sphere that held the
whole apparatus together weighed 520 kilograms. The ballistic case (a necessary thing
for any actual weapon!) weighed another 1,400 kg or so. All of these things were
necessary to make the bomb either work, or be a droppable bomb.
So it’s unsurprising to learn that improving yield-to-weight ratios was a high order of
business in the postwar nuclear program. Thermonuclear fusion ups the ante quite a bit.
Lithium-deuteride (LiD), the most common and usable fusion fuel, yields 50 kilotons for
every kilogram that undergoes fusion — so fusion is nearly 3 times more energetic per
weight than fission. So the more fusion you add to a weapon, the better the yield-
to-weight ratio, excepting for the fact that all fusion weapons require a fission
primary and usually also have very heavy tampers.
I took all of the reported American nuclear weapon weights and yields from Carey
Sublette’s always-useful website, put them into the statistical analysis program R, and
created this semi-crazy-looking graph of American yield-to-weight ratios:

13. 
Click for larger image
Online interactive version here
The horizontal (x) axis is the yield in kilotons (on a logarithmic scale), the vertical (y)
axis is the weight in kilograms (also on a log scale). In choosing which of the weights
and yields to use, I’ve always picked the lowest listed weights and the highest listed
yields — because I’m interested in the optimal state of the art. The individual scatter
points represent models of weapons. The size of each point represents how many of
them were produced; the color of them represents when they were first deployed. Those
with crosses over them are still in the stockpile. The diagonal lines indicate specific
yield-to-weight ratio regions.
A few points of interest here. You can see Little Boy (Mk-1), Fat Man (Mk-3), and the
postwar Fat Man improvements (Mk-4 — same weight, bigger yield) at the upper left,
between 0.01 kt/kg and 0.001 kt/kg. This is a nice benchmark for fairly inefficient fission
weapons. At upper right, you can see the cluster of the first H-bomb designs (TX-16,
EC-17, Mk-17, EC-24, Mk-24) — high yield (hence far to the right), but very heavy

14. (hence very high). Again, a good benchmark for first generation high-yield
thermonuclear weapons.
What a chart like this lets you do, then, is start to think in a really visual and
somewhat quantitative way about the sophistication of late nuclear weapon
designs. You can see quite readily, for example, that radical reductions in weight, like
the sort required to make small tactical nuclear weapons, generally results in a real
decrease in efficiency. Those are the weapons in the lower left corner, pretty much the
only weapons in the Little Boy/Fat Man efficiency range (or worse). One can also see
that there are a few general trends in design development over time if one looks at how
the colors trend.
First there is a movement down and to the right (less weight, more yield — improved
fission bombs); there is also a movement sharply up and to the right (high weight, very
high yield — thermonuclear weapons) which then moves down and to the left again
(high yield, lower weight — improved thermonuclear weapons). There is also the
splinter of low-weight, low-yield tactical weapons as well that jots off to the lower left. In
the middle-right is what appears to be a sophisticated “sweet spot,” the place where all
US weapons currently in the stockpile end up, in the 0.1-3 kt/kg range, especially the 2-
3 kt/kg range:

15. 
Click for larger image
These are the bombs like the W-76 or the B-61 — bombs with “medium” yield warheads
(100s rather than 1,000s of kilotons) in relatively low weight packages (100s rather than
1000s of kilograms). These are the weapons take advantage of the fact that they are
expected to be relatively accurate (and thus don’t need to be in the multi-megaton range
to have strategic implications), along with what are apparently sophisticated
thermonuclear design tricks (like spherical secondaries) to squeeze a lot of energy out
of what is a relatively small amount of material. Take the W-76 for example: its
manages to get 100 kilotons of yield out of 164 kilograms. If we assume that it is a
50/50 fission to fusion ratio, that means that it manages to fully fission about 5 kilograms
of fissionable material, and to fully fuse about 2 kilograms of fusionable material. And it
takes just 157 kg of other apparatus (and unfissioned or unfused material) to produce
that result — which is just a little more than Shaquille O’Neal weighs.
Such weapons aren’t the most efficient. Weapon designer Theodore Taylor wrote in
1987 that 6 kiloton/kilogram had been pretty much the upper limit of what had even
been achieved. Only a handful of weapons got close to that. The most efficient weapon

16. in the US stockpile was the Mk-41, a ridiculously high yield weapon (25 megatons) that
made up for its weight with a lot of fusion energy.
But given that high efficiency is tied to high yields — and relatively high weights — it’s
clear that the innovations that allowed for the placing of warheads on MIRVed,
submarine-launched platforms are still pretty impressive. The really magical range
seems to be for weapons that in the hundred kiloton range (more than 100 kilotons but
under a megaton), yet under 1,000 kilograms. Every one of those dates from after 1962,
and probably involves the real breakthroughs in warhead design that were first used
with the Operation Dominic test series (1962). This is the kind of strategic
miniaturization that makes war planners happy.
What’s the payoff of thinking about these kinds of numbers? One is that it allows
you to see where innovations have been made, even if you know nothing about how the
weapon works. In other words, yield-to-weight ratios can provide a heuristic for making
sense of nuclear design sophistication, comparing developments over time without
caring about the guts of the weapon itself. It also allows you to make cross-national
comparisons in the same fashion. The French nuclear arsenal apparently
developed weapons in that same miniaturized yield-to-weight range of the United States
by the 1970s — apparently with some help from the United States — and so we can
probably assume that they know whatever the United States figured out about
miniaturized H-bomb design in the 1960s.
Or, to take another tack, and returning to the initial impetus for me looking at this topic,
we know that the famous “Tsar Bomba” of the Soviet Union weighed 27,000 kilograms
and had a maximum yield of 100 Mt, giving it a yield-to-weight ratio of “only” 3.43
kilotons/kilograms. That’s pretty high, but not for a weapon that used so much fusion
energy. It was clear to the Atomic Energy Commission that the Soviets had just scaled
up a traditional H-bomb design and had not developed any new tricks. By contrast, the
US was confident in 1961 that they could make a 100 Mt weapon that weighed around
13,600 kg (30,000 lb) — an impressive 7.35 kiloton/kilogram ratio, something well
above the 6 kt/kg achieved maximum. By 1962, after the Dominic series, they thought
they might be able to pull off 50 Mt in only a 4,500 kg (10,000 lb) package — a kind of
ridiculous 11 kt/kg ratio. (In this estimate, they noted that the weapon might have an
impractically large diameter as a result, perhaps because the secondary was spherical
as opposed to cylindrical.) So we can see, without really knowing much about the
US had in mind, that it was planning something very, very different from what the
Soviets set off.
From KILOTONS PER KILOGRAM by Alex Wellerstein (2013)
Neutron Bomb
A "neutron bomb" is a nuclear warhead design that has been tweaked so it is much better at
killing soldiers and civilians while doing much less damage to military vehicles and civilian
buildings. It makes it easier to kill off the enemy soldiers so you can steal their stuff. Neutron

17. bombs are also good to use if the enemy is invading your country. No sense in blowing huge
holes in your own cities when all you want to do is exterminate enemy soldiers.
This weapons is what you call an "enhanced radiation bomb". They are specially constructed so
more of the bomb's energy is emitted as neutrons instead of x-rays. This means there is far less
blast to damage the buildings, but far more lethal neutron radiation to kill the enemy troops.
Conventional nuclear warheads typically release 5% of the energy as neutrons, but in neutron
bombs it is a whopping 40%. Neutron energy is higher as well: 14 MeV instead of the
conventional 1 to 2 MeV.
A 1 kiloton neutron bomb will irradiate anybody unfortunate enough to be at a range of 900
meters with 80 Grays of neutrons. According to dosages set by the US military, this is high
enough to instantly send the victim into a coma, with certain death to follow within 24 hours due
to damage to the central nervous system. The LD50 dose is at a range of between 1350 and 1400
meters (almost a mile).
Problems include:
 Neutron activation of the steel girders of buildings would render them unsafe. Which was
one of the selling points of neutron bombs: the buildings could be immediately used by
an advancing army, once you removed all the dead enemy soliders.
 Armored fighting vehicles provide enemy soldiers with a surprisingly high protection of
neutron radiation, and can be easily increased. Since all spacecraft include radiation
shielding from solar storms and galactic cosmic rays, this will drastically reduce the
effect of neutron bombs used as anti-spacecraft weapons. Spacecraft with nuclear
propulsion will try to aim their shadow shields at the neutron bomb for added protection.
 Enemy ground soldiers can also find high amounts of protection by sheltering inside
buildings with 12 inch concrete walls and ceiling, or in a cellar under 24 inches of damp
soil. Both will reduce the radiation exposure by a factor of 10.
 Neutron bomb ordinance requires maintenance, since one of the components
is Tritium with its annoyingly short half-life of 12.32 years. This means that every few
years the neutron bombs will have to be opened up and have their tritium replaced.
NEUTRON BOMB

18. 
Energy distribution of
weapon
Energy
type
Proportion of total
energy (%)
Fission Enhanced
Blast 50
40 to
minimum
30
Thermal
energy
35
25 to
minimum
20
Prompt
radiation
5
45 to
minimum
30
Residual
radiation
10 5
A neutron bomb, officially defined as a type of enhanced radiation
weapon (ERW), is a low-yield thermonuclear weapon designed to maximize
lethal neutron radiation in the immediate vicinity of the blast while minimizing the
physical power of the blast itself. The neutron release generated by a nuclear
fusion reaction is intentionally allowed to escape the weapon, rather than being
absorbed by its other components. The neutron burst, which is used as the primary
destructive action of the warhead, is able to penetrate enemy armor more effectively
than a conventional warhead, thus making it more lethal as a tactical weapon.
The concept was originally developed by the US in the late 1950s and early 1960s. It
was seen as a "cleaner" bomb for use against massed Soviet armored divisions. As
these would be used over allied nations, notably West Germany, the reduced blast
damage was seen as an important advantage.

19. ERWs were first operationally deployed for anti-ballistic missiles (ABM). In this role the
burst of neutrons would cause nearby warheads to undergo partial fission, preventing
them from exploding properly. For this to work, the ABM would have to explode within
approximately 100 metres (300 ft) of its target. The first example of such a system was
the W66, used on the Sprint missile used in the US's Nike-X system. It is believed the
Soviet equivalent, the A-135's 53T6 missile, uses a similar design.
The weapon was once again proposed for tactical use by the US in the 1970s and
1980s, and production of the W70 began for the MGM-52 Lance in 1981. This time it
experienced a firestorm of protest as the growing anti-nuclear movement gained
strength through this period. Opposition was so intense that European leaders refused
to accept it on their territory. President Ronald Reagan built examples of the W70-3
which remained stockpiled in the US until they were retired in 1992. The last W70 was
dismantled in 2011.
Basic concept
In a standard thermonuclear design, a small fission bomb is placed close to a larger
mass of thermonuclear fuel. The two components are then placed within a
thick radiation case, usually made from uranium, lead or steel. The case traps the
energy from the fission bomb for a brief period, allowing it to heat and compress the
main thermonuclear fuel. The case is normally made of depleted uranium or natural
uranium metal, because the thermonuclear reactions give off massive numbers of high-
energy neutrons that can cause fission reactions in the casing material. These can add
considerable energy to the reaction; in a typical design as much as 50% of the total
energy comes from fission events in the casing. For this reason, these weapons are
technically known as fission-fusion-fission designs.
In a neutron bomb, the casing material is selected either to be transparent to neutrons
or to actively enhance their production. The burst of neutrons created in the
thermonuclear reaction is then free to escape the bomb, outpacing the physical
explosion. By designing the thermonuclear stage of the weapon carefully, the neutron
burst can be maximized while minimizing the blast itself. This makes the lethal radius of
the neutron burst greater than that of the explosion itself. Since the neutrons disappear
from the environment rapidly, such a burst over an enemy column would kill the crews
and leave the area able to be quickly reoccupied.
Compared to a pure fission bomb with an identical explosive yield, a neutron bomb
would emit about ten times the amount of neutron radiation. In a fission bomb, at sea
level, the total radiation pulse energy which is composed of both gamma rays and
neutrons is approximately 5% of the entire energy released; in neutron bombs it would
be closer to 40%, with the percentage increase coming from the higher production of
neutrons. Furthermore, the neutrons emitted by a neutron bomb have a much higher
average energy level (close to 14 MeV) than those released during a fission reaction
(1–2 MeV).

20. Technically speaking, every low yield nuclear weapon is a radiation weapon, including
non-enhanced variants. All nuclear weapons up to about 10 kilotons in yield have
prompt neutron radiation as their furthest-reaching lethal component. For standard
weapons above about 10 kilotons of yield, the lethal blast and thermal effects radius
begins to exceed the lethal ionizing radiation radius. Enhanced radiation weapons also
fall into this same yield range and simply enhance the intensity and range of the neutron
dose for a given yield.
History and deployment to present
The conception of neutron bombs is generally credited to Samuel T. Cohen of
the Lawrence Livermore National Laboratory, who developed the concept in 1958. Initial
development was carried out as part of projects Dove and Starling, and an early device
was tested underground in early 1962. Designs of a "weaponized" version were carried
out in 1963.
Development of two production designs for the army's MGM-52 Lance short-range
missile began in July 1964, the W63 at Livermore and the W64 at Los Alamos. Both
entered phase three testing in July 1964, and the W64 was cancelled in favor of the
W63 in September 1964. The W63 was in turn cancelled in November 1965 in favor of
the W70 (Mod 0), a conventional design. By this time, the same concepts were being
used to develop warheads for the Sprint missile, an anti-ballistic missile (ABM), with
Livermore designing the W65 and Los Alamos the W66. Both entered phase three
testing in October 1965, but the W65 was cancelled in favor of the W66 in November
1968. Testing of the W66 was carried out in the late 1960s, and it entered production in
June 1974, the first neutron bomb to do so. Approximately 120 were built, with about 70
of these being on active duty during 1975 and 1976 as part of the Safeguard Program.
When that program was shut down they were placed in storage, and eventually
decommissioned in the early 1980s.
Development of ER warheads for Lance continued, but in the early 1970s attention had
turned to using modified versions of the W70, the W70 Mod 3. Development was
subsequently postponed by President Jimmy Carter in 1978 following protests against
his administration's plans to deploy neutron warheads to ground forces in Europe.
On November 17, 1978, in a test the USSR detonated its first similar-type bomb.
President Ronald Reagan restarted production in 1981. The Soviet Union renewed
a propaganda campaign against the US's neutron bomb in 1981 following Reagan's
announcement. In 1983 Reagan then announced the Strategic Defense Initiative, which
surpassed neutron bomb production in ambition and vision and with that, neutron
bombs quickly faded from the center of the public's attention.
Three types of enhanced radiation weapons (ERW) were deployed by the United
States. The W66 warhead, for the anti-ICBM Sprint missile system, was deployed in
1975 and retired the next year, along with the missile system. The W70 Mod 3 warhead
was developed for the short-range, tactical MGM-52 Lance missile, and the W79 Mod 0
was developed for nuclear artillery shells. The latter two types were retired by

21. President George H. W. Bush in 1992, following the end of the Cold War. The last W70
Mod 3 warhead was dismantled in 1996, and the last W79 Mod 0 was dismantled by
2003, when the dismantling of all W79 variants was completed.
According to the Cox Report, as of 1999 the United States had never deployed a
neutron weapon. The nature of this statement is not clear; it reads "The stolen
information also includes classified design information for an enhanced radiation
weapon (commonly known as the "neutron bomb"), which neither the United States, nor
any other nation, has ever deployed." However, the fact that neutron bombs had been
produced by the US was well known at this time and part of the public record. Cohen
suggests the report is playing with the definitions; while the US bombs were never
deployed to Europe, they remained stockpiled in the US.
In addition to the two superpowers, France and China are known to have tested neutron
or enhanced radiation bombs. France conducted an early test of the technology in 1967
and tested an "actual" neutron bomb in 1980. China conducted a successful test of
neutron bomb principles in 1984 and a successful test of a neutron bomb in 1988.
However, neither of those countries chose to deploy neutron bombs. Chinese nuclear
scientists stated before the 1988 test that China had no need for neutron bombs, but it
was developed to serve as a "technology reserve", in case the need arose in the future.
In August 1999, the Indian government disclosed that India was capable of producing a
neutron bomb.
Although no country is currently known to deploy them in an offensive manner, all
thermonuclear dial-a-yield warheads that have about 10 kiloton and lower as one dial
option, with a considerable fraction of that yield derived from fusion reactions, can be
considered able to be neutron bombs in use, if not in name. The only country definitely
known to deploy dedicated (that is, not dial-a-yield) neutron warheads for any length of
time is the Soviet Union/Russia, which inherited the USSR's neutron warhead
equipped ABM-3 Gazelle missile program. This ABM system contains at least 68
neutron warheads with a 10 kiloton yield each and it has been in service since 1995,
with inert missile testing approximately every other year since then (2014). The system
is designed to destroy incoming endoatmospheric nuclear warheads aimed
at Moscow and other targets and is the lower-tier/last umbrella of the A-135 anti-ballistic
missile system (NATO reporting name: ABM-3).
By 1984, according to Mordechai Vanunu, Israel was mass-producing neutron bombs.
Considerable controversy arose in the US and Western Europe following a June
1977 Washington Post exposé describing US government plans to equip US Armed
Forces with neutron bombs. The article focused on the fact that it was the first weapon
specifically intended to kill humans with radiation. Lawrence Livermore National
Laboratory director Harold Brown and Soviet General Secretary Leonid Brezhnev both
described neutron bombs as a "capitalist bomb", because it was designed to destroy
people while preserving property.

22. Use
Neutron bombs are purposely designed with explosive yields lower than other nuclear
weapons. Since neutrons are scattered and absorbed by air, neutron radiation effects
drop off rapidly with distance in air. As such, there is a sharper distinction, relative to
thermal effects, between areas of high lethality and areas with minimal radiation doses.
All high yield (more than c. 10 kiloton) nuclear bombs, such as the extreme example of
a device that derived 97% of its energy from fusion, the 50 megaton Tsar Bomba, are
not able to radiate sufficient neutrons beyond their lethal blast range when detonated as
a surface burst or low altitude air burst and so are no longer classified as neutron
bombs, thus limiting the yield of neutron bombs to a maximum of about 10 kilotons. The
intense pulse of high-energy neutrons generated by a neutron bomb is the principal
killing mechanism, not the fallout, heat or blast.
The inventor of the neutron bomb, Sam Cohen, criticized the description of the W70 as
a neutron bomb since it could be configured to yield 100 kilotons:
the W-70 ... is not even remotely a "neutron bomb." Instead of being the type of weapon
that, in the popular mind, "kills people and spares buildings" it is one that both kills and
physically destroys on a massive scale. The W-70 is not a discriminate weapon, like the
neutron bomb—which, incidentally, should be considered a weapon that "kills enemy
personnel while sparing the physical fabric of the attacked populace, and even the
populace too."
Although neutron bombs are commonly believed to "leave the infrastructure intact", with
current designs that have explosive yields in the low kiloton range, detonation in (or
above) a built-up area would still cause a sizable degree of building destruction, through
blast and heat effects out to a moderate radius, albeit considerably less destruction,
than when compared to a standard nuclear bomb of the exact same total energy
release or "yield".
The Warsaw Pact tank strength was over twice that of NATO, and Soviet deep battle
doctrine was likely to be to use this numerical advantage to rapidly sweep across
continental Europe if the Cold War ever turned hot. Any weapon that could break up
their intended mass tank formation deployments and force them to deploy their tanks in
a thinner, more easily dividable manner, would aid ground forces in the task of hunting
down solitary tanks and using anti-tank missiles against them, such as the
contemporary M47 Dragon and BGM-71 TOW missiles, of which NATO had hundreds
of thousands.
Rather than making extensive preparations for battlefield nuclear combat in Central
Europe, "The Soviet military leadership believed that conventional superiority provided
the Warsaw Pact with the means to approximate the effects of nuclear weapons and
achieve victory in Europe without resort to those weapons."

23. Neutron bombs, or more precisely, enhanced [neutron] radiation weapons were also to
find use as strategic anti-ballistic missile weapons, and in this role they are believed to
remain in active service within Russia's Gazelle missile.
Effects
Upon detonation, a near-ground airburst of a 1 kiloton neutron bomb would produce a
large blast wave and a powerful pulse of both thermal radiation and ionizing radiation in
the form of fast (14.1 MeV) neutrons. The thermal pulse would cause third degree
burns to unprotected skin out to approximately 500 meters. The blast would create
pressures of at least 4.6 psi out to a radius of 600 meters, which would severely
damage all non-reinforced concrete structures. At the conventional effective combat
range against modern main battle tanks and armored personnel carriers (< 690–900 m),
the blast from a 1 kt neutron bomb would destroy or damage to the point of nonusability
almost all un-reinforced civilian buildings.
Using neutron bombs to stop an enemy armored attack by rapidly incapacitating crews
with a dose of 80+ Gy of radiation would require exploding large numbers of them to
blanket the enemy forces, destroying all normal civilian buildings within c. 600 meters of
the immediate area. Neutron activation from the explosions could make many building
materials in the city radioactive, such as galvanized steel (see area denial use below).
Because liquid-filled objects like the human body are resistant to gross overpressure,
the 4–5 psi blast overpressure would cause very few direct casualties at a range of
c. 600 m. The powerful winds produced by this overpressure, however, could throw
bodies into objects or throw debris at high velocity, including window glass, both with
potentially lethal results. Casualties would be highly variable depending on
surroundings, including potential building collapses.
The pulse of neutron radiation would cause immediate and permanent incapacitation to
unprotected outdoor humans in the open out to 900 meters, with death occurring in one
or two days. The median lethal dose (LD50) of 6 Gray would extend to between 1350
and 1400 meters for those unprotected and outdoors, where approximately half of those
exposed would die of radiation sickness after several weeks.
A human residing within, or simply shielded by, at least one concrete building with walls
and ceilings 30 cm (12 in) thick, or alternatively of damp soil 24 inches thick, would
receive a neutron radiation exposure reduced by a factor of 10. Even near ground zero,
basement sheltering or buildings with similar radiation shielding characteristics would
drastically reduce the radiation dose.
Furthermore, the neutron absorption spectrum of air is disputed by some authorities,
and depends in part on absorption by hydrogen from water vapor. Thus, absorption
might vary exponentially with humidity, making neutron bombs far more deadly in desert
climates than in humid ones.

24. Effectiveness in modern anti-tank role
See also: Centurion Tank § Nuclear tests, Object 279, and Signs and symptoms of
radiation poisoning § "Walking Ghost phase"
The questionable effectiveness of ER weapons against modern tanks is cited as one of
the main reasons that these weapons are no longer fielded or stockpiled. With the
increase in average tank armor thickness since the first ER weapons were fielded, it
was argued in the March 13, 1986, New Scientist magazine that tank armor protection
was approaching the level where tank crews would be almost fully protected from
radiation effects. Thus, for an ER weapon to incapacitate a modern tank crew through
irradiation, the weapon must be detonated at such proximity to the tank that the nuclear
explosion's blast would now be equally effective at incapacitating it and its crew.
However this assertion was regarded as dubious in the June 12, 1986, New
Scientist reply by C.S. Grace, a member of the Royal Military College of Science, as
neutron radiation from a 1 kiloton neutron bomb would incapacitate the crew of a tank
with a protection factor of 35 out to a range of 280 meters, but the incapacitating blast
range, depending on the exact weight of the tank, is much less, from 70 to 130 meters.
However although the author did note that effective neutron absorbers and neutron
poisons such as boron carbide can be incorporated into conventional armor and strap-
on neutron moderating hydrogenous material (substances containing hydrogen atoms),
such as explosive reactive armor, can both increase the protection factor, the author
holds that in practice combined with neutron scattering, the actual average total tank
area protection factor is rarely higher than 15.5 to 35. According to the Federation of
American Scientists, the neutron protection factor of a "tank" can be as low as 2, without
qualifying whether the statement implies a light tank, medium tank, or main battle tank.
A composite high density concrete, or alternatively, a laminated graded-Z shield, 24
units thick of which 16 units are iron and 8 units are polyethylene containing boron
(BPE), and additional mass behind it to attenuate neutron capture gamma rays, is more
effective than just 24 units of pure iron or BPE alone, due to the advantages of both iron
and BPE in combination. During Neutron transport Iron is effective in slowing
down/scattering high-energy neutrons in the 14-MeV energy range and attenuating
gamma rays, while the hydrogen in polyethylene is effective in slowing down these now
slower fast neutrons in the few MeV range, and boron 10 has a high absorption cross
section for thermal neutrons and a low production yield of gamma rays when it absorbs
a neutron. The Soviet T72 tank, in response to the neutron bomb threat, is cited as
having fitted a boronated polyethylene liner, which has had its neutron shielding
properties simulated.
However, some tank armor material contains depleted uranium (DU), common in the
US's M1A1 Abrams tank, which incorporates steel-encased depleted uranium armor, a
substance that will fast fission when it captures a fast, fusion-generated neutron, and
thus on fissioning will produce fission neutrons and fission products embedded within
the armor, products which emit among other things, penetrating gamma rays. Although

25. the neutrons emitted by the neutron bomb may not penetrate to the tank crew in lethal
quantities, the fast fission of DU within the armor could still ensure a lethal environment
for the crew and maintenance personnel by fission neutron and gamma ray exposure,
largely depending on the exact thickness and elemental composition of the armor—
information usually hard to attain. Despite this, Ducrete—which has an elemental
composition similar (but not identical) to the ceramic second generation heavy metal
Chobham armor of the Abrams tank—is an effective radiation shield, to
both fission neutrons and gamma rays due to it being a graded Z material. Uranium,
being about twice as dense as lead, is thus nearly twice as effective at shielding gamma
ray radiation per unit thickness.
Use against ballistic missiles
As an anti-ballistic missile weapon, the first fielded ER warhead, the W66, was
developed for the Sprint missile system as part of the Safeguard Program to protect
United States cities and missile silos from incoming Soviet warheads.
A problem faced by Sprint and similar ABMs was that the blast effects of their warheads
change greatly as they climb and the atmosphere thins out. At higher altitudes, starting
around 60,000 feet (18,000 m) and above, the blast effects begin to drop off rapidly as
the air density becomes very low. This can be countered by using a larger warhead, but
then it becomes too powerful when used at lower altitudes. An ideal system would use a
mechanism that was less sensitive to changes in air density.
Neutron-based attacks offer one solution to this problem. The burst of neutrons
released by an ER weapon can induce fission in the fissile materials of primary in the
target warhead. The energy released by these reactions may be enough to melt the
warhead, but even at lower fission rates the "burning up" of some of the fuel in the
primary can cause it to fail to explode properly, or "fizzle". Thus a small ER warhead
can be effective across a wide altitude band, using blast effects at lower altitudes and
the increasingly long-ranged neutrons as the engagement rises.
The use of neutron-based attacks was discussed as early as the 1950s, with the
US Atomic Energy Commission mentioning weapons with a "clean, enhanced neutron
output" for use as "antimissile defensive warheads." Studying, improving and defending
against such attacks was a major area of research during the 1950s and 60s. A
particular example of this is the US Polaris A-3 missile, which delivered three warheads
travelling on roughly the same trajectory, and thus with a short distance between them.
A single ABM could conceivably destroy all three through neutron flux. Developing
warheads that were less sensitive to these attacks was a major area of research in the
US and UK during the 1960s.
Some sources claim that the neutron flux attack was also the main design goal of the
various nuclear-tipped anti-aircraft weapons like the AIM-26 Falcon and CIM-10
Bomarc. One F-102 pilot noted:

26. GAR-11/AIM-26 was primarily a weapon-killer. The bomber(s, if any) was collateral
damage. The weapon was proximity-fused to ensure detonation close enough so an
intense flood of neutrons would result in an instantaneous nuclear reaction (NOT full-
scale) in the enemy weapon’s pit; rendering it incapable of functioning as
designed...[O]ur first “neutron bombs” were the GAR-11 and MB-1 Genie.
It has also been suggested that neutron flux's effects on the warhead electronics are
another attack vector for ER warheads in the ABM role. Ionization greater than
50 Gray in silicon chips delivered over seconds to minutes will degrade the function
of semiconductors for long periods. However, while such attacks might be useful
against guidance systems which used relatively advanced electronics, in the ABM role
these components have long ago separated from the warheads by the time they come
within range of the interceptors. The electronics in the warheads themselves tend to be
very simple, and hardening them was one of the many issues studied in the 1960s.
Lithium-6 hydride (Li6H) is cited as being used as a countermeasure to reduce the
vulnerability and "harden" nuclear warheads from the effects of externally generated
neutrons. Radiation hardening of the warhead's electronic components as a
countermeasure to high altitude neutron warheads somewhat reduces the range that a
neutron warhead could successfully cause an unrecoverable glitch by the transient
radiation effects on electronics (TREE) effects.
At very high altitudes, at the edge of the atmosphere and above it, another effect comes
into play. At lower altitudes, the x-rays generated by the bomb are absorbed by the air
and have mean free paths on the order of meters. But as the air thins out, the x-rays
can travel further, eventually outpacing the area of effect of the neutrons. In
exoatmospheric explosions, this can be on the order of 10 kilometres (6.2 mi) in radius.
In this sort of attack, it is the x-rays promptly delivering energy on the warhead surface
that is the active mechanism; the rapid ablation (or "blow off") of the surface creates
shock waves that can break up the warhead.
Use as an area denial weapon
In November 2012, during the planning stages of Operation Hammer of God, British
Labour peer Lord Gilbert suggested that multiple enhanced radiation reduced blast
(ERRB) warheads could be detonated in the mountain region of the Afghanistan-
Pakistan border to prevent infiltration. He proposed to warn the inhabitants to evacuate,
then irradiate the area, making it unusable and impassable. Used in this manner, the
neutron bomb(s), regardless of burst height, would release neutron activated casing
materials used in the bomb, and depending on burst height, create radioactive
soil activation products.
In much the same fashion as the area denial effect resulting from fission product (the
substances that make up most fallout) contamination in an area following a
conventional surface burst nuclear explosion, as considered in the Korean War
by Douglas MacArthur, it would thus be a form of radiological warfare—with the

27. difference that neutron bombs produce half, or less, of the quantity of fission products
relative to the same-yield pure fission bomb. Radiological warfare with neutron bombs
that rely on fission primaries would thus still produce fission fallout, albeit a
comparatively cleaner and shorter lasting version of it in the area than if air bursts were
used, as little to no fission products would be deposited on the direct immediate area,
instead becoming diluted global fallout.
However the most effective use of a neutron bomb with respect to area denial would be
to encase it in a thick shell of material that could be neutron activated, and use a
surface burst. In this manner the neutron bomb would be turned into a salted bomb; a
case of zinc-64, produced as a byproduct of depleted zinc oxide enrichment, would for
example probably be the most attractive for military use, as when activated, the zinc-65
so formed is a gamma emitter, with a half life of 244 days.
Hypothetical effects of a pure fusion bomb
With considerable overlap between the two devices, the prompt radiation effects of
a pure fusion weapon would similarly be much higher than that of a pure-fission device:
approximately twice the initial radiation output of current standard fission-fusion-based
weapons. In common with all neutron bombs that must presently derive a small
percentage of trigger energy from fission, in any given yield a 100% pure fusion bomb
would likewise generate a more diminutive atmospheric blast wave than a pure-fission
bomb. The latter fission device has a higher kinetic energy-ratio per unit of reaction
energy released, which is most notable in the comparison with the D-T fusion reaction.
A larger percentage of the energy from a D-T fusion reaction, is inherently put into
uncharged neutron generation as opposed to charged particles, such as the alpha
particle of the D-T reaction, the primary species, that is most responsible for
the coulomb explosion/fireball.
From the Wikipedia entry for NEUTRON BOMB
NEUTRON BOMB DRAWBACKS
Scratch the beam weapon, then. But at least deploying a particle beam generator
would not do our own side any great harm, and that is more than can be said for the
neutron bomb.
The first thing to know about a neutron bomb— more politely called the “enhanced
radiation weapon"—is that it isn't very different from any other nuclear bomb. It
produces heat, blast and fall-out as well as radiation, and a lot of all of them. The only
thing that makes it special is that it produces a higher proportion of radiation than other
types. So it is not, by any stretch of the imagination, the dreamed "clean" bomb that will
selectively kill all your enemies and leave their cities and machines and farms intact.

28. It has one special property, though. It is the only weapon I can think of that makes
your enemy more dangerous after you have used it than before.
The best way to see the reason for this is to draw some circles on the nearest polka-
dotted surface, perhaps your kitchen linoleum. Draw five concentric circles, with radii of
one foot, eighteen inches, two feet, two and a half feet and three feet. If you let each
foot represent 500 yards, your smallest, innermost circle contains an area representing
some 800,000 square yards.
This is your area immediately around ground zero. It is also the only place where the
neutron bomb works exactly as advertised, so cherish it. Perhaps you have forty polka-
dots in that inner circle. Let each one stand for 100 enemy soldiers, so that you have a
combat brigade of 4,000 men, in tanks and out of them, in that area. You have wiped
them out. All four thousand of them are effectively dead men. Every one will have
received an average of 18,000 rads (180 grays) of whole-body exposure, and so they
are either dead or in coma within five minutes. The ones that don't die at once will surely
do so within twenty-four hours. None of them will ever fight again.
However, the bomb does not confine itself to that inner circle.
In the ring between the one-foot and eighteen-inch circles you probably have fifty
dots, representing 5,000 other men. They're out of it, too, having received some 8,000
rads (80 grays) each, but they may not die for 48 hours. You probably don't have to
worry about any of them for long, but a few may be able to function briefly.
Between the 18-inch and two-foot circles (the range from 750 to 1000 yards in the
real world) you probably have 70 polka-dots, representing 7,000 men. These are surely
dead men, too. But now we come to the real problem. They will take a while to die. They
are knocked out in five minutes, even inside a tank. But then they recover briefly. They
can operate quite normally for a period of several hours, sometimes longer, before
relapsing and ultimately dying within 48 to 96 hours of their 3000-rad (30 gray) dose.
Between the two-foot and thirty-inch circles you have 90 polka-dots, or 9,000 men.
They have received 650 rads (6.5 gray) each on average. At first they are impaired but
still functioning. That lasts for a couple of hours, then they begin a slow decline. Most
will be dead in a matter of weeks. The rest will die later, and worse, of cancer.
And between the thirty-inch and three-foot circles you have 110 polka-dots,
representing 11,000 men, who have received only 250 rads (2.5 gray). For hours or
even days they will seem essentially normal. Their fighting ability will be unimpaired. But
they are doomed, and they know it. Most will be dead within a few months. Almost all of
the rest will never be well again, and will die of their ailments sooner or later.
Of course, beyond the three-foot circle you have a lot of other people, many of whom
will also be damaged and some of whom will also die, but not quickly. How many there

29. will be is a matter of prevailing winds and the path the radioactive plume takes. Some of
them may well be soldiers, or civilians, on the side that deploys the weapon.
To put it another way, out of every thousand casualties within a radius of a mile from
ground zero, about 160 will be knocked out within five minutes, dying then or shortly
thereafter.
But about 400 will be killed, and know they have been killed, and still be able to
function—which means to fight—for some time afterward.
There is a name for soldiers like these. They are called "kamikazes."
Most people don't want to die, and so the fiercest attack is blunted by some residual
instinct for self-preservation. These people have none. We have had bitter experience
of what kamikazes can do. In 1945, when the United States forces had effectively driven
the Japanese off the sea and out of the air, a handful of these doomed warriors nearly
won a battle against odds in materiel and men of at least a hundred to one. Only a few
hundred Japanese participated in the kamikaze attacks. Every time we dropped a one-
kiloton neutron bomb on a troop concentration we would be creating perhaps 25,000 of
them.
The other thing about a neutron bomb is that it is still a bomb.
It is a one or two kiloton nuclear weapon. Apart from its radiation effects, it will
convert a large piece of territory into something that looks a lot like Hiroshima or
Nagasaki. The main difference is that the odds are that it would be employed in
relatively open territory rather than on a city.
But cities can be rebuilt rather quickly. Farms, forests and grazing lands cannot. A
coniferous forest would take three centuries to recover completely. Hardwood would
take almost as long; tundra, which is exceptionally fragile, even longer. Even grasslands
would not become fully productive again for a generation or two.
So the neutron bomb is not very clean—or very desirable on any count, when you
take into account its capacity for converting ordinary troops into something like Ali Ben
Hassan's hashish-filled suicide squads.
From THE WIZARD WARS by Frederik Pohl (1980)
Salted Bomb
You will also occasionally find references to a nasty weapon called a "cobalt bomb". This is
technically termed a "salted bomb". It is not used for spacecraft to spacecraft combat, it is only
used for planetary bombardment. The purpose is to render the land downwind of ground-zero so
radioactive that it will be unsafe to enter for the next few thousand years. They are spiteful
weapons, sending the message that if the attacker cannot have the land, then nobody can have it.

30. They are enhanced-fallout weapons, with jackets of cobalt or zinc to generate large quantities of
deadly radioactive cobalt or zinc isotope dust. The warhead proper will probably be a neutron
bomb: since the more neutrons emitted by the warhead, the more of the jacket will be neutron-
activated into radioactive isotopes.
Suggested elements include cobalt, gold, tantalum, zinc, and sodium. The idea is to use as a
jacket some element that will neutron activate into an isotope which is a high intensity gamma
ray emitter with a long half-life.
Please note the difference between a "salted bomb" and a "dirty bomb".
A dirty bomb is an ordinary chemical explosive in a small bag of ground-up radioactive material.
The chemical explosion merely sprays the powdered plutonium or whatever all over the city
block. Strictly a terrorist weapon, it is pretty worthless as a military weapon.
A salted bomb is a nuclear warhead designed to make a nuclear explosion that will
spread millions of bagfulls of fallout that is thousands of times more radioactive that mere
powdered plutonium over a quarter of a continent.
Term comes from metaphor "sowing the Earth with salt".
SALTED BOMB

A salted bomb is a nuclear weapon designed to function as a radiological weapon,
producing enhanced quantities of radioactive fallout, rendering a large area
uninhabitable. The term is derived both from the means of their manufacture, which
involves the incorporation of additional elements to a standard atomic weapon, and from
the expression "to salt the earth", meaning to render an area uninhabitable for
generations. The idea originated with Hungarian-American physicist Leo Szilard, in
February 1950. His intent was not to propose that such a weapon be built, but to show
that nuclear weapon technology would soon reach the point where it could end human
life on Earth.
No intentionally salted bomb has ever been atmospherically tested, and as far as is
publicly known, none has ever been built. However, the UK tested a one-kiloton bomb
incorporating a small amount of cobalt as an experimental radiochemical tracer at

31. their Tadje testing site in Maralinga range, Australia, on September 14, 1957. The triple
"taiga" nuclear salvo test, as part of the preliminary March 1971 Pechora–Kama
Canal project, converted significant amounts of stable cobalt-59 to radioactive cobalt-
60 by fusion-generated neutron activation and this product is responsible for about half
of the gamma dose measured at the test site in 2011. The experiment was regarded as
a failure and not repeated.
A salted bomb should not be confused with a "dirty bomb", which is an ordinary
explosive bomb containing radioactive material which is spread over the area when the
bomb explodes. A salted bomb is able to contaminate a much larger area than a dirty
bomb.
Design
Salted versions of both fission and fusion weapons can be made by surrounding the
core of the explosive device with a material containing an element that can be
converted to a highly radioactive isotope by neutron bombardment. When the bomb
explodes, the element absorbs neutrons released by the nuclear reaction, converting it
to its radioactive form. The explosion scatters the resulting radioactive material over a
wide area, leaving it uninhabitable far longer than an area affected by typical nuclear
weapons. In a salted hydrogen bomb, the radiation case around the fusion fuel, which
normally is made of some fissionable element, is replaced with a metallic salting
element. Salted fission bombs can be made by replacing the neutron reflector between
the fissionable core and the explosive layer with a metallic element. The
energy yield from a salted weapon is usually lower than from an ordinary weapon of
similar size as a consequence of these changes.
The radioactive isotope used for the fallout material would be a high-intensity gamma
ray emitter, with a half-life long enough that it remains lethal for an extended period. It
would also have to have a chemistry that causes it to return to earth as fallout, rather
than stay in the atmosphere after being vaporized in the explosion. Another
consideration is biological: radioactive isotopes of elements normally taken up by plants
and animals as nutrition would pose a special threat to organisms that absorbed them,
as their radiation would be delivered from within the body of the organism.
Radioactive isotopes that have been suggested for salted bombs include gold-
198, tantalum-182, zinc-65, and cobalt-60. Physicist W. H. Clark looked at the potential
of such devices and estimated that a 20 megaton bomb salted with sodium would
generate sufficient radiation to contaminate 200,000 square miles (520,000 km2) (an
area that is slightly larger than Spain or Thailand, though smaller than France). Given
the intensity of the gamma radiation, not even those in basement shelters could survive
within the fallout zone. However, the short half-life of sodium-24 (15 h) would mean that
the radiation would not spread far enough to be a true doomsday weapon.
A cobalt bomb was first suggested by Leo Szilard, who publicly sounded the alarm
against the possible development of a salted thermonuclear bombs that might annihilate

32. mankind in a University of Chicago Round Table radio program on February 26, 1950.
His comments, as well as those of Hans Bethe, Harrison Brown, and Frederick
Seitz (the three other scientists who participated in the program), were attacked by
the Atomic Energy Commission's former Chairman David Lilienthal, and the criticisms
plus a response from Szilard were published. Time compared Szilard to Chicken
Little while the AEC dismissed his ideas, but scientists debated whether it was feasible
or not. The Bulletin of the Atomic Scientists commissioned a study by James R. Arnold,
who concluded that it was. Clark suggested that a 50 megaton cobalt bomb did have
the potential to produce sufficient long-lasting radiation to be a doomsday weapon, in
theory, but was of the view that, even then, "enough people might find refuge to wait out
the radioactivity and emerge to begin again."
In popular culture
This concept is best known from the Soviet "Doomsday Machine" in the 1964 satirical
Cold War film Dr. Strangelove. In the 1957 novel On the Beach by Nevil Shute, the
death of all humanity is brought about by the detonation of cobalt bombs in the Northern
Hemisphere. In the 1964 James Bond film Goldfinger, the villain's plan is to detonate a
"particularly dirty" atomic device, salted with cobalt and iodine inside the United States
Bullion Depository at Fort Knox, thereby rendering the U.S.'s gold reserves radioactive
for almost six decades. The 1970s movie Beneath the Planet of the Apes featured an
atomic bomb that was hypothesized[citation needed] to use a cobalt casing. The use of a
salted bomb is a component to the plot of Frank Miller's graphic novel series The Dark
Knight Returns and 2008 TV programme Ultimate Force Slow Bomb episode. Also, in
the ABC show The Whispers season 1 episode 5, a "salted bomb" was referred to as a
nuclear bomb laced with arsenic, also known as "A.S. 33". The final level of Metro
Exodus takes place in the city of Novosibirsk, which the main characters surmise was
devastated by a nuclear device salted with cobalt, based on the lack of physical
damage to the city yet massive levels of radioactive contamination as well as character
dialog.
From the Wikipedia entry for SALTED BOMB
Chemical-Explosion Thermonuclear

33. 
Thermonuclear weapons are typically a mass of fusion fuel (with some other items) that are
ignited to fusion temperatures by a fission bomb "match." The requirement of an atom bomb to
light off your h-bomb is a bit inefficient. In science fiction one occasionally encounters fusion
weapons that contain unobtainium capacitors powering honking huge lasers to ignite fusion. You
might save on plutonium, but this is hardly cheaper than conventional fusion warheads.
Finn van Donkelaar has been playing around with another concept. It might be barely possible to
ignite a small fusion reaction using chemical explosives. Maybe. Not out of the question.
Possibly. Not impossible. Sort of.
His initial write up is very interesting reading, abet loaded with nasty equations. He notes it has a
lower yield-to-weight ratio compared to conventional fusion warheads (which is bad), but has a
couple of advantages. Which you can read about in the report.
He calculate the device in the diagram above is at the low end of possible yields. Mass of 20
kilograms, length of 45 centimeters, diameter of 8 centimeters, and a yield of 250 kg of TNT.
Scaled up to largest reasonably portable size the same design would have a mass of 1.6 metric
tons, length of 2.5 meters, diameter of 40 centimeters, and a yield of 2 kilotons of TNT.
EMP

34. When it comes to the dreaded EMP created by nuclear detonations, matters become somewhat
complicated. Please, do NOT confuse EMP (electromagnetic Pulse) with
EM (electromagnetic Radiation).
Most SF fans have a somewhat superficial understanding of EMP: an evil foreign nation
launches an ICBM at the United States, the nuke detonates in the upper atmosphere over the
Midwest, an EMP is generated, the EMP causes all stateside computers to explode, all the TVs
melt, all the automobile electrical systems short out, all the cell phones catch fire, basically
anything that uses electricity is destroyed.
This is true as far as it goes, but when you start talking about deep space warfare, certain things
change. Thanks to Andrew Presby for setting me straight on this matter.
First off, the EMP I just described is High Altitude EMP (HEMP). This EMP can only be
generated if there is a Terra strength magnetic field and a tenuous atmosphere present. A nuke
going off in deep space will not generate HEMP. Please be aware, however, if a nuke over
Iowa generates a HEMP event, the EMP will travel through the airless vacuum of space just fine
and fry any spacecraft that are too close.
Secondly, EMP can also be generated in airless space by an e-Bomb, which uses chemical
explosives and an armature. No magnetic field nor atmosphere required. This is called a Non-
nuclear electromagnetic pulse (NNEMP). As with all EMPs, once generated they will travel
through space and kill spacecraft.
Thirdly, there is System Generated EMP (SGEMP) to consider. HEMP is created when the
gamma rays from the nuclear detonation produce Compton electrons in air molecules, and the
electrons interact with a magnetic field to produce EMP. But with SGEMP, gamma rays
penetrating the body of the spacecraft accelerated electrons, creating electromagnetic transients.
SGEMP impacts space system electronics in three ways. First, x-rays arriving at the
spacecraft skin cause an accumulation of electrons there. The electron charge, which is
not uniformly distributed on the skin, causes current to flow on the outside of the
system. These currents can penetrate into the interior through various apertures, as well
as into and through the solar cell power transmission system. Secondly, x-rays can also
penetrate the skin to produce electrons on the interior walls of the various
compartments. The resulting interior electron currents generate cavity electromagnetic
fields that induce voltages on the associated electronics which produce spurious
currents that can cause upset or burnout of these systems. Finally, x-rays can produce
electrons that find their way directly into signal and power cables to cause extraneous
cable currents. These currents are also propagated through the satellite wiring harness.
Dr. George W. Ullrich

35. ImpulsiveShock


A one kiloton nuclear detonation produces 4.19e12 joules of energy. One kilometer away from
the detonation point defines a sphere with a surface area of about 12,600,000 square meters (the
increase in surface area with the radius of the sphere is another way of stating the Inverse
Square law). Dividing reveals that at this range the energy density is approximately 300
kilojoules per square meter. Under ideal conditions this would be enough energy to vaporize 25

36. grams or 10 cubic centimeters of aluminum (in reality it won't be this much due to conduction
and other factors).
1e8 watts per square centimeter for about a microsecond will melt part of the surface of a sheet
of aluminum. 1e9 W/cm2 for a microsecond will vaporize the surface, and 1e11 W/cm2 for a
microsecond will cause enough vaporization to create impulsive shock damage (i.e., the surface
layer of the material is vaporized at a rate exceeding the speed of sound). The one kiloton bomb
at one kilometer only does about 3.3e7 W/cm2 for a microsecond.
One megaton at one kilometer will do 3.3e10 W/cm2, enough to vaporize but not quite enough
for impulsive shock. At 100 meters our one meg bomb will do 3.3e12 W/cm2, or about 33 times
more energy than is required for impulsive shock. The maximum range for impulsive shock is
about 570 meters.
Luke Campbell wonders if 1e11 W/cm2 is a bit high as the minimum irradiation to create
impulsive shock damage. With lasers in the visible light and infrared range, 1e9 W/cm2 to 1e10
W/cm2 is enough. But he allows that matters might be different for x-rays and gamma rays due to
their extra penetration.
As to the effects of impulsive damage, Luke Campbell had this to say:
First, consider a uniform slab of material subject to uniform irradiation sufficient to cause
an impulsive shock. A thin layer will be vaporized and a planar shock will propagate into
the material. Assuming that the shock is not too intense (i.e., not enough heat is
dumped into the slab to vaporize or melt it) there will be no material damage because of
the planar symmetry. However, as the shock reaches the back side of the slab, it will be
reflected. This will set up stresses on the rear surface, which tends to cause pieces of
the rear surface to break off and fly away at velocities close to the shock wave velocity
(somewhat reduced, of course, due to the binding energy of all those chemical bonds
you need to break in order to spall off that piece). This spallation can cause significant
problems to objects that don't have anything separating them from the hull. Modern
combat vehicles take pains to protect against spallation for just this reason (using an
inner layer of Kevlar or some such).
Now, if the material or irradiance is non-uniform, there will be stresses set up inside the
hull material. If these exceed the strength of the material, the hull will deform or crack.
This can cause crumpling, rupturing, denting (really big dents), or shattering depending
on the material and the shock intensity.
For a sufficiently intense shock, shock heating will melt or vaporize the hull material,
with obvious catastrophic results. At higher intensities, the speed of radiation diffusion of
the nuke x-rays can exceed the shock speed, and the x-rays will vaporize the hull
before the shock can even start. Roughly speaking, any parts of the hull within the
diameter of an atmospheric fireball will be subject to this effect.

37. In any event, visually you would see a bright flash from the surface material that is
heated to incandescence. The flash would be sudden, only if the shock is so intense as
to cause significant heating would you see any extra light for more than one frame of
the animation (if the hull material is heated, you can show it glowing cherry red or yellow
hot or what have you). The nuke itself would create a similar instant flash. There would
probably be something of an afterglow from the vaporized remains of the nuke and
delivery system, but it will be expanding in a spherical cloud so quickly I doubt you
would be able to see it. Shocks in rigid materials tend to travel at something like 10
km/s, shock induced damage would likewise be immediate. Slower effects could occur
as the air pressure inside blasts apart the weakened hull or blows out the shattered
chunks, or as transient waves propagate through the ship's structure, or when structural
elements are loaded so as to shatter normally rather than through the shock. Escaping
air could cause faintly visible jets as moisture condenses/freezes out - these would form
streamers shooting away from the spacecraft at close to the speed of sound in air - NO
billowing clouds.
Luke Campbell
Nuke vs. Spacecraft

Dr. John Schilling describes the visual appearance of a nuclear strike on a spacecraft.

38. First off, the weapon itself. A nuclear explosion in space, will look pretty much like a
Very Very Bright flashbulb going off. The effects are instantaneous or nearly so. There
is no fireball. The gaseous remains of the weapon may be incandescent, but they are
also expanding at about a thousand kilometers per second, so one frame after
detonation they will have dissipated to the point of invisibility. Just a flash.
The effects on the ship itself, those are a bit more visible. If you're getting impulsive
shock damage, you will by definition see hot gas boiling off from the surface. Again, the
effect is instantaneous, but this time the vapor will expand at maybe one kilometer per
second, so depending on the scale you might be able to see some of this action. But
don't blink; it will be quick.
Next is spallation - shocks will bounce back and forth through the skin of the target,
probably tearing chunks off both sides. Some of these may come off at mere hundreds
of meters per second. And they will be hot, red- or maybe even white-hot depending on
the material.
To envision the appearance of this part, a thought experiment. Or, heck, go ahead and
actually perform it. Start with a big piece of sheet metal, covered in a fine layer of flour
and glitter. Shine a spotlight on it, in an otherwise-dark room. Then whack the thing with
a sledgehammer, hard enough for the recoil to knock the flour and glitter into the air.
The haze of brightly-lit flour is your vaporized hull material, and the bits of glitter are the
spallation. Scale up the velocities as needed, and ignore the bit where air resistance
and gravity brings everything to a halt.
Next, the exposed hull is going to be quite hot, probably close to the melting point. So,
dull red even for aluminum, brilliant white for steel or titanium or most ceramics or
composites. The seriously hot layer will only be a millimeter or so thick, so it can cool
fairly quickly - a second or two for a thick metallic hull that can cool by internal
conduction, possibly as long as a minute for something thin and/or insulating that has to
cool by radiation.
After this, if the shock is strong enough, the hull is going to be materially deformed. For
this, take the sledgehammer from your last thought experiment and give a whack to
some tin cans. Depending on how hard you hit them, and whether they are full or
empty, you can get effects ranging from mild denting at weak points, crushing and
tearing, all the way to complete obliteration with bits of tin-can remnant and tin-can
contents splattered across the landscape.
Again, this will be much faster in reality than in the thought experiment. And note that a
spacecraft will have many weak points to be dented, fragile bits to be torn off, and they
all get hit at once. If the hull is of isogrid construction, which is pretty common, you
might see an intact triangular lattice with shallow dents in between. Bits of antenna and
whatnot, tumbling away.

39. Finally, secondary effects. Part of your ship is likely to be pressurized, either habitat
space or propellant tank. Coolant and drinking water and whatnot, as well. With serious
damage, that stuff is going to vent to space. You can probably see this happening (air
and water and some propellants will freeze into snow as they escape, BTW). You'll also
see the reaction force try to tumble the spacecraft, and if the spacecraft's attitude
control systems are working you'll see them try to fight back.
You might see fires, if reactive materials are escaping. But not convection flames, of
course. Diffuse jets of flame, or possibly surface reactions. Maybe secondary
explosions if concentrations of reactive gasses are building up in enclosed (more or
less) spaces.
Dr. John Schilling
Radiation Flux

Crew members are not as durable as spacecraft, since they are vulnerable to neutron radiation. A
one megaton Enhanced-Radiation warhead (AKA "neutron bomb") will deliver a threshold fatal
neutron dose to an unshielded human at 300 kilometers. There are also reports that ER warheads
can transmute the structure of the spacecraft into deadly radioactive isotopes by the toxic magic
of neutron activation. Details are hard to come by, but it was mentioned that a main battle tank
irradiated by an ER weapon would be transmuted into isotopes that would inflict lethal radiation
doses for up to 48 hours after the irradiation. So if you want to re-crew a spacecraft depopulated
by a neutron bomb, better let it cool off for a week or so.
For a conventional nuclear weapon (i.e., NOT a neutron bomb), the x-ray and neutron flux is
approximately:

40. Fx = 2.6 x 1027 * (Y/R2)
Fn = 1.8 x 1023 * (Y/R2)
where:
 Fx = X-ray fluence (x-rays/m2)
 Fn = Neutron fluence (neutrons/m2)
 Y = weapon yield (kilotons TNT)
 R = range from ground zero (meters)
There are notes on the effects of radiation on crew and electronics here.
Nuclear Shaped Charges


41. 
My silly attempt at designing a casaba howitzer weapon

From Aerospace Project Review vol 2, no.2 by Scott Lowther

W: warhead
A: attitude control system
B: Pancake booster rocket
Back in the 1960's, rocket scientist came up with the infamous "Orion Drive." This was
basically a firecracker under a tin can. Except the tin can is a spacecraft, and the firecracker is a
nuclear warhead.
Anyway, they realized that about 99% of the nuclear energy of an unmodified nuclear device
would be wasted. The blast is radiated isotropically, only a small amount actually hits the
pusher-plate and does useful work. So they tried to figure out how to channel all the blast in the
desired direction. A nuclear shaped charge.
Propulsion Shaped Charge
Remember that in the vacuum of space, most of the energy of a nuclear warhead is in the form of
x-rays. The nuclear device is encased in a radiation case of x-ray opaque material (uranium) with

42. a hole in the top. This forces the x-rays to to exit only from the hole. Whereupon they run full tilt
into a large mass of beryllium oxide (channel filler).
The beryllium transforms the nuclear fury of x-rays into a nuclear fury of heat. Perched on top of
the beryllium is the propellant: a thick plate of tungsten. The nuclear fury of heat turns the
tungsten plate into a star-core-hot spindle-shaped-plume of ionized tungsten plasma. The x-ray
opaque material and the beryllium oxide also vaporize a few microseconds later, but that's OK,
their job is done.
The tungsten plasma jet hits square on the Orion drive pusher plate, said plate is designed to be
large enough to catch all of the plasma. With the reference design of nuclear pulse unit, the
plume is confined to a cone of about 22.5 degrees. About 85% of the nuclear device's energy is
directed into the desired direction, which I think you'd agree is a vast improvement over 1%.
Weapon Shaped Charge
About this time the representatives of the military (who were funding this project) noticed that if
you could make the plume a little faster and with a narrower cone, it would no longer be a
propulsion system component. It would be a nuclear directed energy weapon. Thus was
born Project Casaba-Howitzer.
Details are scarce since the project is still classified after all these years. Tungsten has an atomic
number (Z) of 74. When the tungsten plate is vaporized, the resulting plasma jet has a relatively
low velocity and diverges at a wide angle (22.5 degrees). Now, if you replace the tungsten with a
material with a low Z, the plasma jet will instead have a high velocity at a narrow angle ("high
velocity" meaning "a recognizable fraction of the speed of light"). The jet angle also grows
narrower as the thickness of the plate is reduced. This is undesirable for a propulsion system
component (because it will destroy the pusher plate), but just perfect for a weapon (because it
will destroy the enemy ship).
The report below suggests that the practical minimum half angle the jet can be focused to is 5.7°
(0.1 radians).
They would also be perfect as an anti-ballistic missile defence. One hit by a Casaba Howitzer
and a Soviet ICBM would be instantly vaporized. Which is why project Casaba-Howitzer's name
came up a few times in the 1983 Strategic Defense Initiative.
Casaba Howitzers fired from orbit at ground targets on Terra would be inefficient, which
is not the same as "does no damage." A nuclear warhead fired at a ground target would do far
more damage, but the Casaba Howitzer bolt is instantaneous, non-interceptable, and would still
do massive damage to an aircraft carrier.
Scott Lowther has done some research into a 1960's design for an Orion-drive battleship. It was
to be armed with naval gun turrets, minuteman missiles with city-killing 20 megatons warheads,

43. and Casaba-Howitzer weapons. It appears that the Casaba-Howitzer charges would be from
subkiloton to several kilotons in yield, be launched on pancake booster rockets until they were
far enough from the battleship to prevent damage (several hundred yards), whereupon they
would explode and skewer the hapless target with a spear of nuclear flame. The battleship would
probably carry a stockpile of Casaba-Howitzer weapons in the low hundreds.
Mr. Lowther estimates that each Casaba-Howitzer round would have a yield "up to a few
kilotons" and could deliver close to 50% of that energy in the spear of nuclear flame. Three
kiltons is 1.256 × 1013 joules, 50% of that is 6.276 × 1012 joules per bolt.
This is thirty-five times as powerful as a GBU-43/B Massive Ordnance Air Blast bomb, the
second most powerful non-nuclear weapon ever designed. Per bolt.
Get a copy of the report for more details, including a reconstruction of a Casaba-Howitzer
charge.
What is the mass and volume of a Casaba-Howitzer charge? Apparently this also is still
classified. I just got the lastest inside scoop from Scott Lowther. He estimates each Casaba
Howitzer charge is about 115 kg and 0.14 m3, with a probable yield of 5 kilotons. See details
below:
THE DEADLIEST CATCH

Conceptual Design by Scott Lowther

44. 
Conceptual Design by Scott Lowther
Mass Schedule
System
Mass
(kg)
Optics 9.1
Primary ACS 9.1
Secondary ACS 2.7
Communication 2.7
Warhead 90.7
TOTAL 114.3
The story is fictional, an alternate history novel. But the details about the Orion
nuclear pulse drive and the casaba howitzer are meticulously researched and
extrapolated where the details are classified.
Warhead has a length of 0.676 meters, infrared telescope has a length of 0.552 meters.
Length when folded, about 1.23 meters. It is mostly a cylinder with a diameter of 0.387
meters, but there are four bumps near the top of the warhead that increase the diameter
to 0.412 meters. I calculate the volume to be approximately 0.14 m3
.

45. Nuclear device yield is 5 kilotons. Weapon jet velocity is 280,000 meters per second,
containing a whopping 8,700 Ricks.
Blueprint legend:
The first generation of operational Casaba Howtizer units was first deployed in 1972
aboard the USSF Hornet. The units were composed of four primary assemblie… the
modified small Orion pulse unit, a high-thrust, short-burn solid rocket booster, a 13-inch
infrared telescope and a deployable communications module. All are stored and
launched as a 15.25" (0.412 m) diameter cylinder. During the short boost phase, the
freon fluid-injection TVC system directs the unit towards the target and roughly aims it
using internally stored data obtained from the warship at the moment of launch. After
booster separation the unit deploys the sensor and communication systems. A high-
thrust monopropellant thruster system aims the weapon to within half a degree of the
target. The infrared scope detects the target, using reflected laser light (projected from
the warship); the cold gas thruster perform final aiming. Weapons initiation is
commanded from the warship after confirmation of target lock.
From author's afterword:
Discussion of Casaba-Howitzer
The Casaba-Howitzer was a real concept: a modified pulse unit that fired a jet of
plasma. But instead of a jet of fairly dense plasma at a fairly wide angle, Casaba-
Howitzer was to fire a lower density jet at a much tighter angle in order to serve as a
weapon. Work continued well after the Orion program was terminated. And that, sadly,
is about the sum total of the publicly available information on Casaba-Howitzer.
Everything else about it is speculative. So, I speculated.
My first generation Casaba-Howitzer weapon is a modification of the pulse unit
designed for the small 10-meter Orion. Exactly how a tight “beam” of nuclear death was
to be generated, what sort of range could be expected… these are concepts about
which I simply cannot speculate. But other areas sort of fall into place on their own. Was
Casaba-Howitzer a weapon that would be fired from the ship, like a massive cannon?
Given that the yield for a small pulse unit was a good fraction of a kiloton, trying to
contain that energy in any sort of cannon-like object seems futile. So the pulse unit
would be fired in free space. And likely you’d want to fire it at some distance from the
ship. Therefore the pulse unit would need to be projected from the ship. This could be
done via either gun or rocket; I’ve chosen rocket. In this case, a fast-burning, high-thrust
booster similar to a Sprint motor, using Freon injection in the nozzle for thrust vectoring.
The rocket would burn for only a second or so, tossing the projectile some considerable
distance from the ship. After burnout, the projectile would unfold. I’ve given the projectile
a sizable telescope with an IR scanner and a communications system. The presumption
is that the weapon would be used to take out enemies at ranges of hundreds of

46. kilometers, so it would need precise aim. If it was hundreds of yards from the ship, the
only way to be sure of precise orientation with early 1970’s tech would be if the
projectile could see what it was aiming at. The projectile would be aided by a laser on
the warship; this would illuminate the target, making it stand out from the background,
shining as a bright point in the distance. Computer aiming would be needed; even with a
jet velocity of 2.8×107 cm/sec (~174 miles/sec) — slightly less than twice that of the
pulse unit — it will still take several seconds to hit a target. In that time the jet will have
radiated away much of its heat as well as spreading out some distance, so the target
will be hit with a shotgun blast of tiny particles. A thin cloud of dust moving at one tenth
of one percent the speed of light.
The weapon has three attitude control systems. The first is the thrust vector control
system on the booster; this is enough to get the unit within a few degrees of the target.
The second system is a hydrazine monoprop thruster system which, once the system is
properly deployed, quickly gets the weapon within a fraction of a degree of the target.
The third is a simple cold gas (helium) system that has very low but precise thrust, used
for getting the system precisely on target. Once the weapon has locked onto the target,
the command to fire is issued by the warship. The weapon is initially launched with the
telescope and radio communications system folded against the front of the system, but
you wouldn’t want “stuff” immediately in front of the beam, as that would disrupt the
blast.
The Casaba Howitzer yield is here given as 5 kilotons, about ten times the yield of a
comparable pulse unit. The pulse units were at the low end of what was feasible for
repeatable nukes; dialing one up to five kilotons would only be a matter of letting the
base nuke be what it wants to be, rather than intentionally throttling it.

47. 
My artwork, based on Scott Lowther's blueprints
The "Front Towards Enemy" is my little joke.
Runner-up joke was "Say Cheese And Wait For The Flash"

48. 
My artwork, based on Scott Lowther's blueprints

My artwork, based on Scott Lowther's blueprints
From PAX ORIONIS #2: "THE DEADLIEST CATCH, PART TWO" by Scott
Lowther (2018)
THE NUCLEAR SPEAR: CASABA HOWITZER
(ed note: In 2018 Matter Beam discovered errors in the original calculation. The figures
below have been updated)
The Casaba Howitzer is the result of research into reducing the spread of the particles
produced by a nuclear pulse unit. Make the cone narrow enough and it becomes a
destructive beam.

49. The original nuclear shaped charge design called for the use of a tungsten plate. The
particles that resulted from the detonation of a pulse unit would fit inside a cone with a
spread of 22.5°. The particles would be relatively slow (between 10 and 100km/s
depending on thrust requirements) and rather cool (14000°C in transit, 67000°C after
hitting the plate).
As noted before, using lighter elements, such as plastics or even hydrogen, in a thick
and narrow instead of wide and flat shape, you can achieve a very narrow cone and
very high particle velocities. A Science & Global Security report from 1990 used
polystyrene as the propellant material to produce a particle beam with a spread of 5.7°
and a velocity of 1000km/s.
Particle velocity is derived from the Root Mean Square equation. It can be written as
such:
 Particle velocity = (24939 * Temp / Mass) ^ 0.5
24939 is a constant equal to Boltzmann's constant (1.38*10-23) divided by unitary molar
mass in kg (1.66*10-27) times the degrees of freedom of motion (3). Temp is the nuclear
detonation's temperature in Kelvin, and Mass is the mass of the propellant used in
kg/mol.
For an atom bomb (108 K), uranium (238) will be ejected at 102km/s.
In a fusion reaction (109 K), deuterium (2) will be ejected at 3530km/s.
The difficulty is in transmitting this thermal energy to the propellant, and keeping the
particle cone focused.
In a propulsion pulse unit, it is not known how efficiently a nuclear shaped charge is
able to heat the propellant. Most sources cite a 85% of the device's energy being sent in
the desired direction. It is unknown also whether this is before or after some of the
propellant is accelerated in the wrong direction, and whether larger pulse units are more
efficient (higher propellant mass fraction). This is important as it would allow a thermos-
dynamic estimation of the particle velocity.
It would be reasonable to use a lower figure when calculating the amount of energy
delivered to the propellant. Scott Lowther gave a 50% figure for small fission charges.
An SDI nuclear weapons study, Project Prometheus, experimentally tested Casaba
Howitzer weapons using plastic propellants. It achieved 10% efficiency. A Princeton
University study from 1990 on third-generation nuclear weapons cited 5% instead, but
for fusion devices with ten times better beam focus.
Effectiveness