Saab further develops its knowledge in warhead technology

One of the
reasons for which Saab acquired what was then RUAG Warheads back in 2007 was
linked to a weapon that is currently on newspapers’ front pages, the NLAW (Next
generation Light Anti-tank Weapon). Its shaped charge warhead, which is
detonated downwards when the missile overflies its target in the OTA (Overfly
Top Attack) mode, was designed, developed and manufactured in Thun, some 25 km
south-west of Bern, the Helvetic Confederation capital. Within Saab´s Business Unit Ground
Combat there is the department SBDS (Saab Bofors Dynamics Switzerland Ltd). SBDS in short, has since then been
integrated into Saab, which allows it to exploit synergies within the Swedish
group’s research and technology laboratories. In a rapidly changing world, the
company’s approach to warhead development allows it to quickly adapt its
designs to customers’ requirements thanks to a set of evolving and increasing
of technologies that constitute the building blocks on which new designs are
based.

“We
considered multipurpose warheads to become the priority, however due to the
current situation the focus is shifting to antitank at present,” Christopher
Leitner, Head of Marketing and Sales at Saab Bofors Dynamics Switzerland tells
EDR On-Line. Antitank warheads have been the bread and butter for a long time
for the company, however this does not mean that Saab will rule out the
multipurpose theme, as it is currently developing lightweight warheads of this
type i.e. for loitering munitions or other weight sensitive applications.

At Saab
products can be divided by the type of target set, such as: anti-tank,
anti-air, anti-bunker or multirole. For cost / performance, there are state of
the art warheads at a medium price range for unguided shoulder launched
systems, and high-end warheads that include the latest technology destined for
top-tier missile systems in the anti-tank as well as in the air defence fields.

The
Thun-based company is providing its warheads to numerous OEMs; due to the
reduced numbers of systems produced, some top-tier missiles manufacturers have
outsourced their warhead production capability, hence these are now designed
and manufactured by a small community of companies Saab is the leading one in
Europe for small calibre systems, up to 3,500 mm diameter. Starting from
antitank systems, here the shaped charge remains the dominant player. One of
the key parameters is the penetration capability versus the diameter of the
main hollow charge, known as CD. In the past the CD 10 limit (penetration 10
times the charge diameter) seemed the very limit, but this has already been
overcome, Saab’s warhead developed for MBDA’s Milan ER in the early 2000s being
around CD 12. “The trend is to go for CD 15,” Christopher Leitner says.
Reaching that limit would provide a flexibility that will allow increasing
penetration while maintaining or even reducing weight, eventually adding
fragmentation elements, hence giving birth to a missile that can deal with
different targets; having in service a single missile that covers all missions
in a certain envelope would definitely reduce the logistic footprint and the
training, therefore cost of ownership. New materiel and new explosives are
definitely part of the CD increase. Today all missiles warheads are produced
following Insensitive Munition (IM) criteria, the key element being IM
explosive; this is not the case for mortar bombs, a considerable market share
still requiring non-IM ammunition loaded with COMP B or TNT (Trinitrotoluene)
even in Western Europe.

IM
explosive has inherently less energetic density, as part of it is made of
non-explosive materiel, that provides its insensitive properties. “One of the
most used IM explosives is the PBXW-11 of which 96% is made of HMX with only 4%
of non-energetic materiel, and it is quite easy to compensate that small energy
loss by optimising the warhead design,” Christian Herren, the company Director
Development and Quality tells EDR On-Line. Fully accepted in most European
countries, except in Germany where higher insensitive qualities are required by
the Bundeswehr, the PBXW-11 is at the base of most Saab warheads, such as that
of the 5^th generation MMP developed by MBDA. “We have proven that
using that explosive we can reach CD 11-12 by improving the warhead design, and
we are pushing further.” However when some nations, or some services, mostly
navies, need higher IM properties, things change. To reach this objective only
86-87% of the fill is made of energetic materiel, and optimising the design
allows to recover around 10% of the loss, hence we only have a 5-7% reduction
in performance,” Christian Herren says.

Knowing
Christian Herren’s knowledge of chemistry and more specifically in explosives,
EDR On-Line asked him to share some considerations on developments in the
explosive field. “I see two trends in that field. The first one is by research
institutes that are looking for new formulas for explosives but there we are
mostly at the end of the line. There are of course molecules that can have an
impact on penetration performances, but in terms of a few percent, and some of
those substances cost thousands of Euros per kilogram, so they will never be
used in mass series production. They may be employed only for very specific
uses, i.e. nuclear devices. Currently what we have is PBXW-11 and PBXW-17, and
this is what we have to work with,” he states. “There are however other things
we can do, such as better understanding the complex physical chemistry which is
behind those explosives.

We started
to simulate that in a quantum mechanical approach and that gives a lot of
surprises and possibilities that in perspective will allow making the
production process cheaper and more efficient. As an example, when using
isostatic pressing, which is currently the standard production process for
high-end warheads, one of the big costs comes from the loss of explosive when
machining the explosive. We are therefore working hardly to understand how we
could use the material in a more efficient way and maybe how to recycle the
scrap material, which would in the end make the warhead cheaper.”

Another
line Christian Herren sees becoming increasingly adopted internationally is
that of replacing non-IM explosives such as TNT or COMP B, with explosives that
include NTO (Nitrotriazolone) and that will be much better in terms of IM
properties but not significantly more expensive. As previously stated, cost led
many nations to stick to non-IM rounds in certain categories, with these new
explosives able to bridge the gap for mass production rounds.

A key
player in the optimisation process is definitely simulation; “we are using
neuronal networks, and we are working massively on artificial intelligence that
helps us in designing the liner profile,” Christopher Leitner explains. Some
profiles are impossible to be produced, while other can become reality, and
usually they are almost similar to those designed by Saab’s scientists. To
penetrate the main armour of a Main Battle Tank (MBT) the jet generated by the
shaped charge must first of all reach it. To do so, something else must take
care of the Explosive Reactive Armour (ERA) that nowadays is installed on most
MBTs. “We developed different technologies able to do that, one in a detonating
way and two in a non-detonating way, in which you go through the ERA without
exploding it. This can be done in an energetic or in a kinetic way,” Mr.
Leitner tells EDR On-Line. The advantage non-detonating solutions will have is
to avoid creating major turmoil in front of the main charge. No details were
provided on how the non-detonating energetic solution works, but it is based
apparently on a shaped charge. As for the kinetic solution, this very much
resembles the Modular Explosive Penetrator (MEP)
developed in Thun when the company was still RUAG Warheads, and at that time
used in an RPG prototype aimed at penetrating sandbags and walls. The kinetic
solution maintains the MEP conical forward shape, with its surface treatment
remaining undisclosed. Moreover, it should also maintain some capabilities in
terms of wall penetration, which leads to a potentially multipurpose solution.

Modularity
is the keyword in Thun, and EDR On-Line was shown the scheme of a multipurpose
solution that includes a series of elements designed to neutralise ERA and then
the main armour, while maintaining also a multirole function. Before firing,
the operator can select the mode best suited for the target, which adds
considerable flexibility to the missile. All technologies involved are at TRL9.

And this brings us to the fragment generation, which added to antitank capabilities allows a dedicated missile to transform into a multipurpose one. Some of those are well known and have been in use for some time, such as MAPAM (Mortar Anti Personnel Anti Material) used in mortar rounds, and Skjoll, which comes in the form of a belt added outside the warhead generating fragments with adaptable energy and adaptable spray angle, able to deal with soft targets. It is based on very small diameter tungsten balls, with adaptation to customer needs being obtained by modifying the wave shape and balls materiel. These two technologies have been patented and are already in use in some of the warheads provided by Saab to its customers. The third fragment technology patented by SBDS is named Thor, and is a further development of the MAPAM that features multi-materiel and multi-geometry characteristics.

One more
patent is part of the SBDS technology portfolio, although this one is not yet
available at production level. Named ExploStrain, it is based on multiple
initiation points; using smart fuses available on the market, it is possible to
initiate the explosive in a way to concentrate fragments on one side at an
angle, increasing by 40% the warhead effectiveness. Currently considered at TRL
4-5, it would allow to either increase effectiveness or reduce the warhead
weight while maintaining the same effectiveness of a conventional one. The
ExploStrain technology is considered particularly suitable for air defence
missiles, as it will allow triggering the warhead in the best relative position
to the target, orienting the majority of the fragments towards the intercepted
airframe. “It is relatively simple as many missile seekers provide not only the
relative special position of the target relative to the missile but also the
rotation of the latter,” Christian Herren says.

Concentrating
fragments is also the aim of a still unnamed technology that exploits two
initiation points. When the shock wave is the outcome of the detonation initiated
in a single point, it pushes forward fragments within a cone of about 7°, which
at some distance would mean a lesser fragment density hence a loss of
performance. Christian Herren explains to EDR On-Line. “With our technology,
detonating the explosive in two different points allows focusing the fragments
which in a missile aimed at aerial targets can increase effectiveness by 30%,”
he adds. 

However,
fragments concentration can be also obtained with other means than working on
initiating points. “Diffgeo is the acronym for differential geometry, and it is
based on mathematical calculation that allows optimising shrapnel focusing,
exploiting only the geometrical shape of the fragmenting surface,” So this
would not be the typical cylinder but a warhead surface optimised to build a
focus line. This is a system that Christian Herren considers simpler that the
dual-point initiation one, adding that Saab has already produced and tested
some systems based on that technology.

One technology that goes together with dual-point initiation is Diabolo shape as it is a symmetric shape, but by combining the initiation technology with the geometry it can reach a very high concentration of fragments. “This is used to defeat hard aerial target samples, such as those considered by various customers that retain heavy maraging steel tubes that have to be cut,” explains Herren, underlining that Diabolo shape is the main candidate for future air defence or air-to-air missiles warheads under development.

As for
Blast Shield, this is an enhanced blast solution that blends into a
multipurpose warhead and it is used when the main effect required is more a
pressure wave than fragments; used in combination with ExploStrain, it is
possible to focus the blast in the same way the latter does when coupled to a
fragment generation technology.

However, in
Thun scientists and engineers are not exploiting those technologies only to
allow increasing warheads effectiveness. Deepening their knowledge on the
intimate mechanisms of a warhead also allows them to better understand which
are the areas where extreme precision is required, and which are those where a
lesser accuracy has minimal influence on performance. “At CD 14-15 charges, 40%
of the cost will be purely linked to the quality level of manufacturing, hence
this better understanding of warheads mechanisms allows us to reduce cost by
15-20% therefore maintaining an excellent performance-to-price ratio,”
Christopher Leitner underlines.

Beside
missiles and mortar ammunition, which currently represent the great majority of
the SBDS business, the warhead-wing of Saab is looking to new applications such
as to Loitering Munitions (LM) or Unmanned Ground Vehicles (UGV) domains.
Especially for LMs, the weight issue is a critical factor and, until now, most
such systems have been fitted with existing warheads that were not optimised
for such use. SBDS is looking at two main market areas, Europe and North
America, where many nations in those regions have adopted LMs in their
inventories. However, this might change drastically in the coming 5-10 years.
When numbers increase, companies producing LMs will probably decide to invest
in warheads capable of dealing with most types of targets, which are one of
Saab specialties, and which would leverage the technological research done to
now.

According to Saab, the LM business will probably have a more unified approach compared to the purpose-made warheads for missiles. As for UGVs, the aim is to create effectors that might range from lethal to less-than-lethal solutions, which might even extend in the firefighting domain thereby avoiding putting human beings in hazardous situations.

Images and photos courtesy Saab

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