There are countless things that can and should be said about the much
discussed plan for the sustainment (not replacement, as is incorrectly said all
the time) of the Trident missile system.
Overall, there seem to be agreement on the fact that submarines remain the
best platforms for the deterrent, with no one questioning the long demonstrated
rationale of moving away from an Air Launched deterrent with fleets of
strategic bombers and tanker aircrafts. No one, unsurprisingly, is arguing for
a solution made up by silos on land. There’s a current that calls for outright
nuclear disarmament, but this option in my opinion is not even worth exploring,
and then there is the famous “review of the alternatives” sponsored by the
LibDems.
I thought I would write my own quick review, mostly technical, of the
possibilities of adopting an “alternative” and ideally cheaper submarine-based
deterrent.
In the past, I wrote a wider analysis and report about the Trident
situation, including a comparison of national Nuclear Doctrines, which shows,
for example, that France’s nuclear policy is one of the most aggressive ones,
while China’s official position is, at least for now, remarkably similar to the
UK’s one.
That earlier, large review remains valid, so it is worth a look into, here.
First of all, what exactly are we talking about?
There seems to be a quite widespread ignorance of what program the MOD is
currently trying to tackle. The heated debate over the nuclear deterrent has
contributed to bring politics all over the matter, making it confused and
painting a picture of the situation that is often unclear at best.
The nuclear deterrent is composed of these main components:
Trident II D5 is the missile/weapon system.
It is not going anywhere at least until 2042, when it -might- be replaced by a
new missile development, indicated, i don't know how reliably, with the name
Trident II E6. With the recent test launch from HMS Vigilant, the Trident
missile has logged in 143 consecutive succesfull, flawless launches. So it
makes sense to assume that, more than a replacement, the next missile will be a
technology refresh largely based on the already available material. In any
case, what the UK is wrestling with at the moment is NOT a replacement for the Trident
missile system.
For the UK, Trident II is a bargain, as it purchased the rights to 58
Trident missiles under the Polaris Sales Agreement (modified for Trident) from
a jointly maintained "pool" of missiles that arms both the british
and the US Atlantic SSBN fleets. These missiles are fitted with UK-built
warheads and are exchanged when requiring maintenance. Under the terms of the
agreement, the United States does not have any veto on the use of British
nuclear weapons. Some of the Trident missiles originally acquired have been
fired in test launches, so the Vanguard submarines have never (and will never)
have all of their tubes filled with missiles.
In fact, while the theoretical capacity of the four Vanguard-class
submarines is 64 missiles and 768 warheads (16 missiles for each submarine,
each missile carrying up to 12 warheads), only 58 missiles were leased and some
of these have been expended in test firings. The UK leases the missiles but
they are pooled with the Atlantic squadron of the USN Ohio SSBNs at King's Bay,
Georgia (previously the UK maintained its Polaris missiles in-country).
The nuclear warheads themselves are instead UK-made, from design to
assembly to maintenance to preserve the independence of the deterrent. This work is done at the Atomic Weapons
Establishment (AWE) in Aldermaston.
The nuclear warheads carried on Trident are also due to live on for
many more years, with a replacement not envisaged before “the late 2030s” and
possibly further onwards, out to 2042, after in 2010 the UK accessed technology
being used by the US to extend the life of their own warheads and increase
their accuracy to enable more effective targeting of hard and deeply buried
point targets.
The US warhead is the W-76-1, and the british one is presumably a national
development of said weapon.
It is anticipated that developing a new warhead when the current ones will
have reached the end of their safe and useful life will cost 2 or 3 billions.
As part of cooperation with France, the two countries are working together to
ensure the safety and effectiveness of their nuclear warheads: considerable
savings have been achieved by deciding that the complex computer simulations
needed to ensure the safety of the nuclear warheads (since live nuclear tests
are notoriously banned) will be carried out in France, at Valduc, near Dijon,
from 2015 onwards. A new, modern facility is being prepared for this, under the
name EPURE, specialized in the study of the complex
hydrodynamics connected to a nuclear explosion (solid materials behave like
liquids when subject to the extreme levels of pressure and shock of a nuclear
detonation). The british Atomic Weapon Establishment will take on the role of
developing new technology in exchange, with the creation of a Joint Technology Development Centre which will develop advanced instruments for EPURE itself. This has
relieved each country from the need to invest several more billions. The UK,
for example, would have had to invest billions in the Hydrus, a new
hydrodynamics test facility at AWE, that now will not be.
As a consequence of all these considerations, the expense for a warhead
replacement is out of the current planning horizon.
The Vanguard-class SSBN are what the current "Trident
replacement" is about. It is indeed a submarine replacement program,
better known as "Successor Submarine", or Successor SSBN. These four
huge vessels have spent at sea all their life, being hard worked to sustain the
Continuous At Sea Deterrence Posture. HMS Vanguard, the first in the class,
entered service in 1994, and the last SSBN of the type entered service in 2001:
in theory, by 2026 their operational life would be over.
Planned to live 25 years, they will now be life-extended by a considerable
number of years, with HMS Vanguard having its out of service date moved from
2019 to 2028, and the others following.
Further life-extension is deemed too expensive and risky to make sense.
Being only four in the class, these submarines have been worked harder than
their American Ohio counterpart, which will start being replaced into the
2030s.
The Successor Submarine is the program at hand. The idea is to build a new
class of SSBNs which will operate from the same shore infrastructure (keeping
any need for modifications and enhancements to an absolute minimum) and employ,
at least for the first part of their life, the very same missiles and warheads
now carried by the Vanguards.
The expenditure for new missiles and new warheads, if and when these will
be needed and procured, should be kept separate from the submarine part of the
deal, as it will be spread over decades into the future.
Successor Submarine – the current plan
At the moment, the plan is to build a fleet of 3 to 4 new SSBN submarines,
which will carry the Trident missiles. These vessels will be slightly larger
than the current Vanguards, but will use the same shore infrastructure. They
will carry 8 launch tubes, in two rows of four, down from 16 on the Vanguards. They
will use a new, safer nuclear reactor for power, the PWR3, which is partly
responsible from the size growth.
It is intended that the new SSBNs will largely derivate from the
Astute-class SSNs: in particular, the two classes will share the same control
systems, the same tactical torpedo system and the same sonar suite, making the
training of crews similar enough to enable easy transfers from SSN to SSBN and
back as necessary.
The new SSBNs will thus have a very potent battery of 6 torpedo tubes and
room for 38 torpedoes and Tomahawk missiles in addition to their nuclear
arsenal. They will also have a formidable sonar suite, possibly the best in the
world, and they will offer the benefit of great commonality with the attack
submarine fleet.
The Trident launch tubes module is being jointly developed with the US
Navy, to keep costs down as much as possible. This Common Missile Compartment
is composed of blocks of 4 launch tubes each, with the new US SSBN planned to
have 4 blocks, and the british one 2 blocks. Work on the CMC has been smoothly
going on since 23 December 2008, and the maturity of the design is now very
high.
It is intended that the overall size of the nuclear deterrent will shrink:
until the SDSR 2010, the Vanguards would go to sea for patrol carrying 48 nuclear
warheads, distributed unevenly on up to 16 missiles, offering some “flexibility”
in the Armageddon scenario, in theory making it possible to retaliate “proportionally”
with combinations of between 1 to 48 nukes.
The Successor will only carry eight missiles, and a total of 40 warheads.
As a consequence, the total stock of nuclear warheads will shrink from
around 225 to “no more than 180”, of which 120 (down from 160) would be
available for operational use at any one time.
The combination of Trident missiles, a fleet of 4 SSBN and a proportionate
stock of available warheads ensures that one submarine, loaded with live
missiles, is always at sea, 365 days a year, year after year. Once at sea, the
submarine is virtually undetectable and offers maximum survivability: so long
as CASD is maintained, no enemy is in the position of whipping out with a
pre-emptive strike the nuclear arsenal of the UK. Even if they hit and destroy
Faslane and the submarines in port, at least one and at times two submarines
will be somewhere out at sea, ready to retaliate in little more than 30
minutes: the time Trident takes to hit a target up to 10.000 km away. The ballistic
range of Trident means that a submarine hidden in safe waters can relatively
easily target anyone in the world to retaliate timely and assuredly.
For me, the Survivability and the Certainty of a nuclear retaliation option
are the two decisive factors: a minimum credible deterrent, which is what the
UK needs, must absolutely be:
-
Survivable: the enemy must not
have the easy option of whipping out the british nuclear deterrent with its own
first attack
-
Certain and Timely: the enemy
must be in no doubt that a nuclear attack will be met, 100% of the time, with
proportionate nuclear retaliation, from which the enemy must have no realistic
escape.
If the deterrent cannot meet
these two crucial requirements, it is useless. If the enemy can destroy the
arsenal at will or defend itself from the retaliation strike, the enemy will
not be deterred at all. If it is not Survivable and Credible, then it is better
not to devote money to it at all.
The current and future SSBN solution meets the above requirements.
The current Successor Submarine strategy:
-
Requires a new submarine class
to be designed and built, but no new warheads and no new missiles for the time
being
-
Makes best use of US
collaboration and support, cutting costs while protecting independence of the
deterrent
-
Ensures capability to continue
mounting a Continuous At Sea Deterrence
-
Does not impact negatively on
the availability of attack submarines for conventional Fleet roles
Alternatives?
Lengthened Astute with 4
launch tubes: one option that has been mooted is that to build
3 or four more Astutes, inserting an additional module aft of the fin
containing a single block of 4 Trident launch tubes.
Unfortunately, this solution is not at all easy and straightforward.
First of all, the current CMC block of four tubes in two rows of 2 sitting
side to side won’t fit the beam of an Astute submarine. So the development work
done this far would not be sufficient, as we’d have to design a module with the
four tubes sitting in a row, one after the other, making the submarine quite a
bit longer.
 |
| Workers stand proudly inside the launch tubes of a quad-pack block built as part of the CMC effort |
This is, in line of principle, not at all unfeasible: indeed, the
US Navy plans to do exactly this on its Virginia class SSNs of the Block V,
which have already been fitted with two large vertical tubes in the bow
starting with the Block III vessels currently being built. These two large
tubes, fitted with “six-shooters” frames holding each 6 Tomahawk cruise
missiles, have replaced a more complex and less flexible complex of 12 single VLS
tubes mounted on earlier submarines. The US Navy plans to develop, build and
install a “Virginia Payload Module” with 4 large tubes into the vessels of the
fifth production block. This Payload Module, with 4 tubes aligned to the
submarine’s centerline, comes with a pressure hull that is 34 feet in the beam
at the fore and aft extremities, going down to a 26-foot wasp-waist around the
tubes themselves: this is because space was needed outside of the pressure hull
to install the heavy, bulky mechanism of the hatches and additional ballast
tanks, plus some unallocated space. An outer, non-pressure hull wraps up and
completes the module, maintaining the Virginia’s hull profile and beam (34
feet). The length of the whole module is determined by the need to balance the
considerable additional weight made up by the launch tubes and related
machinery.
On the Astute, the arrangement would have to be pretty much the same, since
while the Astute has a larger beam (11.3 meters against 10+ for the Virginia)
it is still not enough to make another configuration viable.
 |
| A General Dynamics Electric Boats image, showing the Virginia Payload Module with its four large tubes, here fitted with a rack for 7 Tomahawk missiles each. Two further large-diameter tubes, even shorter and carrying only 6 Tomahawk each, are fitted, outside of the pressure hull, in the bow of the Virginia subs from the Block III vessels onwards. The VPM's four tubes offer greater flexibility than the bow ones as they can be accessed from inside the sub. The bow tubes, being outside of the pressure hull, cannot be accessed by the crew. |
But, since an option does exist, why is this not a viable alternative
Vanguard replacement for the Royal Navy?
For a pretty simple reason, which is the same main problem ruling out a
Virginia-based Ohio replacement: the launch tubes fitted to the SSN have the same diameter of those fitted
to the SSBN, but don’t have the same
length. The difference in sizes between SSN and SSBN are not casual: the
Trident missile is a big beast, and is 44 feet long (or tall, if you prefer,
since it sits vertically in the tubes).
In an Astute submarine, the launch tube would offer at most 36 feet of
useable length, so the Trident missile would suddenly need a whole new
replacement that the UK would have to fund on its own.
The Virginia Block 5 will use its 4 large tubes to carry modules with 7
Tomahawk each, increasing the cruise missile load on the SSN up to 40, counting
also the 2x 6 in the bow. Even more Tomahawk could be carried in place of
torpedoes, and the large-diameter tubes are seen as a mean to future-proof the
submarines, enabling them to employ, in the future, new missiles, unmanned
vehicles, special forces gear, and other kit.
The Virginia Block V, in fact, was immediately deemed unsuitable as an Ohio
replacement solution: the US Navy envisions the new vessel as a replacement for
the 4 Ohio submarines that were modified into SSGNs. The US Navy in fact is
aware that a boat as ambitious and expensive as an Ohio is not going to be
affordable in the future, and it has been deemed more effective to replace such
SSGNs with boats that have obviously far less firepower (a converted Ohio can
carry some 66 special forces operators and a load of Tomahawks that can reach
the amazing figure of 154 missiles) but that will be more numerous, and will
overall add more capability to the fleet for an advantageous pricetag.
The current Ohio SSGNs will be retired from service starting in 2026, so
the US Navy is obviously already at work over the Virginia Payload Module, with
the aim of starting the building of the first Virginia Block 5 in 2019.
It is probably not technically impossible to fit
Trident missiles into an Astute, but this would have a dramatic impact on
design and performances of the submarine, as it would be necessary to gain a
good 8 feet in height over the back of the submarine, and this would impact
weight, hydrodynamics, stealth when surfaced and, crucially, it would have a
very bad effect on acoustic, making the submarine a lot more noisy when
underwater, and thus much easier to detect, a problem typical of certain
Russian SSBNs, such as the Delta IV, which very evidently show such a hump
behind their conning tower.
 |
| Something like this would be the result of trying to fit Trident II missiles into an Astute hull. This solution would be relatively easy and cheap, but would ruin the submarine's performances, making it slower and louder underwater. |
The Americans, unsurprisingly, absolutely did not want
to walk this path with their replacement SSBN and with the Virginia Block V.
While technically feasible, it is a very bad solution
for a lot of reasons. The savings would be negligible, and the submarine coming
out of this solution would be, basically, a flawed design, using a solution
that everyone has abandoned because of its defects.
If we went with the shorter tubes and tried to design
a new ballistic missile to fit into said tube the costs would skyrocket, and
the UK might well not have the industrial capability to develop such a complex
ballistic weapon on its own, since there is no real previous experience to
build upon.
Arguably, the Astute SSNs should have been built with
large vertical tubes, but like with the Virginia Block V, these should not
stretch out of the carefully designed hull profile, and thus would be not be
Trident tubes.
 |
| The Virginia Block 3 bow in direct comparison with the bow arrangement on submarines of the earlier batches. Best thing is, these changes not only improved the sub, but cut costs of construction by a good few million dollars. |
An
Astute-with-tubes would be an excellent SSGN and potentially a good vector for
a cruise missile-based deterrent, at most.
But the problems connected to a nuclear-tipped cruise
missile are numerous and significant:
- The
nuclear-tipped Tomahawk is gone, so there is no easy option.
- Politically, a
new, british development of Tomahawk fitted with a nuclear warhead would be
inconceivable. The Tomahawk is one of the most precious,
effective and frequently used weapons in the US and UK arsenals, and the political
and operational cost of having every single Tomahawk launch possibly mistaken
for a nuclear attack is absolutely unacceptable.
-
Developing
from scratch a new missile, even one relatively conventional in design, would
be expensive, and would also require a new nuclear warhead to be designed. The
cost could balloon up immensely if, to counter the greater vulnerability of a
cruise missile compared to a ballistic one, the decision was taken to build a
stealth and/or hypersonic missile.
-
The cruise
missile would never be able to match the useful range of the Trident missile,
or its survivability. Shooting down a cruise missile is far easier than trying
to kill small warhead re-entering the atmosphere at Mach 25. The range limit
means that the current hiding places used by nuclear-armed submarines in the
Atlantic and Arctic oceans would be useless: from there, the submarine would be
unable to hit anything. What will the submarine do to retaliate against an
attack coming from far away, from an unexpected direction, via ballistic
missiles? The submarine will run towards a suitable launch area within range of
the target, to launch a retaliation days after the attack, risking to be sunk
by an enemy which will be aware of the cruise missile threat?
For a cruise missile to be an effective deterrent capable to hit
high-technology enemies (the only ones capable to start an attack requiring
nuclear response, arguably), the ability to get past layered air defence
systems is indispensable. It should also have thousands of miles of range to
enable the submarine to stay a safe distance away from the enemy while it
launches the missiles.
And there are only so many routes a low-flying cruise missile can use,
making it relatively simply for the enemy to prepare its air defence batteries
and, even worse, maritime patrol aircrafts and warships patrolling the possible
launch areas.
I think the cruise missile option does not meet the requisites to be
considered a Credible deterrent.
Anyway, the Astute-with-tubes solution offers:
-
Negligible
savings, assuming that an “hump” solution is adopted to retain Trident
missiles. The new submarines will probably cost significantly less, but the
design challenge is still significant, and new subs would still be required. Worse
still, the new vessels would have their performance depleted or compromised in
terms of speed and stealthness. The number of missiles and warheads could
shrink further, contributing to the savings, but the reduced number of missiles
also reduces the flexibility and lethality of the deterrent. If the firepower
shrinks too much and during the life of the deterrent anti-ballistic technology
progresses further, an enemy might become realistically certain of its ability
to shoot down all the re-entry warheads, nullifying the effect of the
deterrent.
-
If the shorter
tubes are adopted, and the decision is taken to drop Trident and develop a new
ballistic missile, costs rise dramatically. It probably would end up costing
more than going onwards with the current plan.
-
If the cruise
missile solution is adopted, a new cruise-missile and a new warhead will need
to be developed and produced, eroding the possibility of achieving any real saving.
All the limits of the cruise missile option will have to be accepted if this
road is chosen.
 |
| Flexibility: you can fit a multiple Tomahawk launcher assembly into a Trident tube and still have a lot of space to spare in the bottom half of the tube. Room for future developments and for new uses. |
Nuclear-tipped
cruise missiles fired from existing, modified Astute subs: the key word here is “modified”. How much
modifications will be required to enable the safe carriage of nuclear-tipped
cruise missiles in the torpedo magazine? How would said modifications impact
the submarine’s performance in its other roles?
This option offers the promise of great savings, even
if a new missile and warhead would need to be developed, and the Astute
submarines would need modifications for their safe stowage and use. I don’t
think, in fact, that it would be accepted to just embark nuclear weapons
without proper procedures and equipment being developed.
This option would very likely negatively impact the
attack submarine fleet. It would become politically harder to send the Astutes
around on their conventional missions, and it wouldn’t be surprising to see
nations denying their ports to the visit of an Astute. It could be a real
problem in the Persian Gulf.
It is pretty much certain that only one Astute at a
time would carry nuclear-tipped missiles, and this one submarine would be
hiding like an SSBN, deep into the ocean. It would mean, effectively, dramatically reducing the availability of
Astute submarines for their normal missions, and this would have a terribly
negative effect on a fleet that is already too small to meet its many
commitments. Building at least a couple more Astutes would be absolutely
indispensable, but this would further reduce the savings, and there would still
be plenty of limits and issues.
Basing the nuclear missiles on surface ships, such as
Type 45s, would be even worse, both politically and operationally. And it would
also further erode the survivability of the deterrent.
Cruise
missiles in a cupboard: this is the
most demented proposal after the unrealistic plan for land-based missile silos.
Hiding an entire nuclear arsenal in a bunker in the
british countryside will present countless challenges, and I absolutely cannot
agree with a course of action of this kind, which would put future british
governments in the difficult position of having to order the Navy to open the
bunker, load a submarine with missiles and set sail “in times of heightened
tension”.
Taking the decision to bring the nukes out of stowage
would an hugely impressive move, but it might very easily impress in the wrong
way. It could cause a sudden worsening of the situation, instead of bringing
back the calm.
There is a big difference between routine patrols
going on at sea from well over 40 years and the sudden show of nuclear might
connected with the decision to blow the dust off the nukes.
The submarine routinely out at sea is aiming its
missiles at everyone, yet at no one at the same time. It is there, somewhere,
lurking in the deep, away from the eyes, but always present. It causes
prudence, and it cannot be contested.
But the images, shown on television, of long stored
nuclear missiles being brought out of the bunker and loaded on the submarine
would send a sudden, harsh message which is unlikely to be of real help,
because it changes from a routine to an exceptional event, a signal of sudden,
dramatic escalation.
Any government would find it hard to take such an
important decision.
Worse, this kind of deterrent is not responsive and is
not survivable. If, for any reason, the nukes were still in stowage when the
first ballistic missile was launched, there wouldn’t be enough time to do
anything. The warheads could be raining from the sky in as little as half an
hour, and the first nuclear strikes would inexorably target the arsenal.
For me, this option absolutely isn’t credible.
Indeed, in my opinion there is no realistic
alternative to a new class of SSBNs. While there are technically different
approaches that could be selected, they all ensure a series of problems or
degradations in capability, while delivering only rather vague promises of
savings.
