Like unleashing a bulldog: 4 good reasons to buy SM-6 missiles
The politicians knew well when they agreed on the Defence Agreement 2018–2023 that the purchase of SM-2 missiles for Danish frigates was not sufficient to make NATO happy.
If Danish frigates are to meet NATO’s goal for a strengthened maritime air defence, we will need to purchase completely new missiles.
For the same reason, it was also decided to commence preparatory work for acquiring SM-6 missiles.
Therefore, the SM-6 is what the Royal Danish Navy and defence experts will be looking for in a new Defence Agreement, because it would truly bring our defence up to a completely different level.
At the end of 2024, the new SM-2 missiles will be delivered. According to the documents from the Pentagon’s Defense Security Cooperation Agency, these are 46 SM-2 Block IIIA missiles. The Danish Defence states that DKK 1 billion has been set aside for procurement.
If Denmark is to buy SM-6 missiles, the costs will be significantly higher. The unit price per missile is 10 times higher—approximately DKK 33 million. And the replacement of the frigates’ radar system will also be costly.
Here are four reasons why the SM-6 missile is a far better air defence system than its little sister, the SM-2:
1. Active seeker
The fact that the SM-6 missile, unlike the SM-2, has its own active seeker is of crucial importance.
“I like to say that the SM-6 missile is the equivalent of letting a bulldog loose. It keeps chasing its target,” says Hans Peter Michaelsen, military analyst with 41 years of experience working in the Danish Defence.
The missile comes in several versions, but is known for its ability to stick to the target even if it zigzags or quickly accelerates. Its active seeker also means that the frigates can have even more missiles in the air at the same time, as they are not limited by the ship’s radar in the flight phase.
2. Able to shoot down ballistic missiles
The war in Ukraine has underlined that ballistic missiles have become a regular part of modern warfare. Ballistic missiles differ from cruise missiles in that they move much faster and typically achieve speeds of 3,000 km/h on impact, but up to 25,000 km/h in the flight phase. While cruise missiles follow a straight trajectory, ballistic missiles follow a curved (ballistic) trajectory that in some cases takes them up out of the atmosphere and back down.
The speed of ballistic missiles makes them difficult to hit, but the SM-6 missile, with its speed that is 3.5 times the speed of sound—and a powerful booster in the boost phase—can shoot down ballistic missiles on their way down through the atmosphere. This also applies to hypersonic missiles.
3. Works side by side with fighter jets
SM-6 missiles also open up the possibility of using the Danish F-35 fighter jets to identify far-away targets that the frigates’ radar cannot detect. The U.S. Navy has shown several years ago that they can use the F-35’s targeting information to launch missiles from ships.
4. Long range attacks
It is not only air defence that the SM-6 can be used for. The missile can provide a quick helping hand to the frigates’ current, old Harpoon missiles.
The old missiles fly at subsonic speeds, so Mach 3.5 is a huge upgrade, even if the SM-6 does not carry a large warhead.
The missile can also hit land targets up to 400 kilometres away, which is about twice as far as the Harpoon.
Thus, Denmark can show that it has learned from the experience of 1864, when the Prussian forces bombarded us from two kilometres away with their breechloading firearms—and we had nothing that could reach them.
Expensive missiles require new radars
However, an SM-6 missile system will require a new radar system on our frigates.
The SM-6 works on the S-band, unlike the frigates’ current target tracking radar.
Another problem today is that the frigates have rotating radars that risk detecting incoming missiles too late and have difficulty tracking several missiles at the same time.
Therefore, other radars will be needed, such as AESA, stationary 4-sided phased array radar familiar from Aegis guided vessels and Norwegian Fridtjof Nansen-class frigates.
Downsides of SM-2
The SM-2 missiles that the Royal Danish Navy will soon receive have serious shortcomings against the new threat of ballistic missiles, as well as fighter jet and helicopter diversionary manoeuvres.
The missile is semi-active, which means that it must be constantly guided towards its target by the frigate’s fire-control radar (APAR).
It can therefore only hit targets that are visible to the radar. If the radar loses its “lock” on the target, it causes problems for the missile, and several modern missiles, fighter jets, and helicopters can exploit this to avoid the missile.
A further problem is that the enemy is smart enough to know that their aircraft or missiles must attack a Danish frigate by flying as close to the surface of the sea as possible—because that way they stay hidden below the horizon for as long as possible, and that minimizes the frigates’ actual defence range to a few kilometres.
Finally, there is the problem that the frigates’ Thales multifunction radar, including the primary SMART-L sensor, is far too slow to detect incoming missiles.
First, the SMART-L sensor must detect the missile, then it must alert the APAR radar, which must lock onto the target, and only then can the SM-2 missiles be launched. Valuable seconds can be lost because the SMART-L sensor is a rotating device:
“It’s a problem if the missile appears when the sensor is facing away from it. And in practice, it’s close to impossible for a frigate to shoot down a ballistic missile that is detected 120 nautical miles away,” says Sune Hansen, commanding officer at the Danish Defence Command, who has also worked with the Royal Danish Defence College and taught at the Centre for Maritime Operations.
“The radar system the frigates have today is simply not sustainable anymore. If we are to be able to see and shoot down modern missiles, then we need new sensors—and I am sure this will be taken into account in the new Defence Agreement,” he says.
