Since mid-November, the Houthis have been launching attacks against shipping in the Red Sea. The US sent a number of AEGIS destroyers to help protect international shipping, performing the dual role of intercepting Houthi drones and missiles and coming to the aid of distressed commercial ships.
The British also sent one of its best ships, the HMS Diamond. However, something changed to cause the US and the UK to actually strike Houthi military sites in retaliation.
Serious doubts arose on both the British and US sides that they were not equipped to deal with swarms of Houthi UAVs and missiles. On January 10, US and British forces shot down 21 drones and missiles. British Defense Secretary Grant Shapps said that doing this was unsustainable. What did he mean?
There are two answers to the question of why the situation with the Houthis was going out of control. The first answer relates to the number of missiles aboard a ship. US ships are relying on SM-2 missiles, part of the AEGIS system.
One expert estimates the number available as follows:
“The [AEGIS] destroyers have a complement of 96 VLS cells, while the [Ticonderoga class] cruisers have 122…. However, they need to fit a mixture of weaponry in those cells so they can’t all be used for air defense.
This weaponry includes the ESSM (quad packed into a single cell), the SM-2 (and its newer counterpart the SM-6), Tomahawk cruise missiles, ASROC anti-submarine missile(s) and SM-3 anti-ballistic missile(s).
The exact ratio of these weapons is largely dependent on the mission and the possible threats faced. However, at least 200 ESSM and another 100 or so SM-2 or SM-6 seems like a fair guess. Maybe a bit more.”
In short, each of the AEGIS has around 100 missiles. The British Sea Viper is the main air defense system the HMS Diamond relied on to fire at Houthi drones and missiles.
“Type 45 destroyers, also known as Daring-class destroyers, are specifically designed around the Sea Viper (PAAMS) air defense system. Each Type 45 destroyer is equipped with a 48-cell A50 Sylver Vertical Launching System. This system is designed to accommodate a mix of up to 48 Aster 15 and Aster 30 missiles,” the expert said.
Neither the US nor the British ships can be reprovisioned at sea, so they have a limited ability to “stay in the fight” if it continues for any length of time.
As the January 10 Houthi attack demonstrated, the Houthis were increasing the number of daily attacks. How large an arsenal the Houthis had, therefore, was challenging US and British defense capabilities.
Missile defenses are very expensive. Each SM-2 missile costs US$2.1 million each. Sea Viper, which can either be an Aster 15 or Aster 30, costs either 1 million to 2 million pounds per shot. ($1.25 million to $2.5 million).
Nor does this take into account the challenge of replacing these missiles once expended. It not only will be more expensive but could take years of production time.
This leads to the second answer: what happened that was different than before? There are three possibilities.
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