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The Evolved Sea Sparrow (ESSM) is a good, low-cost missile used for local air defense by the U.S. Navy as well as several allies.  The short range of the missile limits its use as anything other than local defense missile.  The short range could be rectified for low cost via the addition of an additional booster, similar to what is done with other surface to air missiles in the Navy’s inventory such as the SM-1, SM-2, and SM-6, and dramatically increase the usefulness of the missiles and the platforms that employ them.

The ESSM has several key attributes and incorporates some of the latest missile design features.  The missile has an extremely high speed and is highly maneuverable due to use of thrust vector controlling vanes in the exhaust.  This combination is useful against difficult targets such as aircraft and sea-skimming supersonic anti-ship missiles. The latest version, the ESSM Block II, incorporates a dual-mode X-band seeker adapted from the AMRAAM missile while retaining compatibility with the different radars currently in use by both the U.S. Navy and allied navies.  The new active radar seeker will allow engagement without the use of the launch ship’s target illumination radars.  This seeker allows for the potential for over the horizon engagements and a limited anti-ballistic missile role.  Even with these advanced features, the ESSM is relatively affordable at around $1.1 million dollars according to recently published figures.  This affordability allows for the U.S. Navy and allied navies to acquire the ESSM in relatively large numbers.

Another key advantage of the ESSM is the compact size of the missile.  According to public figures, the EESM is 10 inches in diameter, is 12 feet long and weighs around 620 pounds.  This compact size allows for the ESSM to be quad packed into a single VLS cell.  That means that a ship can carry four capable missiles in the space normally occupied by a single missile.  For large surface combatants like the Burke Class, that allows for more offensive weapons to be carried such as Tomahawks or the forthcoming LRASM while still retaining a potent number of SAMs for self-defense.  For smaller vessels with a limited number of VLS cells, such as European Frigates and the U.S. Navy’s forthcoming FFG(X), this attribute is critical for allowing a multiple mission role.  On a ship with 32 VLS cells, a ship can be armed with 8 ASROC missiles for the ASW role, eight offensive anti-ship missiles for the ASuW role, and 64 ESSM for air defense.  That is a powerful loadout that markedly increases the combat power of a smaller platform. 

The ESSM is not just compact in width, it is also a relatively short missile.  In strike length VLS employed by U.S. Navy ships and most allied navies, the depth of the VLS cells is 303 inches (25 feet) which means that the ESSM only occupies around half of the length available in the usual VLS cell.  That means that a booster can be attached to the ESSM to increase its range and altitude by a sizeable margin which would dramatically improve the performance of the ESSM against high energy targets such as ballistic missiles and hypersonic threats and increase the coverage area against conventional airborne targets.  The addition of a booster would be a relatively inexpensive improvement that would help to maximize the effectiveness of the new ESSM Block II active seeker.

Adding boosters to existing SAMs to extend range is a widespread tactic.  The United States has been doing it for decades, starting with the SM-1ER, and most recently with the SM-6.  The European ASTER series has two missiles, the ASTER 15 and Aster 30, which share a common missile with or without an extended booster to boost the range for the Aster 30.

The current rocket motor in the ESSM is the Mk 134, which is 79 inches long and weighs 370 pounds.  If the current rocket motor were to be added as a first stage booster the overall length of the resulting missile would still easily fit into the current Mk 41 VLS cells.  If the thrust profile of the current MK 143a motor would not work as an effective second stage, i.e., if the initial boost for ejecting the missile from the VLS cell made it unusable in flight, there are other existing rocket motors with the correct approximate size that could be substituted.  For example, the rocket motor from the HARM missile is the same diameter, approximately the same length and is a dual thrust motor that would usable in the ESSM-ER as a second stage as the flight profile would be similar to an air-launched missile.

It is difficult to determine how much range and altitude and additional stage would provide the ESSM.  From public sources, it appears that the maximum effective range of the ESSM is in excess of 50 km, perhaps as long as 80 km (48 statute miles).  With a rule of thumb 40-60% increase for doubling fuel, the resulting range would be around 130 km (78 statute miles).  That results in a coverage area that is approximately tripled over the base ESSM Block II.  A similar increase in engagement altitude would result in missile capable of engaging shorter ranged ballistic missile threats targeting the launching ships or ships close to the launching ship. 

The resulting ESSM-ER would be a perfect weapon for frigates, both those of our allies and the forthcoming FFG(X) class.  Even with the limited number VLS cells on these platforms, the ESSM-ER can be mixed with ESSM Block II missiles to provide credible self-defense against swarm attacks by providing a large number of missiles with the range to provide multiple interception opportunities of incoming threats.  The extended capabilities of the ESSM-ER against emerging highly energetic targets would make these platforms much more useful in the high-end fight against foes employing hypersonic and ballistic targets.  The extended range would also allow these frigates to provide area air defense rather than simply local area defense in distributed fleet operation and convey escort roles. 

The ESSM-ER would also be extremely useful for both the Burke and Ticonderoga classes.  If used in conjunction with the SM-6 to replace the SM-2, a large number of VLS cells could be freed up for more offensive missiles or to simply dramatically increase the number of defensive missiles.  An ESSM-ER also allows for more flexibility to engage targets, instead of expending valuable SM-6 missiles on every incoming target, an ESSM-ER would allow for a tiered approach to engaging inbound targets.

With these advantages, it is clear that the ten member countries of the ESSM Development Consortium should actively pursue this inexpensive upgrade to the current ESSM Block II missile.

Jason Blackstone is currently an attorney in private practice related to patents and technical issues.  He obtained an undergraduate degree from Texas A&M University in both Physics and Journalism and a focus on strategic issues and foreign affairs, and a law degree from Harvard Law School.

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