Spain is working on trajectory correction fuse in the 155mm shell

The Spanish General Directorate of Armament and Material [DGAM] has bestowed upon Escribano Mechanical & Engineering a project worth 16.9 million euros. The project involves the creation of a trajectory correction fuse that can efficiently function with the 155 mm ER02A1BB projectile, a type of ammunition typically used by Army howitzers. 

Ukrainian officer: My M109 Paladin SPH has an accuracy error of 70m
Photo credit: US DoD

The initiative, referred to as Estra, isn’t solely about development. It also includes amalgamation and qualification tests. The enhanced system will seamlessly merge the guidance kit from Escribano with the chrono-electronic fuse, a product from Rheinmetall Expal Munitions. Rheinmetall will join hands as a subcontractor and technological ally on the project. 

This contract is a four-year commitment, with the primary aim to fortify the 155mm ER02A1 extended range projectile’s accuracy. The finalized, integrated setup will function as a testament to the harmonious collaboration of the Escribano guidance kit’s hardware and software components with the fuse’s features offered by Rheinmetall Expal Munitions. 

Escribano points out that the contract is key to equipping the Armed Forces with strategically crucial capabilities like guided munitions. Given the geopolitically volatile climate, this modification is nothing short of essential.

30 meters CEP

The company states that the ER02A1 projectiles, equipped with this novel guidance system, will have the ability to self-correct their trajectory, guaranteeing a remarkably low margin of error [CEP] of fewer than 30 meters. 

“Following the insertion of the fuse into the projectile, along with the necessary dimensional, aerodynamic, and functional compatibility tests, this innovative fuse will be deemed qualified for application in 155mm ER02A1BB projectiles. Subsequently, a thorough operational validation process will commence, facilitating the evaluation of its benefits by the FAS,” Evidently, the Madrid-based enterprise goes into great detail on the process. 

Expal and Escribano initially inked an agreement a year ago to stimulate the progress of a fuse possessing these unique features for 155 mm ammunition. The fiscal planning for the Estra program was ratified in September by the Council of Ministers. 

The Defense subsequently clarified that “the Armed Forces necessitate an efficient medium to be employed on instances where the dispersion of ammunition needs to be curtailed, to minimize collateral damage.” For the Army, the paramount goal is to mitigate the dispersion which restricts the use of extended-range ammunition in situations where friendly forces are in proximity, unacceptable collateral damage may ensue, or the targets to be subdued are demarcated within constrained dimensions.

How it works?

The guidance kit consists of various components, including an inertial navigation system, a global positioning system [GPS], and a control unit. These components work together to continuously monitor the shell’s position, velocity, and orientation during flight.

The tenet principle behind the correction of the artillery shell’s trajectory is based on the concept of guidance and control. The guidance system uses information from the inertial navigation system and GPS to determine the desired trajectory for the shell. It compares this desired trajectory with the actual trajectory of the shell and calculates the necessary adjustments to bring the shell back on track.

Once the necessary adjustments are calculated, the guidance system sends commands to the control unit, which in turn adjusts the flight control surfaces of the shell. These adjustments can include changes in the shell’s orientation, such as pitch, yaw, and roll, as well as changes in its velocity. 

The chrono-electronic detonator plays a crucial role in the correction of the shell’s trajectory. It is responsible for initiating the detonation of the shell at the precise moment when it reaches the target. The guidance system takes into account the time required for the shell to reach the target and calculates the optimal detonation time.


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