In public, military-political leadership of Ukraine constantly pushes forward the request to the United States to finally provide operational-tactical ATACMS missiles to the Armed Forces of Ukraine. These missiles can be launched from an M142 HIMARS or M270, and have a firing range of up to 300 km.
Such missiles would allow to increase the operational depth of destruction of targets in the rear of the russian occupation army in Ukraine. And that is why the citizens of Ukraine fervently hope that their army will receive ATACMS in order to speed up the liberation of the territories occupied by the russians: otherwise, there wouldn't be, for example, such a hype in social networks based on unverified data that ATACMS was "already in Ukraine" and "in action".
Read more: The US Congress Declares the Need to Transfer ATACMS to Ukraine: Democrats and Republicans Support the Decision
But here we should emphasize an interesting thing. In fact, the US Army now has as many as five modifications of ATACMS in its arsenal, which differ in weight of the warhead and firing range, consequently. The entire diversity of the M142 HIMARS ammunition arsenal, including ATACMS modifications, is illustrated in the infographic below. And as for their features in particular, we can learn them from an article by ArmyInform.
ATACMS Block I
This is the basic version that was adopted by the US Army in 1991 and is still in service. It can also appear under the designations M39, MGM-140 or MGM-140A. The warhead of this missile has 950 M74 submunitions, each one can cover an area of up to 15 square meters. The firing range of this missile is up to 165 km. The guidance system is inertial, based on a ring laser gyroscope and ensures accuracy within 225-250 m from the target.
ATACMS Block IA & Block II
The Block IA modification entered service in 1998 and underwent a "baptism of fire" during the war against Iraq in 2003. May also appear under the designations M39A1 or MGM-140B.The warhead on this missile has three times reduced payload, compared to the previous version – only 300 M74 submunitions. But instead, the firing range increases to 290 km. Its guidance system is a combination of inertial one and GPS navigation.
On the basis of ATACMS Block IA, the ATACMS Block II missile was also created (it can appear under the indexes M39A2 or MGM-164). Its peculiarity is that the warhead consists of 13 self-guided BAT submunitions, designed to hit moving or stationary targets.
ATACMS Block IVA
Perhaps this is the most advanced modification of this missile the US Army has at its disposal. It may appear under the following designations: Block IA Quick Reaction Unitary, Block IA Unitary, Block IA Unitary PIP, QRU, M57, MGM-140E, MGM-168, T2K and XM57.
Speaking of the Block IA Unitary, the design preserved the combined guidance system, with the firing range reaching 300 km, but the 227-kg warhead is unitary, designed to destroy bunkers and fortifications. The "baptism" of this missile took place in 2003, too, during the war against Iraq.
In 2004-2005, this missile received a whole package of improvements – an improved guidance system, new software and the ability to hit targets with a vertical dive.
This missile may also appear under the designation M39A3. In this case, the P stands for Penetrator, it was developed specifically for the US Navy and designed to hit deep-seated targets.
May also be designated M57A1. In this case, we are talking about the modification of the missile, the development of which began in 2016. This missile is said to have a range of 300 to 450 kilometers and is equipped with the latest electronics.