The hi-mars systems or the M142 High mobile artillery rocket system is a light multiple rocket launcher developed in late 1990s for US military at per unit of 5.1 million dollars.
The hi-mars systems has operation range of 480 km and effective range of 300 km. The system is good and has been used in Afghanistan, Iraq and Syria but the system also has some short comings.
The biggest advantages of himars systems is its effectiveness against insurgency where the system operates under the cover of US air force and the use of GPS signals to locate accurately the target and destroy it on a battle field.
The advantages turn to disadvantages when fighting an intensity war like the one being fought in Ukraine right now where there is no air cover or protection for Ukraine forces and GPS signals can be jammed by Russia’s military.
If you the see the drills and the himars systems in action, you will notice that it takes time to set up the system and needs a big area which makes it exposed, this is a disadvantage because currently Russia’s military has ” search and destroy policy” where any weapon system supplied by US and its allies is searched and destroyed even before entering the battle field.
Few systems which manages to get to the battlefield also suffers the same fate since Russia’s military will search and destroy any system identified as a threat. Russia enjoys total air superiority in Ukraine and also has ability to jam US GPS signals.
This means that if Ukraine wants this US supplied himars systems to survive on battle field, Ukrainian soldiers will have to constantly fire and rapidly change positions which demands a lot of manpower and requires well trained personal which I don’t think Ukraine has at the moment.
Reports from some western media say that the himars system will be a threat to Russia’s artillery forces due to its range and accuracy which is wrong because Russia’s artillery are protected by both Russian air force and advanced air defense systems and that long range gives Russia’s air defense systems time to react unlike short range shells.
The himars systems was made under assumption that US military will always enjoy military superiority which is not the case in Ukarine. This assumption meant that the manufacturers never considered time of reloading and loading the system and the system operates on big area which leaves exposed to air targets.
The only way Ukraine can turn things around in eastern Ukraine is by gaining air superiority which is impossible at this stage since almost all of its air force assets were destroyed or damaged.