The XR-003 Sapper Explosive Delivery System is believed by British Intelligence to be a product of secret U.S. weapons programs (which can be proven correct upon the release of Resistance 2 and the introduction of SRPA). It is obtained from a dead SRPA Black Op soldier like other weapons supposedly developed by the U.S. The function of the weapon is to create explosive organic material using DNA from Widowmakers. This explosive material is highly sensitive and likely to explode when approach. For this characteristic they serve are able to serve as proxy mines, because of this the weapon itself is able to use implanted microchips to disturb the material to the point of detonation.
Try to preempt where the enemy is going to run, such as Leapers and Gray Jacks, and lay down traps for them. As soon as the orbs sense an enemy nearby they will explode causing considerable damage if a cluster has been left.
In the Resistance 3 extras video "Remembering R1," it is shown that the Sapper model was originally assigned to a totally different weapon, a physics manipulator resembling the Gravity Gun from Half-Life 2. Developers state that the weapon was axed in this form because it could not be made to function correctly in time to make the ship date.