The U.S. Army is spending another $12 million to try and get their new XM-7 Spider “user detonated landmine” system working and into production. The XM-7 has been in development since 1999, and about $150 million has been spent to get the system working reliably enough to send into combat. This was supposed to happen starting in 2004, but there were delays, most of them for technical problems. It was believed that the XM-7 would be useful defending bases in Iraq and Afghanistan. But the delays kept preventing mass production. This new contract is one last effort to get this system ready for action. Four years ago the United States thought it could use XM-7 to replace the traditional anti-personnel mines used along the 243 kilometer long DMZ (DeMilitarized Zone) in South Korea. That is still a viable option.
The XM-7 has a combined mine/sensor system that could either be controlled by troops or put on automatic. The XM-7 Spider consists of MCUs (Munition Control Units), which look like a coffee can with 6 smaller (like Red Bull cans) “mines” sticking out at 60 degree intervals (all around, in other words). The smaller cans contain a tripwire deployment device and an explosive about the size and power of a hand grenade. When activated by a wireless controller, each MCU fires out the trip wires about 20 meters. When one of these trip wires is disturbed the operator is alerted. The operator uses a RCS (Remote Control Station), which is basically a customized laptop. Each RCS can control 84 MCUs and uses one or more repeaters to maintain control over all the MCUs. The operator makes the decision to fire one or more explosive devices on the MCU, or not.
Spider is not buried, although it can be covered with some vegetation. However, it can often be seen in daylight and easily destroyed with rifle fire. But at night, Spider can be a problem for an enemy trying to get through. Of course, animals will also trigger the tripwire, and troops need to watch the area occupied by the MCUs and be able to double check what's out there.
Spider was designed with an "automatic" mode the operator could trigger, which meant the devices released their grenades automatically if the trip wire was disturbed. But this feature was removed, officially anyway, for political reasons. The automatic mode could be turned off remotely. The battery on each MCU is good for 30 days, after which troops have to go out and install fresh batteries.
Spider can also be armed with non-lethal payloads. The explosive devices will also self-destruct after a certain time, to insure that they do not get lost and lay around for years threatening civilians. Spider was to have been available to the troops in 2010, but testing uncovered more technical problems. Back then the U.S. Army was going to buy 903 XM-7 systems (each with 84 MCUs and 503 of the actual munitions) for $555,000 (including the development expense). That meant each of the hand grenade-like munitions was costing $1,100. Landmines cost less than a tenth of that and hand grenades go for about $35 each. In theory, the MCUs can be reloaded and reused, as can the control electronics. But in practice this was not expected to happen, not if the DMZ came under determined attack.