A barrage weapon, the UP (Unrifled Projectile) rocket was a barrage weapon system fielded on ships of the British navy as well as put into field emplacements- Z batteries- around England as part of the Home Guard defense network.
The rockets were designed to reach an altitude, around 1,000 + feet depending on sources, deploy a parachute and let a mine drift down. The mine would foul an oncoming aircraft and destroy/damage it with the aerial explosive.
The simple explosive rocket system was mounted in racks, in Z battery configurations, and multi-barreled launchers as shipborne defense. The land launchers were usually two launchers per battery, clustered with 64 other batteries around the protective zone. When launched the rockets were hurled skyward in a salvo of 128 rockets.
The shipborne defense were installations of 20 tube per unit.Each ship battery would fire one salvo of ten tubes, followed by the second salvo.
Drawbacks of the UP system were its slow reload and general inaccuracy, especially if variable wind conditions caught the parachute-borne mines, drifting them off target and potentially onto friendly forces.