The M904 and M905 delay elements are part of the guidance system used for the Standard Missile 3 (SM-3) interceptor missile. The M904 delay element is placed between the missile's boost motor and the separating stage, while the M905 delay element is placed between the missile's separating stage and the guided missile's rocket motor.
These delay elements are inserted into the missile's payload at specific times and for specific reasons:
- The M904 delay element is inserted to provide proper spacing between the missile's boost motor and the separating stage. This ensures that the thrust from the boost motor does not impact or interfere with the missile's separating stage, which could affect the missile's trajectory and performance.
- The M905 delay element is inserted to provide proper spacing between the missile's separating stage and the guided missile's rocket motor. This spacing helps to ensure that the missile's separating stage has sufficient time to clear the boost motor before the guided missile's rocket motor ignites. This also helps to prevent the rocket motor from damaging the separating stage or interfering with the missile's trajectory.