PASSIVE.—In the passive homing system (fig. 3-5), the directing intelligence is received from the target. Examples of passive homing include homing on a source of infrared rays (such as the hot exhaust of jet aircraft) or radar signals (such as those transmitted by ground radar installations). Like active homing, passive homing is completely independent of the launching aircraft. The missile receiver receives signals generated by the target and then the missile control section functions in the same manner as previously discussed. REVIEW NUMBER 1 ANSWERS A1. If a guided missile is traveling at Mach 1, it is traveling at approximately 766 miles per hour. A2. A missile traveling at Mach 3 is traveling at supersonic speeds. A3. The two types of guided missiles are service and nonservice guided missiles. A4. The two types of guided missiles used in naval aviation   are   air-to-air   and   air-to-surface guided missiles. A5. The   first   letter   of   a   missile   designation describes the missile's launch environment. A6. The  missile  designation  ATM  stands  for  an air-launched training guided missile. A7. The serial number in an assembled missile is usually found on the leading component. A8. The  color  codes  on  guided  missiles  identify the   explosive   hazard   in   the   missile   com- ponent. Armament Section The    armament    system    contains    the    payload (explosives), fuzing, safety and arming (S&A) devices, and target-detecting devices (TDDs). PAYLOAD.—The payload is the element or part of the   missile   that   does   what   a   particular   missile   is launched to do. The payload is usually considered the explosive  charge,  and  is  carried  in  the  warhead  of  the missile.   High-explosive   warheads   used   in   air-to-air guided missiles contain a rather small explosive charge, generally 10 to 18 pounds of H-6, HBX, or PBX high explosives.  The  payload  contained  in  high-explosive warheads used in air-to-surface guided missiles varies widely,  even  within  specific  missile  types,  depending on the specific mission. Large payloads, ranging up to 450 pounds, are common. Comp B and H-6 are typical explosives used in a payload. Most exercise warheads used with guided missiles are  pyrotechnic  signaling  devices.  They  signal  fuze functioning  by  a  brilliant  flash,  by  smoke,  or  both. Exercise warheads frequently contain high explosives, which vary from live fuzes and boosters to self-destruct charges that can contain as much as 5 pounds of high explosive. FUZING.—The    fuzing    and    firing    system    is normally  located  in  or  next  to  the  missile's  warhead section. It includes those devices and arrangements that cause   the   missile's   payload   to   function   in   proper relation to the target. The system consists of a fuze, a safety  and  arming  (S&A)  device,  a  target-detecting device (TDD), or a combination of these devices. There are two general types of fuzes used in guided missiles—proximity fuzes and contact fuzes. Acceleration  forces  upon  missile  launching  arm  both fuzes.   Arming   is   usually   delayed   until   the   fuze   is subjected  to  a  given  level  of  accelerating  force  for  a specified amount of time. In the contact fuze, the force of  impact  closes  a  firing  switch  within  the  fuze  to complete  the  firing  circuit,  detonating  the  warhead. Where proximity fuzing is used, the firing action is very similar  to  the  action  of  proximity  fuzes  used  with bombs and rockets. SAFETY AND ARMING (S&A) DEVICES.— S&A devices are electromechanical, explosive control devices. They maintain the explosive train of a fuzing system  in  a  safe  (unaligned)  condition  until  certain requirements of acceleration are met after the missile is fired. 3-6 Figure 3-5.—Passive homing system.