NAVIGATION — CANOES TO SPACESHIPS — DRAPER 



309 



WHEN DEPARTURE AND DESTINATION ARE BEYOND I.INE-OF-SIGHT 

 CONTACT AMD DIRECT RADIATION CONNECTION IS NOT POSSIBLE, 

 INERTIAL REFERENCE COORDINATES MAY BE USED FOR GUIDANCE 



INERTIAL-REFERENCE- 



PACKAGE AXIS OF 



ROTATION; SET PARALLEL 



TO EARTH'S POLAR AXIS 



NOTE: FOR THE SAKE OF CLARITY, 

 THE SUPPORTING GIMBALS 

 AND ASSOCIATED DRIVES ARE 

 NOT SHOWN IN THE DIAGRAM. 



EARTH REFERENCE GIMBAL 

 (rotated obout the direction of 

 the eorfh's axis - dve to action 

 of the time drive and supporting 

 gimbol servos — to remain para 

 lel to the plane of a meridian as 

 the earth rotates) 



INERTIAL 



REFERENCE 



PACKAGE 



INERTIAL-REFERENCE-PACKAGE ORIENTATION IS INITIALLY ACCURATELY ESTABLISHED 

 WITH RESPECT TO INERTIAL SPACE, THAT IS, WITH RESPECT TO CELESTIAL SPACE (FOR 

 THE PURPOSESOF PRACTICAL GUIDANCE, INERTIAL SPACE AND CELESTIAL SPACE ARE 

 EFFECTIVELY IDENTICAL). THIS MAY INVOLVE THE USE OF DEVICES NOT INCLUDED IN 

 THE INERTIAL GUIDANCE EQUIPMENT. 



HIGH-PERFORMANCE INERTIAL-REFERENCE GYRO UNITS (GYRO UNITS WITH LOW DRIFT 

 RATES) SUPPLYING CORRECTION SIGNALS FOR SERVO-DRIVEN GIMBALS OPERATE TO AC- 

 CURATELY HOLD THE INERTIAL-REFERENCE-PACKAGE ORIENTATION WITH RESPECT TO 

 INERTIAL SPACE DURING THE PERIOD GUIDANCE IS REQUIRED. 



A SPECIFIC FORCE RECEIVER SYSTEM WITH SCHULER TUNING MAY BE USED TO ACCURATE- 

 LY INDICATE THE VERTICAL IN MOVING VEHICLES. 



MEASUREMENT OF THE ANGLES BETWEEN THE VERTICAL AND A MEMBER FIXED WITH THE 

 PROPER ORIENTATION TO THE EARTH REFERENCE GIMBAL GIVES PRESENT POSITION OF 

 THE VEHICLE ON THE EARTH. 



Figure 6. — Guidance by substitution of inertial reference coordinates for celestial 



coordinates. 



high accuracy under conditions of operation. The essential features 

 of systems based on reference members of this kind are discussed in 

 the sections that follow. 



SELF-CONTAINED GEOMETRICAL REFERENCES FOR NAVIGATION BY 

 APPLICATION OF GYROSCOPIC PRINCIPLES 



Gyroscopic effects are mainly associated with the mechanical be- 

 havior of a balanced, symmetrical rotor spinning rapidly about its 



