Abstract : A study is made of the use of drag modulation to reduce deceleration loads during atmosphere entry. The design of a space vehicle which must be capable of entering the earth's atmosphere involves, among other things, the consideration of the accuracy with which its landing point can be predicted, the maximum deceleration loads which the vehicle will experience, and the aerodynamic heating to which the vehicle is exposed. A scheme is examined whereby these loads may be reduced to a tolerable level. This is accomplished by variation of the drag of the vehicle (either discretely or continuously) in a properly programmed fashion. It is found that the use of continuous drag modulation can reduce the deceleration loads by as much as 50%, without significantly affecting the total aerodynamic heating of the vehicle. Particular numerical solutions of the complete equations of motion are also included. These substantiate the results of the approximate analysis. In addition, several specific applications of drag modulation have been considered, such as to a vehicle returning from the moon. (Author)