SPACE EXPLORATION — SEAMANS 271 



the moon and return to earth, and finally an actual moon landmg and 

 return, planned late in this decade. 



The Saturn launch vehicle which is now under development will 

 not provide the capability for circumlunar flight and lunar landing. 

 In the near future, we will commence the development of larger 

 launch vehicles. Implementation of this program will result in the 

 investment of large sums for research, development, and capital equip- 

 ment. We must select the vehicle configurations wisely in order to 

 fulfill our immediate objectives and to maximize our capabilities for 

 other possible missions involving large payloads. 



The design of the Apollo spacecraft itself must be kept as flexible 

 as possible to meet the requirements of an orbiting laboratory, as well 

 as circumlunar and lunar-landing flights. To achieve this flexibility, 

 the so-called "modular concept" will be employed. In other words, 

 various building blocks or units of the vehicle systems will be used for 

 difl'erent phases of missions. The first component, which we call the 

 "command center module," will house the crew during launching and 

 entry. It will also serve as a flight control center for the remainder of 

 missions. 



The second module is a propulsion unit. In earth-orbital flights, 

 this unit will return the craft to earth under either normal or emer- 

 gency conditions. It will also be used for maneuvering in orbit and 

 for orbital rendezvous with other satellites. For circumlunar flights, 

 the propulsion module will return the spacecraft to earth safely from 

 any point along the lunar trajectory and will provide midcourse and 

 terminal guidance corrections. In addition, the propulsion module 

 will inject the Apollo spacecraft into an orbit around the moon and 

 eject it from that orbit toward earth. For the lunar landing mission, 

 the propulsion unit will serve as the takeoff stage. 



The third module is a propulsion stage that will decelerate the 

 spacecraft as it approaches the moon, and will gently lower it to the 

 moon's surface. 



For the earth-orbital laboratory an additional module may be added 

 to the spacecraft to provide capacity for scientific instrumentation 

 and for life support during a reasonably long-lived orbit. 



It is important to note that the command center module for lunar 

 flights will have to be designed to permit entry into the atmosphere at 

 25,000 miles per hour, or at nearly one and one-half times the speed of 

 a satellite returning from orbit. Developing protection against entry 

 heating will be one of our most difficult problems. The spacecraft 

 must have a moderate amount of maneuverability within the atmos- 

 phere to control the flight path and to allow landing at a preselected 

 site. All designs being considered must be capable of surviving either 

 ground or water landings. 



