[[Body Posture for Space Design]] ---- # a. Single Size For All A single size may accommodate all members of the population. Eg. A workstation which has a switch located within the reach limit of the smallest person, for instance, will allow everyone to reach the switch. # b. Adjustment The design can incorporate an adjustment capability. Eg. Automobile seat. # c. Several Sizes Several sizes of equipment may be required to accommodate the full population size-range. Eg. space suits ## Body strike envelope The volume that the extremities (legs, head, arms) of a seated and restrained crewmember will strike when subjected to high accelerations such as during launch and entry ###### Microgravity Effects The spine will lengthen under microgravity conditions. This will increase the overhead reach limits. Downward reaches are more difficult; there is no gravity assist. ###### Multi-G Effects Abrupt high accelerations + extremities; hence consider nonfunctionality and potential injury of the reach envelope. **Acceleration Possible Reach Motion** Up to 4-G Arm Up to 5-G (9-G if arm is counter balanced) Forearm Up to 8-G Hand Up to 10-G Finger #### Restraint Design Considerations The absence of gravitational forces will facilitate rather than restrict body movement, this lack of gravity will leave crewmembers without any stabilization when they exert a thrust or push. ###### Aim - To attain absolute maximum functional reach Three basic types of body restraint or stabilizing devices are **1. Handhold** The individual is stabilized by holding onto a handgrip with one hand and performing the reach or task with the other Drawbacks- Body control is difficult and body stability is poor **2. Waist** A waist restraint ( clamp/belt) affords good body control and stabilization, but limits the range of motion and reach distances attainable. **4. Foot restraints** Restrains the individual by the feet. Foot restraints must be placed under the work surface. Excellent in reach performance, stability, and control. A large reach envelope to the front, back, and to the sides #Kareena