Seats to prevent or limit crash injuries to astronauts aboard the crew vehicle of the Orion spacecraft are undergoing development. The design of these seats incorporates and goes beyond crash-protection concepts embodied in prior spacecraft and racing-car seats to afford superior protection against impacts. Although the seats are designed to support astronauts in a recumbent, quasi-fetal posture that would likely not be suitable for non-spacecraft applications, parts of the design could be adapted to military and some civilian aircraft seats and to racing-car seats to increase levels of protection.
The main problem in designing any crashworthy seat is to provide full support of the occupant against anticipated crash and emergency-landing loads so as to safely limit motion, along any axis, of any part of the occupant’s body relative to (1) any other part of the occupant’s body, (2) the spacecraft or other vehicle, and (3) the seat itself. In the original Orion spacecraft application and in other applications that could easily be envisioned, the problem is complicated by severe limits on space available for the seat, a requirement to enable rapid egress by the occupant after a crash, and a requirement to provide for fitting of the seat to a wide range of sizes and shapes of a human body covered by a crash suit, space suit, or other protective garment. The problem is further complicated by other Orion-application-specific requirements that must be omitted here for the sake of brevity.
To accommodate the wide range of crewmember body lengths within the limits on available space in the original Orion application, the design provides for taller crewmembers to pull their legs back closer toward their chests, while shorter crewmembers can allow their legs to stretch out further. The range of hip-support seat adjustments needed to effect this accommodation, as derived from NASA’s Human Systems Integration Standard, was found to define a parabolic path along which the knees must be positioned. For a given occupant, the specific position along the path depends on the distance from the heel to the back of the knee.
The application of the concept of parabolic adjustment of the hip-support structure caused the seat pan to also take on a parabolic shape, yielding the unanticipated additional benefit that the seat pan fits the occupant’s buttocks and thighs more nearly conformally than do seat pans of prior design. This more nearly conformal fit effectively eliminates a void between the occupant’s body and the seat pan, thereby helping to prevent what, in prior seat designs, was shifting of the occupant’s body into that void during an impact.
The seat includes a thigh-support structure and a lower-leg support structure that can be adjusted for various heel-to-back-of-knee lengths. The occupant’s heels are supported by a heel support pan and could be affixed to the pan by clips similar to those of mountain biking shoes and pedals or by straps over the tops of the feet. At the pivot between the thigh and lower-leg support structures there is a flat panel that provides for strength in adjustment and provides lateral support of the knees. The combination of lateral support of the knees and support and restraint the of the feet is intended to prevent flailing or other movement of the legs while the occupant is seated.
The seat includes lateral supports at the hips that serve the dual purpose of restraining the occupant from shifting laterally and providing structural support to the rest of the seat by acting as a gusset. To accommodate all hip sizes, the seat pan is designed to fit the largest hip breadth allowable. For a smaller occupant, spacer pads can be installed to fill the voids. Shoulder supports, which cover the shoulder joints and extend short distances down the arms, are also sized for occupants having shoulders of maximum breadth and to be fitted to smaller occupants by use of spacer pads. The seat supports bony protrusions of the torso at the shoulders and hips only, leaving the mid-torso area free of supports to enable the occupant to leave the seat by rolling though the clear space.
The seat includes a head support. However, head support on the prototype differs from the envisioned Orion head support: In Orion, the occupant would wear a space helmet and the head support would extend along the right and left sides of the helmet to prevent lateral motion of the head.
Another prominent design feature is a load-distributing seven-point harness similar to harnesses worn in off-road automobile racing. The seven-point harness includes straps over the tops of the shoulders that act, in effect, as wraparound extensions of the lateral shoulder supports.
This work was done by Dustin Gohmert of Johnson Space Center. MSC-24485-1
This Brief includes a Technical Support Package (TSP).
Crashworthy Seats Would Afford Superior Protection
(reference MSC-24485-1) is currently available for download from the TSP library.
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Overview
The document titled "Crashworthy Seats Would Afford Superior Protection" outlines the design and functionality of a revolutionary seat developed for the Orion spacecraft, aimed at ensuring the safety and comfort of astronauts during space missions. This seat is engineered to accommodate a wide range of body types, from the 1st percentile female to the 99th percentile male, making it a significant advancement in occupant protection.
A key feature of the seat is its parabolic adjustment mechanism, which allows for a conformal fit to the occupant's body. This design minimizes void spaces between the body and the seat, reducing the risk of movement during impacts. The seat pan is shaped to fit the contours of the buttocks and thighs, preventing occupants from shifting and enhancing overall stability. Additionally, the lower leg support structure is adjustable to cater to various heel-to-popliteal lengths, ensuring that all crewmembers can be securely positioned.
The seat also incorporates lateral support at the hips and shoulders, which serves dual purposes: restraining the occupant and providing structural support to the seat itself. This design allows for a common minimum spacing of the occupants' feet from the vehicle's pressure vessel, accommodating the varying leg positions of taller and shorter astronauts. The shoulder supports are designed to envelop the shoulder joint, allowing for free movement of the mid-torso area, which is crucial for egress in emergencies.
Safety features include a load-distributing 7-point harness similar to those used in off-road racing, and an "anti-elongation" support that prevents occupants from being ejected from their seats during rollover events or high-impact scenarios. This is particularly important in the context of the Orion capsule, where maintaining occupant safety during dynamic conditions is critical.
The document also highlights potential commercial applications of this seat design beyond space travel, including military aviation and the auto-racing industry, where similar safety features could enhance occupant protection.
In summary, the innovative design of the crashworthy seat represents a significant leap forward in occupant safety technology, tailored specifically for the unique challenges of space travel while also offering broader applications in various high-risk environments.
