Modeling and Testing of a Mechanical Counterpressure Bio-Suit System

Abstract

The President's Vision for Space Exploration calls for a returned human presence on the Moon, followed by human missions to Mars. The astronauts on these missions will require a more robust and flexible spacesuit than currently exists to conduct exploration and science operations as well as maintain a base on planetary surfaces.The BioSuit system is a modular spacesuit concept based on the theory of mechanical counterpressure (MCP). Considerable experimental work has been conducted in the field of MCP, but there has been no analysis of the hypothetical best level of uniformity of pressure production for this type of spacesuit design. Therefore, computer modeling has been undertaken to verify the feasibility of such a design, which is based on not only providing the required pressure on the skin, but also limiting the variation of pressure production around a cross-section of the body. Given the data sets available, which exclusively consist of legs under normal atmospheric pressure, not mechanical counterpressure, the modeling work indicates that a MCP-based design can meet these requirements.This thesis advances the BioSuit design by laying out the system level requirements, and also by setting requirements for the fabric and closure mechanism in order to design a working prototype. As part of this design process, the team has further developed the elastic bindings concept, which previously was designed to produce pressure only on the calf. Now the team has extended the design to protect the entire leg in an underpressurized environment. Based on blood pressure, skin temperature, heart rate, and qualitative comfort ratings, the bands have proven successful at protecting the leg (with the exception of some minor edema on the knee) at the desired underpressure (-225 mm Hg) over a full hour. A simple knee brace which filled the concavities of the knee was also tested, and proved successful in preventing edema in one trial.While the design is not yet capable of operational testing due to limitations in mobility, it is a valuable stepping point towards developing a full BioSuit system.

Low spring index, large displacement Shape Memory Alloy (SMA) coil actuators for use in macro- and micro-systems

“…[19][20][21][22][23] For this application, we prioritize maximum force generated (to create maximum counter-pressure) over other design variables, using the following criteria:…”

Materials and Textile Architecture Analyses for Mechanical Counter-Pressure Space Suits using Active Materials

“…1b-c), designed by Prof. Dava Newman, represents an innovative, modern approach to MCP suit design. The underlying concepts of this suit have been demonstrated through sub-component static testing, and full-suit mockups have been developed and produced to illustrate advanced restraint patterning 5,20,24 . The driving design requirement of an MCP suit is that it must provide sufficient counter pressure to keep the user alive.…”

“…The equations for each x-and y-component are thus phase shifted, but the equation for each z-component remains the same in each strand, which makes the shape radially symmetric. (24) When the function described by Eq. (24) is revolved about the θ axis it forms the sidewalls of the biaxial braid in Fig.…”

“…(1), σ θ is hoop stress, P is counter pressure, r is local limb radius, b is material thickness, l is the axial length of the cylinder, F is circumferential force acting on the area described by the thickness and length, and T is the wall tension (defined as total circumferential force extended along the entire radial thickness). For the estimated largest limb radius (the upper thigh of a 95th percentile male, 10.7 cm), a minimum active hoop stress of 0.633 MPa at 5 mm thickness is required 8,24,28 . This corresponds to a wall tension of 31.65 N/cm 21 .…”

“…1a), but the concept was tabled due to limitations in available materials, user discomfort, funding, and donning and doffing challenges 6 . More recent research efforts to advance MCP suit design have been conducted at multiple universities, including at the University of San Diego and in the Man Vehicle Laboratory (MVL) at MIT 5,[7][8][18][19][20][21][22][23][24][25][26] . The MIT BioSuit™ system (see Fig.…”