Background During early spaceflights, many crewmembers did not meet their caloric requirements and consequently lost body mass during flight, as assessed by a decrease in postflight body mass. Maintaining body mass during spaceflight is crucial for maintaining crew health and monitoring body mass is thus important to medical operations as well as being a key component of human research. Determining body mass becomes difficult in a microgravity environment. Methods We report data from two mass measurement devices on the International Space Station (ISS): the Russian body mass measuring device (BMMD), which uses spring oscillation physics, and NASA's Space Linear Acceleration Mass Measurement Device (SLAMMD), which uses Newton's second law of motion (F = ma). Results For 25 crewmembers whose body mass was measured on both devices, significant body mass loss occurred compared to preflight (gravimetric scale) and averaged -4.4% as assessed by BMMD and -2.8% as assessed by SLAMMD. After an initial loss in the first 30 d of flight, body mass remained constant through the rest of the mission, as determined using either device. The mean difference between the two devices was 1.1 kg when the closest SLAMMD and BMMD measurements were compared (6.9 ± 6.2 d apart). Dietary intake during flight is approximately 80% of the World Health Organization estimated requirement and the decrease in body mass follows in-flight energy intake closely on average. Conclusion Body mass monitoring is important for monitoring crew health during a mission and to help ensure that crewmembers consume adequate energy intake to mitigate the risks of spaceflight.

Body mass changes during long-duration spaceflight.

The fat-to-lean ratio of tissue on a human subject is measured by the subject standing on a platform (100), raising his or her heels, then allowing his or her weight to fall onto the board near a transducer to produce a force. A sensor transmits a voltage signal to an analog-to-digital (A/D) converter. The subject's stomach (300), buttocks (310), and other flesh will continue moving in a downward direction (335) (below their rest position) after the skeleton has stopped moving. This results in a downward force on the board which is registered as a data peak (580) in a computer through the action of the sensor and the A/D converter. Tissue elasticity will cause the stomach and buttocks to then move upward (350), above their normal resting position. This will result in a lessening of the force and a corresponding minimum (590) in the output wave. The wave thus is a damped sinusoid which can be analyzed using various means to result in an "excess pendulous fatty tissue index" which is indicated by humanly sensible readout display.

Dynamic measuring system for determining the amount of excess body fat

Mass measurement using a relay feedback system was studied experimentally. The measurement system has an on-off relay with hysteresis and switches force acting on the object in relation to its velocity. Such nonlinear control induces a limit cycle in the feedback system. The mass of the object is determined from the period of this limit cycle. The apparatus manufactured for experimental study uses two voice coil motors (VCM's), one of which is for driving the object and the other is for generating prescribed disturbances. The effects of system parameters and disturbances on measurement accuracy were examined experimentally.

Mass Measurement System Using Relay Feedback with Hysteresis

The paper describes BIC 3, the latest prototype of inertial balance made at INRIM (former IMGC–CNR) in view of its possible use on board the International Space Station. The main characteristic of this instrument is its ability to work both in weightless conditions and on Earth surface with metrological performances comparable to those of a laboratory-level classic balance. BIC 3, although still based on the same centrifugal method adopted in the two previous prototypes, widely differs from them as regards configuration (constant speed), main motor characteristics (here a stepping motor is used), force transducer (the integral beam of a commercially-available balance), and consequently shows metrological performances considerably improved. The main constructional features are described and the metrological characteristics resulted from on-Earth tests are reported and discussed. A test made of 175 measurements in the range 0–150 g showed an expanded uncertainty of 4.1 mg.

BIC 3, the Latest Inertial Centrifugal Balance for Mass Measurement in Weightless Conditions

The importance of nutrition in exploration has been documented repeatedly throughout history, where, for example, in the period between Columbus' voyage in 1492 and the invention of the steam engine, scurvy resulted in more sailor deaths than all other causes of death combined. Because nutrients are required for the structure and function of every cell and every system in the body, defining the nutrient requirements for spaceflight and ensuring provision and intake of those nutrients are primary issues for crew health and mission success. Unique aspects of nutrition during space travel include the overarching physiological adaptation to weightlessness, psychological adaptation to extreme and remote environments, and the ability of nutrition and nutrients to serve as countermeasures to ameliorate the negative effects of spaceflight on the human body. Key areas of clinical concern for long-duration spaceflight include loss of body mass (general inadequate food intake), bone and muscle loss, cardiovascular and immune system decrements, increased radiation exposure and oxidative stress, vision and ophthalmic changes, behavior and performance, nutrient supply during extravehicular activity, and general depletion of body nutrient stores because of inadequate food supply, inadequate food intake, increased metabolism, and/or irreversible loss of nutrients. These topics are reviewed herein, based on the current gap structure.

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S.F. Khlopina

Papers

Device for mass measurement under zero-gravity conditions.