Space Linear Acceleration Mass Measurement Device (SLAMMD) - 06.27.18

Summary | Overview | Operations | Results | Publications | Imagery

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The Space Linear Acceleration Mass Measurement Device (SLAMMD) follows Newton's Second Law of Motion by having two springs generate a known force against a crewmember mounted on an extension arm, the resulting acceleration being used to calculate the subject's mass. The device is accurate to 0.5 pounds over a range from 90 pounds to 240 pounds.
Science Results for Everyone
Information Pending

The following content was provided by Suzanne McCollum, and is maintained in a database by the ISS Program Science Office.
Facility Details


Facility Manager(s)
Suzanne McCollum, NASA Johnson Space Center, Houston, TX, United States

Facility Representative(s)
Information Pending

Developer(s) Information Pending

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
NASA Research Office - Human Research Program (NASA Research-HRP)

ISS Expedition Duration
April 2005 - March 2010

Expeditions Assigned

Previous Missions
Information Pending


  • Onboard
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    Facility Description

    Facility Overview

    • The SLAMMD (Space Linear Acceleration Mass Measurement Device) was installed in the HRF-1 rack during Expedition 11. SLAMMD measures the on-orbit mass of crewmembers by applying Newton's Second Law of Motion (force is equal to mass times acceleration).

    • This device can measure mass from 95 to 240 pounds by using the known force generated by two springs located inside of the SLAMMD drawer. The resultant acceleration of the attached crewmember is measured and the mass then calculated.
    The Space Linear Acceleration Mass Measurement Device (SLAMMD) is intended to provide an accurate means of determining the on-orbit mass of humans between the 5th percentile Japanese female and the 95th percentile American male. SLAMMD will be rack mounted in a 4 panel unit (PU) drawer and will utilize an 8 PU drawer for stowage.

    The guiding principle of SLAMMD is Sir Isaac Newton's Second Law of Motion, F=ma (force is equal to mass times acceleration). Therefore, to find mass, the acceleration is divided into the force: m=F/a. For the HRF SLAMMD, the force is generated by two springs inside the SLAMMD 4 PU drawer. The acceleration used in calculating the mass is actually a calculated average acceleration with regression analysis. The acceleration is measured by a precise optical instrument which detects the position versus time trajectory of the SLAMMD guide arm and a micro controller which collects the raw data and provides the precise timing. The final computation is done via a portable laptop computer with SLAMMD unique software.

    The force is generated by two springs inside the 4 PU SLAMMD drawer. Each spring has Vectran (strong fiber) attached to one end which is fed around a separate pulley and back towards a central cam. The cam is attached to a centrally-located shaft which also has a flywheel and an encoder disk attached to it. The cam is designed such that, throughout the distance the springs stretch, a constant force is applied to the central shaft. This is an important design feature, so that the mass can be calculated using the m=F/a equation. The large flywheel has a lanyard attached to it that is fed through a small slit on the SLAMMD front panel and is attached to a connector. During SLAMMD operation, the latch connector is connected to a latch assembly on the SLAMMD guiding arm. With the cam design and presently selected springs, the force pulling the guide arm assembly inward is constant at 5.25 lbs (23.3 N). For human mass calculations, the crewmember wraps the legs around the leg support assembly like one would for a leg curl machine, aligns the stomach against the belly pad and rests either the head or chin on the head rest.

    For calibration and control calculations, a calibration arm assembly is attached to the SLAMMD guide arm. Using an 18-pound calibration mass at different lengths from the pivot point, different mass values can be simulated. The range will be from 90 pounds to 240 pounds.

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    Facility Operations

    • SLAMMD is a rack-mounted device. The crewmember mounts the guide assembly and pushes away from the drawer to a predetermined locking position.

    • An electromagnet is activated to stabilize the crewmember in the ready position. The electromagnet comes into contact with the latch attachment plate located on the guiding arm assembly.

    • When the magnet is released the test subject is pulled forward with low-level, constant force.

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    Decadal Survey Recommendations

    Information Pending

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    Results/More Information

    Results Publications

      Zwart SR, Launius RD, Coen GK, Morgan JL, Charles JB, Smith SM.  Body mass changes during long-duration spaceflight. Aviation, Space, and Environmental Medicine. 2014 September; 85(9): 897-904. DOI: 10.3357/ASEM.3979.2014.

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

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    Related Websites

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    image NASA Image: ISS012E12597 - Astronaut Bill McArthur sets-up the Space Linear Acceleration Mass Measurement Device (SLAMMD) in the Destiny Laboratory during Expedition 12. The SLAMMD Guiding Arm, Leg Restraint and Head Rest are visible attached to the Human Research Facility Rack 1 (HRF-1).
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    image NASA Image: ISS019E007130 The Human Research Facility (HRF) Rack 1 in the European Laboratory in Columbus. Visible is the HRF Ultrasound,Workstation 2,and HRF Cooling Stowage Drawer and the Space Linear Acceleration Mass Measurement Device (SLAMMD). Photo was taken during Expedition 19.
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    image NASA Image: ISS019E017901 View of Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata, Expedition 19 flight engineer, using the Space Linear Acceleration Mass Measurement Device(SLAMMD) hardware set up in the Columbus module. Hardware will be used for BMM (Body Mass Measurement) activities by the Expedition 19 crew.
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    image NASA Image: ISS020E015893 - European Space Agency astronaut Frank De Winne, Expedition 20 flight engineer, works with the Space Linear Acceleration Mass Measurement Device (SLAMMD) in the Columbus laboratory of the International Space Station.
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