Space Linear Acceleration Mass Measurement Device (SLAMMD)
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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.
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.
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This content was provided by Cynthia P. Haven, and is maintained in a database by the ISS Program Science Office.
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Facility Manager(s)
Facility Representative(s)
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Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
April 2005 - March 2010
Expeditions Assigned
11,12,13,14,15,16,17,18,19/20,21/22
Previous ISS Missions
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Availability
- 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.
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.
- 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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