SLS

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Presentation

Background

SLS-1
The SLS is the second version of a prototype subject loading system, developed by the Université catholique de Louvain (UCL) and Arsalis (Belgium) in cooperation with the support of Verhaert Space (Belgium), the European Space Agency (ESA) and Prodex, specifically for the second generation treadmill (T2) on the International Space Station (ISS).

Microgravity is known to cause loss of bone and muscle mass. Current evidences indicate that impact loading,bone stress and muscular work, as implied by exercises such as treadmill running, are important countermeasures for maintaining bone and muscular mass. In microgravity, such an exercise requires a Subject Loading System (SLS) in space, i.e. a means to hold the subject down onto the surface of a treadmill while he/she runs.

Design

Over 15 candidate concepts, including different actuators (EMA’s, springs, pistons, bellows) and transmission systems (cams, gear-boxes, fusees), have been studied by Verhaert Space.
These concepts were rated against 15 trade-off criteria such as expected performance and accuracy, proof of concept, engineering budgets (mass, power, dimensions), safety, reliability, maintainability.

The retained concept for the SLS is the one proposed by Arsalis:
SLS-concept
The pneumatic pressure system:

SLS-overview

Functional requirements

SLStest1
SLStest2
The SLS concept is designed to meet the following functional requirements established by the ISS International Partners (CSA, ESA,
JAXA, NASA and RSA):

Accomodation

SLSinT2SLSinT2 The SLS is designed to fit the allocated volume within the T2 ISPR rack

Prototype

The T2 SLS prototype is currently mounted in a simple test rack that allows the SLS to be driven with approximately sine wave displacements ranging in amplitude from ±5.0 cm to ±12.5 cm in 2.5 cm increments.
The ‘step frequency’ can be varied from 0.1 Hz to 3 Hz.
The pull-down force can be varied continuously between 0 and more than 500 N.

A dedicated software allows to:

test Rack view 1test Rack view 2test Rack view 3test Rack view 4Software screenshot (Pressure, force, displacement in scope mode)Software screenshot (force vs piston position)Software screenshot (force vs pressure)Software screenshot (parameters variations statistics)

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test Rack view 1 (1/8)

test Rack view 1

test Rack view 2 (2/8)

test Rack view 2

test Rack view 3 (3/8)

test Rack view 3

test Rack view 4 (4/8)

test Rack view 4

Software screenshot (Pressure, force, displacement in scope mode) (5/8)

Software screenshot (Pressure, force, displacement in scope mode)

Software screenshot (force vs piston position) (6/8)

Software screenshot (force vs piston position)

Software screenshot (force vs pressure) (7/8)

Software screenshot (force vs pressure)

Software screenshot (parameters variations statistics) (8/8)

Software screenshot (parameters variations statistics)

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Downloads

SLS Poster Angers 2008 (1123 kB)

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