running on the moon

Running on the MoonFrancois Decuir

IntroductionIn reduced gravity <0.5g, running requires

less energy than walking

• In space, the pressure inside space suits is high enough that it helps support the total weight

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006614#pone.0006614.s003

IntroductionSpace suits affect the walk-run transition by

mobility restriction, changes in stability, and increased joint mechanical work

VideoThe pressure in the space suit keeps the knee from buckling. This makes walking expend more energy.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006614#pone.0006614.s003

IntroductionFroude Number

By modeling walking as an inverted pendulum, we find that walking occurs only when Fr≤1.

IntroductionApollo Number

The Apollo number is defined as the Froude number multiplied by the inverse of the mass ratio M.

When no space suit is present, M=1 and Ap=Fr

Variablesv=velocityL=hip height or center of mass heightM=ratio of human carried mass to total

transported massg=gravitational accelerationα&β=shape and location of the state transition

PhysiologicalThe physiological variables include the length

of the leg, L, and the mass ratio, M.When attempting to manipulate the Apollo

number, the variable M can be changed. This can give either a higher or lower chance to be in a “run” state.

Important models

Change in M to keep the Apollo number constant.

Probability that gait=1

RecreationMATLAB was used to recreate

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006614#pone.0006614.s003

Apollo Number

Walk

or R

un

sta

te

Alteration

To allow a shorter astronaut to run at the same speed as a taller astronaut, the weight of the space suit must be altered.

Lower space suit weight/Shorter hip height

Higher space suit weight/ Longer hip height

Ap

ollo

Nu

mb

er

Mass Ratio

PossibilitiesEmergency situation occurs

BenefitsOptimizing space suits for travel to the Moon

and Mars

ConclusionIn a suit with a higher mass, M, the walk-run

transition will occur at lower speedsAs loads reduce the self-support, M, walking

becomes possible at higher velocities

Questions