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Yusaku Fujii Yusaku Fujii Gunma UniversityGunma University

Instrument for measuringInstrument for measuring

astronaut body mass astronaut body mass

84th Annual AsMA Scientific Meeting

Chicago, USA - May 12-16 2013

Disclosure Information84th Annual AsMA Scientific Meeting

Yusaku FUJII

I have no financial relationships to disclose.

I will not discuss off-label use and/or investigational use in my presentation

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Three types of MMD (Mass Measurement Device)

f [Hz]

l [m]

w [rad/s]

m1 m2

F -F

Spring-mass system Centrifugal forceF=Ma, or ∫Fdt = M v⊿

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Methods proposed by Fujii Laboratory

SMMD: Small Mass Measurement Device

BMMD: Body Mass Measurement Device

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Ground Test Setup for Space BalanceGround Test Setup for Space BalanceGround Test Setup for Space Balance (SMMD): Principle

∫F dt = M(v1 - v2). Then the mass of the moving part is estimated as M = (∫F dt ) / (v1 - v2)≡ ME.

ObjectM

Base

Impact force: F [N]

Velocity of mass: before the collision: v1 [m/s]

after the collisioin: v2 [m/s]

Impulse acted on the base:∫F dt Momentum change: M(v1 - v2)

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Ground Test Setup for Space BalanceGround Test Setup for Space BalanceGround Test Setup for Space Balance: Experimental Setup

M

m

Tilting stage Mirror

Autocollimator

Interferometer

Force sensorSponge Cube corner prism

attached on the moving stage

Moving part(M)

Guide part ofLiner bearing “Air-Slide”

Attached mass(m)

Base (Mass >> M)

uc,r=10-4

T=0.05s

uc,r=2×10-2

T=0.001s

Y. Fujii, H. Fujimoto and S. Namioka, “Mass measurement under weightless conditions”, Rev. Sci. Instrum., Vol. 70, No.1, pp.111-113, 1999.

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Ground Test Setup for Space BalanceGround Test Setup for Space BalanceGround Test Setup for Space Balance: Experimental Results

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Ground Test Setup for Space BalanceGround Test Setup for Space BalanceSpace Balance: Specimen measurement

Y. Fujii, H. Fujimoto, R. Watanabe, Y. Miki, “Balance for measuring mass under microgravity conditions”, AIAA Journal, Vol.39, No.3, pp.455-457, 2001.

m1 m2

F -F

Publications on SMMD/BMMD[1] Y. Fujii, H. Fujimoto and S. Namioka, "Mass measurement under weightless conditions", Rev. Sci. Instrum., Vol. 70, No.1, pp.111-113, 1999. SMMD

[2] Y. Fujii, H. Fujimoto, R. Watanabe, Y. Miki, "Balance for measuring mass under microgravity conditions", AIAA Journal, Vol.39, No.3, pp.455-457, 2001. SMMD

[3] Y. Fujii and K. Shimada, "Instrument for measuring the mass of an astronaut", Meas. Sci. Technol., Vol.17, No.10, pp.2705-2710, 2006. BMMD

[4] Y. Fujii and K. Shimada, "The space scale: An Instrument for astronaut mass measurement", Trans. Jpn. Soc. Aeronaut. Space Sci., Vol.50, No.170, pp.251-257, 2008. BMMD

[5] Y. Fujii, K. Shimada, M. Yokota, S. Hashimoto, Y. Sugita and H. Ito, "Mass measuring instrument for use under microgravity conditions", Rev. Sci. Instrum., Vol.79, No.5, 056105-1-3, 2008. BMMD

[6] Y. Fujii, K. Shimada and K. Maru, "Instrument for Measuring the Body Mass of Astronauts under Microgravity Conditions", Microgravity Science and Technology, Vol. 22, No. 1, pp. 115-121, 2010. BMMD

Russian BMMDSpring-mass system

Movement of the body is observed.Body is not rigid during the measurement.

GC

Measurementpoint

Skylab BMMD

Rigid Object(0-100 kg)RMS 0.02kg!(0.02%)

Spring-mass system

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“Space Scale” for Astronaut Mass Measurement

Y. Fujii and K. Shimada, "Instrument for measuring the mass of an astronaut", Meas. Sci. Technol., Vol.17, No.10, pp.2705-2710, 2006.

Feature: Use of a rubber code

Expected advantages:Long measurement length→ Reduce the effect of the change of the relative position of GC to the measurement point

Portable and compact size

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“Space Scale” for Astronaut Mass Measurement

Astronaut ( 　mO) Base

Frame of the space station

Belt for holding the instrument to the astronaut

Base

Bungee cord

Force transducerRigid bar

Hinge joint

Optical interferometer and data processing unit

Signal laser beam of the optical interferometer

Cube corner prism

Main part of the Space Scale

Target part of the Space Scale

m = F/a

Y. Fujii and K. Shimada, "Instrument for measuring the mass of an astronaut", Meas. Sci. Technol., Vol.17, No.10, pp.2705-2710, 2006.

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Flight experiment procedureParabolic flight test procedure

Gulfstream II jet parabola profile

JEM-Pressurized ModuleInternal D = 4.2 mL = 11.2 m

Gulfstream II jet airplaneInternal D = 2.2 mExperiment space L = 6.5 m

H = 175 cm

Japanese experimental module is bigger than the jet cabin.

Zero-gravity = 10+ seconds

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Acceleration field

Typical acceleration (G) quality onboard Gulfstream II jet during parabolic flight [Fukushima]

Large residual acceleration field exists.Experimental condition is far from “zero gravity”.ISS: 10-5 ～ 10-6 g

Acceleration conditions

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SPACE SCALE design for Parabolic Flight Test

Y. Fujii, K. Shimada, M. Yokota, S. Hashimoto, Y. Sugita and H. Ito, "Mass measuring instrument for use under microgravity conditions", Rev. Sci. Instrum., Vol.79, No.5, 056105-1-3, 2008.

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SPACE SCALE design for Parabolic Flight Test

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SPACE SCALE design for Parabolic Flight Test

Even during the zero-gravity phase of a parabolic flight, the acceleration vector of the aircraft varies with an amplitude on the order of mG.

In addition, there are the typical jet airplane sounds, noise, and vibration.

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SPACE SCALE design for Parabolic Flight Test

In order to make the prototype work properly on the business jet, some modifications were made to the original design:

(3) Y. Fujii and K. Shimada, “Instrument for measuring the mass of an astronaut”, Meas. Sci. Technol., Vol.17, No.10, pp.2705-2710, 2006.(4) Y. Fujii and K. Shimada, “The space scale: An Instrument for astronaut mass measurement”, T. Jpn. Soc. Aeronaut. Space Sci., Vol. 50, No. 170, pp.251-257, 2007.

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SPACE SCALE design for Parabolic Flight Test

The major modifications are as follows.

(1) The main body of the Space Scale is attached to the base (instead of on the side of an astronaut) and the signal beam is manually aimed at the cube corner prism (CC) attached to the target object by the first experimenter.

(2) The target object is manually released by the second experimenter. Third, a novel signal processing technique for estimating the Doppler shift frequency from the digitized waveform is introduced.

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Parabolic Flight by jet can simulate 25 seconds of microgravity

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1st experimenter

2nd experimenter

After the 0G phase begins in a parabolic trajectory, the first experimenter makes an announcement when he has set the laser beam onto the target object CC.

Objectflying

3rd experimenter

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1st experimenter

2nd experimenter

The third experimenter then starts the measurement system, followed by the second experimenter releasing the target object.

Objectflying

3rd experimenter

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1st experimenter

2nd experimenter

During the measurement, the first experimenter stabilizes the laser beam on the CC of the moving target object to acquire the interference signal.

For beam aiming, a large beam diameter is required to easily make adjustments to the laser beam’s path to the target CC.

Objectflying

3rd experimenter

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Rubber cord

Objectflying

2nd experimenter

The mass of the metal target object is evaluated using the prototype Space Scale on each parabolic trajectory.

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Our latest SPACE SCALE package for Parabolic Flight Test

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Velocity v of the object

measured using the optical

interferometer

Force F applied to the object

measured using the force

transducer

Residual acceleration of

the aircraft aframe,x along

the mass movement direction

measured using the

accelerometer.

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In the experiment run shown in figure, 4020 plots of velocity were obtained.

The first plot is (t1, v1) = (0.888s, 0.464m/s) and the final plot is (t2, v2) =

(1.580s, 1.066m/s).

The velocity change during the period between t1 and t2 (△t = t2 - t1 = 0.692s) is

△v = v2 - v1 = 0.603m/s.

The analysis is conducted for the period for which velocity data is available.

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The velocity change of the frame of the aircraft along the movement direction △vframe = = -1.0 x 10-2 , corresponding to -1.7 % of the velocity change of the

mass between t1 and t2, △v = 0.603m/s.

Therefore, the velocity change of the mass versus the inertial system is calculated as △vinertial = △v +△vframe = 0.592m/s.

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The impulse applied to the subject mass between t1 and t2 is approximately

5.43Ns.

Therefore, the mass of the target object is estimated as Mmeas = / △vinertial =

9.17kg.

The measurement error Er is calculated as Er = Mmeas /Mcal – 1 = -0.022 (-2.2%).

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Relative measurement error Er versus the impulse for all

12 parabolic experiments

Mean value: -0.003 (-0.3%)

Standard deviation: 0.021 (2.1%)

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Setup for measuring body mass

BaseBase

CC

Rubber cordForce transducer

Hinge joint

Safety rope

Astronaut

He-Ne Lazer

PD

Body of Space Scale Handle

CCNPBS

Convex lens

Beam expander

Signal Beam

Computer

Digitizer

GPIB board

DMM

PCI bus

AMP

Ｘ

Ｙ

Ｚ

Y. Fujii, K. Shimada and K. Maru, "Instrument for Measuring the Body Mass of Astronauts under Microgravity Conditions", Microgravity Science and Technology, Vol. 22, No. 1, pp. 115-121, 2010.

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Measurement of body mass

Body mass ：M=93.3 [kg

2rd Experimenter

Subject

1st Experimenter

3rd Experimenter

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bungee safety tether

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Uncertainty Evaluation

The standard deviation of Er 0.021 (2.1%) and the mean value of Er -0.003 (-0.3%) can be considered as the random error and the systematic error, respectively.

On the other hand, the relative standard uncertainty for calibrating the target mass is negligible (0.01%).

Therefore, the relative standard uncertainty of the mass estimated using data from a single sliding measurement is estimated to be 0.021 (2.1%).

As the mean value of the relative measurement error is much smaller than the standard deviation, the measurement error can be reduced by conducting multiple measurement runs and averaging the results.

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Discussions

The measurement error is thought to derive mainly from the uncertainty of the noisy acceleration field of the aircraft.

On the ISS, where a stable microgravity environment is available, a measurement uncertainty better than 1% will be easily obtained using the prototype developed.

The developed Space Scale is also suitable for measuring the mass of large objects such as garbage containers and bags.

The total mass of the instrument can be made as small as 1kg by introducing a laser diode interferometer, a small force transducer, and a digital signal-processing unit.