AttAttenuation
ti ratet off stresstwave ini sinteredi t dandd nonnon--sinteredid glass
glbeadsb d targets
g
1M SetohM.

11Y Yamashita A.M.
Y.
A M Nakamura
Nakam ra2
P MichelP.

(1 Graduate((1:G dSSchoolh l off S
Science,i,KKobeb UUniversity,ii y, 22:ObservatoireOOb
i ded lla C
Cote d'Ad'Azur )Abstract

Porous structure is common in asteroids and satellites of the outer planets.
pplanets
evolution
To study the relationship between the structure of small bodies and their thermal and collisional evolution,
we performed experimental series about the attenuation rate of stress wave in porous small bodies quantitatively.
quantitatively
We found in the results of our experiments using sintered glass beads and rubble-pilerubble pile glass beads powderthat the antipodal
ejectavelocities
fromthe impact
point
i
j
i i have simileri i dependencies
i on the distanceifi
idtte u tio rate
te w
2.
andd ththee power
powe llaw
w iindex
de ofof ththee attenuation
wass -2.

1 : Background3 : Results

PPorousstructures
t t
are b
believedli d tto b
be common iin smallll bodies.
b diex asteroidsex.
asteroids, Kuiper
Kuiper-belt
belt objects
objects.

Antipodal ejection velocities were measured by highhigh-speed
speed video images
andd are normalized
li d with
ith theth projectile
p j til velocities.
l iti
sintered disk (thickness about 26mm)

Laboratory impact experiments into porous objects have asignificance for studying origins and collisional evolution.

acrylic cylinder
fill d withfilled
ith beadsb dThis studyThit dy investigate
itig t theth relationshipl ti hip between
b tattenuation
tt
ti
rate and internal structure of small bodies quantitatively
qy
Initial peak pressure↓↓ (attenuation)
Antipodal pressure

・Destruction
D t ti strength
t gth off P
Porous b
bodiesdi・Possibility
y of ejection
jofregolith particles and boulders from the surface

configuration of powder targets

high-speed
g pvideo images

aluminum foilwith
ith a hhole
lprojectile
breakthroughinto the paper

1 09
1.09msacrylicy p
plate

Antipodal ejecta jet out fromth hl off aluminuml if iltheholefoil.

★Glass beads were stable due to frictional force.

2 : Target
g and experimental
pprocedurespWe conducted
Wd t d fivefi typest
off experiments
it forf glassl
b d targets
beadtt
using light
light-gas
gas gun and two
two-stagestage light
light-gas
gas gun.
Samples are soda lime glass beads of 50 micron diameter,
nominal density is 2.5
2 5 g/cm3 and melting point is 734 ℃.
compressive
pstrengthg of each particle
pis about 850 MPa.
The following
g table shows the experimental
pconditions.

Targetg
porosity

Impactpvelocity

condition

Grain size(micron)

39%

High

Sintered

5039%

Low

Sintered

5032%

High

Sintered

5041%

Low

Powder5041%

Low

Powder50060%L
Low

P d
Powder591%

Low

Powder5-50
550 (hollow)

41%

High

Powder50

Targetg shapep((Consistinggg
grain size))

porositypyCompressivep
Impactpvelocity
ystrengthg ((MPa)) ((m/s))

Ex. I

Sintered disk（50µm）

39 %2Low(190～262)
Low(190262)

Ex II
Ex.

Sintered disk（50µm）

39 %2High(1700～2080)

Ex. III

Sintereddisk（50µm）
S
te ed ds （50µ ）32 %40High(1900～3390)
g ( 900 3390)

Slope ～ -2
No difference between sintered and powder targets

50 500µm
50,41％

5µmµ60％**Low(257～282)()

Th
The reason whyh th
the result
lt off th
the hihigher
h porosity
it ttargets
t are plottedl tt d abovebypthe others is myabethat what we measured was not the antipodal
ejection velocity due to the stress wave but just projectile velocity.

hollo beads
hollow

91％**High(2380～3800)
g ( 380 3800)

Ex. IV
Ex. V

PowderPowderSintered41 %P d (rubblePowder(rubble-pile)( bbl pile)il )4 : Summary and Next
● The attenuation rates of ejection velocity were
found to be similar and about 2,
2 despite of different
impact velocity and different target condition.
condition●Next●
Next step is to investigate the attenuation rateof stress wave of more porous targets, quantitatively.

SEM images ×600