Byers, Terry

Cardenas, Francisco

Cintala, Mark J.

Montes, Roland

See, Thomas H.

NASA Technical Reports Server

Experimental Impact Laboratory
Mark J. Cintala, Terry Byers, Francisco Cardenas, 
Roland Montes, and Thomas H. See
Along with a variety of support equipment (see
the box in the lower right), the EIL comprises three
accelerators, each of which launches its projectiles
into a vacuum chamber, has its own velocity‐
measurement lasers and electronics, and can be
configured for a wide range of experimentation.
Flat‐Plate Accelerator Vertical Gun Light‐Gas Gun
The FPA is a horizontally mounted gun that uses
gunpowder as a propellant to launch a projectile – a lexan
cylinders, 25 mm in diameter, tipped with a flat, metal
plate ‐‐ at a small, typically geologic sample. A shock‐
reverberation process raises the pressure “felt” by the
impacted sample to a level much higher than that caused
by the simple impact alone.
The vertical gun uses gunpowder in standard rifle shells as
a propellant to launch projectiles as large as .30 caliber at
a wide variety of targets. Because its projectiles travel
straight down (hence its name), targets can range from
strengthless materials, like sand, to solid rock, which can
be used to simulate asteroids. The impact chamber of the
vertical gun can be refrigerated, permitting the use of ice
as a target material.
The LGG uses gunpowder to compress hydrogen gas to
extremely high pressures. When that pressure exceeds
the strength of a rupture disk, the disk breaks in a
controlled way and the hot hydrogen escapes through the
hole, pushing the projectile ahead of it. Launch speeds
can approach 8 km/s. Projectiles can range from 5.56‐mm
(about 0.22”) down to 1 µm in diameter (roughly the size
of a bacterium).
These are typical components of a target assembly,
including the sample itself (the small disk). The sample is
held in the three smaller parts, which get pressed into the
large, cylindrical holder on the left.
Glass spheres 50 µm across (about as wide as a human
hair) made these tracks in a three‐layer aerogel target
when they impacted at 6 km/s. Remnants of one of the
particles can be seen at the end of the track in the center
of the right edge. Experiments like this were performed
during development and testing of the Stardust aerogel,
which ultimately captured cometary dust.
The projectile must impact the target with its front
parallel, or nearly so, to the face of the target. This is
determined by photographing the projectile in flight and
measuring its tilt in two photographs, taken 90° from each
other.
A capability afforded by the vertical gun is the
measurement of ejection velocities from craters formed in
granular, strengthless targets, like sand.
An example of a picture taken during the impact of a 3.2
mm (1/8”) glass sphere into a coarse sand at 2.45 km/s.
A similar system can be
used to observe the
growth of the crater below
the surface as it happens.
Sequence of high‐speed video frames documenting the
growth of an impact crater in the laboratory. Numbers
indicate milliseconds after impact.
The LGG is capable of duplicating impact conditions in the
asteroid belt. As an example, this powdered gabbro (a
dark, igneous rock often polished and used for kitchen
counters) was impacted with a ceramic sphere (shown for
scale) at 5.5 km/s, fast enough to melt a large fraction of
the rock. Such impact melts could be important
components of asteroid soils.
A stainless‐steel target 
assembly after impact.  
The sample is still 
contained in the smaller 
sample assembly; it will 
be mounted in a lathe, 
excess metal will be 
machined away, and the 
sample recovered for a 
variety of possible 
analyses.
EIL operations are very intensive and varied, with each 
set of experiments having its own, often unique, set of 
requirements.  Support for these projects must be 
equally flexible, so the EIL includes a machine shop, 
controlling and sequencing computers, analytical 
electronics, and a walk‐in freezer for cold target 
preparation and post‐shot analyses.  Analytical work in 
support of operations is conducted with scales and 
analytical balances, a Chatillon force‐measurement 
stand, a 3D laser scanner, and an optical binocular 
microscope.
https://ntrs.nasa.gov/search.jsp?R=20140017122 2019-08-31T15:01:27+00:00Z


Experimental Impact Laboratory

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server