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Improvement of the CISAS high-shot-frequency light-gas gun
Full text linkAbstract
A preliminary version of Two Stage Light Gas Gun for impact testing directly derived from fusion
pellet injectors was built in the CISAS laboratories few years ago. The main purpose of that system
was to have a starting point to develop a new unit expressly dedicated to hypervelocity impacts.
The system has started its development phase in the late '97 and it was fully operative in the late
'99. In that configuration, it was able to accelerate 200 mg at 3.5 km/s and 100 mg at 4 km/s with a
shot frequency between 20-30 shot per day. The system at that point was reliable but the
performances were not good enough for impact testing. A great computation and experimental
work started at that point to improve the gun performances. The main subsystems of the gun have
been completely revised. Extensive numerical simulations have been used to optimise the first
stage, the head and the damping system. Leaving almost unaltered the main geometric
parameters of the original gun, an almost new unit has been developed, building a new fist stage
valve, a new damping system, and a new gun head. The new system has been tested end
experimentally characterised and optimised. In its new configuration, the gun is able to accelerate
100 mg at 5.5 km/s with a shot frequency of (at least) 10 shots per day; some tests show also that
a speed up to 6 km/s with the same shot frequency is reachable. In this paper, the basic gun
configuration and the improvement of each part are discussed
Global model of Hydrogen Discharge
No full textInternal Publication, University of Padova, Reg. Tribunale P
Development of a zero-dimensional numerical model for optimization and diagnostic of gas systems
No full textInternal Publication, University of Padova, .Reg. Tribunale P
Realizzazioni e possibilità di trasferimento tecnologico del centro spaziale dell'università di padova CISAS
No full text
Computer based control and diagnosis of a two stage light-gas gun by means of pressure recordings
No full textDiagnostic Procedure for two stage light gas gun pellet injector
No full textThis work, by means of the numerical modeling of a two-stage light gas gun, analyses deterioration parameters and proposes a procedure for diagnosing functional parameters of two-stage light gas guns with high firing frequency. Analyzed parameters are: piston wear and deformation, delay in first-stage valve opening, and piston seize-up. The procedure was developed by means of gas-dynamic numerical modeling. Experimental tests demonstrate that this procedure can be realistically applie
Implicitly charge-conserving solver for Boltzmann electrons
No full textAn implicitly charge-conserving algorithm has been developed for solving the nonlinear Poisson
equation that results from the use of Boltzmann electrons. The new algorithm solves for the
Boltzmann density parameter and, in the case of a Neumann boundary condition, the surface-charge
density, simultaneously as it solves for the discretized electrostatic potential. Numerical stability is
demonstrated for time steps exceeding the electron plasma period and spatial resolutions much
coarser than the Debye length
A system to damp the free piston oscillations in a two-stage light-gas gun used for hypervelocity impact experiments
Full text linkHypervelocity impact experiments that reproduce on-orbit collisions between micrometeoroids or
orbital debris and space structures are commonly performed by means of propellant-driven twostage
light-gas guns. Such devices accelerate projectiles using the thrust of a light propellant gas
that is compressed to high pressure and temperature by a piston running in a pump tube. Though
these guns have the unique capability of accelerating particles up to 9 km/s, many components of
the gun must be checked and/or substituted after each shot making test sessions long and
expensive. In order to have a lot of and many different types of hypervelocity impact data, the
Center of Studies and activities for Space CISAS ”G. Colombo” of Padua University developed a
high-shot-frequency two-stage light-gas gun that can increase the shot repetition rate of standard
facilities by a factor of 5 or more and at the same time reduce the shot cost by a factor of 2 or
more. This is made possible through the use of special mechanical and diagnostic solutions that
were designed to operate the gun for more than 50 shots in sequence without having to carry out
maintenance operations. This article presents the design and operation of the CISAS two-stage
light-gas gun damping system, which is one of the subsystems that makes it possible to achieve
high-shot frequency. The damping system is in charge of controlling the piston oscillations in the
pump tube, making it possible for the piston to withstand more than 100 shots without any damage.
In particular, the damping system avoids piston strikes onto the gun head at the end of each
compression stroke and allows the piston to be positioned at the base of the pump tube after each
shot. The sensitivity of the piston oscillations to the damping operations and main subsystem
design parameters were identified using numerical simulations, carried out according to a model
that describes every working phase of the gun. Moreover, in this paper, the technical solutions for
the damping system implementation are presented and the numerical predictions are compared
with experimental results. For the CISAS high-shot-frequency gas gun, an efficient damping
system proved to be a fundamental requirement to reliably accelerate 100 mg projectiles above 5
km/s and 70 mg projectiles at 5.5 km/s with a shot frequency of 10 shots per day at least, including
the time needed for replacing the target and pumping down the target vacuum chamber
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