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Shock TubesInteraction on Meteorites
Hypersonic Meteoroid Entry Physics,61st Course of the International School of Quantum Electronics
Ettore Majorana Foundation and Centre for Scientific Culture,
3–8 October 2017, Erice, Italy
M. Lino da Silva1, A. Smith2, A. Chikhaoui3, L. Marraffa4, R.Rodrigues1, M. Castela1, R. Gomes1, B. Carvalho1, L. L. Alves1
and B. Goncalves1
(1): Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa
(2): Fluid Gravity Engineering
(3): Univesité de Provence
(4): European Space Agency, European Science and Technology Center
Introduction
Motivation
Meteorites enter Earth’s atmosphere between 11km/s and 72km/s
Shock-Tubes can reproduce the conditions of an atmospheric entry with the highest
degree of physical fidelity. However...Shock-Tubes are impulsive facilities, with a very limited test time (∼ 10−6s)Reaching superorbital speeds is notably difficult from an engineeringstandpoint
Mario Lino da Silva Shock Tubes 4th Oct. 2017 2 / 34
Introduction
Motivation
Meteorites enter Earth’s atmosphere between 11km/s and 72km/s
Shock-Tubes can reproduce the conditions of an atmospheric entry with the highest
degree of physical fidelity. However...Shock-Tubes are impulsive facilities, with a very limited test time (∼ 10−6s)Reaching superorbital speeds is notably difficult from an engineeringstandpoint
Mario Lino da Silva Shock Tubes 4th Oct. 2017 2 / 34
Introduction
Motivation
Meteorites enter Earth’s atmosphere between 11km/s and 72km/s
Shock-Tubes can reproduce the conditions of an atmospheric entry with the highest
degree of physical fidelity. However...Shock-Tubes are impulsive facilities, with a very limited test time (∼ 10−6s)Reaching superorbital speeds is notably difficult from an engineeringstandpoint
Mario Lino da Silva Shock Tubes 4th Oct. 2017 2 / 34
Introduction
Motivation
Meteorites enter Earth’s atmosphere between 11km/s and 72km/s
Shock-Tubes can reproduce the conditions of an atmospheric entry with the highest
degree of physical fidelity. However...Shock-Tubes are impulsive facilities, with a very limited test time (∼ 10−6s)Reaching superorbital speeds is notably difficult from an engineeringstandpoint
Mario Lino da Silva Shock Tubes 4th Oct. 2017 2 / 34
Introduction Outline
Outline of this talk
1 Describe the design strategy for a superorbital shock-tube, including physical modelsand design/engineering approaches
2 Present a sample case-study, outlining its detailed design and choice of technologies3 Discuss the possible configurations for the study of Meteor Entry physics in such
facilities
We will present the ESTHER Shock-Tube as a typical “case-study” facility for the simulationof superorbital, high-speed entries (>11km/s).
Mario Lino da Silva Shock Tubes 4th Oct. 2017 3 / 34
Introduction Outline
Outline of this talk
1 Describe the design strategy for a superorbital shock-tube, including physical modelsand design/engineering approaches
2 Present a sample case-study, outlining its detailed design and choice of technologies3 Discuss the possible configurations for the study of Meteor Entry physics in such
facilities
We will present the ESTHER Shock-Tube as a typical “case-study” facility for the simulationof superorbital, high-speed entries (>11km/s).
Mario Lino da Silva Shock Tubes 4th Oct. 2017 3 / 34
Introduction Outline
Outline of this talk
1 Describe the design strategy for a superorbital shock-tube, including physical modelsand design/engineering approaches
2 Present a sample case-study, outlining its detailed design and choice of technologies3 Discuss the possible configurations for the study of Meteor Entry physics in such
facilities
We will present the ESTHER Shock-Tube as a typical “case-study” facility for the simulationof superorbital, high-speed entries (>11km/s).
Mario Lino da Silva Shock Tubes 4th Oct. 2017 3 / 34
Introduction Outline
Outline of this talk
1 Describe the design strategy for a superorbital shock-tube, including physical modelsand design/engineering approaches
2 Present a sample case-study, outlining its detailed design and choice of technologies3 Discuss the possible configurations for the study of Meteor Entry physics in such
facilities
We will present the ESTHER Shock-Tube as a typical “case-study” facility for the simulationof superorbital, high-speed entries (>11km/s).
Mario Lino da Silva Shock Tubes 4th Oct. 2017 3 / 34
Shock-Tube Design
Conceptual Design
Requirement driver: reaching high-speed shocks (v>10km/s)
High shock speeds can be reached on a first approach for large driver/test section(HP/LP) ratios. Some practical limitations (p, T, mixture) exist
Some extra performance can be achieved for a variable (A1/A4 >1) area ratiobetween the HP and LP sections (up to 20%)
single-stage variable area shock-tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 4 / 34
Shock-Tube Design
Conceptual Design
Requirement driver: reaching high-speed shocks (v>10km/s)
High shock speeds can be reached on a first approach for large driver/test section(HP/LP) ratios. Some practical limitations (p, T, mixture) exist
Some extra performance can be achieved for a variable (A1/A4 >1) area ratiobetween the HP and LP sections (up to 20%)
More significant performance enhancements can only be achieved if we add anintermediary section
two-stage variable area shock-tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 4 / 34
Shock-Tube Design
Basic Design Concepts for Maximizing Shock-Tube Performance
1 Thermodynamic design of the driver
2 Shock-Tube cross-section optimization
3 Second stage compression tube optimization
Mario Lino da Silva Shock Tubes 4th Oct. 2017 5 / 34
Shock-Tube Design Thermodynamics of Shock-Tube Driver Design
Thermodynamic Design of the Shock-TubeDriver
Mario Lino da Silva Shock Tubes 4th Oct. 2017 6 / 34
Shock-Tube Design Thermodynamics of Shock-Tube Driver Design
Thermodynamics
Shock-Tube equation
P4P1
=P2P1
1 − (γ4−1) a1a4
(P2P1−1
)√
2γ1
√2γ1+(γ1+1)
(P2P1−1
)−
2γ4γ4−1
Maximization of test section shock speed (a4)for a given initial pressure (P2, imposed), relieson driver parameters: large driver pressure P1,large sound speed V1
s and low γ1
Imposes the selection of a low molecular weigthdriver gas: H2 would be ideal but safety issuesexist, also detrimental effect on γ due to themolecular internal modes
Alternative is using He. Most of Shock-Tubesrely on this gas
Compression of driver gas (piston, combustion, electric arc) increases T, which is beneficial forV1
s . Necessity to compute γ1 values at high p,T
Mario Lino da Silva Shock Tubes 4th Oct. 2017 7 / 34
Shock-Tube Design Variable-Area Shock-Tube Design
Performance of a Variable-Area Shock-Tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 8 / 34
Shock-Tube Design Variable-Area Shock-Tube Design
Shock Relations for Constant and Variable Area Shock-Tubes (1/2)
Classical Shock-Tube equation for constant area (A4/A1 = 1) is:
P4P1
=P2P1
1 −(γ4 − 1) a1
a4
(P2P1− 1
)√
2γ1
√2γ1 + (γ1 + 1)
(P2P1− 1
)−
2γ4γ4−1
(1)
For variable area (A4/A1 , 1) we consider the Alpher and White1 approach, considering an “equivalence” factor g asdefined by Resler 2 .
For a variable area:
A4A1
=MeM3a
2 + (γ4 − 1)M23a
2 + (γ4 − 1)M2e
γ4+1
2(γ4−1
)(2)
Since we are in the supersonic case, we have Me = 1. We may then determine M3a iteratively.
We then solve for the “equivalence” factor g as defined from Resler:
g =
√√
2 + (γ4 − 1)M23a
2 + (γ4 − 1)M2e
[2 + (γ4 − 1)Me2 + (γ4 − 1)M3a
]2γ4γ4−1
(3)
Mario Lino da Silva Shock Tubes 4th Oct. 2017 9 / 34
Shock-Tube Design Variable-Area Shock-Tube Design
Shock Relations for Constant and Variable Area Shock-Tubes (2/2)
We can then use the modified Shock-Tube equation for a variable area ratio:
P4P1
=P2P1
g−1
1 − u2a1
a1a4
γ4 − 12
g−γ4−12γ4
−
2γ4γ4−1
(4)
where we have:
a1u2
=γ1 + 1
2Ms
M2s − 1
(5)
with the shock-speed Ms defined as a function of P2/P1
Ms =
√γ1 − 1
2γ1
(1 +
γ1 + 1γ1 − 1
P2P1
); (6)
We may finally solve solve the variable area Shock-Tube equation (Eq. 4) iteratively in a similar fashion to the constantarea Shock-Tube equation (Eq. 1).
Mario Lino da Silva Shock Tubes 4th Oct. 2017 10 / 34
Shock-Tube Design Two-Stage Shock-Tube Design
Performance of a Two-stage Shock-Tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 11 / 34
Shock-Tube Design Two-Stage Shock-Tube Design
Shock Diagram for a Two-Stage Shock-Tube
Two-stage configurations allow for higher shock speeds at the cost of decreasedrun-times (due to faster contact waves)
Optimization parameters for second stage: Gas composition (always He andpressure p)
Mario Lino da Silva Shock Tubes 4th Oct. 2017 12 / 34
Shock-Tube Design Application to the ESTHER Shock-Tube Design
A few examples: Application to the design ofthe ESTHER Shock-Tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 13 / 34
Shock-Tube Design Application to the ESTHER Shock-Tube Design
Optimized Two-Stage Shock-TubeShock velocity dependence on driver pressure
Variable driver pressures from 100 to600bar
Test section for different planetaryconditions (Earth, Mars entry)
Increasing the driver pressure up to600bar yields 2–2.3km/s increase inshock velocity
Test gas pressure can be decreased
below 10Pa but of little relevance:
Too rarefied regime, outsidepeak fluxes regionCollected radiation will beminimal due to the low density
Mario Lino da Silva Shock Tubes 4th Oct. 2017 14 / 34
Shock-Tube Design Application to the ESTHER Shock-Tube Design
Optimized Two-Stage Shock-TubeShock velocity dependence on area ratio
Up to +1km/s can be achieved through avariable area driver/driven section. Needsoptimized diaphragm design
Diminishing returns as the area ratioincreases
Optimization becomes an engineering
problem: How large of a driver can you
afford as a price for extra performance?
Increased material mass, larger wallstresses due to increased diameterMore costs per shot, need to filllarger volumes of driver gas (He isexpensive)Safety issues with large vesselsunder extreme pressures
Mario Lino da Silva Shock Tubes 4th Oct. 2017 15 / 34
Shock-Tube Design Application to the ESTHER Shock-Tube Design
Optimized Two-Stage Shock-TubeTest times calculations
In ideal case, shock goes faster than contact wave, therefore test time increases withdistance of the test section to the diaphragm (see previous slide)
Shock in fact slows down as it progresses and contact wave accelerates untildistance between both reaches a constant value. Boundary layer acts as a mass sinkbetween shock and contact surface
Analysis by Mirels
⇒ H. Mirels, “Test-time in Low-Pressure Shock-Tubes”, Phys. Fluids, Vol. 6, No. 9, Sep. 1963)
Mario Lino da Silva Shock Tubes 4th Oct. 2017 16 / 34
ESTHER Case-Study
Case Study: The new European shock-tube forsuperorbital entries kinetics and radiation:
The ESTHER Shock-Tube
Mario Lino da Silva Shock Tubes 4th Oct. 2017 17 / 34
ESTHER Case-Study
Overview of ESA’s European Shock-Tube for High Enthalpy Research
Facility developed by an international consortium led by the IST of Lisbon, underfunding from the European Space Agency. Support to future European planetaryexploration missionsTwo-Stage combustion-driven (He/H2/O2 mixture) shock-tube. Laser ignition (1st
facility of its kind)High Pressure (HP) section: 60–600+bar, Mid Pressure (MP) section: 0.1–0.5bar,Low Pressure (LP) section: 10–0.1mbarVariable area cross-section: HP: 200mm∅, MP: 130mm∅, LP: 80mm∅Hydraulics system for sections closureBraking system ensures adequate shock-tube stiffnessPrimary and turbomolecular pump system for ensuring vacuum down to 10−6 mbar inthe test section.
Mario Lino da Silva Shock Tubes 4th Oct. 2017 18 / 34
ESTHER Case-Study
ESTHER Consortium
Mario Lino da Silva Shock Tubes 4th Oct. 2017 19 / 34
ESTHER Case-Study
Shock-Tube FacilitiesA World outlook
o
ESTHER is a World-class facility
Mario Lino da Silva Shock Tubes 4th Oct. 2017 20 / 34
ESTHER Case-Study
Technological OptionsA comparison of different shock-tube facilities
Driver section technology
Strong recoil Pollution Repeatability PerformanceMoving parts risks in the Driver (high p, T)
Piston (X2, X3) yes no good moderateElectric Arc (NASA EAST) no yes bad excellentComb. Detonation (TH2) no yes moderate / bad excellentComb. Deflagration (ESTHER, VUT-1) no no / yes good good
Test section material
Surface pollution Leakage risks fromfrom Carbon Al2O3 flaking
at the window interfaces
Aluminium (EAST, HVST, X2, X3) no yesSteel (VUT-1) yes noLow-carbon Steel (ESTHER) needs good no
vacuum cleaning
Mario Lino da Silva Shock Tubes 4th Oct. 2017 21 / 34
ESTHER Case-Study
Laser-Ignition DriverA World first
Scaled combustion chamber installed forproof-of-concept
First configuration included an axialconstantan hotwire for radial ignition
Issues related to wire pollution andbreakage of ceramic insulators in case ofdetonation
We successfully applied a laser ignitionsystem to the bombe
No parts inside the driver, no pollution fromwire residues
Very good repeatability reached with nodetonations. Maximum pressure: 610bar: Aworld record for laser ignition
Ignition threshold: 108W/cm2 forp>20–30bar. Two orders of magnitudebelow minimum ignition values from theliterature. Effect of impurities/dust?Mario Lino da Silva Shock Tubes 4th Oct. 2017 22 / 34
ESTHER Case-Study
The Challenge of a Lifetime
Mario Lino da Silva Shock Tubes 4th Oct. 2017 23 / 34
ESTHER Case-Study
The Challenge of a LifetimeCurrent Status: Bench assembled and aligned
Mario Lino da Silva Shock Tubes 4th Oct. 2017 24 / 34
Meteroroid Entry Physics Studies
Ablation Studies in Impulsive Facilities
A Few Examples
Mario Lino da Silva Shock Tubes 4th Oct. 2017 25 / 34
Meteroroid Entry Physics Studies
Ablation Studies in Shock-Tube FacilitiesCase-Studies from the University of Queensland
University of Queensland (Australia) operates several superorbitalshock-tube facilities in wind-tunnel mode (X2, X3)
UQ has been pioneering Ablation studies in such facilities, demonstratingthe viability of impulsive facilities for materials testing
We will discuss a few recent experiments that are highly relevant for meteorentry physics
Mario Lino da Silva Shock Tubes 4th Oct. 2017 26 / 34
Meteroroid Entry Physics Studies
Experimental setup for the X2 Expansion Tube
Expansion shock-tube X2
Diagnostics setup includes a fast iCCDcamera and a VUV-capable spectrograph
S. W. Lewis et al. “Expansion Tunnel Experiments of Earth Reentry Flow with Surface Ablation”,
J. Spacecraft Rockets, Vol. 53, 2016, pp. 887–899. T. N. Eichmann, “Radiation measurements in a simulated Mars atmosphere”,
PhD Thesis, University of Queensland, 2012.
Mario Lino da Silva Shock Tubes 4th Oct. 2017 27 / 34
Meteroroid Entry Physics Studies
Heat-Fluxes at Stagnation PointAnalytical estimates and spectra from epoxy coating ablation on the X2 expansion tube
Stagnation heat-flux approximation from Zobya
qs = Ki
√ρu2 u2√reff
Shultz and Jonesb T change for constant heat flux
∆Ts = 2qs√π
√tρck
and 10%, 1% step function thermal pulse penetration depth
x = 2x∗√αt
x = 0.3√
t
Experiment from D’Souza, showing ablation of an epoxy coatingover a model: ∆T=178K with 10% T penetration depth of 6µm in50µs.
aE. Zoby, “Empirical Stagnation-Point Heat-Transfer Relationin Several Gas Mixtures at High Enthalpy Levels,” NASA TND-4799, 1968.
bD. L. Schultz, and T. V. Jones, “Heat-Transfer Measurementsin Short-Duration Hypersonic Facilities,” AGARD AGARDographAG–165, 1973.
M. G. D’Soza et al., “Observation of an Ablating Surface in Expansion Tunnel Flow ”,
AIAA Journal,Vol. 48, No. 7, 2010, pp. 1557–1561.
Mario Lino da Silva Shock Tubes 4th Oct. 2017 28 / 34
Meteroroid Entry Physics Studies
Ablation of a Preheated Carbon StructureExperiment in the X2 expansion shock-tunnel
Preheating of a carbon sample toT=2000K, using a copper resistance
Spectral measurements in the near-VUV(350–390nm) and high-spedd imaging byiCCD camera
Excess C and CN radiation measured inthe flow. Ablation products observed by anICCD camera (see figure below, detail A)
F. Zander et al. “Hot-Wall Reentry Testing in Hypersonic Impulse Facilities”,
AIAA Journal, Vol. 51, No. 2, 2013, pp. 476–484.
F. Zander et al. “Hot-Wall Reentry Testing in Hypersonic Impulse Facilities”, AIAA Journal, Vol. 51, No. 2, 2013, pp. 476–484.
Mario Lino da Silva Shock Tubes 4th Oct. 2017 29 / 34
Meteroroid Entry Physics Studies
Frozen Post-Shock FlowsWedge insertion in a shock-tunnel flow (X2 and EAST)
Sangdi Gu et al., “Study of the Afterbody Radiation during Mars Entry in an Expansion Tube”, AIAA paper 2017–0212, 2017
Comparison between experimental data using iCCD cameras and CFD simulations
Sangdi showed (in Mars entry conditions) that inserting a wedge leads to thefreezing of the flow behind the oblique shock
More investigations needed, but this could relevant for meteor wake radiationreproduction
Mario Lino da Silva Shock Tubes 4th Oct. 2017 30 / 34
Conclusions
Conclusions
Mario Lino da Silva Shock Tubes 4th Oct. 2017 31 / 34
Conclusions
Conclusions
Shock-Tubes are at the performance limit for meteor studies. Facilitiesranging from 11–14km/s should nevertheless suffice for understanding theµ of meteor entry thermophysics
They provide the most realistic conditions of an atmospheric entry but thelimited test run times (a few 10’s of µs) constitute significant challenges
VUV radiation is key owing to the superorbital entry regime⇒ Furtherchallenges related to the deployment of VUV rated diagnostics
Mario Lino da Silva Shock Tubes 4th Oct. 2017 32 / 34
Conclusions
In memory of Prof. Michel Dudeck (1945–2017)
Mario Lino da Silva Shock Tubes 4th Oct. 2017 33 / 34
Mario Lino da Silva Shock Tubes 4th Oct. 2017 34 / 34