Physical simulation of meteoroid and space debris particles influence on spacecraft construction elements

Ira. ,L Imtmct Engng, Vol. ~7, pp. 539 545, 1995 Copyright i , 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0734-743X/95 $9.50+0.00

Pergamon

PHYSICAL SIMULATION OF METEOROID AND SPACE DEBRIS PARTICLES INFLUENCE ON SPACECRAFT CONSTRUCTION ELEMENTS Leonid.G. Lukashev

Samara State Aerospace University, 34, Moskovskoe Shosse, Samara, 443086, Russia Summary Three methods of physical simulation of collision with ba'.riers of meteoroid particles and space debris are given. The direct method is to accelerate a model particle by means of a gun or a cumulative device. The method of collision simulation by the barrier splinters when the barrier is broken through with a high-speed steel particle, accelerated as before. The method of hydrosimulation is to simulate the particle and the barrier by means of liquid substances. Theoretical foundation of hydrosimulation is given and the results of compairing the crater dimensions obtained by the impact of liquid and solid pairs are discussed. _Theboundaries of hydrosimulation of high-speed impact according to velocities for solid impact pairs are V = 2 - 12 km/sec and the dimensions ratio are r / r < 3. INTRODUCTION Spacecraft designers must anticipate many space environmental factors which affect the success and usefulness of any given mission. Two of the most important factors affecting the operating conditions and the survival probability of a spacecraft are the meteoroid and space debris flux. Due to the human development of space approximately 3,5 millions of various artificial particles are found at present in the near-Earth space. The danger of spacecraft collision with such particles is increasing. [ 1,2] The meteoroid particles flux crosses the Earth orbit and has the intensity changing while circulating around the Sun. Unlike it the space debris are moving with the Earth and constantly increase the danger of collision with spacecraft. Every such particle is dangerous in itself since it can collide with a spacecraft and is dangerous as a source of new particles that are formed during its collision with other particles. The collision energy is high and can bring about the formation of the numerous fragments too small to be observed by radar-stations ( the particles of more than 10 c m can be observed) but they are large enough to be dangerous for the systems, working in space. The theoretical investigations of high-velocity collision processes are difficult because of the mathematical description of powerful percussion waves and owing to them integration of nonlinear differential equations. During the orbital testing of the meteoroid and space debris effect on spacecraft construction elements the technical and time difficulties appear. All this induces the researchers to simulate the collision processes. In our works the utmost attention is given to the direct methods of physical simulation as well as to the methods using analogies. Direct simulation of high-velocity meteoroid particle effect on spacecraft elements consists of the hypothetical (model) mechanical particle high-velocity collision with spacecraft elements. The parameters of co-impact pairs are maximum approximated to the real conditions (impact velocity, particle mass and density, vacuum etc.) Direct simulation methods give the most real qualitative and quantitative results picture of the particle effect on spacecraft elements. But these methods are fraught with difficulties: high safety engineering requirements, high cost of equipment and research, impact parameters measuring complexity. Direct simulation method of meteoroid particle collision with spacecraft elements at the velocities approximating those of meteoroids can be divided, according to the methods of velocity acquisition into: gun, explosive, by electric discharge, plasmas, electromagnetic, combined. 539

540

L.G. LUKASHEV

This work presents the method of high-velocity impact simulation. The particle was accelerated by gun and explosive methods to the velocities of O,8 - 10 km/s. The meteoroid particles were simulated by compact bodies of various density steel balls, aluminum and glass balls and secondary splinters of screen-target. The velocities of 6 - 1 2 k m / s provide the mentioned acceleration methods for steel particles of 10 g mass. The objects of research simulation are the parameters of typical barrier damage with highvelocity meteoroid particle (meteoroid substance simulating particle for meteoroids, debris-simulating particle for debris). Crater depth H and diameter D , ultimate-penetration of barrier thickness d , the hole diameter D , the character of radial crack appearance and their dimensions can be classified as the typical barrier damage parameters. The aim of high-velocity impact simulation is the investigation of collision physics, of the particle parameters effect on the damage parameters of the barriers, which allows one to choose the material most satisfying for spacecraft construction elements oftne minimum mass. The collision model must be adequate and simple. For simulation of prolonged and complex orbital investigations (meteoroid substance or space debris effect on spacecraft) the direct estimation of adequacy is unattainable at present and is substituted by an indirect one. To substitute for full-scale experiment results, the basic impact model data are to be used. Here the adequacy is treated as the correlation of the aggregate results of two simulation methods - the basic one and the suggested one. GENERAL STATEMENTS High-velocity impact simulation at 0,8-10 km/s velocities is provided by 3 types of installation for particle acceleration: - to velocities of 2,5 km/s by the smooth-barrel powder gun with 23mm internal diameter; to velocities of 5 km/s by two-stage light gas gun using hydrogen, with 23mm internal diameter; - cumulative acceleration to the velocities of 10 km/s. The estimated indexes are: a) The simulation indexes list: particle material; particle density, g/cm ; particle mass, g; - impact velocity, km/s; - barrier material; - barrier density, g/cm ; - barrier thickness, mm; - damage type (crater, hole); crater diameter, mm; - crater depth, mm; radial crack size (if it appears near crater); hole diameter "in light", mm; radial crack size (if it appears near hole); particle fragment size (diameter-averaged distinctive size); splinters velocity after penetration km/s; splinters and fragments dispersion angle. -

-

-

-

-

-

-

-

-

-

-

b) Indexes value determination. The particle and barrier materials and their density and particle mass are chosen while we defme the simulation problem. The impact velocity is also set and is determined during the experiment by 3 methods depending its value and installation type: - the average velocity is determined on a base between two foil and wire transmitters according to the readings of two frequency meters. The latter were switched on when the particle damaged the first transmitter and switched off when the second transmitter was damaged; - the average velocity is determined while the particle passes between two marks drawn by fotoregister lines. Fotoregister acts in the monitoring regime. the average particle velocity was determined at still-by-still shooting by the register. In the last two velocity measuring methods the speed fotoregister SFR-1M is used in both the monitoring and still-by-still regimc,~. -

Physical simulation of meteoroid and space debris particles

541

METHODS OF METEOROID AND SPACE DEBRIS SIMULATION BY THE FORMATION OF HIGH-VELOCITY DAMAGED BARRIER SPLINTERS As previously stated the objects of investigation are the damage parameters of the typical barriers impacted with the high-velocity particles simulating meteoroid and technical particles. Those particles are formed by piercing a screen by a larger high-velocity particle. The objective of meteoroid substance partic!e simulation is the investigation of meteoroid and technical particle collision effect on surface elements of spacecraft construction such as sun battery, optical devices, mounted radiators of thermal control system. Depending on the supposed spacecraft existence period on the orbit, the accumulation of damages, their density as well as particle mass and density distribution are simulated. This method of direct high-velocity impact simulation allows to simulate the barrier damage with a single high density particle or with a particle flux. The experiments of high velocity impact of particles of reX-15 material with a thin barrier show that the damaged area of the barrier foundation consists of two zones: the zone damaged by thin barrier splinters and the zone damaged by particle fragments. The zone damaged by barrier splinters has the larger area than one damaged by particle fragments. But these zones overlap. The high velocity impact tests with inclined screened samples allow to separate screen splinters from particle fragments. The essence of this separation is in the usage of the regularity of splinters and fragments dispersion 9ehind the screen. The experiments show that the splinters spread normally to the screen while the particle fragments spread in the direction of particle flight. It leads to the conclusion that we can obtain two neighboring zones placing the screen at an angle to the ordinary particle trajectory and separating the flows of particle fragments and screen splinters (fig. 1). The usage of such particle separating method allows to simulate meteoroid particles with various densities. Particle density is determined by screen material density. Changing the distance between the screen and the barrier we can change the thickness of particle flow. The debris flux simulation s c h e m e

1 - the plate which is the source of the meteoroidsubstance; 2 - higla-velositymeteoroid flux; 3 - plate debris flux; 4- the membrane;5 - paper of foil for detectiotaof fragment directions; 6 - testitagspeeimen or eotastruetiveelement Figl Given that the mass volume knocked out of the screen equals to the total volume of all splinters weget 26

rd 2 albl al~]~tk = - ~4s

542

L.G. LUKASHEV

where k - corrective ratio accounting for various types of inaccuracies (screen hole diameter, up and lateral discharge charred splinters etc.); d - the first plate thickness; a., b - the greater and the smaller cavity parameters accordingly. Investigation shows that for the experiments k = 1, 0 As a result of the behind-screen damaged field processing a graph of integral mass distribution of splinters is obtained (fig.2). At this graph the lines are traced corresponding to the integral law of meteoroid particle mass-distribution [3] N ( m ) = d m -s (partic'es / m 2 sec 2rt steradian) From this chart it is clear that experimentally obtained splinters mass-distribution is close to those of the sporadic meteoroid particles.

The distribution of fragments o f t h e s c r e e n by

lgN

mass

I

N(ra)=am"s

3 ~,.._

J

-" (theo,y)

•~

exl°e~ent

t,, -8 -7 -6 -.5 N(m)-number of 10articles m-mass of particles

-4

-3

lg ra

Fig2

ANALOGY METHOD OF HIGH-VELOCITY IMPACT SIMULATION (HYDROCODESIMULATION) Hydrocodesimulation used here can be attributed to the analogy method of high-velocity impact simulation. It consists of the replacement of impacted solid pairs by liquid pairs. This method is mostly applied to crater-formation investigations for the samples - imitators of spacecraft elements. Parameters of impact pairs are chosen from the analogy of high-velocity crater-formation in solid environment to the low-velocity crater-formation in liquids. High-velocity impact process can be explained by hydrodynamic theory. At high impact velocities of solid pairs the impact pressure is much larger than the strength of materials so the impact problem can be considered to be hydrodynamic problem for shift-resistant liquids. The lower impact velocity limit for liquid-imitated metal pairs is about 2-3 km/s. While investigating the crater-formation parameters the impact pair materials pressure can be ignored. Percussion wave is supposed to be the main factor of pressuring. Wave velocity in metals is several levels higher than crater-formation speed. The heat effects in turn ,43n't affect the final depth of the crater in half-infinite barrier at velocity o f V < (3-3,5) C , where C - sound velocity in metal (about 1,6 - 6km/s). Thus at the impact velocities of 2 - 8 km/s the solid bodies behavior can be considered much alike ideal non-pressuring liquids and the collision process is not complicated by heat-formation and explosion effects, though some researchers use hydrodynamic model at higher velocities.

Physical simulation of meteoroid and space debris particles

543

High-velocity impact and crater-formation simulation at the velocities of 3-12 km/s is provided at installation that format a drop that falls from the height of 600-800 nun on surface of liquid. The liquid is contained in transparent vessel with coordinate scale. The crater-formation process is fixed by film camera with optical axe coincided with liquid surface. The average velocity of process shooting was 3000-3500 st/s. Taking into account that while solid spherical particle impact solid half-infinite barrier the motion and inseparability equations are -d-~+ i g , u~ u~.4 - - =Vii2 d, 2

1 pl graa~'

L div~=O for particle

(~_,

_~2

--7---i-igroa

=- --

1

gratiS: 2

k div~ = O for half-infinite barrier where V~ and K2 -velocities in particle and bamer impact point; Pl and P2 - part and barrier density correspondingly; D1s and 92 - particle and barrier stress tensors. At the examh ~d velocities ~ = e, + s , , ~ 2 = 72 + s2 where ~ and P2 spherical stress tensor (pressure), ~ and S-2 stress tensor deviator, its components are less than yield limit tre~ and try2 correspondingly. Motion and inseparability equations of spherical drop impact with liquid half-infinity barrier looks like: dl~ .V12 1 -

-~¢ + gr,~aT

= - - - g r a d ( P , + p,g~, )

Pl

div V~ = 0 for drop

v:

{ dl~

1

- a 7 + g ~ " a T = t;~

div~

grad(P2 + p~gz~ )

=0

for liquid where I71 and/72 - drop and liquid impact point velocities,

fi~ and ffz - drop and liquid densities correspondingly, and P2 spherical stress tensor (pressure),

z~ and z2 - vertical point coordinate, g - free-fall acceleration, l". period. Vo~ Considering scale transformation and dividing into d factor we can arrange those equations to dimensionless form and their solution get non-obvious form. The dependent variable quantity is presented as dimensionless parameters function. For solid impact bodies L-, = F ( for liquid impact bodies

VdZO Pl pzV2,pb,pot) 'P2'

er2

544

L.G. LUKASHEV

Lz =¢(Vo~o pl,

C,p~,poL)

d 'P2 gd

where Vo - impact velocity; Pb - two medium boundary pressure; d - particle (drop) diameter; 7:o - period. For similarity and synonymous definition of crater formation laws while spherical solid and liquid particle impact with half-infinite barrier supposing to work as an ideal non-pressuring liquid (I~ = I, ) it is necessary and sufficient to carry out the conditions

P'

P'

[Z],=[Z [ VoT:o a

[

P2V: ]S=[ v: l

Ha

VoT:o d ],[ P' +/4, H2 ]s=[v'+P'z]Lp2 (Pz + 1)s = (P2 +zz )L

-

-

-

-

-

Here the strength characteristic are considered to be like the Brinnel hardness H The simulatk a parameters are: drop diamete,, drop falling height, crater diameter, crater depth, drop fall velocity. Liquid drop diameter is determined indirectly from equation d=

6f~

where m - drop mass, fixed at analytical scales, P~ - drop formatting liquid density. Crater diameter and depth are fixed with microscope from the developed film. The crater formation final moment is 7:o. The vertical crater-formation velocity is equal to 0. Drop fall velocity is determined as e -~/k - 1. V=-gke-~/k + 1 '

_[. 4dpl k ~3Cxp., P~ - liquid drop density, where =

P~ - air density, Cx - sphere (drop) resistance ratio. For the examined Reinolds numbers interval 350 < Re < 2500 Cx can be considered to be constant and equal 0,5. For comparative liquid impact crater depth and diameter the received formulas look like: (d)L-- = 0,82(P~ )o,5( V2)o,2,

7 0 )o,2,withp~< 1,3 ~ P2 /Z,2 ( D ) L = 1,12(P, )o,24( o )o.2,with P___L> 1,3 P2 ~ P2 (

)L = 1 , 4 5 ( P ' ) ° 2 ' ( P2

Physical simulation of meteoroid and space debris particles

545

The dependencies of comparative crater depth upon physical-mechanical characteristics of the impact pairs with spherical particles (drops) are presented at fig. 3.

The dependence of the relative d e p @ i n t k e • . , E' gz liquid emaromueJtt from ~z o and "* H2 gd

solid and .

accordi~ly

D

200 400 600 g00 1-"Fe-AI", "bromform-watet"; 2-"Fe-Fe", "Fe-Cu", "Fe-Pb", 3- "water-water" Fig.3

I000

H2

'gd

The received equations for comparative crater depth and diameter at the impact velocities of 210 km/s look like V2

= o,8(P' )°"( p2 o )0,2,

P2

"----~2"

( D ) s - - , 1, - 2( - , p' ]0'24 (, -p2V02 - , ]0,2, /-/2 In our work, the boundaries of high-velocity impact hydrosimulation usage are established: the P_~L< 3 velocities of solid impact pairs are V0 = 2-12 km/s, the altitude of their densities is P2 REFERENCES 1. Tiny orbiting debris poses danger to spacecraft//Space Age Tins - 1988 2. Debris in space, Fumiss T. "Flight Int.", 1988, 134,N 4124, 28-31 3. Levin B.Yu. Physical theory of meteoroids and meteoroid substance in Solar System / SU Science Academy, 1956