Dr. David Finkleman (Center for Space Standards and Innovation; Analytical Graphics, Inc.), Daniel L. Oltrogge (1Earth Research, LLC)
Keywords: Iridium, Cosmos Collision
Abstract:
The objective of this paper is to expose the spectrum of satellite breakup physics and is implications for debris production and observables.
Satellite response to the debris environment generally emphasizes small scale hypervelocity impact or the interaction of intense, coherent radiation with satellite surfaces or internals. There are empirical correlations of fragment size distributions based on arena tests and extremely rare observations of breakups in space. Klinkrad describes well research on material response to hypervelocity impact such as the ballistic limit for various materials and shielding walls. Smirnov, et. al., report well the phenomenology of breakups under the influence of nonuniform internal loading of monolithic bodies, such as pressurized tanks. They set forth the transformation of elastic energy into fragment kinetic energy. They establish a sound physical framework for bounding the number of fragments. We took advantage of these works in our previous papers.
There is not much research into the response of nonuniform structures to hypervelocity collisions with similarly massive and complex objects. This work generally employs complex hydrodynamic and finite element computation that is not well suited to real time, operational assessment of the consequences of such encounters. We hope to diminish the void between the extremes of microscopic impact and complex hydrocodes.
Our previous reports employed the framework established by Chobotov and Spencer, fundamentally equilibrium, Newtonian approach. We now explore the spectrum of interactions and debris evolutions possible with realistic combinations of these theories.
The spectrum encompasses Newtonian, semi-elastic energy and momentum transfer through little or no momentum exchange and from virtually all of the mass of the colliders being involved through fractional mass involvement. We observe that the more Newtonian outcomes do not agree well with sparse observations of the few collisions that have occurred in space at high relative velocities.
High speed images of collisions such as the Delta 183 intercept reveal that the objects appear to pass through each other, emerging as a collection of fragments that then disperse with diverse particular velocities under the influence of gravitation and other astrodynamic forces. We previously introduced the concept of partial involvement in which the portions of the colliders that do not make intimate contact tear off, retaining their parent momenta and subsequently fragmenting as elastic energy is released. We now conjecture that the duration of the collision is so short (fractional milliseconds) that stress waves cannot propagate within the involved portions either, and that the involved masses fragment inertially, each fragment inheriting the velocity of the parent object rather than the involved masses evolving about the vector sum of collider parent masses. We call this ghosting. We also observe that ghosted outcomes appear in aggregate to match much more closely observed outcomes, particularly that of the recent Iridium 33 Cosmos 2251 event.
We will discuss the range of outcomes we predict over the spectrum of interaction and fragmentation models. We will examine how the range of outcomes might affect fragment size, mass, and trajectory evolution, with implications for what might be observable and where the less observable fragments might reside.
Date of Conference: September 1-4. 2009
Track: Iridium/Cosmos Collision