Speaker
Description
The Orbiting Dust Impact Experiment (ODIE) is a dedicated, retrievable, passive dust collector, designed to be placed on, for example, the outside of the International Space Station to facilitate the investigation of the flux and origin (orbital debris OD vs micrometeoroid MM), of dust particles in Low Earth Orbit (LEO). ODIE is comprised of multiple layers of polymer foils that act in much the same way as a Whipple shield: the initial foil(s) disrupt the impactor, spreading its energy over a larger surface and capturing multiple lower speed fragments on subsequent foils. Polymer foils used in multi-layer insulation exposed to LEO have been found to capture and retain substantial quantities of easily identifiable residue that may be analysed to determine chemistry, and thus identify OD vs MM origins of the impacting particle. Laboratory experiments have shown that impacting particles ranging in size from a few µms to mms leave behind residues on all foils that they contact and that the dimensions of the impacting particle may be estimated from the size of the crater/penetration hole they create on the front foil. Upon retrieval of ODIE after a minimum deployment of 12 months, impact features can be analysed using a suite of analytical techniques that are typically too large for use in space (e.g. Scanning Electron Microscope, SEM) and thus determine the flux of OD and MM populations in LEO.
Our proposed design comprises 4 polymer foils (Kapton) with thicknesses ranging from 25 µm (front foil) to 125 µm (rear foil). The total surface area of ODIE should be as large as possible to maximise the number of particles collected, however, we have designed the collector to be composed of smaller cells measuring 10 cm x 10 cm to facilitate manufacture, handling and post-retrieval analysis. These cells comprise of an Al frame, within which 1 cm thick plastic support frames ensure the foils are evenly spaced. As ODIE is to be placed in LEO, each foil requires coating to prevent erosion by atomic oxygen (AO). Conventional coatings of Al and Au have the potential to hinder the identification of OD and MM residues thus we have chosen to coat our foils with Pd. Coating the foils also facilitates post-retrieval identification of impact features with holes/craters appearing dark against the bright coated foil in SEM backscattered electron images.
The Light Gas Gun (LGG) at the University of Kent is being used to test ODIE and determine the relation between the size/composition of impactors and the impact features/residues they generate and to discover how these change as impact velocity, impact angle, projectile composition and projectile size are varied. Modelling is also being performed to extrapolate to higher velocities than achievable in the LGG (>7 km/s). We also aim to evaluate our Pd coated foils’ resilience to AO and perform thermal, vacuum and vibrational tests and combine all results to advance ODIE technology to Technology Readiness Level 5.
