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Phipps C.,Photonic Associates LLC | Lander M.,UES, Inc.
AIP Conference Proceedings | Year: 2011

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of space is threatened by runaway collision cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1cm is now a reality that we ignore at our peril. The least costly, and most comprehensive, solution is Laser Orbital Debris Removal (LODR). In this approach, a high power pulsed laser on the Earth creates a laser-ablation jet on the debris object's surface which provides the small impulse required to cause it to re-enter and burn up in the atmosphere. The LODR system should be located near the Equator, and includes the laser, a large, agile mirror, and systems for active detection, tracking and atmospheric path correction. In this paper, we discuss advances that have occurred since LODR was first proposed, which make this solution to the debris problem look quite realistic. © 2011 American Institute of Physics.

Phipps C.,Photonic Associates LLC
International Journal of Aerospace Innovations | Year: 2011

In this paper, we address the problem of predicting p(I), the variation of surface ablation pressure vs. incident pulsed laser intensity I, from the onset of ablation through the transition to its mediation by laser-induced plasma in vacuum. Despite its simplicity, the recently published approach of Sinko and Phipps [1] to this problem describes momentum coupling for many laser-target interactions quite well, for one material at a single wavelength where the ablation fluence threshold is clearly defined. Alternatively, if vapor pressure vs. temperature data p(T) is available for a material, e.g., using the SESAME tables, a different model can be used. In addition to the p(T) data, this model only requires knowledge of basic parameters for the material, such as specific heat, thermal conductivity, optical absorptivity, atomic weight, and its ionization state energies and their partition functions. Since all these parameters, except for optical absorptivity, are independent of laser wavelength, it is possible to calculate a material's mechanical impulse response to pulsed laser irradiation with broad applicability. We show that our model agrees with published data on momentum coupling in aluminum from KrF to CO 2 laser wavelengths to within a factor of two.

Phipps C.R.,Photonic Associates LLC
Acta Astronautica | Year: 2014

Collisions among existing Low Earth Orbit (LEO) debris are now a main source of new debris, threatening future use of LEO space. Due to their greater number, small (1-10 cm) debris are the main threat, while large (>10 cm) objects are the main source of new debris. Flying up and interacting with each large object is inefficient due to the energy cost of orbit plane changes, and quite expensive per object removed. Strategically, it is imperative to remove both small and large debris. Laser-Orbital-Debris-Removal (LODR), is the only solution that can address both large and small debris. In this paper, we briefly review ground-based LODR, and discuss how a polar location can dramatically increase its effectiveness for the important class of sun-synchronous orbit (SSO) objects. With 20% clear weather, a laser-optical system at either pole could lower the 8-ton ENVISAT by 40 km in about 8 weeks, reducing the hazard it represents by a factor of four. We also discuss the advantages and disadvantages of a space-based LODR system. We estimate cost per object removed for these systems. International cooperation is essential for designing, building and operating any such system. © 2013 IAA Published by Elsevier Ltd. All rights reserved.

Phipps C.,Photonic Associates LLC | Sinko J.,Nagoya University
AIP Conference Proceedings | Year: 2010

Previously, Phipps, et al. developed a model that permitted laser ablation impulse predictions within a factor of two over an extremely broad range of pulse durations and wavelengths in the plasma regime. This model lacked the ability to predict the intensity for optimum impulse generation. For the lower-intensity vapor regime, below the plasma transition, Sinko developed a useful, fluence-dependent model which predicts impulse delivered for pulsed lasers on polymers at a specific wavelength. Phipps subsequently developed an alternate model which treats elemental solids in the vapor regime, that only requires knowledge of basic material parameters and vapor pressure vs. temperature data. These data, except for optical absorptivity, are wavelength-independent. A simple technique combines either vapor model with the plasma model to form a complete model that moves smoothly through the vapor to plasma transition. In this paper, we apply these models to show the optimum momentum coupling fluence on target, at the transition from the vapor to the plasma regimes, for aluminum (a typical debris material) and polyoxymethylene (representing polymeric debris). The application of this work is the ORION laser space debris mitigation concept. This is an improvement over previous work, in which this optimum was only estimated from the plasma ignition threshold. We present calculations showing how impulse delivered to debris targets in the ORION concept varies with pulse duration, at an optimum fluence determined by nonlinear optical effects in the Earth's atmosphere. © 2010 American Institute of Physics.

Phipps C.,Photonic Associates LLC
AIP Conference Proceedings | Year: 2010

It is now well-established that a Near-Earth Object (NEO) in the 5 to 10-km size range extinguished the dinosaurs. Although such events have an impact interval on the order of 100M years, a method of rapid response to such a threat is crucial, since warning time is short. Objects in the 0.1 to 1 km size range may not be detected before approaching within 1 to 10 astronomical units (AU) of Earth and, since their approach velocity may be 30-60 km/s, that situation leaves 100 - 300 days to respond. Although the most frequently suggested response to such a threat is a standoff nuclear detonation, physically delivered to the NEO, this paper finds significant advantages in retargeting, probability of success and even precise target location are possible with a high power laser alternative. Assuming a momentum coupling coefficient Cm = 3.5 dyn-s/J and detection at 6.3AU, a 770kW repetitive pulse 355nm laser (f = 1.7 ppm with 27MJ, 10ps pulses) will deflect a 200-m-diameter icy NEO sufficiently to avoid collision. The focusing mirror would need to be manufactured on the Moon. © 2010 American Institute of Physics.

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