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Could Ground-Based Lasers De-Orbit Space Junk?
An interesting paper was recently published proposing to use ground-based high-intensity pulsed lasers to bring down small objects in low Earth orbit.
Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes. We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon pressure is the dominant momentum transfer mechanism, showing that shape and orientation effects influence the target response in a similar, but not identical, manner. We address the related problem of target spin and, by way of a few simple examples, show how ablation can alter the spin state of a target, which often has a pronounced effect on the recoil dynamics.
(Bringing down space junk [pdf])
Geometry used to estimate the velocity change required to obtain a pre- determined perigee via the initial stage of a Hohmann transfer (scales exaggerated for clarity). Starting from a counter-clockwise circular orbit (solid curve) with radius r, an impulse opposite the velocity vector, resulting in a velocity change v, is applied at the transfer point. The perturbed orbit (elliptical until capture; dashed curve) is characterized by its semi-major axis a and perigee rp, where rp is suciently low for re-entry to occur.
SF great Arthur C. Clarke had a similar idea, but he wanted to use lasers to blast them from orbit with appropriately equipped ships.
In his 1978 novel The Fountains of Paradise, Arthur C. Clarke uses Operation Cleanup to make sure that low earth orbit is clear of debris for the newly constructed space elevator.
Fortunately, the old orbital forts were superbly equipped for this task. Their radars - designed to locate oncoming missles at extreme ranges with no advance warning - could easily pinpoint the debris of the early Space Age. Then their lasers vaporized the smaller satellites, while the larger ones were nudged into higher and harmless orbits.
From Pulsed Laser Interactions with Space Debris: Target Shape E ects.
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