Space Debris Affirmative

Tungsten Solvency (1/4)

Tungsten cloud solves best – Creates drag to bring the space junk down

When it comes to solving the growing space junk problem, solutions range from catching it in giant nets to blasting it from orbit with lasers--and these are DARPA’s and NASA’s best plans, respectively. By contrast, the Naval Research Laboratory has a scheme that seems much more feasible, though fraught with negative consequences: using a cloud of tungsten dust to create atmospheric drag at orbital altitudes, deorbiting the thousands of pieces of tiny space junk whirling about the heavens. The idea is simple enough: at altitudes below about 560 miles, the drag of the atmosphere naturally decays orbits, causing smaller bits of debris to slowly lose their orbits over the course of a couple of decades. But above that limit small debris--the stuff smaller than 10 centimeters that is very hard to track--can stay up there for decades or even centuries, threatening to damage satellites and spacecraft. A researcher at the U.S. NRL suggests releasing a cloud of tungsten dust at about 680 miles up, creating a layer of particles that will completely shroud the planet. The particles themselves will be just 30 micrometers across, but because tungsten is nearly twice as dense as lead they will still add effective weight to any small debris they latch on to. This, the thinking goes, will drag small debris pieces down below that 560 mile marker over a decade or two, where natural forces will take over and the debris will burn up, scrubbing orbital space clean of small debris over the next 25 or 35 years. If you haven’t begun verbally objecting to this idea at this point, feel free to begin now. First of all, what effect is this tungsten cloud going to have on all of the equipment we don’t want to deorbit, like our functioning satellites? What about the delicate optics on our science satellites and the the solar panels that keep our communications satellites powered up? And, as Tech Review notes, might this tungsten layer obscure our view of the cosmos, reducing the power of our earth-based

Tungsten would not interfere with any current satellite or spacecraft missions, spacecraft tolerant by design, and impacts are miniscule.

7. System Risks Spacecraft are already designed to operate in the existing cosmic dust and orbital debris environment. The orbital debris remediation technique using tungsten dust described herein would involve higher flux than the current background, but mitigations are available. Certain aspects of spacecraft design are already dust impact tolerant by design. Dust grains of the size proposed by NRL will certainly not penetrate thermal blankets, spacecraft structure, or sensor baffles. Normally, earth observation satellites would point the sensors earthward and scientific satellites away from earth both nearly orthogonal to the satellite motion. Hence, the risk to satellite sensors associated with our small debris removal technique is minimal as the tungsten dust would approach in the local horizontal plane only. Solar arrays could also be degraded by dust impacts, but that effect can be mitigated by thicker cover glass. Recent laboratory tests indicate that solar cells remain unaffected by hypervelocity impact of a 100 μ m glass sphere 11) . The NRL concept involves deploying a tungsten dust layer of a limited thickness, perhaps 30 to 50 km. If necessary active spacecraft could be maneuvered above or below this band using onboard propulsion and avoid the artificial dust flux altogether. Finally, tungsten dust is no longer an issue to operational spacecraft below an altitude of about 600 km because once at that altitude, the tungsten dust orbital lifetime would be brief and any interaction time with operational spacecraft below 600 km would be minimal.

Tungsten Solvency (1/3)

Spreading the Tungsten in the atmosphere is possible with current technology and does not pose any ecological or human threat- tungsten microparticles burn up in low altitudes

Ganguli, Crabtree, Rudkov, Chappie 4-7-11 (Gurudas, Christopher, Leonid, Scott, Plasma Physics Researcher at Naval Research Laboratory in Washington D.C, Icarus Research Incorporation, Naval Center For Space Technology Naval Research Laboratory, Cornell University Library- Space Physics, A Concept For Elimination of Small Orbital Debris, April 7, 2011, http://arxiv.org/ftp/arxiv/papers/1104/1104.1401.pdf, pg 4, NG)

Based on the physics discussed above we envision releasing dust in quasi-circular orbits between 900 and 1100 km. The mass of dust required for remediation is a function of the ballistic coefficient of the orbital debris, the desired altitude reduction of the debris, and the desired altitude reduction rate. The dimension and material density of the dust grains will be optimized so that it can sustain the ‘snow plow’ effect. The dust dimension should also be small enough to be harmless to active satellite components and their orbits. The period of induced drag on targeted small debris is purposely designed to be long (years) so that the requirement for total dust mass carried to orbit is lower. In a series of releases in quasicircular polar orbit, the dust cloud will spread and form a thin shell slowly spreading in azimuth with large meridianal velocity in both directions. At any given point in this shell, half of the dust mass will be in orbit oppositely directed to the targeted debris population. The interaction of dust with debris in this shell will lower the debris altitude. The dust layer itself will descend in altitude over time and in the process lower the altitude of all targeted debris from 1100 to 900 km below which the orbital lifetime of the small debris is naturally 25 years or less. Along with the debris, the injected dust will ultimately burn up in the earth’s atmosphere at lower altitudes. The technique described essentially just requires the transportation of “dumb mass” (micron-sized tungsten dust) to polar orbit, No new technology development is necessary. The dust may be delivered as a secondary payload utilizing the excess capacity available in many launches going to sun synchronous orbit or as a separate dedicated dust dispensing satellite.

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