This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

21 November 2010

Paper: "Rotational Mass Driver - an Efficient NEO Deflection Concept"

Source: Z. M. Ilitz, "Rotational Mass Driver — an Efficient NEO Deflection Concept"

Paper sent by the author on his NEO impact mitigation concept.

"Rotational Mass Driver - an Efficient NEO Deflection Concept"
by Z. M. Ilitz (Subotica, Serbia)

Protecting the Earth against Collisions with Asteroids and Comet Nuclei, Proceedings of the International Conference: "Asteroid-Comet Hazard–2009," Saint Petersburg, Russia, 2010.

There is an Olympic athletic discipline - throwing of a ball on a chain. This paper explores the possibility of using the same method for asteroid deflection. Instead of a chain, however, a tether (or a rope) must be used. As it turns out, the method has many merits. It offers high precision and controllability, is safe, efficient, and has a wide applicability range. The performance envelope for the rotational mass driver specifically covers binaries, rubble piles, and large objects on a direct collision course that need a delta-V of cm/s. The method is comparably efficient to nuclear methods, but is much safer.

Selections from the paper:

Space is a rather harsh environment, imposing strict limitations for tether material. However, there exists a material that fulfills all the needed criteria and is perfect for this job: “M5” fiber from DuPont, manufacturer of kevlar. The most important property of this material is that it is the only one that actually strengthens when exposed to UV radiation, while most of the others deteriorate if unprotected, sometimes very rapidly. Moreover it is resistant to temperatures encountered in Venus-like solar orbit, and it has tensile strength comparable to zylon (which needs coating protection against UV rays). A “comparably strong” zylon Z180 weights 2.44 kg/km, has a diameter of 1.02×3.43 mm, tensile strength of 5783 N, and a modulus of elasticity of 124 GPa [3]. Several other, less suitable choices exist, like PBI (material for spacesuits) or kevlar.

An attachment to the unknown, and probably unstable surface of the asteroid is needed. Considering how light-weight these tethers are, the idea is to loop them, like many “tentacles”, all the way around the asteroid. The spacecraft (S/C) will then mount the asteroid as a rider mounts a horse. To do this, tentacles are deployed in space during descend to the asteroid surface, and on touchdown their momentum will carry them, like whips, all around the surface (Fig. 1). Hereby, entanglement is a desired outcome, not a danger. The whole operation should last about 20 minutes, and the tentacles should only be kept from entangling each other during their deployment, not after that. Once they start whipping the asteroid, it is desirable for them to entangle on the opposite side to provide better attachment. For this purpose, they should be a little longer than necessary. Small hooks and bags of clay at their ends would ensure that they don't bounce back, but stay attached, securing the S/C. Usage of Hoytethers, and redundancy in their numbers provides safety against accidental cutting.

The best place to mount a NEO is on its lighted rotational pole (see Fig. 1). While this is not a requirement for this concept to work, the landing on a pole does makes things easier, as it also enables a “Tug boat” concept to be used as an alternative backup method of asteroid deflection.

Link: Google Docs

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