Planetary defense

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Planetary defense, or planetary defence, is the concept of protecting Earth or another planet from extra-terrestrial threats (meaning any threat that originates outside of the Earth).

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[edit] Mitigation of Near-Earth Objects (NEOs)

In terms of real threats, the term planetary defense generally refers to threats from inanimate objects. The most-recognized planetary threat is from asteroids and comets. If a large asteroid or comet impacts the Earth, such an impact event might bring about the end of civilization.

[edit] History of Recent Planetary Defense Professional Activities

In a 1992 report to NASA (Morrison, D., 1992, The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop, NASA, Washington, D.C.), a coordinated Spaceguard Survey was recommended to discover, verify and provide follow-up observations for Earth-crossing asteroids. This survey was expected to discover 90% of these objects larger than one kilometer within 25 years. Three years later, another NASA report (Shoemaker, E.M., 1995, Report of the Near-Earth Objects Survey Working Group, NASA Office of Space Science, Solar System Exploration Office) recommended search surveys that would discover 60-70% of short-period, near-Earth objects larger than one kilometer within ten years and obtain 90% completeness within five more years. In 1998, NASA formally embraced the goal of finding and cataloging, by 2008, 90% of all near-Earth objects (NEOs) with diameters of 1 km or larger that could represent a collision risk to Earth. The 1 km diameter metric was chosen after considerable study indicated that an impact of an object smaller than 1 km could cause significant local or regional damage but is unlikely to cause a worldwide catastrophe (Morrison, 1992). The impact of an object much larger than 1 km diameter could well result in worldwide damage up to, and potentially including, extinction of the human race. The NASA commitment has resulted in the funding of a number of NEO search efforts that are making considerable progress toward the 90% goal by 2008.

Over the past few years, there have been several meetings of world experts on this topic. The 2004 Planetary Defense Conference was held beginning on 23 February 2004 to discuss detection, deflection, policy, law, and disaster preparedness. There was a follow-up 2007 Planetary Defense Conference, held from March 5-8, 2007 in Washington, D.C. that also addressed similar issues.

[edit] Detection

The first step in defending against Near-Earth objects is detection and threat analysis. There are several world-wide programs for detection. Most of these programs are currently (as of early 2007) by NASA's Near Earth Object (NEO) program office as part of their Spaceguard programs. These detection and analysis programs include:

[edit] The 2005 George E. Brown, Jr. Near-Earth Object Survey Act

U.S. Representative George E. Brown, Jr. (D-CA) was quoted as voicing his support for planetary defense projects in Air & Space Power Chronicles, saying "If some day in the future we discover well in advance that an asteroid that is big enough to cause a mass extinction is going to hit the Earth, and then we alter the course of that asteroid so that is does not hit us, it will be one of the most important accomplishments in all of human history."

Because of Congressman Brown's long-standing commitment to planetary defense, a U.S. House of Representatives' bill, H.R. 1022, was named in his honor: The George E. Brown, Jr. Near-Earth Object Survey Act. This bill "to provide for a Near-Earth Object Survey program to detect, track, catalogue, and characterize certain near-earth asteroids and comets" was introduced in March 2005 by Rep. Dana Rohrabacher (R-CA). It was eventually rolled into S.1281, the NASA Authorization Act of 2005. Presently, it is law.

The following text became law as part of the NASA Authorization Act of 2005 passed by the Congress on December 22, 2005, and subsequently signed by the President.

"The U.S. Congress has declared that the general welfare and security of the United States require that the unique competence of NASA be directed to detecting, tracking, cataloguing, and characterizing near-Earth asteroids and comets in order to provide warning and mitigation of the potential hazard of such near-Earth objects to the Earth.

The NASA Administrator shall plan, develop, and implement a Near-Earth Object Survey program to detect, track, catalogue, and characterize the physical characteristics of near- Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such near-Earth objects to the Earth. It shall be the goal of the Survey program to achieve 90% completion of its near-Earth object catalogue (based on statistically predicted populations of near-Earth objects) within 15 years after the date of enactment of this Act.

The NASA Administrator shall transmit to Congress not later than 1 year after the date of enactment of this Act an initial report that provides the following:

(A) An analysis of possible alternatives that NASA may employ to carry out the Survey program, including ground-based and space-based alternatives with technical descriptions.

(B) A recommended option and proposed budget to carry out the Survey program pursuant to the recommended option.

(C) Analysis of possible alternatives that NASA could employ to divert an object on a likely collision course with Earth.

The result of this directive was a report presented to Congress in early March 2007. This was an Analysis of Alternatives (AoA) study led by NASA's Program Analysis and Evaluation (PA&E) office with support from outside consultants, the Aerospace Corporation, NASA Langley Research Center (LaRC), and SAIC (amongst others).

[edit] Mitigation Techniques

The following are an incomplete but somewhat exhaustive list of mitigation techniques. These are techniques based upon different technologies. Each technique has trade-offs with respect to metrics such as overall performance, cost, operations, and technology readiness.

  • Nuclear Deflection: Standoff, Surface, Subsurface
  • Magnetic Flux Compression
  • Gravitational tractor
  • NEO Painting
  • NEONet
  • Mass Driver
  • Laser Ablation
  • Solar Sail
  • Solar Mirror / Concentrator
  • Space Pebbles
  • Chemical Propulsion
  • SpaceTug (*VASIMR)
  • NEPTug (Ion or Hall)
  • Kinetic Impactor: (with or without Explosive)
  • NEO-to-NEO Collision

[edit] Other threats

There is also some speculation about defending against alien invasion, though this is typically in the science fiction realm, as extraterrestrial life's existence is unknown. A recent textbook by Dr. Travis S. Taylor, Dr. Bob Boan, R.C. Anding, and Dr. T. Conley Powell entitled An Introduction to Planetary Defense A Study of Modern Warfare Applied to Extra-Terrestrial Invasion offers some insight, details, and analysis of how humanity might defend itself against an alien invasion.

[edit] Science fiction

Planetary defenses are a recurring theme in science fiction, usually designed to repel an invasion of a planet by an external force; human or otherwise. An example would be during the Earth Alliance Civil War on the television series Babylon 5, whereby the loyalist forces used orbital planetary defense platforms to defend Earth from the separatist forces.

Planetary defenses are not limited to one pre-defined type, some are space or orbital based platforms or ships like in the previously stated example, there are also weapon systems based on the surface of the said planet, as in Stargate SG-1 where the hero uses an Ancient weapon in Antarctica to destroy the villain's invading fleet; others are more simple, including ground based fighters, as in the case in Star Wars Episode IV: A New Hope where single-manned fighters defended a rebel base against a moon-sized Death Star.

The Posleen novels also called the Legacy of the Aldenata series by John Ringo describe in detail a planetary defense scenario using alien technology to construct a fleet of starships. Similar themes can be seen in the animated series Robotech. Robotech also includes a "Grand Cannon" based in the northern hemisphere that is used for planetary defense. Doc Travis S. Taylor's Warp Speed and The Quantum Connection books (known as the Warp War series) gives examples of developing planetary defense systems based on warp technologies. The Von Neumann's War series by John Ringo and Travis S. Taylor also develops an organization designed to develop planetary defense strategies from present day technologies.

[edit] Selected Science Fiction Works

[edit] External links - Websites

[edit] External links - Articles

[edit] External links - Books

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