The US is dismantling its space program, piece by piece, and neither Europe nor Russia can afford their ambitious space goals. Only China appears to be in a position to pursue the vast opportunities, riches, and challenges of space travel, exploration, colonisation, and . . . . yes, militarisation. It is the high ground, after all.
Unless humans create space-based defenses against errant asteroids, comets, and other dangers from extraterrestrial space, the planet Earth and its precious biosphere will remain defenseless against the most serious threats it will likely face.
Brian Wang takes a look at the problem in a recent posting, Defending Planet Earth from Space Asteroids.
4 approaches depending on circumstances
* Civil defense (evacuation, sheltering, first aid, etc.
- Up to 50 meter in diameter?
* Slow Push-Pull (tug, solar heating, albedo change, gravity tractor, et al.)
- Needs decades to operate (plus time to build, etc.)
- Max size 300-600 m diameter
- Gravity tractor closest to ready and least dependent on properties of NEO
* Kinetic Impacts (Super Deep Impact)
- sensitive to porosity of top meters to tens of meters
- momentum transfer efficiency not known
- much wider range of applicability (max size 1 to 1.5 km, shorter warning for small ones)
- standoff blast best
- works up to 10 km and relatively short warning
* Don Quixote-like mission
- a rendezvous spacecraft at a small NEO followed by a large impactor
- biggest gain in knowledge directly related to mitigation
- Guess $1.5G; Good for international collaboration
* Gravity tractor demonstration
- fewer unknowns other than engineering
- second priority
* Apophis a possible target but any small NEO will do
- Can’t predict which might need to be used first
- Small NEO is by far the most likely
- Warning time very uncertain but short warnings are likely at ~100m diameter or less _NBF
More at link above, and at Planetary Defense and NEO Exploration PPT
Only humans with advanced science and technology can defend their planet from space threats such as comet and asteroid collision. But while the advanced western world governments are dominated by faux environmentalists and beseiged by the twin destructors of debt and demographic decline, science and technology are skewed toward dysfunctional phantom fears such as carbon hysteria, overpopulation doom, etc.
Yet another extremely dangerous societal dysfunction in the west is the ongoing "war against boys" led by highly placed feminsts in academia, journalism, think tanks, and government. It is from among the boys -- including some with Aspergers, dyslexia, and ADD -- that the bulk of high achieving scientists and technologists will inevitably be found. The war against boys is a war against science and technology, and a war against the future of the planet and the human race.
Human societies in general are going the wrong direction, heading toward an Idiocracy. It may be up to isolated groups of humans, building alliances among themselves, to preserve and extend the art of human and planetary survival via the advancement of true science and beneficial / protective technologies.