Using a solar sail to deflect an earth-destroying asteroid

solar sail mission to Apophis

In a paper published today on the Los Alamos astro-ph preprint website, two Chinese scientists have proposed using a solar sail for deflecting any asteroid that happens to be aimed at the earth. The diagram to the right is their simulated mission to impact the asteroid Apophis, which will pass close to the earth in 2029 and — depending on whether that flyby puts it through a very small 600 meter-wide mathematical “keyhole” — could then return in 2036 on a collision course.

The idea is to use the sail to slow the spacecraft down enough so that it starts to fall towards the sun. The sail is then used to maneuver it into a retrograde orbit. When it impacts the asteroid the impact will therefore be similar to a head-on collision, thereby imputing the most energy in the least amount of time with the least amount of rocket fuel. In their Apophis simulation, a mission, weighing only 10 kilograms (about 22 pounds), launched around 2025, and hitting the asteroid in this manner in 2026, would deflect its flyby in 2029 enough to guarantee it will not fly through the “keyhole” and therefore eliminate any chance of it hitting the earth in 2036.

Obviously many questions must be answered before such a mission should fly.
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American manned space: dependent on the Russians in more ways than you think

American manned space: dependent on the Russians in more ways than you think.

As commentators from around the country gnash their teeth at U.S. dependence upon Russia to move cargo and astronauts to the mostly U.S. built/funded International Space Station (ISS), they’ve missed the bigger boat: With one exception, all the commercial spaceflight offerings currently in the works have Soviet or Russian engines as a key part of the rockets involved.

Strange craters on Vesta

strange craters on Vesta

The images from Dawn keep rolling in. The picture on the right, released two days ago, shows the asteroid’s terminator. What makes it intriguing is the weird looking crater near the bottom of the image. It appears to have formed at impact on the wall of a cliff, something that at first glance seems impossible.

This is what I think happened: The impactor sliced down the wall of the cliff, but because of Vesta’s low gravitational field the impact scar never collapsed downward, filling in.

I once wrote an article about asteroids for Astronomy where I described these objects as having the consistency of mashed potatoes and ice cream sundaes. This image illustrates this nicely. The asteroid’s weak gravitational field limits the density of its material, so that puffy strange formations such as this crater can form.

A blank sun during solar maximum

Though it is not yet official, it appears the sun is blank of sunspots today, for the first time since January 16.

Solar scientists have concluded that the solar minimum of the past four years has ended and that the sun is now moving towards solar maximum. The recent activity in August has seemed to confirm this. However, once the minimum has ended, the sun should not have any further blank days until the maximum is over and the sun is ramping back down to solar minimum. That the sun should appear blank again during its ramp up to solar maximum is quite unusual, probably unprecedented, and is further evidence that the sun is heading towards a period of little or no solar activity.

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