Harnessing Asteroids and Comets to Travel the Solar System

NASA is funding a study to see if it might be possible to use asteroids traveling between the orbits of Earth and Mars to shelter spacecraft from radiation. The study is the brainchild of Daniella Della-Giustina, engineering physics undergrad from the University of Arizona - and maybe science fiction writer Arthur C. Clarke.She will investigate two possibilities. The first involves spacecraft actually hitching a ride on asteroids that cross the orbits of both Earth and Mars; astronauts could mine various resources from the asteroid during their journey.The second possibility is that the asteroid could be used as a "sunshade." Astronauts would travel in the shadow of the meteor for as long as possible; astronauts could visit the asteroid on short space walks.Which brings us to Arthur C. Clarke. His short story Summertime on Icarus was published in 1960; it describes a method for getting a research ship closer to the sun than ever before using a comet:

Everything had been carefully planned, years in advance, as part of the International Astrophysical Decade. Here was a unique opportunity for a research ship to get within a mere seventeen million miles of the sun, protected from it's fury by a two-mile-thick shield of rock and iron. In the shadow of Icarus, the ship could ride safely round the central fire which warmed all the planets, and upon which the existence of all life depended.

This is not the first time NASA has investigated ideas for radiation shielding proposed by science fiction writers; see NASA's New Radiation Shielding First Proposed By John W. Campbell In 1936.

Adaptive Optics - Straightening Out Bent Starlight

photo: Photo courtesy of Gemini Observatory, National Science Foundation, and the University of Hawai'i Adaptive Optics Group.The image on the left was taken without adaptive optics (AO), the image on the right was with AO. Notice that the starlight is much more concentrated with the AO System and produces significantly sharper images.An AO system was installed on Gemini North in early 1999.

Whenever starlight passes through our atmosphere, it's distorted by turbulence - similar to what we feel when traveling in an airplane. We've all seen the effects of this turbulence on stars, it's called twinkling. Because twinkling blurs images made through a telescope, scientists go to great lengths (and heights) to reduce its effects.

One of the reasons that the Hubble Space Telescope was put high above the earth's atmosphere was to escape its adverse effects. Since earth orbit is not an option for Gemini, a relatively new technology called Adaptive Optics will be used. Adaptive Optics simply takes a sample of starlight, determines how the atmosphere bent it, and then uses a deformable mirror to "straighten" the starlight out again. Sounds simple? Well, there's a bit more to it than that, here are a few more details...

Because stars are so far away, starlight passing through our atmosphere consists of parallel rays of light that are bent and diverted by air of different temperatures and therefore different densities. Of course our atmosphere is constantly changing and mixing together, so the effect is very random and quite dynamic.

When starlight enters a telescope like Gemini, if nothing is done, the distortions caused by the atmosphere are magnified and stars often look more like shimmering blobs than the pin-points of light they would be if viewed from space. However, before starlight passes into many of the instruments or cameras on Gemini, a representative column of starlight is diverted into what is called a "Wavefront Sensor."

The column of light entering the wavefront sensor is a representative sample of the light that is being collected across the entire main mirror of the telescope. In other words, any distortions that are visible to the wavefront sensor correspond directly to distortions somewhere in the atmosphere above the telescope. In order to use this information, the wavefront sensor separates the column of light into many areas or zones and samples each zone to determine how the light was altered by our atmosphere.

By taking samples many times per second, the information from the wavefront sensor is fed back to a "flexible" mirror that can be adjusted (like a funhouse mirror) to counteract for the distortions caused by the atmosphere. However, unlike a funhouse mirror, these adjustments are very small, and can't even be seen if you were to watch the mirror.

AO systems work best with longer wavelength light, which means that Gemini will see the most dramatic results with infrared observations. Using this system, it is expected that Gemini will produce the sharpest images yet of the infrared sky and dramatically improve many other types of observations as well.

Recently Gemini has found an exo-planet using this technology.

Intel plans to tackle cosmic ray threat

Computer processor manufacturer Intel have revealed details of a patent for protecting future generations of computers from the growing threat of cosmic rays.The company has designed an on-chip cosmic ray detector to try to cope with the particles, which originate in space before sporadically entering the Earth's atmosphere and going through everything they encounter.Because the operation of computers is through charged particles, the unpredictable hits from the rays are problematic, potentially causing the system to crash.

"What happens is if a cosmic ray causes a collision inside the silicon chip, that releases lots of charged particles," Intel's senior scientist Eric Hannah told BBC World Service's Digital Planet programme."All our logic is based on charge, so it gets interference."

Bigger disturb:

The risk from cosmic rays may not be thought of as a big problem on a single computer with a single chip, as there is the potential for error only perhaps every several years.But Mr Hannah explained that on a supercomputer with 10,000 chips, there was the potential for 10 or 20 faults a week.And the risk of cosmic ray interference will only increase as chips get smaller. This is because circuits will require less charge per switch to operate.Since the amount of charge from cosmic rays will remain the same, there will be a "bigger disturb," Mr Hannah explained.

And this is potentially a problem not just for PCs and supercomputers, but anything with computer-operated parts - for example cars."You could be going down the autobahn at 200 miles an hour and suddenly discover your anti-lock braking system doesn't work because it had a cosmic ray event," Mr Hannah said."It's strange, but this is the reality we're moving into as we get smaller and smaller circuits."The cosmic ray detector is therefore designed to spot when rays have caused interference and then tell the chip to repeat the command."Everyone else was trying to do it with circuit resistance and more robust designs, or looking at the architecture," said Mr Hannah."I looked at it and said, 'that's a lot of energy being deposited in a short amount of time, and if you could detect that event with a cosmic ray detector.'"Being a physicist it didn't look too hard to me - we could simply say, 'you were just hit by a cosmic ray, you may want to redo that calculation'."

He said that discussions are now under way within Intel about how to build such a detector and see how it works.But he admitted that it will be hard to say when such a device may become a practical reality.Such devices are "not too easily built," he said, and required a way to build, for example, very small microphones."It's hard to say when it might or might not hit a product," he added.