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The July skies

June 21, 2008
By Ronald W. Kohl
Editor’s note: This monthly guide to the stars is from the Marshall Martz Memorial Astronomical Association, the Southern Tier Astronomy Recreation Society, and The Post-Journal and OBSERVER. For further information, contact the M.M.M.A.A. at http://www.martzobservatory.org or S.T.A.R.S. at http://www.UpStateAstro.org/stars/stars.html.



Early July is a good time to spot evasive little Mercury. Look for it very low in the east-northeast predawn sky during the first two weeks of the month. On Tuesday, July 1, a thin crescent moon will drift above Mercury.

Venus remains lost in the solar glare again this month, still behind the sun in relation to the Earth. Next month it will return to the evening sky.

Mars appears low in the western sky in evening twilight. For the first few nights, the Red Planet is very close to the blue-white star Regulus. It then drifts very close to Saturn on the nights of July 9 through the 12. On Sunday, July 6, a crescent moon will join Mars, Saturn and Regulus to form a nice binocular target, about an hour after sunset.

Jupiter reaches opposition on July 9. On that night it will rise in the east as the sun sets in the west and will be visible all night long. Since Jupiter’s path traces a relatively low arc across the sky this summer, the best telescopic views will be when the planet is located due south.

Saturn is found low in the west as the evening twilight darkens. It will sink lower in the sky each night as the month progresses. Don’t miss the gathering of Saturn, Mars, the moon and the star Regulus on Sunday, July 6.

The Delta Aquarid meteor shower peaks on the night of July 28 to 29. The crescent moon will not be a problem this year. The best viewing will occur during the predawn hours.



REACHING

FOR THE HEAVENS

Since ancient times, humans have always wanted the ability to move upward into the heavens in order to strengthen their connection with the universe, as evidenced by the tale of Jacob’s ladder in the Bible. Today, some scientists are dreaming of a possible space elevator, a revolutionary Earth-to-space transportation system that would rank with the greatest of human accomplishments. Although it sounds like a crazy idea, a successful space elevator would be an excellent alternative to rocket boosters for space exploration, providing relatively cheap, easy, low-risk access to both low Earth and geo-synchronous Earth orbit. Now, with the advent of carbon nanotube composites, this dream could become a reality, enhancing the lives of all humanity.

The concept for a space elevator is an old one. The idea was first proposed by the Russian scientist Konstantin Tsiolkovsky more than a century ago and interest again surfaced in the 1960s. In 1978, Arthur C. Clarke discussed the concept at length in his novel, ‘‘Fountains of Paradise.’’ However, the scheme of actually building one remained in the realm of science fiction, because there was no material in existence that was strong enough for the cable.

Then, in 1991, a Japanese scientist working with the tiniest of technologies discovered carbon nanotubes that have the potential to be more than 100 times as strong and 20 percent more flexible than steel, at one-sixth the weight. The tubes are long, narrow (one nanometer in diameter, about 1/50,000 the width of a human hair) cylindrical molecules with walls made of carbon atoms. Their strength is three times greater than that needed for the space elevator cable. Several labs and universities are currently working on processes to lengthen the nanotubes and to then spin them into a cable structure. Now, the concept of a space elevator is no longer science fiction, although it will be at least another 30 to 50 years before the initial one is completed.

Scientists have recently determined that a carbon nanotube composite ribbon would actually perform better than a cable structure. One end would be anchored to a very high tower on an offshore sea platform and the other end would attach to a counterweight satellite about 62,000 miles into space. The system’s center of mass would be in geostationary orbit, 22,240 miles in altitude. At that distance, a satellite over the equator takes exactly one day to orbit the Earth, and, therefore, it will hover over the same point on Earth’s surface.

As the Earth rotates, the counterweight would spin around the Earth in orbit, keeping the paper-thin, 4 cm wide ribbon taut and allowing robotic electromagnetic lifters to carry cargo up and down at relatively high speeds. These lifters would be powered by laser beams projected from the base platform on Earth. The location of the high tower used to tether the ribbon on Earth would need to be somewhere along the equator so that it would align properly with the geostationary orbit position directly overhead. An equatorial base site is also essential since that region experiences extremely few hurricanes and tornadoes.

One of the basic problems facing space agencies around the world today is the incredibly high cost of sending things into orbit. It currently costs over $10,000 per pound to place a payload into low Earth orbit. Potentially, the cost to reach a much higher geostationary orbit using a space elevator would be lowered to only a few dollars per pound. Passengers and cargo would be able to ride up and down the cable in a manner similar to a cable car, traveling at just a fraction of escape velocity. In much the same way as a bridge connects cities across a body of water, a space elevator would function as a utility and transportation system for transferring power, payloads and people between Earth’s surface and space.

When can we expect a space elevator to be available to take us on the ride of a lifetime? When asked this question, the author Arthur C. Clarke (Space Odessy:2001) answered ‘‘The space elevator will be built about 50 years after everyone stops laughing.’’

Article Photos

Image courtesy of Kunsthistorisches Museum Wien, Vienna.
Top left: The Bible contains the mythical story of the Tower of Babel, supposedly built by humans sometime after the legends of Noah’s arc and the Deluge took place. Since ancient times, people have wanted to go up to the heavens.

Illustration courtesy of Alan Chan
Middle: A substantial transfer station would be built at the geostationary orbit point, 22,370 miles up the cable. This station would handle cargo, deploy satellites into other orbits, assemble and refuel spacecraft, and also act as a tourist destination.

Graphic courtesy of The Spaceward Foundation
At right: This drawing illustrates the concept of the Space Elevator. A magnetic levitation and propulsion system, powered by laser beams from the base platform, would climb the tether to deliver cargo to low Earth orbit or to the transfer station in geostationary orbit.

 
 

 

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