Thoughts on Extraterrestrial Intelligence

by | Jan 11, 2005 | , | 0 Comments

Centauri Dreams' hunch about extraterrestrial life is that it's ubiquitous. The guess is that we'll eventually find off-Earth biospheres right here in the Solar System, probably on Mars, perhaps on one or more of the Jovian moons, possibly in the atmospheres of one or more of the gas giants (and the Venusian atmosphere is now drawing serious interest). We're likely to find simple life around extrasolar stars in equal profusion. This is a heartening thought, but the key word is 'simple.' For the other half of the Centauri Dreams hunch is that extraterrestrial intelligence is rare. At one point, Carl Sagan was estimating there might be one million civilizations existing at any given time in our galaxy. The betting here is that the number is between 1 and 10, with the likelihood being 1. See Ward, Peter and Donald Brownlee, Rare Earth: Why Complex Life is Uncommon in the Universe (New York: Copernicus Books, 2000) for the background to this argument. But we needn't be troubled if we...

read more

Kepler and the Search for Terrestrial Worlds

by | Jan 10, 2005 | , | 0 Comments

In Finding Other Worlds, Edna DeVore of the SETI Institute zeroes in on the importance of the Kepler Mission. Scheduled for an October 2007 launch, Kepler is likely to discover hundreds of extrasolar planets. And as DeVore writes, "Kepler is the first observatory capable of finding Earth-size worlds in the habitable zone of distant Suns. In other words, Kepler may find 'good places to live.'" Some key points about Kepler: To find planets, the mission will use the transit method, looking for the dimming of a star caused by repeated transits of a planet across its face. The size of a planet can be calculated from changes in the star's brightness, and the size of its orbit can be measured. The parameters of the mission are the most challenging ever attempted for extrasolar detection. Kepler is designed to survey nearby stars to determine how often terrestrial and larger planets occur in the habitable zone of different types of star. This, in turn, will allow the follow-on Space...

read more

Interstellar Migration and the Human Experience

by | Jan 8, 2005 | | 0 Comments

"The existence of plausible fastship concepts suggest[s] that once the available technology base has grown sufficiently large, small bands of explorers and pioneers will make the leap between stellar oases. How large the movement of people might be depends, of course, on the cost. If fastship voyages require a significant fraction of the total human wealth, they will be few and far between. We can estimate the relative cost. The sun outputs enough energy to permit 50,000 emigrants to leave the Solar System each second (if that were the only use of the gathered sunlight). If, by the time humanity is ready for the interstellar adventure, our descendants have managed to tap even a modest fraction of the solar output, they could easily afford emigration at a rate sufficient to sustain the human expansion. If we take the figure of 500 men, women, and children, a number suggested by studies of breeding populations among surviving hunter and gatherer peoples, as the minimum size of a...

read more

Gravitational Lensing Offers Clues to Dark Matter

by | Jan 7, 2005 | | 0 Comments

The 'concordance' model of the universe suggests that it is mostly composed of dark matter. In fact, a cluster of hundreds of galaxies would, in the concordance scenario, house fully 90 percent of its mass in dark matter. Never mind that we know almost nothing about dark matter -- theorists have still been able to simulate how it would clump together, forming an intricate substructure that should be capable of observation. Now a Yale astronomer and her colleagues have used gravitational lensing to study galactic clusters, finding a tight fit between the concordance model's predictions and their observations. A gravitational lens might be a galaxy that intervenes between us and a more distant object, focusing the light from that object so that we see things we would not otherwise be able to observe. Says assistant professor of astronomy and physics Priyamvada Natarajan: "We used an innovative technique to pick up the effect of precisely the clumps which might otherwise be obscured by...

read more

The View from Huygens

by | Jan 6, 2005 | | 0 Comments

When the Huygens probe descends through Titan's atmosphere on January 14, only one optical instrument will be available for imaging. The Descent Imager/Spectral Radiometer (DISR) will take photographs of the surface during the two-hour descent, relaying the data to the Cassini orbiter for re-transmission to the Deep Space Network. Martin Tomasko of the University of Arizona's Lunar and Planetary Laboratory leads the international team in charge of DISR; he and other UA colleagues will head for the European Space Operations Center in Darmstadt, Germany next week. Key points: The Huygens probe should emerge from Titan's haze layer at an altitude of about 43 miles (70 kilometers), allowing the DISR instrument to get clear views of the descent and the surface below. The instrument's three cameras will take 750 images, which will be merged into a series of panoramic views of the ground and horizon. All DISR data will be relayed to Cassini at a height of 12 miles, to guard against the loss...

read more

Remembering Mariner 2

by | Jan 5, 2005 | | 2 Comments

As we await the Titan descent, Cassini and Huygens have all the headlines, but Centauri Dreams is remembering a much earlier mission. The Mariner 2 Venus probe was the first successful interplanetary spacecraft. In its pre-autonomous days, spacecraft could be crippled without communications from controllers monitoring their progress. Launched in August of 1962, the probe was a rare early success for the Jet Propulsion Laboratory after a string of lunar failures (the Ranger series), but as it headed for Venus, controllers realized that Mariner 2 would miss its target by over 200,000 miles. The needed mid-course correction was made by encoding computer commands on tape, feeding them to the Deep Space Network's antennae at Goldstone, and transmitting them to Mariner 2, which in turn fed them into its own command sequencer and, over a million and a half miles from Earth, fired its thrusters for almost four hours to adjust its trajectory. The mission was a success, but only because the...

read more

Continuing Success for Ion Thrusters

by | Jan 4, 2005 | | 0 Comments

The Japan Aerospace Exploration Agency's Hayabusa spacecraft (formerly known as MUSES-C) is demonstrating the advantages of ion propulsion in its mission to land on the asteroid Itokawa and return samples of its surface to Earth in 2007. When it performed an Earth flyby in May, Hayabusa became the first spacecraft to accomplish such a maneuver using an ion engine as its main thruster. In cruise mode, the craft's four ion engines were designed to burn throughout the flight. JAXA's recent announcement that Hayabusa's engines had marked 20,000 hours of 'accumulated operational time' points out the ion advantage: the spacecraft's engines consumed a mere 20 kilograms of propellant during that time. You can see the JAXA news release here. Ion engines operate continuously for long periods because their thrust levels are low, but their high efficiency makes them ideal for deep space missions. Hayabusa uses ionized xenon gas sent through a strong magnetic field and expelled at high speed as...

read more

2004 a Good Year for Solar Sails

by | Jan 3, 2005 | | 0 Comments

Interstellar propulsion studies were upstaged in 2004 as we followed planetary exploration: the progress of the Spirit and Opportunity Mars rovers, the Cassini Saturn orbiter and the upcoming Huygens descent onto Titan. But the year was not without significant interstellar news, even though it received little media attention. In separate tests in Ohio and Virginia, two NASA contractors successfully tested solar sail deployments on sails of their own design. In July, L'Garde (Tustin CA) deployed a solar sail nearly 33 feet in length along one side; a separate design created by Able Engineering of Goleta was tested in April and May. The engineering and analysis that went into these tests will help us get sails into space for testing even as we await the launch of the private Cosmos 1 sail sponsored by the Planetary Society. Image: A four-quadrant solar sail system sits fully deployed in a 100-foot-diameter vacuum chamber at NASA's Glenn Research Center Plum Brook Station in Sandusky,...

read more

Looking Back at Project Orion

by | Jan 1, 2005 | | 0 Comments

"'I think there is absolutely no doubt -- and we did some experiments later; still quasi-classified, related to Casaba-Howitzer -- that the propulsion system would have worked. We knew what we were doing in designing it. We could send 85 percent of the momentum in one direction that we wanted it to go in, and there were enough experiments -- and there have been enough experiments -- done on the protection of the pusher plate, to have no doubt that it would have worked. Between those two things there is a tremendous amount of engineering detail to be worked out, but I think it was engineering detail. It could have worked. Now, could it have been done economically, could it have been done in time? Those were all different questions, but I think all of those things could have been solved. Today, people ask me, 'Was it really a joke, Pyatt, or was it serious?' It was dead serious. If we wanted to do it, if there were any good reason for wanting to have high specific impulse and high...

read more

A Tantalizing Glimpse of Iapetus

by | Jan 1, 2005 | | 0 Comments

For the weekend, here is a first look at Iapetus from yesterday's Cassini flyby. JPL describes this as a raw image that "...has not been validated or calibrated." This image was taken on December 31, 2004 and received on Earth January 01, 2005. The camera was pointing toward IAPETUS at approximately 60,821 kilometers away, and the image was taken using the CL1 and CL2 filters. Credit: Jet Propulsion Laboratory. You can find more Iapetus images in the Cassini raw image beta page.

read more

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

Now Reading

Recent Posts

On Comments

If you'd like to submit a comment for possible publication on Centauri Dreams, I will be glad to consider it. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language, and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to others, I'm probably not going to run it.

Follow with RSS or E-Mail

RSS
Follow by Email


Follow by E-Mail

		

			
Get new posts by email:

			

				
				
			

			

				
			

		

	


Advanced Propulsion Research




Beginning and End







Archives