Friday, March 21, 2008

Missed it By THAT Much

Article in New Scientist:

"...when Cassini's radar tracked surface features on the moon, scientists found evidence that Titan rocks slightly due to tiny shifts in its rotation rate. Currently, Titan spins an extra 0.36° over the course of a year beyond what it would if it were in perfect sync with the moon. The moon's rotation rate also appears to be slowly increasing."

That is approximately sixteen kilometers that the base of the ribbon would need to move each year.

Hyperion, the moon that the ribbon may need to periodically dodge, is three hundred and sixty kilometers in its longest dimension.

Monday, March 17, 2008

Cost to Open the Kashagan Oil Field

The Kashagan oil field is in Kazakhstan's sector of the Caspian Sea, and represents one of the largest oil fields discovered in the last forty years.

There is an article in Salon that states that the cost extimate to open the oil field ranges from $57 billion to $135 billion.

Thursday, March 13, 2008

A Thousand Barrels of Oil, and Other Fun Facts

If I'm doing the math right, a thousand barrels of oil would weigh something like twenty metric tons on the surface of Titan. Titan's gravity is only fourteen percent of the Earth's. Barrels of oil from different oil fields have different weights, but this is a nice, easy to remember number.

In 2004, the United States consumption of oil was approximately 20.7 million barrels of oil per day.

A supertanker carries about two million barrels of oil.

Wednesday, March 05, 2008

Regarding All That Oil On Titan

(or 'A little learning is a dangerous thing')

I read an article recently describing the amount of hydrocarbons on Saturn's moon, Titan.

I wanted to kick around the numbers for a space elevator on Titan, one that would allow the oil to be lifted from the surface, and then thrown out of Saturn's orbit to enter the inner solar system.

So far, I've only managed to characterize the length of the elevator ribbon, not the cross section, or mass of the completed ribbon. These could be computed using a similar method as in shown in The Space Elevator book, but with the additional influence of Saturn's gravity is included in computing each ribbon segment.

All of my numbers are approximations.

Imagine a planet with Saturn's mass, with a day that is 15.94 Earth days long. An object in a synchronous orbit would have an orbital period of 15.94 days. The theoretical elevator for this planet needs to extend past synchronous orbit, out into space, to hold the elevator up, with the appropriate counterweight at the end. A space elevator for Titan is similar to the portion of this imaginary elevator that extends past the planetary synchronous orbit.

Titan is tidally locked with Saturn, with an period of 15.94 days. A space elevator could be built extending directly towards or directly away from Saturn from Titan's surface, providing that that length of the elevator passes through the Saturn/Titan L1 or L2 point respectively, and is capped with the appropriate counterweight. The elevator must pass through the Lagrangian point in order to be long enough to exert a force away from Titan that will hold the ribbon up.

The distance of L1 and L2 from the center of Titan is approximated by computing the radius of the Hill Sphere, which is approximately fifty-two thousand kilometers, so an elevator that passes a distance greater than this from the center of the moon, with the appropriate counterweight (if needed) should be stable.

If the elevator ribbon is longer than three hundred thousand kilometers, it should be able to toss a payload with sufficient speed to escape Saturn's orbit. Escape velocity is a function of the mass of the planet and the distance from the planet, so as a payload moves outward along the ribbon, the escape velocity decreases. Traveling outward from the orbit of Titan, this would cross the orbit of the next moon out, Hyperion. Approximately every twenty-one days, Hyperion would pass in the vicinity of the ribbon. Since the orbits of Titan and Hyperion are not exactly co-planer, Hyperion would not necessarily intersect the elevator ribbon on every orbit. Provisions would still need to be made for deflecting the ribbon if necessary.

A pilot ribbon for Titan would be deployed from a satellite placed in L2. With all of the hydrocarbons available on Titan, it would make sense to lower a package to the surface to manufacture additional ribbon material. An exponentially tapered ribbon could then be built deployed from the surface, built from local materials, and hoisted by the pilot ribbon.

I realize that I haven't calculated what happens to the payload once release from the ribbon, or characterized the orbit required to reach the inner solar system, or how to get the payload to the Earth's surface. All I've done is characterize the length of ribbon required for a payload to escape Saturn's orbit, but this is an interesting start.