Add to Google  The Space Elevator Search Engine    
Prime Space Real Estate

LaGrange Points
Source: L5 News via National Space Society Archives
Look up at wide-open space with rose-coloured glasses and there's a potential utopia - lots of room for everybody. The reality is that space will be colonised for the same reason the 'new world' was - proximity to resources - the moon and near-earth asteroids in this case. Only certain locations can be colonised profitably.

We tend to think of the technologies and concepts we use today as 'new' but, as usual, we stand on the shoulders of the giants who came before us.

In 1772 an Italian-French mathematician named Lagrange showed that there are five Libration points where, given two massive bodies in circular orbits around their common center of mass (e.g. the Earth and the Moon), there are five positions in space where a third body of comparatively negligible mass could be placed and maintain its position relative to the two massive bodies. These points have the peculiar property of allowing objects to orbit around them even though there is no material object nearby.

The Earth-Moon L1, L2, and L3 points lie on a line connecting the Earth and Moon. They are stable only in the plane perpendicular to the line between the two bodies. If an object located at one of these points drifted closer to one of the masses, the gravitational attraction it felt from that mass would be greater, and it would be pulled out of orbit.

The other two are L4 and L5. They lie at equal distance from Earth and Moon, in the Moon's orbit, thus forming equilateral triangles with Earth and Moon such that the libration point is ahead of (L4), or behind (L5), the smaller mass in its orbit around the larger mass.

L5 is the only one to have its own song (Home on Lagrange (The L5 Song) © 1978 by William S. Higgins and Barry D. Gehm).

The reason these points are in balance is that at L4 and L5, the distances to the two masses are equal. Accordingly, the gravitational forces from the two massive bodies are in the same ratio as the masses of the two bodies. While a colony could not be placed directly at L4 or L5, it could be placed in an orbit around one of these points that keeps the colony about 90,000 miles from its central libration point.

Several NASA missions are stationed at or use Lagrange Points and clouds of dust, called Kordylewski clouds, even fainter than the notoriously weak gegenschein (sunlight reflected by interplanetary dust), are also present in the L4 and L5 of the Earth–Moon system.

Space Colonisation Scenario
Source: NASA
The diagram to the right is from a 1975 NASA Publication: Space Settlements: A Design Study. Quoting from page 175: "An upper limit to the speed of growth of space colonization is estimated by assuming 3 years for the duplication of a habitat by a workforce equivalent to 12 percent of a habitat's population. Only 56 years are required at this rate for the construction of communities in space adequate to house a population equal to that of the Earth today."


[N.B. I decided not clutter this post with links but it was mainly drawn from these: Wikipedia: LaGarangian Point, National Space Society]

Labels: , ,

Exploring Earth from Space for Free

The beautiful images of Earth returned from space always fill me with awe and wonder. When the space elevator is up and running, first-hand experience of the 'astronaut's-eye-view' of Earth will be the main visual image people will retain once back on Terra Firma.

We don't have to wait to see stunning shots of near-real-time events since the European Space Agency (ESA) put up the
MERIS Images RApid VIsualisation (MIRAVI) web site offering two-hour-old images of fires, floods and volcanic eruptions etc. from the world’s largest Earth Observation satellite, Envisat, ESA's polar-orbiting Earth observation satellite.

is free and requires no registration to view the images generated from the raw data collected by Envisat’s optical instrument, MEdium Resolution Imaging Spectrometer (MERIS), and provides them online within two hours and also provides a searchable archive of images taken since May 2006.

The site comes with a bit of a disclaimer: "
Although the images are fascinating and provide the marvellous feeling that users are ‘onboard the satellite’, they are not suitable for scientific use. Scientists use MERIS products that exploit the instrument’s 15 spectral bands and are generated with sophisticated algorithms. MIRAVI images use only a few spectral bands processed to appear the way the naked eye would see them."

Technical Note: I couldn't get the MIRAVI site to work in FireFox although it worked well in Internet Explorer. Non-technical types may find the interface a bit daunting and it takes a few steps to actually view an image but the results are well worth it. --PB--

Labels: , ,

The Astronaut Farmer - Private Space Flight Goes Hollywood

You have to know somebody who would start a space elevator blog is not-exactly pro-rocketry. Besides the tons of pollutants thrown with every launch and the space debris blanketing the earth from decades of throw-away booster stages, dead satellites etc., rockets just strike me as horribly inefficient and needlessly expensive. Not that the space elevator will be cheap to build but, once built, the cost of getting to space decreases with each lift.

All that aside for the moment, what caught my eye is not the fact that someone wrote the story but that it got financed. Hollywood thinks there's a market for space-related movies.

The Astronaut Farmer is about a NASA astronaut (played by Billy Bob Thornton) who is forced to retire to save his family farm. Unable to give up his dream of space travel, he builds his own rocket despite the government's threats to stop him. (View Trailer)

This seems like another All-American-boy-with-a-dream movie and space travel just happens to be far out enough to make the protagonist seem crazy but realistic enough to actually happen while being something the movie-going public can grasp. So the Hollywood money is mostly behind the moral carried in the tagline: If we don't have our dreams, we have nothing. Still, I'm glad to see private space travel is somewhere in our collective psyche.

Labels: ,

News by Google   Latest Space Elevator Headlines by Google News™