Starships - Part 1

One day in the distant future, we will have our last nice day on Earth. Eventually, billions of years from now, the sky will be on fire. The sun will swell into a raging inferno that will fill up the entire sky, dwarfing everything in the heavens. As temperatures on Earth soar, the oceans will boil and evaporate, leaving a scorched, parched landscape. The mountains will eventually melt and turn liquid, creating lava flows where vibrant citics once stood.

According to the laws of physics, this grim scenario is inevitable. The Earth will eventually die in flames as it is consumed by the sun. This is a law of physics.

This calamity will take place within the next five billion years. On such a cosmic time scale, the rise and fall of human civilizations are but tiny ripples. One day we must leave the Earth or die. So how will humanity, our descendants, cope when conditions on Earth become intolerable?

Mathematician and philosopher Bertrand Russell once lamented "that no fire, no heroism, no intensity of thought or feeling, can preserve a life beyond the grave; that all the labors of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast death of the solar system; and the whole temple of Man's achievement must inevitably be buried beneath the debris of a universe in ruins..."

Given that humanity must one day flee the solar system in the nearby stars to survive, or perish, the question is: how will we get there? The nearest star system, Alpha Centauri, is over 4 light-years away.Conventional chemical propulsion rockets, the workhorses of the current space program, barely reach 40,000 miles per hour. At that speed, it would take 70,000 years just to visit the nearest star.

Alternatives to chemical rockets? Ion engines. Unlike chemical rockets, ion engines do not produce the sudden, dramatic blast of superhot gases that propel conventional rockets. In fact, their thrust is often measured in ounces. Placed on a tabletop on Earth. they are too feeble to move. But what they lack in thrust, they more than make up for in duration, because they can operate for years in the vacuum of outer space.

A typical ion engine looks like the inside of a TV tube. A hot filament is heated by an electric current, which creates a beam of ionized atoms, such as xenon, that is shot out the end of the rocket. Instead of riding on a blast of hot, explosive gas, ion engines ride on a thin but steady flow of ions.

Another alternative is Solar Sails. Solar sails exploits the fact sunlight exerts a very small but steady pressure that is sufficient to propel a huge sail sail through space. The idea for a solar sail is an old one, dating back to the great astronomer Johannes Kepler in his 1611 treatise Somnium.

Although the physics behind a solar sail is simple enough, progress has been spotty in actually creating a solar sail that can be sent into space. proponents of the solar sail have a idea that might take them to the stars: building a huge battery of lasers on the moon that can fire intense beams of laser light at a solar sail, enabling it to coast in the nearest star. The physics of such an interplanetary solar sail are truly daunting. The sail itself would have to be hundreds of miles across and constructed entirely in outer space. One would have to build thousands of powerful laser beams on the moon, each capable of firing continuously for years to decades. (In one estimate, it would be necessary to fire lasers that have one thousand times the current total power output of the planet Earth).

The third alternative is Ramjet Fusion. My favorite candidate for getting us to the stars. There is an abundance of hydrogen in the universe, so a ramjet engine c0uld scoop hydrogen as it traveled in outer space, essentially giving it an inexhaustible source of rocket fuel. Once the hydrogen was collected, it would be heated to millions of degrees, hot enough so that the hydrogen would fuse, releasing the energy of a thermonuclear reaction.

The ram jet fusion engine was proposed by physicist Robert W. Bussard in 1960 and later popularized by Carl Sagan. Burssard calculated that a ramjet engine weighing about 1,000 tons might theoretically be able to main a steady thrust of 1g of force, that is, comparable to standing on the surface of the Earth. If the ramjet engine could maintain a 1g acceleration for one year, it would reach 77 percent of the velocity of light, sufficient to make interstellar travel a serious possibility

In principle, the ramjet engine could propel itself indefinitely, ultimately reaching distant star systems in the galaxy. Since time slows down inside the rocket, according to Einstein, it might be possible to reach astronomical distances without resorting to putting the crew into suspended animation. After accelerating at 1g for eleven years, according to clocks inside the starship, the spacecraft would reach the pleiades star cluster, which is 400 light-years away. In twenty-three years, it would reach the andromeda galaxy, which is 2 million light-years from Earth. In theory, the spacecraft might be able to reach the limit of the visible universe within the lifetime of a crew member (although billions of years might have passed on the Earth).


This is the first part of Starships, Stay tune next week for part two of Starships. See ya