*** This is Part 2 of a multi-part series. Download a free version of this article from the Freebies page at Raymond Towers Dot Com. ***
In the traditional rocket fuel model, Tsiolkovsky’s Rocket Equation tells us that when a rocket-based ship launches, 63% of its weight will be fuel. For a rocket-based ship to land or slow down, 86% of its weight must be fuel. That is the amount of fuel needed to achieve Exhaust Velocity. To propel a ship at twice Exhaust Velocity, the percentages increase to 86% at launch and 98% for slow-down. This is about 400 pounds of fuel for every 1 pound of cargo at 1 times Exhaust Velocity.
Shooting light photon lasers at a graphene sail is more cost effective, but there are problems with making sure the laser hits the sail at just the right angle and also when the laser and sail are too far apart from each other. The proposed thickness for a graphene sail would be 1 micrometer thick. A galactic GPS network will be necessary to keep things in alignment and for course correction. A sister laser at the destination could help slow the sail down. Additional lasers can be spaced out along the travel route.
Alternatives to photon lasers are charged particles aimed at magnetic sails and also solar neutrinos, if a new material were invented capable of utilizing them.
A sample sail ship could weigh 10 million kilograms (10,000 pounds) and have the shape of a cone to lessen drag and deflect incoming objects. The amount of laser power needed to push this size ship is tremendous, comparable to the noonday sun shining over an entire continent. The laser can also be used as a particle accelerator and for communications.
50 relays per light year at 2000 light years of highway equals 100,000 total relays. These relays would use about a trillion kilograms of hydrogen fuel per day to power the lasers. There are projections that such a system could power a ship fast enough to reach relativistic speeds, but for the purpose of my writing project, I’ll probably set a more practical cap of 10% of light speed.
Newton’s First Law – Objects only change speed if force is exerted on them. This will play an important part in my sci-fi project based on the Space 1999 TV series. In that scenario, Luna was wrenched off its orbit by exploding nuclear waste. The human colony on Luna had no way to slow the moon down, which made up the basic premise of the series: a runaway moon with people on it.
Asteroids could serve as way stations to replenish fuel supplies.
If a ship travels at 10% of light speed, one year on the ship equals 1 year and 2 days on Earth.
1. Easier Access To Solar Energy
2. Easier Trade – Trade from a space habitat to a planet would be easier than from one planet to another, due to less hassles entering and exiting planetary gravitational fields.
3. Space Manufacturing – A space habitat can become self-sufficient in producing food and water for its population. Raw materials can be acquired from asteroids to produce tradable goods. There is enough building material in our main asteroid belt to build enough habitats to equal the surface area of 3,000 Earths.
4. Zero-G Environment – For swimming, hang-gliding and flying airplanes!
Oxygen can be obtained from lunar rocks. Nitrogen can be brought in and recycled, or extracted from comets and moons. Air can be recycled through gardens or hydroponics food production. Catalytic burners can decompose industrial pollutants such as volatile oils, as used in nuclear submarines. Cryogenic distillation can slowly remove tougher mercury vapor and noble gases that cannot be catalytically burned. After the distillation, carbon dioxide and water can go straight into agriculture. Nitrates, potassium and sodium in leftover ash can be recycled as fertilizer. Minerals such as iron, nickel and silicon can be purified and reused industrially.
Zero gravity weakens bones and muscles, and imbalances calcium and the immune system in humans. To counter this, a colony would have to rotate to simulate gravity. Most people are comfortable with a rotational radius of 500 meters at a rate of less than one revolution per minute. A small percentage will experience dizziness and vertigo.
The habitat could be shielded from cosmic rays by its outer structure and air. (I would also suggest a barrier of water, as it absorbs radiation, or a coat of regolith or other space dirt or rock to repel cosmic rays.) When it comes to heat, a space habitat is like a giant thermos bottle. Solar heat is absorbed from the outside and radiates toward the center. Convection or chilled coolant could help keep the population on the edges of the habitat comfortably cool. The outer surface must be able to withstand or avoid impacts from meteorites and cosmic dust. Large mirrors or periscopes could be used to direct sunlight into the habitat.
A good location for a habitat is near Luna, for the access to raw materials and the proximity to a major trade market in Earth.
An O’Neill Cylinder is 20 miles long and 5 miles wide, and made of steel. It has a total surface area of 314 square miles. This is roughly the size of Guam, Malta or Rhode Island. A Bishop’s Ring can be larger, the size of continents, if a strong material is used, such as carbon nanotubes and graphene. McKendree Cylinders are huge at 10,000 km, or 6,200 miles, and can be linked together like a string of sausages.
Rotating habitats are extremely difficult to finance and build, as materials have to be moved from a terrestrial world into space. Care must be taken with heat dispersion and habitat size, or else some sections will be too warm and uncomfortable. Excess heat must radiate out into space. A rotating habitat is designed like a washing machine. That is, it has an outer shell that stays stationary, and an inner section that turns. You cannot see this habitat spinning in space, because the velocity would cause it to break apart.
The outer shielding super-structure can be reinforced by hydrogen and helium, which are both plentiful in space. This would be an effective barrier against cosmic radiation. Consider that Earth’s higher atmosphere has 14 pounds per square inch of pressure, preventing most cosmic radiation from reaching the planet’s surface.
The interior habitat doesn’t have to be built flat. It can have dips and rises to simulate lakes and hills. A dedicated reactor suspended in the center of the cylindrical habitat can maintain universal lighting. One difficult effect to reproduce is a natural-looking blue sky. Perhaps an additional colored layer can be inserted between the light reactor and the population level. A lot more dirt will be needed to simulate a natural landscape and agriculture, but less if hydroponics are utilized to produce food.
Bernal Sphere – First proposed in 1929, this habitat is shaped in a hollow spherical shell. This was designed for a target population of 20,000 to 30,000 people. Updates to this concept include Island One. The design has a diameter of 500 m (1600 feet) and spins are 1.9 RPM, enough to produce full Earth gravity at the equator. This is described as a long valley running along the equator, big enough for 10,000 people. It is an optimal size for air pressure and radiation shielding, and would be lit by angled mirrors. Island Two is larger at 1800 meters diameter, with an equator of 6.5 km (4 miles), and a good size for an industrial base.
Stanford Torus – This NASA design can house an estimated 10,000 to 140,000 people. The model for 10,000 people is 1.8 km (1.1 miles) wide and shaped like a doughnut. It rotates once per minute, creating 0.9 or 1.0g of artificial gravity. Spokes connect to a central hub with zero gravity, making it a good place for ship docking and some industry. The interior would appear as a river and valley with the ends curving upward. Areas in the ring would be dedicated to agriculture and housing.
Building materials would come from the moon or asteroid mining, and moved to the ring by a mass driver. The diameter of the tube is 130 m (430 feet). Six spokes linking to the hub would each have a diameter of 15 m (49 feet). The radiation shield would be composed of almost 2 meters (6 feet) or raw lunar soil.
O’Neill Cylinder – Proposed in the mid-1970s, this habitat consists of two separate cylinders, one within the other, spinning counter to each other to cancel out gyroscopic difficulties presented when aiming the habitat at the sun. The two cylinders are 8 km in diameter (5 miles), and up to 32 km long (20 miles). Each cylinder has six ‘stripes’ on it, running lengthwise. These stripes alternate as transparent windows and habitable land masses. A third ring (16 km, 10 miles in radius), would spin at a different speed to allow for farming. The industrial sector is located in the center of this ring, taking advantage of lesser gravity and benefiting some manufacturing processes. Building materials would come from the moon, shot out like a train or cannon from a mass driver.
To simulate gravity O’Neill’s Cylinder would rotate 2 times per hour. People would not notice this unless they turn their heads or drop an object, which would fall a few centimeters from the expected spot. Air pressure would be half that found on Earth, to save on gases and allowing for thinner walls. Mirrors outside the windows would reflect sunlight into the habitat. The windows would not be designed as giant panes of glass, but as smaller units in case they get damaged. The movement of the cylinders can create momentum to turn the habitat 360 degrees, without the use of rockets and saving fuel.
Continued in Part 3