Space Flight

The biggest problem with space colonization is the space flight and especially the costs associated with it. In order to lower costs, rocket engines should be replaced with more inexpensive engines. New ways of propulsion would make space travel faster and more convenient. In addition, spacecraft should be reliable in order for the large scale colonization to be successful.

Space Access

Traditionally we have used rocket-powered spaceships to escape the gravity of Earth. However, if we want to conquer the space, we have to develop alternative methods in order to make space travel more inexpensive. There are multiple ways to do this, and here are a few possible options.

Space Elevator

Of the alternative ways of space access, space elevator is probably the best known. In practice, space elevator would be a long rope, that would descend from the point above the Earths orbit to the surface of Earth. With this rope, equipment, spaceships and people could be transported in to space. There would be a counterweight on the other end of the rope, which would basically mean that not much energy is needed in order for the space elevator to stay functional.

The problem with the space elevator is that the rope must be able to withstand its own weight. At the moment, we don’t have any materials that would be strong enough to be used to build a space elevator on Earth. However, some of the materials we have, could be used to build a space elevator on the Moon or on Mars. It is very possible, that the first space elevator could be built to the Mars, and the resources of the planet could be transported back to Earth with help of the elevator.

Launch Loop

Launch loop was suggested by Keith Lofstrom to propel spacecraft in to space. In practice, it would be a structure that would be over 2 000 kilometres long and 80 kilometres high. In resting mode, the loop would rest on the ground, but with the help of its rotors, it would raise up to its operating height. After the launch loop is in operating mode, spacecraft could be propelled to high enough speed with electromagnetic force.

The problem with the launch loop is that it might be very vulnerable to failures. If a malfunction would be to happen, it could destroy large part of the structure when it would fall to the ground. However, building a launch loop would be possible with the current materials we have, unlike the space elevator. Launch loop would be relatively inexpensive to operate, after it has been built. It requires a lot of space, but there is still enough free land area on the Earth for it.

Projectile Launch Systems

Projectile means an object, that is propelled to fast speeds. With great speed, the object can leave the gravity of the planet or other object. Projectile launch systems would use electromagnetism or chemicals to propel spacecraft to great speeds. If the launch system couldn’t achieve a high enough speed, it could be assisted by traditional rocket engines. The problem with projectile launch systems is the drag from the atmosphere, which is greatest in the lower parts of the atmosphere. In practice, projectile launch systems would work the best in planets or objects where there isn’t a strong atmosphere.

Which Space Access Method Will Be Used?

There are multiple suggestions for efficient space access, but so far we’ve only been using traditional rocket engines. When space colonization becomes a reality, some of these systems described will quite surely be used. Especially the space elevator is an interesting option because its relative inexpensive and safe. Projectile launch systems would probably be built on places without strong atmosphere, such as the Moon.

Spacecraft Technology

In addition to space access technologies, the technology of spaceships should be more advanced, as they are one of the most important parts in the space colonization. The size should be drastically increased and the propulsion methods should be more advanced, in order to make large-scale space colonization possible.

What Makes a Good Spacecraft?

Interplanetary space travel requires properties from spacecraft, that they do not currently possess. We do, essentially, have all the technology required for them. The problem will be, unsurprisingly, the costs. Building spacecraft for interplanetary travel will be very expensive, as they would need to be built very carefully, and ready-made plans don’t exist yet.

The spacecraft should be able to ensure survival of humans for many months, even for years. Basically, this means providing breathable air, water and food. We do have experience regarding this, as the space stations we’ve built have been able to support life for months without resupply. For long trips, artificial gravity should also be provided to prevent health problems.

Spacecraft should also be well protected from deadly space radiation. According to Russian studies, removing deuterium from the drinking water could prevent cancer formation. However, more studies are needed. It would be possible to build shielding from space radiation, but traveling with them will be considerably more expensive. It’s possible that the first interplanetary spaceships have light radiation protection, that will be able to prevent most of the harmful effects of the radiation.

The spacecraft should also be really reliable. If a malfunction would be to happen during the trip, it won’t be practically possible to send help. Therefore, malfunctions are not an option, unless we want to see first human fatalities in outer space.

When moving beyond our own Solar System, requirements for spacecraft are a lot more demanding. When traveling vast distances, spacecraft would remind us of large space habitats, that would be able to survive autonomously for long periods of time. It could be possible to set humans asleep for hundreds of years, but we do not currently possess this technology.

Propulsion Methods

Propulsion method is a way to provide thrust to a space ship. Larger the thrust, the faster the spacecraft can move. Leaving the gravitational field of planets and other objects requires a huge amount of thrust in short periods of time. So far, we have mostly used rocket engines, but other methods need to be developed for large-scale space colonization.

Rocket Engines

Rocket engines are the traditional way to move space ships. They are based on a chemical reaction in rocket propellant, which produces heat, which is after that changed to produce kinetic energy. With rocket engines, it is possible to gain large amount of thrust in small bursts and we know their capabilities quite well. Current space exploration has been done almost exclusively with rocket engines.

The problem with rocket engines is that the spaceship are only able to carry limited amount of propellant. Therefore, movements in space need to be carefully considered and fuel used conservatively, which also means that fast speeds are hard to achieve. Also, the limited resources on Earth and possible air pollution limits their large-scale usage.

Electromagnetic Engines

Electromagnetic engines use electricity to produce thrust. In practice, they collect solar energy, and cause an electric reaction in the propellant, which then produces ions that speed up the spacecraft. In some cases, its possible to use a magnetic field of a planet, instead of ions.

Electromagnetic engines are already in use, and many satellites keep their orbits stable with them, for example. When comparing to rocket engines, electromagnetic engines consume a lot less propellant. With them, it is possible to travel to the outskirts of the Solar System, but intergalactic travel wouldn’t be very feasible. They are not able to produce large thrust, but more continuous, which means that its not possible to leave the gravity field of Earth with them.

Nuclear Engines

Nuclear engines could also be used to propel the ships. One option is to use nuclear power to heat hydrogen, which would produce thrust similarly to rocket engines. According to calculations, engines like this would be about twice as efficient as the traditional rocket engines.

Fission reactors could be used also as a part of an electromagnetic engine. Currently, electromagnetic engines use solar power. If fission reactor would be used instead, the electromagnetic propulsion engines could be used in the farthest points in the Solar System, where solar power is not readily available.

Fusion reactors could be used with deuterium, tritium or helium-3, for example. Fusion engines could allow large thrusts, but engines would be very heavy. If using fusion power becomes possible one day, using it would probably be our best option.

Solar Sail

Solar sails are built of thin and lightweight materials. They collect radiation pressure from the Sun and from the other stars, that eventually propel the spacecraft. Solar sail is proven to be working. Japanese started their solar sail project, IKAROS, in 2010, and it reached Venus in under a year. It could be possible to send artificially radiation beams to solar sails to propel them faster.

The upside of the solar sails is that they do not require propellant at all. Solar sails would allow traveling of vast distances not worrying about running out of fuel. However, their thrust at a given moment is quite small. This means that other methods are better for leaving gravity field or for short-distance travel. Solar sails could be used to explore the far areas in our Solar System and possibly other solar systems also.

Magnetic Sail

Magnetic sail resembles solar sails quite a lot. Instead of radiation pressure, magnetic sails use magnetic fields to create propulsion. Essentially, magnetic sail is an long superconducting wire, that creates a magnetic field. This magnetic field reacts with magnetic fields of planets and plasma winds, creating thrust.

The upside of the magnetic sail is its simple structure. Its essentially just a long wire of superconducting wire, which makes it lightweight and inexpensive. The problem, which also plagues solar sails, is the low thrust in any given moment. This makes it useful only for long distance travel, such as outer edges of our Solar System of other system. Magnetic sail can also be used to reduce speed in interstellar space, as the small amounts of hydrogen there can react with the magnetic sail.

Which propulsion method should we use?

At the moment, we are forced to use rocket engines, if we want to leave the Earth, unless an alternative system for space access is built. Rocket engines and electromagnetic engines are quite common, but we have little experience of magnetic and solar sails. We will be probably using traditional technologies when first colonising the nearest objects, but will be using magnetic and solar sails when exploring objects that are far, unless better technologies are developed.

Summary

Before colonising space, there are multiple problems with space travel that we need to solve. First of all, we have to develop ways to leave the gravitational field of Earth, and other planets and objects. Secondly, spacecraft should be developed in a way, that they would allow safe travel for long distances. Thirdly, propulsion methods should be developed further to make traveling long distances inexpensive and fast.