Reaching space has been a great achievement. There are constantly people at the International Space Station, the Moon has been visited and unmanned spacecraft explore Mars and further celestial bodies and now even the edges of the Solar System. Since a slightly quieter period after the great achievements in the 50s to 70s there are again space news pouring in from the findings of the Curiosity rover on Mars and the greetings from far from Voyager 1 to space tourism and planning of manned expeditions to Mars. Many of us would surely like to see a manned flight to Mars happen in the future. Perhaps we want to visit the place ourselves too. With current rockets it just takes so long and is unpleasantly expensive. Therefore I am suggesting an alternative to them: a highway to Mars!

 

Traveling in space is currently to quite some extent limited by the laws of nature expressed in the rocket equation. In order to accelerate in the vacuum of space, a spacecraft needs to emit exhaust products in the direction opposite to the traveling direction. The majority of the weight of a traditional rocket is fuel, the fuel tanks are released already in the beginning of the journey and only a small part of the rocket continues to destination. Also ion engines operating with much lighter fuel emit ions with horrific speeds, which leads to the ions getting most of the kinetic energy instead of the spacecraft. The journey to Mars is long: 55-400 million kilometres. Applying current propulsion principles the trip takes months. Of course journeys to Mars may be undertaken in the spirit of historical explorers from Europe, without a rush. It is also possible to sail to Mars, for example with an electric sail (http://www.electric-sailing.fi/), which does not need fuel like a rocket, but even in that case the trip takes a long time.

 

If we can construct a continuous highway to Mars and on it use an acceleration of 1 g and a deceleration of the same magnitude from halfway onwards, a trip between Earth and Mars will take something between 2 days and 2 weeks, depending on the planets' positions on their orbits. 1 g is a comfortable acceleration for a human, and she will feel having the same weight as on Earth during such a trip. Especially for cargo traffic, it is also possible to use significantly larger acceleration.

 

The highway operates using magnetic suspension, like Maglev-trains, without touch, controlling the position of the spacecraft with a magnetic field and accelerating it with an electrical engine. As a convenient coincidence, it is cold in space allowing for superconduction for lossless energy transfers. The highway could consist of heavy rocks with the electrical parts on top, which with their weight take the role of the exhaust products in the rocket equation. Energy from the braking spacecraft can be retrieved and the energy input needed because of losses can be provided for example by solar energy. The road starts only where Earth's gravity field is already weak so a lauch system from Earth's surface is also needed. For this, there are many options, but the same electromagnetic principles have been suggested for launches too (for example http://en.wikipedia.org/wiki/StarTram). Jules Verne predicted in his novel From the Earth to the Moon from 1865, in which the spacecraft was launched by a huge cannon, that space ships of the future will move significantly faster powered by light or electricity.

 

Construction of the highway is slow as in the case of asphalt roads for cars, but once its built, it can be used for fast travel and more people have the chance to use it. The length of the highway is similar to the current world road network. In other words, the construction project is massive but doable based on size. This highway does not stay fixed with respect to starting point and destination, but twists into a spiral shape because Earth orbits around the Sun faster than Mars. The highway thus needs to be regularly recompiled. In theory, fitting twists are possible, because as the pieces of the road stay on their orbits around the Sun, either by balanced traffic in both directions or by net input of momentum with for example electric sails, its energy is always the same and the compilation procedure will not use more energy than losses due to non-idealities.

 

A literal goldmine could be achieved by extending the highway to the Asteroid belt. Among the thousands of asteroids located in the belt between Mars and the next planet Jupiter there are all kinds of chunks, from which metals could be won more easily than on planets as one does not need to dig so deep on the small asteroids and many of the asteroids might even be nearly pure metal. Treasures from the Asteroid belt and Mars could return the money spent on building the highway manyfold and make us richer as mankind both in a material sense as well as in opportunities as it would now be possible to visit Mars and for instance hike its mountains and have a beer. Possible destinations can also be found beyond the Asteroid belt. For example Jupiter's icy moon Europa is considered to be one of the most potential alternatives in space for human settlement.

 

Let's build a highway to Mars and beyond. Why not?