One of the greatest problems we face today is the cost and complexity of launching spacecraft into space; the short-term approach by NASA will probably be the use of Micropropulsion.
Microspacecraft will be in the order of 1-10 kg, and the craft's subsystems will have to be reduced by similar factors to allow worthwhile mission capabilities.
This, however, is clearly not the long-term solution. Before we begin serious deep space exploration we shall have to find other ways to overcome the launching problems and allow manned missions in large, advanced spacecraft.
The problems will be solved by large projects in Earth's orbit. The first step will be a fully-fledged space station.

Werher von Braun's Idea

Courtesy: NASA

A large permanently manned space station in Earth's orbit will crucial to any deep space exploration that we perform, as well as providing a large platform for valuable space research.
The importance of such a space station was recognised very early in the space program, with von Braun producing complete designs (the first 'wheel' design) for such a station in 1952.

This is not the first time the advantages of a space station were considered though, as long ago as 1903 Tsiolkovsky began working on ideas of a base in Earth's orbit. In 1929 Oberth first used the term 'Space Station' and performed in depth work considering the advantages of such a structure. There is no doubt that throughout the history of man and space, particularly among pioneers space stations have always been a part of the plans.
More infomation on these men and other pioneers can be found at TheSpaceSite.com Rocketry Page.

The greatest advantage of such a station will be as a construction site and a base (for maintenance, refuelling, component testing, mission base etc) for spacecraft, thus avoiding the problems of the cost of launching by removing the need to launch against the Earth's gravity.

Long-range spacecraft would be assembled and based on the stations, with construction parts and fuels being shipped from either the Earth surface (the space elevator that we shall discuss below will increase the effectiveness here) or from other places in the solar system.
There are further advantages, the station could have a quarantine area where the crew and craft can be checked for any contamination, and it could also be used to train the spacecraft crew in space before their departure.

There will also be the need for a large commercial space station for the development of space tourism, which will be a crucial industry of the 21st century. This may initially be a different part of the same station; the future could perhaps be two separate, specialised stations.

We still do not have the sort of manned station that was designed in the 1950's. While the International Space Station has been a welcome move forward, it is far from what we really need. There will be no spacecraft construction or development done on the station, it is purely a scientific base.

Why haven't we built one?

So if we have had over 50 years since the first complete designs, why are we still no where near this much-needed orbital station?

There are many technical difficulties involved that we have still not solved today, such as permanent life support, exact pressure requirements and availability of adequate power, food and water. On top of this it is probable that virtually 100% recycling of all waste products on the station will be necessary and the station will ideally generate artificial gravity (probably through the use of centrifugal forces, i.e. spinning the station). The station would also require substantial shielding from both the solar radiation and unavoidable particle collisions.

In reality we lack the construction materials and techniques for an operation that would be hundreds of times more complicated that the ISS. This together with the enormous expense of such a project has delayed the development of a fully-fledged space station.

Once again the development of nanotechnolgy will resolve a great deal of these problems, this is becoming a common theme, but it is true that most space applications will be improved with such technology. We shall look at nanotechnology in detail later on.

This is a good place to consider the need for radiation shielding as the first applications may be on an orbital space station.

Cosmic rays and solar flares produce a great deal of harmful radiation and the solar system is flooded with it. We are protected on Earth by our atmosphere, which prevents the harmful radiation reaching us. There will be no such luxury once in space; short-term exposure is not too harmful, although the Apollo mission was on standby to be called off if there was notification of a large solar flare. For more permanent stays some form of shielding will be required, the basic idea is to use 1000's of tonnes of lunar and asteroid rock to absorb the radiation. There may however be a much better way.

Excellent protection may be gained by the use of active electromagnetic shielding. This is an old idea that has become more feasible with technological improvement. It works on the basis that as the particles are charged magnetic fields can divert the radiation away from the region requiring protection.

There are several advances in technology that will be needed to accomplish this feat however. The most important is the improvement in superconductor technology, principally in developing high temperature superconducting wires and the ability to cool them in space. This would enable much simpler and lighter equipment to produce the required fields. We will also require computational solutions to particle transport in electromagnetic fields.

Space Elevator

Courtesy NASA

This would be a development that would further improve the advantages of a space station, eliminating the need for any spacecraft to have to launch from the surface or face the difficulties of re-entry.

The space elevator is a tether permanently connecting the space station to the Earth's surface, which could be used to move materials and people up and down from the space station.

It has also been suggested that it could be used as a launching system if it was connected to a mass rather than a space station. This would function by pulling the craft out of the gravity well and firing it out of the atmosphere at speeds of nearly 7 miles per send (around 11 km per second). Of course without a space station re-entry would still be a problem. As an overall package it would clearly be more desirable to have a space station, use the elevator to get raw materials up there, and build the ships onboard. It is also unlikely the technology to build a space elevator will be available before that which is required to build the station.

A space elevator would clearly be the largest construction project ever undertaken by man, the cable having to be tens of thousands of miles long, as well as requiring enormous supports (approx 50km tall) to anchor it to the Earth.

Again Nanotechnology could provide materials that would be far superior in strength to weight ratios that would be crucial to the successful completion of this project (using steel would require cables so thick it would be unfeasible). Diamondoid cables would be much thinner but at the same time much stronger and more flexible, advanced nanotechnology could also provide active materials, allowing the cable to detect any faults and repair them itself!

Space Elevator (electromagnetic)

Courtesy ChaseDesigns

Further to this it would also make construction of such a large cable much easier, by using nanorobots in space. Using nanotechnology to build the cable in space would save a great deal of cost and remove many difficulties.

A basic space elevator would use some form of mechanical device to move payloads up and down, but we may be able to miss out this stage and build much more advanced space elevators that would be powered using electromagnetism. Electromagnetic propulsion can be used today to make a train hover and travel at tremendous speed, by eliminating friction. The same idea could be used here, with rings of superconductors creating powerful electromagnetic fields to accelerate pods, containing cargo or passengers, up to the space station.

Whichever method is used the construction of a space elevator in conjunction with a space station will virtually eliminate any cost associated with getting material and people into orbit.

SPS

Courtesy NASA

This is also a good point to quickly discuss the SPS, which will be important to both the space program and to everyday lives on the surface. Peter Glaser initially proposed this idea in 1968 as a means of replacing fossil fuel and nuclear power for providing surface energy. It can be imagined as a vast solar array that orbits above the atmosphere, harvesting the raw solar energy from the Sun and sending this energy down to Earth as a microwave beam. The beam is received on Earth and converted into electricity.

The major problems for the development of an SPS are:

1. Once again the sheer size of the undertaking (time and money)
2. the inefficiency of the current technology, for example current solar panels have only about 30% efficiency

Yet again nanotechnology will provide answers to both problems, and together with the availability of general space access, may make this an economical project. It is likely that a SPS will closely follow a space station project.

Go on to the Future Improvements to Chemical Propulsion
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