The time when ordinary people can go into space as tourists is fast approaching believes space visionary Sir Arthur C Clarke. He told BBC News Online that it is about time we built a hotel in space.

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Consider the attractions and appeal, he said. "Where else could you get to see a sunrise and sunset every 90 minutes."

His call for a renewed effort to get tourists into space comes on the day of the first of two conferences this year devoted to space tourism.

The conferences, in Germany and in the United States, are tapping into the feeling that advances in technology are at last bringing the space tourist concept within reach.

Thriving industry

Even the head of Nasa, Dan Goldin, has said it will happen. "In a few decades there will be a thriving tourist industry on the Moon," he recently told American politicians.

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Testifying before the Senate Subcommittee on science, technology and space, Goldin said that "space tourism will soon become affordable."

It is very difficult to estimate the cost of a trip into space but sums of £50,000 for a one-hour flight have been mentioned.

Sir Arthur points out that the market for space tourism could be enormous. "In many countries, more than half the people who were asked responded that they would go into space as a tourist."

Sir Arthur backs space hotels

A handful of US companies have advanced plans to build the prototype of a space passenger vehicle.

Testing is planned for later this year and analysts expect that at least one of the spacecraft will prove viable.

Sub-orbital spaceplanes

In the UK, too, expectations are high. "Passenger flights to space will start within a decade," said David Ashford of Bristol Spaceplanes, a small company with big plans.

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He believes that the key factor that has prevented many companies from developing plans to build their own spacecraft will soon be overcome: "The cost of sending people into space will be reduced by a factor of a thousand within the next 15 years," he said.

This will happen when rocket technology merges with aeroplane technology. "Aeroplanes are reusable and cheaper and they bring the concept of a sub-orbital spaceplanes within the range of a small company."

The space shuttle tanks are over 30m (100 feet) long

One concept that Bristol Spaceplanes are working on is "Ascender", a small three-person craft designed to go into space but not into orbit.

In a 30-minute flight, it would reach an altitude of 100km (62 miles) and spend two minutes there. This is above the altitude of 80km (50 miles) that the United States Air Force regards as qualifying for astronaut wings.