By Duncan Walker
BBC News Online Magazine
The prospect of a revolution in air travel has been raised by Nasa's successful test of a 5,000mph plane. But are we likely to see similar advances in other forms of transport?
Nasa's scramjet powered plane could change flying
The way we get about has a profound impact on the way we live - affecting where we set up home, work and holiday.
Nasa scientists say their experimental X-43A jet has the potential to make the world a much smaller place. It has already led to predictions that passenger planes will one day fly from the UK to Australia in two hours.
But apart from the huge cost implications, governments are increasingly sensitive to environmental concerns and may resist the use of technology that could harm the planet.
So, dusting off the crystal ball, what changes might come in the way we get around? What big ideas are out there, and do they have any chance of seeing the light of day?
PERSONAL AIR TRAVEL
The idea: Flying cars
Developments in microlight technology will make it possible for everyone to own what are, in effect, flying cars. They will have closed cabins, heating, stereos and room for two people.
Microlight wings could be removed, to make them like cars
You will take off from a field or runway near your home and fly to towns and cities across the UK, or mainland Europe.
After landing, you will detach the fixed wing from your vehicle and continue your journey by road - right up to your final destination - just as if you were travelling by car.
Fuel efficient engines and the advantage of being able to travel as the crow flies - rather than by winding roads - will keep costs and the environmental impact down.
Will it happen?
It's not that far fetched. Microlight firm Pegasus is already building closed cabin vehicles, while some aircraft can travel at speeds of up to 130mph and fly for up to four hours.
Pegasus boss Bill Brooks says a combined three wheel car and microlight could cost about £30,000.
The prospect of horrific crashes and air rage spring to mind.
The British weather often prevents microlight flying, and you can only travel during daylight hours. You need an airfield and learning to fly isn't easy.
There is also the question of developing propellers that can safely power cars.
"Whilst taxiing up the road under propeller power, I met a group of cycling proficiency children who I thought I'd chop up, so stopped and pushed the rest of the way," says Bill Brooks of an early test run.
FLYING FOR FUN
The idea: Jet Packs
James Bond used a jet pack to escape a French chateau after killing his enemy Jacques Boiter in Thunderball.
The idea of jet packs has been around for years
The idea was also a hit when a stuntman flew around on one during the opening ceremony of the 1984 Los Angeles Olympics.
You will be able to use the device - roughly the size of two scuba tanks strapped to your back - on short journeys. Perhaps for going to the shops.
They will be handy for retrieving cats from trees, cleaning hard-to-reach windows and arriving in style at a party.
Will it happen?
It's looking increasingly unlikely - despite the fact we have already seen early prototypes in action.
It remains difficult to build a cheap, reliable version which has a practical use.
"Lots of people set their pants on fire and went off in funny directions when they tried them out," says Austin Williams of the independent Transport Research Group.
And there's always the issue of whether you really need one.
The idea: Driverless cabs
These computer-controlled pods will take you wherever you want along a fixed route, whenever you want to go.
Computer-controlled driverless cabs could soon be in Cardiff
For the price of one person's bus fare, several people can ride at speeds of up to 25mph, with fences and elevated sections used to guard against accidents.
There will be little, if any, wait for use of the cabs, which will leave from stations and will be accessed by pre-paid smartcards.
The cabs, which will travel on a 1.5m-wide track, will use 75% less energy per passenger than a car and 50% less than a bus.
Will it happen?
There's a good chance it will. Testing has taken place in Cardiff, where developers hope to have 160 driverless cabs running by 2006.
"We have had a lot of interest from elsewhere in the country," says ULTra chief executive Martin Lowson. He says Corby and Daventry are both looking at the idea, as are Heathrow and East Midlands airports.
Persuading investors and politicians to back the scheme. The possibility of vandalism against the cabs.
There's also the visual impact of elevated sections and possible disruption installing the tracks.
The idea: Safe, environmentally friendly cars
Cars of the future will do far less damage to the environment and will be equipped with futuristic safety devices to minimise the number of accidents and deaths.
Engines could be powered by a rubbish-fuelled reactor - to make use of all the waste we produce. Alternatively, petrol may be replaced by fuel cells which separate hydrogen from oxygen in water.
Rounder and softer vehicles will appear as safety laws shape vehicle design. They will have sensors to detect pedestrians and other cars and will have air cushions inside and out.
They may also run along invisible tracks, via satellite technology. Traffic flow could even be controlled with vehicles "talking" to each other to regulate flow - meaning the end of traffic jams.
Will it happen?
Cars powered by fuel cells are already being developed, says the Society of Motor Manufacturers and Traders.
"Twenty years from now expect to see examples on our roads," it predicts. "With hydrogen power, nothing comes from the tailpipe but water."
So many millions of people own cars that it will be years before environmental and safety improvements become commonplace.
The technology is still experimental and it remains to be seen whether car firms have the ability and commitment necessary.
The idea: Magnetically levitated trains
Maglev trains already run in China
Trains using "Maglev" technology will zip between cities at 260mph - twice the maximum speed British passengers are accustomed to.
The system uses a combination of magnetic attraction and repulsion for lift and forward movement on specially built tracks.
In effect the trains float on an electromagnetic cushion, which minimises friction.
Because journey times are significantly shorter, people will be encouraged to leave their cars at home.
Will it happen?
The first commercial Maglev train line is already in operation between Shanghai city centre and Pudong airport.
The technology was invented in Britain and a Maglev shuttle was actually built between Birmingham International Airport and the nearby railway terminal.
But it was abandoned in 1995 because it was unreliable.
The costs. Chinese authorities were forced to abandon a Maglev line between Shanghai and Beijing because of the phenomenal price tag attached to the project.
High-speed trains already in use in Japan and Europe can travel nearly as fast as maglev trains, but on standard tracks.
What travel innovation would you like to see? We'll pick 10 of the best for a vote
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