The impact of science fiction writer Arthur C Clarke is still being felt, following the news that two more of his ideas are being researched for real.

The Defence Advanced Research Projects Agency (Darpa) is to develop a weapons system first suggested in Clarke's 1955 work Earthlight which fires tubes of molten metal using electricity.

Clarke described the bolts as passing through spaceships "as an entomologist pierces a butterfly with a pin".

Darpa's Magneto Hydrodynamic Explosive Munition (MHEM) programme employs the same principle, but uses an explosion to generate the electrical charge needed to fire the projectiles, rather than huge capacitors as Clarke suggested.

Meanwhile, the Finnish Meteorology Institute (FMI) is planning to put a huge solar sail in orbit around the Earth to prove the concept of using solar wind for propulsion. Clarke first explored the idea in the 1965 short story Sunjammer.

The sail will hopefully go into orbit in the next few years, albeit in a radically different format to that envisaged by Clarke. The Finnish idea is to positively charge thin wires which will pick up the Sun's ions for propulsion.

"The electric sail might lower the cost of all space activities and thereby, for example, help make large solar power satellites a viable option for clean electricity production," said Dr Pekka Janhunen from the FMI.

"Solar power satellites orbiting in the permanent sunshine of space could transmit electric power to Earth by microwaves without interruptions.

"Continuous power would be a major benefit compared to e.g. ground-based solar power where storing the energy over night, during cloudy weather and winter are tricky issues especially here in the far north."

If the project goes ahead it will be the first time that a solar sail has been deployed in orbit. Enthusiasts tried to put a similar craft, Cosmos 1, into orbit in 2005 but the rocket carrying it failed.