VOA常速英语:Former Astronaut Develops Powerful Rocket

As scientists develop plans one day to send humans to Mars, they know the journey will involve many hazards for the astronauts, including possibly many months of exposure to dangerous radiation outside Earth's magnetic field. But if they decide to use a rocket developed by former U.S. astronaut Franklin Chang-Diaz, the trip to the red planet might take only 39 days. The plasma rocket could be the answer to many space travel challenges.

In this giant vacuum chamber at the Ad Astra company's Houston headquarters, technicians are testing the Variable Specific Impulse Magnetoplasma Rocket, called VASIMR for short.

“That exhaust is low-density plasma, so we can contain it pretty well here in the chamber," said Physicist Christopher Olsen. He uses instruments to measure the flow of ionized particles produced by heating a gas to very high temperatures. “We can measure the ion velocity, the ion flux, the force, the temperature coming out of it. There are a lot of parameters that we have the ability to look into.”

The inventor of VASIMR is Ad Astra president and chief executive officer Franklin Chang-Diaz. “It is a rocket that works on the basis of plasma, plasma being a super-heated gas, a gas that is heated to temperatures close to the temperature of the sun. These assemblies here are antennas that actually inject the electromagnetic waves which transform this gas into the plasma," he said.

Chang-Diaz said a gas so hot cannot be contained by any known material, so something else is used to contain and direct the flow. “We use the magnetic field as the enclosure, as the ducting that actually guides this very hot gas and produces rocket propulsion," he said.

The plasma propulsion is not used to launch a payload into space -a conventional chemical rocket would be used for that. Once in space, the plasma engine and the solar panels that power it would be assembled. Chang-Diaz says one big advantage of this propulsion system is the relatively small amount of fuel it uses. “Because the specific impulse of this rocket is much higher, the amount of fuel required to carry out a certain task is that much less," he said.

Franklin Chang-Diaz, who was born and raised in Costa Rica, flew on seven U.S. space shuttle missions.

He launched Ad Astra after he retired from NASA in 2005, but the company continues a close association with the U.S. space agency.

Mission planners at the nearby Johnson Space Center see VASIMR as a possible means of getting astronauts to Mars without exposing them to as much harmful cosmic radiation as they would get on a conventional rocket journey, lasting many months.

Chang-Diaz says replacing solar panels with a nuclear reactor would provide the necessary power to VASIMR for a much faster trip to the red planet. “The marriage of the engine to the nuclear reactor would deliver to you an engine that could go very fast and we could do a mission to Mars that would take about 39 days, one way," he said.

Such a mission is still many years away, but Chang-Diaz says his rocket could be used much sooner for missions to the International Space Station or to retrieve or position satellites in Earth orbit.

In a few years, under a contract with NASA, Ad Astra plans to send a VASIMR engine to the International Space Station for testing.