Tech UPTechnologyFranklin Chang-Díaz:

Franklin Chang-Díaz:


The Space Shuttle, which was designed to put people and objects in Earth orbit, has successfully accomplished its mission, but going to other planets and solar systems will require much more advanced interplanetary propulsion engines. One of the most promising proposals is the VASIMR (Variable Specific Impulse Magnetoplasma Rocket), designed by Franklin Chang Díaz, a physicist at the Massachusetts Institute of Technology and a NASA astronaut. Chang-Díaz, whose passion for spaceships comes from afar? “I built my first rocket when I was a child, in Costa Rica, playing with my cousins. It was an assembly of cardboard boxes, with chairs inside. I even had a radio”? , spoke to VERY about his invention, which could propel spacecraft to Mars on trips of less than four months if it manages to overcome some technical and financial hurdles.

Can you travel to Mars with a conventional rocket?
-With rockets powered by chemical fuels, a mixture of solids and liquids, that we still use today, a trip to Mars would take at least 10 months in an unsafe and limited spacecraft. Fuel would be dead weight for most of the trip, taking up too much space and leaving little room for crew and payload. A long trip in these conditions would be a severe punishment for the organism. Months of exposure to microgravity weaken muscles and bones, and persistent radiation from space would kill immune systems. The chemically powered rocket allowed us to go to the moon and establish a permanent presence in space, but to explore the solar system we have to develop a new type of propulsion.

What qualities should an interplanetary ship have?
-It must be safe, fast, reliable and capable of interrupting the mission and returning to Earth in the event of a major failure. Its propulsion system has to effectively steer the ship during the cruise phase and perform the maneuvers correctly at the departure and destination points.

Is plasma technology the solution?
-Yes. Plasma is a superheated, electrically charged, ionized gas whose energy can be converted into impulse. That’s what we’re working on with a prototype of the Vasimr engine, the VX-10, at the Advanced Propulsion Laboratory at the Johnson Space Center in Houston.

How does it work?
-It is like a balloon to which the knot is untied: the air that is coming out makes it run everywhere. We use hydrogen gas that we heat to extreme temperatures. The heat of the particles equals speed. To heat the gas, we bombard it with radio waves, similar to what a microwave does to boil water. Thus the atoms lose their electrons and the gas is transformed into a plasma as hot as the Sun. This plasma is like a soup composed of charged particles: positive ions and negative electrons. Plasma, considered the fourth state of matter, is found naturally in lightning, nebulae, and the interior of stars and reaches temperatures of hundreds of thousands of degrees. It can melt any material where you intend to store it.

And how do they control it?
-By magnetic fields. It is the only way to handle plasma. We use very light electromagnets and magnetic coils made of superconducting materials to create a magnetic nozzle, a kind of invisible conduit that carries the plasma without it touching the walls of the motor. Then it comes out of the engine exhaust at extreme speeds.

What distinguishes the Vasimr engine?
-The key is in the V of Variable: the nozzle can change shape to increase or decrease the flow of the plasma and the speed of the spacecraft, allowing it to intelligently decelerate at the end of the trip, when it approaches the orbit of the planet destiny. The rocket is designed to cross the “hills” and “valleys” of space in the same way that a car with gears climbs a mountain pass. That way you get a much more efficient use of fuel and can drive more load in significantly less time.

What does Vasimr offer?
-On the one hand, shorten the duration of a spacecraft’s flight to Mars by more than half: from eight months to just over three. I am convinced that this is how we will reach the Red Planet and the rest of the Solar System. In addition, the engine could be used to recycle hydrogen discarded by the International Space Station and keep the laboratory in orbit without the need to refuel with deliveries of fuel from Earth.

Does the engine protect astronauts from space radiation?
-The magnetic field produced by Vasimr and hydrogen fuel act as a protective shield from radiation, which is one of the most serious long-term hazards faced by mission crews. In addition, the ability to open and close the nozzle allows you to interrupt a mission on the spot.

How did you come up with this system?
-After many years of work in controlled fusion research at the Charles Stark Draper Laboratory of the Massachusetts Institute of Technology, where we basically aspired to create a small sun, confining plasma inside a magnetic container for a long period of time to achieve fusion. The idea was to one day produce a fusion reactor that would give us electrical power to eliminate the world’s energy problem. But that has not been possible until now.

Could Vasimr work for the space shuttle?
-The space shuttle is not suitable for going to Mars. It is like a bullock cart compared to the Vasimr. Its main engine, which is the best chemically-powered space engine there is, has a specific impulse of 465 seconds (it is a way of measuring the efficiency of a rocket). Our VX-10 prototype recently produced a specific 11-second pulse using deuterium, which is an isotope of hydrogen, as fuel.

Do you think hydrogen is the ideal fuel?
-We have experimented with argon, helium and xenon, but hydrogen and its isotope deuterium are ideal because they can be stored at cryogenic temperatures, and that means that they can also be used as coolers for the magnets that contain the plasma. In addition, it is the most abundant element in the universe and travelers of the future could obtain it anywhere. We are also experimenting with hydrogen-rich substances, such as ammonia, whose advantage is the ease of storage.

How and when will you test the Vasimr?
-We intend to take it to the International Space Station around 2008 to show that the engine can propel the laboratory and keep it in orbit by counteracting the tiny but constant frictional force that the station receives from the upper layers of the atmosphere.

Are you investigating with some other advanced space transportation system?
-We are working with another type of plasma engine, which is the ion engine. Both this and the Vasimr are nuclear electric propulsion engines. In order to feed them, the Prometheus Project is being developed. Solar sails and space elevators are also studied.

How much does the Vasimr project cost per year?
-One million dollars. Funding comes from various parties, including NASA and the Department of Defense.

Some critics say that is a lot of money for an engine that still does not produce tangible results. What do you think?
-My project has been praised by the most prestigious publications and has received awards, but criticism is never lacking. I think they are part of the natural process to understand something new.

The Vasimr project seems to have stood the test of time, since it was conceived 20 years ago and has been in the laboratory for more than ten years, and that is not very often …
-The Vasimr could be the precursor to the great dream of all of us in the space program: a fusion rocket. Someday future generations will use this technology to get to the stars fast. Now we are preparing the ground to achieve this.

Angela Posada-Swafford

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