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NOVA ScienceNOW

Franklin Chang-Díaz: Expert Q&A

  • Posted 07.20.09
  • NOVA scienceNOW

On July 20, 2009, Franklin Chang-Díaz answered questions about plasma rockets, eating tortillas in space, and much more.

  Franklin Chang-Díaz

Franklin Chang-Díaz

Franklin Chang-Díaz is a former NASA astronaut and the current chairman and CEO of Ad Astra Rocket Company.  Full Bio

Photo credit: © NASA

Franklin Chang-Díaz

Franklin Chang-Díaz is a former NASA astronaut and the current chairman and CEO of Ad Astra Rocket Company. Born in Costa Rica, he moved to the United States to pursue his dream of becoming an astronaut. Along the way to achieving that goal, Chang-Díaz earned a B.S. in mechanical engineering from the University of Connecticut, and a Sc.D. in plasma physics from the Massachusetts Institute of Technology. As an astronaut, he's flown on seven spaceflights—tying the record for most flights—and spent an impressive 1,601 hours away from Earth. On this planet, he enjoys music, flying, and scuba-diving. For his work, Chang-Díaz has received many honors in his adopted land, the United States, and his motherland, Costa Rica. He is married to the former Peggy Marguerite Stafford of Alexandria, Louisiana, has four daughters, and his mother, brothers, and sisters still reside in Costa Rica.

Q: What will it take for the U.S. to make another "giant leap" in space technology? (It seems that there is a lot of industry inertia in using proven technology based on a lot of risk aversion.) Bill Tandy, Boulder, Colorado

Franklin Chang-Díaz: It does take leadership and vision from the very top. However, the private sector is becoming an increasingly important element in the equation, driven by entrepreneurship and new business opportunities. It may very well be that the new driver for space exploration does not come from the traditional government sector but rather from a more agile and dynamic private sector.

Q: How would you control a plasma rocket since it is traveling at such high speeds? Joanne, Albany, New York

Chang-Díaz: The trajectories of space vehicles, regardless of their speed (so long as we don't get too close to the speed of light-unlikely anytime soon) are fortunately determined by laws of physics that we understand well today. Controlling the speed of a spacecraft is done by pointing its rocket engines in particular directions at particular times during the flight. In the case of VASIMR, we would accelerate continuously half way to Mars and then turn the ship around to fire the rocket backwards so we begin gradually slowing down as we reach the planet. Eventually, the planet's own gravity pulls us in, and we finish the breaking maneuver by diving a little into the planet's atmosphere. The friction of the air on the ship slows it down to an acceptable final speed so that conventional chemical rockets can take over and do the landing. We have produced a video that shows this that you might like to see at http://www.adastrarocket.com/plasmarocket.mpg

Q: If you manage to create a rocket that will be able to heat argon up to millions of degrees F, what will you construct the rocket out of in order to withstand such extreme temperatures? Would being in space cool the rocket's body to a point where the parts of the rocket would not melt? Would the fact that the plasma is shooting out the back of the rocket save the body from melting? Lynette BW - Hampstead Middle School teacher 8th grade, Hampstead, New Hampshire

Chang-Díaz: The plasma is so hot that no known material would be capable of "holding" it, so we do not use "materials" to do so. Fortunately, plasma is also an electrical conductor and, as such, it responds very well to magnetic and electric forces. We use a magnetic force field to contain the plasma and electromagnetic waves to heat it (so nothing really touches it). The magnetic field acts as an invisible "duct," which of course, being a force field, does not melt. We call this "duct" a magnetic nozzle and it is one of the key components on the VASIMR engine. You can find a good explanation of this at http://www.adastrarocket.com/VASIMR.html

Q: Dr. Chang-Díaz,

With the idea of your plasma drive, do you believe that the idea of a "warp" drive can be developed in time? And I do believe that your plasma drive is just the first step. What is the temperature range of your plasma drive? David Elliott, Jackson, Michigan

Chang-Díaz: Warp drive requires a major upgrade in our understanding of the laws of physics. I am, however, an eternal optimist and I believe that someday this knowledge will come to us. Until then however, VASIMR provides a stepping-stone to much faster space travel than is possible today, and its development will open the entire solar system to us for exploration. This will keep us busy for a long time and make humanity a true space-faring species. VASIMR is also a precursor to fusion rockets, which will give us extremely powerful engines, capable of accelerating continuously at nearly 1g. This will provide us with an "artificial gravity," and the astronauts will not just travel fast but also will not be debilitated by long exposure to weightlessness. Ultimately though, the "Holy Grail" in space propulsion is Warp drive—hopefully some day that will be possible.

Q: I understand the basics of a plasma rocket, but what are you using to heat the gas? To get something to a million degrees, it seems like that would take a lot of energy, which would take a lot of fuel. Pat Bradford, Huntsville, Alabama

Chang-Díaz: We heat the plasma with electromagnetic waves, not unlike the way one heats food today in microwave ovens. We use radio waves of lower frequency than microwaves, because the hardware that produces them is a bit more efficient and lightweight, suitable for space, but the principle is basically the same. The plasma will reach extremely high temperatures as long as we contain it properly and not let its heat escape too quickly. This containment is done with very strong magnetic forces to which the plasma responds. You can have a look at http://www.adastrarocket.com/VASIMR.html

Q: How would you protect the rocket from small debris tearing through it traveling that fast? Very cool idea by the way!! Thanks, Nick Nick Palassis

Chang-Díaz: Space debris is a real problem even in today's rockets. We have been developing special material shields that are used in spacecraft now. The problem with space debris is concentrated near Earth due to all the derelict satellites we have put in orbit and are no longer usable. In the open interplanetary void however, the collision with debris is less likely—though still a matter of concern. We will have to build our ship with sufficient "redundancy" so that it can tolerate some of these impacts and not be completely crippled. By the way, in a side note, our "space ship" Earth has no such redundancy should a wayward asteroid decide to cross our path, something to think about...

Q: Is it possible to produce the high temperatures needed by static sparks? (For instance, can you make and contain a huge bolt of lightning using nuclear fuel? Thanks and good luck. Chuck Charles P. Richardson, Elkhart, Indiana

Chang-Díaz: Hmm!! That would be hard to do. Capturing large quantities of energy delivered in a short time is always very hard. It is akin to capturing the energy of a bomb. There is actually a project that approaches this though. It is called the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. They use gigantic lasers that all concentrate their light onto a small central point where a tiny piece of deuterium-tritium ice is heated to hundreds of millions of degrees in a billionth of a second. The hoped for result is a miniature Sun that explodes like a tiny hydrogen bomb and releases fusion energy. The hope is to capture this energy as useful electricity.

Q: I've been hearing about plasma engines for sometime. The story was, a favorite book review once said, 'Detailed sketches and sketchy details'. What makes your plasma generator practical?
Thanks! Anonymous

Chang-Díaz: A lot of sweat and hard work, the transition from physics feasibility to engineering practicality is what we are witnessing now in our laboratory today. But there is still a lot of work ahead. It does remind me of a similar transition in the evolution of the automobile engine, an extremely complex system that, over time, has become extremely practical. Most people have no idea when they turn their ignition key in the morning when they go to work what it has taken to bring such a complex system to such a high level of practicality.

Q: Why is xenon used more often to create plasma than other gases? Anonymous

Chang-Díaz: The short answer is: because it is easy to ionize and heavy enough to provide a good kick.

Xenon, however, may not be suitable to feed a robust space propulsion infrastructure, as the world's supply of the gas is quite limited. It costs about $5000/kg to buy laboratory-grade xenon, so scientists are investigating other alternatives, such as argon ($40/kg) and, for deep space missions, the choice may be hydrogen, the most abundant element in the known universe.

Q: What is the difference between plasmas in very hot places like the Sun and plasmas created with lasers, microwaves, electric fields etc? Harrison Becker

Chang-Díaz: There is really no difference. One of the goals of controlled thermonuclear research on Earth is precisely to create a small Sun in the laboratory, so we can learn to harness the power of thermonuclear fusion to provide us with abundant energy.

Q: Can you apply your technology to reduce the fuel consumption of airplanes? This may be quite a challenge; however, if the technology were developed it may greatly reduce the greenhouse gases that airplanes produce. Anonymous

Chang-Díaz: Plasma technology in general has many more uses beyond rocket propulsion. There are techniques to improve the combustion efficiency of gasoline and other fossil fuels in our conventional engines with small plasma discharges that stimulate the chemical reactions that control combustion. There are many others. I would suggest you have a look at this document http://books.nap.edu/openbook.php?isbn=0309109434

Q: Dear Mr. Chang-Díaz,

While in space, what was your favorite food? According to the Travel Channel, tortillas were introduced to space as an alternative for bread. Did you, on any of your many missions, experience any zero-G tortillas? Mark Martinez, Portland, Oregon

Chang-Díaz: Yes, in all of my missions. Tortillas are very practical in space.

Q: What's so special about argon and xenon that makes them so widely used in plasma engines? Perry High School 9th grade, Gilbert, Arizona

Chang-Díaz: The short answer is: Both are easy to ionize and heavy enough to provide a good kick.

Xenon however may not be suitable to feed a robust space propulsion infrastructure, as the world's supply of the gas is quite limited. It costs about $5000/kg to buy laboratory grade xenon, so scientists are investigating other alternatives, such as argon ($40/kg) and, for deep space missions, the choice may be hydrogen, the most abundant element in the known universe.

Q: I watched the NOVA episode where you explain the methods that will be used in the future to propel man into the farthest reaches of space, to start, Mars. Your company is developing a rocket based on your thesis. Perhaps I did not hear you mention the type of element that will be used to create the plasma. I thought that one of the most abundant elements present on Earth is probably the best to use, and that is sulfur. It is almost free and accessible from any place where there is a volcanic vent.

Could your method utilize sulfur? Mind you that if other planets are also made in the similar manner as Earth, the feasibility of harvesting sulfur in places other than Earth makes traveling into other solar systems or planets at so called "warp speeds" or at the speed of light an attainable feat.

I hope that you can make this a reality for the future of mankind.
Best regards, Nelly Nelly Villacreses, Takoma Park, Maryland

Chang-Díaz: We have been working with argon as the main feedstock gas to make the plasma; however, VASIMR can work with a variety of gases, such as hydrogen, deuterium, nitrogen, as well as mixtures such as ammonia. We have not experimented with sulfur. We do have to be careful with the elements we use, as these could combine chemically with components near the rocket and create unfavorable conditions.

Q: Is there any way that plasma thrusters can be used to launch an object from Earth?
Thank you! Harrison Becker, Gilbert, Arizona

Chang-Díaz: Plasma rockets are better suited for in-space propulsion and not to lift off from Earth because they tend to like to work in a vacuum. The venerable chemical rocket will probably continue to get us off the planet and allow us to land nicely and efficiently, but plasma propulsion will provide the "long haul" and high speed capability to travel far and fast once in space.

Q: I am a high school student from Michigan who has always been interested in the cosmos and wanted to be an astronaut. As a high school student I am aware that the decisions that I make right now will affect me the rest of my life. I would greatly appreciate it if you could advise me on what I should focus on (what I should do) to achieve my dreams to become an astronaut.
Thank you Anonymous

Chang-Díaz: There are not only extraordinary opportunities for young people today to fly in space, but to also do extremely productive things there. Space will be a place of exploration, of business, of commerce, and lots of people will live and work there in your lifetime. So, being an astronaut takes on a much larger meaning. It needs to be connected with something else you dream about. In my case. it has always been science and exploration. I wanted to not just ride the rockets, but to also design them and build them. You need to find that special thread that guides your personal path to space. There is no set "recipe" and yours may be different than that of others. The traditional image of the astronaut as the military pilot has been expanded to include that of the scientist, the explorer, the entrepreneur. As such, you have a very bright future and a very high probability of achieving your dream if you apply yourself and work really hard. Follow your star...and be sure to enjoy the road to success, as you will spend the best years of your life getting to where you want to go.

Q: How does someone who believes in what you are trying to do contribute other than money today? With a 39-day trip to Mars, exploration is almost certain because of the manageable timeline this creates! It is so exciting, for a while I thought NASA would surely kill manned exploration beyond the moon due to the muscle loss and health problems associated with long-term space travel. This rocket is truly a game changer, in my estimation. My only engineering question is how to ensure the safety of anything that has temperatures in the millions architecturally. I'm sure the materials are exotic, but will they be safe for a 39-day burn? I'm sure it is proprietary, but nevertheless I am very intrigued. Perhaps some cross-pollination with the cold-fusion folks could net some reliable clean-power sources. If the materials science works in both genres, would there be applicable technology transfer in the future?

Science has the Answers to our problems, and inspires our dreams to go as far as we can go! Roy Koons, Davidsonville, Maryland

Chang-Díaz: I agree completely. It is amazing what science and technology can achieve for the betterment of humanity. The VASIMR engine has many new technologies without which it would not be possible to think of such propulsion system. These technologies have already begun having a positive effect in our lives on Earth. For example, plasma technology is used today to improve the efficiency of electric lamps and light sources. It is used in the manufacture of computer chips with plasma etching devices that reduce the need for toxic chemicals to process these materials. It is also used to dissociate highly toxic wastes, eliminating them and converting them into a source of clean electrical power. Superconducting magnets, needed to control and guide the plasma in the VASIMR, are the basis for MRI machines in modern hospitals and could lead to breakthroughs in high-speed rail transportation and power transmission. I could go on. I suggest you review the following document http://books.nap.edu/openbook.php?isbn=0309109434

Q: How long do you think it will take to develop the 40-day mission to Mars plasma drive? How soon do you think it will be ready for flight test? How long until you think it will be operational? Ron, Kew Gardens, New York

Chang-Díaz: The 40-day mission to Mars would require the development of a nuclear reactor to generate about 200 MW of electrical power for the engines, something similar to the reactors in use today in nuclear submarines (about 1/10 the power of a conventional nuclear power plant). Such reactors have not yet been developed for space, and they need to be if we are truly serious about humans exploring space. This may be pursued by the U.S. or any other country that has a mature nuclear power industry. We will have to see. As for the VASIMR engine itself, our company plans to develop the plasma propulsion technology in a stepwise fashion, focusing first on engines that will be used near Earth and the Moon and powered by solar electricity. Eventually, we will build more powerful engines, at tens of megawatts, suitable for a 40-day mission to Mars. These engines cannot be tested on Earth or on the International Space Station. We plan to test these engines on the surface of the Moon, using solar electric power to drive them.

Q: I was curious about the effects of the extreme temperatures of the plasma rocket. How would these very high temperatures affect the atmosphere and the ozone layer? I have heard that every rocket takeoff now causes a hole in the ozone, but I am not sure of the fact or effects. I must commend you on encouraging your children to live their dreams and be such a strong example. Our continent needs to encourage a work ethic more. Thank you, JJ Crouch JJ Crouch, Winchester, Kentucky

Chang-Díaz: Thank you for your comment. The plasma engine will not be used in the atmosphere but even if it were, the exhaust is a harmless noble gas (argon), which has no chemical reactions with the environment. However, the engine will be used exclusively in space. There, the plasma exhaust will not be much different from the plasma from the solar wind. Another important point to note is that, while the plasma is very hot, its density is very low, and so the "heat" content in the plasma jet is lower than the heat content in the exhaust of a conventional chemical rocket. Think of the difference between heat and temperature. A lit match has a high temperature but very little heat (some tough guys can put it out with their fingers). In contrast, a bathtub full of hot water has a lot of heat but the temperature is low enough to take a bath in it.

Q: I remember reading some years ago about a "Project Daedalus" that was attempting to develop a "continuous pulsed-fusion" rocket that supposedly could achieve 10% of light speed. Are you familiar with this project, and does it have anything in common with the rocket you are working on? Lyle Gentry, Wichita, Kansas

Chang-Díaz: There are several of these ideas I remember from my early university years. One of them would "scoop" hydrogen plasma from the interplanetary medium and compress it in a magnetic trap to produce fusion. I believe it was called the "fusion ramjet." In another concept, the ship would explode thermonuclear bombs in a magnetic nozzle to create a rather bumpy plasma pusher that would propel the ship. These all do have something in common with VASIMR in that they rely on plasma as the ultimate propulsion fluid and use strong magnetic fields to control it and guide it in the right direction. A variant of this was project VISTA in which I did collaborate in the early 1980s. In such a concept, a powerful laser array would trigger thermonuclear ignition in small pellets of deuterium and tritium. The explosions would result in hot and dense plasma that would also be expelled out of the ship in a magnetic nozzle to provide thrust.

Q: I watched NOVA last night and was impressed with the Plasma Rocket you invented. I would like to know if you currently reside in the State of Florida? We would like to know more about your work and share that with our readers. Our publication is a bilingual magazine that reaches both Hispanics and Non-Hispanics. Readership 150,000 print / online over 200,000 viewers a month.

Thank you
Publisher, Susan Pagan
Ahora Orlando Susan Pagan, Orlando, Florida

Chang-Díaz: I do not live in the State of Florida, though our company is thinking of establishing a presence there. Our main operation is in Houston, just a couple of miles from the NASA Johnson Space Center. We also have a research facility in northwestern Costa Rica and a small representation in Frankfurt, Germany. However, we are keen to reach all interested people and would be happy to collaborate with your magazine.

Q: When you get into space, do you have free time to play around, browse Earth, contemplate space, or is the astronaut's schedule too tight? Do you play pranks onto other astronauts during the missions (any one you can share)? Vladimir Sanchez, San Francisco, California

Chang-Díaz: We do have time for all of that and enjoy our time together as a crew. There is a lot of sharing and a strong sense of kinship that comes from being in a space mission. There are some pranks that we do play on others, but we have to be very careful with pranks in space, as they can be misconstrued. The most frequent one is to hide food, as crewmembers are sometimes highly attached to their food stuff. Nothing too serious, though.

Q: NASA is planning a manned mission to Mars around the year 2030. Do you think the VASIMR rocket will be incorporated in the mission? Zachary Neubauer, Wasilla Alaska

Chang-Díaz: We are certainly working hard to make it so. A lot of things can happen in 20 years.

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