From the print edition
Costa Rican Franklin Chang, 62, was the first Latin American astronaut. His accomplishments at NASA are the stuff of legend: He is tied at seventh for most space missions, logged more than 1,600 hours in space, conducted three space walks for a total of more than 19 hours and is a member of the U.S. Astronaut Hall of Fame.
Today, he heads Ad Astra Rocket Company, based in Houston, Texas, in the United States, and with a subsidiary company in Liberia, Guanacaste.
The Tico Times caught up with Chang earlier this month to talk about Ad Astra and Chang’s own design for a plasma rocket.
Excerpts follow:
TT: Where is the space industry now?
FC: Ad Astra is one of a new crop of private space companies. Space X [a company owned by PayPal founder and multi-millionaire Elon Musk] just had a great success with its Falcon 9 booster rocket, putting its Dragon space vehicle into orbit to supply the ISS [International Space Station]. This is excellent news, because Space X, the Falcon boosters and Dragon are a complement to Ad Astra’s plasma rocket. … Our VASIMR [Variable Specific Impulse Magnetoplasma Rocket] plasma rocket is to provide thrust capability in space. …
What is the advantage of VASIMR?
Fuel efficiency. If a chemical rocket consumes fuel like a fire hose, the rate at which VASIMR consumes it would be, comparably, like a slow leak in a car tire with a nail in it. VASIMR is a completely different approach. It does not burn fuel in a combustion reaction with oxygen. VASIMR needs only fuel and no oxygen to burn it with. The fuel is heated into plasma by microwave radiation. …
What’s a plasma?
Any pure gas consists of atoms that have a defined atomic structure, consisting of electrons orbiting a nucleus of protons and neutrons. As any gas is heated, the vibration of the atoms increases. In a plasma, which requires temperatures in the millions of degrees, the atoms vibrate so much that their structure breaks down into a super-hot soup of free electrons, protons and neutrons. Because of its high temperature, a plasma gas wants to expand. …
So how does your VASIMR rocket engine use plasma?
It starts out with its fuel in the form of a highly compressed or liquid gas. The fuel is heated by microwaves, which are a very efficient way to generate heat, into a plasma. In VASIMR, the plasma temperature is 2 million degrees centigrade. This is, of course, too hot to be contained by any metal. But plasma, being a gas, can be contained within a sufficiently strong magnetic field. In VASIMR, very powerful magnets generate a virtual tube that confines the plasma. The back end of the tube is left open, and as the plasma escapes, it produces thrust against the magnetic enclosure that confines it.
How can VASIMR handle such extreme temperature differences in a small space?
At Earth’s distance from the sun, space is either extremely hot or extremely cold, depending on whether you are exposed to the sun’s rays or shielded from them. VASIMR counts on the near-absolute-zero temperatures in space, when the sun’s rays are blocked, to make superconductivity of its magnets possible. This makes magnetic fields powerful enough to contain the plasma. But your question is a good one in pointing out one of the biggest engineering challenges in VASIMR: handling extremes of hot and cold in what is really a very small unit, about the size of a tall oil drum, with a plasma core about eight inches in diameter.
Your website says that the first practical test of VASIMR will be to attach it to the ISS to try to adjust its orbit upwards, in 2015.
We’ll attach VASIMR to the ISS with scaffolding similar to the life-sized mock-up we have at Ad Astra Costa Rica’s lab. I just delivered the mock-up of the VASIMIR engine module that will be attached to it. The ISS has big solar panels, but they aren’t powerful enough to operate VASIMIR directly. What we’ll do is use the ISS panels to charge big batteries that will be incorporated into the scaffolding. In 48 hours, the batteries can be charged to accumulate enough power to fire up VASIMIR for 15 minutes of continuous thrust. This will be enough power to nudge the ISS’s orbit up a little. …
So where does VASIMR fit into the future of space?
In Earth orbit we don’t have to wait for nuclear reactors. A robotic space tug with solar panels and a battery system could operate to clean up space junk and to service and adjust the orbits of satellites.
The moon can function not just as a destination, but also as a space lab or even factory. Big plasma engine development on Earth would require vacuum chambers of a size that may not be practical. The moon, with no atmosphere and one-sixth the gravity of Earth, would be an ideal place for extended plasma rocket development. …
I see a Mars plasma spaceship powered by four 50-megawatt engines, nuclear powered. Call it a Space 747, as the engines would be about the same size. … Time to Mars could be reduced to 39 days one way.
Tell us about Ad Astra Costa Rica.
… My idea in founding Ad Astra Costa Rica is to give Ticos a chance to participate in the space industry, which is rapidly losing its nationalist, government flavor and becoming international and more private-sector driven. Keep in mind that the first men and women to go to Mars are probably 10- to 15-year-olds sitting in a classroom somewhere, right now.
