Imagine a kind of tugboat in space, a vessel that could pull and set a new course for an Earth-threatening asteroid.

Astronaut Edward T. Lu, 43, veteran of two space shuttle missions and an extended stay at the international space station, is in Hawai'i to join a panel discussion about the asteroid threat. The former University of Hawai'i postdoctoral fellow will talk about his tugboat invention, the Gravity Tractor, suiting up to be a construction worker in space, and why he loves to come back to the Aloha State.

We asked the space man five questions.

Q. How much of a threat is an asteroid compared to other disasters facing the planet?

A. An asteroid threat is both like and unlike natural disasters. Just like Hurricane Katrina and the Pakistan earthquake in 2005, and the Asian tsunami in 2004, it falls under "rare events," but as we've seen, these can be very, very bad, and we ignore them at our peril. With Katrina, money was not spent to make the levees safe. In Southeast Asia, a tsunami warning system was not in place even though it's known to be the most tsunami-prone area.

Now if an asteroid hits, it will be way, way worse, worse than World War III, dwarfing any of these events, wiping out civilization. An asteroid threat is a rare event. However, that does not mean it's not going to happen. Building a Gravity Tractor (which will use gravity to pull the asteroid into a different orbit) is being prepared. ... The cost is far less than that of spacecraft or space telescope.

Within this century, there is a 1 in 100 chance of a major explosion from space, and if that happens, the folks at UH's Institute for Astronomy (who are building the Pan-STARRS telescope to track asteroids) will be the folks who save the world. How many people ever get a chance to say that in their lifetimes?

Q. You have described yourself as a "construction worker" in space. What has been your toughest moment?

A. We can't train for everything. Surprises always happen, so the challenge is to prepare for things to go wrong. I've spent 206 days in space, and every single one of those days something had gone wrong. We are trained to test things; in fact it would be shocking if something did not go wrong.

Q. What has been the most memorable moment in space?

A. Many, many amazing moments have been special, which I consider a privilege to have witnessed: launching the space shuttle; returning through the Earth's atmosphere; completing a space walk; flying on a Russian spacecraft. All have been breathtaking. (Lu also spent six months in 2003 overseeing science operations at the international space station.)

Q. What is the challenge for the U.S. space program in the next 20 years?

A. The transition from lower orbit missions (such as those to ISS) to exploratory missions ... the moon, asteroids and Mars. Will we get to Mars in my lifetime? Yes, (scientifically) I think we can do it, but it also takes political will, and I can't predict that.

Q. And when you're not working?

A. I love coming back to Hawai'i; I get to see old friends. We take longboards out at Waikiki to surf, sit and eat local food on the beach. I have a buddy who has a small plane and so we'll fly together. I'll check the wrestling schedule at Punahou ... (Lu coached the school wrestling team between 1992 and 1994) and of course, make a visit to Andy's sandwich shop in Manoa, a favorite place of mine to eat.

(In Houston,) there's my plane, my RV-4 experimental plane, home-built — not by me — but completely modified by me. It's a two-seater, and I like to take her up and fly upside down. When my wife and I began dating, I invited her to come flying with me. My plane was housed in a hangar shielded by a much bigger plane ... of course, she thought the big plane was the one. She ended up helping push mine out of the hangar, but it all worked out in the end.

Reach Chris Oliver at coliver@honoluluadvertiser.com.