Rex Walheim is an astronaut. He's gone to space three times, including on the last flight of the space shuttle. He has spent an accumulated 36 hours outside the ISS on spacewalks. He has tweeted from 240 miles above sea level.

Walheim reached those heights the old-fashioned way: Air Force test pilot school (plus a masters in industrial engineering). But his isn't the only path to the stars. Today, NASA has Walheim chatting with lots of different news outlets about the astronaut recruitment process and what it takes, in the modern world, to have the right stuff. I got to talk to him this morning. Walheim was kind enough to answer five questions, submitted by BoingBoing readers, about astronaut training, the astronaut selection process, and how the Earth-bound can recreate some of the astronaut experience in our daily lives.

Maggie Koerth-Baker: This question comes from reader kansas: When you're going through the selection process, hoping beyond hope to be chosen to train as an astronaut, would you admit to being afraid of anything, or would than seem not very astronaut-like? Is there a place in the training for people to admit to having fear?

Rex Walheim: I think it would depend on how you talk about something like that. If you say, "I'm scared to death," you might not make it. But you can say, "I'm concerned about my safety." Frankly, if you're not concerned about sitting on 10 stories of high explosives, you're not thinking hard enough. The funny thing is, after 5 years of training, it actually doesn't cross your mind too much.

I remember my first flight. You're so excited. You've been wondering, is it ever going to really happen. You never know whether launch day will actually be launch day. I remember that I felt the engine sart and the rocket boosters start, and I thought, "I really get to do this today! Nobody can stop me now!" That was an incredible adrenaline rush. On simulations we have things breaking and going wrong to test us. But on the real day nothing went wrong. I had the chance to look around and think, "Oh, this is kind of dangerous." But 8.5 minutes later we were at 17,000 mph and in orbit. You're so trained to do the job, you just kind of put the danger aside. The harder time is leading up to the mission, when you're with your family and thinking about what could happen several weeks and months ahead.

MKB: Reader penguinchris wants to know: What can we average folk do (within Earth's atmosphere and outside NASA training centers) that most closely simulates the various sensations of space flight? I mean, most of us have experience with g-forces, including brief moments of zero-g/freefall on roller coasters. But what I'm really wondering is if there's something here on the ground that we regularly experience that reminds you, an astronaut, of space flight. Not necessarily just the physical sensations, but perhaps mental state of mind.

RW: The first thing that comes to mind is actually finals week in college. On the space shuttle program, we're sprinting the whole time. We have so much to do. I was on the final mission and there were only 4 people to get everything done in 13 days. We're moving so fast and have so much do concentrate on. The mental frame of mind is that you're doing this hugely important job and doing it quickly.

On long duration stays, you get time to enjoy it a bit more, free time on weekends and whatnot. Then it's like being in the mountains, where the views are spectacular. It's incredible, being able to see 1000 miles in any direction. Incredible. But it's that, plus all the support you're getting from Earth. You have an internet phone to call people anywhere. It's great to be able to call somebody on their cell. They might be on a ski lift in Colorado and you can talk to them from ISS. And you can talk to celebrities and people you wouldn't normally get to interact with and they're really happy to hear from you.

MKB: Here's what Scratcheee asked: Who is the least stereotypically astronaut-like astronaut you know?

RW: There's really a lot of variety of people. But one of the best is Don Pettit. [Pettit was a chemical engineer at Los Alamos before entering astronaut training — MKB] He's launching in just a few days, actually. He's the professor, and the nicest guy you'd want to meet. He knows all sorts of things, on lots of different subjects. And he does Saturday Science on board the space station with things we just have on hand, like what happens to Alka-Selzter in water in zero-g. He's just got an incredible curiosity. He's not the steely eyed test pilot, but he's so much fun to have around.

MKB: Here's a question from spocko: We all loved the Apollo 13 story about creating a C02 detox filter using duct tape and notebook binders. In your training do they ever run "MacGyver drills" where you need to fix things with improvised parts?

RW: I think that is part of space station training, because on long duration stays, over 6 months, you do have to fix things. One of the first things I learned is that duct tape holds the space program together. So you have this maintenance training. They do get into that. You have to fix a lot of stuff. Mike Fossum was telling us recently that that's the great thing about being in the space program: One day you're walking in space, and the next day you're fixing a toilet.

MKB: It looks like we've got time for one final question, so let's try this one from ganman: What reason for candidates getting the axe surprised you the most (or was the most surprisingly frequent)?

RW: Unfortunately, it's the medical stuff. You get people who look perfectly healthy, and tests during training find things they didn't even know about. It's frustrating sometimes, because you'll say, "That person was perfect!" but there's this medical issue that counts them out.

• • • •

•NASA is now taking applications for its astronaut selection program.

• Kansas, penguinchris, Scratcheee, spocko, ganman, and (although we didn't have time for your question) Titus: Please contact me at You've all won an awesome BoingBoing sticker and Jackhammer Jill pin. Thanks to you six, and all the readers, for submitting such great questions. It was a hard choice to narrow them down.

Image: Rex Walheim at work on a spacewalk during STS-122 in February 2008. NASA photograph.