Chewin in the Chung

I am tutoring Alishan Jim's son Tim in pre-algebra. The good news is that in spite of certain glaring lack of mental abilities on my part:

to beat Nick in chess,
to ascertain the location of the leak in the downstairs toilet,
to write coherently,

my Pre-Algebra skills are in good working order. And Tim himself is pretty bright. His problems in the class stem from the classic bad habits of doing too much of the problem solving in his head, and not writing down enough of the steps on paper.

We usually have about 15 minutes at the end of class, where we chat about various things. Halo and fighter jets are popular subjects, but since I don't know anything about fighter jets, he does all the talking and I just ask questions. I can sort of hold my own in the Halo conversation. Sort of.

The thing is, Tim asks an awful lot of questions. I answer them the best I can, but sometimes I have to say: "Let me get back to you on that one." And then I Google like crazy the next day. Here are some examples:

Tim: Why can't we get a spaceship to move at the speed of light if we add enough rocket boosters?
Me: Because the mass of the spaceship increases as your velocity approaches the speed of light.
Tim: So just add more boosters!
Me: Um.. You can't really add enough boosters.
Tim: Why not?

Tim: What is the difference between nuclear radiation and other radiation?
Me: Er...

Tim: With the technology we have now, it would take humans 200,000 years to reach the nearest star.
Me: It wouldn't take that long.
Tim: Really? How long would it take?

Tim: Why don't we use big rail guns to launch spaceships from the earth?

So, in an attempt to give a decent answer to the nearest star question, I set up an Excel file where I was going to show the distance of the nearest star in light years, then convert the light years to km, then divide by the speed in km of the fastest space object mankind has made. Then explain the time required for accelerating and deccelerating, and how that affects the final answer.

So, Google 'closest star'. It is Proxima Centauri, 4.2 light years. I thought it was Alpha Centauri? No, Alpha Centauri is the closest star system. Ok, got it. Google speed of light (I only know it in miles). Very cool, Google guys. 299792458 m/s. Right. Put that in Excel and convert to kilometers. No, wait a second. Google 'kilometers in light year', Oh sweet. Google 'fastest man made object'. Uh oh.
First result: Satellites and probes. 17.4 km/sec
Second result: Helios. 150,000 miles per hour (67 km/sec)
Third result: NASA's Voyager 1. 38,518 miles/hr (17.21 km/sec)

Add a tangential search that yielded Ion drives, and I'm not at all sure how to answer the question.