Weather permitting, the space shuttle Discovery will take off from the Kennedy Space Center on Wednesday at 9:20 p.m. The 125th space shuttle flight will take its seven-member crew to the International Space Station for a 14-day mission. Before these brave astronauts take off, we thought we’d answer a few pressing questions about both this mission and the space shuttle program in general.

What is this mission doing in space?

This mission, STS-119, is another trip to the International Space Station for upgrades. The station wants to expand its crew from three people to six this year, but doubling the population of the revolving lab will suck down added electricity. When the Discovery takes off, it will be carrying a pair of solar arrays that will help buttress the station’s power needs.

Getting this cargo up to the space station doesn’t sound like a huge task, but the arrays themselves are pretty gigantic. Each array is 240 feet long when they’re totally assembled. When they’re up and running, NASA says the arrays will generate up to 120 kilowatts of electricity, enough to meet the energy needs of 40 homes.

Is that the mission’s only objective?

Transporting the arrays is a pretty tall order in itself. But the space station’s crew might be even more excited to see the shuttle because it will also be carrying a Urine Processing Assembly. This device has more than just a catchy name. It converts astronauts’ urine into potable water, a scarce commodity in space. Unfortunately, the system that’s currently on the International Space Station doesn’t work, so Discovery will have a replacement in her hold.

Also, Discovery will do a little experiment when it hits Mach 15 on reentry. One heat shield underneath one of the shuttle’s wings has a quarter-inch raised bump on it. By taking readings on airflows around this tiny bump, NASA’s engineers will be able to gain more insight on the turbulence that surrounds a craft on reentry.

Are all shuttle missions this specific?

According to NASA, the average cost for a mission is $450 million. Given this high sticker price, the astronauts need to have a pretty clear goal before they strap in for takeoff. The first shuttle mission, STS-1 in 1981 (crew pictured), had much less defined aims, though. It seems quaint by NASA’s modern hyper-focused current mindset, but the objectives for that mission were simply to make a successful ascent into orbit, make sure everything on the shuttle worked, and come back safely.

What’s the mileage on Discovery?

Discovery has been going into space for almost 25 years; its first flight lifted off on August 30, 1984, after five years of construction. It started spinning through its odometer pretty quickly, too. It’s not uncommon for a shuttle mission to rack up over 5 million miles of travel, so during the course of its 35 missions, Discovery has put about 128 million miles under its belt. In short, if you buy a shuttle, an extended warranty might not be a rip-off.

Ha! I can’t buy a shuttle…can I?

If you’ve got enough cash, you could build your own. Hope you’ve got deep pockets, though; NASA spent $1.7 billion constructing Endeavour from 1987 to 1992. If you’re not totally bent on getting that new-shuttle smell in your ride, you might be in luck.

NASA is retiring the space shuttle program in 2010 and developing a new “crew exploration vehicle” as a replacement.

Once the shuttles aren’t going up into space anymore, they’re sort of gigantic, expensive paperweights for NASA. The organization is taking applications from museums, schools, and other educational institutions to display one of the retired shuttles.

NASA gave the Smithsonian’s National Air and Space Museum dibs on Discovery, but Endeavour and Atlantis are still up for grabs. Even if you write a really cogent explanation of why your school needs its own retired shuttle, you’ll still need some cash. According to NASA, exhibitors will get a bill in the neighborhood of $42 million just for getting the shuttle to their institution. This fee will include decontamination, transport of the 85-ton shuttle, and $8 million to get it ready for display.

What’s the fuel bill look like?

It would make even the most hardened SUV owner weep. Once in orbit 190 miles above sea level, the shuttle must go at least 17,500 miles an hour to stay there. NASA says that the shuttle and its tank carry 835,958 gallons of hydrogen, oxygen, and other liquid propellants. The solid rocket boosters that help push the shuttle up each have over a million pounds of solid fuel in them.

Are there any average guys on this shuttle?

This mission isn’t just staffed by cream-of-the-crop pilots and brilliant research scientists. Mission Specialists Joseph Acaba and Richard Arnold became space travelers through NASA’s Educator Astronaut Program. The two men, both of whom are former middle and high school teachers, have all the duties of normal astronauts, but they also help with NASA’s educational outreach programs. Acaba and Arnold will get to make two spacewalks apiece to make repairs and additions to the International Space Station.

Where does the shuttle land?

Normally, shuttle voyages are round trips; the shuttle takes off from the Kennedy Space Center in Florida and lands back there at the end of its mission (a Kennedy landing is pictured above). Sometimes, however, the conditions for a landing in Florida aren’t optimal, so NASA has a whole slew of backup landing spots with nice long runways picked out. Edwards Air Force Base near Los Angeles is the prime backup, and the shuttle Endeavour just landed there in December.

Once the shuttle lands at one of these backup sites, there’s a problem. The shuttle isn’t a normal plane that can just take off again to get back to the Kennedy Space Center, and NASA can’t exactly hitch it to the back of a tow truck. These guys are smart, though. NASA has specially modified Boeing 747s known as Shuttle Carrier Aircrafts. To get a shuttle back home to Florida, NASA picks it up off the ground and sticks it on top of the Shuttle Carrier Aircraft, which gives the shuttle a piggyback ride home. The cost of moving the shuttle is a bit more than a first class ticket from LA to Orlando; in the aforementioned shuttle-giveaway program, the bill for simply moving the shuttle is an estimated $5.8 million.