Here's a look at the top 11 spaceflight stories of the year, from the last mission of NASA's venerable space shuttle program to China's first-ever docking of two spaceships in Earth orbit:
Several different companies made strides this year in their private spacecraft development. The chief contenders — firms such as Blue Origin, SpaceX, Boeing and Sierra Nevada — generally say they should be ready to fly by 2015 or 2016.
Private suborbital spaceflight also made progress this year. The space tourism company Virgin Galactic conducted more glide tests of its SpaceShipTwo vehicle, and company officials have said that in-vehicle rocket tests should start in the first half of 2012.
NEXT: Giant Mars Rover Launches
The mission will drop the car-size Curiosity rover at Mars' huge Gale Crater in August 2012, using a rocket-powered sky crane to lower the robot to the planet's surface. Curiosity's main task is to assess whether the Gale Crater area is, or ever was, capable of supporting microbial life.
NEXT: International Space Station Completed
In March, the space shuttle Discovery delivered NASA's final contribution to the assembly of the orbiting lab, a new room called the Permanent Multipurpose Module. While Russia may attach one more module in the coming years, construction from a U.S. standpoint is now 100-percent done.
NASA and its international partners began building the orbiting lab in 1998. The 431-ton space station is as big as a football field and has about as much living space as a five-bedroom house. With an estimated price tag of $100 billion, the orbital outpost is the most expensive structure ever built.
NEXT: Russia's Space Woes
On Feb. 1, for example, a Rockot launch vehicle failed to deliver an Earth-observing satellite to the proper orbit. And on Aug. 18, a Proton rocket didn't place a $300-million communications satellite in the desired orbit.
Then, on Aug. 24, the unmanned Progress 44 supply ship crashed while hauling cargo to the International Space Station, doomed by a problem with the third stage of its Soyuz rocket.
Finally, the $165-million Mars moon probe Phobos-Grunt got stuck in Earth orbit shortly after its Nov. 8 launch. The spacecraft's thrusters were supposed to fire to send it on a course for the Red Planet, but they never did so. [Photos: Russia's Failed Phobos-Grunt Mission]
NEXT: NASA's New Rocket & Spaceship
The astronauts will ride aboard a new spaceship called the Orion Multipurpose Crew Vehicle, which NASA announced in May. The spacecraft is based heavily on the old Orion capsule concept, which NASA began developing as part of now-cancelled moon exploration program
In September, NASA revealed its Space Launch System (SLS), the $10-billion giant rocket that will lift Orion off the pad.
NASA hopes the Orion-SLS combo will be launching astronauts toward deep space by 2021.
NEXT: Uncertain Future of American Spaceflight
With the space shuttle fleet retired, NASA is now completely dependent on Russian Soyuz vehicles to ferry its astronauts to and from the International Space Station, at $63 million per seat. NASA wants American private spaceflight companies to take over this taxi service soon, but that probably won't happen until 2017 at the earliest, officials have said.
NASA's budget also was trimmed, as lawmakers look to cut federal spending across the board. The agency may get just $17.4 billion in fiscal year 2012, down from $18.5 billion in 2011.
The belt-tightening could threaten some of the agency's most ambitious and expensive projects, including the $8.8-billion James Webb Space Telescope (JWST), which was nearly cancelled this year before Congress restored funding for the mission. The JWST will launch in 2018.
NEXT: The Astronaut & the Congresswoman
The tragedy reverberated beyond Arizona and the halls of Congress, reaching into low-Earth orbit. Giffords' husband, Mark Kelly, was slated to command the STS-134 mission of the space shuttle Endeavour — the second-to-last flight of the shuttle program — just a few months after the shooting. Her brother-in-law, Scott Kelly (Mark's identical twin) was also in space commanding the International Space Station at the time.
Giffords made strides in her recovery and ultimately Kelly decided to take part in the mission. When Endeavour blasted off from Florida's Kennedy Space Center on May 16, Giffords was in the crowd. [Photos of Giffords & Kelly]
Kelly retired in October with four spaceflights under his belt. Giffords continues to recuperate, and she's said she may consider a return to Congress if her condition improves enough.
NEXT: 50 Years of Human Spaceflight
Yuri Gagarin became the first person in space on April 12, 1961, completing one Earth orbit in his tiny Vostok capsule before returning safely to terra firma less than two hours later. The United States launched its first spaceflyer just weeks later, Alan Shepard, on a suborbital flight on May 5.
On May 25, 1961, President John F. Kennedy made the speech that charted NASA's direction for years to come, announcing that the U.S. would put an astronaut on the moon before the end of the decade.
NEXT: A Space First for China
The mating of the two vehicles — called Shenzhou 8 and Tiangong 1 — was designed to test key technologies that China will use to assemble a space station in orbit. The country hopes to have a 66-ton manned station up and running by 2020.
China plans to launch two more docking missions during 2012, at least one of which will be manned.
NEXT: Space Shuttle Era Ends
Atlantis' flight was the 135th space mission for the shuttle program, which began flights in 1981. The shuttle was pivotal in the construction of the International Space Station and was the first reusable crewed spaceship.
Two of its 135 missions ended in tragedy, killing a total of 14 astronauts. The shuttle Challenger exploded shortly after liftoff in 1986, while Columbia broke up during re-entry in 2003.
The three remaining space-flown orbiters are now being prepped for display in museums.
NEXT: Satellites Fall from the Sky
First came NASA's Upper Atmosphere Research Satellite, or UARS. This 6.5-ton climate satellite, which was about the size of a school bus, launched in 1991 and was decommissioned in 2005. UARS then spent six years spiraling slowly toward our planet, finally plunging into the atmosphere above the Pacific Ocean on Sept. 24.
Germany's 2.7-ton Roentgen Satellite, or ROSAT, followed closely on UARS' heels. This craft, which launched in 1990 to survey the heavens in X-rays and was shut down in 1999, fell back to Earth over the Indian Ocean on Oct. 23.
Neither uncontrolled satellite crash injured anyone. But the sky isn't done raining down huge pieces of space junk. Russia's failed Mars probe Phobos-Grunt will plummet to Earth by January 2012.