With the help of Kerbal Space Program's new First Contract update. The update massively expands the game's career mode by introducing contracts -- basically missions. Now, instead of launching your custom-built ships into orbit just for fun, you can actually make money by completing specific objectives, and use it to expand your space agency's arsenal of spaceship parts.
There are several types of contracts:
- Testing Parts: Perform a test of a part in a specific location, situation and within given flight parameters (when applicable).
- Collecting Science: Return or transmit any scientific data from a specific location.
- Kerbal Rescues: Rescue a Kerbal who is stuck in orbit.
- Planting the Flag: Plant the Agency's flag on the surface of a given location.
- Exploring the Solar System: Complete several exploration goals for an unreached location.
Which contracts you get depends on your reputation, which rises or falls based on how successful your contracts are: whether you safely bring back or lose Kerbals during a mission, complete your contracts on time, and so on.
You can read more about the update here (and in the official FAQ here). And, in case all this makes you want to come back to the game, here's a new animation-slash-trailer to get you in the proper mood:
First Contract Now Available [KSP Forums]