Other source:

The battle with Vegeta is over, at the cost of Yamcha, Chiaotzu, Tien, Piccolo, and Kami. With the Dragon Balls gone, the others can’t be wished back, but Krillin has an idea. He overheard Vegeta saying that it was the Nameks who created the Dragon Balls, so they decide to go to the planet Namek. The only problem is that it will take over 4000 years to reach Namek. They decide to use Nappa’s spaceship, because Saiyan spaceships travel much faster.