Top ten spacecraft

9. Vanguard 1
Not content with littering the planet, humans are rapidly filling up the skies. We need a plan to clear our junk up, and Vanguard 1 is the perfect reminder that the problem isn't just going to go away.

At 50 years old this year, Vanguard isn't the most remarkable piece of technology, but it is the oldest. Vanguard was the fourth artificial satellite to be placed in orbit and is now one of an estimated 12,000 pieces of non-operational space-junk that are larger than an orange. It's also deeply worrying -- if you spend any time in space at all -- that there are a further 100,000 objects in space that we have no way of tracking.

Space junk is a problem that's worsening too, with more and more things being launched into space, and then eventually abandoned. The Chinese have also conducted experiments to destroy satellites in orbit, and in so doing have created space debris on a massive scale.

Vanguard also holds the much more prestigious honour of being the first satellite to use solar power. It managed to send data for six years after its battery died.

Photo credit: NASA