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- Mothership broken down 3 answers
The movie shows the majority of the aliens as unintelligent and seemingly incapable of operating, let alone inventing, a space ship. However, the exosuit/mech was clearly created in their image, weapons are hardcoded to work only with their DNA, and Christopher seems to know exactly how to operate the mother-ship and where their planet is located.
Why then were conditions inside the ship so terrible and why did it stop to hover above Earth?
All that seemed to be required to start the ship again was the black fluid that Christopher, his friend, and his son collect. They obtain this from various pieces of alien technology scattered throughout the slums. Of course this technology must have been located inside the ship, so why didn't they simply collect it during the few weeks between the ship's arrival and the hull being cut open by humans? It took them years to collect this small amount, but I imagine it would have been much easier to locate on the ship, and the process would have been much quicker with the other prawns' assistance.
If help was what they hoped to gain on Earth, why didn't they send an emissary instead of just letting the ship hover over Johannesburg? Clearly, it would have been possible since we see the smaller ship detach from the mother-ship.