Theory:Doctor Who television discontinuity and plot holes/Delta and the Bannermen


 * By 1959, the idea of launching satellites shouldn't be a big secret anymore.


 * Perhaps this particular satellite was a spy satellite? The DVD production notes suggest that, perhaps in the Whoniverse the US launched its first satellite later than in the real world. However ...

Maybe that is why the agents were assigned to retrieve it
 * Why does the US satellite look exactly like the Russian satellite Sputnik?
 * Why does eating alien food turn billy into a Chimeron? Shouldn't it poison him?