Complex sentence: This was the first time that the Space Shuttle was sending a space station's components, but in 2011, Space Shuttle Endeavor was sent a Alpha Magnetic Spectrometer and ELC-3 to the ISS during STS-134.
Split into simpler sentences: This was the first time that the Space Shuttle was sending a space station's components. But in 2011, Space Shuttle Endeavor was sent a Alpha Magnetic Spectrometer and ELC-3 to the ISS during STS-134.