11.   These include more fuel-efficient, less polluting gas-burning car and aircraft engines as well as superior fire prevention equipment for future human spacecraft.

12.   Both technologies could make future spacecraft less reliant on orders from Earth.

13.   The two astronauts were conducting experiments on materials for building future spacecraft.

a. + spacecraft >>共 167
the 11.18%
russian 8.28%
unmanned 4.97%
alien 4.14%
orbiting 3.93%
new 3.52%
first 3.11%
manned 2.90%
future 2.69%
robotic 2.28%
future + n. >>共 1250
state 3.22%
generation 2.31%
growth 1.75%
earnings 1.53%
plan 1.51%
government 1.40%
capital 1.36%
attack 1.06%
president 0.97%
development 0.96%
spacecraft 0.07%
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