testing, testing?

Question

Engineers at NASA build models of spacecrafts for simulations.

give at least three reasons for building models before an actual space flight

Answer 1

1) Building models help identify problems that will be encountered when building the actual craft.
2) Models can be tested & destroyed far cheaper than actual.
3) Models need to be built for wind tunnel testing to test the reaction of the craft while it's moving through the Earth's atmosphere.

Answer 2

part construction-make sure they fit together properly.

defects-things that don't work properly.

improvements-robotic arms, cameras, computer chips