Final answer:
If a spacecraft doesn't reach escape velocity, it may fall back to Earth or achieve an incorrect orbit. Precise calculations and sufficient thrust are crucial for successful space navigation, as evidenced by the failure of the Mars Climate Orbiter due to unit conversion errors.
Step-by-step explanation:
If a spacecraft launched from Earth doesn't have sufficient velocity, it will be unable to achieve the required escape velocity to break free from the planet's gravitational pull. To escape Earth, a spacecraft must reach a speed of about 11 kilometers per second (25,000 miles per hour). Without this speed, the spacecraft will fall back to Earth or, at best, achieve a lower orbit than intended, which might not be suitable for the planned mission. In interplanetary travel, spacecraft must follow precise trajectories and sometimes require additional rocket thrust to correct their paths or slow down to enter orbit around another celestial body. An underpowered spacecraft may not only fail to reach its target but might also risk collision or loss, similar to what happened with the Mars Climate Orbiter due to incorrect unit conversion.
It is critical for spacecraft to have the correct calculations and thrust calibrated in the proper units to navigate the vast distances in space successfully. As the Mars Climate Orbiter incident illustrates, a navigational error can result in catastrophic failure, underscoring the importance of precision in space travel.