Question

The space missions that went to the moon required an extremely powerful rocket engine. This rocket engine is always separated (blasted away) from the astronaut's capsule as soon as they reach space, leaving them without the power of a large engine. Discuss why they need an engine to take off, but once they are in space they can go all the way from the Earth to the Moon without an engine. Use the Newton's Laws of Motion to guide your thinking about what is happening.

Why do space missions to the moon require an engine to take off, but once they are in space, they can go all the way from the Earth to the Moon without an engine?

A) The rocket engine is only needed to overcome Earth's gravity and achieve escape velocity.
B) Once in space, the spacecraft continues to move due to its inertia.
C) The absence of air resistance in space allows the spacecraft to travel without the need for an engine.
D) The gravitational pull of the Moon helps propel the spacecraft towards its destination.

Answer 1

Space missions require engines for takeoff to overcome Earth's gravity, but once in space, they can coast to the Moon due to inertia and the absence of air resistance. Smaller thrusters are used for orbit insertion and landing maneuvers. Newton's Laws of Motion explain both the initial launch and subsequent maneuvers in space.

Step-by-step explanation:

Space missions to the Moon like those carried out by NASA's Saturn V rocket need an engine to take off primarily to overcome Earth's gravity and achieve escape velocity. The immense amount of fuel (about 2.3 million kilograms for Saturn V's first stage) allows the rocket to accelerate enough until it reaches space. According to Newton's Laws of Motion, particularly in relation to the third law, for every action, there is an equal and opposite reaction. The engines propel the spacecraft off the ground by forcefully ejecting exhaust gas in one direction and pushing the rocket in the opposite direction. This is necessary to counteract the force of gravity pulling the rocket toward the Earth.

Once the rocket is in space, the need for a large engine diminishes because the absence of air resistance and a significant gravitational pull allows the spacecraft to coast through the vacuum of space. Based on Newton's first law of motion, an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. In space, the unbalanced force of Earth's gravity is no longer a major factor, so the spacecraft can maintain its velocity without the need for continuous propulsion to travel from Earth to the Moon.

To enter into lunar orbit or to land on the Moon, smaller thrusters are used to alter the spacecraft's trajectory or slow it down. These manoeuvres require much less energy than the initial takeoff and are vital for mission success. When planning for a return trip to Earth, sufficient propulsive power is required to leave the Moon's gravity, correct the spacecraft's trajectory, and safely re-enter Earth's atmosphere. The propulsion principles governing these phases of space travel also relate back to Newton's Laws of Motion, ensuring the spacecraft's movements are controlled and directed as necessary.