Final answer:
Space exploration can be conducted using vehicles like the Space Shuttle and interplanetary spacecraft, with detailed processes for orbiting and landing on planets, as well as returning to Earth. The Space Shuttle was a partially reusable launch system, but other methods such as launching satellites from airplanes can offer some advantages. Interplanetary spacecraft follow orbits around the Sun, using minor thruster adjustments, and probes use heat shields and parachutes for atmospheric entry.
The correct option is 2.
Step-by-step explanation:
The discussion revolves around different space exploration methods and vehicles, such as the Space Shuttle, interplanetary spacecraft, and the process of a probe mission, which involves orbiting a planet and potentially returning to Earth. The Space Shuttle was designed as a partially reusable spacecraft, costing as much as expendable, unmanned rockets due to its need for a human crew.
The benefits of launching satellites from airplanes include a higher initial velocity and reduced atmospheric resistance. Interplanetary spacecraft require escape velocity to leave Earth's orbit and usually coast to their destination with minor adjustments from on-board thrusters.
For a spacecraft to orbit a planet, it must decelerate upon approach and enter into an elliptical orbit. Additional rocket thrust is needed for the spacecraft to descend from orbit and land, and a return journey necessitates reserve propulsive power to reverse the entire process.
In probe missions, atmospheric friction and heat shields play a crucial role in safely descending into a planet's atmosphere, with parachute deployment for a gentle landing and instrumented data relay back to Earth.
The correct option is 2.