Answer:
1. Following the recoil principle, rockets use combustion (a controlled explosion) to work against earth's gravitational attraction.
2. A force is a push or a pull that acts upon an object as a results of its interaction with another object. ... These two forces are called action and reaction forces and are the subject of Newton's third law of motion. Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction.
(via physicsclassroom.com)
3. The combustion throws out material with very high momentum and is, physically speaking, the action. In reaction to that that, the rocket moves away from it (upward when in starts and has the action underneath it)
4. To show the world that commercial manned space missions are safely possible. Some may also like the fact that the US can now do, or rather order, manned flights into space without the help of the russian space agency (Roskosmos).
5. Robert Behnken and Douglas Hurley
6. The international space station (ISS)
7. Yes, Stage 1 of the rocket landed on the drone ship. The crew opened the hatch to enter the space station after 21 hours and 39 minutes after the launch from Cape Canaveral.
8. To have private contractors such as SpaceX actively in the field, there are now more interest groups that participate in space travel. And they can interact with other companies as well.
Also, due to Musks dream and efforts of SpaceX, space travel seems to get a lot cheaper.
That might indeed open the way back to the moon and further to the Mars for human space flight.
Governments such as the US planned on such things for decades, but changed plans ever since, and routinely changed leadership and the opinion on what's important.
Now Spaceflights can become less politically motivated and more commercially. That seems to be a more stable way over long periods of time.
(wrote most of it for you myself, even tough I'm not a native English speaker. would really appreciate the brainliest if you appreciate the work)