How do rockets move in space?
If space is basically a vacuum and void of atmosphere, how do rockets alter the direction and speed of space craft? In other words, how do they "push off" against nothing?
This is a very good question. Isaac Newton worked out the solution and published it in 1687 in his Principia Mathematica. It is phrased as Newton's 3rd law. I'll include all 3 below just in case!
1st: A body will remain at rest or at motion with a uniform speed unless it is acted on my an external force.
2nd: The acceleration of a body with a force acting on it is that force divided by the mass of the body (F=ma)
3rd: Every action has an equal and opposite reaction.
So the third law basically says that if you shoot out stuff in one direction you will move in the other direction. This is how rockets work in a vacuum. They have a source of fuel which is heated up so that it expands and is pushed out of the rocket. In order to change direction in space rockets have to have little 'thrusters' on all sides (you need 6 in total to maneuver completely in 3 dimensions).
Newton's 3rd law seems contrary to our intuition because on Earth there are lots of sources of friction - providing much easier methods of propulsion, however you might have seen it in action if you have ever blown up a balloon and then let go of it before tying it up. What pushes the balloon all around the room is the air you blew into in escaping.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
- Do unmanned spacecraft like Voyager travel in straight lines?
- When unmanned spacecraft accelerate in space, what causes them to slow down?
- If Mars is only about 35-60 million miles away at close approach, why does it take 6-8 months to get there?
- How do rockets work?
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 70733 times since May 15, 2002.
Last modified: August 20, 2003 10:20:26 AM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)