Does a rocket need the atmosphere to 'push off of'?  Why or why not?
602071
No atmosphere is needed. The exhaust and rocket push against each other. Think of two weights held together with a clamp but with a spring compressed between them. When you release the clamp the spring pushed the weights apart. Each weight pushes off of the other weight and they both move away from their common starting point. This is what the rocket and it's exhaust do, push each other apart.
594787
The speed depends on what you want to accomplish.  If a rocket pushes a craft slower than 5 miles per second (mps), the craft will fall back to Earth.  If the rocket gets the craft to 5 mps, the craft can orbit Earth in more or less a circle.  If a rocket gets a craft to 7 mps or more, the craft will leave Earth all together.
609452
No, because you are moving with the Earth while you're in it's atmosphere.
268556
no....\n\nit wont need fuel..... it is moving in the space only through the gravitional force...
345992
Yes. The gravitational force is not that weak.\nNote also that the pressure difference is not sudden at all, higher and higher into the atmosphere, the pressure becomes lower as the weight of the particles above becomes less. As the pressure gets lower, the effect of gravity is also lower.\nWe do still lose some air particles into space, but not a significant quantity.
488798
Hi:\n\nNASA mostly use hydrogen and oxygen or tri-nictro-oxide in the liquid stages of their rockets and ammonium Nitric or some other solid state fuel that similar to gun cotton for the solid rocket booster. However in the early day of rocketry; they use any liquid fuel that would combined with liquid oxygen, Such gasoline,100 proof grain alcohol,Kerosene, fuel oil. and gunpowder or gun cotton for solid rockets Today however they mostly use hydrogen and oxygen for the liquid fuel rockets. What type of fuel they put into their rocket depend on how much weight their payload is; and how high they want it to go, and if they are visiting the planets in our solar system this as to be accounted for too.\n\nBack in the 1950,s and 1960's NASA had developed a Nuclear rocket engine under a project name: "Project Pluto" where liquid hydrogen was heated by a nuclear reactor to produce  a rocket thrust to propel a spacecraft in space. It fell out favor with the public due to radiation issues. There is a new type of rocket that uses ion propulsion where a gas such a hydrogen or Xenon gas is ionized and run ed through a series of electrically charge grids and are accelerated to very velocity as they exit the spacecraft And then there is:  The Antimatter and Matter rocket engine this where Matter and Antimatter is allow to mix in certain ratio in a rocket reactor vessel and focused by magnetic field to generate a lot of thrust
284291
If you could shoot a rocket into outer space with enough force to cause it to leave our solar system, perhaps it would exhibit "perpetual motion" and travel forever.  But that would be deceptive.  It would continue to move unchanged only because it meets little matter or force to overcome.  On earth, to set something into motion you must add to its kinetic energy which equals one half times its mass times its velocity squared.  It doesn't matter how you add the energy (or that it gains more say by falling) we are interested only in the energy you added to create perpetual motion.  It could revolve say suspended above powerful frictionless magnets within the vacuum inside an evacuated bell jar for a very long time.  However, there is no perfect vacuum on earth and there would still be atoms or molecules that would collide with and slow down the rotating item whether that took hours or days or years.  Perpetual motion must last forever(!) without you or Nature adding to its original kinetic energy.  If you hold your hand outside a moving car you will feel wind on your hand and some reasoon it could be harnessed (like a sail boat) to propel the car, neglecting the fact that the wind exists solely because the car is burning fuel.  Out of gas = out of wind.\n\nI would encourage you to pursue your theory for the lessons involved but carefully account for all the energy.  Consult with any engineer (especially mechanical at first) or any physics teacher (professor) and remember that your theory could involve a better use of energy if not perpetual motion.  You must patent most devices within a year of public disclosure (which would not include a witness to your theory or device).  Good luck.
817981
As others have said, it's all about speed. \n\nIt's a minor point really, but it's a common misconception that it is the friction with the air that causes objects hitting the Earth's atmosphere at high speed to heat up. Actually it's not friction. The heating up is caused by the fact that the air in front of the object cannot get out of the way fast enough, so it's gets compressed in front of the object. As the air gets compressed the pressure rises and as the pressure rises so does the temperature. This is what causes the burning up effect.\n\nWhen a space craft is blasting off into orbit, as its speed rises it's also gaining altitude. At higher altitudes the atmosphere is less dense, so this compression of the air in front of the space craft never becomes a problem.\n\nIf a space craft used its rockets to slow its decent back to Earth then it wouldn't have any problems with burning up on re-entry. The reason they don't do this is because of the weight of the fuel that would be needed to do it. With current technology, no spacecraft could carry that amount of fuel and still be able to get into orbit.
78972
Very large rockets produce enough thrust to overcome the Earth's gravity. Eventually, they go so high up, that even with the rockets turned off, the Earth's gravity no longer pulls it back down.  Everytime you jump up, you're essentially 'leaving' the Earth's gravity, so think of it as 'jumping' with so much force that you keep going right into space.  Sorry for the watered-down explanation. You could probably get a more scientific responce by typing 'rocket propulsion' into a search engine.
1035230
First of all, it depends on what you need the thruster for. Chemical rockets (solid, liquid, and hybrid) are the only ones with strong enough thrust to get off the Earth, but once you're in orbit even a low continuous thrust will get you where you want to go, if you have the time.\n\nChemical rockets combine fuel and oxidizer to create thrust. Liquid and solid fueled rockets are just what they sound like; hybrids use a solid fuel but a liquid oxidizer to to start and stop the burn. This helps to deal with one of the biggest problems with solid fuel rockets - once they're lit, they can't be shut off. A hybrid can be throttled off just by stopping the flow of oxidizer.\n\nHall effect and ion thrusters are a bit different. They use a fuel (typically a light gas, but there's a particular type that uses solid Teflon) that is ionized and then passed through a magnetic field to accelerate it to very high speeds. The drawback is that the acceleration is very low, so it can't be used to launch off the Earth. The plus is that you don't really need the high thrust of a chemical rocket in space - it just takes you longer to get anywhere. There was a British spacecraft that went from Earth orbit to the Moon using only ion thrusters; it took eighteen months!
580135
Absolutely,it is okay!The cylinders are designed to hold thousands of pounds of pressure,regardless of ambient temperature.Also if you look close on the cylinder neck at the shut off valve,you will see a blow off port ,it is permanently there for over pressure blow-off but the summer heat makes little difference.WHAT TO WATCH FOR-have no oil near the tank ,when mixed oxygen there will be an explosion!Do not drop tank.the end could rupture and it will take off like a missile.Also no smoking ,I am not sure why but I have always heard that .
661575
The tighter the foil around the match heads then the further the rocket will go...it's all down to the restriction of oxygen to the initial explosion....the less oxygen then the more power to the match.
462198
it depends on whattype of rocket. it also depends on what fuel that you use. and how high you want it to fly. whether you usea  solid or liquid propellent. how heavy your rocket and payload is. be more specific with this.
524989
a) the ground is counteracting the force of gravity, so the rocket is at rest, no other outside forc is acting upon it.\nb) becuase force is applied to the rocket.\nc) becuase of the force of gravity (and friction from air)\nd) if there were no gravity or friction from air
33547
Same way they do anywhere....\n\nJets take in air and spit it back out. A jet wouldn't work in space.\n\nRockets carry their fule with them, and so don't need to take anything in.\n\nThe mass and energy pushing away from the rocket will push just as hard in space as on Earth, and will do all the better since there is less gravity to worry about.
538200
It doesn't really need to move, since it's a shell that covers the whole Earth.  It's a bit thinner in some places, like the poles (especially the south pole) but it generally protects every spot on Earth at the same time.  Imagine a ball within a ball...  The innner ball is the Earth, and the outer ball is the ozone layer.
39571
As you know, Newton's Third Law of Motion states that for every action there is always an equal and opposite reaction. This is applicable only to an action originating from a mass. When you consider a rocket, gas is ejected out from the thrust nozzle with great acceleration. This is achieved when a force is applied on the gas.\nNow, when a force is applied on the gas by the rocket to thrust it out, the gas exerts an equal and opposite force on the rocket, thereby resulting in acceleration of the rocket in the direction of the net resultant force. Thus there is no need for any atmosphere or body which exerts a reaction force other than the gas ejected!! So there you are !!!