Rockets Definition and 136 Threads

A rocket (from Italian: rocchetto, lit. 'bobbin/spool') is a projectile that spacecraft, aircraft or other vehicles use to obtain thrust from a rocket engine. Rocket engine exhaust is formed entirely from propellant carried within the rocket. Rocket engines work by action and reaction and push rockets forward simply by expelling their exhaust in the opposite direction at high speed, and can therefore work in the vacuum of space.
In fact, rockets work more efficiently in space than in an atmosphere. Multistage rockets are capable of attaining escape velocity from Earth and therefore can achieve unlimited maximum altitude. Compared with airbreathing engines, rockets are lightweight and powerful and capable of generating large accelerations. To control their flight, rockets rely on momentum, airfoils, auxiliary reaction engines, gimballed thrust, momentum wheels, deflection of the exhaust stream, propellant flow, spin, or gravity.
Rockets for military and recreational uses date back to at least 13th-century China. Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology for the Space Age, including setting foot on the Earth's moon. Rockets are now used for fireworks, weaponry, ejection seats, launch vehicles for artificial satellites, human spaceflight, and space exploration.
Chemical rockets are the most common type of high power rocket, typically creating a high speed exhaust by the combustion of fuel with an oxidizer. The stored propellant can be a simple pressurized gas or a single liquid fuel that disassociates in the presence of a catalyst (monopropellant), two liquids that spontaneously react on contact (hypergolic propellants), two liquids that must be ignited to react (like kerosene (RP1) and liquid oxygen, used in most liquid-propellant rockets), a solid combination of fuel with oxidizer (solid fuel), or solid fuel with liquid or gaseous oxidizer (hybrid propellant system). Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks.

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  1. A

    Particle beams in space rockets

    I'm currently working on a new paper on how to increase the efficiency of space rockets (both in performance speed and power). Getting the idea from a simple CRT (Cathode ray tube) and how the beams make an object move in the tube; I came up with this idea to use the same thing in a typical...
  2. E

    Why do electric rockets need to be in a vaccum?

    Yeah, why do they need to place plasma rockets in a vacuum? Temperatures? Air resistance from the particles? Is there any thrust at all in an atmosphere?
  3. F

    Is the Race for Bigger, Stronger, and Faster Rockets Just Beginning?

    Just sayin... The next one must be bigger, stronger, faster.
  4. C

    Answer: Rockets Colliding: Time Dilation from Earth to A's Frame

    A person on Earth observes two rockets moving directly toward each other and colliding. At time t=0 in the Earth frame observer determines that rocket A, traveling to the right at v_a=0.8c is at point a and rocket B traveling to the left at v_b=0.6c is at point b. They are separated by a...
  5. A

    Designing Model Rockets for Maximum Altitude

    Hello, This summer I would be interested in designing my own model rocket. I do not have a lot of aerospace/aerodynamics (read the NASA (http://www.grc.nasa.gov/WWW/k-12/airplane/)) knowledge but I do have a good grasp of math and physics. I would like to use a A or B model rocket engine and...
  6. D

    Will This Perfectly Balanced Rocket Fly Upward or Bounce Continuously?

    I have a question about rockets. Consider a rocket, with a perfect dynamic fulcrum and center of balance (lets say its a magic rocket ship maybe.) Anyway, this rocket never rotates in flight, and has continuous and stable thrust through the flight. Would it continually bounce up and down or...
  7. Z

    Rockets on a car's effect on velocity?

    Homework Statement a rocket is on a car. the car is going to the right. a rocket is fired at 45 degrees angle towards the right. what is the change in velocity (if it changes at all) Homework Equations The Attempt at a Solution I was imagining like a gun firing, and therefore...
  8. A

    Why aren't hybrids used more often in spaceflight?

    What do you guys think about hybrid rocket engines compared with other the other kinds? What are the advantages of using one as opposed to a pure solid or liquid rocket?
  9. T

    Comparing Rockets and Missiles - What's the Difference?

    what is the diference betwin a rocket and a misile? from what I can tell,a rocket is something small,like a bazooka,or at most an anti-air rocket,and a misile is something huge,like a torpilo,or a nuke,or something really big,but I'm not shore,and there might be several "oficial" diferences...
  10. S

    Exploring the Relationship Between Rockets and Newton's Third Law

    Why do rockets behave so well in accordance to Newtons third law
  11. J

    When Does Rocket A Receive Rocket B's Signal?

    Homework Statement Two Rockets A and B depart from Earth at constant speeds of 0.6c in opposite directions, having synchronized clocks with each other and with Earth at departure. After one year as measured in Earth's reference frame, rocket B emits a light signal(call this event E1). At...
  12. B

    Two Relativistic Rockets Pass eachother

    Homework Statement Two relativistic rockets move toward each other. as seen by an observer on Earth rocket A of proper length 500m travels at a speed of .8c and rocket b of proper length travels at speed .6c. What is the speed of the rockets relative to each other? the earthbound observer sets...
  13. A

    Torque and Rockets for Spinning Satellites

    Homework Statement To get a flat, uniform cylindrical satellite spinning at the correct rate, engineers fire four tangential rockets as shown in the figure. If the satellite has a mass of 3600 kg, a radius of 4.6 m, and the rockets each add a mass of 230 kg, what is the required steady force...
  14. R

    Rockets in Space: Need for Engines to Change Direction

    Once rockets leave the Earth's atmosphere they would have a high velocity so how come rockets use their engines when they're in space if there's no air resistance? The only reason I can see why they would need to use them is if they wanted to change direction.
  15. A

    Time and Space: What Happens When Two Men Meet in Adjacent Rockets?

    this question forom a student couldn't be answered by professor in class- imagine 2 men in two rockets adjuscent to one other.you are one of them. rockets begin to move, say for example, revolve around sun. after few fast revolutions, they stop near each other. now you and the other man meet...
  16. K

    Why do we have to observe ultraviolet radiation using rockets or satellites?

    Why do we have to observe ultraviolet radiation using rockets or satellites, where as balloons are sufficient for obervations?
  17. S

    What Does the String Test Reveal About Rocket Stability?

    "String Test" for Rockets This doesn't slot easily into any of the Physics Forum's categories but I guess it is kinda aerospace engineering... And my uni's space society we make small model rockets, just simple things out of paper and card and a small motor. On the sheet of instructions we...
  18. M

    Universal Gravitation and rockets

    [SOLVED] Universal Gravitation Homework Statement A small rocket is launched vertically, attaining a maximum speed at burnout of 1.0x10^2 m/s and thereafter coasting straight up to a maximum altitude of 1519 m. Assuming the rocket accelerated uniformly while the engine was on, how long did it...
  19. L

    Photonic Rockets - Mass & Speed Effects

    Homework Statement one is powering a photonic rocket with photons. what is the speed it reaches when its mass is half its starting mass. and per say you would start stoping then ... how would that look like (equations and sentences) Homework Equations invariance of the 4D vector of...
  20. T

    Calculating Relativistic Rocket Performance

    Hello there I've been looking at this page http://en.wikipedia.org/wiki/Relativistic_rocket at the relativistic version of Tsiolkovsky rocket equation, but something puzzles me With chemical rockets, the mass that is being converted into energy is so tiny that almost all fuel...
  21. L

    Rockets burning in terms of momentum conservation

    Can some one help me with this question please. don't really understand mathematically analyse, using diagrams, rockets burning in terms of momentum conservation and the rate of fuel consumption R and derive the acceleration for a rocket during its launch stage.
  22. G

    Ideal area difference for rockets

    What is the ideal area difference between the nozzle cross-sectional area and inner engine cross-sectional area for a rocket engine for getting the most thrust? The greater the difference in area the higher the velocity of the exit gas but that also increases the pressure inside limiting the...
  23. A

    Space Rockets and Space Aircrafts

    I was wondering if nuclear power is being used in pushing and thrusting Space Rockets when launching out from the earth? Cheers. :smile: Amir Fahd.
  24. J

    Relativistic Fireworker: Exploding Rockets at V=C/2

    suppose an imaginary fireworker that launches rockets at a v=c/2 ( could be any velocity, but near light), and the rockets are programmed to explode at certain time T according to relativity there must be a certain delay in the explosion seen from the fireworker frame , and he should see the...
  25. W

    A rockets force in different enviornments

    a rocket will not produce the same force under water, in air, or in space. is this correct? I would think that according to Newtons 3rd law the force would be different in each enviornment. am i right?
  26. G

    Can a Pipe Rocket be Made for a Water Rocket Model?

    Hello friends, I am just a begginer of model rocketary. I just felt it is better to start with water rockets since i can't get much of the rocketary kits in the place i am living with. I know it is not such big topic to be discussed under a engineering thread, but still as an amateur i will...
  27. A

    Nuclear Fusion Rockets v.s Fission

    If I'm correct nuclear fusion rockets, (if used the right way), can go up to 10% the speed of light. THis is while nuclear fission goes 5% the speed of light. Yet NASA is working on craft that can make a "Earth-Mars-one way in two months". This is better then our current six month. Yet if I'm...
  28. C

    Slowing Photons: A Look at Light Speed Rockets & Measuring Slower Speeds

    How can a photons velocity be slowed down when they pass through air, water, etc? If photons can be slowed down to slower than light speed, then would it not be possible for a "futuristic lightspeed rocket" to catch up to a photon? And also how can someone measure a slower speed (other than...
  29. D

    Is nuclear fuel safe for space missions?

    is there technology to use nuclear fuel for space rockets? what could be the fastest and cheapest way to transport 100000000 kg from Earth to mars? can fission be an alternative? help!
  30. A

    Understanding Solid Fuel Rockets: Tail or Head, What's Best?

    Can somone explain me how solid fuel rockets works? Where should I start the reaction, at the tail or at the head? What fuel is the best?
  31. M

    How long did the rocket remain in the air?

    hey, i have a simple question... a rocket was launched 33degrees above the horizontal at a speed of 760m/s. it accelerates 15m/ss until it burns out after 10sec. how many sec did it say in the air? here s what i did: vertical speed = 760sin33 = 413.9 m/s horizontal velocity = 637.4 m/s...
  32. D

    Water Powered Rockets: Where Does the Energy Come From?

    What kind of energy is stored when u pump air into a bottle ie plastic bottle rocket. When it is launched, it has KE, but where does the KE comes from? the compressed air? what kind of enery then? n how do u calculate the enerygy stored inside?
  33. Clausius2

    A collateral question about rockets

    My question is about the rocket aerodynamics. I'm getting in a course of CFD (computational fluid dynamics) in my university. We have to do a project for this quarter. And I thought in modelling (with Matlab) the supersonic aerodynamics of the Soyuz/ST rocket. I'm only going to test the leading...
  34. S

    Exploring CO2-Powered Rockets: Ideas, Questions & Opinions

    Hi. I've been wondering about these disposable CO2 capsules for airguns: Please share opinions on my reasoning, any hints or ideas of how to calculate this, what to look for and so on will be appriciated. What if I punched a hole in the seal of one of these capsules, how much thrust would...
  35. A

    Why must rockets and bullets spin

    why must rockets and bullets spin when they are in motion in order to move in the intended motion? what does the spinning motion do? does it produce a force to matian the centre of gravity at the centre? and what if the bullet is a perfect sphere, does it still need to spin?
  36. E

    Calculating Optimal Fill for Air and Water-Powered Rockets

    My son & I will soon be building water + air-powered rockets for cub-scouts with soda-bottles and compressed air. You put so much water in a bottle, pressurize it, and release it upwards... Now, if nearly full of water, it would not go far, nor if nearly empty, using only air, but if optimally...
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