What is Rocket engine: Definition and 52 Discussions

A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordance with Newton's third law. Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Vehicles propelled by rocket engines are commonly called rockets. Rocket vehicles carry their own oxidizer, unlike most combustion engines, so rocket engines can be used in a vacuum to propel spacecraft and ballistic missiles.Compared to other types of jet engines, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest specific impulse). The ideal exhaust is hydrogen, the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity.Rocket engines become more efficient at high speeds, due to the Oberth effect.

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  1. T

    Water Rocket Science Project by Tanguy: Reach 11,2k m/s!

    Hi ! I'm a French student in Terminale (12th grade equivalent) and I have to do an oral presentation of 5min (Grand Oral) for my baccalauréat linked with my professional project. As I want to become an engineer in astrophysics, I want to talk about water rocket and the theoretical possibility to...
  2. Ozen

    Why Not Titanium Alloy Rocket Engine Nozzles?

    Industry standard right now is a copper alloy (usually an aluminum bronze) inner liner to promote heat transfer to the coolant channels and the walls of the channels and outer liner are usually made of an INCONEL alloy, usually either 625 or 718. But INCONEL is VERY expensive and heavy. The...
  3. M

    How to Build an Isopropanol Rocket Engine?

    Hello, I'm wondering how I could make an isopropyl alcohol rocket engine. Currently I'm testing with plastic bottles, and that's not quite exciting. The alcohol quickly burns out because it is just some vapor in the bottle. There also isn't enough oxidizer, as the bottle quickly fills in with...
  4. Benjies

    The vacuum optimized Raptor: No attempt at an expander-bleed cycle

    Hello all, The merits of the full-flow cycle are without question and have been fielded with Starship tests to the point of my complete buy-in into Raptor's capability as a launch engine. Elon Musk loosely discusses further refinement of their vacuum-optimized engine that they have created...
  5. R

    Understanding High Thrust of Vacuum Rocket Engines

    Why do vacuum rocket engine always producing high thrust than sea level rocket engine ? for example spacex's merlin vacuum engine produce more thrust than merlin sea level engine. And it is due to the big nozzle with large area in vacuum engine because when the flow reaches mach 1 in the throat...
  6. Jregan

    Rocket Engine Failure: Calculating Velocity at 1055m/s | 21.1*50 = 1055

    21.1*50=1055 1055m/s is the velocity when the engine fails. I don’t know what the time should be in the second equation.
  7. Roy S Ramirez

    Measuring the Discharge Coefficients of a Rocket Injector

    Hello everybody! I hope you are all doing well. I built a liquid rocket injector and the following feed system: I started to do hydro-static tests (cold flows) and a program I wrote records all the data for me (except for the flow rates which I measured experimentally by collecting the water...
  8. Roy S Ramirez

    Adjusting the pressure drop in an injection plate

    Hello everybody, I'm designing a gas pressure feed system for a hydrogen peroxide - ethanol rocket engine, and after analyzing the devised injection plate, I noticed it is very sensitive to the propellants' pressure drops and discharge coefficients. Once the plate is manufactured, the only...
  9. Roy S Ramirez

    Injector pressure drop in a liquid rocket engine

    Hello everybody, I hope you are doing fine. I'm currently designing an injector for a hydrogen peroxide - ethanol engine, and the following formula is confusing me: Q = Cd * A * sqrt( 2 * dP / rho); where Cd is the discharge coefficient, A the total area, dP the pressure drop, and rho the...
  10. Roy S Ramirez

    Relationship between volumetric flow rate and pressure

    Hello everybody, This is my first post. I've been working on a liquid rocket engine for a while, but I have never gotten to work on its feed system (fluid mechanics), until recently. We are using a very simple pressure fed system, and its main goal is to deliver the propellants at a specific...
  11. M

    I on my rocket engine thrust equation

    I have been working on a rocket engine and I have cad models and everything and I am getting ready to build it. Then, I was running over the numbers one more time and I realized that the thrust I was getting was completely different from what I should have been getting. The big problem is the...
  12. yrjosmiel

    Maximum delta-v of a rocket engine

    So I was browsing wikipedia when I encountered: What does this exactly mean? How does one calculate for this? << Adding link to the table >> https://en.wikipedia.org/wiki/Spacecraft_propulsion#Table_of_methods
  13. EL_bob

    Magnetic assisted rocket engine

    Hello everybody! I have been thinking about something for a while now. I would like to make a magnetic nozzle for a rocket engine. Basically, I would like to ionize the hot and high pressure gaz in the combustion chamber and then use a strong magnetic field to adjust the nozzle throat...
  14. J

    Rocket Engine: Centripetal Force to Vector thrust

    Hey guys, I'm new to the forum and I have a question that has stumped several of the professors at my school. My idea is to use an electric motor with a solid rocket engine on a thrust stand to spin the exit cone. The concept would make use of centripetal force to increase the pressure of...
  15. R

    Hobby rocket engine experiments

    I've started making my own sugar-based hobby rocket engines and I want to work on creating a de Laval nozzle for the specific fuel type and configuration I'm using. I don't have the resources to measure things like chamber pressure and exhaust temperature, so I wanted to try and develop an...
  16. Const@ntine

    Understanding Forces and Motion in a 3D Coordinate System

    Homework Statement A toy rocket engine is securely fastened to a large puck that can glide with negligible friction over a horizontal surface, taken as the xy plane. The 4.00-kg puck has a velocity of 3.00ˆi ms at one instant. Eight seconds later, its velocity is (8.00ˆi + 10.0ˆj) ms. Assuming...
  17. oobgular

    Rocket engine operating in a vacuum

    Homework Statement So suppose there is a chemical rocket operating in the vacuum of space (assume it's a perfect vacuum). It generates a hot gas with a total enthalpy of h. What's the final speed of the rocket exhaust, in terms of h? Homework Equations The energy equation seems to be useful...
  18. wolram

    New rocket engine may enable trips to Mars

    https://www.sciencedaily.com/releases/2016/09/160929161628.htm Return trips to Mars without refueling could be a step closer, thanks to a unique new thruster technology.
  19. Fancypen

    Ambiguity in part B -- Rocket engine failure....

    Question: A 7750 kg rocket blasts off vertically from the launch pad with a constant upward acceleration of 2.35 m/s^2 and feels no appreciable air resistance. When it has reached a height of 555 m , its engines suddenly fail so that the only force acting on it is now gravity. Part B: How much...
  20. Y

    Can Isopropyl Alcohol Be Used as Fuel for Rocket Engines?

    Y'know, just because. Will it be possible to create a rocket engine using isopropyl alcohol as fuel? Why or why not? (will be used just for show and not really for sending ships to space. I'd rather have an entire school intact than it being blown to bits if I used hydrogen)
  21. T

    Is there a limit on rocket engine exhaust velocity?

    I've been trying to figure this out for days. I'm told that atmospheric pressure imposes a limit on maximum possible exhaust velocity in the Earth's atmosphere, and that under STP conditions that limit is approximately 15,000 feet per second. But that doesn't make any sense. Suppose you had...
  22. rmoh13

    Is this a possible idea for an antimatter rocket engine?

    Antimatter can be contained in magnetic fields; what if we could somehow "propel" that magnetic field by using a magnetic nozzle when the small antimatter-matter reactions/annihilation occurs which produces thrust? This seems like a really stupid idea, but can you tell me some limitations about...
  23. David Morgan

    Ground-based Laser + Liquid Nitrogen Rocket Engine?

    No idea why this popped into my head on the drive home tonight, but here we go: Would it be possible to build a rocket filled with either liquid Nitrogen, or some other super-cooled substance, then use a battery of high-energy, ground-based laser beams pointed at the super-cooled propellant to...
  24. S

    Would this be possible in a Rocket Engine combustion chamber

    Lets say if i have a bell nozzle rocket engine such as this one : http://www.braeunig.us/space/pics/fig1-04.gif and inside the combustion chamber i have an average pressure of around 300 psi. If i wanted to feed in liquid fuel into it while the fuel pump is only able to supply 100 psi of fuel...
  25. N

    News Is the RD180 rocket engine ban going to impact space exploration?

    What do you guys think about the recent vote where the house of reps decided to ban (100-300 or so) imports of these Russian rocket engines? Seems like politicians and corporations looking to make a buck (like SpaceX) have succeeded in their lobbying for the ban on RD180 engine import. Is it OK...
  26. N

    Rocket engine vs jet engine efficiency

    Which are more efficient, Rocket Engines or Jet engines, and why? It would make sense that rocket engines are more efficient because they aren't effected by air pressure but I have been told by some people that actually Jet engines are more efficient so I am confused. If you know of any link...
  27. R

    Rocket engine gimballing - torque and angular acceleration question

    Hello Firstly i just registered, I am a final year computer science student and I am busy working on my thesis (the deadline is fast approaching) I am working this application of a rocket going into orbit and physics is not my forte. I need some help on converting the gimbal of a rocket...
  28. H

    Does a Rocket Engine Exert Same Force Regardless of Velocity?

    This is a problem I have never really understood. If a rocket engine is fired in a vacuum, does it exert the same force regardless of its velocity? If so, I don't know how to get around the following issue. Say that the chemical energy stored in a particular rocket engine is 100 Joules (I am...
  29. E

    How can Solar Thermal Rocket Engines revolutionize space exploration?

    Dear visionary inventors, megalomaniac engineers and audacious explorers, Chemical rocket engines aren't up to our desire to hop in the Solar system: go quickly to Mars, deviate Earth-threatening objects, and so many more missions. We need a higher ejection speed to save propellant mass, but...
  30. F

    Ice Sled Powered by Rocket Engine: Find t1, t2, v & Final Position

    An ice sled powered by a rocket engine starts from rest on a large frozen lake and accelerates at +38 ft/s2. After some time t1, the rocket engine is shut down and the sled moves with constant velocity v for a time t2. Assume the total distance traveled by the sled is 15750 ft and the total time...
  31. M

    Achieving VTOL with jet engine instead of rocket engine

    Jetpack International's T-73 achieves vertical takeoff with an actual jet engine as opposed to the rocket engines used by the majority of jetpack models. This allows it to have longer flight time (9 minutes as opposed to 30 seconds). Some fighter planes also manage VTOL with a jet engine, the...
  32. R

    Calculating Thrust from Rocket Engine Ejection Velocity

    The burned gases of a rocket engine are ejected from the rocket nozzle at a speed of 17,000 ft/sec. If the weight of gas ejected is one pound per second, find the thrust developed by the rocket. I don't really have an equation to use here but my guess is F = M\32.2 * Ejection Velocity...
  33. Filip Larsen

    Live! Witness TM65 Liquid Propellant Rocket Engine Testing

    A livestream video feed from the event has started and can be accessed via the CS homepage [1] or the corresponding blog on Wired [2]. Some background information about CS can be found on [3] together with a (very) short description on the TM65 [4]. [1] http://www.copenhagensuborbitals.com/ [2]...
  34. U

    Rocketdyne H-1 Rocket Engine, plans/blueprints

    Hello, I am searching for plans or copies of the blueprints for the Rocketdyne H-1 engine used in the Saturn I/IB rocket, any help would be appreciated.
  35. I

    Small Liquid Rocket Engines for Sale | Glow Fuel Propellant

    Hello, I'm in the process of building a small liquid rocket engine that uses glow fuel as propellant. Can anyone direct me to a company that sells small liquid rocket engines? Thank you.
  36. MattRob

    Home-Made Liquid-Fuel Rocket Engine

    So I'm looking and researching to build a small liquid-fueled rocket engine. So far I think my choice for fuel is definitely unleaded gasoline because of it's high impulse when mixed with Gas-state O2 and how easy it is to obtain. Previously, I was looking at using Hydrogen Peroxide (H202) for...
  37. N

    How Does a Rocket Engine Maintain Constant Thrust While Power Increases?

    ok here's the problem. i really need on this. its not a calculation but more of an explanation. Consider a rocket engine. It delivers a constant thrust, which is the force exerted on the rocket by the expanding exhaust gases from the burning fuel.This typically is true in real life:both the...
  38. I

    Maximum altitude of a rocket engine

    Homework Statement A rocket is launched at an angle of 53 above the horizontal with an initial speed of 100 m/s. It moves along its initial line of motion with an acceleration of 30 m/s^2 for 3 s. A this time its engines fail and the rocket proceeds to move as a free body. a. Find maximum...
  39. T

    Ramjet Rocket engine hybrid?

    I wanted to get some opinions on this, I am serious considering designing a ramjet rocket hybrid engine for my 3rd year mechanical engineering degree project and have started doing the research to see exactly how much work it entails I still can't quite decide... is this a realistic project? (my...
  40. F

    Liquid-fulled rocket engine efficency.

    "Acceleration increased during S-IC flight for two reasons: decreasing propellant mass; and increasing thrust as F-1 engine efficiency improved in the thinner air at altitude." This is from Wikipedia, so who knows. Why would a thiner atmosphere increase the thrust efficency of the engine...
  41. G

    Mixture Ratio for oxygen/propane in a rocket engine?

    What is the Air/Propane mixture Ratio? The Fuel Air Ratio of a Jet Engine is 15 to 1. This is for JP4. What is the Fuel Air Ratio for Propane Gas? I have learned the only difference between a rocket engine and pulse jet engine is the pulse jet runs on the oxygen that is in the air (30%...
  42. E

    Rocket Engine Exhaust Velocity

    I want to calculate the exhaust velocity of a rocket. This is the formula that I found at http://en.wikipedia.org/wiki/Rocket_engine_nozzles which is: V_e = \sqrt{{\frac{T*R}{M}}*{\frac{2*k}{k-1}}*[1-(P_e/P)^(^k^-^2^)^/^k] } Ve = Exhaust velocity at nozzle exit, m/s T = absolute...
  43. A

    Making a Solid Rocket Engine Abroad: What Can I Do?

    I really enjoy building model rockets, however, I moved oversees and can't get premade engins. Nor can I get potassium nitrate or any other common combustable. What can I do to make a small solid rocket engin??
  44. F

    Rocket Engine Combustion Chamber Equations

    Good evening all, I was wondering if anyone would be able to point me in the right direction to equations in regards to designing a proper combustion chamber for a rocket engine, as well as for the throat/De Laval nozzle as well. I've looked around and I can't seem to find anything that...
  45. M

    Rocket Engine Thrust Formula Help

    hello, does anyone know how to derive the ROCKET ENGINE THRUST formula: T = P/R AV + (P-B)A i know you need to use F=ma and Momentum flow rate equations to get the first place. but what do you do after that? Any help would be greatly appreciated. Thanks, Michael
  46. A

    Torque on a Turbine, Air Breathing Rocket Engine

    Hi All, I'm a junior in HS. I have a research project due this semester for Physics B (first year introductory college physics). Last semester I did some research on boundary layers, friction loss in pipes. This semester I've decided to do some investigation on air breathing rocket...
  47. B

    Homemade liquid rocket engine all based around a CO2

    Ok, so if there is a better place for this, please do move it mods, I just couldn't find a place to post project related stuff so I chose this part of the site. Anyways, I'm working on a homemade liquid rocket engine all based around a CO2 cartridge combustion chamber. This project also has the...
  48. kach22i

    What is the Next Generation Propulsion Technology at RRX Aerospace?

    FYI: http://www.rutherford-research.ca/rrx/aerospace/nextGenPropulsion.php Click link above to see pictures and description.
  49. Z

    Finding Cv values for Hydrogen and Water at high temperatures

    Currently, I am trying to find the optimal O/F ratio for H2 and O2 in terms of maximal gas escape velocities. I have researched Cp, and Cv values for H2O and H2 extensively, yet I can not find a function of their values depending on temperature. Does anyone know where I could find functions of...
  50. A

    Journey into Model Rocket Engine Making

    i have been into model rocketry for a very long time now, and i think that it is about time i learn how to start making the engines, does anyone know how to do this? the only explinations i have seen is one printed by Aerospace model rocket engine company who basically gave 10 reasons why you...