What is Rocket propulsion: Definition and 51 Discussions

Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric entry.
Several methods of pragmatic spacecraft propulsion have been developed each having its own drawbacks and advantages. Most satellites have simple reliable chemical thrusters (often monopropellant rockets) or resistojet rockets for orbital station-keeping and some use momentum wheels for attitude control. Soviet bloc satellites have used electric propulsion for decades, and newer Western geo-orbiting spacecraft are starting to use them for north–south station-keeping and orbit raising. Interplanetary vehicles mostly use chemical rockets as well, although a few have used ion thrusters and Hall-effect thrusters (two different types of electric propulsion) to great success.
Hypothetical in-space propulsion technologies describe the propulsion technologies that could meet future space science and exploration needs. These propulsion technologies are intended to provide effective exploration of our Solar System and will permit mission designers to plan missions to "fly anytime, anywhere, and complete a host of science objectives at the destinations" and with greater reliability and safety. With a wide range of possible missions and candidate propulsion technologies, the question of which technologies are "best" for future missions is a difficult one. A portfolio of propulsion technologies should be developed to provide optimum solutions for a diverse set of missions and destinations.

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  1. Astronuc

    The Future of Rocket Propulsion, What To Do About Emissions

    https://www.bbc.com/future/article/20220713-how-to-make-rocket-launches-less-polluting
  2. Ozen

    Bi-propellant Liquid Fuel Engine Pressures Before Thrust Chamber

    Been reading Rocket Propulsion Elements 9th Edition and got approval from my university to design a bi-propellant liquid fuel rocket engine for my senior design project, and I've been understanding everything so far but I haven't quite found an answer to how the pressure works throughout the...
  3. V

    Trouble with a Rocket Propulsion question (Variable Mass & Momentum)

    I chose to set the upwards direction to be positive and dM/dt = R = 190 kg/s, so I can solve the problem in variable form and plug in. With the only external force being gravity, this gives M(t) * dv/dt = -M(t) * g + v_rel * R where M(t) is the remaining mass of the rocket. Rearranging this...
  4. E

    New type of rocket propulsion design, and why it might not work?

    Hi, *Excuse the crude visualization and possibly imprecise description - I'm not a rocket scientist :) So, I have a friend that has come up with a "new" concept for a rocket propulsion design, and although I have a hunch that it might not work better than existing designs I cannot really...
  5. 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...
  6. yucheng

    Rocket propulsion equation: what's the error here?

    Equation for rocket motion: $$\frac{d \mathbf{P}}{d t} = M\frac{d \mathbf{v}}{d t} - \mathbf{u}\frac{d M}{d t}$$ But $$\mathbf{F}=\frac{d \mathbf{P}}{d t}=M\frac{d \mathbf{v}}{d t}$$ So $$M\frac{d \mathbf{v}}{d t} = M\frac{d \mathbf{v}}{d t} - \mathbf{u}\frac{d M}{d t}$$ And $$-...
  7. A

    Rocket propulsion explained only through pressure differential

    Fluid can exert force to object(move object) only through pressure and tangential stress caused by viscosity. if we look at balloon rocket ,here is Newton 3 law action-reaction,but this 3 law as usual don't tell nothing how fluid really exert force to the ballon.. it exert through pressure...
  8. Parkerrhees

    Electromagnetic fluid acceleration as effective rocket propulsion?

    Let me preface this by saying I have no background in physics or any of the above other than hours and hours of reading. Could someone explain why (if a method was developed) we couldn't use EFA as a thrust system for a rocket? My reasoning is instead of using fuel to fight gravity and push...
  9. granzer

    Why variable geometry nozzles are not used on rocket engines

    Why is it that variable geometry nozzles, like those found on jet engine(iris nozzles), are not used as rocket nozzle to provide better altitude compensation?
  10. G

    Maximizing rocket velocity - shoot fuel at once, or slowly?

    I stumbled upon a 3-year old article from Wired that poses this question on rockets: Suppose I have two rockets with a mass M and fuel mass m. Rocket A shoots all the fuel at once (again, like a nuclear propulsion engine) with a fuel speed of u and rocket B shoots two blobs of fuel—first a shot...
  11. T

    Exhaust velocity of a fire extinguisher

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Hey, For our project we have to think of an experiment that can kind of simulate a rocket. We decided to use a fire extinguisher on a kart, since its mass constantly changes (same with a rocket)...
  12. M

    The EM Drive: Exploring the Possibilities of Laser Propulsion

    I just had this thought while watching a video about the EM drive...basically using 2 lasers to bounce them off prisms inside an object to push the craft through space at a small but constant acceleration...could someone explain why this would not work?...please see attached image :)
  13. Carlos PdL SdT

    How Fast Does Air Escape from a Pressurized Suit into Space?

    I have a weird question here. At what speed does air flow from a pressurized container at one atm into vacuum (rupture in ISS for example). I was watching the Martian and I wanted to see how much deltaV Mark Wattney can get by puncturing his suit, so I did my homework and saw that the spacesuit...
  14. F

    Newton's 3rd law & rocket propulsion (detailed explanation)

    I had someone ask me how rockets are able to accelerate in space and my initial answer was that the rocket fuel combusts and is heated into an energetic gas, the gas is accelerated out of the back of the rocket (i.e. the rocket exerts a force on the gas), then according to Newton's 3rd law, the...
  15. E

    How rockets take curved paths in space (absent gravity)

    This might have been answered before but it's something that has been bothering me. A rocket in space will move in a straight line. If I apply thrust, it still moves in a straight line unless I apply the thrust in a different direction. So unless I have rocket nozzles attached to the side...
  16. RAHIL008

    Why can't a rocket continue to travel without fuel?

    By Newton's first law of motion, every object will continue to be in state of movement or rest, until acted upon by external force. Now, why can't a rocket continue to travel after it was initially thrusted (do not know if its right word) by fuel ? like a satellite that is set in orbit with some...
  17. L

    Rocket Propulsion with gravity

    Homework Statement Earlier we considered a rocket fired in outer space where there is no air resistance and where gravity is negligible. Suppose instead that the rocket is accelerating vertically upward from rest on the Earth's surface. Continue to ignore air resistance and consider only that...
  18. A

    General Rocket Propulsion book

    Hello, I've always been interested in space and space flights and have often wondered how rockets are lunched into space, how their trajectories are defined, how they are sped up (like gravity assist), how they are slowed down (like the complicated trajectory of the Rosetta mission etc . . . I...
  19. praveenpandiyan

    Rocket Propulsion: Calculating Specific Impulse for Return Mission

    well. I have this question. That my rocket is launched from mar in an return mission to earth. To calculate specific impulse of the rocket. Should i consider mar or Earth gravity and if why!? Help me with this
  20. S

    Rocket Propulsion: Explaining How Hot Gases Propel Rockets

    Hi i am doing a project on the future of solar energy. While reading up on rockets and how they are propelled to escape velocity i noticed all references only tell us that the hot gases propel the rocket up. Could someone explain exactly how this happens. What i mean is does molecule collision...
  21. P

    Rocket Propulsion Homework: Calculating Travel Time

    Homework Statement A rocket in outer space has a payload of 4050.0 kg and 1.753·105 kg of fuel. The rocket can expel propellant at a speed of 4.300 km/s. Assume that the rocket starts from rest, accelerates to its final velocity, and then begins its trip. How long will it take the rocket to...
  22. L

    Rocket propulsion - Differential equations

    Homework Statement Suppose a rocket is launched from the surface of the Earth with initial velocity v_0 = \sqrt(2gR) , the escape velocity. a) Find an expression for the velocity in terms of the distance x from the surface of the Earth (ignore air resistance) b) Find the time...
  23. A

    Rocket Propulsion: Question About Relationship of V and M0/M(t)

    Did a question about this a few weeks ago, but I thought I might do another, as I don't quite get, what is going on. The relationship: v=vex * log(m0/m(t)) tells us that a rocket will attain greater and greater acceleration as time goes. However, when I try to simulate this in Matlab I get...
  24. A

    Rocket Propulsion: Understanding the Equation Behind It

    Look at the attached picture, which is taken from my textbook. I don't understand the equation: v = vex * ln(m0/m(t)) If the rocket looses mass at a constant rate, wouldn't that equation then say, that the acceleration decreases as time goes. Since the curve of ln(>1) flattens out. That...
  25. O

    Maximum thrust - theory of rocket propulsion

    Hello all, Just wondering if anyone can give me some guidance on this: the problem is an apparent contradiction I've stumbled upon. Some sources (e.g. www.braeunig.us) suggest that maximum thrust is achieved when Pe=Pamb (i.e. exhaust pressure = ambient pressure)l whereas others say that...
  26. T

    How Does Rocket Propulsion Affect Burnout Metrics and Altitude Achievement?

    Question I) For a single stage rocket: T = 955.23 kN, n = 16, Isp = 400 s and m0 = 70, 000 kg. The rocket is launched into a vertical trajectory. Neglecting drag and assuming g is constant at its sea level value, Find (a) the time until burnout, (b) burnout altitude, (c) burnout velocity, (d)...
  27. P

    Rocket Propulsion - Varying mass

    Homework Statement A rocket at rest in space, where there is virtually no gravitational force, has a mass of 2.55 * 105 kg, of which 1.81*105 kg is fuel.The engine consumes fuel at the rate of 480 kg/s and the xhaust speed is 3.27 m/s. The engine is fired for 250 s. Find the thrust of the...
  28. R

    Grade 12 Rocket propulsion Question

    Homework Statement A rocket for use in deep space is to have the capability of boosting a pay load ( plus the rocket frame and engine) of 3 metric tonnes to an achieved speed of 10000m/s with an engine and fuel designed to produce an exhaust velocity of 2000m/s. a) How much fuel and...
  29. M

    Solve Rocket Propulsion Problem: a = ((Vr)(k))/(1-(kt))-g

    Here is what I know a = (-Vr/m)(dm/dt)-g, I also know that 6. : m=m(initial)(1-kt). Under the conditions of 6: Show that a = ((Vr)(k))/(1-(kt))-g. I have tried to solve this problem by substituting dm/dt=-km(initial) into the first equation I have listed (a = etc.) but I have had no luck. Please...
  30. M

    Rocket Propulsion Differential Equation Solution Help?

    Homework Statement Consider the case of a rocket taking off vertically from rest in a gravitational field g. The differential equation is given by m\dot{v} = -\dot{m}v_{ex}-mg Assume the rocket ejects mass at a constant rate, \dot{m}=-k (where k is a positive constant), so that m=m_{0}-kt...
  31. J

    Calculate Speed of Exhaust Gas in Rocket Propulsion

    Homework Statement A Rocket is propelled as a result of the very rapid ejection of exhaust gas from the rear of the rocket. Given that the initial mass of the rocket and fuel is 5000kg and the 4000kg of fuel is burned in accelerating the rocket to a speed of 600m/s, calculate the speed of...
  32. G

    Rocket Propulsion: Solving a Variable Mass Equation of Motion

    State the fundamental equation of motion for a particle of variable mass. A rocket of initial mass m0 is fired vertically, under the influence of a uniform gravitational field, and expels propellant at a constant relative velocity c downwards. The propellant is completely consumed after a...
  33. A

    Rocket Propulsion Gas Injection

    Please help, book gives no examples relatively close to this. A rocket is fired in deep space, where gravity is negligible. If the rocket has an initial mass of 6000 kg and ejects gas at a relative velocity of magnitude 2000 m/s , how much gas must it eject in the first second to have...
  34. R

    Rocket Propulsion Homework: Find Thrust & Impulse

    Homework Statement A rocket operating with combustion chamber pressure and temperatures of 14MPa and 2500K respectively, has a throat diameter of 0.3m, and a nozzle area ratio of 50:1. Find the thrust and specific impulse developed by the motor with back pressures of 1 bar (10^5 Pa) and zero...
  35. C

    How Much Fuel and Oxidizer is Required for a Rocket to Reach 10,000 m/s?

    Homework Statement A rocket for use in deep space is to have the capability of boosting a total load (payload plus the rocket frame and engine) of 3.10 metric tons to a speed of 10 000 m/s. (a) It has an engine and fuel designed to produce an exhaust speed of 2000 m/s. How much fuel plus...
  36. N

    Rocket Propulsion Homework: Calculating Mass Loss R

    Homework Statement A Roadrunner F45 rocket engine, of mass 93g, is attached to a 2kg cylinder, which glides along a horizontal low friction nylon fishing wire. The thrust curve for the rocket engine is given. In reality, 30g of propellant are burned as the engine is ignited. Calculate the...
  37. C

    Rocket propulsion and vortexes

    rocket propulsion and "vortexes" Hi I have been reading a little about vortexes of late. ie hurricane shaped formations. and I wondered if such vortexes were deliberately designed into rocket propulsion systems. I have seen no examples of such in standard rockets whether they be powered...
  38. C

    How much fuel is needed to reach a specific velocity in rocket propulsion?

    Homework Statement The space shuttle, with an initial mass M = 2.41E+6 kg, is launched from the surface of the Earth with an initial net acceleration a = 26.1 m/s2. The rate of fuel consumption is R = 6.90E+3 kg/s. The shuttle reaches outer space with a velocity of vo = 4632 m/s, and a mass of...
  39. J

    Rocket propulsion fuel velocity

    Rocket propulsion In the serway textbook at the rocket propulsion section it is mentioned that If the fuel is ejected with a speed v_e relative to the rocket (the subscript e stands for exhaust, and v_e is usually called the exhaust speed), the velocity of the fuel relative to the Earth is...
  40. T

    Rocket Propulsion Speed of Fragments

    A fireworks rocket is fired vertically upward. At its maximum height of 75.0m , it explodes and breaks into two pieces, one with mass = 1.25kg and the other with mass = 0.240kg . In the explosion, 910 J of chemical energy is converted to kinetic energy of the two fragments. a) What is the...
  41. A

    What are the lessons learned from nuclear reactor design and analysis?

    I have been reading a bit lately about project orion and the NERVA project. Project orion seems like such a crazy project that you can't help to love it:approve: I am not suprised it got shut down however. But is there any research going on anymore in the states or any other country that is...
  42. J

    Rocket Propulsion Flight Time

    The height that a model rocket launched from Earth can reach can be estemated by assuming that the burn time is short compared to the total flight time, so for most of the flight the rocket is in free-fall. (This estimate neglects the burm time in calculations of both time and displacement. )...
  43. W

    How Does Rocket Propulsion Calculation Work with Changing Mass?

    Hello, I am not understanding how the book got it's answer from the supplied rocket propulsion example. "A rocket moving in free space has a speed of 3.0 x 10^3 m/s relative to the Earth. Its engines are turned on, and fuel is ejected in a direction opposite the rocket's motion at a speed...
  44. J

    Rocket Propulsion: Boosting 3.10T to 10K m/s

    A rocket for use in deep space is to have the capability of boosting a total load (payload plus the rocket frame and engine) of 3.10 metric tons to a speed of 10 000 m/s. (a) It has an engine and fuel designed to produce an exhaust speed of 2800 m/s. How much fuel plus oxidizer is required...
  45. e-realmz

    How does rocket propulsion used by space shuttles work?

    Jet propulsion in space? If space is "nothing" then how does rocket propulsion used by space shuttles work? What exactly do those blasts push off of?
  46. S

    Model Rocket Propulsion: The Power of Hydrogen and Oxygen Combustion

    If say hydrogen is ejected out of the tail of a model rocket and combusted with O2 of the surrounding air, will that propel the model rocket forward and will the propulsion be sustainable?
  47. U

    Rocket Velocity and Mass Ratio

    A large rocket with an exhaust speed of v=3000m/s develops a thrust of 24 million Newton. a. How much mass is being blasted out of the rocket exhaust per second and b. what is the max speed the rocket can attain if it starts from rest in a force-free environment with v=3000m/s and if 90% of...
  48. S

    Rocket Propulsion, Newton's second law

    I was reading a section about rocket propulsion in my general physics text and it came up with the following formula: m \frac{dv}{dt} = - v_{ex} \frac{dm}{dt} I don't have much trouble with this formula, but then it went ahead and substituted m dv/dt as the thrust experianced by the...
  49. P

    Boosting Speed with Rocket Propulsion & Momentum

    rocket propulsion/momentum A 1520 kg rocket has 4860 kg of fuel on board. The rocket is coasting through space at 94 m/s and needs to boost its speed to 348 m/s. It does this by firing its engines and ejecting fuel at a relative speed of 807 m/s until the desired speed is reached. How much fuel...
  50. S

    Questioning logic used for highschool rocket propulsion problem

    Standard rocket propulsion problem. We are supposed to derive an expression for the final velocity of a rocket being launched into space based upon the exhuast velocity (Ve), final mass (Mf), intial mass (Mo), g, and time. The only forces acting on the rocket throughout the motion is the force...
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