What is Rocket equation: Definition and 63 Discussions

The Tsiolkovsky rocket equation, classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity can thereby move due to the conservation of momentum.




Δ
v
=

v

e


ln




m

0



m

f




=

I

sp



g

0


ln




m

0



m

f






{\displaystyle \Delta v=v_{\text{e}}\ln {\frac {m_{0}}{m_{f}}}=I_{\text{sp}}g_{0}\ln {\frac {m_{0}}{m_{f}}}}
where:




Δ
v



{\displaystyle \Delta v\ }
is delta-v – the maximum change of velocity of the vehicle (with no external forces acting).





m

0




{\displaystyle m_{0}}
is the initial total mass, including propellant, a.k.a. wet mass.





m

f




{\displaystyle m_{f}}
is the final total mass without propellant, a.k.a. dry mass.





v

e


=

I

sp



g

0




{\displaystyle v_{\text{e}}=I_{\text{sp}}g_{0}}
is the effective exhaust velocity, where:





I

sp




{\displaystyle I_{\text{sp}}}
is the specific impulse in dimension of time.





g

0




{\displaystyle g_{0}}
is standard gravity.




ln


{\displaystyle \ln }
is the natural logarithm function.

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  1. R

    Rocket equation exhaust velocity question

    The rocket equation given by Delta V = Ve ln (Mo/M) says that Ve is the exhaust velocity of the rocket. The orbital velocity for Low Earth Orbit is about 7.8 Km/s. How then, is this velocity attained by a rocket which is fuelled only by a bipropellant rocket engine producing an exhaust...
  2. A

    Double stage Rocket Equation help

    Homework Statement okay the problem is there is a two stage rocket with a payload of 200kg and isp 2943m/s. It has a total delta v of 10km/s and at each stage it produces half of the total delta v. The question is to calculate the initial mass prior to launch, I've been told also that for...
  3. R

    Rocket Equation with varying gravity

    So, the rocket equation is F_ext = m(dv/dt) + u(dm/dt) where m is the mass of the rocket, v the velocity, u the effective exhaust gases speed, and F_ext the external forces on the system. If we take a constant mass ejection rate p, and take the external force to be the gravitational...
  4. V

    Rocket Equation for Booster

    Hi Can anyone help to write rocket equation with strap on booster. The exhaust velocity of the booster rocket and the core rocket is same? and The exhaust velocity of the booster rocket and the core rocket is different?
  5. C

    Netwons second law and rocket equation

    according to Newtons second law: \vec{F}=\frac{d\vec{p}}{dt}=m\frac{d\vec{v}}{dt}+\vec{v}\frac{dm}{dt}(1) ie force impelled on a body is equal to the rate of change of momentum however when we use calculus to derive rocket equation we get: m\frac{d\vec{v}}{dt}={\vec{v}_{gas\; relative \;to...
  6. A

    The Rocket Equation: Unraveling the Mystery

    In deriving the rocket equation, there is one part I don't understand. The velocity of exhaust with respect to the body is assumed to be constant, where: v(exhaust wrt body)=v(exhaust wrt inertial)-v(body wrt inertial) So assuming a constant mass flow rate, the rocket propellant exerts a...
  7. C

    Solving the Rocket Equation: Confusion with Signs

    recenty i read the rocket equation, derivation of, however i think i have a slight confusion with signs suppost initially a rocket has mass= M velocity= \overrightarrow{v} then at a time dt later, mass of rocket= M-dM velocity of rocket= \overrightarrow {v} +d\overrightarrow {v} mass of...
  8. J

    Ideal rocket equation application help

    Homework Statement I am trying to calculate the change in velocity of the space shuttle required for a low orbit currently in use by NASA which i believe can be done from the ideal rocket equation. launch mass = 2,040,000kg external tank propellant mass=730,000kg solid rocket booster mass...
  9. C

    Is the Rocket Equation True?

    is this equation true Fnet=[m(Vf-Vi)]/Delta T net force is equal to the mass times the change in velocity all over time thanks alot
  10. A

    Exploring the Rocket Equation: A Non-Mathematician's Perspective

    Hi. I'm curious how the science folks here would see this 'rocket equation' I formulated: Energy (E) = the cube root of mass (m) multiplied by 5 times the speed of light (C). I'm not a mathematician, I'm more into art. It was borne out from my visualization of the universe (an ideal future)...
  11. B

    Why is dm negative in the rocket equation derivation?

    I'll write the equation first, and then state my problem with it. mv=(m+dm)(v+dv)-dm(v-v') The book says that in the term (m+dm), that dm is a negative quantity. If I believe this, then what about the -dm(v-v') term? Why is dm negative? If I were to derive it I would have (m-dm) and...
  12. S

    What is the correct derivation of the relativistic rocket equation?

    I'm trying to derive the relativistic rocket equation, and I'm getting two different answers depending on the method I use. I think the first method is right, and they would agree if not for one sign in the second equation, but I can't seem to get rid of it. Can anyone tell me what I'm doing...
  13. L

    Solving a Rocket Equation: Mass, Velocity & Height

    Im having this problem with a rocket equation. Ill state the problem then show what I've done Let M = mass of rocket and fuel M_f = mass of fuel M_0 = rockets total initial mass (including fuel) (this is given as 10^5 kg) V_R = rockets velocity A 10^5 kg rocket has a total...
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