What are the equations for fission-based spacecraft propulsion?

[Arjun Wasan]

Hello I'm working on a project to create spacecraft engines that use fission to produce thrust. I will be coming up with many equations and I wanted to have them checked. If you could review them and give me some feedback that would be great. Here is the first equation that describes how the fission produces force:

(em*ea)*sc=sca

where: em - mass of energy released
ea - acceleration of energy released
sc - mass of spacecraft
sca - acceleration of spacecraft

 

[Astronuc]

(em*ea)*sc=sca

The units of this equation do not work.

F(propellant) = F( spacecraft ) or ma(propellant) = ma ( spacecraft ).

(em*ea)/sc=sca would be more appropriate, but that's too simplistic. This is only an equivalence and does not describe how fission produces thrust, rather it only describes the acceleration of a spacecraft assuming some thrust from a fission system. In order to describe thrust, one must show the change in momentum of the propellant and the mass flow rate of the propellant.

 

[Bigjoemonger]

Fission produces energy in the form of heat. That heat is then used to heat water to create pressure which propels it through a pipe to turn a turbine and create electricity. But even then the electricity cannot create propulsion because it's a spacecraft in a vacuum. There's no medium to manipulate to move yourself in a vacuum.

The only way I can see this would work on a spacecraft is if you heated water into steam and shot it out the back of the ship. But that would be a significant waste of a very finite resource and would not produce much thrust.

 

[sirios]

Hello I'm working on a project to create spacecraft engines that use fission to produce thrust. I will be coming up with many equations and I wanted to have them checked. If you could review them and give me some feedback that would be great. Here is the first equation that describes how the fission produces force:

(em*ea)*sc=sca

where: em - mass of energy released
ea - acceleration of energy released
sc - mass of spacecraft
sca - acceleration of spacecraft

its idea in general is very interesting but the equation does not demonstrate the rate of variation of the acceleration, that is in a celestial body approach its acceleration will have to assume the minimum possible, having this in mind you have to have control of the fission depending of the chemical compound you will use, but the idea is very good, continue to refine the calculations that you will go away, but the calculations can not take simplistic calculations.

 

[Dennis Jasbey]

Rockets powered by nuclear fission were under development in the USA from 1955 to 1972.
See Project Rover at Los Alamos.
And the NERVA and KIWI nuclear-powered rocket engines.

 

[Bigjoemonger]

Oh that's cool. I didn't know that was a thing. Just saw a video that they're starting to look into it again as an engine for going to mars.

 

[etudiant]

The USAF also did work on nuclear propulsion under the Timberwind program, with Grumman as the contractor.
I believe that the program got far enough in the engineering stage that hydrogen flow tests through electrically heated core simulations were performed.
It was ended sometime in the late 1970s, after a test glitch iirc.

 

[gmax137]

don't forget Project Orion
https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

 

[Dennis Jasbey]

NERVA and KIWI used actual fission reactors producing up to 1,000 MW of heat.
The incoming fuel was liquid hydrogen or ammonia, and ultrahot hydrogen went out the nozzle.

 

[skeptic2]

There is an interesting book, though a little dated - it was published in 1979. It discusses the Orion project among other things. One of the other things was how large a nuclear bomb would be needed to bring down the World Trade Towers - answer: about a kiloton. The name of the book is The Curve of Binding Energy.

 

[jim hardy]

The name of the book is The Curve of Binding Energy.

Very interesting book. John McPhee is author.

Another is Freeman Dyson's "Disturbing the Universe" . He's about the last of the Manhattan project physicists. A truly 'Great Man' IMHO with an unusual amount of practical common sense..