Is it possible to create a fission (or fusion) thruster?

[Paramecium8]

Aparently fuel is one of the biggest problems with rockets and spaceships, because the most part of rockets are fuel tanks, could nuclear fuel be contained and used to accelerate spaceships using less space and more power?

[swansont]

The fuel is also the ejected matter for standard rockets. That problem doesn't change.

 

Fission (or fusion) systems have a great deal of what in rocket terms would be "overhead" - extra mass you have to lift.

[petrushka.googol]

Aparently fuel is one of the biggest problems with rockets and spaceships, because the most part of rockets are fuel tanks, could nuclear fuel be contained and used to accelerate spaceships using less space and more power?

It is already being used to power space probes.

[Enthalpy]

It has been done with fission. NERVA was prototyped and tried:

https://en.wikipedia.org/wiki/NERVA

Fusion doesn't work properly on Earth up to now, so don't expect it in spacecraft.

 

Since the thrust is the product of the, let's say, "mass consumption" (ejected mass per second) and the ejection speed, you can reduce the amount of ejected mass if increasing its speed. And because the squared speed times the mass implies the energy, it takes more energy in order to save mass.

 

As we already use the most energetic chemical reactions, the next step seems to be nuclear, sure. But then, you have to ask the drawbacks. Personally, I hate the idea of throwing a nuclear reactor in the air. About 1 rocket in 20 misfunctions.

 

Also, there are alternatives. Solar energy is available if the craft isn't too far from the Sun, and this one isn't carried in tanks at the craft. Use it to accelerate the working fluid, and if the fluid's speed exceeds what is achieved by combustions (3-5 km/s) you save fluid. It's the purpose of

• Ion, plasma and similar thrusters. Already used on satellites and space probes. VASIMR is a high-power variant that will open new missions.
  https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket
• Sunheat engines that expel hydrogen. ESA had made paperwork on it, I prefer my variant (logically enough)
  http://www.scienceforums.net/topic/76627-solar-thermal-rocket/
• Just resistors can heat the fluid, it's called a resistojet and has been used. With ammonia the benefit is small, with hydrogen it's big.
• I must forget a few dozen ones.

You might also consider solar sails. For some missions they're better than anything, but they still remain to develop at the proper scale and mass. Some hints there

http://www.scienceforums.net/topic/78265-solar-sails-bits-and-pieces/

to test a rugby-pitch-sized one on Earth. Still a bit small, but more significant than the 10m gadgets we test up to now.

 

Different approaches can change the game too. One is called "in-situ propellant" or "in-situ resource utilization" where, for instance in a samples return mission or a manned Earth-Mars-Earth trip, propellant would be produced at the remote body from materials found there.

[Moontanman]

There is always the salt water nuclear rocket...

 

https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

 

Pretty much a continuous nuclear explosion...

[dimreepr]

There's also Project Orion.