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In ion drive, we use ionized gas. With particle accelerators, we use high-energy particles. Given that colliders expend huge amounts of energy to propell a handful of particles, I speculate the particles can be used as propellant just like with an ion drive.

Given the higer energy output compared to ion drive engines, would that be possible? Is the energy source compact and not too heavy to offset the benefits? What if we experimented with light vs. Heavy particles and even ions?

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  • $\begingroup$ Both uses electric field to accelerate charged particles, but ion drive rely on reaction force to work while particles accelerator just want to use these particles as crash test dummies. $\endgroup$ – user6760 Sep 4 '17 at 11:19
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    $\begingroup$ You do know what ion engines are and how the rocket equation works? Putting an LHC style particle accelerator on a spaceship will kill your fuel fracion, no matter how high the Isp gets. Thats why we use small accelerators, which are called ion engines. $\endgroup$ – Polygnome Sep 7 '17 at 18:57
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Well ... the typical particle accelerator is several miles across, and 180 MW energy https://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/faq/lhc-energy-consumption.htm . The mechanical pressure of the particles inside is sufficiently low that standard photographic films and metal foils show no visible mechanical reaction to being struck by the particle stream.

At a high level, the energy in the particle accelerator is expended in shattering atoms into their component parts, at a more detailed level, the bulk of the energy is expended in the cryogenics and support services to keep things running. Very little energy is expended on actualy accelerating particles. What makes ion drives attractive is the low mass and energy consumption and ability to function over a long time. A particle accelerator is high mass, high energy consumption, , and wasteful in terms of its ability to convert stored energy into kinetic energy.

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  • $\begingroup$ While I think that there is nothing wrong with the facts in this answer, one has to add that "current particle accelerators" are like that. We are centuries away from real space ships though. This is sci fi of course, so is there any reason why one cannot build an accelerator that is a bit more useful? I think for this answer to be perfectly on topic, you have to comment on why you think this cannot be improved $\endgroup$ – Raditz_35 Sep 4 '17 at 11:08
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You seem to have a fundamental misconception here. An ion drive IS a linear particle accelerator: the particles being accelerated are ionized atoms. That's also what is usually accelerated in a particle accelerator (though electrons can also be used). The LHC https://en.wikipedia.org/wiki/Large_Hadron_Collider for instance can accelerate protons or ionized lead atoms.

So you could in theory use a linear accelerator such as SLAC https://en.wikipedia.org/wiki/SLAC_National_Accelerator_Laboratory#Accelerator The only problem is that the thing is 2 miles (3.2 km) long, so getting it in space (or building it there) is going to be a bit of a challenge.

Using a circular synchrotron-type accelerator, though, is not a good idea. The problem is that while the particles are being accelerated in a circle, they radiate energy ("synchrotron radiation": https://en.wikipedia.org/wiki/Synchrotron_radiation )

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  • $\begingroup$ The reason I chose to try the accelerator is it higher power compared to the ion drive. Think how much power is used (In the order of Megawatts) to accelerate the particle. The assumption was that the particle receives enough kinetic energy so that a reaction drive would be achievable. $\endgroup$ – Christmas Snow Sep 5 '17 at 9:52
  • $\begingroup$ @Christmas Snow: The questions here are where you get the power from, and now much mass do you devote to the accelerator part of the ship. And an ion drive IS a reaction drive. $\endgroup$ – jamesqf Sep 6 '17 at 4:15
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It would simplify the engine design, you'd get move fuel per unit fuel weight, and the fuel would be more effective to higher speeds, those are the pros. The cons are that the fuel is subatomic particles, they will cause serious containment issues, high speeds in accelerators are usually achieved using circular tracks in space that will cause gyroscopic precession, which you'll have to correct for every step of the way from design right through flight. I'm not 100% sure but I think the Ion Drive is a more efficient user of electrical power too.

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  • $\begingroup$ Yes, I agree with you about gyroscopic procession. I didn't think at first it has to employ a circular path, or else it would be too lengthy and therefore heavy. A pair of accelerators spinnng the particles in opposite directions seems practical. $\endgroup$ – Christmas Snow Sep 4 '17 at 16:55
  • $\begingroup$ Yeah I think that works as long as you use some kind of synchronised fuel injection model. I don't really grok precession in orbital flight mechanics, non-gravitational vacuum physics are just plain hard on the human brain. $\endgroup$ – Ash Sep 4 '17 at 17:06
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The ideal ion engine uses ionized helium as propellant. The helium is created by fusing 4 hydrogen atoms. This produces something like 25 Mev of energy. 25 Mev is a trivial linear accelerator, although to get decent thrust you will need to handle significant currents.

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