Particle Beam Weapons: More Than Just Flashlights?

[Konraden]

First things first, hey. New here obviously, figured I would say hey, enjoying\enjoyed the game. (I think I "beat" it, but I'm not sure). I've been trying to get X-Com: UFO Defense to run on my PC for two years now with no satisfactory luck. UFO:AI is something i've been so desperatly searching for since the begining of time. Thanks Dev's for throwin' in together over the last few years.

Now, to the Particle Beam Weaponry you guys enjoy so much. The idea of the weapons themselves sound good, but the actual physics seem...off.

You guys never really define what a particle is in your description. From what it sounds like, I first thought light photos, but laughed a little when I realized you basically created a flashlight. I realize that isn't what you are going for.

However, you could also say particle means atom, which is a legitamate defintion. To quote your UFOpedia

Particle-beam weaponry is designed to hit a target object with a stream of accelerated particles moving at near-light velocities, therefore carrying tremendous kinetic energy. Until now we've only seen the aliens use this technology in large UFO weapons. Now, however, they're using it on the ground in the worst way.

It says a stream of high-energy particles What exactly does this mean? From my understanding, launching particles out of a weapon isn't going to get you anywhere, especially considering the lack of mass.

Momentum = Mass * Velocity. (P=MV) Our velocity is "near light speeds,". C=299,792,458 m\s. However, our mass of these particles is undefined. Let's play out the numbers a little. (feel free to correct me, I don't have a PhD)

If M = .000001kg (one milligram, a rather large amount of particles to be swirling around inside the ammo-boxes). P = MV, P = .000001 * 299,000,000 (near light speed). P = 299kgm/s.

EDIT EDIT: Alright, I think I got it.

F = kgm/s², all I need to do is divide by a time for that momentum to stop in, say .001 seconds. (a millisecond). 299/.001 = 299000N ~ 68000lbs of force. Apparently my argument goes in an unexpected but still valid way. That gun will literally launch the shooter into orbit. Good luck.

Either I'm missing something, or you guys might need to rethink your weapon.

To me, the weapons seem impractical.

[blondandy]

relativistic momentum, p = mass * velocity * gamma

gamma = 1 / sqrt (1 - velocity^2 / c^2)

(I do have a degree in Physics)

The kinetic energy of a relativistic particle is generally more useful than talking about its speed. eg a 15MeV electron has a speed which is near c. in fact it is 5E-4 below 1 times c. Some folk even talk of its mass being 30 times its rest mass. I use these in radiotherapy most weeks.

The most obvious problem is storing the energy. If I recall the ufopedia correctly, they are accelerated and kept in a mini storage ring, in the gun's magazine. keeping particles moving in a circle using a magnetic field, could take very little energy.

I find it harder to suspend disbelief for the plasma gun: but this has been done to death before, so let's not go there again.

[Konraden]

Does it have the force to knock someone on their ass is the question. I never did the entire radiation thing.

[blondandy]

"near light speed" encompasses a huge range of energies (and hence momenta).

Unless the particle is specified (would have to be proton mass or heavier) and the kinetic energy (or something else that allows the momentum to be calculated), it is not possible to say.

[Konraden]

Play it out then, doc.

I'm a little ignoramus when it comes to anything more than kinetics, torque, and simple physics. Physics 101 doesn't cover much more. Radiation and Electric fields, magnetism, etc is all beyond me.

So, assume it is what you were rambling about. It's a proton traveling at the speed of light. You can calculate force and\or momentum from that, can you not?

[Aiki-Knight]

It's nice to see educated players really thinking about the game's concepts. I'm learning a lot. Please, science-majors, feel free to hash it out and maybe edit the UFOpaedia as required!

[Darkpriest667]

the main problem ive encountered with particle "beam" weapons is the radiation created from the reaction and energy needed to force particles to near the speed of light

Even if you could hold the weapon and not be killed by the recoil the radioactive isotopes created by the initial reaction would kill most people.  not immediately mind you.  But depending on the distance from the reaction anywhere from a couple of hours to a couple of days .


the military similarly had a problem with what they called ETC weapons.. Electro thermal chemical projectiles..   

[Doctor J]

The great old tabletop RPG Traveller had a book called "Fire, Fusion and Steel", which walked the reader through the creation of weapons or vehicles to order.  The writers did have to make some assumptions, but had quite a bit of hard research under their belts.  Anyway to get to the point, the section on particle accelerators was quite informative as to the how and whys of charged particles [better in atmosphere] and neutral particles [better in vacuum].  Ions or subatomic particles can be accelerated to near light speeds, and at such speeds relativism kicks in and effectively increases the mass.  The main problem in making a small particle accelerator is not the amount of energy required, but the length of the barrel [called a 'tunnel'] required to focus the beam.  Keep in mind that in Traveller particle weapons were typically used as the spine of a battleship, though they were also seen as the main armament on some high-tech tanks.  I tried designing a man-portable particle accelerator, but the effective range was only three meters - hardly worth it!  Suffice to say that every game designer has to make their own assumptions.

[DanielOR]

My degree is, indeed, in physics.  This has potential to be seriously embarrassing - I know for a fact at least one more Ph D lurks here.  Please, please correct me - it has been a while since I've taken relevant classes.

A particle's energy, the sort one gets in an accelerator, is on the order of a MeV - Mega electron Volt.  That's an electron accelerated though a field of 1,000,000 Volts.  The trouble here is "e" - the charge of an electron - 1.62 x 10^(-19) Coulombs - a very tiny number.  Kinetic energy of a *single particle* in Joules is tiny. 

By comparison, a 10 g (0.01 kg) bullet traveling at MAC 1 (134 m/s, close enough) has the kinetic energy E = m v^2 / 2 = just under 90 Joules

So, are particle guns doomed?  Not quite...  First, inside a particle accelerator particles travel in bunches (honest geek term), though I won't hazard a guess of how many (little help, my brethren?)  Main point: it ain't the kinetic energy of a particle beam/bunch that kills - at least not by blunt force trauma.  A particle beam flies through a target and all the particles have a great chance to hit the atoms that make up a target.  Resulting in other particles, more collisions, creation of X-rays and all sorts of radiation.  None of the above is healthy for breathing things.  Imagine putting Fluffy in front of a strong beam.  For starters, Fluffy gets a small-ish hole where the beam passes.  I imagine the area around the hole also gets well heated.  And if Fluffy is OK with that, the ionization (ripping away of electrons) of most of the tissue will do serious immediate damage to the nerves, and eventual death from radiation sickness.

What makes particle guns not useful as hand-held weapons today is
1) size - As Dr. J pointed out small particle accelerators don't do much (your microwave ain't no rifle) and the strong ones tend to need a very large room at least.
2) absorption by the atmosphere - the particle bunches travel (are stored) in accelerator rings that are pumped down to vacuum.  Shoot them in the air and they particles start hitting the air molecules and the beam looses lethality pretty quick.

Applications: best bet is space-borne platforms that shoot particle beams at missiles, damaging them by burning holes and melting the electronics. 
Limitations: simple dense cloud cover would be a limiting factor for effectiveness AND space weapon platforms are not too maneuverable, which means would be easy targets.  A bit on the expensive side for a disposable weapon.

Sorry for the rent.  Please, please check this for unintentional BS.  I will do my best to look up details if there is interest.

[Darkpriest667]

Daniel the USAF is testing particle weapons for ramjets and scramjets for OOA (out of atmosphere) use.  they have been testing them for about 15 years.   Why has no one mentioned the rail gun (guass cannon) technology really surprises me.   Its much more developed and reliable in an atmosphere environment.

the problem i foresee with the bunches is that once the particles leave the tube their direction is not very controllable.  Also again you guys are failing to address the energy issue.


How much energy are we talking about using to shoot 15 or 20 particles

[blondandy]

Why has no one mentioned the rail gun (guass cannon) technology really surprises me.

have you read the bolter article?

the problem i foresee with the bunches is that once the particles leave the tube their direction is not very controllable. 

particles with mass equal to or greater than protons go in a reasonably straight line in air.

Also again you guys are failing to address the energy issue.

it is stored as kinetic energy in the magazine. the particles are kept at the speed they come out of the gun, but going in a circle. a magnetic field can keep charged particles going in a circle for no energy cost.

[DanielOR]

blondandy - just to add to your post...the bit of physics we are ignoring here is the strength of the magnetic field needed to make the damn particles go in a circle of a radius of an inch or two...For comparison: real accelerator rings are miles (often >10 mi) in diameter and involve magnets the size of furniture pieces.  And those are electric magnets that draw a fair bit of current.  Which is why most national labs have own energy sources (i.e. nuclear power plants).

Again, those in the field of particle/nuclear physics please, please correct me as needed.

[blondandy]

high temperature superconductors might be possible. then you can have whetever magnetic field you like.

for example MRI machines (medical scanners) have some damn strong fields. the permanent magnetic field is generated by superconductors. this has to be cooled using liquid nitrogen. keeping the nitrogen cold takes energy. it is not impossible that superconductors working at room temperature might be discovered.

electric current going in a loop generates the magnetic field. so, when the magnetic is installed, you just cool it and inject the current.

[DanielOR]

very good point.  High Tc superconductors would go a long way towards making smaller (portable) particle weapons.

[babunito]

Daniel, I concur with all the points you've made. In any case, even if I had some doubts, I would not have questioned you, since you are the one who still is active in the trade, while I moved to other pastures long ago.

Small effective interaction radius of the elementary particles makes them not the best candidates for shooting at fluffy organics. While the idea of blocking the accelerator's beam is far from brightest, the damage is done only thanks to millions of passes (Dan please correct me if I am the order of the magnitude off) of the particle cloud through the blocking genius within what would seem to us a fraction of a second. Heavily ionized and huge molecules with small density (like buckyballs or other fullerenes) are robust enough to sustain high stresses during acceleration and will have much bigger interaction radii for such applications. Due to huge initial momentum they should be lethal over much bigger distances compared to conventional bullets.