187 replies to this topic

[990Dreams]

Also, recently, I've been wanting to see a PPC with a Gauss capacitor replacing the normal ionization capacitor.

[bad arcade kitty]

not physics but i should say that this article made me smile for several reasons at once

http://www.sarna.net/wiki/Sea_Fox

>Vulpes Maritimus Strana Mechtis

>seal-like reptilian predator



so, firstly it doesn't look as a seal at all, it looks as a some kind of otter or beaver with a weird muzzle, also those pointy ears are useful on the surface only and it has typical legs and tail of an (at least partially) land animal, definitely not something like a seal

secondly, i don't think we can even relate alien animals to the existing taxonomy like 'reptiles' etc (and it's a very weird 'reptile' which looks as a mammal), but even if we could... the genus 'vulpes' (fox) is an existing genus of our earthern canines, 'vulpes vulpes' it's ordinary fox, 'vulpes macrotis' it's kit fox etc; canines are not reptiles... and i doubt they traveled through the space to settle a colony on strana mechty so we could use the name of an existing genus for alien animals

Edited by bad arcade kitty, 13 April 2015 - 02:54 PM.

[990Dreams]

Screw physics, let's discuss alien life.

What about the Taetae (Katetoa birds)? I find them to be intriguing.

[Strum Wealh]

bad arcade kitty, on 13 April 2015 - 02:53 PM, said:

not physics but i should say that this article made me smile for several reasons at once

http://www.sarna.net/wiki/Sea_Fox

>Vulpes Maritimus Strana Mechtis

>seal-like reptilian predator



so, firstly it doesn't look as a seal at all, it looks as a some kind of otter or beaver with a weird muzzle, also those pointy ears are useful on the surface only and it has typical legs and tail of an (at least partially) land animal, definitely not something like a seal

secondly, i don't think we can even relate alien animals to the existing taxonomy like 'reptiles' etc (and it's a very weird 'reptile' which looks as a mammal), but even if we could... the genus 'vulpes' (fox) is an existing genus of our earthern canines, 'vulpes vulpes' it's ordinary fox, 'vulpes macrotis' it's kit fox etc; canines are not reptiles... and i doubt they traveled through the space to settle a colony on strana mechty so we could use the name of an existing genus for alien animals

For the record, the book that the Sarna article references (Classic BattleTech Companion, pg. 143) actually says absolutely nothing about the Sea Fox being in any way either "reptilian" or "seal-like".

[Strum Wealh]

DavidHurricane, on 13 April 2015 - 02:10 PM, said:

Also, recently, I've been wanting to see a PPC with a Gauss capacitor replacing the normal ionization capacitor.

And what, precisely, would the difference be between a "Gauss capacitor" and an "ionization capacitor"?

[990Dreams]

Strum Wealh, on 14 April 2015 - 03:26 AM, said:

And what, precisely, would the difference be between a "Gauss capacitor" and an "ionization capacitor"?

For one, I imagine the PPC has something to ionize atoms to make the lovely plasma we all know, and a separate discharge device that shoots it out. It would certainly make it more energy and heat efficient.

The reason I'm thinking Gauss capacitor is because to accelerate a 200 pound slug of metal you need a lot of electricity. Probably more than the PPC uses. So replacing the two capacitors would be very... interesting, so to speak .

That or it would ionize so hard that it would explode. So yeah, fun stuff either way.

Edited by DavidHurricane, 14 April 2015 - 04:02 AM.

[Strum Wealh]

DavidHurricane, on 14 April 2015 - 04:00 AM, said:

For one, I imagine the PPC has something to ionize atoms to make the lovely plasma we all know, and a separate discharge device that shoots it out. It would certainly make it more energy and heat efficient.

The reason I'm thinking Gauss capacitor is because to accelerate a 200 pound slug of metal you need a lot of electricity. Probably more than the PPC uses. So replacing the two capacitors would be very... interesting, so to speak .

That or it would ionize so hard that it would explode. So yeah, fun stuff either way.

We can actually calculate how much energy a Gauss Rifle should need using a few known points:

• Gauss Rifle slugs have a mass of approximately one-eighth of one metric ton (that is, 125kg).
  
• The Gauss Rifle's muzzle velocity in human-survivable conditions (e.g. close enough to Earth-standard ranges of atmospheric pressure & composition, gravity, and so on) is consistently described as "hypersonic" (that is, at least Mach 5.0 (1701.45 m/s) and at most Mach 10.0 (3402.90 m/s)).
  
• The efficiency of the 45-stage DARPA coilgun is ~22% - that is, of the energy put into the system, only ~22% is delivered to the projectile for propulsion.
  
• The maximum practical efficiency of a coilgun is theorized to be "above 90%".

At Mach 5.0 at muzzle-exit, the Gauss Rifle slug would have a KE value of (0.50)*(125)*(1701.45^2) = 1.809*10^8 joules (J), or 180.93 megajoules (MJ).

• If the Gauss Rifle is 90% efficient, then the system would need (1.809*10^8)/(0.90) = 2.010*10^8 J, or 201.03 MJ, in order to fire.
  
• If the Gauss Rifle is 22% efficient, then the system would need (1.809*10^8)/(0.22) = 8.224*10^8 J, or 822.42 MJ, in order to fire.

For perspective, one megajoule is equal to 0.278 kilowatt-hours (that is, one kilowatt-hour is equal to 3.6 MJ), and a 160-liter barrel of oil represents approximately six gigajoules (6.0*10^9 J, or 6000 MJ) of potential energy.

----------

One implementation of a PPC (or PPC-like device) is as a device known as an "electrolaser".

"An electrolaser is a type of electroshock weapon which is also a directed-energy weapon. It uses lasers to form an electrically conductive laser-induced plasma channel (LIPC). A fraction of a second later, a powerful electric current is sent down this plasma channel and delivered to the target, thus functioning overall as a large-scale, high energy, long-distance version of the Taser electroshock gun."

In essence, the device would emit a relatively low-power laser beam (by comparison to a laser weapon) that ionizes the air it comes into contact with, creating an electrically-conductive "plasma channel" along which a pulse or bolt of charged particles (such as electrons, protons or ionized atoms/molecules) is projected.
The advantage to this is that it would (at least partially) counteract the effect known as "blooming", wherein "particles bump into one another under the effects of thermal vibration, or bump into air molecules" and "ions of like charge repel one another", thus causing the beam/bolt to lose cohesion and severely limiting its range.

The electrolaser developed and tested by the US Army even resembles the BT novels' description of the PPC firing as "an arc of man-made lightning".


Like its natural counterpart, such a weapon could deliver its damage instantaneously to a very small, specific area. It would serve to explain/justify the repeated description of PPC salvos as "cerulean arcs/beams of man-made lightning" (as that's pretty much what it would be - man-made "lightning" caused by the projection of charged particles that gives the Particle Projector Cannon its name) as well as the workings of and need for the field inhibitor - it would generate an electric (or magnetic?) field that would mitigate/prevent some form of harmful feedback along the original plasma channel.

It also serves to explain the Blue Shield Particle Field Damper (which apparently also includes some form of turbine if it's susceptible to damage by sucking up debris and such) - it draws in atmosphere, ionizes it, and ejects it, creating a cloud of ions around the target that reduces the potential across the PPC's plasma channel and dissipates some of the energy of the PPC's salvo through the ion cloud into the atmosphere, reducing the amount of energy that can be delivered to the target.

Thoughts?

Edited by Strum Wealh, 14 April 2015 - 11:57 AM.

[X-Ray]

Since this is about physics of Mechwarrior, I do have a Battletech related question.
Space flight physics: Let's say a Union-Class drop ship (spheric), starting from nadir jump point (actually doesn't matter), is falling towards a planet. The ship is on the right vector and is accelareting with 1g, which would mean I can walk the decks normally. Half way to the planet, the ship has to turn in order to reduce speed, while still falling towards the destination. In case of 1g "counter thrust", there should be 0g for the passengers inside, right? Now, let's say we do the same with a Leopard-Class drop ship, which is space shuttle shaped. Will the passengers be pushed towards the stern bulkhead for the first half of the flight?

[Egomane]

Kidon XRay, on 16 May 2015 - 03:54 AM, said:

Since this is about physics of Mechwarrior, I do have a Battletech related question.
Space flight physics: Let's say a Union-Class drop ship (spheric), starting from nadir jump point (actually doesn't matter), is falling towards a planet. The ship is on the right vector and is accelareting with 1g, which would mean I can walk the decks normally. Half way to the planet, the ship has to turn in order to reduce speed, while still falling towards the destination. In case of 1g "counter thrust", there should be 0g for the passengers inside, right? Now, let's say we do the same with a Leopard-Class drop ship, which is space shuttle shaped. Will the passengers be pushed towards the stern bulkhead for the first half of the flight?

No there would still be 1G for the passenger inside, when the ship is decelerating. You have 1G of acceleration still, just vectored in the opposite direction. The only time you have zero G is while the ship is turning itself around on the midway point.

In case of the Leopard, while it is build to look somewhat aerodynamic (it is still a flying brick) on the outside, the inside is accomodating for the accelerations deceleration with a fitting internal structuring.

[X-Ray]

But isn't the flight direction (trim) crucial for the direction of inertial forces? If gravity is generated by inertia, wouldn't the force change its direction accordingly (a bit like inside an elevator)?

[Egomane]

Ok... I guess I need to explain it differently.

You are right now standing (or sitting) on the planet earth. You are, at this very moment, accelerated with 1G towards the planet. This is the gravitational pull the planet inflicts upon you.

Now imagine, the planet teleporting from below to above you. What would happen? The gravitational pull, your 1G acceleration, is now suddenly coming from a different direction. Would you stay in position (flying) or would you crash into the planet above you?

Now imagine yourself in the dropship resting motionless in space. Because you'd have zero G while you are not accelerating in space you would be in free fall. Even if the ship where close to lightspeed, if it is not further accelerating you would have zero G. But we will start with no motion.

Suddenly the engines come alive. They push the dropship towards the planet you want to reach. The ship is accelerating with a force of 1G (9.78033 m/s²). You yourself are not accelerating. The ship pushes itself against you with it's acceleration. You get the feeling of gravity in the oposite flight direction.

At the halfway point the ship stops accelerating. You become weightless again and drift through the ship, while it spins around to aim the engines at the target planet. While the ship spins, you could walk on walls, as the wall are now accelerating until the ship has finished it's turn. For simplicity sake, you are right in the middle of the ship and do not notice that.

You and the ship are falling towards the target planet. You feel weightless but your velocity hasn't changed since the engines stopped. You are actually pretty fast on your way.

Now the ship ignites its engines again. Again with 1G (9.78033 m/s²). Your body is still flying with the end speed of the ships acceleration towards the planet. The dropship is getting slower now, but you remain at speed. You overtake the ship until you are hitting the floor again. The ship is now pushing against you because it is slowing down. You again feel 1G and can walk and act normally.

And in yet another picture:
You are sitting in a car at 100 mph. Behind you a car comes up and connects with your bumper. The car behind you accelerates, thereby accelerating your car and thereby you. You are pushed into your seat. (Gravity from the back)

You are sitting in a car, travelling at 100 mph. Suddenly another car puts itself in front of you and slows down until it connects to you. It hits the brakes, thereby forcing your car to go slower. You are pushed into the security belts. (Gravity from the front)

Edited by Egomane, 16 May 2015 - 06:33 AM.

[X-Ray]

Great explanation! Thanks for teaching a sociologist some physics! I've forgotten about passengers own velocity in my story. ;-)

[Nebfer]

Strum Wealh, on 14 April 2015 - 11:52 AM, said:

At Mach 5.0 at muzzle-exit, the Gauss Rifle slug would have a KE value of (0.50)*(125)*(1701.45^2) = 1.809*10^8 joules (J), or 180.93 megajoules (MJ).

• If the Gauss Rifle is 90% efficient, then the system would need (1.809*10^8)/(0.90) = 2.010*10^8 J, or 201.03 MJ, in order to fire.
  
• If the Gauss Rifle is 22% efficient, then the system would need (1.809*10^8)/(0.22) = 8.224*10^8 J, or 822.42 MJ, in order to fire.

For perspective, one megajoule is equal to 0.278 kilowatt-hours (that is, one kilowatt-hour is equal to 3.6 MJ), and a 160-liter barrel of oil represents approximately six gigajoules (6.0*10^9 J, or 6000 MJ) of potential energy.

Well the one wrinkle with the hypersonic Gauss slugs is the issue with recoil will be severe, but from what I have seen on that topic is even with the recoil most mechs at full speed have the motive power and mass to absorb the recoil when fired... so that they wont be flying backwords when they fire. But it would be a fairly hefty jolt. Another issue is that their often described as Nickel-Iron which dose not make for a ideal penetrator, nor dose the often used shape of a large cannon ball (which would be around 8 to 11 inchs in diameter) or Mellon shaped, though Im told that newer books (i.e. DA era or later source books) have dropped that depiction... The only other issue would be integrating Aerotech ranges but thats another can of worms...

Quote

One implementation of a PPC (or PPC-like device) is as a device known as an "electrolaser".

"An electrolaser is a type of electroshock weapon which is also a directed-energy weapon. It uses lasers to form an electrically conductive laser-induced plasma channel (LIPC). A fraction of a second later, a powerful electric current is sent down this plasma channel and delivered to the target, thus functioning overall as a large-scale, high energy, long-distance version of the Taser electroshock gun."

In essence, the device would emit a relatively low-power laser beam (by comparison to a laser weapon) that ionizes the air it comes into contact with, creating an electrically-conductive "plasma channel" along which a pulse or bolt of charged particles (such as electrons, protons or ionized atoms/molecules) is projected.
The advantage to this is that it would (at least partially) counteract the effect known as "blooming", wherein "particles bump into one another under the effects of thermal vibration, or bump into air molecules" and "ions of like charge repel one another", thus causing the beam/bolt to lose cohesion and severely limiting its range.

The electrolaser developed and tested by the US Army even resembles the BT novels' description of the PPC firing as "an arc of man-made lightning".


Like its natural counterpart, such a weapon could deliver its damage instantaneously to a very small, specific area. It would serve to explain/justify the repeated description of PPC salvos as "cerulean arcs/beams of man-made lightning" (as that's pretty much what it would be - man-made "lightning" caused by the projection of charged particles that gives the Particle Projector Cannon its name) as well as the workings of and need for the field inhibitor - it would generate an electric (or magnetic?) field that would mitigate/prevent some form of harmful feedback along the original plasma channel.

It also serves to explain the Blue Shield Particle Field Damper (which apparently also includes some form of turbine if it's susceptible to damage by sucking up debris and such) - it draws in atmosphere, ionizes it, and ejects it, creating a cloud of ions around the target that reduces the potential across the PPC's plasma channel and dissipates some of the energy of the PPC's salvo through the ion cloud into the atmosphere, reducing the amount of energy that can be delivered to the target.

Thoughts?

Interesting. Though IIRC their is more than one type of PPC around that was described in the fluff (TRO fluff), though man made lightning is the typical fluff when the fire in the novels -though I could be wrong.
For example the Manticores "Parti-Kill Heavy Cannon" PPC is described as different from other types in that it uses a series of magnetic collection bottles that store the reactor's energy directly, and then hurl that at the target as a sort of "energy shell".

Though as for the laser it would not be the first time a laser was used as an initiator, the Plasma Cannon/Rifle is stated as using a Laser to turn a large chunk of plastic foam into plasma and the fling that at a target (the barrel is ceramic lined, at lest for the infantry model).

Per Era report 2750 Small and medium lasers are free electron, while the large is a Gamma ray based laser
Though their are other types in use I believe, the Bulldog tank uses a unknown amount of Kyrpton gas for it's large laser (though it's not much as it's decidedly not a chemical laser). The older fluff of the Drilson mentions that it's Cyclops Eye large laser uses both laser tech and particle beam tech, supposedly a hybrid of both.

[990Dreams]

Nebfer, on 05 June 2015 - 10:06 AM, said:

Well the one wrinkle with the hypersonic Gauss slugs is the issue with recoil will be severe, but from what I have seen on that topic is even with the recoil most mechs at full speed have the motive power and mass to absorb the recoil when fired... so that they wont be flying backwords when they fire. But it would be a fairly hefty jolt. Another issue is that their often described as Nickel-Iron which dose not make for a ideal penetrator, nor dose the often used shape of a large cannon ball (which would be around 8 to 11 inchs in diameter) or Mellon shaped, though Im told that newer books (i.e. DA era or later source books) have dropped that depiction... The only other issue would be integrating Aerotech ranges but thats another can of worms...

Suspension in a magnetic field could reduce the recoil, with the main recoil coming from the sudden vacuum being created in front of the projectile in the barrel being rapidly refilled (which isn't a big amount of recoil).

Nickle-iron is both magnetically responsive and quite tough. Thus, it is more of a kinetic transfer weapon as opposed to a perpetrator (transfer as opposed to penetration is still a good way to deal damage). This idea is further supported by the ball/melon shape depiction, which would be used for transfer more than penetration. Now of course, there are some ways you could make it penetrate, and perhaps penetrate even more efficiently than an Autocannon.

Addendum: Also, considering recoil, you're thinking in a very traditional sense. A normal gun requires expanding gases to push backwards to create pressure to accelerate a bullet forwards. In a Gauss Rifle, you just accelerate a bullet forward, and as long as there is minimal friction, there should be no need for a force to go in the opposite direction.

Edited by DavidHurricane, 05 June 2015 - 01:03 PM.

[RedDragon]

DavidHurricane, on 05 June 2015 - 12:58 PM, said:

In a Gauss Rifle, you just accelerate a bullet forward, and as long as there is minimal friction, there should be no need for a force to go in the opposite direction.

Newton would like to have a word with you about that

While there wouldn't be a large force aimed backwards from the projectile, the magnets would experience the same force they are giving to the slug. But I guess that would be directed eccentrically outwards along the path of the accelerator, so in effect when the magnets are positioned circularly around the barrel, the force would counter itself?

[990Dreams]

RedDragon, on 05 June 2015 - 01:12 PM, said:

Newton would like to have a word with you about that

While there wouldn't be a large force aimed backwards from the projectile, the magnets would experience the same force they are giving to the slug. But I guess that would be directed eccentrically outwards along the path of the accelerator, so in effect when the magnets are positioned circularly around the barrel, the force would counter itself?

Practically the force would center itself and balance out enough to be negligible. The barrel may expand over time, but not to a damaging degree. The "equal and opposite reaction" would probably some reverse current and heat in the magnetic coils/rails.

[Adsbom]

It's been a while since I have done physics but I think you may need to consider this in more basic terms.

Imagine that initially you have the mech/slug system at rest, the slug is then accelerated to muzzle-velocity and exits the Gauss Rifle leaving you with a separate mech and slug system, ie two objects. Now if we consider this in terms of conservation of momentum the initial mech/slug system will have zero momentum (since at rest) and using the equation:
momentum of mech/slug = momentum of slug + momentum of mech
with Strum Wealh's values of m_slug = 125kg and v_slug = 1701.45 m/s, and assuming that the Gauss Rifle is fired by a mech of mass 65 tons and that all that mass resists the change in momentum we would have:
0 = 125*1701.45 + 65000*v_mech
which would give v_mech = -3.27 m/s == 11.8 km/h in the opposite direction to the slug. Which is not an unreasonable amount of recoil for a mech to dissipate, it would obviously rock backwards a little and you wouldn't want to be firing any other weapons at the same time because aiming would go out the window, but still within the realms of feasibility. Of course if muzzle velocity were higher or the mass resisting lower we could start to have problems...

[Nebfer]

Yeah I have seen this idea show up a number of times in debates, basically B-tech Gauss Rifles are stupidly powerful, at 2.2km/s your reaching 300 megajoules of Ke (why 2.2km/s well it's a bit of a play on the occasional Mach 2.2 quotes you see a few times). At 300 megajoules you are running into 16 inch shell battleship range in terms of Ke. At 1.7km/s the resulting Ke of 190 Megajoules is not to far off from 14 inch guns (~210 Megajoules).

As Adsbom noted the Recoil of these rounds is tremendous, this is not easily explained, This recoil issue was part of why for a time I saw the old mach 2.2 quote being used over the far more common Hypersonic quotes (I still see some who complain that it was a retcon...), as the recoil issue was to problematic for them. Battletech dose not have any inertial dampeners to hand the recoil like a number of other series.

That said it is possible that battletech dose have some fairly substantial recoil gear, it's possible that a good chunk of the mass of a Gauss rifle is devoted to it. On such example of this counter recoil gear is with the Zeus Heavy Rifle, in the novels it is treated as a 50 cal sniper rifle (as it is in the early RPGs, the later eds. it's more simply a 50 cal rifle), it is listed as firing a 45g slug at hypersonic speeds... Your looking at upwords of real life 30mm range. However it is mentioned that it dose come with counter recoil gear that makes it feel like your firing a 7mm rifle. So their is some evidence that B-tech dose seem to have rather effective counter recoil gear.

Edited by Nebfer, 22 June 2015 - 11:40 AM.

[RedDragon]

Nebfer, on 22 June 2015 - 11:39 AM, said:

Yeah I have seen this idea show up a number of times in debates, basically B-tech Gauss Rifles are stupidly powerful, at 2.2km/s your reaching 300 megajoules of Ke (why 2.2km/s well it's a bit of a play on the occasional Mach 2.2 quotes you see a few times). At 300 megajoules you are running into 16 inch shell battleship range in terms of Ke. At 1.7km/s the resulting Ke of 190 Megajoules is not to far off from 14 inch guns (~210 Megajoules).

As Adsbom noted the Recoil of these rounds is tremendous, this is not easily explained, This recoil issue was part of why for a time I saw the old mach 2.2 quote being used over the far more common Hypersonic quotes (I still see some who complain that it was a retcon...), as the recoil issue was to problematic for them. Battletech dose not have any inertial dampeners to hand the recoil like a number of other series.

That said it is possible that battletech dose have some fairly substantial recoil gear, it's possible that a good chunk of the mass of a Gauss rifle is devoted to it. On such example of this counter recoil gear is with the Zeus Heavy Rifle, in the novels it is treated as a 50 cal sniper rifle (as it is in the early RPGs, the later eds. it's more simply a 50 cal rifle), it is listed as firing a 45g slug at hypersonic speeds... Your looking at upwords of real life 30mm range. However it is mentioned that it dose come with counter recoil gear that makes it feel like your firing a 7mm rifle. So their is some evidence that B-tech dose seem to have rather effective counter recoil gear.

All that about recoil would be reasonable if a Gauss Rifle actually pushed the projectile forwards. But that's not how Gauss Rifles work. They use magnetic coils to draw the projectile along the barrel. Recoil could only affect the single magnets, and even then, as we mentioned above, it is possible that this recoil would compensate itself because the magnets are aligned around the barrel, thus the opposing magnets would negate the outward force they produce individually.

[t Khrist]

RedDragon, on 22 June 2015 - 12:25 PM, said:

All that about recoil would be reasonable if a Gauss Rifle actually pushed the projectile forwards. But that's not how Gauss Rifles work. They use magnetic coils to draw the projectile along the barrel. Recoil could only affect the single magnets, and even then, as we mentioned above, it is possible that this recoil would compensate itself because the magnets are aligned around the barrel, thus the opposing magnets would negate the outward force they produce individually.

There is most definitely a recoil. If the magnets are attracting the slug, than the attraction of the slug to the magnet is equal, such force being the recoil. That force is transferred accordingly throughout the magnets, the arms of the mech, the mech, and into the ground. So it would seem that the recoil would be there, but dampened by the sheer mass of the mech, though if the recoil is large enough positioning would start to play a part more-so due to the fact that the shot could knock the mech off-balance.

Think of it as if the slug were a stationary object, if the weapon was discharged then, would the mech not be pushed away from it (obviously at a much slower velocity)?

Edited by t Khrist, 22 June 2015 - 01:46 PM.