187 replies to this topic

[Karl Streiger]

Artifice, on 18 September 2013 - 04:33 AM, said:

The physics seem a little silly at times. I don't know the newest version, but the old Gauss rifles had a minimum range - makes no sense.

Well a minimum range makes some sense:
for example. you need a APFSDS for your gauss (while it is some what silly to use such a projectile for a gauss it is possible)
- but because you need ferro magnetic material to accelerate the bullet - your sabot is made of nickel or iron while the arrow uses tungsten carbide or depledet uranium: that means: at minimum range - the energy of impact hits a square of ~ 20cm² while after the sabot is discarded nearly the same energy hits only a square of 25% of that size

[Pht]

Karl Streiger, on 17 September 2013 - 11:16 PM, said:

So it is a kind of electro thermal cannon?
Instead of firing a projectile it fires compressed air?

Sorry but i would stay near actual physics like the NERVA or RAM jet - both need fuel and in case of the fusion engine its the deuterium or hydrogen that is the fuel of the fusion engine

It doesn't fire compressed air. it fire plasma. This is exactly how the technical description in the setting has it - it takes in local atmosphere via turbo compressors; than hits that compressed atmosphere with an electrical arc, converting the compressed atmosphere into an explosion of plasma. Said plasma explosion is than let out of the jump jet in a controlled manner providing lift.

I can quote you the direct text with it's reference, if you'd like.

[Elyam]

That's interesting...means they changed the original Jump Jet description slightly. Original held that the intaken air was compressed and circulated around the outside of the fusion core thus causing it to super-heat and eject as steam. There never was at that time a mention of arc ignition. It was also held that a small reserve of mercury was kept on all JJ-equipped mechs to be fuel for the jets when in space or an otherwise incompatible atmospheric situation. In some cases the mercury was even described as always an ingredient in small amounts during normal atmospheric use. You'll find several text passages in novels describing a jetting mech 'rising on a column of mercury steam'.

And to reiterate since there has been so much misinformation on this - no, reactor plasma itself has never been the jet or rocket fuel of the jump jet system.

Edited by Elyam, 18 September 2013 - 02:59 PM.

[Space Odin]

How come mechs with legs cant walk over a rock/streelamp/car/hill less than 1/5 their height?

[Void Angel]

DavidHurricane, on 15 September 2013 - 06:18 AM, said:

Other than the fact that some Mechs way 95 tons and mount them. But what does a fusion reactor do with the plasma for power?

I'm very sure that the problem isn't generating enough thrust from a fictional reactor to lift a 90 ton war machine high into the air - but the fact that said war machine doesn't shake itself apart landing - or falling down, or running at 60KPH, or supporting its own weight under gravity...

The structural strength of the required materials is far beyond what the Battletech flavor text says is used for 'mech construction, and there is actually no way at all for a war machine with multiple articulated joints to be tougher than a tank built from the same tech - but that's not fun, so we all just blissfully ignore it. =)

[dal10]

Void Angel, on 18 September 2013 - 05:01 PM, said:

I'm very sure that the problem isn't generating enough thrust from a fictional reactor to lift a 90 ton war machine high into the air - but the fact that said war machine doesn't shake itself apart landing - or falling down, or running at 60KPH, or supporting its own weight under gravity...

The structural strength of the required materials is far beyond what the Battletech flavor text says is used for 'mech construction, and there is actually no way at all for a war machine with multiple articulated joints to be tougher than a tank built from the same tech - but that's not fun, so we all just blissfully ignore it. =)

the one thing i will give battlemechs is that they could be a much more efficient weapons platform. lot more room to mount weapons. cause their are only so many things you can stack on a turret. let alone have room for ammo.

[Karl Streiger]

Pht, on 18 September 2013 - 02:32 PM, said:

I can quote you the direct text with it's reference, if you'd like.

Thanks in advance - but I believe you mean the part of this essay
http://www.sarna.net...ology#Jump_Jets

Its excellent and spares me mostly a lot of time searching in all my rule books and compendiums for the "right" look n feel.

However - we are talking about physics? And while BT has references to Hard Sic-Fi its more a kind of sicfantasy or a spaceopera mecha verse.

I don't want to bother with the full equotations of physical laws.
But for JumpJets - a 90t Highlander with 3 JJs can jump up to 18m height - that means the work of the jumpjets have to counter gravity:
at Terra - it means all thos 3 JJs have to put out 15.892.200 MJ - with the efficency of 40% at best the plasma need an energy of ~ 40 MJ - so the energy that ignites the compressed air have to deliver 80 MJ - at we are just talking about a straight jump in the air. Not to mention the other 25 MJ of the plasma that stresses the JumpJets....
the funny part is however: that a 45t Mech jumping 36m height (Phoenix Hawk) need the same energy but the JJs weight only 3tons in addition over the 6tons for the highlander.
It make sense from a game balancing point of view - not from physics - or logic...like so many other things you mentioned in your essay.
BattleTech has started as a game - and the worst mistake was to bound the lore to the mechanics of the game.

Space Odin, on 18 September 2013 - 04:31 PM, said:

How come mechs with legs cant walk over a rock/streelamp/car/hill less than 1/5 their height?

That is also a funny part - founded in the start as a game:

To start with i ask you to imagine fourth persons: all are 400m sprinters


Than you add a short range were your are measuring the time they need to travel 100m
but at this point the first is allready running for 10sec - moving allready at topspeed
the second has just started and is accelerating
and the third start when you are beginning the measurement.
The fourth has uneven ground and has to climb over some small obstacles

So the average speed of the sprinters should be obviously clear:
1 > 2 > 3 > 4
although there top speed is equal.

Same happens in TT - topspeed of a Atlas is 15m/s or 5 hex... it doesn't matter if he starts from standing, from walking or from running...after that round all three will arrive at the same hex - moving with topspeed?
Does that make sense? No it doesn't.

I believe a Atlas can run at much higher topseed far above 15m/s...but the problem is the acceleration - take for example a car...what need more time - climbing a hill from v0 of 0 or allready moving with 100mps?

But MWO only had the TT values measured in top speed of 15m/s.... and because it is bound to the lore...its a rule...

[SchwarzerPeter]

Well usually future tech in such a setting is the same as magic. Its explains the cheese bit physics can't.

Jump jets that takes no fuel (compress atmosphere and superheat them to plasma) that can lift a 90t mech? Its kinda ridiculous in terms of energy consumption, but why not? We got a super high efficiency fusion reactor there anyway.

Oh and the whole walking tank thing - wouldn't a hovering spaceship be far more efficient in terms of mobility range an speed? Not to mention that normal tanks would be a far durable weapon platform than a mech.
Yes i love these walking tanks, but they don't have a significant advantage against normal tanks. Ok maybe in a city when they climb over houses and so on (but they will most likely collapse).

And the short range of the weapons. LRM with a max range of 1km? Its makes sense in terms of game balance, but from physics?

Edited by SchwarzerPeter, 19 September 2013 - 12:03 AM.

[Karl Streiger]

Right a hovering dropship would be more devastating...and i believe some of them are more devastating - for example an Assault Triumph has the same firepower of 3 or 4 assault mechs while moving at much more speed Next to that it is much better armored - but on the opposite is a big target - simpler to hit.

I don't know if it make some sense: but the best advantage of an BattleMech would be its mobility - that isn't perfectly reflected in TT terms - when compared to tanks.
A next advantage could be the "reduced" damage of a penetrating hit. Like a AP-round can travel through a human without causing significant damage - a penetrating rod of a gauss or rail gun may move through the torso of a Mech without damaging important internal components - while the same hit may stun or disable a tank crew.

The range of weapons - should be baned from lore - really best thing to do is to replace the range of a hex from 30m to 300m.
Although you still could read the "to hit" chance in another way:

for example the Shilouete Core rules of Heavy Gear - here is the damage as well as the to hit roll combined into a single one.
That means - a missed shot could still mean you hit the target but didn't caused damage.

The ablative armor of BT is another thing you need some thoughts about - I've read some where that todays composite armor is able to stop kinetic penetrators but is damaged when the plate is hit...so even light weapon weaken the structure of that ceramic armor - so they have layers of a more flexible material like to take the shockwaves of the impact to reduce the damage to the plate when taking minor damage.... so in terms of BT - even todays MBT have a kind of ablativ armor....but I don't know if there was ever a "field" test to penetrate the frontal glacier or side armor of a MBT with low caliber weapons (25-40mm)

[990Dreams]

SchwarzerPeter, on 19 September 2013 - 12:02 AM, said:

Well usually future tech in such a setting is the same as magic. Its explains the cheese bit physics can't.

Jump jets that takes no fuel (compress atmosphere and superheat them to plasma) that can lift a 90t mech? Its kinda ridiculous in terms of energy consumption, but why not? We got a super high efficiency fusion reactor there anyway.

Oh and the whole walking tank thing - wouldn't a hovering spaceship be far more efficient in terms of mobility range an speed? Not to mention that normal tanks would be a far durable weapon platform than a mech.
Yes i love these walking tanks, but they don't have a significant advantage against normal tanks. Ok maybe in a city when they climb over houses and so on (but they will most likely collapse).

And the short range of the weapons. LRM with a max range of 1km? Its makes sense in terms of game balance, but from physics?

Mini-propulsion systems could propel a projectile far further than 1km in principle. And as for a fusion reactor just inject carbon into a pure hydrogen mix and get super energy output. But Sarna says that is is not deuterium or tritium. Just to clarify.

[990Dreams]

Space Odin, on 18 September 2013 - 04:31 PM, said:

How come mechs with legs cant walk over a rock/streelamp/car/hill less than 1/5 their height?

The pneumatic/hydro/electric actuators don't allow it to move it's legs THAT high.

[CyclonerM]

Mmmh i never read in the novels about "mercury steams"..

[990Dreams]

CyclonerM, on 19 September 2013 - 10:08 AM, said:

Mmmh i never read in the novels about "mercury steams"..

Wut?

[Void Angel]

dal10, on 18 September 2013 - 05:21 PM, said:

the one thing i will give battlemechs is that they could be a much more efficient weapons platform. lot more room to mount weapons. cause their are only so many things you can stack on a turret. let alone have room for ammo.

Actually the tank would have an easier time fitting weapons into the chassis, since its main weapons could be housed in a single compartment. The armor coverage would also be more effective per ton, since you're wasting less armor on things like arms and legs.

Essentially, on any armored fighting platform, you have unavoidable weak points in your armor - sensors, exhaust ports, weapons, etc, all have to protrude through the armor somehow. Additionally, if a weapon system needs to be able to turn, that necessitates a seam in the armor wherever the two mated parts join up. A tank minimizes these weak points, but a humanoid walking robot adds more for every point of articulation - elbows, feet, shoulders, neck, hips, waist, hands, fingers... Every single place where a 'mech has two moving body segments, there's a corresponding weak point in the armor. So as a weapons platform, a tank wins over a walking robot in both flexibility and firepower.

Now, a humanoid chassis does allow you more flexibility - but not as a tank. A walking robot on a combined-arms battlefield would fulfill the role of Infantry, not a super-tank - but then we'd be playingHeavy Gear. Which is an excellent game in its own right, but it's not BattleTech. In the end, giant stompy robots who are king of the battlefield is what MechWarrior/Battletech's brand of fun is all about.

[CyclonerM]

DavidHurricane, on 19 September 2013 - 10:30 AM, said:

Wut?

Elyam, on 18 September 2013 - 02:55 PM, said:

You'll find several text passages in novels describing a jetting mech 'rising on a column of mercury steam'.

Void Angel, on 19 September 2013 - 11:17 AM, said:

So as a weapons platform, a tank wins over a walking robot in both flexibility and firepower.

'Mechs still have a mobility advantage compared to tracked or wheeled vehicles

[Elyam]

CyclonerM, on 19 September 2013 - 10:08 AM, said:

Mmmh i never read in the novels about "mercury steams"..

I don't have time to go find it, but it's there between one and 3 times used in one or more of the first 10 novels, probably in the Warrior series but I can't pin it there for certain. But the description is accurate.

edit: a quick search found a reference in William H. Keith's 'Decision at Thunder Rift'

"The Mech jumped, vaulting skyward with magical grace on flaring jets of superheated mercury steam. Grayson saw it twist in midair, swinging its laser down to ..."

Edited by Elyam, 19 September 2013 - 03:14 PM.

[Void Angel]

CyclonerM, on 19 September 2013 - 11:44 AM, said:

'Mechs still have a mobility advantage compared to tracked or wheeled vehicles

You kinda took that out of context. We were talking about the flexibility of weapon mounts, not maneuverability. However, on that note, a tank is just as capable of jumping on flaring jets of mercury steam from its fantasy fusion reactor - and while a humanoid robot would be better able to traverse difficult terrain, the tank (particularly a hovertank) would be far faster on open ground (particularly improved roads.) So the tank is faster and carries more firepower, while the humanoid robot is less well-armed, but able to get places the tank can't - and we're back to an infantry role. Which is fine, and Heavy Gear did that really well (in the video games, at least.) But BattleTech says "screw that! Giant stompy robots are so much more fun as a super-tank!" And since they're both science fantasy, that's ok.

[Pht]

Void Angel, on 19 September 2013 - 09:12 PM, said:

You kinda took that out of context. We were talking about the flexibility of weapon mounts, not maneuverability.

Mechs ARE more manuverable.

Notice that they can traverse terrain types that are forbidden to tanks and almost every other unit type.

[Pht]

Karl Streiger, on 18 September 2013 - 11:34 PM, said:

Thanks in advance - but I believe you mean the part of this essay
http://www.sarna.net...ology#Jump_Jets

Uh ... no, I meant the actual language straight from the techmanual source on the topic that the linked article gets it's information from.

Quote

Its excellent and spares me mostly a lot of time searching in all my rule books and compendiums for the "right" look n feel.

I haven't updated the sarna version lately - the info in it is still right, but the current version is a bit better - it's in the off topic forum here, pinned at the top.

Quote

I don't want to bother with the full equotations of physical laws.
But for JumpJets - a 90t Highlander with 3 JJs can jump up to 18m height - that means the work of the jumpjets have to counter gravity:
at Terra - it means all thos 3 JJs have to put out 15.892.200 MJ - with the efficency of 40% at best the plasma need an energy of ~ 40 MJ - so the energy that ignites the compressed air have to deliver 80 MJ - at we are just talking about a straight jump in the air. Not to mention the other 25 MJ of the plasma that stresses the JumpJets....
the funny part is however: that a 45t Mech jumping 36m height (Phoenix Hawk) need the same energy but the JJs weight only 3tons in addition over the 6tons for the highlander.
It make sense from a game balancing point of view - not from physics - or logic...like so many other things you mentioned in your essay.

The PH jjs don't put out the energy at the same rate. You have to account for how much energy has to be put out at any given time. They only put out an equal TOTAL energy amount because the jump is longer.

Quote

BattleTech has started as a game - and the worst mistake was to bound the lore to the mechanics of the game.

"Real life" physics is just as much a house of cards... but that's a discussion for elsewhere and maybe even another forum altogether.

Edited by Pht, 20 September 2013 - 03:36 PM.

[Solis Obscuri]

All Battletech physics are the effect of chronometric dilithium antimatter particles piped through the tachyon emitter array between the Jeffries tubes in the starboard warp nacelle and the plasma conduit located behind the helmsman's station.

Exactly the same as Star Trek physics.

That's all you need to know.