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[Mjolnir]

You said increasing speed doesnt increase energy, then made a comment about acceleration.

You really should take the time to read what people are actually saying.
He said halving the mass doesn't double the speed and energy. It doubles the acceleration. The assumption is clearly that force and gun length are equal, he's comparing how projectile mass and exit velocity scale relative to each other, which is what you appeared to be talking about.

You arguing with physics then?

In a sense...he's arguing using physics.

Or are you arguing its impossible to make railguns able to project something that fast?
Then I would like to point out small projectiles have been accelerated to over 30kms in real life.

45 km/s, actually, but it took the Z machine at Sandia firing a rather tiny (0.9 mm thick, 25x13 mm) projectile.
http://www.sandia.gov/pulsedpower/prog_ ... -lemke.pdf

It's not a railgun, though it seems somewhat similar. The rails of a railgun are pushed apart during launch, the Z accelerator just replaces the projectile with a short at the end and the rails with lightweight "flyer plates", minus the mechanical support that holds a railgun together. The flyer plates explode outward in opposite directions when it fires. The configuration puts the projectile and fields deep inside the machine, and only a tiny amount of energy expended goes into accelerating the flyer plates...the one-sided experiment that got the 45 km/s number gave the projectile about 700 kJ (assuming a rectangular plate, it's probably lighter and lower-energy than my estimate), out of 12000 kJ input. And there's the little issue with the projectile vaporizing...even with their pulse shaping efforts, the flyer plates apparently must be placed quite close to the target (5 mm) in order to still be partly solid when they hit it.

In any case, firing a projectile of half the mass at even the same energy is a more difficult task, requiring higher peak powers, faster switching of higher currents, etc. They need to impart a very large amount of kinetic energy into the projectile in a very short period of time, and increasing the velocity and decreasing the mass makes that harder...if the projectiles are fast enough to do the job, the speeds they're using may well be optimal for their intended use.

[CptWinters]

Because this is what they're planning for each other right now.

I know; I was trying to be funny. Sadly, I'm no comedian.

[Rosen_Ritter_1]

Then humans are screwed ;P
Since Loroi are superior to humans in everything BUT Social structure and physical strength.
They seem smarter
They have telepathic and telekintic abilities
They require far less food.
They can live on larger extremes of hot or cold worlds
70% female breeding rapidly will result in overpopulation and need to expand.. humans traped in a culdesac will sooner or later get wiped out so the Loroi can populate our worlds.

Humanity is screwed if there is a fundermental shift in Loroi culture.

Pffft! And I thought I was the pessimist. Yes. The Loroi have a bunch of advantage over humans. HOWEVER. The biggest advantage they have over other races they don't have with humans. Namely the ability to mind read and farsee us. Which is a rather significant issue. Plus, nothings written in stone yet. We don't know how things will turn out ultimately. Just possibilities to consider.

[Tash]

Pffft! And I thought I was the pessimist. Yes. The Loroi have a bunch of advantage over humans. HOWEVER. The biggest advantage they have over other races they don't have with humans. Namely the ability to mind read and farsee us. Which is a rather significant issue. Plus, nothings written in stone yet. We don't know how things will turn out ultimately. Just possibilities to consider.

Humans also resemble Loroi. That's a pretty difficult stumbling block in the way of exterminating an entire race, because it's fairly easy to demonise something that doesn't look at all like you.

Also, offtopic, but it is so hard to not begin and end every post with 'sieg kaiser' when replying to you.

[fredgiblet]

Who might not pay much heed to the cultural barriers of communication since they interfere in weapons R&D.

We aren't talking about something that they can just turn off and move on from. The communications issue comes from their BIOLOGY, not from, say, a holy book that can be re-interpreted in a different manner.

They seem smarter

Nope. They have a +1 to Health but no bonus to Intelligence. The one's we've been seeing are just the ones smart enough to survive.

[Mayhem]

It is interesting that there is a common default assumption that Humans or Alex specifically are going to critically impact the war through their own actions or innate talents.

Even I used to wonder how it is that Alex's arrival will can the balance of the war.

More recently I have been considering how the course of the war could be changed others responses to the mere knowledge of Human existence.

For example, if they had not found Alex and the Bellarmine then the strike group would not dream of trying to defend a "fixed" point.

Following on, the presence of an ambassador for a new and unexpected species added to the toll defending said fixed point may mean the strike group withdraw to location Y rather than X changing the forces distribution for subsequent battles.

Or even a squadron is sent to rendezvous with the Prabhu, sending them through space that would otherwise would have been without Loroi presence at that causing them to stumble across the Umiak's secret whatever.

It is the whole pebble triggering an avalanche concept (or the trouser legs of time).
The pebble itself maybe insignificant but the village is still destroyed.

[BattleRaptor]

You really should take the time to read what people are actually saying.
He said halving the mass doesn't double the speed and energy. It doubles the acceleration. The assumption is clearly that force and gun length are equal, he's comparing how projectile mass and exit velocity scale relative to each other, which is what you appeared to be talking about.

*COUGH*
I said

Half the weight double the speed and you still have double the energy.
Pluss double the effective range.

Not
Halve the weight, get double the speed and energy.

No ambiguity in my orginal post.

[osmium]

@BattleRaptor

I am loath to wade into these flame wars (although what passes for them in this forum isn't nearly as free wrangling as might appear in other corners of the internet), however in this case I feel I need to add more information.

1) if you correct yourself in further posts it may be useful (especially in threads that are fast moving or contain multiple unrelated conversations [such as this one]) to make note of that if you are going to re-reference it in further posts.

2) Relevant equations from physics to clear up any misunderstandings / misconceptions

F = ma. (statement half mass -> 2X speed and still have 2X energy(unclear what the wording meant seems to imply 2X energy in the projectile) [obviously paraphrased]
so 1/2 mass directly equals 2X acceleration assuming constant force. (yay physics)

KE = 1/2mV^2
unclear here, but if you actually do get 2x velocity you would instead get 4X the kinetic energy (you corrected yourself / correctly stated this in a further post)

Now the force is significantly more complicated the simplest bit is the Lorentz force, which obviously needs to be integrated (in some manner) over the mass density function of the projectile with respect to position (resulting in a much more complicated equation)

F = q[E+(B x v)]

F is the force, E is the electric field, B is the magnetic field, q is the electric charge of the particle, v is the velocity of the particle, inside () is a cross product

Obviously this brings up variables for all of those things mjolnir was talking about. What is the resistance as a function of the variables that change (such as temperature of the conductor, voltage? etc) for the conductors used for the rails (or materials for the coils if it's a gauss rifle.) How are you generating the B field, with electromagnets(likely) or with permanent magnets, or maybe with something like a peizo electric where you can generate a permanent magnetic field by straining the crystal... Suffice to say you need to take into account the differences in the requirements electromagnetism places on the gun's systems in order to maintain that same applied force (And thus actually double acceleration).

it is *also* worthwhile to point out that:

s = .5at^2 + v0t +s0
is relevant as it is where the barrel length comes into play as accelerating fast does indeed reduce the time it takes to reach the end of the barrel. Although a gun that fires a smaller projectile faster might indeed have a longer barrel length to help counteract that effect (and reduce the strain and losses that mjolnir mentioned might play a significant part in attaining adequate values for the state required to attain the doubled acceleration we have been talking about this whole time)

Just for further complication, every individual material that takes part in this process has unique limitations (or advantages) but there is no magic bullet, every part needs to be made of something and oftentimes when you take thought exercises like the one we've been arguing about you may very well run afoul of some such limitation.

Finally, having seen your further posts there appears to have either been ambiguity or errors in the original post, it is unclear to me which occurred.

There was certainly ambiguity in my terse post. Acceleration wasn't clear if it meant in the barrel, or if I was assuming some sort of torpedo. I think it was mostly clear what I was saying, but especially if someone doesn't speak english as their first language (of which there are a number of people in this forum in said category) it is sometimes unclear why they might misunderstand (even if you do actually think you're being incredibly clear) so it is usually most useful to just assume you made some minor mistake and go from there rather than defending the Alamo to the last man.

-O

[BattleRaptor]

I corrected my post yesterday and NOT today, no one had posted in response to it either.
What I corrected, was when I posted I was tired and said the Projectile had 4* the energy not 2* when it had half the mass.
Post was besides that and me stating I edited it, was left untouched.

You do not get quadruple the energy if the projectile is HALF the bloody weight at double the speed.
You get Quadruple the energy if its double the speed with no change in mass.

The ENTIRE point was you can have a railgun fire a lighter projectile at greater effectiveness.
The Shear size of the Terran Projectiles dont make sense.

Not only can you increase effectiveness with a smaller projectile.
This incidently increases effective range, increases ammo stores.

AT least this thread is entertaining.

People assume the same railgun is used for diffrent projectiles....
and then attempt to argue why a railgun wouldnt project a 100kg slug at double the speed of a 200kg slug.
While NOT pointing out why its totaly impossible if its the same railgun used for the 200kg slug.
IT simply requires more energy then the railgun can output.....

*CRICKETS IN THE BACKGROUND AS AWARENESS DAWNS*
I think its best if I just COMPLETELY ignore specific persons posts from this point on.

[Rosen_Ritter_1]

Humans also resemble Loroi. That's a pretty difficult stumbling block in the way of exterminating an entire race, because it's fairly easy to demonise something that doesn't look at all like you.

That, and the fact that allot of internal members of the Loroi Union would consider an unprovoked attacked against humanity as being VERY suspicious in Loroi motivations. The Barsam and the Historians are already aware of the implications behind humanities existance, so that at least gives humanity some friends within the Union. They might not officially be in charge but the Loroi can't entirely discard them completely.

Also, offtopic, but it is so hard to not begin and end every post with 'sieg kaiser' when replying to you.

Such topics are highly upsetting to Rosen Ritter when they hear it.


It drives them to do very unpleasant things.

We aren't talking about something that they can just turn off and move on from. The communications issue comes from their BIOLOGY, not from, say, a holy book that can be re-interpreted in a different manner.

No. The technical flow of information isn't an entirely biological issue. It's a social one. Loroi telepathy in fact makes them HIGHLY effective at transferring information to one another. It's just that the insular nature of the various castes often dissuades idea's from being transmitted. This is not a biological feature.

[BattleRaptor]

The loroi effectively cant lie to each other..
So the propaganda that human Civilization is full of wouldnt work for the Loroi.

Dont think its possible for the Loroi govement to hide anything from the masses without locking up and throwing away the key for everyone who know what needs to be hidden, and then the people that know people were hidden.. and so on.

Be intresting to know if Loroi even have what we would call spies.

[Mjolnir]

Half the weight double the speed and you still have double the energy.
Pluss double the effective range.

Not
Halve the weight, get double the speed and energy.

No ambiguity in my orginal post.

Some ambiguity there, certainly more than in fredgiblet's response. He made the obvious assumption that you were talking about weapons that were in some way comparable.

I corrected my post yesterday and NOT today, no one had posted in response to it either.
What I corrected, was when I posted I was tired and said the Projectile had 4* the energy not 2* when it had half the mass.
Post was besides that and me stating I edited it, was left untouched.

You do not get quadruple the energy if the projectile is HALF the bloody weight at double the speed.
You get Quadruple the energy if its double the speed with no change in mass.

The ENTIRE point was you can have a railgun fire a lighter projectile at greater effectiveness.
The Shear size of the Terran Projectiles dont make sense.

Not only can you increase effectiveness with a smaller projectile.
This incidently increases effective range, increases ammo stores.

Being able to build and deploy a given gun does not imply the capability to build one that fires projectiles of half the mass at double the velocity. Simply reducing projectile mass may increase velocity and specific energy per unit of projectile mass, but will decrease overall projectile energy. Assuming you can maintain the same force on the half-mass projectile, velocity scales as sqrt(a*D*2)...double the acceleration, you increase velocity by sqrt(2) and double the specific kinetic energy...equal projectile energy, all else being equal. It's not equal, though, you're applying that energy to a smaller projectile over a shorter period of time, and your losses will be higher...reducing overall projectile energy for the same energy input.

The Terrans may simply have a need to maximize projectile energy instead of projectile velocity. And as I mentioned, it makes even more sense if the projectiles aren't entirely dumb, but have some degree of propulsion for trajectory tuning/guidance...this could compensate a great deal for lower projectile velocities. In fact, given that their mass drivers likely aren't 100% accurate, larger, slower projectiles that can correct minor trajectory errors may be required in order to achieve hits at long ranges with any reliability.

[Mjolnir]

No. The technical flow of information isn't an entirely biological issue. It's a social one. Loroi telepathy in fact makes them HIGHLY effective at transferring information to one another. It's just that the insular nature of the various castes often dissuades idea's from being transmitted. This is not a biological feature.

That effectiveness of telepathy is also part of the problem. Written language has some major advantages in preserving and disseminating knowledge, but they find telepathic communication with someone who's memorized the information to be far preferable. Their culture is what it is because of their biology.

They're not biologically limited, though. With the demands of the war, requirements for communication with alien species, and the limited supply of Listel, perhaps there's an increasing acceptance of written language.

[icekatze]

hi hi

I can think of a few explanations for the super-sized nature of the Mjolnir Cannon, most of them are based on what the target of the weapon is. Below are some thoughts on the matter.

• Human vs human/ship to ship combat does not seem to be the purpose of the weapon. Nobody else but the TCA seems to have any warships, and the lasers/torpedos should be enough to handle rogue freighters, should that ever become a problem.

• Muzzle velocity and impact velocity are not going to be the same thing in space combat, especially not in a joust. (This is a big one)

• Possible use: Nudging asteroids?

• Possible use: Orbital Bombardment? If I am not mistaken, the larger mass would mean better penetration in an atmosphere. If a colony is stepping out of line, it would be a powerful psychological deterrent. But it also means that they cannot use it for surgical strikes, this may be a selling point, as people may be less likely to use weapons of mass destruction.

• Terrans know the Umiak/Loroi are big but we don't really have a clue as to how big, so they built this big gun in the hopes that it might be impressive even though Alex now knows that it isn't.

[fredgiblet]

*CRICKETS IN THE BACKGROUND AS AWARENESS DAWNS*

Since you haven't been very clear so far so I'll ask for clarification, are you talking about an ENTIRELY DIFFERENT mass driver? If not then my and Mjolnir's posts still stand. If yes then you still run into the issues with actually building such a weapon since it's power usage will be significantly higher (and it's efficiency notably lower) than the original weapon, but in that case it's plausible.

No. The technical flow of information isn't an entirely biological issue. It's a social one. Loroi telepathy in fact makes them HIGHLY effective at transferring information to one another. It's just that the insular nature of the various castes often dissuades idea's from being transmitted. This is not a biological feature.

Where do you think that insular nature comes from? Telepathy. Telepathy lets you into the very mind of the person you are communicating with, it's not something that you're going to want to share with every random stranger that you come across, hence an insular nature.

Terrans know the Umiak/Loroi are big but we don't really have a clue as to how big, so they built this big gun in the hopes that it might be impressive even though Alex now knows that it isn't.

Nah, those guns existed long before the Orgus showed up. My guess is that they are that large due to the guidance systems.

[Mjolnir]

Nah, those guns existed long before the Orgus showed up. My guess is that they are that large due to the guidance systems.

They may also serve as probe launchers. From orbit at the distances typical of jump zones, that delta-v would be more than enough to reach everything in our solar system. Being able to launch ballistic probes on flybys of every body of note in a system would be useful for surveying a new system. Being able to vaporize a chunk of an asteroid or planetary surface would have similar uses for judging mineral resources. It might be that they exist primarily as a tool and only secondarily as a defense against potential hostiles.

[dfacto]

Since you haven't been very clear so far so I'll ask for clarification, are you talking about an ENTIRELY DIFFERENT mass driver? If not then my and Mjolnir's posts still stand. If yes then you still run into the issues with actually building such a weapon since it's power usage will be significantly higher (and it's efficiency notably lower) than the original weapon, but in that case it's plausible.

Wait, I have to ask why though.
http://www.csgnetwork.com/kineticenergycalc.html

200kg projectile, 6000m/s = 3.6 GigaJoules
100Kg projectile, 3.6 GJ = ~8500 m/s

Seems to me that reducing the size of the projectile by half while maintaining the same kinetic energy would hardly present an insurmountable technical challenge, plus you would have a faster muzzle velocity. Honestly I'd be surprised as hell if we couldn't achieve higher speed and KE in 150 years considering where we are today (and we're at the very cusp of EM launcher technology)

But aside from that, yeah, it does seem reasonable that the main usage of the guns is utility and bombardment rather than ship to ship combat. Maybe they need the big guns for intimidating colonies?

[fredgiblet]

Wait, I have to ask why though.

8500 m/s is about what they would get out of cutting mass in half if efficiency stayed the same but it wouldn't since they're trying to pump a round out much faster out of an already extremely high-performance device. Specific numbers are impossible to guess because we don't have the actual devices (or anything in remotely the same class) but efficiency will drop and that will require more power, probably significantly more.

[dfacto]

Yes, but on the other hand you have a lighter round with less inertia, which means it needs less energy to accelerate it compared to the larger round. I'm thinking the situation isn't as bad as you make it out to be. Probably doable, just no benefit to it.

[Mjolnir]

Yes, but on the other hand you have a lighter round with less inertia, which means it needs less energy to accelerate it compared to the larger round. I'm thinking the situation isn't as bad as you make it out to be. Probably doable, just no benefit to it.

It doesn't work that way. With equal efficiency and projectile energy, you need to put exactly the same amount of energy in, regardless of the mass of the projectile.

You have to put a given amount of energy into the projectile to do damage, and that is easier to do efficiently with larger, slower projectiles. A lighter projectile is easier to accelerate to the same velocity, but that's not enough...it must be accelerated to a higher velocity to achieve the same projectile energy. You need either a longer gun that may not fit in the ship and can have other scaling issues, or a briefer pulse of higher power, which means higher losses.

edit: an illustration of two extremes of our current capabilities...we can accelerate a roughly 700 mg projectile to 45 km/s, giving it 700 kJ (the Sandia experiments using the Z machine), or we can accelerate a >20 tonne mass to ~100 m/s, maxing out at 122 MJ (the EMALS electromagnetic aircraft catapult), a couple orders of magnitude more energy...and a reusable launch apparatus. In between, there's the railguns the US Navy is developing, planned to scale up to 64 MJ and 5.8 km/s, with 3-4 kg projectiles. Their current record is 33 MJ, apparently with a 10.4 kg 2.5 km/s shot.