E-mag weapons builder

[onetrikpony]

I've had a lot of fun playing with the "Blaster and Laser Design" rules from Pyramid 3-37.

Does anyone have anything equivalent for Electromagnetic slug throwers?

I've tried, and failed, to reverse engineer the gauss guns from UT. I think the issue is hypervelocity air resistance, and I'm ready to admit that I'm just not smart enough to understand what's going to there.

I also failed to come to any conclusions by statistical analysis of the printed weapons...

Any help?

[Ulzgoroth]

I frankly would not start from the assumption that UT gauss guns are based on any sort of good physical model. And if anything would expect them to be ignoring the issues of serious hyper-velocity air resistance because if you run into that your gun probably isn't practical to use in an atmosphere.

[The_Ryujin]

Yeah, the projectile weapons in Ultra-Tech mostly followed the examples set in the basic set which in turn were more rule of thumb then built using a design system.

To give you an idea, The 4mm gauss rifle shoots a 2.7g bullet at around 1,500m/s that should do 8d+1 pi- instead of the 6d+2 pi- listed. I peg range (assuming non-APEP rounds) at 900/5,400.

While not ideal, right now the best you can do is use Douglas's ballistic spreadsheet to get damage and range (note that range figures from his sheet will be different then numbers gurps uses) and for small arms at lest take the square root of the rounds KE in joules divided by 3,000 and multiple it by 7.1lbs or 10.7 if the weapon is a heavy automatic to get the weapons weight. A TL10 C Cell can power 60 3kj shots.

[onetrikpony]

Originally Posted by The_Ryujin

To give you an idea, The 4mm gauss rifle shoots a 2.7g bullet at around 1,500m/s that should do 8d+1 pi- instead of the 6d+2 pi- listed. I peg range (assuming non-APEP rounds) at 900/5,400.

While not ideal, right now the best you can do is use Douglas's ballistic spreadsheet to get damage and range...
...and for small arms at lest take the square root of the rounds KE in joules divided by 3,000 and multiple it by 7.1lbs or 10.7 if the weapon is a heavy automatic to get the weapons weight. A TL10 C Cell can power 60 3kj shots.

Thanks for your post.

Douglas from Gaming Ballistic? I Havn't been able to find that spreadsheet.
Am correct to assume the metrics you're using are from the spreadsheet?
Does this spreadsheet cover hyper velocity shockwave and resistance?

If that's not the case can you help me understand how you arrive at;
900 yd 1/2 damage range for the 4mm rifle?
60 3KG shots / C-cell (I'm guessing the assumption is a 3600KJ rechargeable)?

[Fred Brackin]

Originally Posted by onetrikpony

I've had a lot of fun playing with the "Blaster and Laser Design" rules from Pyramid 3-37.

Does anyone have anything equivalent for Electromagnetic slug throwers?

Any help?

What you need is actually just a system for handling the upper end of conventional guns.

Some reasons why:

Above 1600 meters per second pretty much any projectiles made from anything except but depleted uranium or materials like UT's "bulk amorphous tungsten" shatter and make shallow craters rather than deep penetrating hits.

Above 2200 mps even depleted uranium structurally fails. "Hyperdense might take you farther but how far depends on specifics. Traveller's "Bonded Superdense" at 2x as dense as steel but 14x as strong might take you to 3700 mps.

At about the same speed (Mach 7) projectiles made out of conventional matter start to burn up like meteors in an Earth-like atmopshere.

So really, you don't need to go that far past what you can get with gunpowder. I've heard of rifle rounds that hit 1200 to 1500 mps and tank guns go toa round 1600.

Of course, this is for the projectiles. Stats for the guns are pretty speculative though soemupper limits can be calcualted using material strength math that is well beyond me.

[Varyon]

Originally Posted by onetrikpony

60 3KG shots / C-cell (I'm guessing the assumption is a 3600KJ rechargeable)?

Curious about that myself. The laser rifle in UT is consistent with a 30 kJ weapon in Spaceships (and probably the mentioned design article, but I don't have that to check), and would get 8.3 shots out of a C cell (the D cell it normally uses holds 10x as much energy as a C cell, and gets it 83 shots). 30kJ * 8.3shots/cell = 249kJ/cell, implying that's how much usable energy you get out of it. Assuming electromagnetic weapons have comparable efficiencies to laser weapons, that would mean a 3 kJ* gauss gun (say) should manage around 83 shots out of a C cell. The_Ryujin appears to be assuming the electromagnetic weapon will only have around 70% of the efficiency of the laser weapon.

[onetrikpony]

Originally Posted by Varyon

Curious about that myself. The laser rifle in UT is consistent with a 30 kJ weapon in Spaceships (and probably the mentioned design article, but I don't have that to check), and would get 8.3 shots out of a C cell (the D cell it normally uses holds 10x as much energy as a C cell, and gets it 83 shots). 30kJ * 8.3shots/cell = 249kJ/cell, implying that's how much usable energy you get out of it. Assuming electromagnetic weapons have comparable efficiencies to laser weapons, that would mean a 3 kJ* gauss gun (say) should manage around 83 shots out of a C cell. The_Ryujin appears to be assuming the electromagnetic weapon will only have around 70% of the efficiency of the laser weapon.

I'm assuming the issue is the efficiency of the projector / launcher. I've been thinking about my TL 10 setting in terms of projectile launchers being more efficient in terms of terminal energy than beams. Things would change a lot if that weren't the case.

Originally Posted by Fred Brackin

Above 1600 meters per second pretty much any projectiles made from anything except but depleted uranium or materials like UT's "bulk amorphous tungsten" shatter and make shallow craters rather than deep penetrating hits.

Above 2200 mps even depleted uranium structurally fails. "Hyperdense might take you farther but how far depends on specifics. Traveller's "Bonded Superdense" at 2x as dense as steel but 14x as strong might take you to 3700 mps.

This concept is new to me!
Thanks Fred.
Where do I go to learn more? (even search terms would be OK) I'm guessing it has something to do with a threshold for energy transfer based on the (sheer?) strength of the projectile material?
This could definitely change my setting.

[Varyon]

Originally Posted by onetrikpony

I'm assuming the issue is the efficiency of the projector / launcher. I've been thinking about my TL 10 setting in terms of projectile launchers being more efficient in terms of terminal energy than beams. Things would change a lot if that weren't the case.

The relationship between the energy of a projectile and its GURPS damage isn't as straightforward as that between the energy of a beam weapon and its GURPS damage. The latter is simply the cube root of energy multiplied by a constant (roughly 2d if using energy in kJ, and dealing with most beam weapons like lasers), then rounded appropriately. For a large projectile, the former is roughly the cube root of the projectile's mass multiplied by velocity, multiplied by a factor dependent on the projectile's composition (it's the collision equation from Basic Set). For bullets, there's no official formula, but Douglas Cole's spreadsheet uses this equation to get damage in points (divide by 3.5 to get it in dice): (((KE^1.04)/(X^0.314))^0.5)/13.3926, where KE is kinetic energy (in Joules) and X is the bullet's cross sectional area in square meters. He's got other stuff setup on the spreadsheet to calculate what (if any) armor divisor is appropriate. There are cases (indeed, I think it's generally the case) with that equation where even if a slugthrower isn't as efficient at turning stored energy into kinetic energy as a laser that gets a comparable number of shots, the thrown slug will deal more damage. For example, that 30 kJ laser I mentioned earlier does 6d(2) burn, which is 12 dice of armor penetration. The .50 BMG round in Doug's spreadsheet only has around 17 kJ, yet deals 13d+2 pi+, which is both more penetration and more wounding for less energy.

[Say, it isn't that bad!]

Originally Posted by Varyon

For a large projectile, the former is roughly the cube root of the target's mass multiplied by velocity, multiplied by a factor dependent on the projectile's composition...

You sure about that?

[onetrikpony]

Originally Posted by Varyon

... Douglas Cole's spreadsheet uses this equation to get damage in points (divide by 3.5 to get it in dice): (((KE^1.04)/(X^0.314))^0.5)/13.3926, where KE is kinetic energy (in Joules) and X is the bullet's cross sectional area in square meters...

Thank you for the post and espescially the information. I'd sure like to see that spreadsheet.

Do you know where Ryujin got the weight factor numbers?

Found the spreadsheet; Google. Who knew?!
http://www.motoslave.net/thom/rpgs/

Also found what might be information on the upper limit of velocity for penetration here.
http://aux.ciar.org/ttk/mbt/papers/i...jie_28_363.pdf
which will be awesome to read after I get my injuneering degree.