October 9, 2015

Ballistic's ballistic equations

I promise I'll let this go at some point. But not today.

In my little mishap from this past Tuesday, I estimate that I got tossed about 6-8 feet. 

Well. That's enough to calculate a trajectory!

If we assume that I was launched at the most effective and efficient launch angle of 45 degrees for simplicity, that means that my initial velocity imparted by the explosion was something like 4.3m/s.

If we treat the Gaming Ballistic author as a spherical frictionless brainless cow massing 81 kg, we can see that the blast imparted to me roughly 350 kg-m/s of momentum and 750J of energy. That's about the same energy as in a 10mmAuto, for comparison, but far more momentum.

Let's assume that the combustion/explosion took place over a roughly 0.005 second period (5 milliseconds). That seems to be on the order of what some brief searching shows is on the upper end of how long it takes for the fuel-air mixture in an automobile cylinder to combust.

If that's the case, it means that since Impulse = Momentum (F x delta t) = MV, that I was thrown with roughly 70,000 N of force! Roughly seven tons.

Is that reasonable? If half my body was exposed to the blast, that's about 0.8 square meters. So a pressure requirement of 70,000N per 0.8 square meters, or 87,500 Pascals - 0.85 atmospheres.

According to the Wiki page on blast overpressure, 85 kPa is more than enough to cause severe heart and lung damage, and rip off limbs. Since that didn't happen, my estimate is off somewhere. 

I suspect that the real problem is my estimation of initial velocity, since my mass is what it is. But I did travel that far (I measured!), so we'll leave it as is.

It could also be that the velocity was fine, but if the overpressure effect lasted for much longer than 5ms. The force would drop by at least an order of magnitude, and the overpressure is lower and more in the "not turned to instant pulp" zone. Since I'm sitting here typing, that seems much more reasonable, and a discussion here of typical results and levels of overpressure suggest that since my house did not suffer any major damage (nor did I, really), that I was probably subjected to 0.04 to 0.4 psi of overpressure - let's assume 0.3, giving me more credit for robustness and getting lucky a bit.

So that's more like 2.1kPa rather than a ridiculous 87kPa. That implies about 1700N of force, which is about a 200ms pressure wave duration.

I don't know if it's real or valid, but that's what the math suggests!

Edit: My wife thinks she's funny (she's right)

  • She complained that I hadn't replaced the drawing of the circle with a little stick figure going "aaaaahhhhh!"
  • Also, today when she was helping me get dressed, she says "Hmm. What should you wear? How about a T-shirt?" And she tosses me this one -->

October 8, 2015

Darwin Award Runner Up - Gaming Ballistic goes Ballistic

So, things got interesting this past Tuesday after I threw down my last post about ST and HP and whatnot.

I was doing some yard work in the backyard, removing a large cluster of thorny plants. My intent was to kill them permanently by burning them down at the root. The only fuel on hand I had was gasoline, and since I'd seen gas fires before, I didn't think much of it.

Well, I coated the pile of plants and the roots with what I thought was a properly sparse amount of gas. Alas, the fuel must have vaporized and concentrated under my deck, so when I went to touch off the fuel, it exploded rather than burning. 

My two children were both outside, but are fine. I got thrown to the air for 6-8 feet and landed in the grass. I did manage to break my heel, but that is seemingly the only ill effect. Well, my butt is a little sore from landing, as is my neck. I landed two yards away (so 8 points of concussion damage, with double knockback, if you're playing GURPS). I think the damage to my heel was caused by the deck, rather than the landing. I'm not sure. When the explosion occurred, I only realized it when I was able to orient myself - which happened while I was still airborne. 

After the landing, I examined my kids from a distance, and seeing they were fine, examined myself. No gross trauma, no obvious burns, but my left lower leg made horrible popping and settling noises when I moved my (sore) ankle. My wife got my 6yo daughter calmed down, and then saw to my 16month old. My eldest helped me with a two-sided splint. I used a dowel rod, a left-over garden stake, and my leather belt. Long stake underneath the long bone to the arch of the foot for lifting support, and the dowel on top, running along the top of the arch. Wound the belt around both - it kept it nicely immobile. The ER doctor would later express some admiration at my handiwork under pressure. Go me?

Net/net, the X-rays show a broken heel, but the tibia, fibia, ankle bones, and the rest of the foot bones are all fine. No burns, no impaling injuries, no singed eyebrows even, and I didn't inhale flaming gasoline.

So the only real impact was the heel. Plus vastly accelerating our plans to replace our deck with something new. Demolition started early, I guess. The explosion drew out all my neighbors (some said they saw the fireball) and the concussion knocked a tile off the inside of our fireplace.

Game Related Stats!

  • I had a fuel-air explosive going on.
  • It threw a ST 10-11 person 2 yards through the air
  • Probably counted as a tamped charge
  • I definitely crippled my lower left foot in the blast. That's 2-3 HP right there.

If it's 8 points per yard of flight, so to speak, then I needed 16 points of knockback damage. Since I'm not dead, I figure this sort of blast had double knockback, which means about 4 HP of rolled damage.

This reinforces my thought about needing a HT roll to shrug off injury from crushing/concussive damage.

Parting Shot

A few final notes:

  • I got lucky. Really lucky. I could have easily been killed. I get that: Darwin Award Runner up T-Shirt has probably already been ordered by my relieved but sarcastic family
  • Kerosene rather than gas for burning things off. Flash point is a real thing.
  • My wife will not let me near the BBQ for a least two or three seasons. I do not blame her for this.
  • When Katy Perry sings about becoming a firework and shooting across the sky? She definitely did not think that the entire way through. Although technically I was a krowerif.[1]
  • With no small amount of irony, the author of Gaming Ballistic became a ballistic object himself. Go ahead and laugh. I do.

[1] That's a firework backwards. Because the colors burst, I shot across the sky, and made me go Ow Ow Ow!

What? Not funny? It was funny as hell while I was still on Percoset. Fortunately, the need for that has abated. I'm making do with ibuprophen now, and not much of that either. My splint was replaced with a cast until the swelling goes down. Probably two weeks.

October 6, 2015

Rescaling GURPS HP - some car thoughts

As as was driving in to work, I was thinking about the relationship between ST, HP, and damage. One of the potential solutions people have talked about to bring fisticuff damage, especially swing damage, in line with firearms has been to double HP and DR scores, add a (2) to all pi damage, and call it a day.

My post today is not about that. 

It's really just a realization that one of the impacts of having reasonable HP and mass relationships is that doubling the HP that a character has very, very much widens the range of HP scores that are game-relevant. 

If you look at most humanoids in most games (not all games, and not all humanoids, of course. This is GURPS) they'll tend to run from the 80-400 lb range. 

Female champion gymnasts run from about 80-125 lbs. Pro jockeys tend to be in the 100-120 lb. range. So on the low end, that's not bad. 

William Perry, Adventurer at Large
Andre the Giant clocked in at 500-650 lbs, depending on the source. So there's an argument for going even higher.

William "The Refrigerator" Perry, an American Pro Football player, was 335-385 lbs, but could dunk a basketball and ran a 100-yd dash in about 11 sec (Sprint Move 9, or regular Move 7.5). This is more in line with a "professional" GURPS adventurer.

At the normal scale, the gymnast is going to be a low of 9HP high of 10HP. Jockeys will all fall in the 10HP range. Most men in the 150-200lbs range are all 11 HP. The Refrigerator is 14 HP. Andre clocks in at 16 or 17.

Parting Shot

Doubling the HP totals means your low end gymnast is 17 HP, but the high end is 20HP. Jockeys are still all going to be 20HP (more or less), but from 90-150 lbs (for example) you now get HP from 18 to 21, and in the adventuring range doubles (as expected).

I like that this carries with it the potential for more differentiation in a lot of things. Characters are the heart of the game, and from a "what makes for a sensible HP number for various folks" perspective, having a wider range of useful values is good.

From a damage and DR perspective, now we have the identity 20d(2) = DR 140 = penetration of one inch of RHA steel instead of 20d = DR70 = penetration of one inch of RHA steel. That keeps all of the armor and gun damage in the game where it should be.

It would provide more differentiation using The Deadly Spring for bows, too, so that you don't have to get crazy-town increases in draw weight to increase bow penetration by a point (assuming you don't also give arrows pi damage, which I would not), since the resolution is higher.

This isn't something I'd just go do if I started a game tomorrow. But I couldn't help notice that the increased resolution when translating weight (and Basic Lift, a topic of recent interest) to HP was pretty friendly.

The Lorica Project - Sample Instructions

I just spent far too long writing up instructions. I will try and paste them into this post, but I will also upload the file.

The Word 2013 File.

The PPT file with my diagrams

The actual PDF I found with a Newstead Pattern harness

This may get ugly. I'm not going to take a lot of time to edit it, though. Be warned: after the break, here there be dragons. (alas, the pictures did not come in - please take a look at the files themselves).

October 4, 2015

Orcpower quick summary - Barb thru Paladin

This one can't be quite as complete as the prior builds, but it will at least put all the characters on the same scale, using the Orc-o-Matic v2. 

This will either look at melee attacks or cantrip-based Orcpower, the basic "what can I do every round, forever, until they kill me?" question. We can look at spells uniquely, and other special abilities like Hunter's Mark, Colossus Slayer, and the Rogue's sneak attack with a bit of fiddling with the program. I'll round to an approximate number.

So, here we go. Consider these a base from which clever play and builds can start.

More critical hit goodness (courtesy of Peter Dell'Orto)

+Peter V. Dell'Orto did a nice post on critical hits yesterday.

One thing that came up a few times is that there are cases where if you only crit on a 3 and have a skill of 3, then you're either rolling an awesome crit, or you're screwed.

This can be avoided, though, by using margin of success. There are only four values that result in critical hits: 3 through 6, and 5 and 6 only come into play with a large skill.

When you look at the Critical Hit table, though, there are really only a few outcomes.

  • No Defense
  • Defender drops what he's holding
  • Extra Damage (max normal, double, or triple)
  • Major Wound no matter what damage
  • Half-DR
  • Extra shock

October 3, 2015

Getting the Size/Speed Range Table Right and Wrong

I love the Size and Speed/Range Table in GURPS. EABA has one too. I think both games get things right and wrong here, and since I have an idle moment, I want to say why.

What's Right?

Where do these kinds of charts succeed? While there's lots of small things, here are the big ones that occur to me:


Both charts (the SSR can be found on p. B550; "The Chart" is on p. 2.8 of EABA v2.01) cover the entire possible range of scaling and are logarithmic in nature. My personal experience is that this is nearly mandatory, since both gaming and real life happen on widely different scales. 

This need not be frost giants and mortals, either. An aircraft carrier might well be the target of a light antitank weapon. A man might stomp on a bug. An industrial press might have hundreds - or thousands - of times the applied force capability of a human. 

So something that accounts for scale is necessary.

October 2, 2015

Castle of Horrors: Neil Stevenson

This is my character for +Mark Langsdorf's Modern meets Dungeon Fantasy mashup, Castle of Horrors. Some thoughts on his generation and makeup are intermixed.

Neil Stevenson (200 points)

Neil finished high school and joined the Army, where he was a pretty good soldier, mostly light infantry. Ranger training. Probably saw a bit of combat. When he got out, he decided to become a police officer, where he was picked up as a SWAT guy. This didn't sit so well with him after he noticed a pattern of excessive force. After a spectacularly botched raid, he was set up to take the blame . . . but he happened to be out sick with salmonella that day. Ooops. But he left the force in disgust and went to college. He dabbled as a rep for Fabrique-Nationale USA for a bit, so he has a ridiculous thing for FN weapons - it's definitely not rational. Studied law, psychology, and became a fairly successful PI.

Full character build follows!

Gollum: Because it's my birthday, and I wants it

Today is my birthday. If you want to celebrate with me, go read something i wrote, post a review or a comment, and share it with your friends. Maybe it's Technical Grappling or Grappling Old School. Maybe it's The Last Gasp, On Target, Violent Resolution, or The Deadly Spring. Hell, maybe it's a post on the costumes I make for my daughter.

But if you want to wish me well as I start my 45th trip around the sun, tell me what you liked, what you'd do differently, and how you'd use something I've one in your games. And share it. We bloggers are only as pervasive as what is shared that we've done.

** *** **

+Jeffro Johnson says very nice things about me.

September 30, 2015

Play Report - Castle of Horrors 1

We got in our first game of Castle of Horrors, a GURPS mash-up with modern day characters that get transported to a Dungeon Fantasy world. 

There are lots of house rules and altered point costs and stuff. I won't go into that now - you can probably read all about them on +Mark Langsdorf's blog. The rules were arrived at more or less by consensus, in that Mark posted them, gave us time to offer objections or changes, and then locked 'em in. 

We were old friends from college, meeting on a big ranch in eastern Texas for a hunting weekend. In 2012, there was a Shadowrun-esque genetic expression event, so some of our party are non-humans/demi-humans. One troll-like creature, one dwarf, an Orc, I think. 

We started in the famous "you wake up from a night's sleep" ploy (usually associated with bait-and-switch, but in this case, we were all forewarned, so booyah), and found ourselves in between a castle wall and its keep.

Initial exploration led us down a hallway, and it was spooky enough that all of us brought out weapons - especially after looking at what seemed to be bloodstained crossbow bolts embedded in a door. And the bolts were very organic-looking. Chitinous heads, some sort of bone-like or tube-like shaft, and freaking dragonfly wings for fletching. Looked grown,not made. So weapons out.