Thursday, November 24, 2016

Shocker Lizard

CER 14 (OR 8 and PR 6)
Everyone’s hair stood on and as they approached the green reptile. Arcs of bluish-white light dances across its skin. Thankfully there was only one, or things would get hairy fast.
A three-foot long lizard with bright green scales and a yellow underbelly, the shocker lizard is a unique and frightening predator. It gets its name from its ability to discharge an electrical shock that can stun or kill prey. Alone, they are a nuisance, but a nest of shocker lizards rapidly grows to pose a lethal threat to any party!
ST: 7                                                       HP: 7                                                      Speed: 6.00
DX: 12                                                    Will: 10                                                  Ground Move: 6
IQ: 3                                                       Per: 12                                                   Water Move: 6
HT: 12                                                    FP: 12                                                     SM: -2

Dodge: 10                                             Parry: N/A                                             DR: 2

Bite (14): 1d-2 crushing. Reach C.
Shock: 1d-3 lethal electrical damage. Reach C. If two or more shocker lizards are within 2 yards of each other, damage is increased by 1 per lizard present and the attack gains the Explosion 3 enhancement – divide damage by the distance from the nearest lizard to any one victim!
Electric Sense: Shocker lizards can detect animal life with a successful Per roll, but not well enough to target it with an attack – it can only tell the general direction and SM of the animal.

Traits: Acute Smell 3; Bully (12); Cold Blooded (65°); Combat Reflexes; Discriminatory Smell; Gluttony (12); Jaw ST +2; Night Vision 9; Perfect Balance; Peripheral Vision; Quadruped; Terrain Adaptation (Undergrowth).
Features: Born Biter.
Skills: Brawling-14; Intimidation-11; Stealth-13; Swimming-12; Wrestling-14.

Thursday, October 13, 2016

Ents

With a creaking, cracking gate, the animate oak strode forward at an easy pace. It seemed little worried about the dozen gnolls arrayed before it, and hardly noticed their arrows. But once one buried its axe in the ent’s thick bark, the treebeast croaked with rage and sent the loathsome fae sailing through the air with a single swipe of a branch.
Ents are ambulatory, sapient trees who tend the most ancient forests.  They serve as gardeners and wardens, although they rarely pay any heed to any member of the animal kingdom unless a reasonable threat is posed.  Ancient by mortal standards, ents are extremely slow to action, do things slowly, and are very slow to embark on any endeavor.  Only a threat to the forest can readily mobilize the local ent population with any degree of rapidity, and "rapid" for an ent can take weeks.

Ent

CER 198 (OR 12 and PR 186)
An average, 20-foot-tall ent.
ST: 35                                                     HP: 145                                                  Speed: 5.50
DX: 9                                                      Will: 13                                                  Ground Move: 4
IQ: 10                                                     Per: 10
HT: 13                                                    FP: 13                                                     SM: 3

Dodge: 8                                                Parry: 7 (Unarmed)                             DR: 18

Branch Slam (9): 4d-2 crushing. Reach C-3. Usually made as a Telegraphic Attack.
Damage Reduction: DR is ablative to burning, corrosion, cutting, and huge piercing attacks to the same spot. DR is semi-ablative to multiple impaling, piercing, and large piercing attacks to the same spot. DR cannot be reduced below 1.

Traits: Chauvinistic; Common Sense; Decreased Time Rate; Dislikes Going Anywhere; Doesn't Breathe (Oxygen Absorption); Doesn't Eat or Drink (Requires Water); Fragile (Combustible); Green Thumb 1; Ham-Fisted 3; Hidebound; High Pain Threshold; Indomitable; Injury Tolerance (Homogenous; No Groin; No Neck); Pyrophobia (12); Regrowth; Sense of Duty (To forests, jungles, and other plant-covered areas); Unfazeable; Weak Sense of Humor.
Features: Affected as Plant.
Skills: Area Knowledge-13; Diplomacy-10; Gardening-13; History-13.
Notes: Ents are notoriously difficult for anyone to convince of anything (-3 to Influence rolls), and that's assuming anyone can even draw its attention.

Elder Ent

CER 798 (OR 25 and PR 773)
A truly ancient ent who has grown to the massive size of 50 feet and over 800,000 pounds.
ST: 65                                                     HP: 720                                                  Speed: 5.50
DX: 9                                                      Will: 15                                                  Ground Move: 4
IQ: 12                                                     Per: 12
HT: 13                                                    FP: 13                                                     SM: 5

Dodge: 8                                                Parry: 7 (Unarmed)                             DR: 30

Branch Slam (9): 7d crushing. Reach C-5. Usually made as a Telegraphic Attack.
Damage Reduction: DR is ablative to burning, corrosion, cutting, and huge piercing attacks to the same spot. DR is semi-ablative to multiple impaling, piercing, and large piercing attacks to the same spot. DR cannot be reduced below 1.

Traits: As Ent, but add Killjoy and Plant Empathy (Cosmic, No die roll required).
Features: Affected as Plant.
Skills: Area Knowledge-14; Diplomacy-12; Gardening-15; History-15.
Notes: Elder ents are even more difficult to communicate with or convince of anything (-6 to Influence rolls to get them to do anything they don't already want to do).  They care even less for the animal kingdom than their younger brethren.  While they are aware of animals, they generally ignore them.

Thursday, September 1, 2016

Wraith

CER 106 (OR 27 and PR 79)
Tendrils of cold, cloying darkness crawled from the shadows and snuffed the life from every candle in the room. The four travelers huddled together, back to back, and prepared for the wraith’s assault.
Wraiths are partially incorporeal undead that boarder on the demonic.  Little more than shadowy, animated hatred, they haunt the darkness of night seeking to drain the life from those they encounter, and when they succeed, their victim, tainted by the wraith's intense loathing of life, becomes twisted into a mirror of his executioner's – a weaker wraith serving its creator.
ST: 14                                                     HP: 15                                                   Speed: 6.00
DX: 12                                                    Will: 15                                                  Air Move: 12
IQ: 10                                                     Per: 12
HT: 12                                                    FP: N/A                                                  SM: 0

Dodge: 10                                              Parry: N/A                                              DR: 0

Punch (15): 1d(0.5) crushing + linked Life Drain (see below).  Reach C.
Life Drain (15): 3d+2 months of life drained per second.  Reach C.  This can only follow a successful grapple – often a choke hold (see Strangle Hold below).
Strangle Hold (12): On a successful attack, the wraith grapples his victim's neck.  On the victim's next turn, he may attempt to break free; the wraith is at +5 in this Quick Contest for using two hands.  On the wraith's next turn – and each turn thereafter, until its prey breaks free – it may strangle.  Roll a Quick Contest of the wraith's ST+3 vs. the victim's HT.  If the wraith wins, its victim takes crushing damage equal to its margin of victory.  DR protects normally, but multiply injury to the neck by 1.5.  If any damage – even blunt trauma – penetrates the victim's DR, you also start to suffocate him.  On his next turn and every subsequent turn until he escapes, he loses 1 FP; see Suffocation (B436).
Terror (Will-3): When a wraith moans or screams menacingly, anyone who hears it must make a Fright Check at -3.
Aura of Hopelessness: Anyone who fails a Fright Check in the wraith’s presence suffers -3 to all rolls. Every turn, the victim rolls against Will at a penalty equal to his margin of failure on the triggering Fright Check; on a success, he snaps out of his self-doubt.
Firebane: Wraiths suck the energy out of the area around them. Within two yards, candles are extinguished, torches burn as candles, and campfires burn as torches, and bonfires burn as campfires.
Light Weakness: Wraiths take quadruple damage from light attacks, 1d injury/minute from direct, natural sunlight, and lose their ability to interact with the physical world in any lighting conditions that impose a Vision penalty between +0 to -4.
Shadow Body: Wraiths are composed of partially insubstantial shadowstuff.  They can flow through any opening like a vapor; flight through the night air; take only 1 point of damage from impaling and piercing attacks and 2 points from all other non-area attacks.

Traits: Bloodlust (9); Callous; Can Be Turned by True Faith; Combat Reflexes; Darkvision; Desecrator; Detect (All Life; Precise); Doesn’t Breathe; Doesn’t Eat or Drink; Doesn’t Sleep; Dominance; Dread (Sunlight; 1 yard); Flight; Fragile (Unnatural); Frightens Animals; High Pain Threshold; Immune to Metabolic Hazards; Indomitable; Injury Tolerance (Diffuse; Infiltration); Insubstantial (Accessibility, Not in Darkness less than -4; Affect Substantial; Always On); Intolerance (The Living); Lifebane; No Legs (Aerial); Obscure 5 (Vision; Area Effect, 2 yards; Defensive; Emanation); See Invisible (Ghosts); Temperature Control 5 (Cold; Emanation); Uncontrollable Appetite (Life Force) (9); Unfazeable; Unkillable 3 (Achilles’ Heel, Sunlight).
Features: Affected as Evil; Affected as Dead; Functions and Detects as Evil.
Skills: Brawling-15; Hidden Lore (Undead)-10; Intimidate-15; Stealth-22; Wrestling-14.
Notes: Wraiths can speak and may be willing to negotiate, but rarely bother to. They often know much about other wraiths, if not undeath in general. A wraith's spawn usually have the same stats as its parent, with -2 ST.

Friday, August 26, 2016

Perk: Library Card

Library Card

1 point
Whether by virtue of reputation, actual license, or simply a plot device, you can waltz into any institution that houses knowledge and access any document or artifact housed therein - provided it isn't classified! No one will think twice about it or delay you, assuming the materials are available readily accessible, and if any time must be taken to retrieve them, you will gain access in the minimum possible time. This perk does not grant access to materials that are classified or those that are not on site, checked out, or otherwise not available. The GM should still feel free to deny the character access to information when circumstances would demand it - e.g., if the character just trashed the library's public collection and then asks to visit more delicate archives, or if the clerk knows the PC is wanted by the police.

A prime example of a character with this perk is Professor Robert Langdon from Dan Brown's The Da Vinci Code. He walks into museum after museum asking to see priceless and delicate artifacts and documents without any issues - excepting, of course, the police chasing after him.

Thursday, July 21, 2016

Peryton

CER 57 (OR 42 and PR 15)
A loud snorting sniff rang through the treetops. Jack heard the scuffle of rabbits and squirrels running for their dens. Another sniff, closer this time, sent the boar he was stalking into a startled retreat. Then with a swift stoop, the peryton struck Jack, grabbed him by the belly and thigh, and lifted the boy into the air.
Perytons are omnivorous beasts with the front half of a stag and the back half of a bird. They are fleet of foot and swift of wing, often taking to flight when startled. Perytons supplement their largely herbivorous diet with protein from small deer, lambs, and other mid-sized mammals. They have been known to take children when
ST: 18                                                     HP: 18                                                    Speed: 6.00
DX: 13                                                    Will: 10                                                  Ground Move: 7/14
IQ: 4                                                       Per: 12                                                   Air Speed: 14/28
HT: 11                                                    FP: 11                                                     SM: 1 (4.5 feet)

Dodge: 10                                             Parry: N/A                                             DR: 2 (Tough Skin)

Bite (14): 1d crushing. Reach C
Hooves (14): 1d+2 crushing. Reach C, 1.
Talons (14): 1d+2 cutting or impaling. Reach C.
Antlers (14): 1d+4 impaling. Reach C, 1.

Traits: Bad Sight 4 (Motion Sensitive); Bad Temper (12); Discriminatory Smell; Flight (Cannot Hover, Winged); Night Vision 6; Panic (12); Parabolic Hearing 2; Perfect Balance; Peripheral Vision; Quadruped; Temperature Tolerance 1 (Cold); Terrain Adaptation (Undergrowth); Ultrahearing; Wild Animal.
Skills: Brawling-14; Intimidation-10; Jumping-12; Stealth-12; Swimming-11; Wrestling-14.
Encumbrance: None 64.8 lbs.; Light 129.6 lbs.; Medium 194.4 lbs.; Heavy 388.8 lbs.; Very Heavy 648 lbs.

Thursday, June 23, 2016

Accuracy (Sorcery)

This common weapon enchantment is intended for use with GURPSThaumatology: Sorcery.

Accurate Weapon

Key Words: Weapon Buff
Full Cost: 24 points for level 1, 37 points for level 2, and 51 points for level 3.
Casting Roll: None. Use Innate Attack (Gaze) to aim.
Range: 100 yards
Duration: 3 minutes.

The weapon enhanced is more likely to hit for the duration by adding its level to the user’s effective skill (maximum 3). This stacks with mundane bonuses, such as weapon quality, but not magical ones.

Statistics: Affliction 1 (HT; Accessibility, Only on weapons, -20%; Advantage, Accuracy, +135%; Fixed Duration, +0%; Increased 1/2D, 10x, +15%; No Signature, +20%; Sorcery, -15%) [23.5]. Additional levels add further levels of Accuracy to the Advantage enhancement (+135%) [+13.5]. Notes: "Accuracy " is Weapon Talent (Magical, -10%) [13.5]. Weapon Talent adds its level to Beam Weapons, Blowpipe, Bolas, Bow, Cloak, Crossbow, Garrote, Gunner, Guns, Lance, Lasso, Liquid Projector, Melee Weapon, Net, Shield, Sling, Throwing Art, and Thrown Weapon.


Energy Point Cost Table

Energy Point Cost
Weapon Type +1 +2 +3
Projectile 3 5 7
Staff 9 13 18
Wand 10 15 21
Weapon 11 17 23

Thursday, June 16, 2016

Review: The Tome of the Black Island

I like worldbuilding. I like it more than rules tinkering (sorry Doug). I like it more than GMing. I like it more than playing. I say this to explain why I generally shy away from “fluff” articles and books that present premade world material. That’s the stuff I love to create, and those publications are taking that away from me! Interesting rules tweaks? Yes, please! Advice on how to run my creation in a game? Certainly! Options for playing a character in my world? Hell yeah! Hand me a world already made? No thank you. Keep this in mind as you read my review of The Tome of the Black Island by J. Edward Tremlett.

This month, I got a bit blindsided by one article in GURPS Pyramid#3/91 – Thaumatology IV. As usual, I gave the issue a cursory perusal to see where I wanted to begin. I helped review C.R.’s Codex Duello, so I marked that for last. W. A. Frick’s Technomysticism doesn’t cover a topic I, personally, care for, so that got bumped down the list, too. Ted Brock’s The Thaumaturgy of Metallurgy looked specific to standard spell magic, and being an RPM guy, I set that aside for later idea-mining. This month’s Random Thought Table had some interesting thoughts, as usual, but is a small offering. That brought me to The Tome of the Black Island, a systemless article about the mad writings of a depraved and corrupted wizard. I was intrigued.

I started reading it, expecting to find it far too fluff-heavy. I thought I’d get turned off pretty early on, but after about one sentence, I couldn’t put it down. It drew me into the story the way H.P. Lovecraft or Edgar Allen Poe did when I first starting reading them. Heck, it read like something out of the Cthulhu mythos. And as the plot twisted and turned, I couldn’t help but keep reading about Maldrick Udelholfen’s lust for power and how it ultimately destroyed him. The mad sorcerer’s tale perfectly married the sublime with the grotesque in an orgiastic display of gothic horror. I loved it.

But Tremlett’s real accomplishment lay in what he held back. Why didn’t those servants try to escape the fire? Why did Udelholfen return so disfigured? He waits until you think the story is over and you’ve dropped your guard. It’s time to read how to use the Tome in your game, what it contains, where it might pop up, – the crunchy bits. And as you examine those spell descriptions and possibilities, he hits you with another wave of horror. Now everything makes a little too much sense. Did I really want to know that? Oh god.


So when I say this article is excellent, take it as coming from someone who generally doesn’t want this sort of thing in his monthly issues. I feel like I might have missed out by dismissing some of Tremlett's past articles, too. I will say, I plan on going back and rereading them all. I’m going to check out his blog, Spygod, too.

Thursday, June 9, 2016

Nymphs Part 4: Water Nymphs

The crystal clear water of the icy pool shimmered and rippled in the still air of the morning. Gradually, the ripples grew in an upward undulation that formed shapely calves, then thighs, and eventually a fully formed woman of surpassing beauty.
Nymphs are loci geniuses that inhabit various natural places. While similar to what are sometimes called “fae”, they more closely resemble elementals of a specific locale. They are inherently tied to the location they inhabit; indeed, their very existence depends on the wellbeing of the environment. And they defend it vehemently.

All nymphs exercise a measure of control over their homes and use this, in combination with their preternatural beauty to ward off attacks. Their beauty is terrible and captivating, and they use this mercilessly to their advantage.

As dangerous as nymphs can be, they are excellent sources of information on the area in which they dwell, and if befriended, they make powerful allies. However, their legendary shyness makes this difficult, and their sadistic impulses make it doubly dangerous!

Water Nymph

CER 68 (OR 26 and PR 42)
Water nymphs are spirits of place associated with bodies of fresh water. They are closely attached to springs, lakes, rivers, etc. and may not stray more than a short distance from their home without becoming seriously ill. They defend their homes fiercely by luring those who threaten it to a watery death. Some water nymphs are experienced mages, but most are simply guardians. All command great knowledge about their environment.
ST: 8                                                       HP: 8                                                      Speed: 6.00
DX: 12                                                    Will: 10                                                  Ground Move: 6
IQ: 10                                                     Per: 11                                                   Water Move: 6
HT: 12                                                    FP: 12                                                     SM: 0

Dodge: 9                                                Parry: 10 (Unarmed)                           DR: 0

Punch (14): 1d-2 crushing. Reach C.
Animated Environment: Water nymphs can animate the environment around them to grapple (Binding or Telekinesis) intruders with ST 10 or strike at them (1d crushing or impaling) with branches and bushes near the shore.
Intoxicating Beauty (Resisted at Will): Anyone within 16 yards of a nymph who can see her must make a Will roll or gain the Lecherousness (12) disadvantage for a number of minutes equal to their margin of failure.
Kiss of Death (Resisted at HT): A corporeal nymph can kiss a foe (roll against 14) and send him into unearthly ecstasy (see p. B428) if he fails his HT roll – assuming he even wants to resist – that lasts minutes equal to his margin of failure.  Even if he does not resist, the roll must be made, because any failure by 5 or more results in him suffering a heart attack (see p. B4249).
Stunning Beauty: By striking even the slightest pose, anyone who sees her must make a Fright Check at -5 and roll on the Awe table.
Threshold Entity: This being doesn’t breathe, drink, eat, or sleep, is immune to metabolic hazards, and is either insubstantial and invisible or substantial and visible.

Traits: Acute Hearing 1; Appearance (Transcendent; Universal); Berserk (9) (Special Trigger, harming the wilderness); Callous; Can Be Turned with True Faith; Curious (15); Dependency (Home Lake or Spring; Daily); Dislikes Loud Noises; Divine Curse (Keep to the letter of any promise); Fearlessness 2; Higher Purpose (Protect Home Spring); Impulsive (12); Odious Personal Habit -1 (Capricious); Sadism (15); Sense of Duty (Home Spring); Shyness (Mild); Terrain Adaptation (Water and Wetlands); Unaging; Vulnerability (Iron x2).
Features: Affected as Spirit.
Skills: Area Knowledge (Local)-12; Brawling-14; Camouflage-12; Intimidation-17; Naturalist-12; Sex Appeal-17; Stealth-14; Swimming-14; Wrestling-14.
Notes: Most nymphs won't negotiate because they are too shy.  Those who do are amiable enough, but dealing with such an astounding beauty is often disconcerting – especially while under the effect of her intoxicating beauty (see above).  Always scars from wounds inflicted by iron.

Thursday, April 28, 2016

Nymphs Part 3: Tree Nymph

The crystal clear water of the icy pool shimmered and rippled in the still air of the morning. Gradually, the ripples grew in an upward undulation that formed shapely calves, then thighs, and eventually a fully formed woman of surpassing beauty.
Nymphs are loci geniuses that inhabit various natural places. While similar to what are sometimes called “fae”, they more closely resemble elementals of a specific locale. They are inherently tied to the location they inhabit; indeed, their very existence depends on the wellbeing of the environment. And they defend it vehemently.

All nymphs exercise a measure of control over their homes and use this, in combination with their preternatural beauty to ward off attacks. Their beauty is terrible and captivating, and they use this mercilessly to their advantage.

As dangerous as nymphs can be, they are excellent sources of information on the area in which they dwell, and if befriended, they make powerful allies. However, their legendary shyness makes this difficult, and their sadistic impulses make it doubly dangerous!

Tree Nymph

CER 72 (OR 31 and PR 41)
Tree nymphs are spirits of place who watch over woodland areas.  They are closely attached to trees and may not stray more than a short distance from their home tree without becoming seriously ill.  They defend their homes fiercely, employing magic to animate the plants and trees around them, usually while hiding inside a tree.  Some tree nymphs are experienced mages, but most are simple forest guardians.  All command great knowledge about their environment.
ST: 8                                                       HP: 8                                                      Speed: 6.00
DX: 12                                                    Will: 10                                                  Ground Move: 6
IQ: 10                                                     Per: 11
HT: 12                                                    FP: 12                                                     SM: 0

Dodge: 9                                                Parry: 10 (Unarmed)                           DR: 3

Bow (14): 1d impaling. Acc 3. Range 120/160. Bulk -7.
Club (14): 1d-1 crushing. Reach 1.
Punch (14): 1d-2 crushing. Reach C.
Animated Environment: Tree nymphs can animate the environment around them to grapple (Binding or Telekinesis) intruders with ST 10 or strike at them (1d crushing or impaling) with branches.
Stunning Beauty: By striking even the slightest pose, anyone who sees her must make a Fright Check at -5 and roll on the Awe table.
Threshold Entity: This being doesn’t breathe, drink, eat, or sleep, is immune to metabolic hazards, and is either insubstantial and invisible or substantial and visible.
Woodwalk: A tree nymph can see and move through wood without hindrance.

Traits: Acute Hearing 1; Appearance (Beautiful; Universal); Berserk (9) (Special Trigger, harming the wilderness); Callous; Can Be Turned with True Faith; Curious (15); Dependency (Home Tree; Daily); Dislikes Loud Noises; Divine Curse (Keep to the letter of any promise); Fearlessness 2; Fragile (Combustible); Higher Purpose (Protect Home Tree); Impulsive (12); Night Vision 5; Obsession (Protect Trees); Odious Personal Habit -1 (Capricious); Sadism (15); Sense of Duty (Home Tree); Shyness (Mild); Silence 2 (Limited, In Woodlands Only); Terrain Adaptation (Jungle or Woodlands); Unaging; Vulnerability (Iron x2); Walk on Liquid (Specialized, Water).
Features: Affected as Spirit.
Skills: Area Knowledge (Local)-12; Axe/Mace-14; Bow-14; Brawling-14; Camouflage-12; Intimidation-17; Naturalist-12; Sex Appeal-12; Stealth-14 (18 in jungles and woodlands); Wrestling-14.
Notes: Most nymphs won't negotiate because they are too shy.  Those who do are amiable enough, but dealing with such an astounding beauty is often disconcerting – especially while under the effect of her intoxicating beauty (see above).  Always scars from wounds inflicted by iron.

Thursday, March 17, 2016

Nymphs Part 2: Mountain Nymph

The crystal clear water of the icy pool shimmered and rippled in the still air of the morning. Gradually, the ripples grew in an upward undulation that formed shapely calves, then thighs, and eventually a fully formed woman of surpassing beauty.
Nymphs are loci geniuses that inhabit various natural places. While similar to what are sometimes called “fae”, they more closely resemble elementals of a specific locale. They are inherently tied to the location they inhabit; indeed, their very existence depends on the wellbeing of the environment. And they defend it vehemently.

All nymphs exercise a measure of control over their homes and use this, in combination with their preternatural beauty to ward off attacks. Their beauty is terrible and captivating, and they use this mercilessly to their advantage.

As dangerous as nymphs can be, they are excellent sources of information on the area in which they dwell, and if befriended, they make powerful allies. However, their legendary shyness makes this difficult, and their sadistic impulses make it doubly dangerous!

Mountain Nymph

CER 73 (OR 27 and PR 46)
Mountain nymphs are spirits of place who watch over mountainous areas.  They are closely attached to particular passes, grottos, peaks, etc., and may not stray more than a short distance from them without becoming seriously ill.  They defend their homes fiercely, employing magic to animate the mountain itself, often while dancing about high above.  All mountain nymphs command great knowledge about their environment.
ST: 9                                                       HP: 10                                                    Speed: 6.00
DX: 12                                                    Will: 10                                                  Ground Move: 6
IQ: 10                                                     Per: 11                                                   Climbing Move: 6
HT: 12                                                    FP: 12                                                     SM: 0

Dodge: 9                                                Parry: 10 (Unarmed)                           DR: 5

Punch (14): 1d-1 crushing. Reach C.
Quarterstaff (14): 1d+1 crushing (swing) or 1d crushing (thrust). Reach 1, 2*.
Animated Environment: Mountain nymphs can animate the environment around them to slide or knock intruders from their feet (target takes 3d crushing double knockback no wounding), strike at them (1d crushing or impaling) with rocks from above, or cause the ground to partially swallow a person – treat as Binding 10.
Difficult Terrain: A mountain nymph can cause anyone within their domain to have difficulty maintaining their balance or moving about.  The victim must roll a Quick Contest between his Will and the nymph's Will.  On a failure, the subject suffers a -2 penalty to DX and -2 penalty to Acrobatics, Jumping, Climbing, and Skiing lasting a number of minutes equal to his margin of failure.
Stunning Beauty: By striking even the slightest pose, anyone who sees her must make a Fright Check at -5 and roll on the Awe table.
Threshold Entity: This being doesn’t breathe, drink, eat, or sleep, is immune to metabolic hazards, and is either insubstantial and invisible or substantial and visible.

Traits: Acute Hearing 2; Appearance (Very Beautiful; Universal); Berserk (9) (Special Trigger, harming the wilderness); Callous; Can Be Turned by True Faith; Curious (15); Dependency (Home Mountain; Daily); Dislikes Loud Noises; Divine Curse (Keep to the letter of any promise); Fearlessness 2; Higher Purpose (Protect Home Mountain); Impulsive (12); Odious Personal Habit -1 (Capricious); Perfect Balance; Sadism (15); Sense of Duty (Home Mountain); Shyness (Mild); Super Jump 1; Terrain Adaptation (Mountain); Unaging; Vulnerability (Iron x2).
Features: Affected as Spirit.
Skills: Area Knowledge (Local)-12; Brawling-14; Climbing-16; Dancing-16; Intimidation-17; Jumping-16; Naturalist-12; Quarterstaff-14; Sex Appeal-12; Stealth-14.
Notes: Most nymphs won't negotiate because they are too shy.  Those who do are amiable enough, but dealing with such an astounding beauty is often disconcerting – especially while under the effect of her intoxicating beauty (see above).  Always scars from wounds inflicted by iron.

Monday, March 14, 2016

This Time It IS Rocket Science!

Last instalment, I discussed the parameters of the Rocket Design Project for this semester. This time, I’m going to get into how we make our predictions. Below is a derivation of the formulas necessary for predicting the apogee of a spherical bovine rocket undergoing air drag.

Warning: Math Ahead


So ultimately, we want to know how high the rocket will go. I am going to call this “y”, “displacement” or “apogee” interchangeably. I might even call it the height. Either way, this is what we are ultimately trying to solve for.

Anyone who has taken a basic calculus or physics class probably recognizes a few truths:
and
That is to say, the change in location of an object over a period of time is its velocity, and its change in velocity over a period of time is its acceleration. Thankfully, we can also say this in reverse:
and
This becomes important when we consider that the flight of any object is based on the sum of the forces acting on it. This is grounded in Newton’s Laws of Motion. Thus we know that the sum of our forces is

where F = force, m = mass, and a = acceleration. Thus,

Now we have a few terms here that we need to sort out: FThrust, FDrag, and FWeight. Of these, we can generally not worry about FThrust because that information is available based on our motor. Likewise, we know that FWeight = mg, where g is the acceleration due to gravity. This leaves FDrag for us to define:

where ρ = the density of air, CD = the coefficient of drag, A = the crossectional area of the rocket, and v = the velocity. This may seem like a lot of information, but much of it really doesn’t change with time for our purposes here. So I am going to combine a bunch of these into a constant. I will do this a few more times to clean up equations and put them in more easily recognizable forms, too.

Now we have a simpler looking equation:
Substituting this and the formula for FWeight, we get:
One more substitution, referring back to the beginning gives us
and we are ready to separate the variables and integrate.
But first, we are going to use some algebraic manipulations to get this looking like something we can integrate more easily:
Let
Thus
Now it’s time to integrate both sides:
Both m and k are constants, so we pull those out and integrate the right side:
We should now recognize the integral on the left as tanh-1 u:
By the definition of tanh-1, we can perform the following manipulations:
Therefore,
And define the constant
This lets us say:
Raising both sides to the e power gives:
Then we multiply both sides by the denominator:
Expanding the right side gives us:
Next, I need to isolate my v’s on one side:
Next, factor out v:
And divide both sides by (-ext-1):
Put more neatly:
And thankfully, we know that t = impulse divided by thrust, both of which are specifications provided by our motors. So now we know the final velocity when the motor finishes burning its fuel, but that doesn’t tell us either how high the rocket is at that point or how far it continues to coast. For that information, we need more integration.

We will begin by solving for yBurn, or how far the rocket travels while the motor is still providing thrust. For simplicity’s sake, we will assume the rocket’s weight does not change during this time (we are launching a frictionless spherical cow, aren’t we?), so m will continue to refer to the mass of the rocket while it is full of propellant.

Referring back to our original equation, we know that:
So we can say
By separating the variables and integrating both sides, we get:
Which becomes:
Now we know the rocket’s altitude when the motor cuts out, but the rocket won’t instantly stop; it will continue to coast. So let yCoast = the distance the rocket coasts on its momentum before beginning its descent. That is to say, how far will the rocket travel upward once FThrust = 0. Note that since the rocket has exhausted all of its fuel, we no longer use mFull – we are now use mEmpty.
This should all look a bit familiar, but not that because FThrust = 0, that term is simply missing:
By integrating both sides, we get:
Which becomes:
Now, we know the rocket’s apogee will be the sum of how high it goes while under power (yBurn) and how far it coasts before the acceleration due to gravity starts returning it to Earth (yCoast):
And there you have it! To summarize:








Where,
A = the area of the rocket’s cross-section normal to its velocity vector.
CD = the rocket’s coefficient of drag.
FThrust = the motor’s thrust in Newtons.
g = the acceleration due to gravity.
I = the motor’s impulse in seconds.
mEmpty = the mass of the rocket after burnout.
mFull = the mass of the rocket at liftoff.
ρ = the density of air.

Of course, the astute reader will notice that through all of that mess, there is one term still undefined- CD. This is the coefficient of drag, and determining it generally requires experimentation or running simulations. For our purposes, that is where OpenRocket and SolidWorks come in. Both are capable of determining CD.

Did you survive? I warned you there’d be math!