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Old 11-15-2019, 09:12 AM   #21
Varyon
 
Join Date: Jun 2013
Default Re: Making Gyrocs Great

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Originally Posted by Rupert View Post
The ammo weight is low compared to that for conventional guns and grenade launchers. The cost (for ungiunded rockets) is comparable to similar ammo for grenade launchers (payload rifle ammo is much more expensive, and very heavy). Interestingly the 25mm gauss grenades weight very little less (for the same amount of bang), but cost next to nothing. UT's gyroc ammo would seem to have a very small amount of very expensive and high-performance rocket propellant (so much so it doesn't really make sense).
Gyrocs aren't 25mm, they're 15mm. 15mm rifle ammo is admittedly heavier, but is a bit less expensive and does 2.5x as much damage with longer range. Gyrocs are roughly comparable to 10mm rifles (against an unarmored foe, injury is right between that of a storm carbine and storm rifle), and those use ammo that's 40% of the weight and 16% of the cost, which is why I said their ammo tends to be heavy and expensive for what it does.

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Originally Posted by Rupert View Post
APEP doesn't have to have a discarding sabot - the description merely notes what the core is, not that it's a sub-calibre penetrator. I agree on the APDS thjough (and APHD at TL11).
It's explicitly an APDS round with a denser core - it's APDSDU with the DU replaced by some flavor of tungsten alloy. Making the entire payload out of EP material would be an option, but I don't think it would have any different effect than APHC*. I did consider it, as it could serve to either shorten the round or let it fit more propellant, but that would require making even more assumptions and I felt the small amount of difference wasn't likely to be enough to bother with. For reference, assuming normal rounds are made of lead (or a tungsten alloy with comparable density) and EP has comparable density to DU, the payload would take up 60% as much volume. Turning the payload into something roughly approximating a hemisphere would buy you around 6mm - 6.67g. Going from a 45g projectile with 13.5g propellant to a 51.67g projectile with 20.17g propellant is around +10% mass fraction of propellant, that gets you around 600 extra yards for x1.15% WPS. However, EP is going to be more expensive than APHC. Considering APDS probably uses the same material as APHC, this implies a saboted round is 2.5x the cost of a normal one; applying this in reverse to APEP, this implies EP would be 4x cost. If you absolutely need to get as much range out of a gyroc as possible, combining EP with the longest level of Flight would result in a 75% mass fraction, getting you around x3.5 to range, but for a total of x5 CPS (I really should have done things as +CF to avoid confusion) and x2.2 WPS.

Note the (3) armor divisor, as per HT, isn't quite appropriate - APEP (which may be appropriate to rename APDSEP) should have AD (2) but deal 1.5x as much damage (which is the same impact on penetration) to keep it in line with the way APDSDU works. Unimportant for gyrocs, this implies APDSFSEP should also be an option, for x1.7 damage (+2.5/die to damage), for perhaps x12 cost.

*HT does have an APDU round, which is like APHC but with boosted damage - presumably because the round itself is heavier. As I'm opting to maintain the same weight, that doesn't apply here.

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Originally Posted by Rupert View Post
1/2D equalling Max could mean that there's a sustainer motor, and when it runs out the imprecise burnout and change in centre of gravity, etc. destabilises the bullet, so there's no effective reach past that point - this is why tracers go off-target when they burn out, and why rocket-assisted artillery rounds are less accurate than conventional ones, so it's not impossible.
I considered this as a possibility, but felt by TL9 it could be a solved problem. Still, if you don't want to have to deal with flat range, 1/2D, and Max as separate entries, it's an option.

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Originally Posted by Rupert View Post
GURPS' reactionless thrusters tend not to have very high accelerations compared to chemical rockets, and I don't think even a hypothetical version that exchanges better a thrust/weight ratio for a (very) short life would do well. It'd disallow 'hot' versions, but they'd have greater range (as you say), etc.
This is really just the option from UT145 applied to gyrocs. Maintaining 500 yards per second only needs 0.16G acceleration for a streamlined craft, according to Spaceships. A TL12^ Superhot (x2 damage/velocity) Reactionless gyroc, zooming downrange at Move 3000 (6000 mph) does need an acceleration around 6G, but seeing as my calculations above assume a 25% mass fraction of drive, that's only 1.2G per drive. Getting up to speed in only 10 seconds (or, as you note, perhaps 20 seconds) is perhaps problematic, of course - realistically (or at least as realistic as we can get when considering reactionless drives), a reactionless gyroc would probably have a small first stage that uses a traditional rocket engine to get up to speed, then switches to reactionless. Or, given the small amount of acceleration needed, it might have something like 4 high-acceleration reaction drives to get it up to speed, then rely on a 5th reactionless drive to maintain (normal gyrocs could do something similar).

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Originally Posted by Rupert View Post
The overall problems in UT come from 1) ETC weapons being just that good (and perhaps unfortunately RL research doesn't rule that out as a reasonable assumption)
From what I understand, Pulver has somewhat stepped back on his thoughts on ETC. I think the values I saw were that ETC should probably be x1.2, and if ETK is available, it would be the x1.5 we see for ETC in UT.

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Originally Posted by Rupert View Post
2) all warheads of the same calibre having the same payloads. A gyroc round intended for delivering a payload, rather than a KE-based round, could have a relatively low velocity (and long burn time to keep the range up) and thus a large payload compared to a rifle. That would make them a more accurate, but direct fire only, equivalent of a grenade launcher. Unlike a grenade launcher, you would have the option of high velocity, high-KE damage, rockets with shorter range.
As I understand it, for the most useful non-KE payload for a gyroc - HEAT - penetration is a function of caliber, so simply making the payload heavier isn't going to help much. For other payloads, you should be able to get 18.5mm performance with a 2x weight warhead, 25mm with a x5 weight warhead. With constant caliber, length will scale linearly with weight. From my calculations for Long Gyroc, the 18.5mm equivalent doesn't even leave enough room for the rocket on a standard gyroc. With a maximum-length Flight Gyroc, we have enough room for 45% mass fraction in fuel, for a burn range of around 3300 yards, which is respectable. At the same speed, the increased weight would result in around x1.25 to damage, which is right around +1/die. You can manage longer range with the slow gyroc option from above.
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Old 11-15-2019, 09:50 AM   #22
evileeyore
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Default Re: Making Gyrocs Great

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Originally Posted by Daigoro View Post
You can see some gyrojet test shots in this video, although they're using vintage ammo.

https://youtu.be/cJAXpyt8-oQ
The Taofledermaus boys at their best.

Here's Sean's video of the day (he's owner of the gyrojet pistol and carbine they were firing), and another Taofledermaus video on 3D printed rocket slugs for a shotgun...
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Old 11-15-2019, 02:07 PM   #23
Black Leviathan
 
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Default Re: Making Gyrocs Great

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Originally Posted by Anthony View Post
Is there some reason to continue calling that a gyroc? In the end, it's just a small missile.
That's a good question, It's still ignited by a rifle-trigger, it still loads from a magazine still unguided, but instead of being a rocket-powered rifle round it's more of a rocked-powered shotgun slug.

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Originally Posted by Anthony View Post
In general 'silent' and 'rocket' don't go together, unless you're willing to use an extremely low performance rocket.
Silent is a strong word perhaps. How about "Suppressed"? Substantially quieter than a man-portable rocket for having a smaller, cooler propulsion system. I'm envisioning a lot of WHOOOSH and not so much BANG. In my mind it would be harder to locate where shots are being fired from, but now I'm thinking about rockets that would most likely have chemtrails.. Maybe a no-go either way.

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Originally Posted by Varyon View Post
Slowing it down to 350 yards per second would put it subsonic. It would also take twice as long to burn through its fuel, traveling around 2800 yards in that time, so it would actually have longer range than a normal gyroc. Damage would drop to around 4d pi++.
.
Yeah that's where the slow Gyroc gets sloppy for me as well. At TL9 plus you're not going to get a lot of enemies who will be impressed with 4d given modern armor. If the payload could support some kind of high armor penetration or chemical delivery to disable your target then maybe? HEAT, while effective and cool would nearly invalidate the point of going subsonic.

Firing slow Gyrocs at range would have limited applications, especially given the damage. It would be really hard to hit something with a round that slow that would be impressed with a shot with so little velocity. Maybe an archaic way to mark a target with a radio transponder?

Slow-Gyroc might be a bit of a pipe-dream upon light criticism of the idea.
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Old 11-15-2019, 02:14 PM   #24
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Default Re: Making Gyrocs Great

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Originally Posted by Black Leviathan View Post
Yeah that's where the slow Gyroc gets sloppy for me as well. At TL9 plus you're not going to get a lot of enemies who will be impressed with 4d given modern armor. If the payload could support some kind of high armor penetration or chemical delivery to disable your target then maybe? HEAT, while effective and cool would nearly invalidate the point of going subsonic.
Not really. It'll ensure that people in the area notice somebody's been shot (with rather serious munitions) but the warhead explosion won't do anything to give away the location of the shooter.

With UT telemetry, it seems likely that military opponents would be alerted about your victim just as well if you perforated them with solid rounds. (Also how quiet are solid rounds punching through armor anyway?)
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Old 11-15-2019, 02:19 PM   #25
AlexanderHowl
 
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Default Re: Making Gyrocs Great

I like the idea of a 25mm gyroc, similar in weight and cost to the 25mmCL ammo, probably with similar damage and range, though the weapon could be lighter, cheaper, and have lower minimum ST and Rcl (perhaps 24 lbs., ST 10!, Rcl 2, and $4,000). At that point though, the 25mm Payload rifle would only really shine if ETC, but that would be acceptable.
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Old 11-15-2019, 02:23 PM   #26
Anthony
 
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Default Re: Making Gyrocs Great

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Originally Posted by Black Leviathan View Post
Silent is a strong word perhaps. How about "Suppressed"?
The main noise source is the rocket, not the sonic boom, so using a lower powered rocket will produce less noise, but probably not enough lower to be less than extremely obvious unless you use a low performance propellant.
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Originally Posted by Black Leviathan View Post
Slow-Gyroc might be a bit of a pipe-dream upon light criticism of the idea.
In general low speed projectiles (rockets are otherwise) are better suited for payload delivery than being kinetic weapons. 25mm rockets would probably compare very favorably to the payload rifle.
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Old 11-15-2019, 02:32 PM   #27
Ulzgoroth
 
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Default Re: Making Gyrocs Great

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Originally Posted by Black Leviathan View Post
Silent is a strong word perhaps. How about "Suppressed"? Substantially quieter than a man-portable rocket for having a smaller, cooler propulsion system. I'm envisioning a lot of WHOOOSH and not so much BANG. In my mind it would be harder to locate where shots are being fired from, but now I'm thinking about rockets that would most likely have chemtrails.. Maybe a no-go either way.
Alternate approach to obfuscating shooter position - use a sub-sonic soft-launch charge that kicks the rocket into the air before it ignites, and rig the guidance system to let you do that launch a bit off the bearing to the target. So you can have your missiles ignite a decent shot off to the side of where you launch them from.
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Old 11-15-2019, 02:50 PM   #28
Varyon
 
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Default Re: Making Gyrocs Great

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Originally Posted by Black Leviathan View Post
Yeah that's where the slow Gyroc gets sloppy for me as well. At TL9 plus you're not going to get a lot of enemies who will be impressed with 4d given modern armor. If the payload could support some kind of high armor penetration or chemical delivery to disable your target then maybe? HEAT, while effective and cool would nearly invalidate the point of going subsonic.
APHC would be 4d(2) Pi+, averaging 28 points of penetration. A Torso shot will cause a 6 HP Wound on a target in a reflex tacsuit, while a Vitals shot will cause a 12 HP Wound. Either could drop a sentry (although the former would just be from stunning), although he may cry out and give away your position. Away from my books, but APHEX may also be worthwhile (the internal explosion should be muffled by the target’s body). Against a target without sealed armor, some sort of poison gas (probably sleep, possibly nerve) could work.

Quote:
Firing slow Gyrocs at range would have limited applications, especially given the damage. It would be really hard to hit something with a round that slow that would be impressed with a shot with so little velocity. Maybe an archaic way to mark a target with a radio transponder?
While expensive, a guidance package can correct for this. And, really, with a mere Acc 2, a normal gyroc probably needs a guidance package to reliably manage a hit at any appreciable distance.
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Old 11-15-2019, 03:02 PM   #29
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Originally Posted by Ulzgoroth View Post
Alternate approach to obfuscating shooter position - use a sub-sonic soft-launch charge that kicks the rocket into the air before it ignites, and rig the guidance system to let you do that launch a bit off the bearing to the target.
This does have the side effect that the missile's guidance system must acquire the target after launch, as an off-bearing launch means it doesn't have line of sight before launch.

In general the solution for rockets making the location of the shooter obvious is using disposable launchers that you either fire by remote control or you just abandon before counterfire can hit you.
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Old 11-15-2019, 05:42 PM   #30
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Default Re: Making Gyrocs Great

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Originally Posted by Varyon View Post
APHC would be 4d(2) Pi+, averaging 28 points of penetration. A Torso shot will cause a 6 HP Wound on a target in a reflex tacsuit, while a Vitals shot will cause a 12 HP Wound. Either could drop a sentry (although the former would just be from stunning), although he may cry out and give away your position. Away from my books, but APHEX may also be worthwhile (the internal explosion should be muffled by the target’s body). Against a target without sealed armor, some sort of poison gas (probably sleep, possibly nerve) could work.
Now that I'm home and can check UT, APHEX isn't great but is an option. Assuming we add the explosion and shrapnel together with the initial wound to determine severity, a Torso shot against a character in a reflex tacsuit gets 4 damage past DR, increased to 8 HP for pi++ (APHEX doesn't suffer a piercing-class reduction, as the explosion makes it functionally frangible). The 1d-2 explosion averages 5.33 injury (1, 1, 3, 6, 9, 12), while the 1d-1 fragmentation averages 7.67 injury (1, 3, 6, 9, 12, 15). Adding it all up, that's 21 injury, enough to potentially kill an HP 10 character instantly (and those with higher HP through fairly rapid blood loss), enough to potentially incapacitate an HP 21 character, and enough to score a Major Wound on an HP 40 character (although the latter two are probably wearing thicker than normal armor); as 13 of the injury was functionally to the vitals, characters up to 25 HP are at -5 on the knockdown roll; actually, with that in mind you trigger a knockdown roll on any target with less than 140 HP (the least HP where a 13 HP wound doesn't cause a Shock penalty). Heavier armor - such as a tactical vest with trauma plates, or a clamshell - will soak the hit readily, but their improved protection doesn't protect the abdomen, so you can avoid it with a -1 to hit (or at least it doesn't protect the pelvis, which is at -3 to hit; note a hit there is also pretty much guaranteed to cripple your target's legs). A combat hardsuit is nearly immune - you'll need to aim at the face (DR 12 with the combat infantry helmet's faceplate, for 8 penetrating damage) at -5 to hit. On the bright side, a face hit is likely an instant KO - an internal face explosion should be treated as a brain hit, so you're looking at 16 + 7 (1, 1, 4, 8, 12, 16) + 10 (1, 4, 8, 12, 16, 20), for 33 HP injury; any character below 34 HP is at -10 on the knockdown roll, and any character below 180 HP has to make a knockdown roll. Of course, even without any appreciable sound, whoever is monitoring that guard's vitals (via the biomedical sensors likely installed) is likely going to notice their head exploding...

As for other fillers, sleep gas is probably your best bet if the target isn't Sealed. If you really want to kill the target, and don't expect to have time to get up close and personal to execute them, either use the double-weight payload variant from a prior post and fill half of it with sleep gas and half with nerve gas (just nerve gas is a bad idea, as 1d tox per minute gives them plenty of time to sound the alarm), or use a normal biochemical aerosol round and split it half-and-half between sleep and nerve. Roughly based on the Varying the Dosage (B439) guidelines, half doses would give +2 to resist and cut the time unconscious (for sleep) or the damage (for nerve) in half (nerve gas would also only do damage every 2 minutes). That, or shoot them first with Sleep, then follow up with Nerve on their unconscious body.

On that topic, does UT Nerve gas seem a little tame to anyone else? It's fast-acting, sure, but only has around a 50% shot of killing a typical person, which seems a bit underwhelming.

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Originally Posted by Varyon View Post
While expensive, a guidance package can correct for this. And, really, with a mere Acc 2, a normal gyroc probably needs a guidance package to reliably manage a hit at any appreciable distance.
It occurs to me I may have set guidance systems as a bit too expensive, as I based their price on the incredibly-expensive UT micromissile. Going to Spaceships, the Tactical Array is probably a decent fit for a multi-spectral guidance system. As it doesn't add appreciably to the projectile's mass, it is at most a 1/3 size system (~1.67%), more likely a 1/10th size system (~0.5%). Those systems cost $100/lb. At TL9, the smallest they can get would be on a 40mm, 2 lb micromissile, meaning right between 3/100 and 1/100 lb, for either $3 or $1. That's clearly far too cheap, so let's come at it from a different angle. An IR communicator probably has roughly comparable cost to an IR guidance system (the latter is likely more expensive, but this should give us a ballpark figure). UT43-44's IR communicator follows a trend of x2/lb to cost per x0.1 to weight. On a 15mm, 0.1 lb micromissile (the smallest you can manage at TL9), we're looking at between roughly 0.002 lb and 0.0005 lb, respectively. The former would be $1050/lb; the latter would be $1600/lb. That works out to $2 and $0.8, respectively, so that clearly doesn't work either.

At this point, there really isn't any option other than to basically arbitrarily set the prices. What prices seem like they'd be appropriate? I currently have it as $50 for Guided, $150 for IR, and $500 for Multi-spectral/Multiscanner. Do those look acceptable, or would something like 10/30/100 or even 5/15/50 be more acceptable? For reference, the former sets the prices as they'd be by UT rules for a $10 CPS round (so, my micromissiles); the latter sets it as they'd be for a $5 CPS round (so, a normal gyroc). For my 15mm micromissiles, I currently have the prices set at 60/160/510 while a 15mm rifle round would cost 90/190/540. With the cheaper prices, these become either 20/40/110 (micromissile) and 50/70/140 (smart bullet); or 15/25/60 (micromissile) and 45/55/90 (smart bullet).

Which looks better? Also, does my previous suggestion of x2 cost per +1 to skill for the Homing variants seem appropriate (for that matter, am I reading correctly that skill is actually TL+4+Acc)? As previously noted, this is simply applying the rules for higher TL gear, although it potentially (depending on how high you allow the bonus to go) allows for functional TL above 12.
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