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GURPS Fox 01-14-2022 10:38 PM
GURPS 3e: Making a duct-rotor helicopter
 
So, I've been working on a CnC Tiberium/Generals fusion setting and one of the things I've been having problems with is designing duct-rotor helicopters (like the SA-2 Samson from Jake Cameron's Avatar) via GURPS Vehicle Builder.

I've been using multiple main rotors but I've been recommended to use concord wing rotors and seen a thread about using multiple coaxial rotors.

Is there any help in this regard?

I'll post a GVB writeup in a moment.

GURPS Fox 01-14-2022 10:42 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Code:
TL9 GDI GH Mk 1 Helicopter Gunship (Hawk)

Crew: 2 total. 2 crew stations covering vehicle maneuvering system, 6 communicators, 5 navigation aids, 18 sensors, 5 targeting systems, 246 countermeasures.

Subassemblies: Vehicle +7, Body +7, 4xADS Turret [Body] +2, 2xArmament Turret [Body:U] +0, 4xSensor Turret [Body] +1, Ground Attack Sensor Turret [Body:F] +1, 2xWings [Body] +3, 4xRotor (T) +5, Wheels +5.

P&P: two 9,750-kW GDI HP Gas Turbine Mk1s (Propane/LNG, Realistic, short term access), two 1,124 lbs. thrust GDI Helicopter Super Turbofan Mk1s (2D thrust vectoring, Propane/LNG, Realistic; long term access), four 4,500-kW GDI Duct Rotor Drivetrain Mk1s (long term access).

Fuel: 61,707 liter LNG (fire 13), four 15,427 liter self-sealing standard Body Fuel Tanks (fire modifier -3).

Occ: two roomy Cockpit Stations (improved access, crashweb), 12 normal PA-Compatable Passenger Seats (improved access, crashweb, folding seat), two Cockpit Air Tanks (3 hr. duration, rebreather), 14-man NBCT Kit, 14-man Helicopter Gunship Enviromental Control System        Cargo: two 9.8-m^3 Infantry Ordinance Hold 4.4-lbs/cf

Armor                          F    RL    B    T    U
Body                            6/240 5/180 5/180 4/120 4/120
ADS Turret                      4/50  4/50  4/50  4/50  0/0
Armament Turret (U)            5/180 5/180 4/120 4/120 4/120
Crew                            4/440 4/440 4/440 4/440 4/440
Sensor Turret                  4/50  4/50  4/50  4/50  0/0
Ground Attack Sensor Turret (F) 4/50  4/50  4/50  4/50  0/0
Wings                          4/120 4/120 4/120 4/120 4/120
Rotor (T)                      4/50  4/50  4/50  4/50  4/50
Wheels                          4/50  4/50  4/50  4/50  4/50

Weaponry                Malf        Type Damage      SS Acc 1/2D m Max m RoF TL
40mm GDI ADS Mk1        -            Cr  0d          14 0  0      0    1/1 9
2mm GDI EMAMS Mk1        Ver.        Cr  2d+1        11 12  192    1,737 50  9
40mm GDI GAGL Mk1        Ver. (Crit.) Cr  17d        20 13  439    3,383 25  9
6.8mm GDI MGG Mk1        Ver. (Crit.) Cr  9d+2        12 16  672    4,298 50  9
2mm AP GDI 2EMAMSAP Mk1  -            Cr  2d+1(2)    -  12  192    1,737 -  9
40mm HE GDI 40HE Mk1    -            Exp  18d [4d]    -  13  439    3,383 -  9
40mm HEDP GDI 40HEDP Mk1 -            Exp  12d(5) [4d] -  13  439    3,383 -  9
6.8mm AP GDI 6.8AP Mk1  -            Cr  9d+2(2)    -  16  677    4,298 -  9
6.8mm API GDI 6.8API Mk1 -            Cr  9d+2(2)    -  16  677    4,298 -  9
GDI ADSM Mk1            Crit        Exp  18d[4d]    -  -  0      4,800 -  9

Equipment
Body: 3,000 rounds 40mm HE GDI 40HE Mk1; 3,000 rounds 40mm HEDP GDI 40HEDP Mk1; 100,000 rounds 6.8mm AP GDI 6.8AP Mk1; 50,000 rounds 6.8mm API GDI 6.8API Mk1; MGG Door Mount; MGG HUDWAC (near miss indicator); 6.8mm 3-barrel GDI MGG Mk1 (L, medium barrel; very fine (accurate), caseless ammo, electrothermal ammo); 100,000 rounds 6.8mm AP GDI 6.8AP Mk1; 50,000 rounds 6.8mm API GDI 6.8API Mk1; MGG Door Mount; MGG HUDWAC (near miss indicator); 6.8mm 3-barrel GDI MGG Mk1 (R, medium barrel; very fine (accurate), caseless ammo, electrothermal ammo); two Light Missile Bays (3 hardpoints rated 75 kg each); two medium range GDI Medium-Range LaserComm Mk1s (2,000-mile range; sensitive, scrambler); medium range GDI Medium-Range Wide Band Radio Set Mk1 (1,000-mile range; very sensitive, VLF, scrambler, direction finder); two short range GDI Short-Range LaserComm Mk1s (200-mile range; sensitive, scrambler); short range GDI Short-Range Wide Band Radio Set Mk1 (100-mile range; very sensitive, VLF, scrambler, direction finder); mainframe EVA Computer (complexity 7; genius, hardened, very high capacity, neural net, sentient, supercompact); mainframe Vehicle Data Analysis Co-Processor (complexity 7; dedicated, genius, hardened, very high capacity, neural net, supercompact); mainframe Vehicle Electronic Warfare Co-Processor (complexity 7; dedicated, genius, hardened, very high capacity, neural net, supercompact); mainframe Vehicle Encryption Co-Processor (complexity 7; dedicated, genius, hardened, very high capacity, neural net, supercompact); mainframe Vehicle Main Computer (complexity 7; genius, hardened, very high capacity, neural net, supercompact); mainframe Vehicle Navigation Co-Processor (complexity 7; dedicated, genius, hardened, very high capacity, neural net, supercompact); mainframe Vehicle Sensors Co-Processor (complexity 7; dedicated, genius, hardened, very high capacity, neural net, supercompact); three macroframe Vehicle Fire Control Co-Processors (complexity 8; dedicated, genius, hardened, very high capacity, neural net, supercompact); 2,000-gig Computer Harddrive (hardened); six 1,000-gig Database Harddrives (hardened); 1,500-gig EVA Harddrive (hardened); Computer Navigation Program (C2); +7 Damage Control Assistance Program (C7); two Data Recovery Programs (C2); Electronic Warfare Database; Encrpytion Database; full EVA Personality Program (C5); GDI Data Encryption Program (C14); five GDI DataWarrior Mk1s (C1); Navigation Database; Recon Data Storage; Routine Vehicle Piloting Program (piloting-17, C7); Sensors Database; Warbook Database; four GDI ADS Gunnery Programs-16 (C8); two GDI Armament Turret Gunnery Programs-16 (C8); +9 Main Gun Fire Control Program (C8); 40 chaff Chaff Dispensers; 40 chaff Chaff Dispensers; 40 chaff Chaff Dispensers; 80 chaff Chaff Reloads; 80 chaff Chaff Reloads; 80 chaff Chaff Reloads; 40 flare Flare Dispensers; 40 flare Flare Dispensers; 40 flare Flare Dispensers; 80 flare Flare Reloads; 80 flare Flare Reloads; 80 flare Flare Reloads; two IR Jammers (1.5-mile range, jammer rating 4); four advanced Sensor Detection Systems; two military GPSs; two IFFs; Inertial Navigation System; Adaptive Camouflage (-2 spotting modifier); modest Emission Stealth (-2 spotting modifier); modest IR Stealth (-2 spotting modifier); Mimetic Camouflage (-6 spotting modifier); NBCT Sealing; NBCT-Grade Self-Sealing Hull; modest Sensor Stealth (-2 spotting modifier); Waterproofing; Psi Shielding (8 psi strength); Spall Liner; Radiation Shielding (1,000 PF).  ADS Turret: 5,000 rounds 2mm AP GDI 2EMAMSAP Mk1; 200 40mm GDI ADSM Mk1s (modest HEPF warhead; stealthy, self destruct, Skill-100 IIRH); ADS Universal Mount (concealed); ADSM/EMAMS Link; EMAMS Full Stabilizer; two 40mm slow autoloader GDI ADS Mk1s (F, concealed); 2mm 3-barrel GDI EMAMS Mk1 (F, extremely short barrel; concealed, very fine (accurate)).  Armament Turret (U): 40mm GDI GAGL Mk1 (F, very short barrel; concealed, low powered, very fine (accurate), caseless ammo, electrothermal ammo).  Sensor Turret: Search AESA (T, scan 19, 25-mile range; non-targeting, LPI); Search LIDAR (F, scan 19, 25-mile range; multimode, LPI); two Medium-Range LLTVs (F, magnification x25); two Search Thermographs (F, scan 21, 50-mile range); two Short-Range LLTVs (F, magnification x5); Magnetic Anomaly Detector (MAD) (scan 21, 50-mile range); Multiscanner (scan 21, 50-mile range); ranging Sound Ranging System (sound level 18); surveillance Sound Surveillance System (sound level 18); Search PESA (T, scan 21, 50-mile range).  Ground Attack Sensor Turret (F): Search AESA (T, scan 19, 25-mile range; non-targeting, LPI); Search LIDAR (F, scan 19, 25-mile range; multimode, LPI); two Medium-Range LLTVs (F, magnification x25); two Search Thermographs (F, scan 21, 50-mile range); two Short-Range LLTVs (F, magnification x5); Magnetic Anomaly Detector (MAD) (scan 21, 50-mile range); Multiscanner (scan 21, 50-mile range); ranging Sound Ranging System (sound level 18); surveillance Sound Surveillance System (sound level 18); Search PESA (T, scan 21, 50-mile range); two AGL HUDWACs (near miss indicator); Laser Designator Tracker; two Laser Designators (100-mile range).  Wings: two Light Rocket Bays (4 hardpoints rated 347 kg each).

GURPS Fox 01-14-2022 10:44 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Code:
Statistics
Size: [LxWxH] 12 m x9 m x5 m        Payload: 49,113 kg        Lwt.: 97,972 kg
Volume: 550 m^3        Maint.: 0.349 hours (275 mh/day)        Price: $3,293,199,720

HT: 11        HP: 6,000 [Body], 150 each [4xADS Turret], 28 each [2xArmament Turret (U)], 90 each [4xSensor Turret], 90 [Ground Attack Sensor Turret (F)], 375 each [2xWings], 2,700 [Rotor (T)], 300 each [4xWheels].

Aerial Performance: Stall Speed 0 kph, Drag 1,234, Top Speed 700 kph, aAccel 4.83 kph/s, aMR 17.5, aSR 4, aDecel 113 kph/s.

Wheel Ground Performance: Speed Factor 18, Top Speed 64.4 kph, gAccel 3.22 kph/s, gDecel 32.2 kph/s, gMR 0.5, gSR 4, Ground Pressure 13,499 lbs./sf, Off Road Speed 8.05 kph.


Design Notes:
TL10 responsive medium frame advanced materials [Body].
TL10 responsive medium frame advanced materials [4xRotor].
TL10 responsive light frame advanced materials [Wheels].

TL10 DR 50 advanced laminate [4xADS Turret].
TL10 DR 440 advanced laminate [Crew].
TL10 DR 50 advanced laminate [4xSensor Turret].
TL10 DR 50 advanced laminate [Ground Attack Sensor Turret].
TL10 DR 120 advanced laminate [Body].
TL10 DR 50 advanced laminate [4xRotor].
TL10 DR 50 skirt advanced laminate [Wheels].
Operating Duration:  3 H.
Payload Cost: $12,299,495
Vehicle Features: computerized controls, very good streamlining, 4x multiple main rotor.
Body: lifting body, 60° Front Slope, 30° Rear Slope, 30° Left Slope, 30° Right Slope.
Wings: stub.
Wheels: quantity 4, non-standard sizex1.5, retract into body, improved suspension, improved brakes, smart, puncture resistant.
ADS Turret: retractable, full rotation.
Armament Turret: limited rotation, 30° Front Slope, 30° Left Slope, 30° Right Slope.
Sensor Turret: retractable, full rotation.
Ground Attack Sensor Turret: retractable, full rotation.
Volume: 459 m^3 [Body], 1.3 m^3 [4xADS Turret], 0.161 m^3 [2xArmament Turret (U)], 0.743 m^3 [4xSensor Turret], 0.769 m^3 [Ground Attack Sensor Turret (F)], 5.2 m^3 [2xWings], 9.19 m^3 [4xRotor (T)], 34.5 m^3 [Wheels].
Area: 372 m^2 [Body], 9.29 m^2 [4xADS Turret], 1.77 m^2 [2xArmament Turret (U)], 5.57 m^2 [4xSensor Turret], 5.57 m^2 [Ground Attack Sensor Turret (F)], 23.2 m^2 [2xWings], 83.6 m^2 [4xRotor (T)], 74.3 m^2 [Wheels].
Aerial Performance: external item drag 1, payload 0, sweep none, unclamp top speed, use VXii stall speed;
Wheel Ground Performance:;
The rest of the writeup.

Fred Brackin 01-14-2022 10:49 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by GURPS Fox (Post 2411569)
So, I've been working on a CnC Tiberium/Generals fusion setting and one of the things I've been having problems with is designing duct-rotor helicopters (like the SA-2 Samson from Jake Cameron's Avatar) via GURPS Vehicle Builder.

I've been using multiple main rotors but I've been recommended to use concord wing rotors and seen a thread about using multiple coaxial rotors.

Is there any help in this regard?

I'll post a GVB writeup in a moment.
We may be having a terminology problem.

As far as Ve2/GVB goes there is no such thing as a "duct rotor". You can have "ducted fans" or several types of rotors (includign "Tilt rotors) but no "duct rotor".

Googling shows me a picture that qualifies as a "Ducted fan vertol" in Ve2/GVB. Though the fans are quite large.

You want "Ducted fans" from the "Airscrew" table on p.35 of Ve2. Then you want to go to "Vectored Thrust" on p.41

Avoid all helicopter drive trains..

GURPS Fox 01-14-2022 10:55 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by Fred Brackin (Post 2411577)
We may be having a terminology problem.

As far as Ve2/GVB goes there is no such thing as a "duct rotor". You can have "ducted fans" or several types of rotors (includign "Tilt rotors) but no "duct rotor".

Googling shows me a picture that qualifies as a "Ducted fan vertol" in Ve2/GVB. Though the fans are quite large.

You want "Ducted fans" from the "Airscrew" table on p.35 of Ve2. Then you want to go to "Vectored Thrust" on p.41

Avoid all helicopter drive trains..
The thing was, they looked like regular rotors, just in ducts. :\ So sorry for the hiccups that makes.

At least I've resigned to simply using multiple main rotors for intermeshing rotors helicopters...

Fred Brackin 01-14-2022 11:01 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by GURPS Fox (Post 2411578)
The thing was, they looked like regular rotors, just in ducts. :\ So sorry for the hiccups that makes.

At least I've resigned to simply using multiple main rotors for intermeshing rotors helicopters...
They do look very large for ducted fans. In the Real World this might give you better lift efficiency (which ducted fans suck at) but it'd come at the expense of forward speed.

What Ve2 _really_ loves is a lifting body with vectored thrust jet engines. That's where I always ended up when tryign to build this sort of thing.

Oh, and I agree about the "Kaman" style helicpters.

GURPS Fox 01-15-2022 12:31 AM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by Fred Brackin (Post 2411580)
They do look very large for ducted fans. In the Real World this might give you better lift efficiency (which ducted fans suck at) but it'd come at the expense of forward speed.

What Ve2 _really_ loves is a lifting body with vectored thrust jet engines. That's where I always ended up when tryign to build this sort of thing.

Oh, and I agree about the "Kaman" style helicpters.
To be honest, when I saw the 'Hummingbird' -the world's second military production helicopter... made in WW2 by the Germans- I was enamored with them. I mean, look at the thing, it's so adorable (for a military machine).

Anthony 01-15-2022 05:43 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
A more realistic treatment of fans in Vehicles would allow you to specify fan area and fan power separately; the reason helicopters have high lift efficiency is just because they have extremely large fans (lift is actually proportional to the 1/3 power of area and 2/3 power of fan power). The SA-2 Samson has similar fan size to area to a V-22 Osprey, which is pretty underwhelming as a helicopter.

The main problem with ducted rotors for helicopters is the 'why' problem -- it's a bunch of weight that serves no purpose in normal flight. It's useful for microdrones because it reduces damage (to both vehicle and object struck) when colliding with environmental objects, but at the sizes and speeds of full scale aircraft it will just be slightly differently shaped wreckage.

thrash 01-15-2022 07:27 PM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by Anthony (Post 2411642)
The main problem with ducted rotors for helicopters is the 'why' problem -- it's a bunch of weight that serves no purpose in normal flight.
Ducted fan blades are usually made of stiffer material and therefore able to run at higher RPMs than an equivalent rotor system, making them smaller for the same overall power. Done right, the blades should be lighter as well for being supported on both ends (and/or from not having to rotate some of the structural mass). Because they are self-contained, they can be vectored in ways that a conventional rotor system has trouble duplicating. I suspect there is also a gain in efficiency from eliminating rotor tip vortices, but I haven't seen the math on that.

That's not to say ducted fans don't involve a lot of additional weight and complexity, just that there are compensating gains.

RyanW 01-16-2022 09:05 AM
Re: GURPS 3e: Making a duct-rotor helicopter
 
Quote:
Originally Posted by thrash (Post 2411693)
That's not to say ducted fans don't involve a lot of additional weight and complexity, just that there are compensating gains.
On the other hand, helicopter rotors generate lift like a wing when the helicopter is moving, requiring much less down thrust (and thus power) than when hovering. A helicopter operating at the edge of its capacity can even stall (fully loaded Hinds in the high altitudes of Afghanistan had to make rolling takeoffs). If a ducted fan gains any lift that way, I'm sure it is greatly reduced.


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