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Old 10-02-2022, 01:25 AM   #21
hal
 
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Default Re: Vectored thrust vehicles of CP2020

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Originally Posted by Rupert View Post
I'm fairly sure having them right at the bottom will make for really exciting landing characteristics, so either way having the nozzles on the body is going to be bad.

I'm also sure that the illustrations assume way too little volume consumed by fuel, as those thing are going to burn it like crazy. They're a great example of brute force winning over common sense.
I think you may be right. In order to get the range for the AV-4, I have to add more fuel. When I add more fuel, I add more weight, which means I Have to add more jet engines to lift the added weight, which in turn, guzzles more fuel.f

Even trying to get the bare minimum (ie no weapon turrets etc) AV-4, requires that I halve the DR from 40 to DR 20 just to get the weight of the vehicle down to something manageable.
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Last edited by hal; 10-02-2022 at 08:58 AM.
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Old 10-02-2022, 01:27 AM   #22
hal
 
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Default Re: Vectored thrust vehicles of CP2020

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Originally Posted by the-red-scare View Post
SP 1 is definitely not 1” of steel, because Cyberpunk leather armor has SP 4 on the same scale. Cyberpunk SP and damage tend to match about 75-125% of GURPS DR and damage until you get up to heavy weapon levels, then Cyberpunk flattens out much quicker than GURPS does.

In any case, SP 40 is probably fairly close to DR 30-50.
I went into my CP2020 main book to look at armors and weapons. A MAC 10 .45 caliber submachinegun is rated at 2d6+2 damage. Nylon Helmet with a SP of 20, is supposed to be essentially Kevlar helmets of the 90's. 2d6+2 works on average, to being 9 points of damage. Armor piercing rounds treat an SP of 20 as being SP of 10. Now if we use assault rifles from CP2020, a 5.56 rifle will inflict 5d6 damage, with an average of 17 points. That means on average, the Helmet will stop even a rifle round, but there will be times where it doesn't. How often? Per TRAVELLER 5th edition tables of "odds" rolling a given number or less, rolling a 20 or less on 5d6 happens roughly 78% of the time. That means that roughly 22% of the time, the damage of a rifle round will penetrate an SP (stopping power) of 20. Oddly enough? A Colt M16 damage of 5d6 would require a DR of 20 to stop all damage roughly 78% of the time.

That makes me feel a whole heck of a lot better where it comes to armoring up the AV-4.

Thanks for the insight. :)
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Old 10-02-2022, 09:00 AM   #23
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Default Re: Vectored thrust vehicles of CP2020

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Even trying to get the bare minimum (ie no weapon turrets etc) AV-4, requires that I halve the DR from 40 to DR 20 just to get the weight of the vehicle down to something manageable.
Sounds about right. The Harrier is the main example of a successful vectored-thrust vehicle, and it's essentially a specialised engine, with other stuff hung off it. It was always weight-critical, and upgrades always had to start with more engine power.

The F-35B works around some of its limitations, at a higher TL, but is unproven in action.
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Old 10-02-2022, 10:33 AM   #24
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Default Re: Vectored thrust vehicles of CP2020

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I'm also sure that the illustrations assume way too little volume consumed by fuel, as those thing are going to burn it like crazy. They're a great example of brute force winning over common sense.
The F-4 Phantom II would like to talk to you about trademark infringement.
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Old 10-03-2022, 09:25 AM   #25
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Default Re: Vectored thrust vehicles of CP2020

English Electric Lightning, anyone? :)

In the very first edition of Cyberpunk the AV-4 was described as having been built onto a surplus Pegasus-successor engine, which would imply a massive air intake (never shown in any of the art), and nozzles which could swivel between rearward, downward and a bit of forward thrust. As well as the other problems people have pointed out, there's a great big plume of hot air which an IR missile can follow all the way to the engine - there's no way of getting IR baffling into that system.

It's worth noting that, while VIFFing turned out to have combat utility, the Harrier was expected to fly and fight in a conventional wingborne mode whenever possible - it's hugely vulnerable at the hover. Similarly the F-35 family.

Top versus bottom thrust location doesn't really matter for a jet engine – consider also rockets, of which Goddard's early designs did put the motors at the top of the structure, but it turned out not to help. ("Pendulum rocket fallacy" may be a helpful phrase to search.) As I understand it, it makes some sense for helicopters because when the body tilts the rotor is flexible enough that it's still mostly providing downward thrust (no longer through the centre of mass, so there's a torque effect) – but with a rocket or jet the thrust vector moves instantly and rigidly with the body, so you don't get any extra stability.

I don't think it's possible to design a realistic VTOL jet-engine craft that matches the AV-4's performance, armour and range. There's a reason we use wings.
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Old 10-03-2022, 09:46 AM   #26
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Default Re: Vectored thrust vehicles of CP2020

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English Electric Lightning, anyone? :)

I don't think it's possible to design a realistic VTOL jet-engine craft that matches the AV-4's performance, armour and range. There's a reason we use wings.
I know something about the EE Lightning (Simthsonisn Air &Space magzine article and maybe a TV show too) but your reference escapes me.

Ve2 considers a lifting body as a sort of wing and infact doesn't distinguish betwen lifting bodies and flying wings. You could create a workable AV-4 by building it as a lifting body and loitering in forward flight with aerodynamic lift mode.

You would need your engine to throttle down efficiently. You only need pure thrust in excess of weight for verical take off or landing. For cruising with aero lift as little as 1/5th to 1/10th that much would be fine..
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Old 10-03-2022, 10:22 AM   #27
johndallman
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Default Re: Vectored thrust vehicles of CP2020

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Originally Posted by Fred Brackin View Post
I know something about the EE Lightning (Simthsonisn Air &Space magzine article and maybe a TV show too) but your reference escapes me.
It was terribly short of volume for fuel. The engines and their ducts occupy almost all of the fuselage. The Mk I version had fuel in the wing flaps.
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Old 10-03-2022, 10:26 AM   #28
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Default Re: Vectored thrust vehicles of CP2020

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Originally Posted by Fred Brackin View Post
Ve2 considers a lifting body as a sort of wing and infact doesn't distinguish betwen lifting bodies and flying wings.
Which is correct, but the core thing to realize about vectored thrust air-breathing engines is that, outside of the very low velocity regime, the math controlling them is the same as the math for wings, and a multi-ton flying vehicle with a 5' wingspan would be spectacularly stupid.
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Old 10-03-2022, 10:55 AM   #29
hal
 
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Default Re: Vectored thrust vehicles of CP2020

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I don't think it's possible to design a realistic VTOL jet-engine craft that matches the AV-4's performance, armour and range. There's a reason we use wings.
Just out of curiosity - the specs given HERE that I did - does that reasonably come close to the AV-4 overall?

In looking at the Logistics for trying to cover say, Los Angeles as it is today, I'd need four landing pads for the TT Inc to be based off of. With an area that is roughly 44 miles long by 29 miles wide, a vehicle moving at 210 MPH on average, would be able to cover an area with a roughly 12 mile radius. This presumes that it takes about 16 seconds to go from a speed of zero to a speed of 210 miles per hour. Time required to accelerate upwards and then start heading towards the last known location of the patient, would likely be such that a standing team waiting for a call might lose about 1 minute getting airborne and taking off, spend 3.5 minutes travelling at 210 miles per hour before decelerating and then landing. Call it roughly 5 minutes with a safety margin of 1 minute to spare to meet its SLA (Service level Agreement).

IN bad weather, I don't know how that would work out, but presumably about the same.

So - the GURPS Analog as depicted above - is it good enough?
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Last edited by hal; 10-03-2022 at 10:57 AM. Reason: Added link to the specs given in a different thread.
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Old 10-03-2022, 10:40 PM   #30
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Default Re: Vectored thrust vehicles of CP2020

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Originally Posted by Witchking View Post
The F-4 Phantom II would like to talk to you about trademark infringement.
The Phantom (and the Lightning, for that matter) had a measurable glide angle. I'm pretty sure CP2020's AV-4s don't.
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