I'm pretty sure it's just a design exercise and not an actual prototype or anything. Asymmetry like that makes equipment look more functional and purpose-built, I assume that's why the artist designed it that way although obviously I'm in no place to say for sure.

I agree with Caadium though, it's pretty bad ass.

Also, Tsithlis, I think your drawing is also bad ass, and if I was running a game and you brought that to me I would bend over backwards as a GM to find a way to get it into the story.

This post has been edited by svenftw: Mar 4 2010, 11:15 PM

It could be designed for racing on an oval track whereupon you only turn right (like Nascar only on flying motorcycles and way cooler...)

Tons of it.
And if you wondered about the statement you quoted: no thrill seeker ever survived even a single one of my adventures. I have problem with killing off the characters of my players if they make mistakes.

Sweet, I was wondering the same thing. Thanks for answering it.

Also: I think it's really awsome that you found a group which suits your GMing style. (IMG:style_emoticons/default/biggrin.gif) It's always nice when everything works out.

Now then, since you play your game your way, and other people play their games their way, why are you being so very, very negative on this person's jet bike?

Btw, I like your picture Tsithlis. I'm quite ok with: "How does this work?" "I don't know, I'm not a professional scientist, nor am I from the future. Is it balanced for your game?" "Sure, looks fun."

Isn't that how it should always be? I wouldn't run my campaigns that way, if my players had no fun in them. We just like figuring out extravagant solutions to difficult problems, so planning and charater interaction take up most of our advantures rather than nuzzle flash action.



I am not negative about his bike. He asked why the rules to build it aren't available anymore and I gave him a reason. Aside from that I even gave him an option to achieve his goal despite the missing rules: to simly use the sparrow as a template and call it by a different name.

If you think my comment towards his picture was negative, then you misunderstood me. I think his drawing is awesome and I might even copy it for one of our more sci-fi rp sessions. That said, he pictured his thrusters as jet engines. They'd roast his legs off, while active. That's why I said that bike would kill him. I still think it looks awesome, though. I wish I had that artistic talent.

Oh, silly internets. Normally we need a *sarcasm* button; in this case I apparently needed a *not sarcasm* one. (IMG:style_emoticons/default/twirl.gif)

Yeah, if you asked for something like that in my game, I'd say maybe, Point out that JETS would fry you, and suggest something else as a mode of propusion, probably a prop based/ Super High Tech Ion drive.

Then, for stats, I'd go for a Similar Model to the Sparrow. Faster and less manuverable,

Something like
Entertainment Systems JetByke Handling +0 , Accel 15/40, Speed 110, Pilot 3 Body 4 Armor 2 Sensor 1 Available 12R Cost 20,000 (IMG:style_emoticons/default/nuyen.gif)

Actually, if you had maglev capabilities built into gridlink systems, you could have pretty much anything "flying" along no problem as long it it stayed to the main roads.

Why not have the front two thrusters being turbo fans and the back two thrusters being jets?

This way you can still have forward propulsion and not burn off your legs.

That would work.

Smaller turbofans for maneuverability and lift and a jet for forward propulsion

I figured the front jets would be angled down to provide lift, thus saving the riders legs and actually allowing this contraption to make some sense. (IMG:style_emoticons/default/smile.gif) (its a very good drawing by the way... did you draw it yourself Tsithlis?)

That works up until the moment you have to brake...

Hmm, good point.

It might work if you have Airbrakes and a possibility to reverse the jet stream akin to vector thrust nozzles on some modern fighter jets - just make sure it avoid the drivers feet.

Wow this thread sploded while I was away! Okay to clear up a few things about this image of the bike...

The front thrusters are pointed back at the legs of the occupant of the bike but are not active in that state. The front thrusters are rotary and rotate down to maintain stable lift during the bikes VSTOL operations (They can also be used in braking operations by rotating forward to slow the bikes speed). They are also used as air intakes to power two air thrusters that are located underneath the bike that maintain lift during its operations (hence the very large open intake on the front of the bike as well). The main power thrusters as can be seen are on the rear of the bike and expel most of the exhaust away from the bikes passenger. These create power and slight lift thereby explaining its operations as best as I can without being an aeronautical engineer. I tried to make the bike as realistically plausible in the future of 2070 as I could but I am neither a physicist or an engineer.

I am actualy not sure, if fighter jets can inverse their engine thrust. I know jetliners can, but their jet engines work on a different principle. I'd have to do some extra digging there.

All things considered, the health risks to the driver are not even the biggest cons of a jetbike. Maneuverability and fuel economy are.

To give you a (horribly scewed, but approximate) excemple: If you were to use enough JetCat P-200 jet engines (each an exhaust temperature of 630°C or 1166°F) and assuming the jetbike (without engines) weighs about 200kg (you can't use carbon or plastics because of the exhaust temperatures, so you're pretty much stuck with aluminium and titanium) and the rider with gear weighs about another 100kg (so no Trolls or heavy Orks here), you'd need approximately 15 P-200 jet engines to merely get it off the ground. We're not even talking forward movement, yet. And since the jetbike has no wings and as a result no uplift of its own while moving forward, you need to provide thrust downwards and forwards, to even get moving. So, let us be generous and assume a directly proportional distribution and simply double the required lift: 30 P-200 Jet engines.

That yields a final fuel comsumption of 21.9 l/min or 5.79 gallons(US)/min. SR4 assumes a 6hr operation time for each vehicle. As a result, the nescessary fuel tank would need a max volume of 7,884l or 2082,73 gal(US) or 49,59 bbl.

Also, keep in mind that we didn't factor in the weight of the fuel, while calculating the nescessary engines and uplift. To lift a 7 ton jetbike, you'd need around 330 P-200 jet engines... So even if we completely ignore the weight of the fuel, nescessary to operate the bike, the fuel consumption would still be around 6 gallons a minute. Now compare that to your average bike...

It should be pretty obvious, why a Jetbike has not been developed in a world that uses LAVs for military applications already.

Wait your complaining about how much a jet bike would take to get off the ground but you're okay with the fact that a MIG 67 is using what appears to be only 6 engines and is effectively a flying house?

I agree, and even LAV’s that don’t even have “Vertical Takeoff And Landing” are fuel guzzlers and require a landing strip to takeoff. They would most likely require even more fuel if they need to be able to hover.

Let us assume that the 60+ years of aeuronautic development would cut down on:
A: Improved Engine Power
B: Improved Fuel Consumption
C: Lighter Materials
D: Heat Resistant Non-Metal Materials

We could make it easy and imagine a -60% requirement but jet engines would be a stretch.

I we take your 30 jet engines as a requirement we could assume that we instead require 12 jet engines and 8,8 litres/min. This would still require a fueltank of approximately 3000 liters for a 6 hour operation.

I do believe it would be possible with small turbofans and electric engines that can (today) have incredible torque to get the turboprops up to speed and fuel consumption in fuel cells would be even less.

But yea, single human jet engines might be a stretch.

Makes we wonder how big feet you need to have those hoverfeet in augmentation…gotta be the size of tables to lift a troll…

The MiG-67 is a decaton military group transport with military grade vector thrust jet engines. Also, 6 engines is the minimum for the MiG-67, as we don't know whether or not it also sports additional englines beneath its hull for extra uplift.
If we considered 6 engines to be the case, the fuel consumption of a MiG-67 would average around 1.5 lb/lbf-hr with an plausible max thrust of somewhere around 270 kN (or the equivalent of around 1,300 P-200 engines).

You are not really trying to argue, that a BIKE (for crying out loud) can have the nescessary fuel tank to provide enough fuel to keep it in the air for more than just a few minutes. The MiG-67 is CONDSIDERABLY larger than what you are trying to build here, with a considerably larger fuel capacity and still piss poor fuel economy.

I can understand your desire on the basis of personal preferance. I can fully undestand your personal prference based on the visuals as I, myself think that picture looks awesome. I'd love to have jetbike like that, just for the looks of it. I can also understand that you are trying to make it fit within the SR universe.
But you can NOT expect anyone with at least an ounce of sense to consider your proposal plausible.

You asked why the rules weren't there anymore, I gave you the most plausible explanation. After that, I provided you with the means to still achieve your goal, within the limits of SR. But you are not content with a vehicle that looks like the one you want to have, but works on the mechanics of the sparrow. You really want a jet-bike. With real jet engines. And that is nonsense. It would be impractical, uneconomic, maneuverable as a brick and a direct hazard to the driver's health. Nothing you could POSSIBLY say will chage that fact.

Just use the base of the sparrow and be done with it.

I'm no expert on jet engines but I wonder if jet engines power output is equal to increase in size.

The output of an engine that is 10 times larger than another might be far more than 10 times the power of the smaller one.

Hence the 6 engines on a far larger vessel might be twelve to twenty times more powerful.

Way different, actually.

To give you a comparison:

JetCat P-200 RC Jet Engine: Max Thrust - 230N
Soloviev D-30KU-157 turbofan engine (MiG-31): Max Thrust - 103,000 N

So what are the usual Weight to Thrust Ratio then, is it linear?

How much does a JetCat RC jet engine weight?
And how much does a Soloviev D-30KU-157 turbofan engine weight?

Yes I know, I can probably find it on the net but...

Actually I think you are misunderstanding me, I am perfectly fine with using the sparrow and explaining that the lower thrust from the bottom of the bike that maintains altitude is similar to the fans of the sparrow. I was saying that the fact that they have made a small non-aerodynamic house vectored thrust seems just as implausible as a bike. Specifically with the same problems as the bike with maneuverability and stopping.

Well, they don't specifically say it is a JET POWERED vector thrust drone for example.

Even the NIMROD is pictured as having propeller based propulsion.

In fact i don't think ANY drone is jet powered in SR4, at least not through description.

Not to mention the Sparrow also says that it uses vectored thrust engines as well bringing up what exactly is vector thrust? I think this is causing a lot of the confusion I was stating vector thrust as being any engine that thrusts in a specific direction not necessarily rockets. The two engines on the sparrow are vector thrust engines yet they point directly at the driver and do not harm him.

*squints*

No, there are two large vector thrust turbofans on each side of the pilot. Neither fan points towards him. Since they are also large Turboprops and not jet engines they will only blow air close to him and not hot flames.

SR4 should clarify what they actually means in detail. We have several engine types to choose from and each vehicle should have a description of how it functions.

Propeller
Tilt Wing Propeller
Turboprop Vector Thrust

Jet Engine
Tilt Wing Jet Engine
Jet Engine Vector Thrust

Just to name a few