Vehicle Speed vs. Aerodynamics

[allanimal]

Without a faring of some sort 200kph is about the maximum you could handle but with clever aerodynamics it would be quite possible to get a lot more out of it; it's all about diverting the airflow around the rider and diffusing the base drag. 300kph? Easy. Modern street legal road bikes can get to that (just) and they have the added disadvantage of actually having to stay on the road.

That's true. Diverting the inbound airflow around the pilot provides for some protection. And that's when you'll start getting negative air pressure on the backside of your fairing, which will also cause pull on the driver/rider, though in a different direction. The faster you go, the more the negative pressure. It won't be nearly the same impact as forward-facing pressure, but it will be strong nonetheless, and if you provide air bleed inside that will get sucked out too.

Depending on how you design it, the less aerodynamic it becomes the more power you need to apply, and the stronger the materials need to become, which changes the flow and you have to start over again. With lots of power and super-strong materials you can overcome a lot. But at some point you no longer have a crotch rocket, you have a nearly fully encapsulated craft. So you might as well fully encapsulate it and gain much more speed and protection for the occupants.

But crotch rockets are all about feeling the air whipping in your face and laughing at the danger of riding something so fast with so little protection. Only wussies are gonna go with full protection!

All we need to get our TL-more-than-now Grav Bikes zipping along at 500kph without these aerodynamics issues is to install some sort of handwavium overthruster to compensate. Probably gets its mojo from the grav plates or something. And quantum flux. That is involved too. Look, I'm no physics expert, but I see guys flying these things at 500kph all the time out my starship viewport, and they are under control and not getting sucked out.

 

[phavoc]

So you are saying the Flux capacitor is real???? Way to go Marty! You made it back in time!

Of course we could do a hand wave and make anything work. It's science fiction, emphasis on the fiction part. But I think the idea was to make parts of it fit within an overall conceptual model that doesn't bend sciences today with the sciences of tomorrow.

 

[Libris]

Without a faring of some sort 200kph is about the maximum you could handle but with clever aerodynamics it would be quite possible to get a lot more out of it; it's all about diverting the airflow around the rider and diffusing the base drag. 300kph? Easy. Modern street legal road bikes can get to that (just) and they have the added disadvantage of actually having to stay on the road.

That's true. Diverting the inbound airflow around the pilot provides for some protection. And that's when you'll start getting negative air pressure on the backside of your fairing, which will also cause pull on the driver/rider, though in a different direction. The faster you go, the more the negative pressure. It won't be nearly the same impact as forward-facing pressure, but it will be strong nonetheless, and if you provide air bleed inside that will get sucked out too.

Depending on how you design it, the less aerodynamic it becomes the more power you need to apply, and the stronger the materials need to become, which changes the flow and you have to start over again. With lots of power and super-strong materials you can overcome a lot. But at some point you no longer have a crotch rocket, you have a nearly fully encapsulated craft. So you might as well fully encapsulate it and gain much more speed and protection for the occupants.

But crotch rockets are all about feeling the air whipping in your face and laughing at the danger of riding something so fast with so little protection. Only wussies are gonna go with full protection!

All we need to get our TL-more-than-now Grav Bikes zipping along at 500kph without these aerodynamics issues is to install some sort of handwavium overthruster to compensate. Probably gets its mojo from the grav plates or something. And quantum flux. That is involved too. Look, I'm no physics expert, but I see guys flying these things at 500kph all the time out my starship viewport, and they are under control and not getting sucked out.

Entirely my point. it's fair to say that we know a lot about aerodynamics at our current tech level but unforeseen developments have a habit of making the impossible entirely practical and with some active aerodynamics such as boundary layer blowers and active base drag diffusion - essentially eliminating the negative pressure on the rider - those strange looking bits and bobs at the front and that weird aerial thing actually operate to create a pocket of (relative) calm in air in which a rider can operate at what appear to be crazy speeds. Of course, if you don't have the reaction speed of a fighter pilot your career may be lot shorter than anticipated.

 

[phavoc]

Entirely my point. it's fair to say that we know a lot about aerodynamics at our current tech level but unforeseen developments have a habit of making the impossible entirely practical and with some active aerodynamics such as boundary layer blowers and active base drag diffusion - essentially eliminating the negative pressure on the rider - those strange looking bits and bobs at the front and that weird aerial thing actually operate to create a pocket of (relative) calm in air in which a rider can operate at what appear to be crazy speeds. Of course, if you don't have the reaction speed of a fighter pilot your career may be lot shorter than anticipated.

I can support that, so long as the illustrations and descriptions of these futuristic crotch rockets support that design. But everything you see is basically the speeder bike from Star Wars, or the grav bikes from Gypsy Knights 21 Vehicles supplement - and those bikes are crotch rockets with wind screens no bigger than what you might find on a Kawasaki Ninja today. And that disconnect is the problem. IF we are talking up bikes like that, then they need to have a reasonably lower airspeed to reflect things. But if we dip into the handwavium and create null-g force fields, or some other things BUT leave the descriptions towards what is in there, then yeah, I think that's a problem.

 

[-Daniel-]

IF we are talking up bikes like that, then they need to have a reasonably lower airspeed to reflect things.

I thought the speed of the bike had already been lowered to closer to the speed real bikes are going. Did they raise the speed again?

The real top end race bikes go more than 300kph. So I guess I am asking, did the G-Bike end up at Fast? If so, it's cruise speed "high" or about 200kph to 300kph an that is in line what real crotch rockets could do now.

 

[phavoc]

It was dropped to fast after discussion.

 

[-Daniel-]

It was dropped to fast after discussion.

That is what I thought, and it made sense. In my game, as long as they cruise with it, they will be fine. If they push the top speed of 500 kph then there will be issues. :mrgreen:

But everything you see is basically the speeder bike from Star Wars, or the grav bikes from Gypsy Knights 21 Vehicles supplement -

Fun side note, my favorite illustration of a Grav Bike is from the old DGP 101 Vehicles book. Fell in love the first time I saw it. I was driving a bike at that time so it was a great "fantasy" concept. They listed it as NOE= 160kph, Cruise = 225kph, Top=300kph. I wanted my character to have one so bad my friends felt sorry for me and made up some silly in game excuse for the crew to approve the purchase of a Cr171,600 GravBike. 8)

 

[phavoc]

DGP made some excellent quality supplements.

 

[-Daniel-]

DGP made some excellent quality supplements.

Amen to that. Sad that the present IP owner will not allow it to be shared, the original books are just too costly for me to even try and get what I am missing. Glad I have my 101 Robots and 101 Vehicles.

 

[phavoc]

DGP made some excellent quality supplements.

Amen to that. Sad that the present IP owner will not allow it to be shared, the original books are just too costly for me to even try and get what I am missing. Glad I have my 101 Robots and 101 Vehicles.

I'm tempted to make bootleg scans of mine... but I can't bear to take them apart. It's friggin hard to find some of them. I miss that attention to detail, even with some of the quirks.

Another SOM would be very welcome - provided it was of the same quality.

 

[Infojunky]

I'm tempted to make bootleg scans of mine... but I can't bear to take them apart. It's friggin hard to find some of them. I miss that attention to detail, even with some of the quirks.

Another SOM would be very welcome - provided it was of the same quality.

Are you sure You are talking about DGP? DGP was hit and Miss at best with some lovely art work conceptually stolen from ST:TNG..... Nearly everything that was Horked up in MT is directly relatable to DGP, We should have known too with the mess they did with Book 8. Though Grand Survey and Grand Census where good, so who was to know..... :evil:

"Edit Note; above is all opinion based on use of said materials"

 

[-Daniel-]

Are you sure You are talking about DGP? DGP was hit and Miss at best...

I can't speak to all of their products quality, but the few copies of The Traveller's Digest I owned were good. I also liked the two 101 books. I did sell most of what I had to a friend who was trying for a "100% of everything" collection. I am so glad I kept my 101 books though. :mrgreen:

 

[MongooseMatt]

Without a faring of some sort 200kph is about the maximum you could handle but with clever aerodynamics it would be quite possible to get a lot more out of it; it's all about diverting the airflow around the rider and diffusing the base drag. 300kph? Easy. Modern street legal road bikes can get to that (just) and they have the added disadvantage of actually having to stay on the road.

I am also thinking about about modern convertibles that allow you to have the top down but the wind does not mess up your hair. That is kinda what we are talking about, isn't it?

 

[Libris]

Without a faring of some sort 200kph is about the maximum you could handle but with clever aerodynamics it would be quite possible to get a lot more out of it; it's all about diverting the airflow around the rider and diffusing the base drag. 300kph? Easy. Modern street legal road bikes can get to that (just) and they have the added disadvantage of actually having to stay on the road.

I am also thinking about about modern convertibles that allow you to have the top down but the wind does not mess up your hair. That is kinda what we are talking about, isn't it?

Pretty much. On a lot of these cars there is no obvious reason that the airflow does that; it's basically advanced aerodynamics doing quite a lot with very little impact on the esthetics.