/sci/ - Science & Math

>>9941272
How would even go to create a hoverbike? Plasma propulsion? Pic related is just a personal helicopter.

>>9941272
Implying actual engineers wouldn't be able to weld some tubes with two propellers and gasoline engines, come on man that's just a beautiful toy. Btw i love Colin Furze :)

>>9941277
It hovers. All the prototypes I’ve seen largely either hover with propellers or ducted fans

>>9941272
That shit doesn't even work.

>>9941319
Thats ugly and inefficient, why would you need to waste energy to stay hovering, you are not displacing vertically so W=0, theorically there it should be a way to hover for free.

Like planes, they only spend energy for travelling, but its shape makes it stay in altitude thanks to air, if planes needed energy to stay vertically we wouldnt reach shit

>>9941323
>Hovers
>Doesn’t work
What do you mean

>>9941272

We have the technology to build solid-state aerodynes aka electrostatic aircraft, yet choose not do because aircraft nuclear power is seen as ridiculous.

It is less about what is possible and more about what governments will safely allow.

>>9941380
>solid-state aerodynes aka electrostatic aircraft

source

>>9941380
For a given power to weight ratio, even before shielding, jet turbines win over nuclear, and they win hard. Nuclear power's advantage is endurance.

>>9941328
So? You're ugly and inefficient too, and everybody likes you just the same.

>>9941272
1. No demand. No, nerds who watched to much scifi are not a market
2. Dangerous to other people when used in populated areas. No way they will be allowed near cities or villages, we do not even allow drones over a certain size in cities because they can kill people if they crash or lose parts.

Same reasons why we do not have flying cars: It's not that we can't have them, we just don't need them.

>>9941489

It's the basis for ion engines which NASA uses in space. They aren't really usable in atmosphere due to the lack of a suitable power source.

https://en.wikipedia.org/wiki/Ionocraft

https://www.youtube.com/watch?v=dnPEgV_GFkU

>>9941536

First of all it's hard to know exactly how efficient nuclear would be since attempts to examine this in depth were ended in the mid-70s. Secondly the raw power density of uranium is greater than jet fuel, giving a theoretically larger electrical power source which could drive turbines or propellers (or ion engines) at higher speeds than their fossil fuel counterparts.

>>9941562

We don't have flying cars because there's no place to park them since getting a legal urban helipad built is a massive bitch and requires a lot of paperwork. The FAA's stringent pilot licensing program (including mandatory health checks) does not help. If getting a helicopter license only cost $100 and could be done in a few weekends, more people would get one.

>>9941564
>getting my hopes up with shitty ion wind lifters

I thought there was an actual development in that field or some shit.

Maybe one day we can brute force it.

>>9941272
>>9941319
>>9941328
>>9941338
It barely does anything simply because there's not enough power or power density to lift enough weight or produce enough force to properly maneuver in the ways needed for it to be useful. This is because it is horrifically inefficient in its design. Why? Because people want a "hoverbike" design for some tarded reason.

>>9941562
>Same reasons why we do not have flying cars

We have them. They are called, "helicopters," and, "aeroplanes".

>>9941566
>The FAA's stringent pilot licensing program (including mandatory health checks) does not help. If getting a helicopter license only cost $100 and could be done in a few weekends, more people would get one

This is a good thing. Fucked if I want Stacey getting her flying car licence and plowing into my house at 200mph because she was too busy applying lippy.

As much as Elon Musk is a meme he is absolutely right about taking transport underground, not overhead.

>>9941633
Everything needs to be underground. All utilities and transportation. Nothing more than an pedal car should be allowed above ground.

>>9941272
We already did it in the 50s. Pic related. It wasn't very practical as just like the presented hoverbike it barely flew out of ground effect and had limited speed.
>>9941277
>>9941380
>>9941564
>> plasma and electrostatic propulsion
I don't fucking get the purpose of using these exotic propulsion schemes. What's the advantage pf using plasma or ionic wind to move air over propellers? It's not going to be more efficient. It won't be quieter either because the flow will still need to be fast if we want our bike to be compact and fast flow tends to get turbulent and noisy. Electrostatic propulsion is certainly not compact either. Electrostatic propulsion has to be large because you can only use upto a certain electrical field strength before air breaks down and you get arcing.
>> nuclear power
Fuck no. To even get near the reactor you need assloads of shielding. That's going to be heavy. Even just making a nuclear powered drone would require a fair bit of shielding, because neutrons are so nasty that even the most rad hard of rad hard electronics only last weeks at most. Not to mention there are limits to how compact a reactor can be made due to the critical mass of fissile materials.
>> raw power density of uranium
Sure when used in nuclear bombs. In reality, practical machines don't explode or melt. And as of yet we can't practically convert fission power aside from using heat engines. We can only make heat engines, heat exchangers, and what not so compact today.

>>9941747

>What's the advantage pf using plasma or ionic wind to move air over propellers?

No moving parts meaning minimal maintenance cost for maximum durability. Devices can be used longer and in far more unforgiving conditions. The only thing stopping it is a suitable power source other than a small nuclear reactor or beamed energy.

>Fuck no. To even get near the reactor you need assloads of shielding.

You don't depending on the make, model, and size. Commercial electric reactors contain gamma radiation within their reactors because it means a more efficient power cycle. Whether or not shielding would be needed depends on the type of fuel/operation cycle chosen, and here it's pretty much impossible to know what exactly it would be since there is scant data on it.

>Sure when used in nuclear bombs. In reality, practical machines don't explode or melt. And as of yet we can't practically convert fission power aside from using heat engines. We can only make heat engines, heat exchangers, and what not so compact today.

Your car's engine explodes about 2-3 thousand times per minute and emits toxic carbon monoxide and dioxide into the atmosphere. This didn't stop adoption of them because they were more efficient than steam engines which burn their contents slowly instead of exploding them. Nuclear reactors neither explode nor burn their material, they fission it.

>>9941747
this

the way forward is more efficient engines and ultra light materials

>>9941874
>No moving parts meaning minimal maintenance cost for maximum durability. Devices can be used longer and in far more unforgiving conditions.

Except that's not even true. Plasma sputtering wears down the surface of whatever is containing it. You think high energy ions are just going to disappear?

> The only thing stopping it is a suitable power source other than a small nuclear reactor or beamed energy.

Also not true. You can build one and power it out of a standard wall outlet.

>>9941747

> What's the advantage pf using plasma or ionic wind to move air over propellers?

Neither of you guys know how plasma propulsion works. Plasma and electric propulsion don't move wind across propellers. They use high velocity ions as exhaust for thrust. By the way, even if you built a hoverbike with a hall thruster, you wouldn't even be able to get it off the ground.

Plasma and electric propulsion are super low thrust but incredibly efficient fuel wise. The amount of force a hall thruster has couldn't even knock over a jenga tower. That's why they're only used for satellite propulsion.

>yet another hoverbike thread

Holy shit, use a helicopter already and stop posting this shit over and over.

>>9941874
No moving parts does not necessarily translate to lower maintenance cost. You could still get things like bug strikes necessitating cleaning of the all the fragile electrodes and wires that ionocraft are typically made of. Also arcing can cause damage
>> the only thing stopping it is a suitable power source
Bullshit, for ionocraft it's their low thrust density. You just can't make as much thrust in the same area as a propeller no matter how much power you have. At some point air just breaks down and all your power goes through a few electric arcs damaging everything.

>> whether or not shielding would be needed depends on the type of fuel
All practical power reactors today use nuclear fission. Fission generates NEUTRONS and there ain't any way around this or it ain't fission. Neutrons are highly penetrating necessitating the use of lots of shielding.
>> fuel cycle
Doesn't matter worth a damn, all fission fuel cycles make NEUTRONS. And no, we sure as hell don't have scant data on fuel cycles. Barring exotic matter or fusion, no new fuel cycle will change the fact that atomic nuclei are small. Meaning we need to generate a shitton of neutrons just to sustain fission and that it will always be hard to shield stuff from neutrons
>>explodes about 2-3 thousand times per minute
Of course, but nuclear bombs are only able to explode once
>>9941910
I am assuming this massive brainlet was referring to ionocraft, which can generate enough thrust to knock over a jenga tower, but barely more than that. They work completely fucking differently than hall thrusters. You charge up air with a wire, this air gets attracted to a plate with opposite charge and bounces off. Pic related. They actually could be more efficient than jet engines in terms of power per unit thrust, however, they need a larger surface area to do so

There are also other plasma propulsion techniques out there for moving air in an inefficient manner, but they aren't worth discussing.

>>9941910
>>No moving parts meaning minimal maintenance cost for maximum durability. Devices can be used longer and in far more unforgiving conditions.
>Except that's not even true. Plasma sputtering wears down the surface of whatever is containing it. You think high energy ions are just going to disappear?
>> The only thing stopping it is a suitable power source other than a small nuclear reactor or beamed energy.
>Also not true. You can build one and power it out of a standard wall outlet.
>> What's the advantage pf using plasma or ionic wind to move air over propellers?
>Neither of you guys know how plasma propulsion works. Plasma and electric propulsion don't move wind across propellers. They use high velocity ions as exhaust for thrust. By the way, even if you built a hoverbike with a hall thruster, you wouldn't even be able to get it off the ground.
>Plasma and electric propulsion are super low thrust but incredibly efficient fuel wise. The amount of force a hall thruster has couldn't even knock over a jenga tower. That's why they're only used for satellite propulsion.

But you are comparing it like it was a jet turbine. What about generating a huge plasma cloud under the bike?

>>9942007
What a fucking bout it? For what purpose are you generating a huge plasma cloud under the bike? You have to explain your ideas. I am assuming you want a big cloud of plasma under the bike because you could potentially trap it in a magnetic field so you could have a hovecraft with a skirt made of plasma. Of course in order to be a concept of merit, one should provide some calculations showing that this can generate any force at all, and even better whether it generates enough force to overcome gravity given the strengths of magnetic fields we can produce today. Ignoring power, because we live in a world where we're willing to spend megawatts of power just so we don't have to use a propeller, we run into other issues like the fact we generate air pollution and the plasma may be hot enough to ignite the ground/vegetation. Yes we maybe have a different means of producing a force on our bike than moving air, and we could potentially use less power if we could magic away all the losses associated with using plasma. And by magic, I mean actual fuckin magic, cause that ain't fucking happening. In terms of other fucking crazy ways to produce an upward force on our bike, acoustic levitation has potential. Really only because we haven't worked out the limits of acoustic levitation in the far field. Also, sound transmission can be horrible fucking nonlinear, meaning you can get weird effects like sound turning into translational movement of fluid. (Acoustic streaming) Maybe by exploiting this phenomenon we could have our bike make a huge invisible propeller made of sound. It will still use as much power as a propeller, but now our bike can be more compact. Similarly, Terrence Tao has shown that in a toy model of the navier stokes equations we can make machines that can move energy around purely using fluid, which might also allow us to make invisible propellers.

>>9942160
Don't even bother reading this next bit cause it's fucking dumb. So there's this theorem(somewhere, I think) that you can extract an arbitrary amount of force from a photon bouncing between two mirrors so long as you get enough bounces and the mirrors don't move. So we scan the ground using a laser and use fucking crazy adaptive optics so that we shine another laser through them so that we can bounce this light off the ground and our device as many times as possible. We can already do shit like use adaptive optics and lasers to see through opaque media. We figure out some crazy transform through the media using our laser's known properties. Now hold my beer and buckle up this is about to get really dumb. So you say that photon rockets even with the best photon recycling still require ridiculous amounts of power to generate even newtons of thrust? So we use a quantum computer somewhere to uhhhhhhhhh.... compute quantum stuff so that the photons we emit aren't absorbed, and the ground 'looks' like a near perfect mirror. The magnitude of this perfection probably has to be in the range of ninenty nine point hundreds of nines past the decimal place.

I apologize for making you suffer through this, but some quantum physicist said that quantum computers are supposed to have sci-fi applications we can't even imagine. I certainly can't imagine this working.

WHAT IF you put half-critical lumps of a fissile material on the tips of a fan blade, and spaced other half-critical lumps around the circumference of the fan shroud. Then, when the fan was spun up, neutron flux in the gap between the lumps would heat the air and expel it to power the fan. If the fan is spinning fast enough, the lumps can be cooled after each pulse of neutrons.

>>9942227
I love it, I'll be patenting the design and suing you shortly.

>>9942227
>>WHAT IF you put half-critical lumps of a fissile material on the tips of a fan blade, and spaced other half-critical lumps around the circumference of the fan shroud.
so you've got weapons grade fissile material on a fan
>>Then, when the fan was spun up, neutron flux in the gap between the lumps
fucking how? If they're subcritical, it's going to be between fuck all an not much
>>heat the air and expel it to power the fan
you need to be a little bit more elaborate how you're going to heat the air and expel it to power a fan
>>lumps can be cooled after each pulse of neutrons
and just how are you generating these pulses of neutrons?
>>WHAT IF
So in the rare event you got this half fleshed out shit post to work, your device would emit copious amounts of fission productions directly into the air. This would be just like the windscale disaster on steroids. Oh and because you're making big giant pulses of neutrons, you've got a tiny neutron bomb going off with every pulse. So everything within about 25 feet of the device is DEAD.

Since you didn't flesh out how exactly you're going to generate neutron pulses or convert heat into rotation of the fan, I'm going to propose a similarly stupid idea. So nuclear powered ramjets have supposedly been generated, wherein thrust is generated via induction and compression of air through forward movement and subsequent heating of said air by moving it through a nuclear reactor. Now ramjets work most efficiently moving at supersonic speeds, now guess what also moves at supersonic speeds? Why the ends of helicopter blades of course! So what we do is simple we put our reactor in the center of a rather large propeller and put ramjets driven by nuclear heat on the blade tips. We provide this heat by ducting air through them into the reactor, then back out, or exchanging heat with them using say helium gas or supercritical CO2. Sure we could just put project pluto ramjets on the blade tips, but that' not doable due to their mass.

>mentions youtube channel
>doesn't post a fucking link
OP is a faggot, as usual.

https://www.youtube.com/watch?v=soxxPyaAT1k