FF for Jet Engines?

[QuantumDot]

you don’t need lead or heavy water for the radiation shielding, and well planes should probably have shielding anyway.

there is a company called radiation shield technologies which makes a product called demron which is made of a combination of plastics and organics and inorganic salts to create shielding from alpha, beta, low energy gamma and x rays.
http://www.radshield.com/

[Brian H]

zapkitty wrote:
…
Well, for the effect to work only a small portion of the exhaust needs to reach plasma… but it seems this might all be mooted by the invention of the plasma window.
…

?? That “invention” was in 1995 at Brookhaven. Not exactly new news that would moot anything by surprise!

Can handle up to 9 atmospheres; doesn’t seem like enough for the enviro of a jet engine.

[vansig]

zapkitty wrote:

i meant the THz laser beam

At what efficiency is the beam expected to operate?

To be determined. I don’t have detailed-enough spectral charts to assist with the task of optimizing it, and spectroscopy guys tell me to be prepared for the possibility that the data might not yet exist — so there’s science to do. The emitters would likely be a large array of nano-klystrons.

For comparison, quartz heaters are 85% efficient at heating objects *without* heating the air, but they operate as blackbody radiators, with bulge around 100 THz.

We’ll be looking for strong absorption lines for air, in the 1 to 6 THz spectrum, that remain strong over a range of temperatures from about 240 to 2000 kelvin.

Atmospheric pressure is ~0.01 bar at 35 km. We’ll want to know the path length for 100% absorption, here.

240 K is the inlet temperature at 35km altitude; and 2000 K is the upper bound to avoid production of NOx. Keeping this squeeky-clean on the environment sure would help to sell it.

2000 from 240 K is an 8:1 increase in pressure, as gas flows through the expansion tube. the scramjet design does not slow the gases. for low speeds, the air inlet shape might have to change to avoid back-pressure in the tube. there are several ways to accomplish this (including the plasma window).

Yes, this could go into a surface-to-orbit vehicle. Being an air-breathing engine while flying through atmosphere, it will really save on propellant. Mach-24 horizontal flight at high altitude is the magic threshold that will make it possible. We can expect, if this works at all, to see the classic shock diamonds characteristic of rocket thrusters and scramjets.

[vansig]

Brian H wrote:

plasma window

Can handle up to 9 atmospheres; doesn’t seem like enough for the enviro of a jet engine.

Do remember that 9 atmospheres is 0.9 million newtons per square metre. 🙂

That’s like supporting a 90 tonne vehicle on top of a 1m² window.

Seen head-on, a vehicle of this type might be reminiscent of a manta ray. With a huge mouth, its cross-section is mostly engine, in comparison to its airfoil and payload.

Attached files

[Aeronaut]

vansig wrote:

plasma window

Can handle up to 9 atmospheres; doesn’t seem like enough for the enviro of a jet engine.

Do remember that 9 atmospheres is 0.9 million newtons per square metre. 🙂

That’s like supporting a 90 tonne vehicle on top of a 1m² window.

Seen head-on, a vehicle of this type might be reminiscent of a manta ray. With a huge mouth, its cross-section is mostly engine, in comparison to its airfoil and payload.

Sorry, I’m still not seeing how the compression is achieved without the compressor stage fans. A Blended Wing Body (BWB) architecture may be easier to engineer for mach 24…

[QuantumDot]

the British recently created a UAV with plasma actuators, which can save about 10 percent of the weight of a plane, while the current design tested will not work at high speed( above mach 1 ) there is a another design that will work at hypersonic speeds, the current problem is the amount of energy needed to make it work which wouldn’t be a problem with a DPF, a sophisticated design is believed to be able to reduce drag by 30 percent and reduce heating from drag by 50 percent.

as to the propulsion design Richard Dell who is working on a polywell design with George Miley think that they have created a magneto hydrodynamic vertical takeoff system. which would work something like the propulsion system for the “Red October” in that it would ionize the air then using electro magnets create a suction force on the air and then again use magnets to keep the air from hitting the sides of the drive to help keep them cool, so imagine a funnel, that is how it will compress the air without fans. depending on the design it might compress a large amount of air to a near liquid before expelling it from the rear of the engine.

http://nextbigfuture.com/2011/01/richard-dell-who-is-developing-nuclear.html

[vansig]

Aeronaut wrote:
Sorry, I’m still not seeing how the compression is achieved without the compressor stage fans. A Blended Wing Body (BWB) architecture may be easier to engineer for mach 24…

BWB is even-more like the manta ray shape, true.

Well, SR-71 design is clear, but tops out at about Mach 3.2. How’s compression achieved in existing scramjet designs?
Isn’t this done by manipulation of shock waves?

By the way, this book has a section on scramjets, that mentions how electricity assists present designs:
Low temperature plasmas: fundamentals, technologies, and techniques edited by R. Hippler
— http://tinyurl.com/6d2vcxw

What we need right now is a team of Maxwell’s demons, to open the window for particles traveling in preferred directions only. 😉

I’m brainstorming, that the doppler effect will help: the emitters will be carefully tuned and focused, so that particles moving the wrong way through the engine are slowed, and particles moving the right way are accelerated.

Oh, and I like vortices, too. If we use them, then this should be a twin-engine design, for stability.

[Aeronaut]

My understanding of current scramjet designs are that you need a turbine engine to get the bird moving fast enough to create the compression required by the ramjet’s constricted wall design. The ramjet would in turn accelerate the plane to scramjet speeds in production birds. X-series birds ride a rocket to the required speeds.

The magnetic approach sounds ‘good’ to me, but like with a polywell, beware the magnets’ weight and expense.

[QuantumDot]

a British company named magnifye have created a way to make superconducting magnets that are a ten times more powerful then some of the best and about 2 million times smaller.
http://www.magnifye.com/

researchers at the university of Texas have learned how to create carbon nano tubes that can be used to create wires of various compounded, including superconductors, and they would be pliable.
http://www.technologyreview.com/energy/27039/?mod=chfeatured

a Japanese researcher has used red wine to create a superconductor at a much higher temperature using FeTe0.8S0.2 by sealing iron (Fe), tellurium (Te) and tellurium sulfide (TeS) powders into an evacuate quartz tube and heating the mixture at 600°C for 10 hours.
http://www.physorg.com/news/2011-01-hot-booze-material-superconductor.html

so within 5 years i would expect the price and size of superconductors to decease radically.

[Henning]

QuantumDot wrote:
a Japanese researcher has used red wine to create a superconductor at a much higher temperature using FeTe0.8S0.2 by sealing iron (Fe), tellurium (Te) and tellurium sulfide (TeS) powders into an evacuate quartz tube and heating the mixture at 600°C for 10 hours.
http://www.physorg.com/news/2011-01-hot-booze-material-superconductor.html

But that’s just rising the temperature from 2K to 8K (at least as I’ve seen from the graphs): http://arxiv.org/ftp/arxiv/papers/1008/1008.0666.pdf

[Aeronaut]

Looks like Magnifye may be on to something. I was looking for a cryo-plant like PW is currently going to need.

[zapkitty]

Returning to the fray after a severe bout of what was probably stomach flu… probably…

to recap: vansig wants fusion-powered jet engines because that can lead to supersonic flight and from there to spaceplanes.

That’s ok because currently projected FF units… even vansig’s massively ganged units… will not be able to compete economically with chemically fueled supersonic military combat units. And there still isn’t much of a market for supersonic cargo flights.

I believe that first subsonic and then high-subsonic passenger and cargo flights will be dominated by the fusion-powered propfans I have described.

In seeking ways to transfer energy from a notional array of FF units to the airstream vansig has proposed laser heating using a terahertz beam.

I have proposed using the alpha beam directly from the FF array directed through a plasma window into the airstream.

As a baseline Lerner-hakase proposed using a relativistic electron beam (REB) for heating propellant.

The first thing that must be addressed is the efficiency of the heating. A Thz laser is not very efficient. A free-electron laser tailored to operate in the precise Thz-range frequency desired might be as much as 40% percent efficient in transferring energy from its electron beam to its laser output…

… but then how are you ever going to catch up to the efficiency of just using a straight REB for heating? Not so good.

other issues…

Brian H wrote:

plasma window

Can handle up to 9 atmospheres; doesn’t seem like enough for the enviro of a jet engine.

Depends on the jet engine referenced. 10-40 bar is a common pressure range… 140 psi is respectable.

And the FF-powered unit has a huge advantage over traditional burners that might not be immediately apparent: the heated air does not have to give up any of its energy to power the intake compressors and auxiliary gear. Powering such takes upwards of 75% or more from the output of a standard jet engine.

75%.

FF don’t do dat 🙂

Past experience has proven that 140 psi can take us supersonic, given time, and scramjet design is all about maintaining combustion in a suprsonic airflow… and FF ain’t gots combustion either.

So it seems to me that the question now goes back to direct alpha heating vs REB heating… but did I miss anything?

I’ve taken a few preliminary cuts as to what might be involved in REB vs. direct alpha, but let’s make sure it’s on the right track to begin with 🙂

[QuantumDot]

Well the first question should be if you are going for Constant Pressure Combustion or Constant Volume Combustion.

Constant pressure combustion is the current method of propulsion used.
Constant volume combustion is currently under research and is often called pulse detonation engine and its theoretically able to give better performance, the current problems are powering the detonation, and constructing a tube that can survive the detonation for any length of time.

one way for Constant pressure combustion would be to use carbon nano tubes to ionize the air and then use a MHD drive, it would work at subsonic for supersonic you would need something more to ionize more air faster.

the REB and direct alpha could both be used for either propulsion method based on the engine design.

[zapkitty]

QuantumDot wrote: Well the first question should be if you are going for Constant Pressure Combustion or Constant Volume Combustion.

… errrrrrr… I think we’re going for the No Combustion option 😉

[zapkitty]

As with my previous musings on spacecraft power generation and fusion-powered aircraft this will assume that the FF fusion power generator proves out and operates on aneutronic proton-Boron 11 fuel close to the currently hoped-for specs.

But unlike the propfan aircraft proposed earlier for cargo and passenger transport this time we want to see what what would be needed for jet-like engines to be implemented around an FF powerplant. Jet-like in order to enable supersonic flight as the first step to orbital flight.

It gets interesting as many of the assumptions that govern the design of current jet aircraft apply themselves very differently to a fusion-powered craft… or do not apply at all.

Also of interest is the fact that many of the standing assumptions about handling nuclear fission power plants in aircraft also turn out to have radically different implications when applied to aircraft powered by aneutronic fusion.

As a useful set of parameters to shoot for in this first cut I’m vaguely thinking of an aircraft that is between the SR-71 Blackbird and Reaction Engines’ Skylon spaceplane in size and capability.

If we can show that FF can get a few people and a few tons of cargo first supersonic and then into orbit that will be sufficient proof-of-concept for now. The single-stage-to-anywhere interplanetary cruisers can follow later 🙂

First up: safety.
Given the essentially unlimited power provided by FF I do not see any real advantage in trying to leave shielding off just to save a few tons in mass.

In fact design and implementation becomes much easier if one not only starts out with standard FF shielding but embraces it to the point where a flying FF unit is essentially as well-protected as a nuclear waste transportation container… only without being nearly so toxic and radioactive.

Then the FF craft can take off, fly amongst other aircraft, fly to orbit, dock with spacecraft and stations, undock, enter atmosphere, approach an airport, land, taxi, and enter a hangar… all without any concern at all as to where the engines are in relation to anyone else.

And not incidentally things are much cheaper that way 🙂

A standard jet engine:
In a standard jet engine a compressor stage pulls in air in front and feeds that air to a “burner” stage or “burner can” along with jet fuel. The fuel is ignited and the combustion and the combustion products heat the remaining air. All this heated material attempts to expand but finds it easier to escape to the rear of the engine. It becomes the jet exhaust. Along the way additional incoming air can be entrained with the exhaust, lowering the exhaust velocity but increasing the total thrust of the engine.

All this occurs at subsonic air velocities inside the engine. Even supersonic aircraft with ramjet engines must slow the incoming air to subsonic speeds at the engine intake before attempting to burn fuel in the airstream. This deceleration of air at engine intakes is a real drag (pun intended) and is a major source of unwanted heating in supersonic aircraft. And it is also why scramjets are seen as a way to true aerospacecraft. A scramjet (supersonic combustion ramjet) allows the engine to burn fuel in a supersonic airstream inside the engine. It’s not easy to do.

Another proposed solution to the engine airflow drag issue, and one that is very relevant to an FF-powered jet engine, is magnetohydrodynamics. MHD is hoped to enable conventional turbojets to reach hypersonic speeds… without needing supersonic combustion.

In these aircraft MHD generators are to be used to absorb the energy of incoming air, converting that energy to electrical power and slowing the air to speeds a conventional jet engine can handle. Once the air has been through the “burner” in the engine the MHD would take the electrical power it absorbed from the incoming air and accelerate the exhaust as it exits the engine. An energy transfer.

I believe that’s a recap of where we are starting from… might as well be as the forum chopped the rest of my post for length 🙂

… to be continued…

[Author]

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