The Next Generation of Human Spaceflight

[GW Johnson]

93143: Did I understand correctly? You are describing a LOX-augmented nuclear thermal rocket vehicle, where the nuclear energy comes from a polywell fusion reactor? How is such a thing arranged?

[93143]

I would actually describe the system as a LOX-augmented nuclear electric rocket.

The version without LOX augmentation (ie: Dr. Bussard's ARC-QED rocket) works by running the LH2 through a cooling loop to carry away the waste heat of the reactor, and then injecting it into a magnetically-shielded 'combustion' chamber where it's heated by a relativistic electron beam powered by the reactor's electrical output (which is most of the total output, hence the high maximum Isp).

The question of whether the LOX gets injected before or after the REB-heating stage is largely a matter of practical considerations.

Now, one potential problem I see with what I've just done is that for normal heating modes, ionization is minimal, but with the REB you create a plasma. This is why the magnetic shielding works. (It also saps energy, so the high end of my Isp curve is probably too efficient.)

Hopefully the ionization can be kept low enough at lower temperatures that the LOX can actually add its energy (of combustion with the hydrogen) to the exhaust rather than just being extra reaction mass. At high values of the LOX injection rate, the REB doesn't add all that much extra energy anyhow, so perhaps its effects can be contained. The chamber temperature doesn't get much past 4000 K before LOX injection ceases to be useful, and if the chamber and nozzle are regeneratively-cooled they shouldn't need much, if any, magnetic shielding before then...

Perhaps the recombination rate would be higher if the REB-heated hydrogen spent some quality time at the chamber pressure before being mixed with the LOX? That way the temperature would be lower and the number density would be higher... it might make adding the LOX more difficult, though...

Or perhaps the ionized fraction would be high enough in practice to allow the magnetic shielding to work but not high enough to prevent the LOX from being useful - I don't know; this isn't my area...

It's distinctly possible that this system is unbuildable as described; I'm kinda new at aerospace propulsion engineering and I haven't exactly done a major design study... the main point was actually to demonstrate that an all-rocket Polywell-powered SSTO is not practical. Whether or not I've succeeded is left up to the reader...

[Diogenes]

Hell, since we're talking about propulsion, and since I like to throw out weird stuff for consideration, and since we kinda sorta want it linked to polywell in some way or other, I thought i'd throw this out.











It's an multiphase multistage Ionic wind propulsion system.

My calculations based on integration of this E along the flight patch show 6.27 times decrease of the power consumption as compared with the case when we would have corona wires in each gap, without decrease of force. The increase of efficiency becomes greater with d and less with r, it can be estimated as

To summarize, we can increase efficiency greatly without sacrifysing force – that means more compact design and finaly ability to lift power supply by a device of acceptable size. In fact my calculation shows that self-powered lifter with radius of 0.4m and hight 1m will be able to lift itself and 600gm power supply and 100 armature.

I've been keeping my eye on this thing for a long time. If I had time to screw with it, i'd like to do some experiments on this idea myself. It seems simple enough to put this apparatus together. I would power it with a resonant tesla coil with multiple taps for low and high voltage power sources. That would make the power source very lightweight and virtually unlimited for experimental purposes.

If the idea works, the thing would make a great observation platform with the advantage over an aerial drone in that it can hover stationary indefinitely. Park it right outside someones bedroom window if you wanted.

Seems like the idea might be possible to keep adding stages and make the thing supersonic. Seems so in theory at least.

[krenshala]

Diogenes, your images aren't showing up as I don't believe Tripod allows external links (I've seen this from a number of other images hosted there).

[GW Johnson]

93143:

That's a concept I had never heard of before, for sure: LOX-augmented fusion electric rocket. Wow!

Recombination. Hmmmm. I'm not very clear on your concept, but we hit smack into recombination problems pushing subsonic ramjet to Mach 6-ish. In fact, that is the subsonic combustion ramjet speed limit mechanism.

The nozzle converts thermal energy to kinetic energy at the expense of a pressure drop, but it does not convert recombination energy to kinetic energy. If the chamber temperature gets much over 4500 F (near 2000K) in the airbreather, we got serious recombination penalties. I think in the rocket scenario, this is probably nearer chamber temperatures around 6000F (near 3000 K), but I could be wrong.

For what you describe, I think you probably need a process to extract usable energy from the EB-heated plasma until it recombines, then put it through the nozzle, and burn with LOX if you like. Use the extracted energy in some way, like preheating the working fluid, so that this energy is not lost.

[Diogenes]

Diogenes, your images aren't showing up as I don't believe Tripod allows external links (I've seen this from a number of other images hosted there).

That sucks. They were showing up fine when I was previewing it. I'll have to do a work around.

[GIThruster]

They're working fine for me, though I should mention that all indications are, ionic wind can never be an efficient means of lift. Pretty hard to beat Bernoulli here. What makes you think multi-staging would make any efficiency difference? Are you familiar with the myriad of "Lifters" that have been built and flown based on ionic wind for propulsion? None of them are self-contained power source because the method is so inefficient as won't allow.

[GIThruster]

I would actually describe the system as a LOX-augmented nuclear electric rocket.

The version without LOX augmentation (ie: Dr. Bussard's ARC-QED rocket) works by running the LH2 through a cooling loop to carry away the waste heat of the reactor, and then injecting it into a magnetically-shielded 'combustion' chamber where it's heated by a relativistic electron beam powered by the reactor's electrical output (which is most of the total output, hence the high maximum Isp).

The question of whether the LOX gets injected before or after the REB-heating stage is largely a matter of practical considerations.

Now, one potential problem I see with what I've just done is that for normal heating modes, ionization is minimal, but with the REB you create a plasma. This is why the magnetic shielding works. (It also saps energy, so the high end of my Isp curve is probably too efficient.)

Hopefully the ionization can be kept low enough at lower temperatures that the LOX can actually add its energy (of combustion with the hydrogen) to the exhaust rather than just being extra reaction mass. At high values of the LOX injection rate, the REB doesn't add all that much extra energy anyhow, so perhaps its effects can be contained. The chamber temperature doesn't get much past 4000 K before LOX injection ceases to be useful, and if the chamber and nozzle are regeneratively-cooled they shouldn't need much, if any, magnetic shielding before then...

Perhaps the recombination rate would be higher if the REB-heated hydrogen spent some quality time at the chamber pressure before being mixed with the LOX? That way the temperature would be lower and the number density would be higher... it might make adding the LOX more difficult, though...

Or perhaps the ionized fraction would be high enough in practice to allow the magnetic shielding to work but not high enough to prevent the LOX from being useful - I don't know; this isn't my area...

It's distinctly possible that this system is unbuildable as described; I'm kinda new at aerospace propulsion engineering and I haven't exactly done a major design study... the main point was actually to demonstrate that an all-rocket Polywell-powered SSTO is not practical. Whether or not I've succeeded is left up to the reader...

SSTO doesn't seem to me to be the most urgent nor important application for a Poly. SpaceX is going to be launching for pretty darn cheap. What we really need is a thruster that can take us all around our planetary system. That's why I asked about using other gasses for airbreathing (which admittedly does seem to put you most of the way toward a SSTO solution).

Have you seen the parametric study done by USAF at Wright Patterson, looking at the DPF for use in what is essentially a starfighter, SSTO vehicle? I posted it at NSF about a year or so ago in the advanced concepts folder. If you search for the name "Frank Meade" you should find it.

That study found the DPF sufficient for SSTO.

[Diogenes]

They're working fine for me, though I should mention that all indications are, ionic wind can never be an efficient means of lift. Pretty hard to beat Bernoulli here. What makes you think multi-staging would make any efficiency difference? Are you familiar with the myriad of "Lifters" that have been built and flown based on ionic wind for propulsion? None of them are self-contained power source because the method is so inefficient as won't allow.

I had never read that inefficiency was the problem. Rather, the problem is that the lift of a single stage is just too small. That is why I find this multistage multiphase idea interesting. It *MIGHT* be possible to overcome some of the deficiencies with the idea by adding additional stages to create a stronger airflow.

The device is basically a linear ion accelerator. If subsequent stages produce a multiplication effect as opposed to an addition effect, the Idea ought to be workable.

[GIThruster]

You'll find the electrohydrodynamic force equation here:

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

Back when people were seriously posing an electro-gravitic linking, Lifters were quite popular. Wasn't very long until people put them in vacuum and found they don't then work so all you have is ion wind. Simpler still was put it in a box. Then you don't need vacuum.

IIRC, Lifters were one of the areas NASA explored during the Breakthrough Propulsion Physics Project and handily dispensed with as useless technology. Now if you think you have a work-around for the poor thrust efficiency with staging, they might make a comeback; but you'll need to show they're more efficient than ducted fans and you still have the downwash problem that makes them unsuitable for things like flying around in a city or lurking outside someone's window. Even with no moving parts, the downwash sufficient to lift a craft is going to be loud, and dangerous. Think of the trouble with the Harrier. You can't hover it over asphalt as it tears the stuff up and sends it flying at hundreds of miles per hour. Open blades as with a helicopter distribute the air stream over a larger area than the craft and so don't cause this particular problem.

[Diogenes]

You'll find the electrohydrodynamic force equation here:

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

Back when people were seriously posing an electro-gravitic linking, Lifters were quite popular. Wasn't very long until people put them in vacuum and found they don't then work so all you have is ion wind. Simpler still was put it in a box. Then you don't need vacuum.

IIRC, Lifters were one of the areas NASA explored during the Breakthrough Propulsion Physics Project and handily dispensed with as useless technology. Now if you think you have a work-around for the poor thrust efficiency with staging, they might make a comeback; but you'll need to show they're more efficient than ducted fans and you still have the downwash problem that makes them unsuitable for things like flying around in a city or lurking outside someone's window. Even with no moving parts, the downwash sufficient to lift a craft is going to be loud, and dangerous. Think of the trouble with the Harrier. You can't hover it over asphalt as it tears the stuff up and sends it flying at hundreds of miles per hour. Open blades as with a helicopter distribute the air stream over a larger area than the craft and so don't cause this particular problem.

The downwash problem is proportional to weight. Action and reaction. If the hovering device is light enough, the downwash won't be loud or even very noticeable. As for more efficient than ducted fans, I will show you this example of a real world test which indicates that they may very well be.

The tests showed that the ionic-cooling system extracted roughly 30 percent more heat from a laptop than a conventional fan and could potentially consume only half as much power. Aside from these efficiency improvements, the EHD system is solid-state, which means it has no moving parts and therefore no noise, while its decreased size and weight mean it is suited for thinner, lighter portable devices.

My understanding of the heat extraction is that ionic cooling punches through boundary layer conditions because the ionized air molecule will not stop till it acquires an electron from the cathode plate.


http://www.gizmag.com/an-ionic-wind-to- ... way/11797/

[hanelyp]

The tests showed that the ionic-cooling system extracted roughly 30 percent more heat from a laptop than a conventional fan and could potentially consume only half as much power. Aside from these efficiency improvements, the EHD system is solid-state, which means it has no moving parts and therefore no noise, while its decreased size and weight mean it is suited for thinner, lighter portable devices.

My understanding of the heat extraction is that ionic cooling punches through boundary layer conditions because the ionized air molecule will not stop till it acquires an electron from the cathode plate.


http://www.gizmag.com/an-ionic-wind-to- ... way/11797/

Sounds useful for convective heat transfer, but I don't see it applying to the production of lift or thrust.

[Diogenes]

The tests showed that the ionic-cooling system extracted roughly 30 percent more heat from a laptop than a conventional fan and could potentially consume only half as much power. Aside from these efficiency improvements, the EHD system is solid-state, which means it has no moving parts and therefore no noise, while its decreased size and weight mean it is suited for thinner, lighter portable devices.

My understanding of the heat extraction is that ionic cooling punches through boundary layer conditions because the ionized air molecule will not stop till it acquires an electron from the cathode plate.


http://www.gizmag.com/an-ionic-wind-to- ... way/11797/

Sounds useful for convective heat transfer, but I don't see it applying to the production of lift or thrust.

A single stage is useless, but if that cascade idea is workable, that may very well be a game changer. If you could stack stages, each one giving a pressure and velocity boost, then why couldn't you use such a device to compress air into the inlet of a ramjet?

Form the plates into tubes, and allow air to accelerate through them, mix with fuel and combust for additional thrust. A lightweight ram jet that will produce thrust at zero forward motion!

Just an idea.

[IntLibber]

Actually, the primary limiter on lifter thrust isn't inefficiency vis a vis a newtons per watt, but that lifters are power limited by the issue of arcing once you reach a given voltage level, which results in electrode erosion that is common to all similar thrusters (it would also help if your working fluid, air, wasn't an oxidizing substance). Only the VASIMR and the Hall thruster have been able to go beyond these power limits because they use electromagnetic rather than electrostatic fields to excite the working fluid.

A more powerful lifter would have an electron emitter at the intake, with sets of MHD coils to accelerate the ions in an insulated environment, preventing arcing paths from grounding out the plasma.

[Diogenes]

Actually, the primary limiter on lifter thrust isn't inefficiency vis a vis a newtons per watt, but that lifters are power limited by the issue of arcing once you reach a given voltage level, which results in electrode erosion that is common to all similar thrusters (it would also help if your working fluid, air, wasn't an oxidizing substance). Only the VASIMR and the Hall thruster have been able to go beyond these power limits because they use electromagnetic rather than electrostatic fields to excite the working fluid.

A more powerful lifter would have an electron emitter at the intake, with sets of MHD coils to accelerate the ions in an insulated environment, preventing arcing paths from grounding out the plasma.

I am thinking that people aren't getting the AC multiphased idea. Let's see if I can make the idea clearer.


Initially, you have a positive charged corona wire. It grabs electrons off of air molecules, at which point they become positively charged, and are repelled from the corona wire. They are attracted to the negatively charged plate some distance from the corona wire. As air molecules flow past the corona wire, they form a cloud of positively charged ions pushing neutral air molecules ahead of them in their efforts to get to the negatively charged plate.

When this cloud is half way to the plate, the voltage starts to decline to zero, and by the time they arrive at the plate, the plate is no longer negatively charged, but is mostly neutral instead. As a result, most of the cloud continues in the direction it was traveling, at whatever velocity it had when the charge turned off.

As the cloud is passing over the plate, the plate slowly swings positive, and the plate behind it is starting to swing negative, so the ionized cloud of air molecules is repelled from the plate it was once attracted to, and attracted to the next plate in the sequence, since it was already moving when this occurred, it is accelerated once more by the new potential differences between the next two plates in the sequence.

Now this idea has been proven to work in ordinary linear particle accelerators, the difference here is, you are trying to move a LOT of particles, instead of a tiny stream. Because of this, the timing and the potential differences and sizes and distances of the plates make it a bit tricky to optimize, but you should be able to seemingly keep accelerating the cloud of ions until they are finally ejected past the last plate at their maximum speed.

If you are unfamiliar with the principle of operation of this sort of linear accelerator, here is a diagram and a link for what I am talking about.



This idea works in exactly the same manner as this linear accelerator, but because it uses large clouds of ions mixed with neutral particles, the pumping frequency probably needs to be a lot less than RF.



http://en.wikipedia.org/wiki/Linear_par ... ccelerator


I'm kinda surprised you guys don't seem to be familiar with this stuff. Anyway, the point is, you DON'T have to use higher and higher voltages. A multiphase AC voltage will achieve whatever degree of acceleration that you want, you just have to get the timing and distances correct for the ion\neutral velocities involved.