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I'm trying to steer clear of neutron technologies so my coolant doesn't get activated. The Lead fisson reactor is becoming less attractive to me for this reason as alternatives look promising. Neither Hafnium isomer or photoalpha would suffer this problem.

 

On the subject of charging our hafnium batteries, the attached pic from Gamma-ray laser shows that the energy release from hf178m2 is in several separate photons of sub gamma energy. This is a clear indication that several intermediate quantum nucleonic states are traversed by the nucleus in transitions between ground state and the stable higher energy isomers. While charging hf178 to hf178m2 has been so far done by huge and inefficient high energy gamma sources with low efficiencies, I'm speculating that the best way of doing it may be with a rapid succesion of sub gamma photons of precise quanta equal to each rung in the ladder.:turtle:

 

No nuetrons? Are you talking about something like aneutroic fusion?

 

Michael

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What you describe is not predicted by classical physics. According to the basic laws of motion, if no outside force acts on the body, or the body doesn’t expel mass, it’s speed and direction won’t ch

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No nuetrons? Are you talking about something like aneutroic fusion?

 

Michael

 

Nope.

Hafnium has the most stable nuclear isomer known at 31yrhl. 2.8MeV can be stored and reused with photon triggering but quantum nucleonics is still young and its not quite feasible yet.

Photo triggered Alpha and Beta decay are also possibilities that the field may open up.

I'm more inclined to think that bleeding high energy Protons ~hundreds MeV from our magnetoplasma shields to trigger Fission of lead via spallation of neutrons (~500 per proton) is feasible now. I'm informed that lead fission has very low radioactivity in its fission products. Not real happy with neutron technologies, but the main thing is to not spew radioisotopes out the exhaust, and energy to accelerate reaction mass to relativistic speeds is better than thermal rockets even nuclear in terms of most utility of reaction mass.

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Nope.

Hafnium has the most stable nuclear isomer known at 31yrhl. 2.8MeV can be stored and reused with photon triggering but quantum nucleonics is still young and its not quite feasible yet.

Photo triggered Alpha and Beta decay are also possibilities that the field may open up.

I'm more inclined to think that bleeding high energy Protons ~hundreds MeV from our magnetoplasma shields to trigger Fission of lead via spallation of neutrons (~500 per proton) is feasible now. I'm informed that lead fission has very low radioactivity in its fission products. Not real happy with neutron technologies, but the main thing is to not spew radioisotopes out the exhaust, and energy to accelerate reaction mass to relativistic speeds is better than thermal rockets even nuclear in terms of most utility of reaction mass.

 

 

Why are you worried about radio active exhaust on a star ship? Space is already full of radioactivity, it would be like refusing to put a teaspoon of salt in the ocean. Why would helium three - helium three fusion not be a better energy source than the radio active decay of halfnium? Anuetrinic fusion leaves no radio active exhaust and produces no nuetrons to make anything else radio active. Helium three is available in the moons regolith. The fusion by products could be used as an ion drive and to produce energy for other reaction mass like ions of some other fuel. of course helium three fusion is not any nearer than dueterium fusion maybe not as near but neglible nuetron production is very atractive goal.

 

Michael

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Why are you worried about radio active exhaust on a star ship? Space is already full of radioactivity, it would be like refusing to put a teaspoon of salt in the ocean. Why would helium three - helium three fusion not be a better energy source than the radio active decay of halfnium? Anuetrinic fusion leaves no radio active exhaust and produces no nuetrons to make anything else radio active. Helium three is available in the moons regolith. The fusion by products could be used as an ion drive and to produce energy for other reaction mass like ions of some other fuel. of course helium three fusion is not any nearer than dueterium fusion maybe not as near but neglible nuetron production is very atractive goal.

 

Michael

 

Great addition, thank you.

we're still looking at particle energies of <30MeV though. And unlikely you can get them all going the right way, which means probably thermal particle velocities in exhaust. I'd like to see exhaust particle energies 100MeV to many GeV - near lightspeed with associated relativistic reaction mass enhancement. Still volume advantages may give you more thrust potential with thermonuke systems.

On the radioexhaust thing. Fine as long as its outer solarsystem to interstellar, but I'd hate to see radioactive exhaust used to get you out of earth solar orbit as its going to all end up re-entering, and we have to consider if we want to do that to mars or jupiter moons as well.

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Yes, it is interesting how much energy can go in. But it is rather difficult to get the energy back out in a usable form.
Most of the flywheel I’ve seen implemented or designed get energy out in the same way the get it in.

 

For example, the flywheel on a piston engine stores the energy generated by the expansion of gas in the piston (the power stroke) via mechanical force on the driveshaft, then exerts force in the opposite direction to turn the shaft and move the piston into position for the next power stroke (in the case of a 4-stroke engine, one-and-a-half revolutions, including a exhaust stroke). This kinetic energy storage system is critical in most piston engines – without a flywheel of some sort (which can be in the form of a single-function platter, or multi-function parts such as drive wheels or propellers), the engine can’t complete a cycle. The energy stored is relatively small, though, and the time it is stored very brief.

 

More advanced flywheels typically combine a platter with an electric motor/generator. When a voltage is applied to the motor, the platter’s speed is increased. When its circuit is open or zero resistance, it decreases only slowly, due to frictional forces. When resistance is put on the circuit, it supplies functions as a generator, generating a voltage, the platter’s speed decreasing. An example of one of the most advanced implementations of a system like this was the Chrysler Patriot hybrid-electric racing car, which used a vacuum-enclosed, 55,000 RPM carbon fibre/magnetic flywheel with magnetic bearings, the motor/generator coils on the outside of the vacuum enclosure. (see Great Moments in Science, Ep 33, 1997, or the post “Electric motors, gas turbine-generators, dangerous flywheels & the Chrysler Patriot”)

 

Development of the Patriot’s flywheel was halted around 1995, due mostly to concerns about the system’s safety. Safety is a major challenge in flywheel design. Mechanical failure, such as the flywheel breaking into fragments, can transform all of the stored energy into destructive kinetic energy similar to (but less precisely directed than) that of the projectile of a battleship gun, easily capable of killing people or even damaging or destroying vehicles and buildings.

Flywheels are great for storage of energy in a machine that can handle rotational motion, but a rocket engine is not one of those machines. There is no practical way of converting rotational momentum, however great, into propulsive thrust.
As described above, rotational momentum can be transformed into electric current. In the presence of even the very weak magnetic field, such as the Earth’s, this current can be used to produce electrodynamic force. The most developed implementation of this at present is, to the best of my knowledge, the Electrodynamic tether. Although at least one company has been formed to develop this technology for spaceflight (using solar power and/or chemical battery storage, not flywheels), it is still in the early stages of its development, with only a few preliminary experiments actually flown in space.

 

A limitation of electrodynamic spacecraft propulsion is its requirement of a sufficiently strong magnetic field. Given current material technologies, such systems appear capable of producing practical accelerations near bodies with significant magnetic fields, such as Earth and Jupiter, but not the Moon or Mars.

 

The 11069 thread proposes a very advanced kind of electrodynamic propulsion and storage system. In principle, such a system could store energy when descending onto the Earth’s surface, then expend the stored energy to ascend back into space, needing only to add energy to compensate for atmospheric friction and system inefficiency.

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Great addition, thank you.

we're still looking at particle energies of <30MeV though. And unlikely you can get them all going the right way, which means probably thermal particle velocities in exhaust. I'd like to see exhaust particle energies 100MeV to many GeV - near lightspeed with associated relativistic reaction mass enhancement. Still volume advantages may give you more thrust potential with thermonuke systems.

On the radioexhaust thing. Fine as long as its outer solarsystem to interstellar, but I'd hate to see radioactive exhaust used to get you out of earth solar orbit as its going to all end up re-entering, and we have to consider if we want to do that to mars or jupiter moons as well.

 

Actually studies have been done that show that exhaust particals in that energy range leave the solor system immediatly and could in no way contribute to any increase of radioactivity in space. Near earth space is already full of natural radioactivity much higher than anything you could produce. Thats why the space station has to be in low earth orbit.

 

Michael

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Is not nuclear fusion the cleanest burning nuclear fuel?

 

 

The type of nuclear fusion currently being developed (hydrogen 3 X hydrogen 4) gives off lots of neutrons, enough to make everything in the immediate vicinity, metals especially, radioactive. The best is Helium 3 X Helium 3 fusion. It give off only electromagnetic radiation that can't make stable matter radioactive. So it doesn't have any radioactive waste by products at all. Helium 3 fusion isn't being developed since deuterium x tritium reaction takes up almost all the grant money. Also it is assumed that Helium 3 fusion would be much more difficult than deuterium x tritium fusion.

 

Michael

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Thats a pretty impressive velocity at 3 000 000 m/s. Was that a linear electrostatic accelerator? I wouldn't have thought it was possible to get them that fast that way.

Still if we want to go faster than that then the most energy efficient way is seemingly even more eg/ at 0.9c our exhaust should be 0.9c velocity. I'm still not sure of what we need for good efficiency when slowing down from that sort of v. Relativity is so confusing.;)

Yes, linear electrostatic accelerator. Getting naked nuclei up to .1c is rather easy. The ion engine on NEAR was only about 2 feet long. :hihi:

 

getting up to .9c would take an accelerator about 20 feet long, judging from the one we had in the Physics building at the Univ of Alabama.

 

getting up to .99c would take a reeeeeeeeeeeeally long accelerator. This would push the mass of the total rocket so high that it might not be worth it.

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Yes, linear electrostatic accelerator. Getting naked nuclei up to .1c is rather easy. The ion engine on NEAR was only about 2 feet long. :)

 

getting up to .9c would take an accelerator about 20 feet long, judging from the one we had in the Physics building at the Univ of Alabama.

 

getting up to .99c would take a reeeeeeeeeeeeally long accelerator. This would push the mass of the total rocket so high that it might not be worth it.

so why not make a circular track?

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Actually studies have been done that show that exhaust particals in that energy range leave the solor system immediatly and could in no way contribute to any increase of radioactivity in space. Near earth space is already full of natural radioactivity much higher than anything you could produce. Thats why the space station has to be in low earth orbit.

 

Michael

 

Yeah thats probably true. Its only a rocket system of optimum energy efficiency that accelerates with exhaust velocity zero relative to its starting point. Using reaction mass to its best advantage is more important particularly when using nuclear techs that make e=mc^2 out of mass carried for energy production.

However.

"The solution to pollution is dilution" is the most disproved truism of our day arguably.

I'm for starting as you mean to go on.

I'm with jq Why can't we build up mass, energy and momentum in a synchrotron and use it for reaction thrust when we need big energy+ mass=acceleration?

something like this (pic).

If we kick particles neutral particles into it with some starting energy they could be stripped to electrons and + nuclei by the mag field and incorperated into the relevant charge/mass band. Varying the magfield in exhaust sectors would bleed some into exhaust streams.

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Yeah thats probably true. Its only a rocket system of optimum energy efficiency that accelerates with exhaust velocity zero relative to its starting point. Using reaction mass to its best advantage is more important particularly when using nuclear techs that make e=mc^2 out of mass carried for energy production.

However.

"The solution to pollution is dilution" is the most disproved truism of our day arguably.

I'm for starting as you mean to go on.

I'm with jq Why can't we build up mass, energy and momentum in a synchrotron and use it for reaction thrust when we need big energy+ mass=acceleration?

something like this (pic).

If we kick particles neutral particles into it with some starting energy they could be stripped to electrons and + nuclei by the mag field and incorperated into the relevant charge/mass band. Varying the magfield in exhaust sectors would bleed some into exhaust streams.

 

Has anyone checked out the nuclear fission plasma reactor I told you about? Here is the link if you want to see what the future really holds.NuclearSpace: Opening the Next Frontier pt. 1

 

Michael

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Yes, linear electrostatic accelerator. Getting naked nuclei up to .1c is rather easy. The ion engine on NEAR was only about 2 feet long. :turtle:

 

getting up to .9c would take an accelerator about 20 feet long, judging from the one we had in the Physics building at the Univ of Alabama.

 

getting up to .99c would take a reeeeeeeeeeeeally long accelerator. This would push the mass of the total rocket so high that it might not be worth it.

so why not make a circular track?
I'm with jq Why can't we build up mass, energy and momentum in a synchrotron and use it for reaction thrust when we need big energy+ mass=acceleration?
At first glance, I had the same thought – rather than struggle with the engineering challenge of building a long enough linear accelerator to accelerate our reaction mass particles to the desired Relativity-dilated mass, why not do what’s been done in so many existing particle accelerators to get very-high velocity particles, and accelerate them in a circle. If some sort of superconduction is used to create the magnetic field keeping the particles circling, excessive additional energy might not be used in this design (although loss from synchrotron radiation would be unavoidable) compared to a linear accelerator, and is could be more compact, and less massive.

 

However, despite accelerating its exhaust particles to great velocities, such a design would produce only a little thrust. Rocket thrust is due to the mutual opposite force of exhaust particles and the rocket motor. In a synchrotron, this direction of this force consists of 2 components, one tangent to, another coinciding with, the particle’s velocity, which varies as the particle travels in a circle. When the particle is finally “released” by switching off a section of the field keeping it on a circular path, only the brief period where the coinciding force was present and the tangent force not would produce linear thrust on the rocket. All of the rest of the thrust would be circular. If only one synchrotron was used in the design, most of the coincident force on the particles would cause the vehicle to change its angular, not linear, velocity.

 

A synchrotron could still be useful in relativistically increasing the rocket’s reaction mass, but the actual rocket thrust would need to come from a linear accelerator downstream of it.

 

It should be possible to calculate, given a few engineering estimates of synchrotron and linear accelerator masses, the energy efficiency, specific impulse, and other performance data to find a best performing combination of the two kinds of accelerators.

 

It seems to me that a “hybrid oval” kind of accelerator – essentially a synchrotron cut in half with a linear accelerator connecting the beam path between the two halves - might provide the best solution (see the attached sketch).

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Back in school, we had a little device in science class that blew my mind, and I can't remember what it's called (what with having a blown mind and all). But bottom line, it was a little four-bladed propeller thingy mounted inside a vacuum bulb, similar in size and shape to a light bulb. The one side of each propeller blade was black, whilst the other side was white. It hung on a magnetic pin, with very little friction. In any case, when you put that sucker in light, it started spinning. And the brighter the light, the faster it spun. It was awesome. But here's my point:

 

Instead of trying to accellerate ions, why not use some form of nuclear reactor to build up juice to fire the brightest and harshest possible floodlights available? You fire them away from your direction of travel - surely, there must be some kick there?

 

Or, alternatively, paint the whole spaceship black. Then, in the opposite direction of travel, you have a large white shield of some lightweight material. There's light all over the galaxy, but if you're close to a star, you'll get more oomph, obviously. But you should still be accellerating in interstellar space. Halfway through, you turn your shield around and start decelerating...

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Your reading my mind on the oval path Craig. I'm thinking for decent energy storage, contained mass capacity, and volume thruput for steady thrust, an oval track may be much better. Also I think electrostatic particle acceleration has some big limitations in these areas.

Not sure if its at all possible to move a magnetic field without physically moving magnets but if the straight (call them vertical for descriptive purposes) accelerator sections of our oval could have a lateral magnetic field that was rapidly raking through the charged particle columns, then velocity could be added to full circle columns of particles. You may even be able to take energy back out as electricity.

Perhaps current swirls orbiting around superconducting cylinders in the middle and outside the racecourse could do it. there would be speed limitations to this too I'm sure.

The angular momentum transferred to the ship by torquing up your particles would be balanced by 2 mirror racecourses. If you had three or more you could turn the ship any direction by unbalancing it. Letting the particles go as exhaust would give you linear thrust because the one of the 180 turns is eliminated in the exhaust particles track. The remaining one facing forward is turning the particle from travelling forwards at near c to rearwards with momentum result thats no longer cancelled by a mirror 180 at the rear. Force would be transfered by the turning magfield to the structure.

 

Moon, I still think thermal exhaust velocities are poo. Sure for an earth launched rocket you don't want high energy particles. The russian rocket motors used now by the americans with their oxygen pre heater systems give ~5x what any other chem rockets have achieved which is fine if you want rockets to lift mass from earth. They are reliable thanks to russian high temp metals, tho scary to contemplate since a bit of fuel is added to the liquid oxygen feed to preheat it. This resulting in bright orange-white glowing pipes feeding oxygen at hundreds of atmospheres pressure to the combustion chamber. Americans regarded this as impossible and never tried to develop it themselves.

Flying and magleving to orbit are far more efficient solutions than rockets will ever be.

If you want a fission deep space thermal rocket, the Nuke Saltwater looks good to me, get rid of the spent fuel as reaction mass. As you say space is full of radioactive stuff so no big problem as long as we don't all start commuting this way.

Boerseun, photon thrusters have enormous energy consumption for little thrust. They may be better as you approach c though.

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(Apologies for a slight threadjacking, but I can’t resist this, one of my favorite spaceflight topics)

Back in school, we had a little device in science class that blew my mind, and I can't remember what it's called (what with having a blown mind and all). But bottom line, it was a little four-bladed propeller thingy mounted inside a vacuum bulb, similar in size and shape to a light bulb. The one side of each propeller blade was black, whilst the other side was white. It hung on a magnetic pin, with very little friction. In any case, when you put that sucker in light, it started spinning. And the brighter the light, the faster it spun. It was awesome.
You’re describing a http://Crookes radiometer. (My parents bought me one in a planetarium gift store, and it was one of my most prized childhood possessions :D)

 

Its inventor, Crookes, believed its vanes turned due to the impact of light particles (ca. 1870, before quantum physics and the photon had been imagined). He was wrong, as was soon argued by people who noticed that, if that were the case, they would rotate away from the white side of the vanes (reflecting the particles gains twice the momentum of absorbing them), not away from the black sides, as actually happens.

 

What really makes the Crookes radiometer spin is heating of the little air inside the globe, which is greater near the warmer black sides of the vanes than near the cooler white sides. If made with a better vacuum, these little toys don’t have enough force to overcome the friction of their pin-on-glass bearings, and don’t work, though, in principle, if you could make the bearing low-friction enough, they would, turning backward from their usual direction.

 

Nonetheless, the idea of light-pressure propulsion is a valid one that can actually be measured by more precisely built devices

But here's my point:

 

Instead of trying to accellerate ions, why not use some form of nuclear reactor to build up juice to fire the brightest and harshest possible floodlights available? You fire them away from your direction of travel - surely, there must be some kick there?

This is known as a nuclear photonic rocket. It’s basic shortcoming is too low a power/mass ratio – the mass of a nuclear reactor is too great, and the force of light, too small.

 

This problem can be eliminated by having the harsh light stay put, and only the reflector move as part of the spacecraft. This is the essence of the space exploration scheme described by (and to a some extent patented by) the late Robert Forward. His designs ranged from tiny “Starwisp” probe spacecraft that could be propelled by microwave masers on Earth-orbiting solar power satellites that could serve double-duty to beam power to electric power plants on the surface, to massive, 3-sail designs to carry human explorers on missions to explore nearby star systems, powered by an array of thousands of Sun-orbiting lasers focused thought a moon-sized Fresnel lens.

 

I’m very enthusiastic about such systems, and have posted several times on the subject here at hypography. I highly recommend Forward’s writing on this and other spaceflight topics, particularly his alternating fiction/non-fiction book, “Indistinguishable from Magic”.

 

An obvious limitation of such systems is that the spaceship must trust the station beaming it power not to lose interest, funding, political stability, etc, and stop beaming power when and if its needed. This limitation has, I think, limited such systems popularity among spaceflight enthusiasts, many of whom are lone individualist types who imagine the role of interstellar spacecraft to be getting away from Earth before some calamity ensues.

 

The major technical challenge, after the preliminaries of building giant space lasers and lenses, is aiming them with sufficient precision to hit the target ship with a sufficiently narrow, intense beam at interstellar distances. Note that hitting a target with a roughly moon-diameter (3000000 m) beam at a 1-light year (about 10^15 m) requires an angular precision of 3000000/10^15 radians, or about .00006 arc-seconds. For reference, the Hubble Space Telescope, one of the most accurately pointable spacecraft yet flown, has a pointing accuracy of about .007 arc-seconds, 100 times too course.

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