[Jolly Roger]

zapkitty wrote: …how many useful things could be investigated without using a DPF at all?

My vision of the future my grandchildren will live in includes fusion-powered planes, trains, trucks and ships. 5 MW (and multiples thereof) would have applications in transportation, an energy-intensive sector of the world economy. Reduction in size and weight of auxilliary systems (ie capacitors, switches, shielding, etc.) would be needed. Research and Development in those areas would be useful.

P.S. It’s been a while since I last posted.

[Jolly Roger]

Transmute wrote: I can see how it could easily be used in the vacuum of space, but how could it operate in Earth’s atmosphere? Could it have a thrust to weight ratio high enough to get off the ground?

FF by itself may not have enough thrust for liftoff, but perhaps it could be used as the power source of some sort of plasma rocket that could. I also brought up the idea in another thread of an FF powered jet engine that could power a craft up to the edge of space.

And won’t the x-ray flux of a unshielded reactor have a huge lethal radius?

If it can’t be shielded because of the weight, perhaps it can be launched remotely from a ship far from land. If the craft is manned, or carrying electronics, it would at least have shielding between the engine and the crew cabin/cargo bay.

[Jolly Roger]

On the “Fusion for Waste Disposal” thread, the idea was brought up that using Deuterium as fuel for the FF would produce the neutrons needed to induce radioactive nuclides to a stable state.

[Jolly Roger]

Breakable wrote:

This fusion process involve neutronic fusion, not the aneutronic fusion/fission of Focus Fusion. FF could not be used for this unless alpha particles could be used instead of neutrons.

If you burn different fuel you get neutronic fusion.

True, I should have mentioned that. Deuterium or Tritium reactions yield neutrons. I understand that early FF tests will be with those fuels. If p-B11 doesn’t pan out, Deuterium could be a fall-back position. Deuterium could be used for radioactive waste disposal even if p-B11 does work, but definitely “NOT in MY backyard”!

[Jolly Roger]

annodomini2 wrote: Again interesting, would the charged particles from the solar wind be drawn into the the sail? And other matter around the spacecraft?

Just thinking if there is a need to carry mass to maintain the sail.

ETA: other than the power supply systems of course.

From what I’ve read, there will be some absorption of particles from the solar wind into the plasma sail, but not enough to make up for leakage. So, yes, there is still a need to carry mass to maintain the sail.

ETA?

[Jolly Roger]

Breakable wrote: There are two different processes:
http://en.wikipedia.org/wiki/Plasma_arc_gasification
disposes common organic waste by gasifying it into flammable compounds that is totally unrelated to fusion or nuclear waste.

There may still be some toxic substances remaining after the plasma process breaks everything down to basic atoms. Arsenic is still Arsenic, radioactives are still radioactive.

Another method is using fusion to burn up wasted fission fuel:
http://www.cosmosmagazine.com/news/2589/fission-fusion-hybrids-could-mop-nuclear-waste

This fusion process involves neutronic fusion, not the aneutronic fusion/fission of Focus Fusion. FF could not be used for this unless alpha particles could be used instead of neutrons.

[Jolly Roger]

Tasmodevil44 wrote: Hmmm …. all very interesting there, Jolly Roger. I may be wrong, but I always thought that the solar wind of charged particles also exerted pressure, same as sunlight. And that a sail could be used for either/both.

Sunlight has thousands of times more momentum than the solar wind. The thrust contribution of the solar wind on a solar sail is extremely small. The problem with a solar sail is that its size is limited by the weight of the sail material. A magnetic bubble sail does not have the same constraint, and can be expanded to the enormous size needed to catch the feeble solar wind.

[Jolly Roger]

What about Carbon-12? It is already an intermediate product in the reaction. What does additional carbon in the soup do?

[Jolly Roger]

I am buying an RV soon, and I would love to have appliances that run on AC or DC. If manufacturers made all appliances dual function, it would provide incentive to change the infrastructure to DC.

“Built it, and they will come!”

[Jolly Roger]

Sailing on the Solar Wind

Tasmodevil44 wrote: Or for greater versatility of propulsion, you could use a combination of focus fusion techniques, instead of just one. I still don’t know exactly what advantages such a system might have right off – hand, but what if you employed both a focus fusion laser for solar sailing, as well as an additional onboard focus fusion rocket or ion engine?

For a spacecraft, mass is our enemy. We want our spacecraft to have as little mass as possible. We won’t take a heavy fusion engine onboard if lighter thrusters will do. We want to leave the more massive components back at the space dock. That is where the fusion-powered lasers will be. However, an onboard fusion engine would provide additional thrust for acceleration and for deceleration at the destination and the thrust for the return trip. Just keep in mind that the engine, fuel and propellant all have mass that has to be pushed too.

Every time your solar sailing craft wandered out of the path of the fusion – powered laser beam, onboard fusion thrusters could also propel it back into the laser beam for additional thrust.

A 5 MW fusion engine would be overkill if used strictly as maneuvering thrusters, but if you have it onboard for additional acceleration and deceleration, you might as well use it. Also, remember that the laser beam travels in a straight line (usually), but the light sail craft travels in a curved path around the Sun. The beam will have to be continually aimed where the spacecraft is supposed to be when the beam gets there. Light is fast, but it is not instantaneous. It takes more than a second for light to travel from the Moon to the Earth.

Also, in sailboat sailing, there’s such a thing called tacking, where you can actually propel a craft upwind and against the wind. To do this, the sailboat has to travel in a zig – zag fashion back and forth. In a similar way, onboard fusion engine thrusters might be able to propel a craft back and forth in such a way as to catch the solar wind easier for traveling upwind against it. This way, you would have two methods of propulsion working together and assisting each other.

Solar sailing is not quite the same as marine sailing. For one thing, solar sails are not propelled by the Solar Wind (magnetic sails are), but by the pressure of sunlight.

For another thing, an unpowered craft is not motionless; it is in an elliptical orbit around the Sun. Adding power either speeds it up, causing it to spiral outward away from the Sun, or slows it down, causing it to spiral inward toward the Sun.

This can be done with thrusters, but for a solar sail, it is much easier to just change the angle of the sail to the Sun; one way speeds it up, the other way slows it down. This is how “tacking” will be done with a solar sail. There will be no “zigzagging”.

A solar sail has some serious disadvantages. It must be large, as big as a square kilometer, and made of a very light material. That material will be punctured by micrometeorites, which will reduce its ability to reflect sunlight.

The power of sunlight drops off with the square of the distance from the Sun. @ 2 AU it is 1/4 of what it is @ 1 AU, @ 3 AU it is 1/9, @ 4 AU it is 1/16, etc.

I much prefer a magnetic sail (Winglee’s M2P2, not Zubrin’s wire loop) to a solar sail. It is a HUGE magnetic bubble (10-20 km) inflated with plasma and propelled by the charged particles of the Solar Wind. It is impervious to punctures; an asteroid could pass through it with no problem.

It expands as it gets farther from the Sun, so the power it derives from the Solar Wind does not diminish with distance.

It is, however, dependent on the density and velocity of the Solar Wind, which can vary from 300 to 800 kps. It also leaks plasma.

A magnetic sail can be used in conjunction with a Plasma Beam, just as a solar sail can be used with a laser. One difference though is that a plasma beam will bend to follow a magnetic sail that drifts off course. A plasma beam may also be able to re-inflate a leaky magnetic balloon.

[Jolly Roger]

Jolly Roger wrote:

The maximum speed of the ship is not limited by the exhaust velocity as the action is relative… The speed limitation is mainly one of fuel, the ship will keep accelerating forever with infinite fuel and time, however as you approach the speed of light the net acceleration drops significantly as the relative mass increases.

My Bad! Thank you. I stand corrected. I was assuming that the equation for final velocity was:

Vf = Ve,

where Vf is the final velocity and Ve is the exhaust velocity.

The correct equation is:

Vf = Ve * ln(Mi/Mf)

where ln is the natural log, Mi is the initial mass of the ship, and Mf is the final mass.

I will do some calculations with various mass ratios and post my results later.

I kicked around a few numbers. With multiple stages, the ratio can get quite high. Then it turns out that the low acceleration becomes the limiting factor. Even at an almost respectable 0.6 m/sec^2, it would take almost 6 months to get out to my brown dwarf.

[Jolly Roger]

annodomini2 wrote:
The maximum speed of the ship is not limited by the exhaust velocity as the action is relative… The speed limitation is mainly one of fuel, the ship will keep accelerating forever with infinite fuel and time, however as you approach the speed of light the net acceleration drops significantly as the relative mass increases.

My Bad! Thank you. I stand corrected. I was assuming that the equation for final velocity was:

Vf = Ve,

where Vf is the final velocity and Ve is the exhaust velocity.

The correct equation is:

Vf = Ve * ln(Mi/Mf)

where ln is the natural log, Mi is the initial mass of the ship, and Mf is the final mass.

I will do some calculations with various mass ratios and post my results later.

[Jolly Roger]

Aeronaut wrote:
… Therefore, if 10 N= 1G of acceleration, a 100-ton ship would require only 1kN for 1G. For clarity, that would be tons of mass, not earth weight. 100 metric tons of mass would still be a sizable (and hefty) 1,000 metric tons or 3,200 tons (US) weight.

I don’t understand your math. I will explain mine.

1 Newton (N) of thrust will accelerate 1 kilogram (kg) of mass by 1 meter per second per second (m/sec^2).

10 N will accelerate 1 kg by 10 m/sec^2. 1 Gravity (G) = 9.8 m/sec^2, so 10 N/kg = 1.02 G = ~1 G.

1 metric ton mass is 1,000 kg, therefore it would take ~10,000 N (10 kN) to accelerate it to 1 G.

100 metric tons mass is 100,000 kg, therefore it would take ~1,000,000 N (1 MN) to accelerate it to 1 G.

The Space Shuttle has a mass of ~20,000 metric tons. It needs ~200 MN thrust for 1 G.

[Jolly Roger]

JimmyT wrote: … This technology does have waste heat. We believe that its overall efficiency will be on the order of 43%. That’s less waste heat than most heat engines, but still significant.

How did you come up with 43% efficiency?

An article on the Focus Fusion site states 80% efficiency is expected.

LPP Team Starts Looking at Ion-Beam Energy Extraction
by Admin on Mar 31, 2007 at 08:27 AM

Energy from the plasma focus will be delivered in two forms a burst of x-rays and an intense beam of ions. Extracting the energy from the x-ray burst by photoelectric means has been outlined in our patent application and it seems that a high efficiency, around 80%, will be achievable. We have now started to look at the questions related to extracting energy from the ion beam.

Since the ion beam is a pulse of current, the best way to extract energy from it is inductively, by essentially the same process that makes a transformer work. The changing magnetic fields produced by the rapidly varying currents generate electric fields that can move electrons in a coil. The energy in the current can then be captured in a capacitor. As the beam exits the coil, rapid-acting diamond switches can open the circuit to prevent the energy from leaving the capacitors.

However, the challenge in this process is that the electrons in the gas that the ion beam passes through are also capable of carrying the return current by moving in the same direction as the ions. If the electrons within the beam itself carry this current, it will short out the coil and no energy will be derived from the beam.

A preliminary analysis of this problem is now being carried out by Eric Lerner in cooperation with Dr. Roberts Terry of Naval Research Lab and Dr. John Guillory of George Mason University. We are just beginning this work, but a review of studies in the literature has come up with some initial encouragement. First studies performed at Sandia Laboratory in the 1990�s showed that when the density of the gas and the density of the beams are close, the beam can propagate in a self-pinched mode that preserves the ion current and prevents most of the electrons from catching up with the beam. This is because it is more difficult for electrons to move across magnetic field lines than along them. Other studies showed that if a coil or other conductor is placed close enough to a self-pinched beam, the return current will flow preferentially through the coil rather than the plasma.

We will continue to study this issue in greater depth. As our experiments develop they will also shed light on the ion beams, whose current is measured with a Rogowski coil.

https://focusfusion.pmhclients.com/index.php/site/article/lpp_team_starts_looking_at_ion_beam_energy_extraction/

[Jolly Roger]

Here is a site for scifi writers that has some interesting information.

http://www.projectrho.com/rocket/rocket3c2.html#table

It states that we may expect a Hydrogen-Boron rocket engine to have an exhaust velocity of 980 km/sec, thrust of 61 kN and engine mass of 300 metric tons.

We expect an FF engine to have a mass closer to 3 tons, but perhaps the other numbers are in the ballpark. If so, our spacecraft will have a top speed of 980 km/sec or 0.33% of the speed of light. I think that relativistic effects will be minimal.

With a top speed such a small fraction of the speed of light, extra-solar missions will be limited to robots, sleepers or generation ships. However, it should do fine for getting around the solar system, even out to the brown dwarf, Barbarossa, thought by some amateur astronomers to be orbiting the Sun, currently at about 218 AU.

http://www.metaresearch.org/msgboard/topic.asp?TOPIC_ID=770&whichpage=33

The critical factor then is the thrust. At 61 kN, our 100-metric ton ship will have an acceleration of 61 cm/sec^2. It would hit top speed in a few weeks, but it would still take 13 months to accelerate, coast/cruise, and decelerate to Barbarossa. A larger ship, with the 2,000 ton mass of the Space Shuttle, would take 25 months for the same journey.

The brown dwarf Barbarossa is not to be confused with the asteroid of the same name. Barbarossa may be the Dark Star Marduk/Nibiru that author Andy Lloyd is looking for.

http://www.darkstar1.co.uk/solution.html

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