Homepage Forums After Fusion Can a Focus Fusion rocket engine take us to the stars?

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  • #3510
    AvatarJolly Roger
    Member

    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.

    #3531
    AvatarTasmodevil44
    Member

    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. I know that when the Apollo astronauts visited the Moon on one of their missions, lunar dust was observed being kicked – up by the solar wind. Due to the Moon’s lack of atmosphere, it did not make dust clouds, but almost immediately settled back down again. But the magnetic bubble idea for utilizing solar wind as a possible supplement to an onboard fusion – powered thruster also sounds interesting. Both the thruster and the magnetic field bubble could perhaps all be powered by focus fusion.

    #3565
    AvatarJolly Roger
    Member

    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.

    #3573
    Avatarannodomini2
    Participant

    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.

    #3592
    AvatarJolly Roger
    Member

    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?

    #3614
    Avatarannodomini2
    Participant

    Jolly Roger 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?

    Edited to Add

    #3622
    AvatarTasmodevil44
    Member

    Come to think of it, there’s just no end to the creative ideas and ways you could possibly have hybrid FF reactor / other propulsion for a spacecraft to make it more flexible and versatile.

    #3648
    Avatarannodomini2
    Participant

    Tasmodevil44 wrote: Come to think of it, there’s just no end to the creative ideas and ways you could possibly have hybrid FF reactor / other propulsion for a spacecraft to make it more flexible and versatile.

    Its the holy grail of spaceship technology development atm, and electric based propulsion system that can get you into orbit.

    Ideally requiring no propellant.

    #3712
    Avatarsimulation11
    Member

    Jolly Roger wrote: 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

    Thank u so much. It’s quite interesting info. Barbarossa, wow it is the same name with my sister. 😉

    simulation rachat credit

    #3714
    AvatarAeronaut
    Member

    Jolly Roger 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.

    Thanx for explaining it more clearly than my texts, Jolly Roger. I was “thinking” I’d seen a typo.

    #3741
    Avatarpluto
    Member

    G’day from the land of ozzzzzzzz

    Magnetic reconnection in plasma jets get close to the speed of light.

    Could this be so for space ships?

    #3747
    Avatarjesims
    Member

    this is an interesting discussion.. thank you for sharing 🙂
    simulation rachat de credit

    #3751
    Avatarpluto
    Member

    G’day from the land of ozzzz

    Magnetic reconnection

    Magnetic Reconnection 2009
    http://arxiv.org/find/all/1/all:+AND+2009+AND+Magnetic+reconnection/0/1/0/all/0/1

    The topic becomes more interesting the more you read.

    That link show 2009

    Alter the year and it will give you that year.

    #3763
    AvatarBrian H
    Member

    A couple of points/questions:
    Tacking is not possible against the solar wind, because there is no parallel to a keel or water medium for the keel to push against. If you draw the forces that operate in sailing, you will see that the forward motion comes from pressure on the keel being pressed against water resistance at an angle to the incident wind. There is no water or equivalent to press against for a spacecraft.

    Second, I fail to see how any angle of a solar sail could slow the ship down (unless it is already heading inbound towards the source). The incident force is away from the sun/source; you can angle the sail to get some sideways pressure, but no possible angle gives you reverse pressure.

    #3767
    Avatarpluto
    Member

    G’day from the land of ozzzzzzz

    Sail is the slow way to china.

    Magnetic reconnection and the strorage of an ultra dense plasma matter in a magnetic confinement would be the ultimate power to go where no man has gone before, deep space far far away.

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