Difference between revisions of "Eddy Current Brake to Orbit"
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Setting down on the lunar surface by eddy braking has some advantages over using a tether. With a tether the vehicle to be landed must achieve the correct orbital speed at the correct position at the correct time to rendezvous with the tether and be dropped to the moon. With the eddy braking device only the correct position and correct direction of movement are required to properly enter the eddy braking device. It is much like landing an airplane on a runway. The differences are that an airplane does not have such a high relative speed to the runway, the runway is somewhat wider than the eddy braking slot, and the airplane must contend with varying wind conditions which would not affect eddy braking on Luna. Also for an eddy braking slot there is no requirement for super strong structural materials as for a tether. | Setting down on the lunar surface by eddy braking has some advantages over using a tether. With a tether the vehicle to be landed must achieve the correct orbital speed at the correct position at the correct time to rendezvous with the tether and be dropped to the moon. With the eddy braking device only the correct position and correct direction of movement are required to properly enter the eddy braking device. It is much like landing an airplane on a runway. The differences are that an airplane does not have such a high relative speed to the runway, the runway is somewhat wider than the eddy braking slot, and the airplane must contend with varying wind conditions which would not affect eddy braking on Luna. Also for an eddy braking slot there is no requirement for super strong structural materials as for a tether. | ||
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| + | If the orbiting tube imparts velocity to the shuttle at a rate of 30 meter per second per second, then the tube should be about 59 kilometers (37 miles) long. As with other low cost per unit mass systems of launching to orbit, a high mass rate of launch is needed to realize the low cost per unit mass. | ||
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Revision as of 06:57, 24 August 2012
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This works by having a long slotted aluminum tube in orbit and having the shuttle vehicle that is launched to orbit enter this slot while the tube is moving by at orbital speed. Magnetic flux from the shuttle is directed at the walls of the tube causing a repulsive force and a retarding force.[1] By reducing the relative speed of the orbiting aluminum tube and the shuttle, the shuttle is brought up to near orbital speed. Since eddy current braking loses effectiveness at low relative speeds, friction braking is used to give the shuttle the last 18 meters per second to reach orbital speed and match velocity with the aluminum tube. The aluminum tube requires electrically enhanced orientational stability which is achieved by shifting masses along the length of the tube to counter any tendency to pitch up or down. Electrically enhanced rigidity is achieved with electromagnets varying the tension on selected tension members in the structure as is determined to be necessary by continuous laser measurements. The structural material holding the aluminum in place varies from aluminum to steel as necessary to avoid having the speed of sound in the structure match the speed of the shuttle as it moves through that portion of the tube. This avoids having a destructive shock wave move through the structure. The tube requires high specific impulse electric thrusters to maintain orbital momentum when donating some momentum to the less massive shuttle. Thrusters of sufficient force are possible because they can be made very massive since they would not be supporting their own weight, just restoring the small number of meters per second the tube loses by interaction with the shuttle. This sort of device is possible for the moon, Mars, and Earth. A similar device would work for moving from orbital speed to a stop on the lunar surface. Replacing the simple aluminum of the tube with electrically conductive wires, insulation, and electrical power storage would recover some of the energy lost in the momentum transfer from the tube to the shuttle. This device could be built when it becomes economical to ship large masses of construction material from Luna to lunar orbit.
There have been objections to mass drivers because of large current switching requirements needed to have drive coils first attract the bucket then turn off to not retard the bucket on the way to orbital velocity. There is no such current switching requirement for the eddy current brake to orbit device.
Setting down on the lunar surface by eddy braking has some advantages over using a tether. With a tether the vehicle to be landed must achieve the correct orbital speed at the correct position at the correct time to rendezvous with the tether and be dropped to the moon. With the eddy braking device only the correct position and correct direction of movement are required to properly enter the eddy braking device. It is much like landing an airplane on a runway. The differences are that an airplane does not have such a high relative speed to the runway, the runway is somewhat wider than the eddy braking slot, and the airplane must contend with varying wind conditions which would not affect eddy braking on Luna. Also for an eddy braking slot there is no requirement for super strong structural materials as for a tether.
If the orbiting tube imparts velocity to the shuttle at a rate of 30 meter per second per second, then the tube should be about 59 kilometers (37 miles) long. As with other low cost per unit mass systems of launching to orbit, a high mass rate of launch is needed to realize the low cost per unit mass.
