Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Interstellar travel/centrifugal couching

  1. Mar 1, 2017 #1
    Given: original project Orion https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

    My idea is the addition of a centrifugal couch to regulate gravity to crew during the acceleration and deceleration phases of the trip.

    The Orion concept, for an interstellar ark concept, relies on an ablative pusher-plate system to act as a shock absorber and provide some relief to crew from g forces during the beginning and end phases of the trip.

    I want to add the centrifugal couch to this. Picture a steam locomotive. The track is the path the ark takes on its' journey. The steam in this metaphor is from the detonation, and the detonation force on the pusher plate pushes a ram that works to rotate an arm that rotates around a fixed point in line with the direction of travel. The arm is configured so that it rotates on an "axle" connected to other components that contains ark modules that are not as sensitive as biologicals to extreme g forces. There are thus multiple "arms" rotating in space, an even number of them, revolving counter to one another to negate possible yaw effects from rotation forces in space and vacuum.

    Similar to the steam locomotive with the buildup of steam pressure turning the wheels, the detonation in a Project Orion ark occurs at a point in time mechanically where the crew compartment attached to the end of the rotating arm in space achieves a constant gravity during rotation, and thus the rotating body translates fore and aft acceleration into centrifugal force that can simulate gravity in the crew compartment. I believe that the release in steam used to power a locomotive can roughly instruct a centrifugal couch concept that creates artificial gravity for crew and increases comfort during transition phases.

    The pusher plate would accept force from the detonation, and would relax once the detonation forces subsided. This ram would cushion forces for cargo, but the centrifugal couch I believe would further dampen those forces to increase survivability and comfort for crew. Currently, the concept would call for detonations every ten seconds for 30 days straight on both ends of the journey. The detonations for this timetable and this acceleration would yield 4 gees of force with each detonation for the crewed ark.

    I guess the question here is would the centrifugal couch concept relieve g force strain on the crew mechanically? Instead of whiplash and sleep deprivation every ten seconds for a month, is it possible to mechanically divert the forces into a rotary motion that solves a problem (whiplash, artificial gravity) and increases comfort? Or are we seriously talking about a 30 day medically induced coma so the crew can transition without becoming insane?

    I also have some ideas about rotary regulators for the concept that derive from analog, steampunk technology that would divert a small portion of the force of each detonation to regulate the rotary speed of each armature as a robust and reliable inherent design feature.
  2. jcsd
  3. Mar 2, 2017 #2


    User Avatar
    2017 Award

    Staff: Mentor

    You have to reduce the peak acceleration felt by the crew. The pusher plate does this in the best possible way by leading to a constant acceleration, or at least a constant acceleration as long as possible if heat limits the explosion rate too much. Letting something rotate will increase the peak acceleration, no matter how you do it. Letting smaller things rotate inside a larger structure also leads to a huge overhead in terms of structural mass.

    If the detonations have to be spaced out too much to provide a constant acceleration, you can stop them for 8 hours per 24 hours. It won't have a significant impact on the overall journey time, but it will lead to a better sleep.
  4. Mar 2, 2017 #3


    User Avatar

    I have trouble visualising the geometry from the description.
    It seems unlikely that circular motion linked to a sort of crank will be able to completely eliminate the pulsing of the thrust.

    I wonder if you are proposing a design that needs less damping mass than the Orion "pusher plate"?
    The Orion concept used a massive pusher plate as both damping mass and shielding. Does your design need less shielding?

    It is always possible to provide much more springing and pulse smoothing for a bed, inside the craft.
  5. Mar 2, 2017 #4
    If you can picture one of those dumb lawn ornaments, the duck with the spinning wings, and then put your pusher plate on the back of the duck. The crew is in the area near the ends of the wings. The duck would then be everything else in the craft.

    The first post response is probably right on here, which leads me to try and come up with a variant that involves scoping the armature, or at least come up with a better visual guide.

    The duck imagery works, so take your lawn ornament and duct tape a plate to its rear end and that's your pusher plate. Put your crew in solo cups duct taped to the ends of the wings. Is there a geometry for the swinging of that crew capsule attached to that armature that allows more force to be applied while reducing the effect on the crew?

    The circular rotation creates artificial gravity but the first response is right, no matter what the timing of the rotation it just translates force into a force that pulls down (out from the center point) or out from the central point. Can that armature be configured into one that scopes, to increase and decrease its' length in a sequence timed according to detonation?

    Felt g effect is always reduced when the time of the effect on the object is increased relative to force applied. So if the detonation occurs at the appropriate time in the sequence, by my reckoning just as the rotating capsule passed through the point facing the direction of travel, and then as the armature rotates past about 80-90 degrees from this point, it begins to dramatically lengthen to a point where maximum length is achieved just after the rotation reaches 180 degrees from direction of ark travel. Then the armature begins to contract, creating an ellipse.

    As close as I can get with an analogy is to rip a tetherball pole out of the ground, turn it on its' side, mount it on a headache rack on a pickup truck, and spin it around the pole as you slam on the accelerator on the truck. It makes sense that a simple rotary motion would crush an occupant on the backside. But now replace the tetherball rope with something approximating a spring, maybe like an old telephone cord. You only dramatically accelerate when the ball is near the hood ornament. Then the craft relaxes and the ball stretches the spring until it passes the trailer hitch. Then the spring relaxes and it returns to the position out front, where another acceleration happens and the cycle repeats.

    Does the length of the armature spring significantly dampen g force? I know that it will add mass to the craft, but if the spring armature does a good enough job dampening acceleration loads felt by crew, then acceleration can be increased and the ark can be accelerated more rapidly while the crew doesn't have to endure the increased force. What might explain that dampening effect, if any?
  6. Mar 2, 2017 #5
    I added an analogy of the duck lawn ornament on the other reply. So the ark is the duck. The pusher plate is the plate that's duct taped to the back of the duck. Take the wings off and put little solo cup crew modules on the ends of the armatures. Your answer makes sense. It crushes the crew on the backside of each acceleration cycle.

    So throw the lawn duck in the trash and replace it with a tetherball pole. Yank the pole out of the ground and lay it on its' side on the headache rack on top of a pickup truck. Replace the rope with a spring. Spin the ball around the pole. As the ball passes the hood ornament, with the rotation plane parallel to direction of travel, the spring is relaxed, and then slam on the accelerator. As the ball rotates to 180 degrees from direction of travel, it stretches to maximum length, dampening felt g effect on the ball (crew compartment) when it passes the trailer hitch, before returning to the front, relaxed position near the front of the truck (ark).

    I asked on the other post if the maximum length of the armature is relevant to measuring felt g force experienced by the crew, since g is just force over time, so spreading out force over time would help? Does an ellipse achieve this?

    And in our ark, would it be wise to expend this type of mass on an exterior, rotary armature, or waste even more mass encapsulating a compartment inside a hollow elliptical shell? The trade off would be less felt g on crew for a given rate of acceleration, or the same felt force for even more acceleration per cycle. The crewed Orion would take MUCH longer to get it up to speed, because the crew absolutely cannot sustain high g force. The Orion probe could take up to 100 gees of force per detonation, since biologicals would not be present.
  7. Mar 2, 2017 #6


    User Avatar
    2017 Award

    Staff: Mentor

    That's what the pusher plate is doing! Adding a rotation just makes everything more complicated, increases g-forces, increases the overall spacecraft mass, and leads to various other issues.

    The crew has to stay in front of the pusher plate (where "forwards" is the direction of acceleration) to use it as radiation shield. There is not much space for large rotations.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted