Author Topic: Relatively inexpensive active thrust system for asteroid deflection  (Read 4657 times)

Offline JasonAW3

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Ok guys,

     I'm not 100% sure thatthis would go in this section, but as it would use an active electron thrust system I figured that this would be the closest match.  If not, I ask that the moderator move it to the appropriate group.
     Now, to the point;

     I have studied many of the proposal for actively and passively deflecting a variety of astroids from the solid metalic to the 'dust bunny' (my words, not NASA's) using a variety of systems from solar sails, gravity tractors, nukes, even painting one side black and one side white.

     All of these proposals had their benifits and drawbacks, but I would like to propose a system that would provide an active thrust vector while being able to be used on a wide variety of different asteroid types and with a certain amount of thrust reduction, (as well as an amount of unit losses due to outgassing) possibly on a comet as well.

     What I am suggesting are millions of small electron thruster units, with a 10 centimeter by 10 centimeter solar panel, whict would also act as the base in contact with the surface, with a tiny electron thruster, gimbaling system using MEMS type devices and a computer package with a broardband cellular modem and the equivelent of a smartphone's computer, camera and MEM gyroscopes for guidance and a lithium/polymer battery pack for power storage.  With the thruster avionics package in the center of the solar panel, (assuming a 10 square centimeter footprint) this would leave about 90 square centimeters of solar panel, (minus the shadow that would sweep across the panel as the asteroid / comet rotated) to gather solar power for the truster and computer systems.  As all of the millions of thruster units would produce about one tenth of a gram of thrust for however long they would be exposed to the sun, this would add up to a substantile amount of thrust, distributed over a large surface of a NEO object.

     Assuming that you needed to deflect a 1 kilometer asteroid, IK guesstimated that about only 1/3 of the total surface area would actually be usable for this use, due to debris, void spaces, shadows, etc, one could put nearly 105 MILLION of these units on the surface.  Assuming about 150 million were sent up, one could have a 25% failure rate of the total units and still have more than enough to do the job done.

     All of thse units would network together to produce the equvelent of a fairly powerful supercomputer, but with a bit slower data rate, due to distance between eact unit and signal drop out due to cosmic radiation, transient RF and solar storms.

     Each "mission bus" that would deliver a portion of the hundreds of millions of smaller thruster units to the NEO, woiuld also take up a station keeping orbit or parallel course and act as a relay to coordinate the millions of units as well as deliver long range telemetery back and forth with Earth.  Assuming each group of 10 million thruster units used one delivery bus, this would place 15 telemetry/coordination units in orbit / on parallel courses for maximum redundancy.

     As the total surface area of the 1 kilometer asteroid would be, approximately, 31.415 billion square centimeters, we deduct about 2/3rd's as noted, for approximately 10.472 billion square centimeters, dividing this by 100 square centimeters, (the total surface area taken up per unit) approximately 104.72 million units could be distributed on the NEO surface.  At about 1 tenth of a gram per unit for thrust, and assuming the NEO rotates around a single or multiple axis, this would provide a continious thrust of about 3.95 million grams or about 3.95 tons of continious thrust, varying according to unit distribution.  Over a period of a couple of months, this should produce a fairly sizable deviation of it's orbital path.

     One issue is the mass.  Using thin-film and memory metal technologies, as well as standard computer component technologies, production of 150 million units would be easily within current prodution capibilities, and as each unit weighs, perhaps 50 grams each, (likely an over-estimation by a factor of approximately 10) each dilevery bus itself massing about 5,000 Kilograms would have to carry and guide 500,000 Kilograms or about 505 metric tons per bus.  Assuming the units can be made at 5 grams mass each, this reduces to 55 metric tons, which is easily in a number of HLLV's payload capibility.  Fifteen HLLV launches from the US, Russia and Ariean Space, is do-able in a year and a year's worth of production from several major microelectronics firms, (especially if the entiire system is printed on a single sheet of thin film material) could be easily made in a year.
     Transit time would depend on basic celestial mechanics but should be able to be in place in about a year and a half to two and a half years.

     Assuming 1000 square centimeter units were used, (100 by 100 centimeters) thrust would stay about the same oveall while reducing the number needed by a factor of 10, and oveall mass by about 3/4's. (Minus the delivery bus mass of about 5 metric tons per launch).

     Again, these are simply back of napkin figures, adding alot of pesimistic estimates, but these figures should work as a starting point.

JasonAW3
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Offline Solman

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 I love the idea of having millions of units and having them networked and working together. The benefits of mass production and the versatility in being able to adapt to asteroids of widely varying composition and even comets as well.
 Similar units might be useful for mining NEO's or even braking large payloads to Earth orbit from asteroids, Luna, or Mars or vice versa.
 
Sol

Offline space_man

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What propellant do the ion thrusters utilize?

Offline JasonAW3

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What propellant do the ion thrusters utilize?

     Ion thrusters could use a variety of gases, including volitiles extractable from asteroids or comets, but as these are Electric thrusters, you could, in theory, use the dust and small debris on the asteroid's surface as reaction mass, charging the material and electrostatically ejecting it out into space.
     If need be, small 'mouse bots', either using electrically charged treds to stay on the surface, or electrostatric thrusters, could be used to gather dust and debris in small hopper bins and deliver them to each of the thruster units.  During the 'refuel' the thruster unit, the 'mousebot' could recharge from the thruster unit's EV cells.  I imagine the 'mousebots' might looks somewhat like the Roomba floor cleaning Jasonbots.  Form following function.

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Offline space_man

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I believe the energy it will take you to gather "comet dust" combined with the low specific impulse of ejecting "dust particles" will offset the viability of this concept.

Offline MajorBringdown

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Could you achieve a similar result by having a LCD panel (or something similar) that could be turned off and on to change the albedo over the surface of the asteroid?  It's like the idea of painting the asteroid, but with more control.

It removes the potential problems of gathering reaction mass with robots.

Offline JasonAW3

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I believe the energy it will take you to gather "comet dust" combined with the low specific impulse of ejecting "dust particles" will offset the viability of this concept.

I'm not totally certain I agree with you here, but as you might have a point, much of the material could, in theory, be gathered from directly under each unit.  In the case of comets, one would likely have to anchor each unit somehow to prevent their dislodging via outgassing, and perhaps, using electromagnetically charged superconducting filiments  played from each unit, stretching away from the surface, out gassing material can be directed via sequentially activated and deactivated and power varied filiments.  (As a comet is already outgassing, I simply propose directing the electrically charged gasses in a direction that facilitates an orbital change vis selectively applied EM fields).

     Asteroids present a different issue.

     If the direct dust thrust system wouldnt work, perhaps a series of filiments can be deployed from each unit, avoiding crossing over other units and other filiments to centeralized locations strategically located across the surface of the asteroid, allowing the units to charge those areas with a high energy negative electrical charge.  When a high enough level is reached, one unit, not attached to the other filiments, will use it's power charge to create an electron beam to both propel itself up and over the surface of the asteroid, as well as building up a substantial positive charge in itself.  once it is in the proper position and has achieved the desired level of a positive charge, it will sacrificially begin approaching the negatively charged area, (Which the other units have severed their filiments to at this point) and allow the high powered arc of electricity to both vaporize the positively charged unit and a portion of the surrounding dust and rock on the surface of the asteroid.

     As an electrical arc of this nature, (more or less a lightening bolt) produces a fairly explosive amount of power, I figure a few thousand of these, 'zaps' should allow a substantial defelection of such a massive body. 

     Of course, each unit, being equiped with an electron pump drive, could simply sit tight, converting sunlight into electrons, and pumping them out as an individual electron beams on a semi-continious basis, adding a fairly high amount of delta-V to the rock.  Again, magnetic filiments could be used to redirect the general direction of thrust, allowing a degree of steering to the design.

Jason 
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Offline JasonAW3

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Could you achieve a similar result by having a LCD panel (or something similar) that could be turned off and on to change the albedo over the surface of the asteroid?  It's like the idea of painting the asteroid, but with more control.

It removes the potential problems of gathering reaction mass with robots.

Interesting idea.

     So long as the LCDs are using transparent solar cells on them to charge up the batteries, I don't see why that wouldn't work, off the top of my head.

     Of courseit occures to me to wonder if simply increasing or decreasing the spin of an asteroid or comet could aalter their course via gyroscopic precession?  if so either process, either your LCDs or the Electron Beam units I meantioned before, could work, using less units, but a substantially longer time before impact.

     Anyway you look at it, I suspect that many smaller, lower powered units distributed over an asteroid or comet's surface, would have a greater and and more controlable effect than one or a few larger, high powered units.

Jason
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Offline JasonAW3

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     It also occures to me that these units could also each mount a small directional microwave emiter to selectively heat the surface of an asteroid or comet to promote directionalized outgassing, which would act as a form of thrust.

Jason
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Offline MajorBringdown

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Could you achieve a similar result by having a LCD panel (or something similar) that could be turned off and on to change the albedo over the surface of the asteroid?  It's like the idea of painting the asteroid, but with more control.

It removes the potential problems of gathering reaction mass with robots.

Interesting idea.

     So long as the LCDs are using transparent solar cells on them to charge up the batteries, I don't see why that wouldn't work, off the top of my head.

     Of courseit occures to me to wonder if simply increasing or decreasing the spin of an asteroid or comet could aalter their course via gyroscopic precession?  if so either process, either your LCDs or the Electron Beam units I meantioned before, could work, using less units, but a substantially longer time before impact.

     Anyway you look at it, I suspect that many smaller, lower powered units distributed over an asteroid or comet's surface, would have a greater and and more controlable effect than one or a few larger, high powered units.

Jason



I suspect you probably wouldn't need transparent solar cells.  If the device was a square panel, and one half was solar cells and the other half some sort of panel that can change from dark to reflective, you would probably still be able to get a reasonable change in albedo if you had good enough coverage on the asteroid.

Now, I'm just pulling this out of my backside.  I haven't done any napkin math to confirm my idea.

Offline JasonAW3

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Could you achieve a similar result by having a LCD panel (or something similar) that could be turned off and on to change the albedo over the surface of the asteroid?  It's like the idea of painting the asteroid, but with more control.

It removes the potential problems of gathering reaction mass with robots.

Interesting idea.

     So long as the LCDs are using transparent solar cells on them to charge up the batteries, I don't see why that wouldn't work, off the top of my head.

     Of courseit occures to me to wonder if simply increasing or decreasing the spin of an asteroid or comet could aalter their course via gyroscopic precession?  if so either process, either your LCDs or the Electron Beam units I meantioned before, could work, using less units, but a substantially longer time before impact.

     Anyway you look at it, I suspect that many smaller, lower powered units distributed over an asteroid or comet's surface, would have a greater and and more controlable effect than one or a few larger, high powered units.

Jason



I suspect you probably wouldn't need transparent solar cells.  If the device was a square panel, and one half was solar cells and the other half some sort of panel that can change from dark to reflective, you would probably still be able to get a reasonable change in albedo if you had good enough coverage on the asteroid.

Now, I'm just pulling this out of my backside.  I haven't done any napkin math to confirm my idea.

You're likely right, but I was considering maximum reflectivity versus a 50% loss of albedo.  But I also didn't take into account the natural reflectivity that the solar panels will have on their own.

     While your idea is an active system, I prefer one that would add a bit more thrust to the whole set up.

     Of corse, one could set up the asteroid with a huge positivetive electrical charge and use some of the units, flying free of the asteroid, with a massive negative electrical charge, as sacrificial targets.  When the electricity discharges from the asteroid to the unit, not only will the unit vaporize, but so would some of the asteroid's surface.  this would also act as thrust.  Not alot, admittedly, but maybe enough to divert an asteroid as needed.

Jason
My God!  It's full of universes!

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