wisdom & handicraft
Captive Mass Space Engine
by Robert Buckalew
Rockets work on basic Newtonian principles. Throwing mass out the back of a rocket creates thrust. Carrying the mass necessary to create thrust is a detriment to space travel and limits long range missions. The loss of mass during a launch is essential to getting rockets from Earth to space. However once in space much less thrust is required to move mass, and an engine that produces even a very small net thrust could gradually influence the motion of objects in space to relocate space junk, transport supplies, change or maintain orbits or even deliver craft to distant destinations with its gradual but cumulative Δv. The conservation and reuse of accelerated mass in such systems would be an important advance to space travel and off-world space industries. This paper will show how an engine can create net thrust in space while preserving and reusing the propulsive mass needed to accelerate the engine.
If a space ship’s propulsive mass was not thrown away and could be reused such an engine would be limited only by the energy required to accelerate this reusable mass. In this description only solid masses (imagine golf balls) will be used although other types of mass might be employed. Throwing (accelerating) a mass inside the confined space of the engine creates the same reaction velocity (kg sec2) as an equivalent mass and velocity of rocket exhaust thrust, but only initially. When that moving mass reaches an opposing wall of the enclosure its impact nulls whatever initial thrust was created, stopping the velocity of the space ship. Only if that kinetic energy in the moving mass is otherwise reduced or canceled will a net thrust have been created maintaining the vehicle’s velocity as if the mass were conventionally sent into space.
A system using two equal masses accelerated equally allows mutual cancellation of the inertia in the two propulsive masses. Two mass drivers (guns) accelerate the two masses simultaneously, in parallel to strike two reflective surfaces placed 45° to their velocity vector. The masses then are oppositely redirected 90° from their initial velocity vector to non-destructive inertial arresters that absorb the energy. With the negation of this inertia the forward motion of the engine is maintained while the preservation of the propulsive mass makes it possible to reuse this mass repeatedly for additional acceleration.
There are two basic configurations of this captive mass engine, the diverging mass and the converging mass designs. Both employ the same method of preserving the masses by parallel acceleration of equal masses, a mirrored redirecting of internal mass motion and symmetrical canceling of mass momentum
In this diverging mass example the accelerator guns are located at End B. At the opposite, A end of the engine hull, are two centrally located reflectors forming a 90° angle and the absorbers mounted on opposite sides. When the accelerator guns simultaneously fire the two masses, an equal and opposite reaction force is created moving the engine in the opposite direction of the traveling masses. In this example the accelerated masses strike the angled reflectors which divert the motions of the masses 90° from their original parallel direction of travel. These equal and opposite changes in motion send the masses to the capturing absorbers which simultaneously and symmetrically capture and arrest the masses’ velocities while not creating forces which would affect the forward direction of the engine.
In its converging mass configuration the accelerator guns are again at End B, the reflectors remain at End A, though now inverted, with a single arrester centrally located along the axis of the engine. Again a simultaneous firing of the masses causes a reaction force that moves the engine in the desired direction. The parallel traveling masses simultaneously hit the angled reflectors at a 45° angle. These reflectors divert most of the velocities of the masses 90° from their original direction of motion to the capturing arrester at the central axis of the engine. Because the kinetic energies of the masses at the reflectors and arrester are equal, opposite and simultaneous, they are mutually canceled. Side forces affecting the forward direction of the engine are avoided. Having lost all velocity and momentum, the masses come to rest leaving only the initial accelerating force that propelled the balls to react on the engine as if the masses were shot into space.
After a series of such firings the propellant mass would be at the A end of the engine. At this point the engine is moving along its long axis and would continue to travel indefinitely in space with the movable mass now at the trailing end of the engine. Just leaving the ball mass at the trailing, A end, would allow the engine to continue at its velocity indefinitely. Although this is good, in most cases it would be better to further increase this velocity and shorten the travel time.
With the propellant mass preserved inside the engine hull, firing a second volley of mass from the leading end of the engine could double this initial velocity of the engine. To reuse the mass for additional acceleration, the mass must somehow get from the trailing end to the leading end of the direction of travel where it can be fired again. However, returning the fired mass to the leading, B end, of the engine would produce a canceling force opposite the traveling vector of the now accelerated engine. Putting additional accelerator guns at the A end of the engine and firing the mass back would quickly stop the motion of the engine. No matter what method or how slowly the ball masses were returned (imagine using a slowly moving conveyor belt) the linear return of the mass would cancel the forward motion, although the distance the engine traveled would be preserved.
Adding a pair of guns at the A end of the engine, and then reorienting the engine in space so the A end with the mass would become the leading end, the balls could be fired again in a way that would add velocity to the engine. This could be accomplished by rotating the engine 180°. Adding this component of rotation around the center of the engine mass requires little energy although the rate of rotation would be proportional to that energy. The mechanism necessary to accomplish this rotation already exists. Having retained a small reserve of mass at the B end, equal masses are fired from opposite side guns. The resultant arresting force on the absorbers that stops the masses would create a torque (moment) about the center of mass axis. Once started, this rotation in space would continue indefinitely if not stopped by another firing of counter-rotational forces.
With most of the propellant mass accumulated at the A end of the engine an outside observer would see an apparent eccentric rotation since the lighter, B end, would extend more from the center of the rotation to offset the higher accumulated mass at the A end. Once the engine had completed a 180° turn, firing the other two guns with an equal amount of mass would stop the rotation leaving the engine still traveling with its initial velocity vector largely unaffected but facing in the opposite direction. The A end propulsive mass, now at the leading end of travel, can be fired again to increase the velocity.
With the balanced spin arrested and the propulsive mass now at the forward end of travel, the propulsive mass is in position for a second volley, after which the engine will be moving at twice its initial velocity. As long as energy is available this process can be repeated adding velocity each time until the forward velocity is sufficient for the trip.
To minimize the energy required to achieve rotation, the engine should be designed to minimize mass at the extremities (A and B ends). However the extremities of the engine are where the greatest strength is needed for inertial absorption and where the firing and reloading mechanisms need to be located. The limits of inertial absorption (and therefore mass firing velocity) would be the strengths, durabilities and heat dissipation characteristics of the reflector plate and inertial absorber.
To maximize the efficiency of the rotational torque, the rotational forces should be applied perpendicular to the direction of travel and as far from the center of mass as possible. The rate of rotation will be proportional to the momentum of these offsetting forces. Firing additional mass will increase the rate of rotation. Because the guns are not on the engine centerline the gun reactions will add an opposite moment of inertia to the intended rotational vector caused by the mass arrest. However this effect can be minimized by locating the absorbers farther from the center of mass and moving the guns closer to the centerline of the engine (greater length to width ratio).
Calculating the Ship’s Velocity
Note: When the engine, power unit and cargo space are assembled this will be referred to as the “ship” and will include the additional mass of these structures.
The Δv of the ship with each volley can be calculated as follows:
If the projectiles were fired with a velocity of 300 m/s and the ship is 1000 times more massive than the total mass of the projectiles fired and projectile bounce efficiency is 0.8, the ship velocity would increase by .24 m/s.
This paper assumes the propulsive mass will be a solid material. The selection of a suitable projectile material involves weighing the various performance requirements: shape, mass, coefficient of restitution (bounce efficiency) and durability.
A spherical projectile (ball) is best for consistent, predictable bounce direction from the deflector and ease of handling and automated reloading. Because the engine is operating only in the vacuum of space considerations for air resistance or aerodynamics need not be considered. A high density projectile (mass per unit volume) increases the reaction force that creates the forward thrust. High density materials include metals such as iron and depleted uranium and metal alloys such as steel and brass.
A primary consideration in the efficiency of the engine is the ball’s efficiency of bounce (coefficient of restitution). A basic measure of this efficiency is the reflected velocity of the sphere after the bounce off of the reflector plate. The more velocity that is retained after the bounce, the less energy has gone into the engine’s reflector, which directly reduces the ship’s velocity. The coefficient of restitution, denoted by (e), is the ratio of the final to initial relative velocity between two objects after they collide.
Durability of the propulsive mass determines, to a large extent, the durability and dependability of the system. The ability to withstand the heat and shock of repeated, rapid acceleration, the high speed glancing deflection from the reflector and the sudden impact with the absorber while retaining shape, surface finish and coefficient of restitution, will all be factors in the useful lifetime of the propulsive mass. The use of surface hardened steel spheres as the propulsive mass meets many of these considerations: high mass, high (e), and durability while also having ferro-magnetic properties which would be necessary for electromagnetic guns and might prove useful in the collection, storage and reloading of the mass. However a multi-layered sphere of various materials, much like a gulf ball, might provide superior performance over a uniform solid material.
The efficiency of the system depends in part on the momentum (velocity x mass kg.m/s) of the projectile. Increasing either the propulsive mass or mass velocity will proportionally increase the momentum. A higher mass velocity will produce a greater thrust given the available mass. The maximum propellant velocity will be limited by numerous factors including the structural limits of the gun, the durability of the mass and the reflector and the dampening and heat dissipation capacity of the absorbers.
Although this example has been limited to solid masses, the propulsive mass could take other forms: fluids, electromagnetic radiation (laser light), particle beams (plasma) and possibly sound waves. The measure of the reflective efficiency (e) following the 90° turn is a determining factor of propulsive mass efficiency. Gases or liquids though easily contained and pumped must demonstrate a high (e) when following tubes through the required 90° turn. Although electromagnetic radiation is easily created, absorbed and reflected, photons exhibit very low inertial mass.
Mass Accelerator Gun
Solid propellant mass can be accelerated by chemical energy (like explosive gas mixtures or gunpowder), electromagnetic (mass driver, linear motor, coil gun) or kinetic energy (like a hammer or stored energy in a flywheel). Such systems could be powered by electricity, compressed gas or chemical combustion. Employing electromagnetic cannons eliminates the need for flammable, corrosive or toxic fuels that can be unstable or deleterious to humans. High firing rates in the non-convective vacuum of space may necessitate the active cooling of guns with pumps and radiators.
An efficient reflector would have a hardened surface, be rigid (inflexible) and solidly mounted to the engine to encourage bounce with a minimum of energy absorption. Any energy absorbed by the reflector would create counter-productive thrust, reducing he desired forward velocity of the ship.
As this coefficient approaches 1, more of the mass velocity is recovered, less retarding energy transferred into the reflector and more momentum productively captured by the absorber. The reflector would be designed to be detachable from the hull for replacement if it becomes worn or damaged.
The first function of the absorber/arrester is the absorption of the kinetic energy in the propulsive mass and the dispersion of the resultant heat. It requires properties diametrically opposite those of the reflector and might be thought of as the antithesis of a reflector. Like the reflector it would be subject to fatigue and failure and as such it needs to be a separate part designed for simple replacement.
To arrest the propellant momentum the absorber must yield to kinetic energy and rapidly recover. Designs might include an elastomer coated steel with liquid or gel backing to move with the impact and distribute that energy over a larger, heat-absorbing and conductive surface.
Once the kinetic energy of the moving mass is dispersed, the second “arrester” function of the absorber/arrester is to manipulate the mass in such a way that the balls can be stored and reloaded into the guns to repeat the acceleration process. For efficiency the re-organization of propellant mass should be accomplished during the interval when the engine is in rotation. The rate of rotation would then determine the time constraint on this process. Although this process adds some mechanical complexity to the system it might be designed for both minimal mass and energy use. Using electro-magnets with steel balls might enhance the collection and reloading of the propulsive mass. The firing rate would depend upon the efficiency of the mass reloading mechanism, the recovery time for the firing mechanism and the propulsive energy recharge rate.
An external power source is required for accelerating the propellant mass, reloading the guns, cooling the guns and absorbers, and moving and rotating the engine. Electrical energy, being very versatile, could be used for all necessary functions of the engine. Any form of prime power could be employed for electrical energy generation; solar electric, nuclear, heat engine or fuel cell. Electrical energy is usually not the limiting factor in space travel but becomes a design variable. Since the accelerated mass is reusable, solar arrays or nuclear power would be best for extended term and long range use of this system.
Unlike some other means of space propulsion, such as solar or mag sails, the captive mass engine can be decelerated by simply reversing the firing direction, firing the propellant mass in the direction of travel (from the trailing end toward the leading end). Once the destination is near, the mass could be repeatedly fired to decelerate the ship for orbit or docking.
Divergent vs Convergent Designs
With a divergent mass system the ability of the hull structure to absorb the propellant’s mass momentum without damage would limit the momentum (mass x velocity) of the propellant mass. In the convergent design the hull would only be required to absorb 20% of the mass inertia at the reflector, assuming a coefficient of restitution of .8. Here the centrally located absorber dampens most of the energy with the converging forces of the masses being balanced. This should allow a lighter construction at the engine’s rotational extremes.
Incorporating the Engine into a Ship
In the previous drawings the engine is not a part of a larger ship with power units, solar arrays or cargo capacity. To create such a fully functional space craft will add mass. To minimize rotational inertia, cargo and power units should not be directly attached to the engine where they also would be part of the rotational mass. Pivotal connections are required between the connecting yoke and the engine to allow the engine to separately rotate without the ship’s mass. However, with the firing of each volley the center of mass changes and therefore the balanced rotation point of the engine moves. For energy efficient rotation the engine must be rotated at this changing center of mass. These rotation axes will predictably shift equal distances from the engine centerline for any given quantity of propellant mass that is moved. The pivot pins must be mounted on the engine corresponding to the two rotation axes of the changing centers of mass.
Rotating Engine Attached to Ship
There are four basic steps to implement center of mass axis engine rotation while keeping the engine attached. Four pivot pins, two at each of the two pivot centerlines, are affixed to the hull of the engine. These four pins will all be latched to the yoke (as shown above) during mass firing to create a secure connection between the engine and ship. Once the propellant mass has been fired the engine is readied to be rotated separately from the rest of the ship.
The first step is to disengage the latches at the leading pivot pins leaving only the two trailing pivot bearings latched. This will allow rotation to occur at the trailing pivot pins (mass centerline) when the reserve rotation mass is asymmetrically fired.
1. Pivot bearings engaged at mass centerline for rotation
Once engine rotation has been stopped at 180° the engine is at its furthermost point in the yoke and must be moved back in to realign the four pivot pins with their respective latches.
2. Rotation complete – firing mass returns engine to pivot point
To guide this motion the four double flanged wheels are engaged with the two guide rails attached to the engine. The pivot bearings can now be retracted (disengaged) from their pivot pins and the forward engine stops must be extended. When an initial propellant mass is fired the engine will move toward the ship guided by the wheels and rails until the leading pivot pins contact the engine stops.
3. Engine reaction motion stopped at new pivot engagement point
Any momentum from the moving engine will be transferred to the ship’s yoke in the direction of travel. At this point the two pivot bearings and the two forward latches can be extended to engage the four pivot pins and secure the engine. With the four pins secured, the flanged wheels can be retracted. The engine is now ready for another volley firing of mass to increase the ships velocity.
4. Engine secured for firing remainder of mass propellant
Three Dimensional Control & Scale
The drawings so far have shown only a flat representation of the captive mass system. Such engines would have control in only two dimensions. To control attitude and direction in three dimensional space requires pitch, roll and yaw control. Flat engines can be assembled into various geometric configurations. Four of these flat engines could be assembled into a four sided box with pyramidal end reflectors or another configuration could be a cylindrical design with conical end reflectors and mass accelerator guns lining the inside of the hull
These arrangements would provide pitch and yaw control by the eccentric firing of mass from paired guns. Roll control can be implemented with symmetrically pared, small, flat engines centered on the hull and mounted transversely to the engine’s forward motion.
The captive mass rocket engine may demonstrate an efficiency of scale. Small, CubeSat size systems might prove more effective than large, heavy payload missions. Larger quantities of small propulsive mass may be more effective than using fewer large mass spheres. Supplemental chemical rocket acceleration and deceleration can be added for time sensitive applications such as human travel.
The captured mass engine operates with mature, mechanical technologies, making it a reliable and easily serviced propulsive space engine. Long range and long term scientific missions are often terminated because of the depletion of needed propellant. A captive propellant system in conjunction with a nuclear or solar energy power source can resolve this constraint on extended, robotic, interplanetary missions. With the projected growth in space manufacturing, asteroid mining, lunar bases and space stations a captive mass system should be well suited for LEO, MEO, GSO and cislunar space transport.
Engineered Exogenesis: Nature’s Model for interstellar colonization
by Robert Buckalew
The series of pivotal events that led to the development of intelligent life on Earth are so numerous and seemingly random that the occurrence of intelligent life at other places in the galaxy may be very rare. The chance extinction of the dinosaurs which led to the diversification and opportunistic evolution of mammals is but one of many such events. Assuming the extraordinary rarity of this occurrence elsewhere in the galaxy should be a compelling reason for humans to presume our gifts of intellect exceptional and assume the obligation to prevent this cosmic largess from vanishing through global natural disaster, nuclear war or self-made neglect. Even if intelligent life is found to be common in the universe, it is certain that our form of intelligent life is unique. If we wish, someday, to communicate and interact with these various sentient species and contribute our singular human culture to their diverse communities, we must project our species’ existence into cosmic time frames.
The creation of dispersed, self-sufficient human settlements both interplanetary and extra-solar is the best way to ensure our long term survival as a species. Because of the unimaginable distances to other star systems, most proposals for interstellar colonization involve large multi-generational starships, warp drives or wormholes. Although common plot devices to create science fiction stories, wormholes and warp drives appear unworkable travel methods given the constraints of known physics. Multi-generational starships come with their own technological, political, biological, social and psychological challenges that make their realization daunting to consider.
Nature, however, has developed efficient methods to spread life on Earth that could be employed for interstellar colonization. Engineered Exogenesis, modeled after successful natural processes, proposes a method to spread Earth-life throughout our local stellar neighborhood.
Exogenesis, in astrobiology, is the hypothesis that life originated elsewhere in the universe and was conveyed here to Earth. For example, there is evidence that life in our solar system originated on Mars and was brought to this planet aboard a meteorite. The plausibility of Earth-life having been transplanted is supported by our inability to create spontaneous life from primordial organic chemicals in the laboratory and by the fact that there is no known remnant of pre-genetic life on Earth.
Engineered Exogenesis will use an additional strategy derived from nature. The survival system used by plants, insects and many aquatic lifeforms is based on the overproduction of seeds, larvae or spores in order to overcome their natural failure rate. Mass produced microbots can be designed to intentionally deliver engineered genetics to prospective exoplanets in numbers sufficient to assure that some will likely reach their destination and survive. As with seeds, this may require the dissemination of thousands to millions of them, based on the projected failure rate of the delivery system and the expected germination rate.
We know that water and organic compounds, known as tholins, have been found on planets, moons, comets and asteroids throughout our solar system. These precursors for life are believed to exist on interstellar comets and asteroids as well. Planetary exo-systems are expected to offer a similar fertile environment ready for the introduction of earthly genetic material.
The major components of an Engineered Exogenesis system might include 1) a microbiotic vessel that travels to the extra-solar planet, 2) a space-based magnetic accelerator capable of providing the inertial energy to send the vessel to other solar systems, 3) a space-based laser providing communication and supplemental energy for solar sail navigation and maneuvering, and 4) the engineered genetic material capable of growing a bio-robotic agent on the exoplanet to prepare the planetary environment for humans.
The microbiotic vessel, hereafter referred to as the microbot, would transport hermetically encapsulated, genetic material to the destination exoplanet while providing radiation, magnetic and acceleration protection. This vessel would be designed to open in the presence of liquid water, deploy a biobot zygote and, if necessary, a photosynthesizing food source such as phytoplankton or other aqueous plant food. The engineering of the microbot would incorporate nano technology, bio-robotics, AI and neural networks. It could be very small, possibly the size of a grain of rice, and constructed of low mass materials to minimize the energy required for acceleration. Construction materials might include carbon fiber, graphene or Kevlar designed towithstand the high magnetic fields and high acceleration rates and to provide heat shielding for atmospheric entry. Microbot vessels would possess no on-board propulsion using only their initial inertial energy for space travel. A ferromagnetic mass at the leading end of the vessel would be required for magnetic acceleration and inertial stability. This mass might be separated for deceleration upon arrival at the planetary system or retained for atmospheric entry shielding.
Microbos would also use leading and trailing photo-sensors for navigational aids with the leading photo-sensor directed at the destination star and the trailing sensor pointed at Sol. Fore and aft modulated, bio-luminescent lasers would provide communication between traveling microbot ships reminiscent of fireflies on a summer night.
A series of pivoting, flat panels would be extended following launch. Each panel would use one side for solar energy collection. Solar electric storage might be achieved by capacitance of the microbot body. The obverse side, capable of adjustable reflectivity, would be used as a solar sail. The panel ends would also be capable of latching with other microbot panels for the creation of microbot arrays, connected clusters of individual microbots. A powdered iron substrate layer which would become magnetized during acceleration could aid in microbot arraying and later become a magsail for magnetic braking. A superconducting loop for magnetic braking could be incorporated into the perimeter of the solar panels or otherwise deployed as an independent loop. Finally, the panels could be positioned for autogyro aerobraking during atmospheric entry in the same way maple seeds can dissipate energy by helicoptering to Earth.
Magnetic acceleration happens by activating each electromagnet ahead of the projectile to pull it forward. As the projectile accelerates, the rate of coil activation increases to stay ahead of the accelerating mass. Projectile acceleration would be limited by the inertial mass of the projectile and the force produced by the electromagnets. Magnetic accelerators can include a circular or linear motor configuration.
Aimed at the destination star, the microbots would be accelerated sequentially for a maximum exit velocity with a minimum energy expenditure. This must be a space based as the atmospheric heating from the very high exit velocity precludes microbots being launched from Earth. By timing the sequencing of the magnets the rate of acceleration can be optimized for the given projectile mass and the vulnerability of the vehicle and payload to the forces of acceleration. The length of a linear accelerator is inversely related to the acceleration needed for a given exit velocity – the longer the coil gun, the less acceleration needed. A circular, toroidal accelerator would not have this length constraint as it could use multiple cycles to obtain projectile terminal velocity. Once the system is deployed it could be used for numerous target stars. If microbots can be accelerated to 10% light speed, a trip to Alpha Centari (4.37 light years away) would take 43 years and a trip to Tau Ceti (10.4 light years away) would take 104 years. Reaching these speeds would be a function of the length and power of the accelerator and the mass of the microbot ship.
The laser is not for propulsion, as suggested by Yuri Milner’s Breakthrough Starshot, but would be used for communication and programming updates by modulation of the laser beam. It could also provide energy for course correction and arraying maneuvers. It is also best located in space to reduce atmospheric light scattering.
Microbots would be programmed to array although some microbots would necessarily remain as self sufficient individual ships. The primary purpose of arraying is to improve communication with Earth as a larger antenna area can enhance both transmission and reception performance. However, arraying may also be used to collectivize the solar power and energy storage and to organize the use of this power.
Microbot arraying could be achieved through use of swarm intelligence, a naturally occurring function among social insects, migrating birds and fish schools. Known in robotics as distributed AI, microbots could communicate with each other while traveling in space through their fore and aft photo-sensors and modulated bio-luminescence. As the trip may take 100 years or more, there should be adequate time for arraying even considering the limited maneuvering power provided by the angular incident positioning and variable reflectivity of their panels. Although launched individually, the first vessels would be accelerated at a slower velocity than the later vessels causing their clumping in space as they travel and increasing their ability to form arrays.
Microbots Arrival and Descent to the ExoPlanet
Deceleration from near relativistic speeds to that of planetary orbit velocity is always problematic. Explosive ejection of the leading ferromagnetic mass could substantially decelerate the containment vessel while reducing the remaining microbot maneuvering mass. Employing the resistance of the reflective solar sails and the magsail, braking and maneuvering could be achieved by using the retrograde radiant photon pressure, plasma energy streams and charged magnetosphere of the destination star. Solar and magnetic braking could continue after entering an elliptical orbit of the star, until a matching planetary orbital velocity is obtained. With aerobraking the arrays could go from an elliptical orbit of the planet to a circular one. For the solitary microbots aerobraking would slow them for atmospheric entry.
Microbots entering the atmosphere would experience further braking through atmospheric drag. With reduced velocity, low gravitational attraction and high surface-to-mass ratios, atmospheric entry damage to the microbots might be kept to a minimum. Descent might be further dampened and controlled by positioning the panels for autogyro energy dissipation.
Engineered Genetic Materials
Genetics has become a game-changing technology allowing for man-made biological creativity. Genetic engineering has been revolutionized through CRISPR and the creation of artificial life by scientists like Craig Venter. Expanding the genetic alphabet beyond the 4 chemical bases found in DNA could add functions capable of assembling metal or silicon components into planet inhabiting biobots.
Although the microbot starship incorporated some bio-robotic functions such as neural networks and bio-luminescence for communication, it did not need the biobot ability to grow and reproduce. The biobots used for planetary exploration, terraforming and habitat construction would be grown from the genetic material in the microbot after acquiring a suitable watery environment for germination/gestation. These bio-life forms would be genetically designed to be suitable for the anticipated planetary environment but might also incorporate a greater degree of robotics into their biology for laser communication with Earth and reprogrammability.
Essential BioBot Characteristics
The first terrestrial biobots might best be designed to be amphibious for food access and terrain mobility and cold blooded for temperature tolerance. They might be capable of solar power or photosynthesis for their energy, but separate genetic material may be included to produce a photosynthesizing food source for the biobots.
Their instinctive behavior would include a work activity for communication and infrastructure building similar to instinctive nest, hive or web building found with Earth life. Their behaviors would be re-programmable from Earth allowing task changing capability. For this they would require a means to transmit and receive laser modulated signals with Earth as well as their interspecies communication using sound or light modulation.
Reproduction could be biological though it would likely be asexual. Reproduction would also be programmable through Earth communication in order to create a series of diverse offspring, specifically-tasked and specialized biobots. Eventually there would be terraforming for human habitation. After successful habitat construction and terraforming, the final genetic download would be human genomes for incubation. This would require specialized biobots for human gestation and nurturing. These humans could be genetically designed for the gravity, atmosphere and temperatures of the exoplanet by adjusting metabolism rate, body mass, lung capacity, skin color, fat, fur covering, etc. These modifications would prognosticate natural changes which would have evolved over time in humans in adapting to their new environment.
The simpler alternative to the more complex remote reproductive reprogramming would be to send sequential waves of microbots each containing subsequent genetics. However, the advantages of remote genetic reprogramming would not only result in faster colonization, but the genetic developments during the 100+ year microbot travel time could be incorporated in the transmitted genetic code.
Advantages of Engineered Exogenesis
There are some obvious advantages that come with with an Engineered Exogenesis approach to interstellar colonization. It would be scalable, specifically, the numbers of microbots manufactured and launch frequencies can be adjusted to suit political or financial circumstances. It would not be limited to one target planet, and any number of planets or newly discovered planets or moons could be added as targets over time. It would be tested in our solar system and modified with improvements before deployment. The seeding and growth of biobots could take place on Earth or in domed environments on the moon or Mars. Finally, it reduces the time scale for starship colonization, and eliminates human exposure to space travel. It, however, it lacks the drama and romance found in human adventure stories in space.
For Engineered Exogenesis to become a reality there are many technical problems to be resolved as well as numerous ethical issues to be considered such as the chauvinistic imposition of our genetics onto other evolving planetary systems, the creation and dissemination of synthetic, reproducing life forms and the alternation of our own human genome. Society, so far, has been accepting of test tube babies, GMO food crops and gene therapy, especially when it seems to improve our lives. Such controversial technological impositions may also be accepted as necessary in order to achieve a human interstellar presence.
Has This Happened Before?
If Engineered Exogenesis is a viable idea, would it not have been done by advanced alien civilizations? If so, why are there no alien biobots roving around on Earth? This is like the Fermi Paradox about space aliens. If they were sent here, maybe ocean Earth life feeds on these undeveloped alien genomes before they grow and reproduce. Possibly life on Earth is the result of an alien exogenesis. Then where are the microbot ships that carried them? They would be tiny, widely scattered and hard to find. Possibly the nascent search for micrometeorites on Earth may yet find one of these artificial nanobots.
1. Michael Noah Mautner Seeding the Universe with Life: Securing Our Cosmological Future. The Interstellar Panspermia Society. http://www.panspermia-society.com/
2. N. Mathews, A. L. Christensen, R. O’Grady, F. Mondada, and M. Dorigo Mergeable nervous systems for robots. Nature Communications. 8(439), 2017
3. Jennifer Doudna How CRISPR lets us edit our DNA. TED Talk. September 2015
4. J. Craig Venter Watch me unveil ‘synthetic life’ TED talk. May 2010
5. Daniela Rus Autonomous boats can target and latch onto each other MIT News June 5, 2019
6. Sarah Hörst What in the world(s) are tholins? July 22, 2015 Planetary Society http://www.planetary.org/blogs/guest-blogs/2015/0722-what-in-the-worlds-are-tholins.html
7. Francesco Corea Distributed Artificial Intelligence: A Primer on Multi-Agent Systems Agent Based Modeling and Swarm Intelligence Kdnuggets
8. Paul Gilster Starship Surfing: Ride the Bow Shock Centauri Dreams March 21, 2012 https://www.centauri-dreams.org/2012/03/21/starship-surfing-ride-the-bow-shock/
God of Science and Astronomy
Space Junk – An Overlooked Resource and Business Opportunity
Orbital debris is a growing problem and poses a serious hazard to astronauts, satellites and future space missions. It is estimated that more than 100 million pieces of space junk (6800 tons) are currently in Low Earth Orbit (LEO) traveling at speeds up to 17,500 MPH. and The Department of Defense Space Surveillance Network tracks 15,000 cataloged objects and there are hundreds of collisions every year. With decreasing launch prices and expanding multinational government and private launch capacity, the amount of space debris can be expected to multiply. As current and planned satellites become obsolete, deplete propellant or simply fail, there will be a steady supply of material joining the orbiting canopy of space debris.
Today, it costs $10,000 to put a pound of payload into Earth orbit. It was only by the uncommon exertions of costly rockets, fuel and a complex physical and institutional infrastructure that this orbiting material was released from the pull of Earth’s gravity to become a weightless menace. Proposed space junk disposal systems, such as the NASA ‘Laser Broom’, the Japanese Kounotori ‘Integrated Tether Experiments’ (KITE) and the Surrey Space Center’s ‘Remove DEBRIS’ are all based on deorbiting the junk and having it burn up in the atmosphere. Deorbiting and vaporizing this material disregards the effort and expense previously expended to put the materials into orbit.
Reprocessing scrap metal has always been less energy intensive than refining from natural, raw materials. Consisting mostly of metals, glass, ceramics and plastics, space junk possesses innate value primarily because of its propitious location. Recognizing the inherit value of this orbiting debris as the raw material of a future space manufacturing industry might alone be enough to transform our perception of it from dangerous trash to a useful resource. Implementing such a transformational cognizance might only require an injection of NASA or European Space Agency R&D funding and expertise for proving the feasibility of a Medium Earth Orbit (MEO) or Earth-Moon L4-L5 scrap storage facility. Such a study into space scrap storage technology could initiate a profitable, self-supporting commercial space cleanup, recycling and manufacturing industry. Space Drone tugs, built by London-based Effective Space, may be capable of moving dead satellites to this safe storage point.
Developing the initial design and engineering concepts could spur private and public funding for the construction, launch and implementation of a MEO storage facility. Additional funding for development and maintenance of a central storage facility could be generated with an imposed fee on those who profit from commercializing space or otherwise contribute to LEO space litter. And it is precisely these players who have the most to gain from a cleanup and the most to to lose from ignoring the problem. These include governments, militaries, launch services and satellite companies. Such a fee might also encourage vehicle and satellite designs that would minimize space clutter, incorporate a propellant system to move expended craft to the MEO scrap collection point and make separation, sorting and component recycling easier.
Once a MEO scrap storage facility was operational and the feasibility for scrap recycling realized, the commercial opportunities presented should spur the development of competitive proprietary methods to capture, agglomerate, contain and transport space debris. The next phase would consist of moving space debris to this single collection point in MEO. Transfer of some orbiting materials to the MEO location might be accomplished with NASA Laser Broom technology used to divert or increase orbital velocity.
Once MEO agglomeration of scrap material was initiated, the removal of dangerous debris from LEO would not only make launch and orbiting safer but should generate private sector awareness for the opportunities in related space industries. Eventually the potential value of this growing material resource would become commercially attractive and exploited. The collected availability of unprocessed scrap and other manufactured materials in space would ultimately set the stage for the recycling, production and assembly of finished glass, ceramic, plastic and metal construction products.
Recycling this reservoir of space scrap might then begin by shredding, pulverizing, liquefying or vaporizing the material and sorting the aggregate by magnetism, reflectivity, spectrography and centrifugal mass separation. The resulting metal. plastic, glass and ceramic powders could be directly used in additive manufacturing such as 3d printing, selective laser sintering and fused deposition modeling. Refined powders could then be smelted with solar furnaces for production of wire, sheet and plate products. Sheets and plates can be further fabricated for assembly with digital controlled laser or plasma cutting systems. Finished products created by additive manufacturing, such as sheet, rod, structural beams and tubing, could become the building blocks for a new generation of large-scale space structures. Made In Space’s Archinaut Ulisses proposes robotic, additive manufacturing for large space structures. The availability of sorted and refined materials in space would set the stage for the development of zero g material manufacturing and ultimately the assembly of large-scale structures.
Heat energy for liquefying, smelting, extruding and rolling can be obtained with focused solar energy furnaces. Robotic machinery, powered by solar electric, can be controlled and monitored from an Earth based command center. The scale of the refining operation might be contained in a very modest (possibly tabletop size) area; not nearly the scale of earth based factories. With continuous operation outside of the Earth’s shadow, even a concept demonstration prototype system would steadily accumulate usable ingots, powder and wire. The robotic-operated shredders, smelters and extruders should require infrequent visits for maintenance and upgrades. Working in the vacuum of space would have the additional advantage of minimizing oxidation and other contamination during smelting and shaping of high purity metal and alloys.
The constrained physical capacity imposed on launch vehicle payloads has always made large space structures uncommon. In-space manufacturing and assembly then presents the next best way to create large orbiting constructs. Space ports, interplanetary ships, orbiting hotels and extra-terrestrial habitat could be assembled (at least structurally) from the ever replenished supply of orbiting space junk. With a space manufacturing infrastructure established, the growing demand for raw materials, combined with more efficient collection systems, could make the collection of ever smaller debris economically advantageous. Improved methods of collection combined with the continual resupply of readily processed orbiting material, might forestall the necessity of more costly and energy intensive asteroid mining for raw materials.
Thus a multinational government investment in the development of an MEO space debris storage facility, while immediately mitigating the existing and growing population of space junk, could promote the re-use of available orbiting materials. A collection of orbital scrap could incentivise commercial collection and transport of LEO debris while fostering a profitable recycling system for shredding, pulverizing and reprocessing to provide structural components for the next generation of large-scale, space assembled structures.
Once space manufacturing and the assembly of large-scale structures become a functional reality, a natural demand for resources such as orbital scrap materials would be created at which time the removal, storage and recycling of space debris will become a profit driven, competitive, commercial enterprise.
Relativism of a Straight Line
Consider a simple problem about centrifugal force. Imagine you stood at a pole of the earth, say the North Pole and constructed a wheel whose axis extended from the calculated axis of the earth. (This wheel would spin parallel to the plane of the equator.) Imagine that this wheel contained a precision force gauge whose output you could remotely read as the centrifugal force at the wheel’s rim.
You spin the wheel clockwise (from the top view) and recorded the force at the wheel’s rim. By spinning in the clockwise direction the wheel would be spinning opposite that of the earth’s rotation. Would the rotation of the earth, in effect, be subtracted from the spin of the wheel? Would the centrifugal force readout be higher if the earth did not rotate?
Now you stop the wheel and spin it in the opposite direction, i.e. counter clockwise at precisely the same speed (RPM) relative to you standing on the earth. Again you read the output of the force gauge and record it. In this direction would the earth’s rotation add to the wheel spin? Will the output of the second (counterclockwise) spin have an added centrifugal component that would show up on the force gauge? Or will the wheel produce the same centrifugal force? Does your effort, imparting a force in the wheel, somehow create it’s own frame of reference relative to you (the force) and the wheel? Or could the proximity of the wheel to the earth’s gravity somehow envelop and include the wheel in its rotational motion allowing the two opposite direction spins to produce an identical force output?
The speed of the wheel obviously depends on where you stand when you determine the wheel speed. If you float in space above the pole you will see the wheel spinning at different speeds. The counter clockwise wheel spin being 2 Revolutions per day (RPD) faster than the clockwise direction. And from that point of view you would expect the centrifugal force to be higher in the counterclockwise direction. If you took the remote readout of the force gauge in space above the pole, would the readout be different?
Centrifugal force is derived from the inertia of an object in motion (which prefers to travel in a straight line). Inertial resistance to that ever-changing circular motion produces the force. It is technically called angular momentum. Also, the velocity of that body in motion determines the amplitude of that force. So the question boils down to the immediate straight line moment of velocity of a point on the rim. However, this brings us back to the original problem. If you measured the moment of velocity at a point on the rim standing at the at the earth’s pole (or anywhere on the earth), it would again be the same in both directions. If you measured the moment of velocity from space, it would again be higher in the counter clockwise direction. It seems simple Newtonian motion is relative to the observer’s position and motion.
Our individual motion standing on the earth is far from simple. We are not only moving on a spinning earth but also orbit around the sun, which is moving through the galaxy. This galaxy is spinning around its center and moving relative to the local cluster. And this cluster is moving relative to the more distant background galaxies. So even the task of throwing a ball in space, which would appear to the thrower to go in a straight line, (producing no force of angular momentum) would not be moving in a Newtonian straight line if observed from, for instance, the moon.
So is the straight line motion of the ball solely determined by the force applied, from the point of applied force? If so the wheel would produce the same centrifugal force in both directions as the applied force is equal (though opposite). If the motion of a thrown ball is not a universal straight line but follows the curves and spins of an orbiting earth and moving sun, then the centrifugal force of the wheel will be different between a clockwise spin and a counter clockwise spin.
If the observer’s motion determines weather a line of motion is straight or curved, then consider an observer above the earth, watching a bullet fired from the equator to the north pole. It will naturally take the shortest path, (a straight line for us watching on earth). To eliminate any confusion about following the curvature of the earth I have will make the northern hemisphere a cone with the equator as the base and the north pole the apex and removed the attraction of gravity. From the firing position on the equator the bullet would describe a perfect straight line. From space above the rotating cone the path of the bullet would describe a tightening spiral. So the outside observer would see the bullet traveling a curved path and therefore assume that some outside force was causing the mass to travel a path other than a straight line. They would also assume that there was a side force on the projectile produced by the angular momentum. They would expect anyone traveling inside the bullet to experience this side force as one in a car when turning a corner.
So where lies this frame of reference for determining what is a straight line? The answer could come from the measurement of centrifugal force itself. It could be determined by performing our original experiment of spinning a wheel. If the centrifugal force is identical with both spins, the frame of reference is the wheel itself. If it is additive and subtractive by the earth’s rotation, the frame of reference then occurs in a larger context beyond the earth’s influence.
If the later was true, this experiment on a larger scale could determine the absolute frame of reference for all motion. It would be possible that the reference frame could be the universe and with a large enough wheel we could determine if the universe itself is in relative motion. We could measure this by a series of wheel spins (or tethered weight spins) in space with a precise force sensor. By changing the orientation and speed we could find the condition of zero angular momentum, when the wheel is at rest relative to the universe. The wheel speed and orientation would match the rotation and orientation of the universe. This would also mean that our universe not self contained but part of a larger framework possibly containing other multi-verses.
However, if the reference frame is that of the point of origin of the applied force, then every moving object in the universe determines its own straight line. And producing a universal straight line would be impossible. It would mean that straight line inertial motion is as relativistic as the speed of light. That any straight line motion is determined by the last applied motion changing force. Traveling in space (away from any influencing source of gravity) you would know that you were going in your own straight line but it would be impossible to prove it by observing outside motion.