Compact Farms

In my last two blogs, I wrote about two different types of propulsion for use in space. These propulsion methods, or at least the ion thruster, would be most useful for long distance space travel. Once you start going on longer and longer trips, you start to run into problems. One of the major ones is the life support. One of the most prevalent problems with supporting life on a space ship is food. The most obvious way to get food is to bring it with you. This works fine for shorter missions, but it becomes impractical quickly as the mission lengths increase.

A solution to this would be making a farm. Not farming things like corn and wheat like on earth, that would be to inefficient and inconsistent. It would be an algae farm. This could be made extremely efficient by having the farm be on stacked trays with built in light sources, to maximize use of space. The algae could be genetically modified to produce the amino acids and some of the nutrients that we cannot produce and require in our diet. This farm would also help to eliminate carbon dioxide and produce oxygen. The water and nutrients for growing the algae would come from recycled human wastes. This type of farm would be self-sustaining, because we only borrow everything, so the total number of each of the atoms in the system stays constant. This cyclic nature makes this feasible for even the longest of trips.

The trays would consist of a repeating pattern of three layers. The first layer would be a solid layer for structural support and electronic housing that is reflective on one side. The second layer, attached to and powered by the first, would be a simple array of growing light LEDs embedded in a light scattering material to make growth more even. The third layer, between the growing light and reflective barrier, would be the algae populated nutrient solution. This solution would be constantly circulated through the air control system to exchange gases, and the waste processing to get the recycled nutrients.

This idea of an aqueous algae farm would be self-sustaining and very compact. This would become increasingly economical and efficient with increasing trip lengths. It would also be invaluable in “stationary” structures such as the International Space Station that will be in space and requiring food for years. Systems like this are the advancements that we need to make in order to do most of the things that are now thought of as mere ideas such as manned travel out of earth's gravity well or even out of our home solar system.

Nuclear Propulsion

In my last blog post, I wrote about a type of propulsion that would provide extremely high fuel efficiency with the trade off of using extremely large amounts of electrical power. What I will be writing about in this blog is a crazy sounding method of providing thrust that is practically the polar opposite of the ion thruster.

This method uses hybrid fission/fusion nuclear bombs as fuel. The idea is that the bombs would be ejected out the back of an extremely large space ship with a bell shaped protrusion attached to a giant “spring” on the back. When the bombs reached the edge of the bell, they would be detonated, and the half of the matter/energy cloud that has “forward” momentum would hit the bell, compressing the spring so that the energy is not pushing the spacecraft all at once (which would be the equivalent to nuking it.

The reason that it cannot just be any bomb, but has to be a nuclear bomb, specifically a fusion bomb, is that the energy produced per weight of a nuclear fusion bomb has no man-made comparison. It is not just a fraction more efficient, it is millions of times as efficient. Plutonium, being 1.75 times as dense as lead, is quite dense, but the hydrogen used in the fusion part of the bomb is the lightest element in existence, and produces multitudes of the power as even Plutonium.

One obvious problem would be the manufacturing of the nuclear materials. This would be quite simple with minor modifications to any of the reactors from my previous blogs, or even current nuclear reactors. I am not going to say anything else related to the manufacture of nuclear bombs, because, well...

Another problem would be the bell structure. It would have to be light, otherwise you ended up where you started. It would have to be able to withstand massive temperature variance from the near absolute zero temperature of space to the extreme heat of the nuclear flash. It would also have to block the radiation from the nuclear blasts from the ship without damaging itself. And, of course, the shock waves from the nuclear blasts that would be its primary purpose. This is unfeasible with our current material technology, but perhaps in a later blog, I will discuss some materials that could be used to accomplish this, but for now, I am going to stay on the topic of space.

Ion Thrusters

In my last blog post, I wrote about an idea for a more efficient method for getting things into space. I also mentioned more efficient engine design with lower throughput. That is what I will be writing about in this blog post. The type of propulsion that I will be writing about will be an ion thruster. This type of thruster is only viable in space, it does not produce much thrust, but it uses only absolutely tiny amounts of fuel. It works by ionizing xenon and repelling the ions electromagnetically at extremely high velocities.

There is one main positive quality to this type of propulsion (high-five to whoever got that joke). This is the fuel efficiency. It is more fuel efficient because of the higher speed at which the working mass is ejected. This is due to Newton's Second law which is commonly shortened to F=ma, or Force equals Mass times Acceleration. This means that in order to decrease the amount of mass required (fuel), you would need to give it more acceleration. This is achieved by the electromagnetic acceleration. While the space shuttle's main engine had a exhaust velocity of about 4.5km/s, the ion thruster would have an exhaust velocity of about 20-50km/s, making it much more efficient. An example of an achieved efficiency with this type of thruster is the Deep Space 1 spacecraft, which accelerated by 4300 m/s with only about 74 kg of xenon.

There are also two major negative qualities to this type of propulsion (same joke). One of these is the fact that it cannot be used in atmosphere. The electrical fields and electrodes require a near vacuum to function. The second is the low thrust. The thrust of current ion thrusters range from 20 to 250 milinewtons, which is tiny compared to the Space Shuttle Main Engine's 2,279 kilonewtons of force. The Space Shuttle Main Engine has about 9,116,000 to 113,950,000 times as much thrust.

Overall, in my opinion, the idea of low thrust, high efficiency engines should be explored more. In my opinion, the lower thrust is counted for in the less fuel it has to push and in the increased fuel economy. In my opinion, these types of engines could be how we power long distance ships for the future.

Rotating Skyhook

For my last blog post, I wrote about a problem with space travel. This problem was fuel. For this blog, I will be writing my opinion about an idea proposed by scientists in 1976 and 1994 for getting an object into space, which is the main reason for the need for so much fuel and for such powerful engines. This idea is the rotating skyhook.

The idea behind a rotating skyhook is a massive space station in orbit that has a tether, or hook, attached to it that rotates in the direction opposite of the orbit of the station. The orbiting station will allow the hook to stay suspended “from the sky”, hence the name. The opposing orbital spin and tether spin will have the effect of making the hook travel in an epicycloidal pattern around the planet. This means that the hook would be momentarily stationary relatively low in the atmosphere, allowing it to travel deeper into the atmosphere without drag, and allowing the object to be attached to the hook at very low speeds. It also will have the interesting visual effect from the ground of a hook on a tether suddenly descending vertically from the sky, slowing, stopping, and reversing to leave. The hook would lift the object away from the planet and accelerate it so that when it is the farthest distance from the planet, it would be moving very fast, allowing it to enter orbit or leave the planet very efficiently.

There are some problems however. The force of lifting the object into orbit would have an equal and opposite effect on the station. This means that every time an object was lifted, the station would move to a lower orbit. This is not as bad as it sounds, the station could have a small amount of thrust over a large amount of time, balancing to the force to lift the object. This can be achieved by more efficient but less throughput propulsion methods that I will be writing about in some upcoming blog posts. The other problem is that the station would have to be many multiples of the mass of the object being lifted. The tether would also have to be very light and strong, but nothing past what we are capable of. These two problems would lead to an extremely large cost to build.

Overall, in my opinion, this is one of the less outrageous methods of getting to space more efficiently. I feel as though the costs would be massive to build and require cooperation of nations, but that the benefits outweigh the costs.

Space Shuttle Propulsion

                In my last couple of blogs, I have been writing about nuclear power. For this blog and the next few to follow, I will be talking about some things relating to space travel. The subject that I will be writing about in this post will be the problems with propulsion for space travel today. For simplicity, the space craft that I will be examining will be the Space Shuttle.

                 The first thing that is a major problem is the fuel. An amazing amount of fuel is required to get anything into space. The fuel for the space shuttle weighed a total of 3,869,475lb, or nearly 1935 tons of fuel! That is more than 23 times the weight of the empty shuttle itself!

There were three different types of fuel used in the Space Shuttle. One was a mixture of liquid hydrogen and liquid Oxygen. This was contained in the Space Shuttle external tank, weighing a total of 1,621,722lb. This burns almost invisibly, and is the fire that is coming out of the bottom of the shuttle itself. The second type of fuel was a mix of 69.6% ammonium perchlorate as an oxidizer, 16% aluminum as a fuel, .4% iron oxide to control burn speed, 12.04% PBAN (Polybutadiene acrylonitrile) to hold the fuel together and act as a secondary fuel, and 1.96% an epoxy curing agent. This was contained in the Space Shuttle Solid Rocket Boosters, weighing 1,100,000lb each for a total of 2,200,000lb. This is the fuel that causes the classic huge plumes of smoke and fire during a launch. The last type of fuel used in the Space Shuttle was two chemicals that, when mixed, combusted to produce thrust. These two chemicals were monomethylhydrazine as a fuel, and dinitrogen tetroxide as an oxidizer. These were contained in the Space Shuttle Orbital Maneuvering System, with a combined weight of 47,753lb. These thrusters are small and mostly used in space, so you cannot see them during the launch.

All three of these fuels are either toxic and carcinogenic or cryogenically cooled, making them very difficult, expensive, and dangerous to handle. They also are impractical for more mass or longer travel, as this would require more fuel. This increase in fuel would need even more fuel to lift it. This means that at a certain amount of weight or distance to travel, it would simply require too much fuel or be too massive to achieve liftoff. In my opinion this needs much improvement. In my next blog, I will be writing about some ideas for improved fuel efficiency and different types of engines and fuels.

Comparison of hybrid reactor

                In my last blog, I described my design for a nuclear reactor core that would, in my opinion, be superior to the current design in multiple ways. In this blog, I will be comparing my reactor design to the design of modern day fission reactors.

                The first point of comparison is safety. This reactor would have a much higher operating temperature than current reactors. This makes a meltdown sound much more dangerous, but in fact it would be less of a problem, because any explosion that would occur would simply be caused by too much heat or pressure, not an uncontrolled nuclear chain reaction. The likelihood of a meltdown is also drastically reduced because of the plethora of failsafe mechanisms and intrinsic safety of the reactions.

                The second point of comparison is the production of nuclear waste. This nuclear reactor would produce only short half-life radioisotopes that could be used in simpler power plants as fuel because they would produce large amounts of heat from radiation that could be used to generate electricity, or possibly even for other uses such as industrial heating. This reactor would also be able to consume long half-life nuclear waste as fuel, solving many of the storage and environmental concerns that are usually associated with nuclear waste.

                The last point of comparison is the availability, sustainability, and economic feasibility of fuel. This reactor would take two types of fuel, one with relatively large atoms and one with relatively small atoms. The small atom fuel, for the fusion reactor component, would be produced in the reactor from the cooling water. The neutrons used to produce this would come mostly from the splitting of the larger fuel. This larger fuel could be nuclear waste as mentioned above, or it could be thorium or natural uranium. This would mean that there would be no need for processing, and would theoretically last us millions to billions of years. This means that it would be considered a renewable resource.

                In comparison to current nuclear reactors, or worse, coal plants, in my opinion, this would win by a landslide. So what would this all mean for you, the average person? The main thing that it would mean is dirt cheap electricity. This would cause an increase in the use of electric vehicles. This increased use of electric vehicles coupled with the zero emissions from the power plant would remove the top two sources of greenhouse gasses. Overall, I think that the benefits of this would be massive and cause good effects across almost everything indirectly economically or environmentally.

A hybrid reactor design

                In my last few blog posts, I have described some ideas for nuclear power that I think are worth considering for use in the future. In this blog post, I will be writing about what I think would be the best design for a nuclear reactor for the future. My reactor design is a hybrid of the three reactors that I discussed in my previous posts.

                For the design of the nuclear reactor core, it would be a toroid, or donut shape, with three shells. The center would be a combination thermonuclear and inertial confinement fusion reactor. The first shell would be molten fluorine and fuel salts. The second shell would be a circulated coolant molten salt. The outermost third layer would be a layer of supercritical water coolant.

                The plasma in innermost fusion reactor would be spinning which will make the heavier elements, or wastes from the fusion reaction, be centrifuged out to the sides of the chamber for removal. While wastes are being removed, more fuel could be constantly added, eliminating the need to stop and refuel.

                The first shell of the reactor would be the same as a molten salt reactor, but would be able to use much more nuclear waste or depleted uranium as fuel, as the fusion reactor would produce high energy neutrons similar to those produced from a particle accelerator. A lot of the heat from the fusion reactor would be deposited in this layer, as the salt would be very dense. The salt would be continuously circulated and processed to remove wastes and add more fuel, eliminating the need to stop and refuel, which is a major problem with the molten salt reactors.

                The second shell would be the main cooling shell. It would be some other molten salt that would be used to transfer the heat to the power generation part of the reactor. The extremely high operating temperature allows very high thermodynamic efficiency.

                The outermost shell would be a layer of water that would be used for further heat transfer, but also would absorb many neutrons from the reactor, making deuterium and tritium for use in the fusion reaction at the center.

                This design would have most of the benefits of the constituent designs while minimizing the negatives. In my next blog post, I will compare this design to the design of the nuclear reactors that we use today.