Earthbags for Mars Colonies

NASA recently announce a competition to develop means of using in-situ materials on the Moon or
Mars to build structures.

NASA suggests, and no doubt most people will pursue, using adhesives mixed with regolith or some type of sintering in order to create the structural elements needed. Both of these methods are non-optimal.

Sintering is a highly energy intensive process. Considering that large nuclear reactors will not be sent to Mars sintering is not a means of creating structures quickly or efficiently. They my look nice and the technology is fascinating and eventually viable it will not be until space power-source capabilities increased significantly.

Adhesives are a simpler process. But they still rely on chemistry which has to be extensively explored. The temperature, atmospheric composition, and even wind could limit the viability adhesive chemical reactions on Mars. So to attempt to create a type of concrete or glue I would not consider reliable.

With adhesives there is also a high material weight cost for transport. It is unlikely that everything needed to make beams and bricks using adhesives or additives will exist on Mars. Tanks of chemicals will have to be transported and safely landed on Mars. Unless again high energy requirement systems are feasible.

The solution much be mechanically self-reinforcing. An igloo or a geodetic dome.

What the most basic level every mineral on Mars is dirt. Particles which, when compressed become essentially solid. The method I decided to pursue was the used of sandbags.

Sand bags require minimal transported material in order to create high volume constructive elements. And bags can be changed to tubes. A single polypropylene tube could be filled with martian dust and behave like a 3-D printer creating a beehive-like igloo structure. A Martian Coil-Pot Hut.

Initially I thought that the bags would have to be specially designed to insure that during settling the sand within the bags would not be able to  cause bulges or gaps which would cause a structure to fail. But as I did my research I found earth-bag structures.

Earth-bag structures are exactly what I was imagining with my sandbag concept. Bags are filled, compressed, and then stacked. These structures are generally igloo shaped but can take square form.

With more research I found several structural analysis dissertation papers on earth-bags which justified their structural integrity.

The benefits of such structures on Mars is that they can be built by hand without complex machinery. But in order to prepare ahead of time, a large 3-D printer-like system could be delivered to build the huts.

The huts have a high thermal mass so they will not require large amounts of energy to heat. This mass of soil also serves as radiation protection. And since they are using large quantities of dirt the huts can have a basement increasing the total volume of the structure.

Earth-bag, or in this case, Mars-bag structures are an efficient and almost optimal solution for preliminary buildings on Mars using in-situ materials.

Note: Since the primary challenge with earth-bags is that fact that the sand or soil inside of them can shift, they would actually be even more optimal on the moon where the regolith is un-eroded and therefore will have a higher shear resistance, that is sliding over itself inside of the bag.

Flywheel-Powered Submarines

Flywheels store electrical energy as kinetic energy. Basically you spin up the wheel very fast with an electric motor, keep the wheel in a vacuum, and when the energy is needed the motor acts as a generator. Flywheels also have an efficiency of 80-90% as compared to most other technologies (li-ion are in the same range)

The trouble with flywheels, in mobile platforms, is that they have to be sealed in a vacuum container, and they induce gyroscopic forces. They are also relatively complex compared to batteries, though they are technologically simple.

They should be used in personal submarines. Flywheels are a great, heavy, and dense power source. They can provide stability and power to submarines and be rapidly recharged.

Submarines also have the heavy duty structure to support the mass and protection that comes with a relatively low-tech flywheel.

If implemented cleverly, using low tech components. Flywheels would be superior to batteries when applied to submarines. (thinking more about it they would also be viable for electric boats, since ships already use flywheels in some cases)

Autogyros: Great Electric Aircraft

I apologize for the roughness of this post. I will improve it soon.

An autogyro is a an aircraft that uses forward motion to spin a rotary wing, allowing for safe flight
at slower speeds and the potential for VTOL. But their design also lends itself to becoming electrically powered.

Autogyros were developed in the early days of flight in Spain.  Originally they were basically planes which used a rotor instead of a wing. A rotor is able maintain speed, and therefore lift, independent of the speed of the aircraft. This means that an auto gyro can move very slowly through the air and not stall as a conventional fixed wing plane would.

There are two ways of thinking about this. The rotor is basically creating a large circular wing above the aircraft, or it is several small wings moving very quickly through the air. In both situations lift is increased, and slow speeds of the craft are possible. Use which ever mental model you need for it to be clear.

Now an autogyro was originally just a plane with a rotating wing. But development went far enough that power from the thrust engine could be transmitted to the rotor so that an autogyro could launch vertically, then the power to the rotor could be disengaged and it could simply rotate freely for forward flight. A auto gyro can literally switch from vertical to forward flight just by popping a clutch. No complex transitions are needed such as in the case of tilt-rotor aircraft like the Osprey.

The autogyro was developed into an VTOL airliner in the early 1960's but the Fairey Rotodyne project was cancelled for lack of funding.

Fairey Rotodyne intro video

The fact that the primary rotor is only used for liftoff and then is simply a passive wing in forward flight is a great efficiency benefit to an electric aircraft. Power is consumed on lift-off and then, in forward flight the system is as efficient as an airplane. There could even be the potential for a type of air regenerative braking as the rotor acts like a wing.

The autogyro is also very safe as personal air vehicle. Its basically non-existent stall speed and lack of complex transitions makes it potentially safe for consumer markets. The autogyro is one of the best technologies for an electric personal flying car.