ISRU

Intro

In order to effectively live in space, the cost of obtaining the needed goods in space must be reduced. This can come from either lowering the cost of shipping mass into orbit (Cheap Access to Space) or devising ways of producing the resources in space (ISRU) to avoid the need of shipping the goods into space. ISRU stands for In-Situ Resource Utilization. The goods that could be produced in space include just about anything that can be produced on Earth, including power, water, air and spaceship propellant.

Producing Power

	kW	kg	kW/kg	$/kW
Today
Nuclear	50000 kW	500000 kg	0.1 kW/kg
Solar	200 kW	2000 kg	0.1 kW/kg
Near Future
Nuclear	40000 kW	200000 kg	0.2 kW/kg
Solar	2000 kW	2000 kg	1 kW/kg
Far Future				Invest. Req.
Nuclear	20000 kW	20000 kg	1 kW/kg
Solar	30000 kW	2000 kg	15 kW/kg

Power is the most essential resource for living and operating in space. The easiest way of obtaining power in space would be to ship nuclear power from Earth. This could include an entire nuclear reactor, a radioisotope thermoelectric generator or simply the fuel for the reactor. A lightweight, efficient, long lasting refuelable nuclear reactor would go a long way towards supplying the power needs of a colony. Project Prometheus is the name given to the NASA project to develop nuclear power sources for space.

Although nuclear reactors can be shipped to Mars to supply power, it is also possible to use more local resources to build the infrastructure to produce power. This could involve either mining nuclear fuel on Mars, local production of solar panels (using ISRU solar cells), geothermal power or solar thermal power. The conversion of heat to electricity can be done by solid state thermal electric devices, evaporation of metals and using a turbine in a thermodynamic cycle.

Another idea uses solar power satellite technology. [1] A solar panel array in orbit around Mars beams power to the surface using microwave frequencies. A large (20 km²) rectenna is required to receive the power, however a bootstrap (1.5 km²) rectenna could power an iron ore refinery (Martian soil is up to 14% iron oxide) and manufacturing plant. Benefits over surface solar panel arrays include full power generation throughout the Martian day and night, immunity to dust storms, the ability to supply power to anywhere on the planet, and ease of manufacture compared to ISRU solar cells.

An important metric in this regard is kilowatts per kilogram (kW/kg). For ISRU power, manufacturing equipment dedicated to power production should be accounted for. The table presents current estimates.

Producing Propellant and Fuel

• See: Sabatier reaction

Producing Food

There are many aspects to producing food on Mars, including the design of the greenhouse, the preparation of the soil, crop selection, and crop harvesting. Some design aspects include the thermodynamics of the greenhouse, whether it is built with local resources or imported resources, the materials used to build the greenhouse and whether it is built on Earth or on Mars.

Electronic components

Modern-day electronics have both become extremely complicated and laughingly cheap. While the manufacturing of modern processors involves hugely expensive equipment and infrastructure, economics of scale make it possible to invest literally tens of billions in chip manufacturing plants that produce processors that cost only dollars individually.

Given the fact that chips have become increasingly small, and thus lightweight for their capabilities, it will probably take a long time to make it economically viable to manufacture them on Mars instead of producing them on Earth and sending them to Mars.

Chips, however, only count as a mere weight-fracture of modern electronic devices. Take a desktop computer, for instance: The power supply unit, the capacitors, the printed circuit board, on which the electronic components are placed, connectors, keyboard, screen, printer, scanner... Take the bulk of the mass.

If only the In-situ manufacturing of transformers, a fairly simple task, could be accomplished, this would save a huge amount of mass to be shipped up. Printed circuit boards, made out of fibre-glass, would also be quite simple. Case, connectors, keyboards, are mechanical systems, discussed elsewhere.

That leaves us data-storage, capacitors, and various output devices. Arguably, data-storage will become a non-mechanical thing in the near future (Flashdrives, memory sticks...) and will probably be shipped from earth for a long time too.

New Mars Discussions

• Lunar Carbon?

References

• Advanced Automation for Space Missions, NASA, 1980.
• t/Space Final Briefing (PDF), NASA, 2005.
• Geoffrey A. Landis, Silicon Production on the Moon.
• Maier et al., Purdue Advanced Lunar Apparatus, Maximizing Excavation and Delivery of Experimental Sciences (PDF), School of Aeronautics and Astronautics, Purdue University.Template:Stub