Wednesday, August 24, 2016

Make the Dark Side of the Moon Cool (Why We Should Build a Space Elevator on the Moon version 0)

This post will be part of a series, intended to serve as a reference point for how you might potentially write a white paper, in this case on promoting space elevators on the moon, each post in the series will build on the previous document, until the language meets the necessary level of professionalism.  The author asks that readers provide feedback and suggestions for this document.  Who knows maybe someone might actually use the idea.

Every year NASA gets a hyperbole inducing volume of suggestions* for how they should invest their research dollars, ranging from congressional line items, mandating what should be researched over the coming years, letters from school age children making their own suggestions on potential science experiments (like my little brother did when he was in the fifth grade), more seriously are research proposals coming from well reputed scientists working at various research institutes, and once in a while chicken scratch on the back of envelopes and napkins outlining how we really can build the starship Enterprise.  This article hopes to be a bit better than a back of the envelope mission proposal.

A major pain point of any mission sent into space from the planet Earth is minimizing how much mass is required for the mission.  Even relatively massive pieces like the lunar landers used in the Apollo missions where optimized down to the last gram.  As humanity's aspirations to the stars begin to become actual mission plans, those responsible for planning the mission will benefit from having as diverse a portfolio of design and system solutions as possible.  When planning a mission, sometimes engineers can plan on further improvements in technology to save mass, a key example would be the computers that control a space craft, during the Apollo missions, astronauts would brag about a machine that could fit in a single room, that same level of processing power now fits in your cellphone, not only that, the smaller computer requires far less electrical power, continuing a virtuous cycle of design.  Solar panels have also become far more efficient, with panels on satellites converting roughly 40% of the sunlight they are exposed to into useable electricity, compared to 14% in 1961.  Future missions might also benefit from the use of micro-gravity manufacturing techniques, instead of relying on components that must be strong enough to survive the harsh acceleration of gravity, engineers at firms like Made In Space, are producing 3-D printers capable of creating a range of potential space craft components.  These developments are exciting (at least for space and engineering nerds), but they are still relatively limited, because all of these technologies and solutions, need to be launched from the surface of the Earth, what if we had an alternative?  Enter the world of space mining.

The boom of space mining firms like Planetary Resources and Deep Space Industries have sparked imaginations around the world, is humanity finally getting ready to live in the science fiction world's we used to dream about?  Fingers are most definitely crossed.  While mining asteroids for useful materials is exciting and over the coming generations our descendants will most likely be incredibly dependent on industries based around converting asteroids into useful materials there are resources much closer to Earth that should be considered.  The dark side of the moon is a near perfect near to mid-term location for humanity to expand its reach.  The lunar surface has incredibly large volumes of readily accessible oxygen, iron, and aluminum, while there are other resources to gather from the lunar surface, this article is intended to make a case using the most readily available and understood resources.  With access to relatively cheap sources of oxygen for rocket engines, iron for radiation shielding, and aluminum for structural elements, engineers would be empowered to change how they design deep space missions.  Instead of having to launch a probe with all of its fuel, future missions could fill up on oxygen before continuing on to other celestial bodies.  Future space stations would no longer need to launch with complex walls intended to minimize micro-meteorite damage while minimizing mass, instead, tiles of iron could be added to the exterior of the station on an as needed basis.

Outlining cool uses for the basic chemical elements of lunar regolith is all well and good, but how will future missions gain access to the surface of the Moon to use these resources, two words "space elevator".  A space elevator is roughly speaking, a long ribbon of material that has been placed in orbit around a planet or moon, where one end of the ribbon is in contact with the surface, on the other end of the ribbon, there is a counter weight.  The overall length of ribbon is dependent on two characteristics of the celestial body they are built around, the more massive the planet or the slower the day, the longer the tether needs to be.  The pull of gravity also impacts how strong the tether needs to be, on planet Earth you need tether's made out of materials that can, currently, only be made in laboratories in small quantities.  For a tether on the moon the elevator can be made from materials currently available, for example kevlar.  With an operational space elevator on the surface of the moon, future missions to and from the moon would only require sufficient fuel to dock with the space elevator, as opposed to requiring sufficient fuel to safely land on the surface and then fight against the lunar gravity well on the return trip.  Getting to the point where materials are routinely going to and from the surface of the moon will take many years, but might have a timeline as follows.

Phase 0:  NASA and partner organizations request contract bids for companies that will build the first Lunar Elevator

Phase 1:  The first space elevator satellite is deployed on the dark-side of the moon (Pink Floyd album sales experience a light resurgence).  The system is only capable of moving payloads of a few dozen kilograms per container (potentially more, but we are being conservative in estimations)   The small mass flow rate is not considered useful for industrial applications, but allows scientists of partner nations to do far more analysis of the chemistry of lunar regolith

Phase 2:  Improved versions of the initial space elevator probe are now deployed in a constellation around the initial space elevator satellite.  The larger number of probes allow the space elevator consortium to start shipping semi useful quantities of liquid oxygen and other resources.  One client for the liquid oxygen are space mining firms, looking to minimize their launch costs while pursuing asteroids further afield.

Phase 3:  Using the Phase 2 constellation, the Lunar Mining Consortium beings to manufacture their next generation space elevator, this elevator is intended to allow the transportation of thousands of kilograms at a time.   At this point there are multiple small semi-autonomous research stations and mining sites on the dark side of the moon.

Phase 4:  The Lunar Mining Consortium continues to add to the initial space elevator system.  There is a habitat at stationary orbit, serving as a depot and manufacturing facility, where space craft can refuel, receive modifications and exchange crews and/or cargo.  The number of facilities on the lunar surface continue to grow.  A small number of mirrors have been added to reflect sunlight towards various research stations to ensure they receive enough power during the Lunar night

Phase 5:  The elevator has multiple termination points across the lunar surface, including the north and south poles.  The mirrors now ensure that lunar facilities now only require battery power for <10% of the Lunar night.  Lunar manufacturing capacity has reached the point that more than 20% of the material put into space in a given year came from the Moon.  Only organics and more complicated electronics are likely to still launch from Earth in the coming decades.  As a result of the shear volume of materials arriving and departing the Lunar Elevator Station, engineers have added even larger engines and rail guns to preserve the elevator's orbit.

Phate 6:  Using lessons from the Lunar Mining Consortium, humanity forms the Mars Elevator Group, and begins to outline a Martian space elevator, opening up Mars for more ready colonization.

The motivations for developing space mining are quite reasonable, the more materials that can be harvested outside of the Earth's gravity well, the greater flexibility our civilization will have.  That being said there needs to be a dollars and cents argument made to those who hold the strings.  The easiest is for rocket fuel.  for traditional rockets that use hydrogen and oxygen, the oxygen makes up 8/9ths of the mass of the fuel needed (this doesn't include the tanks holding the hydrogen and oxygen).  Now imagine you have a reasonably affordable source of liquid oxygen on the moon.  Now you need way less mass devoted at launch to your liquid oxygen supply.  For crewed missions to Mars that will, potentially, be a massive saving.  Now to developing the space elevator itself, in theory engineers could make a massive rail gun on the surface of the moon, and use that to launch materials into space, true, but the applications are reduced, building a space elevator on the Moon allows scientists to have a  real test bed for space elevator technologies, these technologies could inform how we build a space elevator on Mars and maybe one day the Earth.
The rational behind suggesting the formation of the Lunar Mining Consortium is to promote international collaboration, projects like the ISS have done wonders for promoting cooperation here on Earth, a massive engineering project where dozens of governments can share in innovations and natural resources will hopefully promote a more unified Earth.

Well thanks for reading version 0, feedback and notes are appreciated.

*honestly the author isn't sure how many ideas NASA gets, but assumes it is a lot.

1 comment:

  1. this is more of a reminder for myself on a later date, but feel free to read the source article now http://www.vice.com/en_au/read/how-an-australian-university-student-beat-nasa-at-their-own-game, a new class of plasma engine that uses metal as a fuel source. Which makes a lunar metallics mining operation that much more valuable

    ReplyDelete