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Pedaling the Stars

Exploration and colonization of the Moon and Mars will require transporting larger loads and traveling greater distances than is practical for humans on foot. Clearly some type of surface vehicle will be needed to effectively explore and colonize. A question to ask is what shape will the vehicles take? What may seem a radical concept is that the vehicles should be human powered. Though this may seem like an improbable solution it actually has a number of benefits over other power sources.

The biggest obstacle to human powered vehicles used beyond Earth is that current space suit designs make this all but unworkable. The problem is that balloon suits used make just walking around heavy exercise. I have argued in an earlier post, Fall Fashion for the Extraterrestrial, that this is an issue that will need to be resolve if we hope to send humans to space for extended periods. The mechanical counterpresure suit suggested should allow mobility similar to a wet suit which will be more than enough to allow the use of human powered vehicles.

One of the biggest advantages of a human powered vehicle is that it will be far lighter than any powered option. The average bicycle weighs about 15 lbs. Though a vehicle designed for transporting the crew on the Moon or Mars will be larger, with the use of high tech materials the basic vehicle will likely only weigh about 2 to 3 times that. That is still less than an average car battery[1] and one tenth that of the Apollo Lunar Rover Vehicle[2]. This provide a huge advantage in launch weight. A vehicle this light can be picked if it somehow gets stuck or to get around an obstacle or carried if it breaks down.

The performance that can be expected from a human powered vehicle is likely more than one might expect. From person experience I know that a person who is in moderately good physical condition can travel and average of 50 miles a day by bicycle carrying 50 lbs. of gear. Rickshaw drivers regularly carry 2 passengers. On the Moon and Mars two factors will allow human powered vehicles to have much higher performance. The most obvious is the difference in gravity, on Mars three times the load and twice that on the Moon. The other is that the biggest limit of the speed of a human power vehicle is air resistance. With little or no atmosphere a human power vehicle should be able to cruise about as fast as is safe to travel over difficult terrain (about 25 mph)[3]. On Mars a human powered vehicle should be able to carry at least 1,000 lbs. of passengers and cargo and possibly a good deal more than that. Someone in good shape should be able propel range at least equal to that of any powered vehicle.

Human power vehicles also excel as all-terrain vehicles. Back in 1897 the US Cavalry experimented with troops mounted on bicycles. A troop of buffalo soldiers traveled 1,900 mile in 40 days from Missoula, Montana to St. Louis[4]. Most terrain you can cover on foot you can ride a bike over. As I mentioned earlier a human powered vehicle can also be carried over extreme obstacles. Consider how literally some people take the term “mountain biking”.

Mountain Biking

Rugged and Robust

Human powered vehicles is a very old technology. Except for detailers the general design of today’s bicycles is almost unchanged from the design developed of 125 years ago. Even though the basic design is old technology the bicycle’s popularity has resulted in a great deal of recent development. What this means for a human powered vehicle for EVA is that almost all the technology needed to make it work can be had off the shelf. Mountain bike designs have focused on a bike that can take a great deal of punishment. A human powered vehicle will have much fewer points of failure than a comparable motorized vehicle.

In the event of an equipment failure just about everything is easily repaired. Part of the reason for this is that a major points of failure are in the drive train. All parts and tools needed to entirely replace a drivetrain can easily be carried along. Repairs in the field would likely take little more than an hour for any but the most catastrophic failures. Even cracks in the frame could likely be temporarily repaired with a splint and heavy duty duct tape.

Active Crews are Healthy Crews

A side benefit of using human powered vehicle is that it will improve crew health. One of the main concerns of extended stay beyond Earth is the loss of bone and muscle mass. It is well know that vigorous physical activity prevent this issue. Especially with respect to Mars missions it would provide a double purpose to the required exercise in transit. If the designers are clever this could also provide extra power for the ships systems.

Shape of the Next Rover

The design of a human powered EVA vehicle will not be a 2 wheeler. The biggest reason is that even with much more advanced space suit design keeping balance will be challenging. Also 2 wheelers are not ideal for carrying cargo. Much more likely will be a recumbent with 3 or 4 wheels. This type of design would be able to be both very stable and provide room for passengers and cargo. The tires are unlikely to be balloon tires. A more likely design would be the Michelin Tweel airless tire design[5]. Part of the cargo may be auxiliary life support. This would likely be a larger version of the personal life support pack that each member of the EVA team has. It would allow the personal life support to be saved for when the crew is moving around on foot.

The Role of Powered Rovers

Though human powered vehicles may be ideal for moving the crew and much of their equipment around there will be many things they can’t do. Though they may not be needed for exploration missions colonization will require loads that a human powered vehicle can’t move and will be needed for jobs like excavation where human power is not likely to be practical. Also remotely operated vehicles will be useful for scouting and other uses. As they will be unmanned they will need a motor.

  1. http://www.carsdirect.com/car-maintenance/car-battery-weight-average-weight-expectations-for-popular-models
  1. http://www.astronautix.com/craft/apololrv.htm
  2. http://www.avdweb.nl/solar-bike/energy-requirements-of-cycling.html
  3. http://www.historynet.com/the-buffalo-soldiers-who-rode-bikes.htm
  4. https://en.wikipedia.org/wiki/Tweel

Lasso the Moon

presentation set-05.ai

I have been a personal fan of the concept of the Space Elevator (SE) since attending a talk by Bradley Edwards describing his work developing the concept. From that time I have always thought it was self-evident that this was the method that eventually most of the mass traveling between Earth and the rest of space would use. The problem to this point is that currently there is no material in commercial production that could be used to build the elevator. I have faith that material sciences will eventually resolve this issue but this could be decades away. There is a variation on the concept that is currently feasible, a Moon SE.

The Slow Boat to Luna

Currently the LiftPort Group is promoting the concept of and SE stretching from the surface of the Moon through the first Lagrange point (L1). Unlike the Earth based elevator this would not require a yet undeveloped material but would be possible with various existing materials such as Kevlar. Several modern synthetic fibers could be used because of the lower lunar gravity even though L1 is about 30% further from the surface of the Moon than GEO is from the surface of Earth.

Another difference is that while a SE from the surface of Earth is able to “self-counterweight”. A cable/ribbon of consistent cross section would need to extend almost 240,000 km beyond L1 to just counterweight the cable/ribbon to the Moon. For every 1 kg of payload to be lifted from the Moon you would need 33 kg in counterweight. A cable/ribbon of this length would possibly conflict with an Earth based elevator when one is built.

One advantage of a cable/ribbon this long is that a payload released from the end would come within 15,000 km of Earth. This could make returning to Earth from the Moon fairly cheap. If some way could be developed to capture payloads from the Earth any rocket able to deliver a payload to GEO would be able to deliver it to the Moon.

Like all space elevators the one to the Moon would be ideal for moving cargo. What it will not be very good for is moving people. Even if the climber moved at an average 1,000 km/h it would take over 2 days to make the trip between L1 and the Moon’s surface. The reality is the top speed will likely be less than half of that making the trip more like a week. A climber would be an extremely cramped space to live in for a week. It is unlikely that until space elevators are built for loads of at least 50 tons of mass that it will be used to transport people except in dire emergency.

What Good is It

A lunar space elevator would enable much more extensive exploration of the Moon’s surface. Exploration vehicles could be much more complex because their landing would be very soft and because potentially they can be returned from the surface for repairs and maintenance. It would be far cheaper to supply a permanent human habitation on the Moon. It would provide an ideal opportunity to develop a permanent habitation at L1. It would greatly simplify returning payloads from the Moon to the Earth; first scientific samples and later products of commercial value.

The Next Frontier in Real Estate

Ravens_Nest

Where will we live beyond Earth?

The most common assumption about an interplanetary race is that a majority of the race will live on planetary surfaces. There are actually many disadvantages to living on a planetary surface. The gravity of most planets is far from ideal. The gravity wells of planets require huge amounts of energy to move people and goods up and down them. Most atmospheres are far from ideal. The most convenient source of power is solar energy and half of the time any surface colony will be in darkness. There are a wealth of contaminants such as dust that are either a hazard to human health or to the operation of our machinery.

Orbital habitats avoid most of these issues. We know how to create artificial gravity that will avoid known health problems simply by rotating the habitat; the same solution is impractical on the ground. The energy to get to and from them is much lower than the energy to get between orbit and surface location. In space there is no atmosphere so it makes it equal to the most favorable atmospheric conditions we have encountered off Earth and you do not get the weather problems that come with an atmosphere. Even in LEO a station would have sunlight at least 60% of the time in an equatorial orbit and this can be increased by sitting at the higher end of LEO and using an inclined orbit. Once you are above the inner Van Allen belt the station would have at least 90% sunlight. The orbital environment is considered equal to the best clean room.

There are disadvantages. Any raw materials are a long way away. A colony on a planetary surface will have some raw materials very available to it. The value of the raw materials will be limited and at the start most of the supplies for any colony will need to come from Earth and it will be more expensive to get the supplies to any planetary surface. The cost of transporting resources from locations like the Moon or asteroids will be fairly low and easily offset by other advantages. Radiation could be a more significant issue but even colonies on planetary surfaces will need to deal with this issue.

The Shape of Things to Come

A large part of the design of orbital colonies will strongly influenced by the fact that a zero G environment is not health for humans over the long term. This means artificial gravity is required and the only current feasible way to do this is to spin the colony. Some assume that for humans to be health they must have near full Earth gravity. This is likely far from true, especially for individuals who intend on never returning to Earth but some gravity will likely be needed. The first colony will likely be a “dumbbell” design with 2 modals connected by a narrow passage way. As colonies expand in size a torrid design will eventually become common. Only the primary habitations will require the maximum artificial gravity so eventually the inside of the torus will be filled with spaces for food production, storage, machinery for operating the colony and industries employing the colonist.

What we will not see is a recreation of the terrestrial environment so often seen in suggested designs for orbital colonies. The colony designs from the 1970’s come from the myth that the human mind will break if it is not able to see vast expanses of open space on a regular basis. The fact is that about half of the world’s population lives in areas that do not provide such vast vistas. Most of these design look like they are trying to sell the idea to suburbanites rather than come up with reasonable designs for habitats. Every one of the designs are a massive waste of resources and are very impractical.

The amount of atmosphere needed for these designs will be at best be only 10 times what a more efficient design would be but will more likely be far more than that. This much atmosphere also has the disadvantage of creating weather that could damage the station in much the same way as weather damages structures on Earth. As only a fraction of the volume is used there is far more surface area for a given population requiring more shielding from impacts and radiation. Most of these designs assume that as much as half of the outer surface of the colony will be transparent. That means that section has no function but to collect sunlight wasting more space. The transparent surfaces will also need to be able to sustain impacts from micro meteors without shattering and provide the same amount of radiation shielding as the rest of the outer surface. In the end the designs reflect 2 dimensional thinking in a 3 dimensional environment.

I am not saying that there will not be any open spaces but those that exist will be similar to parks, a public space designed to look terrestrial. Once a colony exceeds 1,000 people it will likely be practical to create such spaces. However by this time most inhabitants will likely have technology to simulate outdoor environments in their own quarters. Recreating the sights, sound and even smells of any location they wish.

What’s for Dinner

Some things will be shipped to an extraterrestrial colony from Earth but food will not be among them. An extraterrestrial colony will need to produce all its own food. The designs for colonies for the 1970’s imagined that along with living much the way we do on Earth we would farm much the same way too. Using anything like conventional tilled farming methods will be completely impractical for any extraterrestrial colony. At the time of these designs little was known of any other method of growing crops but new techniques have been developed.

A concept known as vertical farming will be key in efficiently growing crops in and orbital colony. Vertical farming on Earth refers to any indoor farming method that uses more than a single story. Some commercial vertical farm projects produce 150 times per acre of floor space as a conventional farm. That would translate into a 10 story building on a 1 acre lot would produce 1,500 acres of conventional farm land. Not all crops could achieve this level of production but vertical farming could far surpass conventional farming for most.

Another big advantage of vertical farms is they use fewer resource than conventional farming. Some vertical farming projects report a 95% reduction in the water used. As most techniques depend on hydroponic the amount of fertilizer used is reduced. As the crops will be in near clean room environments that can have physically isolated from each other almost no fungicide will be needed.

Another point is that natural sunlight in orbit has not been filtered by the Earth’s atmosphere. This means it is 150% as strong as the sunlight at the equator and much higher in the UV spectrum and comes with higher levels of radiation. Solar thermal power generation will likely be able to achieve at least 40% efficiency converting sunlight to electricity. Plants only make use of 10% of the spectrum of sunlight and new LED grow lights that produce only this spectrum are now available. If the LED are only 50% efficient at converting electricity to light the useable light will be double what you would get by shining the sunlight directly on the plants.

What is so Great about Space

Some have the opinion that there is no value in colonizing space. Many believe that there is nothing beyond Earth that will be worth the effort to colonize space. For the most part what I have read is a combination of “it is too dangerous”, “robots do a better job” and “there is nothing of value in space”. I will comment on the first two and go into the third in more depth.

The Danger in Colonization

This opinion usually runs that space is much more dangerous than any environment we have previously colonized. First I would comment that though we have yet to colonize it naval submarines spend month at a time in environments at least as lethal as the surface of Mars. Compared to past colonization the relative danger is very much less . We have a very good understanding of the dangers we are likely to face. We also know the sort of technology we need to develop to overcome those danger and a clear understanding of the supplies we will require.

Past colonization and exploration efforts were much less prepared for the danger they would face than we are for the dangers of space today. A good example of this would be the Plymouth Colony, arguably the most famous colony. Just 7 months after setting sail from England almost half the colonist were dead and half the crew of the Mayflower[1]. Jamestown did far worse, losing 2/3rds of their colonist within 3 years in spite of being resupplied twice[2]. The truth is that colonization was much more dangerous than most realize and colonist of the past were poorly prepared and poorly informed about the environment they were headed to. Colonist in space will be much more aware of their environment and more prepared for the dangers it faces.

Robot vs. Man

This argument boils down to the idea that automation can completely replace human activity. The truth is this is not the case and is not likely to be the case any time in the near future. Automation can replace human presence if the tasks to be accomplished can be narrowly defined and up to this point all human activity in space has been fairly narrowly defined. Up to now all activity in space has been related to gathering or handling information. Little that could be seen as material product has come from space. As long as this remains the case the activities will remain narrowly defined and automation will be enough.

Producing material products on an industrial scale will quickly go outside of any narrowly defined tasks. The most automated factories still employ a fairly large staff to maintain the automated equipment. Even with advances in robotics and remote operation a human on site will be more efficient and managing the variety of tasks that will be required to maintain industrial scale operations in Earth orbit or beyond.

Show Me the Money

One of the first ideas that comes up in commercializing space is mining. It is also one of the reasons many think space will never be worth the effort. The fact is that there is almost nothing that can be mined in space that will be commercially viable to return to Earth. The real value of commercializing space will come in the form of manufacturing. What manufacturing will provide that most ideas of mining cannot are goods that cannot be produce on Earth. The key to this is the environment (or lack of it) in space. What will we manufacture in space? At the moment I do not think anyone knows for sure. Many of the possibilities being suggested will either not work as expected or ways to do it cheaper on Earth will be found. It is very likely the most profitable products from space will be something nobody has dreamed of yet.

A Situation of Gravity

Gravity has an effect on everything we manufacture on Earth. In a microgravity environment changes the way just about everything works. The most obvious changes involve how fluids behave. In microgravity sedimentation and buoyancy do not affect fluids so different components of a fluid mix more evenly and say mixed. This can have an effect on how chemicals react and if the components remain mixed when the fluid solidifies. Convection (i.e. buoyant cooling) does not happen in microgravity having an impact on what happens as materials go from a molten state to solid and could help create materials like metallic glasses[3]. In microgravity forces such as surface tension have a much greater effect on the shape fluids take. It could even be possible to use magnetic fields to shape things making “containerless molds” possible to avoid contamination from the surface of the mold. Microgravity may also be the best environment to produce nano-technology also called Microelectromechanical Systems (MEMS)[4].

Many manufacturing methods work better with gravity. This is not a problem for space manufacturing as we know how to produce artificial gravity. In orbit the gravity can be different in different parts of the manufacturing process to accommodate the manufacturing method being used on a product at the moment.

It’s All About the Atmosphere

In many processes the atmosphere we breathe is a contaminant. In space the “natural” environment is hard vacuum. Any atmosphere that exists will need to be managed as closely as the best clean rooms’ atmosphere on Earth. A vacuum is useful in various manufacturing methods including some types of welding and some new types of 3D printing. Clean room environments are important for manufacturing microelectronics and some manufacturing some biological products. As with gravity if the product requires more than one atmosphere in production it can easily be moved from one atmosphere to another as airlocks are already a required part of any human habitation in space.

There is a Lot of Space in Space

The room for space industry is hard to define. It is unlikely we will actually be running out of places to put facilities for industry in the Earth/Moon system for centuries. The Moon’s surface alone is nearly equal to the “usable” surface area of Earth. Also because the environment in space will not limit the size we can build structures that will dwarf anything on Earth. The generation being born today may see factories built in space that have interior volumes measured in cubic miles.

  1. Wikipedia – Voyage of the Mayflower
  2. Wikipedia – Jamestown
  3. Nature – Microgravity metal processing
  4. Space Island Group – Micro Electro Mechanical Systems – (MEMS)

Fall Fashion for the Extraterrestrial

Space imageWhat humanity has worn when beyond the Earth’s atmosphere so far can still be seen as experimental garments. Only the most recent spacesuits do not need to be custom made for the person who will ware it. This will change only when the number of people traveling to space grows. By the time the first person to leaves the cradle what is worn in space will have evolved. The largest reason for this is what is worn now provides only the absolute minimal functionality.

What Wrong with What I’m Wearing

All spacesuits so far have been variation on what is called a balloon suit. It is easy to see where the name comes from as everyone looks like it was inspired by the Michelin Man. There is a long list of problems with this design. Mobility is very restricted and even light physical activity is exhausting. Related to this is that the suit pressure must be kept very low or mobility is near impossible which creates 2 other problems. First is that very low pressures require the air in the suit being pure oxygen to prevent hypoxia. The problem with this is even at very low pressures pure oxygen is quite flammable. This has yet to have created an issue in use in space but it is possible a spark or a micrometer could ignite the air in the spacesuit severely burning or killing the person waring it. Second because of the danger of fire normal cabin pressure is closer to sea level pressure; this means that using the suit requires hours of pre-breathing before each use to avoid the bends.[1] Another problem is that as the suit is a single large balloon any puncture of the spacesuit is potentially lethal. Finally the current designs usually takes over 2 hours to put on, including safety checks, and requires help from another person to put on all parts of the suit.[1] Also it takes at least 5 minutes to remove even the top layer of the suit. This means it will not be very useful in an emergency. Even what is worn in the main cabin could be more functional than the coveralls that are currently worn.

Hard Option

An alternative to the balloon suit is the hard shell suit. The main benefits is of this type is that it can be a full pressure suit so no lengthy pre-breathing and it can be put on and taken off relatively easy.  The problems with the hard suits are they are heavy, expensive, bulky, much more complex and requires padding to prevent abrasions. By definition the materials that make up a hard suit are not flexible so any point where flex is needed there must be one or more joints or bearings. This adds to the mass of an already heavy suit and the complexity increases the cost. Also in a surface environment dust can get into the joints and bearings reducing their effectiveness. As every point of flex is another seal the possible points of failure on the suit are multiplied. The suit also tends to have a larger volume than a soft suit because the must be padding between the occupant of the suit and any part of the shell. With so many joints any point where the occupants skin could press against the outer shell would be a possible cut, scrape or bruise. So far several designs for hard shell suits have been developed but none have been put into active service.

Compromise

The current EVA suits used and a majority of the development money is going into spacesuits that are hybrids of hard shell and balloon suits. The largest advantage is reducing the suit up time. Future development hopes to eliminate the pre-breathing by accommodating full pressure in the suit. Flexibility remains an issue and for longer stays on the Moon or Mars this will be a critical factor.

Badass Option

If you missed it this was what Elon Musk believes should be the defining characteristic of a spacesuit. Now this may seem weird but it may be that the design that fits his description may end up the best one. The concept is rather than retaining actual atmospheric pressure over the entire body use mechanical compression to provide the equivalent of atmospheric pressure over most of the body. The mechanical counterpressure (MCP) suit or skin suit is not a new idea as the first development started in 1959[2]. The most important benefit of the MCP spacesuit is that it promises greater and easier mobility than any other suit design. Most of the suit would not be air tight allowing the wearers sweat to evaporate normally eliminating the need for the liquid cooling garment required in all other types of spacesuits[3]. Weight of a MCP suit is likely to be around 5 kg making a huge savings in launch costs and most of the suit could fit inside the helmet. With a standard suit any damage to the suit could lead to fatal decompression but damage to a MPC suit would only cause loss of counterpressure at the point of damage and might only result in bruising. It is estimated that a MCP suit would cost $500 thousand as opposed to $4 to $10 million for most other spacesuits.

The biggest drawback originally was that that it took much longer than other spacesuits to get into. This was mainly due to the fact that the counterpressure was supplied by a large number of zippers and straps. It is difficult to maintain even counterpressure over the entire skin without sacrificing mobility. Also current designs only can maintain the minimum pressure resulting in the same issue with the lengthy pre-breathing requirement. All of these drawbacks are largely a matter of development required. Current suit designs using advanced materials are making progress toward making suit up time faster and make the suit pressure higher. More research will be needed before the MCP suit replaces current designs but the advantages will be worth the effort.

Dressing Casual

What to wear inside capsules is likely to change. The surprising thing here is that what is worn inside may look a lot like what is worn outside. Currently the usual garb is either jump suits or polo shirts and slacks or shorts. Other than protecting modesty current clothing serves no function. There a variety of health issue related to microgravity that could be mitigated by a new suit design. The Gravity Loading Countermeasure Skinsuit is designed to mimic the effects of gravity on the human body. This could help prevent loss of bone and muscle loss and elongation of the spine[4]. It is possible that some merging of the MCP and the Gravity Loading suit will happen and in the future EVA might require little more than putting on breathing apparatus.

  1. Donning the Spacesuit – Canadian Space Agency
  2. Wikipedia – Space activity Suit
  3. Wikipedia – Liquid Cooling and Ventilation Garment
  4. Gizmag – King’s College London develops skinsuit

They Promised Atomic Rockets

I would like to clarify that this post does not refer to radioisotope thermoelectric generators (RTG) that have been used in space since the ’60s. These are still used and will be used in future missions. What I am talking about here is a primary propulsion system that uses nuclear fission or fusion to generate thrust.

When Will the First Atomic Rocket Lift Off Earth?

Most likely never. The main reason for this is quite simple; even the smallest propulsion engine will likely qualify as a potential weapon of mass destruction. Even a few kilograms of radioactive material could cause a huge loss of life if it were to burn up on reentry and that would be the best case scenario of an accident involving such a craft. It would be so easy to weaponize such an engine that there would be massive international opposition to its development. Those that think that countries like the U.S.A. and China would not be effected by such opposition how simple huge boycotts could cripple the economies of any country and how universal the opposition would be.

Will We Ever Have Atomic Rockets?

Yes, atomic propulsion in space will be an important part of our expansion into space. The catch here is that the radioactive element used will not likely come from the Earth’s surface and will likely never approach it closer than Geosynchronous orbit. The main reason for this is that even intentional nuclear weapon will not be that much more destructive than more conventional weapons in space. A large mass traveling as a significant speed has the potential energy and destructive power of even our largest nuclear weapons and the radiation produced is not that much greater than is ‘natural’ in the local environment. As the Moon is made up of the same material as the Earth’s crust there will likely be enough heavy metal isotope there to use in the engine. Mining it will also not have the issue of contaminating the local environment that exists on Earth.

Atomic propulsion will be used but it most likely will be uncommon. There will be cheaper and cleaner ways to get from point A to B but there will be situation where the high fuel density and power output provided by an ‘atomic rocket’ will be the right tool for the job.

Solar Energy Satellites

There are a number of proposals provide for the Earth’s energy demands by using solar energy satellites (SES). The most common version is to use satellites in geosynchronous orbits. The satellites would convert the suns energy to electricity and use the electricity to generate a beam. The beam will be transmitted back to the Earth’s surface where it will be converted back to electricity. This is presented as having great benefits over ground based solar power options. Many of those proposing and supporting technology of this type suggest that it could provide power more cheaply than fossil fuels or existing renewable technologies. I believe that this viewpoint is based on several misconceptions. I will introduce the issues below and then try to explain in detail what I mean.

In regards to the cost of SES compared to fossil fuels is a misconception held for many renewable power sources. The fuel for renewable power is “free” so the power generated by it must be cheaper. The misconception here is that fuel costs are actually a small part of the overall cost of power generation. A majority of the cost of power generation is split between initial construction costs and ongoing non-fuel operation and maintenance costs. This is the reason that all renewable energy except hydro are only now approaching or achieving grid parity as the cost of construction per KW delivered has been significantly higher. This would be even more true for a similar installation in Earth’s orbit.

In comparing it to existing renewable technologies it is usually argued that it is more consistent and efficient than ground based options. On the surface this is true but ignores the fact that this is only advantage if it is cheaper than a ground based option that would cover the gaps in generation such as other power generation method or power storage methods. An orbital installation’s construction cost is likely to make it far more expensive than any ground based option including grid scale battery systems.[1]

The Advantages

The advantages that an SES system has over non-renewable options is almost identical to ground based solar power. Ground based solar power solutions are just beginning to be competitive with non-renewable option.[2] As that is the case if an SES system is not able to compete with a ground based solar power system it will definitely not be able to compete with non-renewable options. In addition solar thermal option continue to be significantly more expensive than photovoltaic (PV) options. For that reason from this point forward I will focus on comparing SES to ground based PV.

The two main advantages of a GEO SES is that it gets more hours of sunlight and the power density of the sunlight is greater without the atmosphere filtering it. If the Earth based system uses similar sun tracking technology as would be required to an SES system and the location were chosen moderately well it could achieve and average of 9 hours of full sunlight. This would provide a 2 and 2/3rd advantage to the orbital system over the earth based one. The Earth’s atmosphere absorbs about 35% of the overall but as more of this loss is in the UV and infrared range not used by PV the loss is closer 21% in this comparison. Combined with hours of sunlight this results in an overall advantage of almost 3.38 times the power available.[3]

The Show Stopper

I will start with the single biggest obstacle to the feasibility of a SES system, launch costs. The single most important factor here is weight. I checked several sites to identify what would be the weight of the solar panels to provide 1 KW of capacity. The best numbers I came up with was about 120 lbs./KW. With the number above we could determine that we get the same bang out of only 35.5 lbs. of solar panels. When it is launched this summer the Falcon Heavy will likely be the cheapest way to get to orbit per pound. Details listed on the Space X website give pricing of $772/lbs. to LEO and $1,930/lbs. to GEO.[4] Even if a way is found to transport the panels from LEO to GEO for free this would still mean that it would cost $27,406 just to transport the equivalent of 1 KW of ground based capacity to orbit. The more reasonable cost to take the panels to GEO would be $68,515. Agua Caliente, a fairly recent solar plant project costing $1.8 Billion with a capacity of 290 MW that works out to just $6,000/KW.[5] The worst part of this is that the solar panels are only part of the weight that such an orbital project would require. Some of the things I have not tried to estimate the weight of is the framework that the panels would be mounted on, the motors needed to keep the panels pointed at the sun, the engines needed for station keeping, the construction equipment to build it in orbit or the transmission antenna for beaming the power back to Earth.

Often with show figures like these the reply will be, “the next launch technology will significantly reduce launch costs.” The problem with this is that if launch costs dropped by an order of magnitude and the rest of the project was free it would still not be competitive with existing ground based solar power or almost any other power source. And the bad news just keeps coming. Launch cost are not the only prohibitive costs and in future posts will discuss these and options for orbital beamed power I believe are more likely to work.

Footnotes

  1. Article referencing pricing for grid scale batteries – Big Batteries Don’t Come Cheap
  2. Article from U.S. Energy Information Administration – Capital Cost for Electricity Plants
  3. Post on ‘Do the Math’ blog – Space Based Solar Power
  4. Space X launch costs – Capabilities
  5. Wikipedia – Agua Caliente Solar Project

Building a Future

Earth has been the cradle for life as we know it for at least 3.5 billion years. Humanity as a species has existed for less than 200 thousand years. Civilization was born about 12,000 years ago. In all this time we have lived in the cradle we were born into. No human has been more than 260,000 miles from Earth or been away from it for more than a year and a half.  We have thrived on Earth up to this point adapting our environment to support a population far larger than any other species of a comparable size and complexity. This will not continue for much longer. We have tapped almost all of the easily available resources on the planet. This is not to say that there are not a massive amount of resources that are yet to be tapped but it does mean those resources will become increasingly more expensive at a faster rate. I do not believe the end is near but it is beginning to become clear to most everyone that we are starting to outgrow our home.

It is time we commit ourselves to leaving the cradle we were born into or it may someday become our casket. That is not to say I ascribe to the worries about an extinction event. Though it is possible that some unforeseen disaster could blot out all of humanity the reality is that humanity right now would likely the survive the asteroid impact that happened 65 million years ago. What is more sure is that if we chose not to move to space there are only two possibilities I see. Either we continue to expand to the point where the Earth cannot support us or we limit ourselves and eventually smothering ourselves to death. In any case the only insurance of long term survival of humanity is in space.

I am doing this blog out of the passionate belief that humanities future is in space. I believe eventually either this will become evident to most people or the benefits of living in space will draw people to live in space. In a hundred years I believe more than 1 percent of the entire human population will reside off Earth. In two hundred years I believe a majority of humanity will live in space. Eventually Earth itself may become a vague memory of a time when we restricted ourselves to the surface of a single planet.