I think this is a good discussion of the EM drive.
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. Jamestown did far worse, losing 2/3rds of their colonist within 3 years in spite of being resupplied twice. 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. 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).
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.
What 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. 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. 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.
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.
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.
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. 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. 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.
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. 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.
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.
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.
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. 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.
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. 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. 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.
- Article referencing pricing for grid scale batteries – Big Batteries Don’t Come Cheap
- Article from U.S. Energy Information Administration – Capital Cost for Electricity Plants
- Post on ‘Do the Math’ blog – Space Based Solar Power
- Space X launch costs – Capabilities
- Wikipedia – Agua Caliente Solar Project