Friday, December 16, 2016

Ice Mines Don't Sell

Kapitalist asked if Moonwards could also work on a plan that could happen in the world we know in a comment on the previous post. That was like pressing a big red button in the middle of my forehead, so i am responding here.

If we only think about what could be realistically done under existing political realities, we fail to see the real nature of space exploration. Decisions about undertakings of this scope should be made knowing the best and worst possible outcomes within our lifetimes. This is really important, but the matter is almost completely neglected. That's because we haven't had the tools before to really examine it. Now we do, and time is of the essence.

Paul Spudis has a wonderful detailed plan for lunar exploration, in my opinion the best out there by far, very realistic and reasonable. I have to ignore it almost completely. There is a list of reasons. I will look at the main three.

Saturday, December 3, 2016

Colony Expansion

Sketching things rapidly is really helpful for discussion. In the last 3 weeks i've sketched all the main installations of the colony in order to create an overview, and a framework that can be the basis for improvement. There are still a number of undocumented things, nonetheless there is so much more in the colony models i'm having trouble deciding how to explain it. At the same time, the models are such simple sketches, they don't really get across the richness of the ideas unless the viewer fills in a fair bit... Let me see if i can paint this picture for you now with what we have...

Whole Phase 1 colony looking west over the crater rim




















Monday, November 7, 2016

Walking on the Moon

I have spent a lot of time in and around Lalande Crater on the various maps of the Moon. I have my favorite spots. I've developed an inordinate fondness for it as clearly one of the handsomest craters. I have burning questions about what is really there. So, when i decided it was time to make a 3d model of it using LRO imagery and topographical data, it isn't surprising this activity stretched to over a month.

I highly recommend the modelling of craters as a pleasant pass time. If you enjoy maps and scale models, you will find it rewarding. We have a whole Moon covered with craters for which such models do not exist, so you can also enjoy the fact the result is a first and might be useful to someone. Really. There are very few such things in existence, and what there is isn't very detailed. NASA (of course) has the best collection, but the size of the smallest details in their models is still on the order of 100 meters (300 feet). Also, all the listed models at the link have been stretched vertically for dramatic contrast, which makes me shudder. Cosmetic fixes like that aren't necessary if you lovingly detail a smaller feature by using photos for reference, instead of modelling areas a hundred kilometers across using only topographical data.  LRO photos have resolutions as small as 50 cm per pixel (20 inches). With them you can show off the Moon's actual rugged terrain, as it really is. But, it takes time.

Wednesday, October 12, 2016

The Transport Tipping Point

Giant rockets and giant rocket explosions have been all the buzz for the last few weeks. It has gotten me thinking how little conversation there really is about the future being pursued here. There is lots of analysis of the market and the technology, but not of where we are headed. Sure, the viability of colonizing Mars is discussed, and the reasons for pursuing space settlement in general. But there is no sense of how scale affects the whole thing, and changes the whole panorama.

Sunday, October 2, 2016

Nice Even Temperatures Through the Magic of Thermal Mass

An entry came in on the website forum about the extreme temperature swings between day and night on the Moon, and the difficulty of keeping temperatures even because of this. The poster, Sam D, mentioned in another post how lava tubes help with this, and that is indeed one reason why the idea of just sealing one up and using it as a hab is popular. I haven't ever properly explained why the habs we've designed will have very stable temperatures, so, now i am. (There is a different version of this on the forum more tailored to the asker, here i'm rearranging it a bit.)

If you have enough mass within the whole gallery space, then heat regulation is easy. Just make sure that enough heat leaves over the night to balance what came in during the day. That will mostly happen through the rock of the gallery floor and lower walls. If anything, the windows won't be enough for that and very minimal radiators would need to run every now and then at night.

Wednesday, September 21, 2016

The Pyramid Paradigm

Long, long ago, all of the very first nations on the face of the Earth made really big things. They made the very biggest things they could figure out how to. For a long time they raised huge stones over tombs or temples. Then they took to building a wide variety of pyramids. The one we simply know as the Great Pyramid remains the heaviest structure ever built, handily beating the Romanian Palace of the Parliament, which is the heaviest modern building and an interesting point of comparison.

The Romanian Parliament, known in Romania as Casa Poporului (the People's House) was built by the nation's soldiers, in a land at the time ruled by a brutal dictator. It took between 20,000 and 100,000 of them working under forced labor sometimes around the clock for 5 years, and the rest of Romania was deprived of basic needs in order to fund this. It is said that hundreds of workers, maybe as many as 3000, died during construction. The project stopped when the dictator and his wife were overthrown and executed in 1989. I remember the film shown on the news in Canada of the Ceausescus' dead bodies, a clip taken by the Romanian revolutionaries who wished to prove to their countrymen that they were really dead. Despite their hatred of everything the building represents, Romanians eventually decided that it only made sense to use Casa Poporului as the seat of government, the purpose for which it was built. So much was sacrificed to build it, and it is, in the end, well adapted to the task if one looks past its authoritarian feel.

Monday, September 5, 2016

All the Reasons Why

Moonwards is a bit of a different approach to promoting space. It seems time to properly summarize that. I'm on The Space Show next Sunday, Sept. 11th, and i need to organize my thoughts. It hasn't seemed useful (up to now) to contrast it with various other projects out there, so this gap keeps reappearing where people wonder why it isn't done like x or y.

99% of the imagery of space that most people see is in fiction, there is a huge quantity of material. For most people, what we are really doing in space is pretty boring by comparison. Unless they have a background in the sciences that allows them to appreciate it, it just isn't going to hold their attention. However, the growing proportion of popular fiction that takes place in space is a signal of something important. Human cultures are increasingly transferring their broadest vision of our hopes and dreams to a space setting. If you want to reach people, and get them thinking about what the road to our greatest dreams needs to be, tapping that has huge potential.

So Moonwards is building a bridge between the vast energy placed in fictional visions and something that could actually be done. It seeks a keen balance between realism and fantasy that powerfully makes key points about who we are and what we should pursue. A city on the Moon can capture the imagination. Yes, you could fly by flapping wings, needing only your own strength. Yes, you could leap from the water like a dolphin. You could carry 10 people on your shoulders, jump to the roof of a house. You could run for miles and miles without exhaustion - you could just run wherever you go without it being a big deal. You could run everyplace with a friend on your shoulders, and switch occasionally between who is carrying who. The scale of what we could build there once we built up infrastructure would also be that much grander. Ladders into space, skyscrapers miles high, pits miles deep.

Thursday, August 25, 2016

Transportation that Builds Momentum

There is no way around it. The different resources of the Moon are in different places, and they don't seem to be close together. Mapping of resources is really patchy, low-resolution, and incomplete, so maybe there is a sweet spot that helps with this we have only to discover. Probably not, though, and even if there is, if you are talking about serious development, you are going to need to go get things from far away sooner or later.

Building first at the equator simplifies some things but runs into this as soon as the water supply comes up. For all that it is much easier to build big quickly at Lalande Crater, it has advantages in trajectories to and from Earth, and has much more iron, potassium, phosphorus, thorium, and rare earth elements than the poles, all of its water has to be delivered. A base at the poles could get its water from permanently shadowed craters once the machinery to do so had been developed and built. That could prove difficult and expensive though - we don't know yet.  If you set up an efficient supply route from Earth, supplying enough water doesn't get problematic until it is time to expand the colony from the initial crew of 30 to a population of hundreds. Even then, if you skipped putting in giant swimming pools it is conceivable you could simply add a few cargo runs  to your schedule loaded with nothing but water from Earth and stay within your budget. However, a place on the Moon where people are supposed to live for the rest of their lives really ought to have giant swimming pools. So, the trick is how to bring kilotons of water to the colony for those residents. And just aside from that you will want to be able to move kilotons onto and off of the Moon anyhow, so this is really just the first, most obvious case of that need.

Wednesday, August 17, 2016

Health Tips on the Moon - Part 3

It is time to speak of radiation on the Moon. First i am going to explain it a bit, and point out things a lot of people don't know. One, we can only make decent guesses how much radiation there is on the Moon. Two, we don't know what it will do to people. Three, a bit of shielding makes it much worse, not better.

One - We have no direct measurements of radiation levels on the Moon's surface, and modeling that environment with software is extraordinarily complex. This paper based on modelling found galactic cosmic radiation (GCR) fluctuates between 0.38 Sv/yr at solar minimum and 0.11 Sv/yr during solar maximum. (The solar wind scatters GCR particles that enter the solar system, and when it is stronger less penetrate to the inner solar system.) The Curiosity rover measured 0.66 Sv/yr in deep space on its way to Mars, 0.23 Sv/yr on the Martian surface in 2013, when solar activity was about half way between its minimum and maximum. The Moon is different than Mars because it has no atmosphere, but taking all those figures, using an average of 0.25 Sv/yr overall is probably within, say, 50% of the truth.

Two - Again using a lot of modeling and statistics, the estimate is that 0.5 Sv/yr increases an astronaut's chances of cancer by about 3% to 5%. In order to not increase those chances beyond that amount, radiation dose for a whole career is not to exceed 1 to 4 Sv, depending largely on the age and gender of the astronaut. There isn't enough data to consider other possible health risks due to radiation exposure, and even the figures used are a guesstimate. Actual effects could be much less or much more, they could vary a lot from person to person, and other factors like diet and exercise could change these probabilities greatly.

Tuesday, August 9, 2016

Health tips on the Moon - Part 2

Before i do anything else i am going to deliberately refer you away from this blog, to the wonderful Lunar Swimming entry on Randall Munroe's What If blog, and please note that i asked that question. Please return for further discussion of the proposition.

All done? Okay, hopefully you noticed the bit that points out 'The inertia of the water is the main source of drag when swimming, and inertia is a property of matter independent of gravity. The top speed of a submerged swimmer would be about the same on the Moon as here—about 2 meters/second'. So, if you can swim, you can load your muscles just as much as they are loaded when you swim on Earth, and swimming is one of the best forms of exercise there is. It develops all your main muscle groups while not straining your joints. The pressure of the water against you could also be useful for encouraging redistribution of fluids, if the low gravity isn't enough to keep the fluids in our body where they ought to be (which it might be, and if it isn't, the water pressure while swimming might not help - speculation here).

Let us come back in a bit to the much more intriguing fact you could leap out of the water like a dolphin, and the splashiness matter, and talk about how else so much water can be useful. And let us also come back to the point that water is heavy and it would take a lot of infrastructure to get the water for large swimming pools to the colony, and more infrastructure still to do the audacious things with them i am about to propose. That is all just a matter of how far along the development path of a colony something like this would make sense. Development timelines change a lot when people decide they want something to happen, thus the relevant thing is to talk about the neatest possibilities.

Monday, August 1, 2016

Health tips on the Moon - Part 1

I've been mulling how to address effective exercise on the Moon to address a host of health problems that come with low gravity.  The main issues are loss of muscle and bone mass, and problems associated with redistribution of fluids, in particular how this can degrade eyesight. Also with the first habitat model coming along, i took a more critical look at its radiation protection and beefed it up.

As with many things, the exercise problem gets a lot easier if you have plenty of space to work with. That is why the first virtual moon colony being made is something pretty developed, to really assess the potential. Two things are being put in for exercise that hopefully could make a big difference. One is a human-powered centrifuge, a variation on the kind used to test human tolerance to high g forces. One the German space agency has is shown below:

You go in the box then it spins real fast

Wednesday, July 27, 2016

Getting in Virtual Shape

This may not shock anybody, but building an entire virtual Moon colony is a really big job with many challenges. Trying to become more methodical and organized about it has led to a lull in visible output right now. It has also made the stack of tasks on my desktop look that much more daunting. For now. I hear that once a project is properly organized, things go much more smoothly. That would be really nice.

The Moonwards.com website was registered a year ago this week. I had been playing with the idea for a few months before that, and was encouraged to actually try it by people i met at the International Space Development Conference in Toronto in May of 2015. My idea of how that would go was really different at the time. Maybe it is typical when someone has an idea they find really exciting that they expect other people to find it equally exciting and hop on board just because one tells them about it. Now i realize that the rich, complex landscape of Moonwards in my head is only visible to me, and although many people find it interesting, they need much better reasons to devote their time to it than my enthusiasm and a small website. Turns out i actually have to figure out how to do this myself, and create the basic framework of it mostly on my own. Then it will draw people in and the actual doing of it will be shared among a group.

Saturday, July 23, 2016

Walking Rovers on the Moon

Moon dust is super nasty. It is composed of particles of shrapnel, essentially, created during meteor strikes. The only bits that aren't all sharp edges are the blobs of glass from the portion that was thrown up as lava. You want to stay away from it as much as possible.

And when exploring a new world, you need to be able to handle all terrain, from steep crater walls of loose material, to fields of boulders, to deep crevices, to ponds of deep fine dust.

Also your vehicle has to do everything. It will have arms so it can do all the manual labor needed to build, manufacture, repair, prospect... whatever comes up, most of which won't be very predictable.

So the rovers for Cernan's Promise will take the ATHLETE rover model one step further. They chuck the wheels altogether and walk around, and some of the legs also can be arms. (I can't help but think that is the eventual idea for ATHLETE too.)

I rather like this video for getting across what i mean :)

The spider-bot that wants to be a rover

My thought is to reduce that concept to 6 legs, put mechanisms on two of them so that the bottom joint folds out of the way and hands are deployed for doing any kind of work.

The Space Show on Conquering the World

(Note: the following is one of various posts that were copied here from the Moonwards.com forum. It was originally posted there on June 6th, 2016.)

Here is a link to Friday's episode of The Space Show, where i talked about how the Moon could conquer Earth, and in general about how military acts in space can be extremely effective and hard to prevent.

It is a dark theme i talk about in order to propose a bright future. I believe that it would be by far the healthiest thing for the world to undertake our first extensive venture in space together, in a manner that is as inclusive as possible. This is the only way we can develop the cooperation and trust needed to keep space safe at the same time we create the possibility for it to become very dangerous. No system of laws, treaties, or regulations are going to be enough on their own. They will only work if we build a sense that we have a common interest world-wide in peace, and that can only happen if we feel we've done it together and we are all on the same team.

The timeline for Cernan's Promise will be based on that approach. I have been focused over the last 8 weeks on building rather complicated models (that i am in fact unsure how to display well on the website, they are that large), preparing for, attending, and doing follow-up emails for the ISDC in Puerto Rico, and getting used to being the new junior moderator on space.stackexchange. I have added some content to the site over the last week and hope to add much more in the next two or three. One of those bits of content is the Residency Program.

It has been outlined in the Mission Timelines already (which are screaming for an update, but hey, one does what one can). Basically, any nation can send an astronaut for life to Cernan's Promise for $100 million, and you need at least 200 such astronauts to provide sufficient income for development. There is an overt effort to get astronauts from as many countries as possible as part of this effort, and there are later rounds done on the same model that add more residency spots at increasingly cheaper prices. Once the settlement has a few thousand residents and the price for further spots has decreased to a level a significant percentage of Earth's population could afford, the market is opened to all.

To get across the urgency of doing whatever the first big thing we do in space is, as a world, together, making people realize that we could pay a grave price indeed down the road if we don't is absolutely necessary. So, i've started going on about it whenever the opportunity arises.

Hybrid Ice Shuttles

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on April 22nd, 2016.)

A nuclear shuttle for transportation of ice from the pole to an equatorial base is limited by the thrust of its engine. That mass must accommodate the mass of the engine and all the other dry mass, and the propellant. What is left in the mass budget then is the payload. Note that fuel required for the return trip must be subtracted as well.

A reasonable delta-v budget for a one-way trip (including some gravity losses) is 3200 m/s.
For all my examples, I am going to use a hypothetical but realistic nuclear engine, at 2500kg, 100kN and an Isp of 950s

Using hydrogen:

We can calculate the required mass ratio:



Also, using a thrust to weight ratio of 2, the launch mass of the shuttle can 30,800 kg. (Scale as desired by adding more engines).
From the mass ratio, we get that 21,800kg of that can be used for the dry mass, payload and return trip fuel.

Using water:

First, why use water? After all, the Isp of water is only 45% of hydrogen. But, even though the mass ratio gets a lot worse, water allows us to get more thrust from the same engine. In a NTR, thrust is simply inversely proportional to the Isp.

So the same configuration with a T/W ratio of 2 allows us to increase the launch mass to 70,800kg. The mass ratio is 2.2, but that still gives us 32200kg for dry mass, etc. Absolutely an improvement.


But we can do better!

The extra thrust we get from the water is only required for the first part of the burn. After the shuttle has depleted some of its propellant, it is light enough that if you then switch to hydrogen, the T/W ratio is still good. (Also note that an high T/W ratio is not that important when you have gained a significant fraction of orbital velocity, making it even more favorable to switch propellant mid-burn.)

If, for instance, we use water for the first km/s of the ascent burn, and for the last 200 m/s of the landing burn, and hydrogen for the remaining 2km/s mid-flight. That results isn 37,300kg for the dry mass etc.

Thrust when needed, efficiency when possible.

My reply:

This is great, Sigvart, you have started my day off quite well for me. And you have taught me an essential new emoticon :[)

That idea i talked to you about the other day, of moving the colony to Aristillus, is one i really didn't want to take on, at least not right now. This issue of transport of material between the pole and the base was what had driven me to consider it. Aristillus is at 33 degrees N latitude, meaning a one way hop would take about 10% less fuel than a trip to Lalande on the equator. As a double sub-orbital hop to get to Lalande and then fly back takes so much fuel, you and Russell had warned me very little space would be left for payload. But water (and carbon chemicals, and ammonia, and the rest) is so darned useful. Even though i think setting up a fuel depot is a low priority, i keep thinking of amazing things to do with water. Lots and lots of water. And those other things.

There are two things i think will make the colony flourish, especially once people are there. If you do it well, broadcasting can bring in 2 or 3 billion dollars a year. And you sell permanent residence in the colony for $100 million a pop. I see residence sales working in the early days mostly because it should be an international sponsorship process. You announce to the world that any nation can send permanent residents of their choosing for that price, and you focus on assembling an initial population that is as representative as possible. Those residents are then representatives of their countries, like Olympic athletes, like astronauts are today. Lots of countries would be attracted to the prestige of that - years and years of national pride and inspiration for one relatively low price, all things considered. And you'd get an almost ideal initial population as well. The best and brightest. The diplomats, the figureheads of a way of life, a way of seeing life and our place in the universe.

Yeah - so, water. For those things above to work, they must come to live in a beautiful place, a place just about anyone would be happy to live. People's impression of how worthwhile it is to live in space, how rewarding the experience could be, will be based on what they see in these broadcasts and the feeling they pick up from those residents. There are so many cool things you can do with water to make the colony more inviting, but you need a lot of it. There is, of course, the classic What If? lunar swimming pool scenario. There are water walls and water domes - 5 m of water is pretty good radiation shielding. There are natural ponds that both provide a sense of nature and do some of the work of recycling waste water.

To do those things on a proper scale requires several thousand tons of water. Some of it will therefore wait for the installation of coil guns at both the equator and the pole. Because really, you can't go too far with this idea. Lakes. A lunar lake, if you are putting in an actual town, you've gotta have one. A dome over a whole crater - good ol' Teacup Crater gets that treatment first. That will take 350,000 tons of water. After that you can stand below that dome and see the sky all around, and sort of feel like you are outside, unencumbered by a space suit, for the first time on another planet.

Oh - Aristillus. It is also a KREEP hotspot. Perhaps it can get the second full colony, but i think we are too far along to move the colony again, and actually, i think there is a decent argument against it. The likelihood of an ilmenite deposit is much higher at Lalande, based on Clemintine data of TiO2 on the surface. Concentration of TiO2 is much higher at Lalande than at Aristillus. ilmenite gets water and iron when reacted with hydrogen. Aristillus also looks a lot older and doesn't have the wonderfully clean walls that Lalande has, that look so very much like the digging depth to get to bedrock isn't much. And the equator has a big advantage if you start doing stuff with tethers, whether you go through EML1 or make a lunavator. So Lalande it is. Which is also nice because i've become quite fond of Lalande after looking at it so much.


Things are shaping up nicely :)

The Sunken Hall (Extensive Edit)

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on April 2nd, 2016.)

New and improved! All the external main stuff looked at. Here are a bunch of images of this key ingredient to the colony concept, an excavated space reinforced with fused basalt material and turned into a nice, bright, quite large habitation space. Man building this took a lot longer than i thought it would. But i think i'm getting faster with these things. I was going to talk about each image but that effort would probably be better applied to the main page of the website, with the whole marker and tooltip setup. Though this model is really getting into the territory where it would be much better to have a 3d model people can rotate and move around in, or you don't see how it all works together or the details. In fact i'm not sure it would be helpful to put up all these images, as there are so many.

At any rate, a couple of highlights. The berms of material around the sides of the area with the arched roof ensure there is no direct view of the sky from the sides, cutting the radiation dose down to something safe, even over decades and even if you spend half your time in that area. The bottom image shows how a view of the sky is visible between the beams of that area, which i call the dugout. You get a significant dose of radiation from that direction due to that, but because you are so well protected from other directions it doesn't endanger you. All the beams have the same gap, so you can walk from end to end of that area, always have a view of the sky above you, and always have natural sunlight falling on you (minus the UV and gamma ray spectrum). The area is very well adapted for growing plants. The idea is gone over more in this post. Also through the windows at the end of both the tunneled sunken hall and the end of the dugout, a mirror has been set up that reflects in a view of the Earth. The Earth moves only a little in the Moon's sky, and does so quite slowly, because of the way the Moon is tidally locked to the Earth. Those mirrors will always keep the Earth in view.

None of the interior has been modeled yet, of course. I just put in the two airlocks and the structure. Doing the interior will be fun. The space is 40 m long, 30 m wide at the top and 15 m wide at the bottom, by 20 m high, in the dugout area. The hall area (the tunneled part) is 78 m long, 27 m wide, and 13 m high. There is all kinds of space to play with, and all kinds of things that are possible in that space that have never been possible before in, uh, space. I have been playing with ideas for exercises that take advantage of the room. On the Moon if you have enough distance, you can jump high enough to load your muscles and bones the way they are loaded on Earth. That might be very helpful to reducing health issues due to low gravity. You can leave large enough areas open to give something of a feel of the outdoors, or at least large enough not to feel positively claustrophobic after a few weeks.


That outside door you see on the airlock is actually 6 m tall by 5.3 m wide. The other airlock, in the dugout, also has a door that is much larger than an ordinary door. Don't let them fool you as to scale, they were just made very large so they can accommodate anything that might need to be brought inside. Use the little green men in the image below for scale.









A couple of notes:

The transparent areas will indeed all be windows. I don't care what they cost, the views are critical to maintaining mental health. And i don't think they will be that expensive, actually. They can be made of laminated sheets of sapphire, which isn't terribly expensive these days. The images show pretty large spans without reinforcement - actually the biggest open spans would be the squares shown with a reinforcing brace halfway vertically and horizontally, making the unsupported area about a meter square. That's about 1.1 tons each would have to bear if a full atmosphere was inside (and to start it would likely be more like two thirds of an atmosphere). Most would have 3 braces, vertically and horizontally, for spans of 50 cm. For the area of windows shown, for each centimeter thick the glazing is, it will mass 3.2 t. I really don't know how to assess how thick it needs to be to bear the pressure of an atmosphere across a span of a meter or 50 cm. If all of it was 2 cm thick, that is 6.4 t. That really seems worth it for how gorgeous it will be. One of the main undertakings in the early days will be broadcasting and film, a gorgeous place really helps with the success of that. Aside from how mentally refreshing that view would be. The windows looking out over Lalande crater would show you a big section of the crater interior. The dugout windows would only show you the Earth in the mirror, but you'd be able to see it throughout the whole dugout space. And besides, it occurred to me later probably most of that outer wall should be mirrored, for a wider view of the sky.

The arched beams over the dugout are held down at each end by those great big long solid beams with the series of holes along them. The holes show where anchors would been bored deep into the regolith, 3 from each hole at different angles. There is a technique for that that comes from putting together two promising techniques. Both are of course untested, but seem promising. Microwave Sintering of Lunar Soil and In-Situ Rock Melting Applied To Lunar Base. You melt through the regolith with a microwave emitter on the end of a long tube, down as deep as you can go, hopefully at least 20 m. The lava produced is forced out by displacement, and a hollow tube through the regolith is the end result. The microwave emitter sits at the bottom of the tube for a while melting a puddle of regolith around it. Any voids left are back-filled with lava. Deep strong anchors under the long beam on either side of the dugout is the end result. The thick basalt fiber cables running along the top of each beam are attached to these anchors. Similar anchors under the floor of the hall are also made and used to anchor the arches above.

The Polar Ice Shuttle

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Mar 19th, 2016.)

by Sigvart Brendberg:

The location of the Cernan's Promise lunar base has several important benefits, however, access to lunar volatiles is unfortunately not one of them. Therefore, there is a need for transporting ice from the poles to the equator. Currently, the most realistic way to do that is a reusable shuttle, performing a suborbital hop. The optimal trajectory, as described by Hop David here, has a Delta-v cost for take-off and landing at 3131 m/s. (from now on set to 3200 m/s for a little margin).

LH2/LOX

The propellant for the shuttle should be derived from the mines ice, as it has to be independent of imported resources (which would make it a net loss). For a pure chemical system, LH2/LOX is what we have. Most modern upper stages has a total-to-dry-mass ratio around 12, so a ratio of 10 for our shuttle should work as a reasonable assumption. For the Isp of a LH2/LOX system, ~455s, the required one-way mass ratio is 2.05 . That means that the shuttle should be able to transport a payload of 28 % of its launch mass. Further optimizations are however possible, most notably the fact that oxygen can be produced locally at Cernan's Promise, so the important part of the shuttle payload is hydrogen. Even the oxygen for the return trip can be refuelled there. Thus, assuming a fuel to oxidizer ratio of 4.5, it is able to deliver 37% of its launch mass in hydrogen, in total supplying the base with 330% of its launch mass in water. (Not a typo!)

Nuclear/LH2

Nuclear rocket engines are ready, in fact, they have been ready for over 40 years! I chose to use the RD-0410 prototype engine for reference: <engine Isp="910s" thrust="35.3kN" mass="2000kg" src="Soviet Union"> I assume technological progression can easily squeeze 50kN out of that prototype. If we want a trust to weight ratio of 1.5 on the shuttle, the total mass should be 20 tons, with a dry mass of approximately 3800 kg. Payload mass: 43%, water: 380%.

Nuclear/LH2/LOX

What the nuclear engine mostly suffers from, that makes it not that much more payload efficient over all, is that its relatively low thrust gives it a poor total-to-dry-mass ratio. Introducing LOX to the exhaust gives an almost three times higher thrust, while reducing the Isp to 650s. That should bring the total to dry mass ratio back to around 10. If it uses the LOX for the whole trip to the base, that gives a payload ratio of 46%, but high thrust is not required for the whole duration of the burn, so shifting to the high gear for about half of it gives 50% ! In the end, 450% water.

My reply:

I really like the thinking of transporting just the hydrogen. I worry a little that oxygen production will be slow enough that it will take a long time to produce enough to combine it with all the hydrogen to produce water.

The paper i've used for very roughly estimating the characteristics of the solar furnace is this one by Constance Senior, written in the 1991. Since here the relevant topic is how long it would take to produce the oxygen to make water out of the delivered hydrogen, i went looking for something else and found a pretty great paper, which will also be part of a new solar furnace post - this one by John Matchett, written in 2006. 71 pages of pyrolysis goodies.



The sample size was very small, under 40 grams. The applicable test is really only the last one, which used regolith simulant. 10% of that vaporized away in a little under an hour. The size of the lens relative to the sample was maybe a bit bigger than the mirror on the solar furnace, but the solar furnace will probably manage a higher energy flux, maintain a better focus, and will be operating in a vacuum where less heat is transported away. So i'm going to call it even and ignore various differences in terms of scale and setup for the sake of coming up with starting-point numbers. And again, a number of differences besides this will be discussed in a solar furnace post.

The tank on the solar furnace holds about 1.5 m3, but it will be hard to fill it completely to the top. I'm going to call it 1.3 m3. It will be loose regolith, which has a bulk density of about 1.3 g/cm3 - might be able to pack in more mass by putting in mostly chunks instead of powder, but we'll go with that. So that's 1.7 t per charge. At the bottom page 15 of the pdf of the Senior paper, she estimates yields of 0.02 to 0.2 g of oxygen per gram of soil. She postulated a very different design, and didn't have the benefit of experimental results from a prototype, instead using extrapolations of results from related experiments. I'm going to pick a figure in the middle of 0.1 g O2 / g of regolith. I'll also say that we evaporate away half of the charge before emptying the tank and refilling it. So that would mean we get 10% of 0.85 t of regolith out as O2, which is 85 kg. If the figure of 10% of the charge vaporizing in an hour held true, that would only take 5 hours. To account for the tasks of processing, maintenance, and put in a healthy margin for error, i'll say 10 hours. At that rate, working around the clock (which will be standard), over one lunar day we could do that 34 times, which is a total of 2890 kg of O2, and i'll round that down to 2.8 tons of O2.


If i take my understanding of your terms (danger!), then 50% payload for nuclear using hydrolox fuel is half of 20 tons, so 10 tons. Some of that is going to be pressure cylinders to hold the hydrogen, probably a few of them, because of the way they need to be processed on either end. Those cylinders need to handle long-term storage in the lunar environment - several days at least. I'm going to say they account for 1 ton of the payload. So that's 9 tons of H2, which needs 72 tons of O2 to convert it all to water. At 2.8 tons per month, it would take 26 months to produce enough oxygen. And also we need to have the oxygen ready to refuel the shuttle, so that's another 3400 kg of O2 (i think).

Sigvart:

Just a little comment on the shuttle calculations.

That "maximum total mass" is just because of the limited thrust of the nuclear engine I used as an example. That number is really just used to find an acceptable number for the total-to-dry mass ratio for the all nuclear system. Of course, the shuttle can be made large (or smaller). What matters are the percentages at the end. The results should be (roughly) scalable.

For the nuclear/LH2/LOX, the thrust limitations can pretty much be ignored.

However, the great differences does not seem to lay in the propulsion system design, as producing the required oxygen at Cernan's Promise is boosting the payload 800% ! (+ a little more for not having to transport the oxygen for the return trip.)

I am really looking forward to see what throughput the solar furnace ends up with, but I suspect that the limiting production rate would be the electrolysis at the poles anyway. (To be determined though).


Another consideration that may have an impact on the design is that event though hydrogen has a much better Isp than water, there may be benefits of using water for the first km/s or so: Despite the lover Isp, it is way denser, so for some substitution, the Delta-v actually increases due to the much better mass ratio (using the same tank space). Secondly, for the same reactor power, water has a higher thrust than hydrogen (inversely proportional to Isp). That extra thrust allows for a larger launch mass, and therefore also a smaller part of that mass being the propulsion system. (Better total-to-dry mass ratio). On top of that, straight water requires less processing to produce, of course.

Me:

Oh - a potential solution: reduction of ilmenite by hydrogen to produce water, iron, and titanium dioxide.

FeTiO3 + H2 > Fe + TiO2 + H2O

http://pubs.acs.org/doi/abs/10.1021/ie00057a005?journalCode=iecred
http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources07.pdf


Gotta go do something else, but i wanted to get that down.

Leap day for celebrating leaps!

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Mar 1st, 2016.)

Well, now that the Space Show interview is done, time to tear apart the Planning page and redo it as something more focused and useful. I'm deciding how to do that now and it will take some Javascript, so it won't be fast, especially as i only know basic JS right now and haven't practiced much. This time i'll do the work on CodePen and upload working versions to GitHub, so that if people have anything to say about it or want to add or change it, they can. Just register here and at GitHub (if you aren't already there).

New people coming in here see a long list of posts by mostly me, and recently a handful by Sigvart. Please don't let that hold you back from saying or asking what is on your mind. I'm learning, the site is young, and there is much to do.

I chose the day i'd be on TSS because it was leap day. For the past few leap days i've thought to myself, this is a day for a very special holiday, one that is more intense because it only happens once every 4 years. I think it should be a day for celebrating leaps - the turning points in human history when something happened that led to great changes. David Livingston mentioned Copernicus yesterday as such a thing. I also think of the steam engine, powered flight, radio, e=mc2, the discovery of the Americas, the invention of photography... It would be a great day for celebrating those special moments when an event enables the human spirit to suddenly expand, and those special moments are brought by great thinkers.

The space advocacy movement is a strong nucleus of people who believe in those leaps, and i think by making Feb 29 a holiday for celebrating them, Leap Day would become a way of reaching out to the general populace and encouraging them to value leaps as well. Because the more we focus on them and value them, the easier it is for them to happen.

The leap we 'space cadets' pine for is a full, proper, committed leap into space. We have lacked a way to really present that to people who don't know a lot about the science and engineering behind that, people who therefore have misgivings about how much would be gained for such a vast investment. What better way than to put on a party that honors the spirit of it?

So, i say we do something next Leap Day to really mark that message, and celebrate it as hard as we can. I vote for a parade. Okay, it is a cold time of year in a lot of places, but that has the advantage that there are no competing festivals. Besides, the end of winter has always lacked a decent holiday to brighten the cold and gray. And St. Patrick's really doesn't do it for me.

Yep, i say we have a parade. Something interactive for extra fun, and subtly educational. Something that gets the blood moving.

So, what city should we pick for the first such parade? San Francisco, home of Google, Tesla, and Silicon Valley?

Friday, July 22, 2016

Let us get a Lunavator thread

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 28th, 2016.)

From Sigvart Brendberg: 

Lunavators is an approaching topic, so I just threw up the basics here if anyone is interested

A major concern in space travel is not distances, but change in velocity, commonly called delta v. A spacecraft is limited by its delta-v budget, governed by the rocket equation that has a nasty exponential nature. For example, a spacecraft taking off or landing on the Moon typically needs to be half propellant, with regular chemical engines. Thus, spacecraft are normally mostly fuel, and less of everything else.

Tethers, when completed, provides an efficient way of cheating the troublesome equation, what if you could just climb down to the Moon? The bottom part of the elevator is anchored to the surface, so the momentum of the spacecraft is simply transferred to that enormous chunk of rock.

The problem: Why does not the Lunavator simply fall down? That is after all our everyday experience. The classical approach to this problem is to use the spin of the planet to counteract gravity. (Try to spin around with a rope). However, that does not work for the Moon, as it spins way to slowly. Instead, the elevator extends to a point between the Earth and the Moon called EML1, a place where Earth's and the Moon's gravity cancels out, and together with the inertia creates a place where a thing would remain fixed relative to both the Moon and Earth. A nice place for a space station. From there, a counterweight can be lowered down into the gravity well of Earth. The lower end is also of interest because it moves slower than orbital velocity, making it possible to just "jump off" and re-enter the atmosphere. In other words, a free return from the Moon. Of course, it also works in reverse, making it possible to climb from a transfer orbit to the surface of the Moon. The total one-way delta-v saved is about 2500 m/s.

The math is not that horrifying:

The cable is stretched, so the cable strength we look for is ultimate tensile strength. Also, the density of it is important, the lighter the better. The combined metric for how good a material is as a tether, strength divided by density, gets the unit m^2/s^2, sometimes called Yuri.

This is the same unit that we use for the requirements for the tether, acceleration over a distance. Simply put, you take the acceleration profile over the whole tether span, and finds the area under the graph by integration. This is also a quantity in m^2/s^2.

This can be put into the tether equation, R = e^(requirement in Yuris / tether strength in Yuris). R is here the ratio of the cross sections at the start and at the end of the tether. If this ratio is very large, the material is too weak.

One promising material is Zylon. At a tensile strength of 5800 MPa and a density of only 1560 kg/m^3, it ends up at 3.7 mega-Yuri. That is good compared to the potential between EML1 and the lunar surface, 2.7 mega-Yuri. The end result is a taper ratio of 2.1, perfectly acceptable.

My reply:

That anchored lunar elevator concept is especially exciting, as it would basically be a highway into space. However it would weigh so much that a lot of infrastructure would need to exist in order to build it. Maybe it should be the thing in the Phase 3 Mission 1 section, instead of taking over the world. I was reading a bit about this the other day and it was mentioned that because the Moon's orbit isn't exactly circular, and other variants such as the tug of the sun, Jupiter, and Venus, and irregularities in the gravitational field of the Moon, the EML1 point moved around a fair bit. I went and found where - it was this Orbiter forum thread (where Hop David shows up, surprise, surprise). So the station will require significant orbital maintenance and will need to move continuously to stay in the right relationship to all the elements. But it still is a much easier project than an equivalent elevator from the surface of the Earth. 
The rotating 'skyhook' version, credited to Hans Moravic, allows for a system with much smaller mass that does something similar on a much smaller scale. It can be in a low orbit around the Moon and by rotating the whole structure as it orbits, one end can touch the lunar surface with no relative velocity. 
 
The clever additions by Robert Hoyt to this design allows for a tether 200 km long with a counterweight on one end and a travelling station or hub that moves up and down the tether to transfer momentum from the Moon to the Lunavator. (That's what he called his specific design, though i agree it's so catchy we should just use it for all lunar tether systems.) 
Not that i have yet read his paper properly, but i can't find what material he was using in his calculations. I imagine it was Zylon. At any rate, the tether mass in his design is listed as only 4706 kg. (I like it that he didn't round that to 4700 kg.) It is so light that just one Falcon Heavy could launch not only the tether but also the rest of the system, considering that there is no need to land on the Moon. So maybe the first Lunavator should indeed be done that way. Still - there is soooo much basalt to be had on the Moon, and it may be up to the job, if not as good as Zylon. Sure, it is twice as dense. But getting it where you want it takes about a fifth of the delta v. 
There are few sources on basalt tensile strength and what they say is highly variable. The particular source of basalt makes a big difference, from what i've read. This page by Dr Alexander Novyskyi seems to give a fair treatment of the subject. There is a chart on that page shown below that makes clear how much the particular basalt used and the process technology affect final strength. 
That product 2nd from bottom has a pretty good tensile strength, the two above it aren't too shabby either. And note this quote from the accompanying article: 
'An important step in obtaining quality is melt degassing process which involves the removal of gas held in the melt. This process takes place upon exposure of the melt at temperatures above 1720 K. The duration of exposure is about two hours.' 
Degassing you say? Well, the Moon will have no problem with that at all. In fact, this brings up again the speculation that lunar glasses may be significantly stronger than Earth glasses in general because they are completely anhydrous. This article by James Blacic rather gushes about that. (There is a lot of other fascinating stuff in that booklet too.) 
Which development route to take... much to ponder...
Sigvart: 

The whole rotating tether set-up have momentum, and we pick up something that stands still on the surface. Afterwards, the combined mass of the two must have orbital velocity, in order to not crash into the ground. We want the resulting orbit to be circular. We can manage to do that by either drop mass when picking up the payload, or initially having an elliptic orbit. Of course, we can chose to only lift payloads that are much smaller than the tether mass to approximate the orbit as a circle. The core principle does however remain, we balance cargo up and down from the surface.

If the tether orbits at an altitude of 100 km, the end of the tether has to rotate at 1720 m/s in order to be able to catch the payload. Let us see what the acceleration is then:

(1720 m/s * 1720 m/s)/100000 m = 29.6 m/s^2

That is over 3 g. Ouch.
And when we pick up the payload, we have lunar gravity too. (In total 31.2 m/s^2)

This is great opportunity to present another fundamental property of tethers:

Tether mass is proportional to tether-end acceleration. (for the same payload)

So even if a skyhook is shorter than an anchored tether, it has to be much ticker.


Next: Taper ratio.

The potential (in m^2/s^2, Yuri) caused by the rotation is simply the tether length times half the tether-end acceleration. For the low lunar orbit tether:

29.6 m/s^2 * 1/2 * 100000 m = 1.48 mega-Yuri

Quite substantial. In comparison, the potential caused by the lunar gravity over the 100 km is just 0.155 mega-Yuri.
Although a smaller item, we must consider that too. Taper ratio with Zylon fibre:

R = e^(1.64 MY / 3.7 MY) = 1.56

An improvement over the anchored tether, but the almost 20 times larger acceleration causes a 20 times larger cross section.

A longer tether, for example orbiting at 200 km, has a tether-end acceleration of 15.65 m/s^2 and a taper ratio of 1.58 (very close to the ratio for 100 km).

500 km: acceleration 6.48 m/s^2 and R of 1.65


In conclusion, the mass of the skyhook tether is almost independent of the orbital altitude (unless very high or low), but a higher altitude reduces the acceleration giving more time to make the catch.

Long range plans of all sorts

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 28th, 2016.)

I added lots of stuff to the mission timelines over the last few days, and today tossed in a bouquet of ideas of many sorts. I am on the Space Show on Monday afternoon (2pm PST, 5pm EST, 10pm GST), and wanted to broaden the menu as much as i could in advance. So, i hashed out very, very brief outlines of missions going out far into the future, out into the times when the Moon will be a boomtown with extraordinary scope. The timeline roughly goes to 30 years or so after the first mission lands, accelerating sharply in development speed as it goes. I think this needs to be expected, as by the time the current timeline ends, robotics will be highly advanced. Most labor by then will be executed by independent machines acting almost entirely without supervision or interference, and very little of the mass of those robots will come from Earth. It is only the briefest of outlines of those missions, but it gives a sense of the giddy potential there.

Something to note. I named a few of the installations further out, big things like space stations deserving of a name. Those names come from the family names of people who have contributed to Moonwards so far. This is one little way i can recognize these people, do a little something for them that might actually be seen a lot in the future if things go well. Thus we have Brendberg Station for Sigvart Brendberg, Lynch Spaceport for Brian Lynch, Garcia Lunavator for my husband Aldo Garcia, and Holder Lunavator for me, because hey, we're a pair, and so that the pattern is maybe more clear if people are missing it. As time goes on, i'll give names in the same way to various things in the project. Of course this is only a taste of how in the future credit markers will be on everything. I thought about calling them 'plaques', like how buildings and monuments have plaques talking about their creators.

And now to explain this lunavator thing. Basalt fiber cable is something the colony should have little trouble manufacturing in bulk early on. There is a lack of good documentation regarding the strength of such cable, but the little there is suggests this stuff makes great rope. Wikipedia says its ultimate tensile strength is 4.8 GPa, compared to 5.8 GPa for Zylon, and 3.8 for Kevlar. That's really high. It is a preliminary number and must be treated with caution, but not so much caution that i can't get a little starry-eyed over it. At any rate if basalt rope doesn't cut it for this, further out something else will. Might be harder to make on the Moon though, for a while.

This document, from Robert Hoyt of Tethers Unlimited, looks at a really great version of what you could do on the Moon with an orbiting tether on page 9. The whole document makes delicious reading, an excellent treatment of tether launch systems. I love me a good tether. The paper was done under grant from NIAC, the NASA Institute for Advanced Concepts, so its quality is high. The idea is a tether with a total length of 200 km makes clever use of a counterweight and a station on the tether that travels its length in order to manage angular momentum. This way the tether can be made to meet the surface of the Moon at essentially no relative speed, pick up or drop off a payload, and swing back up into space. And it can do that again and again. Its capacity to move payload is high. It will orbit the Moon once every 90 minutes, so if everything is clicking, it grabs a payload once every 90 minutes. If what it can handle is 1 ton, then it can launch 16 tons every day, day in and day out. Even better, there is an extremely clever way to transfer momentum between the tether and the Moon so that the Lunavator doesn't need to expend propellant to adjust its orbit. It just takes a break every now and then to focus on swinging itself up to the orbital speed it needs.

200 km doesn't seem so very long if you are making basalt rope in really large quantities locally. Sure maybe a Lunavator made of basalt cable would need to be much larger than one made of more ideal materials, but if it can be made of basalt, i like the idea anyhow. Not only would it mean you don't have to spend payload space on an awful lot of cable, it means you can do continuous maintenance on the complex using your own resources. The tether tip velocity to pick up a payload is 0.75 km/s, much better than the 1.68 km/s tether tip velocity needed for a sling launcher to put something in lunar orbit. If a payload is released at that speed, then it has to add on the 0.93 km/s it needs to stay in orbit before it hits the ground. But it has a fair bit of time to do that, meaning big crude rocket engines made on the Moon would be good enough. This gives the Moon a way to ease in to both tether manufacture and rocket manufacture. I even pondered the idea of giant liquid-oxygen-based resistojets as a way for lunar robots to build rocket motors that are good enough to get the job done, albeit inefficient and crude. Otherwise known as simple and reliable. Or maybe more conventional engines from Earth could be made beefy enough, with such a light workload, to work for several hundreds of trips. They could fly back to the Lunavator to be captured, set down on the surface, and reused.

As the Lunavator tether is thickened and reinforced, and experience is gained, it can start hefting payloads at full lunar orbital velocity, or at lunar escape velocity. It can start doing this with small payloads and work up to larger ones. It would allow ion engines alone to be used for stuff that doesn't happen quickly, ones that stay in space and get refueled and serviced there. It is a way to launch lots of mass, which is the only way to do the really interesting things. It is the way the Moon will build its first space station, on a shoe-string budget compared to what it would cost an Earth enterprise to do it. A really nice space station that people would pay lots of money to be able to use.

You see, the Moon is an excellent example of how things change once you reach a tipping point. The Moon goes from being a money pit to a boomtown really quickly once you are able to do the right things - things that are based on known technology and well understood physics. A sense of the possible is all we need.

The Garden Space with Sky Views - Yes we can :)

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 16th, 2016. An updated version of this will be posted soon.)

Okay, finally we have a reasonable design for a sunny space that uses spaced beams that are quite tall to limit radiation exposure to a livable amount even if you are hanging out there up to half the time.

Alright, suppose the little rectangle with the rays emanating from it is you. The beams start 4 m above you for a nice sense of space. In this version, the beams represented by the grey rectangles are 6 m high by 50 cm wide. The complete analysis was done using beams 4 m high by 50 cm wide. In both cases, each beam is separated by 1 m. The orange rays shows a representative set of paths radiation that passes through your body can take.

In the model of Cernan's Promise, the beams will look roughly like this:



See how it works? Straight up, there is very little material blocking radiation, you get a full dose. But because the spaces that have only glass or a transparent membrane are separated by lots of tall beams, starting a short angle away there is enough material that the dose is lowered to a small amount, and when you average the two you are a fair bit better off than if there had only been a membrane. Especially when you get into the details - those beams also protect against all micrometeorites except the ones coming straight down, which is rarely what they do. And unlike if you just dug down and put a membrane, the whole volume is usable. You don't have to stay down low in order to get a low dose.

Here is a map of how the doses work out. It bears a lot of contemplation. Because the energy in cosmic radiation is so incredibly high, it causes atomic nuclei to explode when struck and the bits that fly off have enough energy to cause other nuclei to explode too, and it takes a while before that process causes the original energy to be dispersed enough that you are getting net protection from the material shielding you instead of actually getting a lot more radiation because of the atomic shrapnel flying around.

So the map shows the area of a dome around a person through which the heightened doses due to an insufficient blocking thickness would pass. Those areas are in pink and red. The orange part offers some protection, and the yellow is better protection, good enough for permanent habitation. The green is as low as sea level on Earth. The area this dome examines is an angle of 60 degrees, roughly. Beyond where the mapping ceases, the protection has a fringe of yellow and then quickly turns to green for all the rest.

So imagine if the tall east-west sides of the beams were covered with a mirror surface. If you stand between two and look up you see nothing but stars. The are angled just slightly so that here at the equator the sun tracks around over the long day and the beams are always parallel to its rays of light, the shadows stay minimal. The Earth would be visible much of the time between the beams. When it isn't, it is still coming in from the south end, where there is a mirror pool outside the sunken hall for that very purpose. And the north wall reflect that image from the mirror pool so it is visible from inside the tunnel where people will spend most of their time.

If you'd like a few numbers, here are the basic ones (and please remember the previous post - these numbers are estimates):

Pink - covers 556 triangles, of which a half sphere has 10,240 - radiation between 0.5 and 0.13 Sv/yr. Average taken as 1 Sv/yr, cautiously on the high side. Dose of this area with constant exposure 0.027 Sv/yr
Red - covers 1120 - between 0.2 and 0.5 Sv/yr, average used is 0.4 Sv/yr (The unfilled triangles along the central axis are assumed to be red and counted in this number.) Dose of this area with constant exposure 0.022 Sv/yr
Orange - 2024 tris, average of 0.13 Sv/yr. Dose of this area with constant exposure 0.013 Sv/yr
Yellow - 964 tris, 0.07 Sv/yr. Dose of this area with constant exposure 0.003 Sv/yr
Green - 248 tris, Earth sea level equivalent, taken as 0.01 Sv/yr. If the rest of the half sphere is all green, that is another 0.003 Sv/yr. I padded that to 0.005 Sv/yr.

Which gave a round number of 0.07 Sv/yr total if you were always in that space. Spend half your time there, that's 0.035 Sv/yr. The maximum allowed for nuclear plant workers is 0.05 Sv/yr. So we're good. And we can soak up some sun and see the actual sky, and have healthy growing plants. Ahhhh....


Now let us remember what we don't know. Humans have never spent extended periods of time exposed to galactic cosmic rays. Never. The Apollo astronauts got the biggest doses in history but weren't exposed for more than 9 or 10 days each. These rays are actually particles, and they really aren't like radiation as we know it. In fact their name is a hold-over from when we thought they were radiation because they seemed like it, but actually they are protons, neutrons, and sometimes entire atomic nuclei stripped of their electrons, whipping through space at incredibly high speeds, coming from god knows where but it isn't from around here. Probably from supernovas. Our bodies repair damage from radiation if it is a small enough amount and happens slowly enough. It would in all probability react exactly the same way to cosmic rays. So we just have to keep our exposure down to levels our body can repair as part of its normal daily routine of cleaning, patching, and sprucing up. But we need to know much more before our first buff astronauts bathe in the sun in their hammocks among the tomato plants.

Radiation and windows - a cosmic ray blind design

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 13th, 2016.)

First, i want to emphasize that how much radiation one would actually get on the surface of the Moon is UNKNOWN. I've scrounged for figures repeatedly on this, and went with numbers for initial designs that numbers from new sources make sound silly, which is why an initial dome design had such thin walls. Then i noticed the reference i'd happily started using seemed to have slipped a decimal over one spot to the left in the chart backing up all their statements, repeated in this video. You can tell because the starting figure for radiation on the open surface definitely shouldn't be 0.02 Sv per year. It should be 0.2 Sv/yr. That came out when i found the other reference the video mentions.

Finally today i found a paper that puts it in perspective. An exceedingly relevant snippet from the abstract of Radiation exposure in the moon environment by Reitz, Berger, and Matthiae:

On Earth, the contribution to the annual terrestrial dose of natural ionizing radiation of 2.4 mSv by cosmic radiation is about 1/6, whereas the annual exposure caused by GCR on the lunar surface is roughly 380 mSv (solar minimum) and 110 mSv (solar maximum). The analysis of worst case scenarios has indicated that SPE may lead to an exposure of about 1 Sv. The only efficient measure to reduce radiation exposure is the provision of radiation shelters.
    Very recently some data were added by the Radiation Dose Monitoring (RADOM) instrument operated during the Indian Chandrayaan Mission and the Cosmic Ray Telescope (CRaTER) instrument of the NASA LRO (Lunar Reconnaisance Orbiter) mission. These measurements need to be complemented by surface measurements.*
Models and simulations that exist describe the approximate radiation exposure in space and on the lunar surface. The knowledge on the radiation exposure at the lunar surface is exclusively based on calculations applying radiation transport codes in combination with environmental models.

*That bit translates in my mind to "the results don't correlate and/or don't make sense, so we don't believe them".

The radiation figures cited should be considered in the light of these calculations being astonishingly complex, mainframe computers needed, and the models haven't really been checked against reality, so there is no saying how accurate they are.

For one last bit of pause, consider how this article by Eugene Parker sees it:


This estimate is from 2006, but its high end figure is a third of the high end in the Reitz, Berger, and Matthiae paper. It's a total non-linear, non-intuitive mess.

Nevertheless, the design approach now being used does well in any of these scenarios. The part of it i'm working on now even provides a way to have a glazed roof over large portions of a sunken hall, provided you have a recessed area for when there are solar flares, and you get the proportions of the beams right. The proportions it has right now uses the average of 0.25 Sv/yr from the paper quoted above, which matches the charts from the other reference works, as long as you shift the decimal in the spots where it has drifted.

I am posting this early, the analysis of the radiation that penetrated it isn't done, but this helped me think it through. The illustration should be ready in a few hours.

Heat Islands

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 11th, 2016.)

I suffer from a severe rabbit-in-headlights reaction when i open the Lunar Sourcebook. Yes, i know it is a venerable tome that contains about everything i need. But it is also extremely detailed and dense and designed for people who are trained in the field. David Kring's Powerpoint summary of its information on the nature of the regolith is much more my speed. I was musing over it again this morning. It tells a tale of regolith density at depths over a meter that (once again) is not the idea i had. There are so many things to know, you see, and though i've scanned a lot of material, some things take a lot longer to register clearly than others.

So, alright, as we can see on slide 22 of that presentation, below the first foot of regolith, relative density rises to over 90 percent. And on slide 27 we see that there it conducts heat as well as porcelain does. So forget what i said about it being a good insulator. It will suck up heat like crazy. However, we are still okay, in fact this could be regarded as a good thing - as long as you think more long term. Let us talk about heat islands.

Heat diffuses outwards in all directions based purely on the statistical likelihood of a particle with more kinetic energy striking one with less and thus transferring some of its energy in the collision. We experience that kinetic energy of molecules as heat (well, unless a very large number of them are moving in the same way at the same time). When you pour heat energy into a medium, the heat moves away more slowly the closer the temperature of the surrounding material is to the temperature at the heat source. So the longer heat is poured into the ground around the sunken hall we are building, the slower it will move away. At night the heat closest to the hall is just as likely to move towards it as away from it. When dawn arrives, heat starts pouring in again, and at first it will sink in to the ground faster than it did at sunset, because the ground is cooler than it was then.

The regolith deeper than 80 cm remains at a pretty constant temperature all day and all night. That temperature is about -20 degrees Celsius (-4 Farenheit). Once you expose that layer to the heat of the sun, it will start warming up for the first time in maybe a billion years. Then at night you want to limit heat loss with reflective insulation so that heat builds up. Thus we seek a recipe in which enough sunlight pours in during the day, into the right geometry of material, to create a heat island where the temperature stays reasonably close to something pleasant all the time. And we'd like to reach that temperature within a few years, so that people can arrive to a temperate clime. To get that done we are talking about dumping in a lot of heat, but it should be possible to achieve a desirable balance in a few years with a good design and possibly a few tweaks.

On Earth this approach to temperature control has probably best been explored as Passive Annual Heat Storage. The rule of thumb in that method is that if you thermally isolate a volume of dry soil extending 6 m from an underground home and heat it to the desired temperature, the temperature in the home will stay within a degree or two of that year-round using only the passive heat of the sun, through south-facing windows in a normal-looking house, other than that the rest of it is buried under a thick layer of soil. Beyond that 6 m point the temperature slowly falls to the annual average, which on Earth in mid-latitudes is 5 or 6 Celsius. If you look at the 'Look Inside' preview of the book at the Amazon link above, there is a case study where such a home's earthen thermal store reached a good temperature within 2 years, and was close after only a year.

On the Moon the temperature gradient we have to deal with is much steeper, -20 to 20 Celsius, 40 degrees instead of 15 or so. But the conditions for doing that are very favorable. Sun that averaged over time is twice as strong as what most places on Earth receive, the ability to control heat loss quite precisely and completely with just a few sheets of reflective foil.

My guess - and i say this with 68 arbitrary units more confidence than i've said other things - is that even the smallish sunken hall planned in Phase 1 can have a pleasant area of windows (or, you know, window-like objects) and be kept at a pleasant, even temperature using only reflective shutters. A set of them hooked up to a simple program that opens and closes them on some schedule would be enough, and at least a couple could always be open for that key view of the full Earth bounced into the hall from a mirror.

Moving day

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 10th, 2016.)

After much contemplation, Cernan's Promise will be moved today to a spot half a kilometer north of its current location. Several changes in approach go with this move. Turns out planning an entire Moon colony, even just for education and inspiration, has a steep learning curve full of false starts, half-baked ideas, and a wide variety of mistakes. As hikers learn over time where best to pitch a tent, my feel for how best to make use of what the Moon offers is slowly growing.



I have now modeled this section of the rim of Lalande Crater much better, and made much better use of LRO photos to do so. I have done my best to make the boulders and outcrops shown in the photo accurate, and properly assess their scale. This is made more difficult by the fact that there exist only 2 photos of this area from LRO. In fact, to roughly estimate the downward slope heading away from the crater, i made some use of the photo taken by Apollo 16. As near as i can tell, the boulders in the foreground above are about 20 m high at their tallest, and the mound behind about 15 m at its tallest. Those 2 areas, and the large number of other boulders nearby, are the justification for the move.

There are several reasons.


  • How to store heat and energy through the night has been my main focus recently. Many recent posts discuss the matter. In my view, you want the right balance of two things.
    • Enough powder and fine-grain regolith to prevent heat from diffusing quickly, because even packed tightly such material is about half voids and it conducts heat so slowly it is decent insulation.
    • Enough dense rock to store heat in vast quantities so that power use for heating at night and cooling during the day is minimal. If you have enough such rock, you need no heating or cooling at all. Just let in the right amount of sunlight during the day.
    • There were boulders to be had near Teacup Crater, but this area has a true bounty. Teacup's boulder resources didn't seem adequate once i thought about it a lot. A big factor here is that the more i think about it, the more i suspect that the fine regolith layer at the rim of Lalande is very deep. Though it is mixed with a lot of boulders, it would be a mistake to assume there are enough in a particular area without evidence. Digging down to the mega-regolith layer to access superior thermal mass resources will be difficult, unless it is done through the inside wall of Lalande Crater. Though it is only a guess, i think there is sufficient evidence to postulate that the fine-grain regolith layer could be 100 m deep.
  • The inside wall of Lalande Crater is paydirt. We want to get down in there and start digging as fast as we can. I'd already identified that collection of large boulders i have started calling Gibraltar as the place to anchor ourselves so that is easier and safer. Now i think it is important to capitalize on them that way even more than i thought before, and even sooner. The slope inside the rim here is about 40 degrees on average, and steeper in spots. Lunar regolith compacts extremely well and flows extremely poorly, but you really, really don't want your rovers to get stuck, or heaven forbid, be struck by a boulder that has started rolling downhill. Gibraltar will live up to its name by having a winch with a long strong cable bolted to it, and anchor points for further cables. Advancing deep into Lalande will require the loose rocks be cleared, a winch will come in very handy.
    • Some of those loose rocks are paydirt on their own, because chances are they are composed of purer minerals than powder regolith.
    • About 300 m below the rim and 500 m east there is a ridge that looks very much like an outcropping of a strata of solid rock. Most likely, that is highland material extending from the hills 2 km or so to the west of the rim.
  • The adequacy of regolith as radiations shielding is much worse than i thought. The 1.2 m of packed regolith i'd envisioned in the early dome idea would only have made human residents sick. Cosmic radiation is so powerful that atomic nuclei are smashed when hit with such a particle, creating a cascade effect that takes over 5 m of loose regolith to block. That's not blocking all the radiation, just the extra radiation due to the particle cascade. To then protect against the dose that you'd get on the open surface, you need another 2.5 m of regolith. This issue was what made me decide to dig out the habitat, however difficult that is, because the lenses really help with that and it is by far the safest thing. The deeper you can dig the better, because the smaller the portion of sky you see, the less radiation you get. The closer to the rim of Lalande you can dig, the better, because then you can tunnel to it - an excellent place to expand the colony.


Far out proposal

(Note: the following is one of various posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. It was originally posted there on Feb 9th, 2016.)

From Sigvart Brendberg:

Two layers of reflective aluminium foil around the 18x18x18 meter Thermal Energy STorage cube (TESTcube?) is 3900 m².

What if this foil was used for something else?

Say you have all of it in one sheet at approximately the EML1 point. (not exactly as we must compensate for radiation pressure).

That is a 4.9 MW flash light!

It would of course be tilted 45 degrees at dusk and dawn, so that reduce the power to 3.5 MW, and also, pointing the beam directly at the base is a challenge. Was 300W/m² what the plants needed? Well, then it is enough for a 12000 m² garden.

I know Moonwards is not intended to be a sci-fi setting, and the main focus is keeping things as realistic as possible, but I just had to say it.

My reply: 

Hey, if it works technically, it deserves to be examined and depicted on the site. I have heard a bit about such ideas, but never looked for articles about it because i had the idea it would be for farther in the future. Of course i hope that Moonwards will grow into a 3d world depicting a variety of lunar bases at various points in the future. It's just that i began with a point and a set of installations that seemed like they should be done first, based on my limited knowledge. 
I was concerned about the aiming, like you mention. I also wondered about how flat the reflectors would need to be to get the majority of the light to fall neatly on the base. If those can be managed, then absolutely it should be modeled and included. Here you have a big advantage over me until i set aside modelling, writing, and coding the website to learn a lot more math and physics. If you can establish what the parameters should be and sketch out a design, i'll make the model. Or help you make the model if you wish, or something like that. 
There has to be a few papers out there on this concept. I can't think of how one might search for them. Maybe ask in the Pod Bay, TildalWave might have an idea. A couple of simple searches on NTRS didn't yield anything. A search for 'reflector earth moon' (couldn't think of better) yielded Russians to Test Space Mirror as Giant Night Light for Earth, from the New York Times, 1993. Surprisingly close for such a simple search, actually. 
There are of course other reasons to create an installation at the EML1 point, so such a system there could be refined and expanded over time. Again, the challenge is to get things going, but if Moonwards catches on and we have the resources, modelling such a station would be a good project. My sense right now is that once Cernan's Promise is basically set up - it will constantly be expanded, but once all its principal installations have a decent model - then it is time to model a polar base, and an EML1 station. 
Also, in my mission to goad people into taking space more seriously, i of course did the half-baked calculation in this post, in which i mused how much area of mirror would be needed on the Moon to cause chaos on Earth. Perhaps you would like to play with that idea for your EML1 installation too. After all, if we propose mirrors in space big enough to light lunar crops overnight to feed the lunar populace, what might those do if they were turned towards the Earth and focused on a much tighter area? :]]]

Lighting a Garden

(Note: the following is a set if posts that were copied here from the Moonwards.com forum for the sake of preserving the early days of the project. They were originally posted there between Feb 5th and March 10th, 2016. Some posts in the thread that were unrelated have been omitted.)

So i was looking into the power needs to light a garden through the night enough to keep the plants healthy. And i went to the NASA Technical Reports Server looking for papers on the topic. And sure enough, there were a number, going back decades. But they used odd specialized units for power - PAR, Photosynthetically Active Radiation, was measured in ╬╝mol/m2*s, being the number of photons received by each meter each second. They didn't actually say how many watts the lights were drawing. But after a while i found a paper that stated that. That paper was using BloomBoss UFO LED Growlights.


At which point i did a facepalm. Of course. What was i thinking, not going to the small marijuana grow-op scene for detailed and accurate information on how to grow plants in artificial light. And a wide range of products designed for exactly that. That NASA researcher was a practical guy.


Yes, he actually has dreadlocks.

Anyhow, the light unit above is conveniently designed to illuminate 9 square feet for 90 W, so that's 10 W per ft2, for easy scaling calculations for your... indoor garden. At 11 ft2 per m2, that's 11000 ft2 for the 1000 m2 garden i'd proposed, and thus 110 kW to illuminate the garden - if it was all illuminated at the same time. If it is divided into 2 halves and each is illuminated 12 hours a day, that is 55 kW, or 36 kW if divided in thirds and illuminated for 8 hours. What a deal!

The paper referenced illuminated its plants 18 hours a day for some reason. Given that half the time the garden will be illuminated by good old sunlight, i bet 8 hours is fine. Now, to get these results, the lights were no more than 24 inches from the leaves (60 cm). To have an interesting garden with plants of many different heights, including bushes and trees, it would probably be best to put the lights on strings and carefully weave them among the plants. The distribution of the different LEDs would need to be precise to get the best results. The format is 8 red LEDS plus a blue LED. Overall the effect is of pink light - quite relaxing. A reflective tent of
reinforced mylar will need to be extended over the whole garden when night falls to keep the light where it can do its work.

So, a garden is going to be rather easier than i'd feared. You do need the nuclear power plant to make it possible in the early days, but we already knew that makes a ton of sense. Once you bring a couple of payloads of water from the poles, and have the first sunken hall completely pressurized and balanced at a comfortable temperature, you can start right in on it. Once growing nicely, this garden would greatly reduce the payload mass of food needed from Earth (pro tip - eat bugs!) and be a great boon to the hall's ambiance.

Reply from Robert Walker:
Right, I got a similar figure for my article about astronauts getting all their oxygen from growing food. 20 watts to illuminate 0.2 square meters for a modern high efficiency LED grow light. It's the LEDs that reduce the power requirements so much compared with earlier experiments. 
At the same time - if they grow all their own food, then they also automatically must produce all their own oxygen too. Because we turn nearly all the oxygen in the food into the CO2 that we exhale. Feces are just a tiny part of the total mass there, especially once you remove the water from them, most of the mass of our food is either exhaled as CO2 or its water, far easier to recycle. 
So to complete the cycle, if we grow plants and they take up the CO2 that we exhale, they must also automatically produce enough oxygen for us to breath in to turn the food back into CO2 again next time we harvest it. 
Only 50% of the plant mass is used as food, but that doesn't matter. Even with burning up all the plant wastes, the excess oxygen after taking account of that still must exactly balance the amount of oxygenthe astronauts need to breath to eat the food. 
Also the amount of growing area needed is far less than most would realize. If you use hydroponics and rapidly growing crops, then you can grow nearly all the food from a tiny area. 
With the BIOS-3 experiments, it was 13 square meters per person, for 78% of their dry food requirements and nearly all their oxygen. 
See my article here for more details and links to some of the research:  Could Astronauts Get All Their Oxygen From Algae Or Plants? And Their Food Also?
Alright, now i've read the article properly, and i have a few thoughts. There is a lot of useful information and i imagine i'll need to review the article once a garden space is being designed. And a few of the linked articles.


  • To me, even the first sunken hall and it's garden space (which i've started calling a dugout) have to look great, like a place a person would definitely want to be. First, this is to draw people to spend time in the Virtual Colony once complete, but also i think this would be well worth any extra money spent in a real colony. So i'd put the algae in an aquarium type of construction, a tall narrow aquarium in which the swirling spirulina are seen in mottled shades of fresh green, as a pump swirls them around and sun filters through the tank. Water should be pretty cheap for the colony as long as there is no problem with the shuttles or the polar water mine. Using extra for something like this isn't too extravagant. And i often think about what it would be like to be in the dugout. I think such a tank would be quite pretty.
  • I make fermented drinks from organic fruit juice and sugar here at home. It has proven to be an important element of my diet, as i have health issues that can become much worse if i don't eat properly. And after all, before soda was made commercially, people made drinks like this all the time. It's very simple. My drinks are often just as fizzy as pop, and it's all CO2. I don't let them ferment long enough to have a significant alcohol content, but they are still quite fizzy. Of course, residents might well like the idea of home-brewing beer. Maybe that wouldn't make much difference to the oxygen - CO2 budget, but it is another possible pathway. Anything sweet can be used for this, including some plant waste.
  • Having eaten spirulina, i can tell you its flavor is okay, but i wouldn't want to eat it in large quantities. And it is not the kind of flavor you can easily combine with other things, or disguise. If a good portion of it could be used for other things besides eating, that would be preferable. It would be more tolerable in a diet together with the other plants you listed, like dwarf wheat, mixed greens, and potatoes.
  • Surely it would be easy to add a few insects to this system early on too. I have had grasshoppers, they aren't bad. Meal worms apparently have a nice nutty flavor, and you can avoid the ick factor by drying them and grinding them into a flour. I wonder how they would affect the oxygen / carbon dioxide budget.
  • The dugout is big, 30 x 60 m at the top, narrowing to 10 x 60 m at the bottom. I strongly feel building big is very important to success, and that the robotic technique based so much on melting basalt with sunlight makes that entirely feasible. So there is lots of space for a variety of plants. I quite agree the thing is to use some system to grow plants in a number of layers to best use space. I would really like to come up with a design that is effective and also attractive, which conveyor belts don't bring to mind at all. Maybe some system of trays rotating around an axis. There should be enough room to spare for this to work, and it would be much more attractive, i think.


That's all i can think of for now. Thanks for giving me a lot of ideas and a sound basis to start from. If you have input as to how to design the gardens, please hold forth!