Thursday, June 1, 2017

Cuba 2017

It was my recent pleasure to travel to Cuba with my fiance, C. We spent eight days on the ground and it was intense. My primary interest, besides long standing curiosity, was to see how an isolated (geographically and politically) island economy functions. This was to help me examine some of the assumptions that I fed into my recent and ongoing work on small-scale industrial bootstrapping and Mars settlement!

C and I had wanted to travel together at some point this year, and we found a free week in common. Plans were made, and at 6am Saturday morning, we set off for the airport. Alaska runs a direct flight to Havana for cheap, so by mid afternoon we had landed with a bump, taxied past some ancient Russian Cubana planes being eaten by moss (their current fleet is more modern!), got through immigration and found ourselves in the humid heat, surrounded by amazing American cars from the 1950s. We realized later that Alaska flies to the old terminal, which is considerably more atmospheric.

Havana has more than a million people but the old town is compact (with buildings dating back to the 1500s) and the traffic is sensible, due to a shortage of vehicles and fuel. We set out on foot, walking along the Malecon, a seaside corniche that runs along the northern shore of the city toward the harbour entrance and old fort. The harbour had quite a number of tiny fishing boats, but I suspect the larger vessels evaporated some time ago. The Malecon fed us into the old center, where we walked a space filling curve between Hemingway's (mostly unchanged) old haunts, eventually finding an old bishop's palace to eat dinner. Later that evening we strolled back to our airbnb and decompressed. 

Internet in Cuba is non-standard. Typically there is one or two parks in a city with a public wifi router. One looks for the sketchiest person in the park, who is selling internet tickets for a small fee. There is a considerable industry in resaling these tickets, which contain a username and password that's good for an hour or so, or less, depending on how congested the network ends up being.

The next morning, I felt surprisingly reticent about going outside, ever again, but eventually hunger drove us forth once more into the teeming maelstrom. I have always found the first few days of any adventure to require a lot of readjustment and some gritting of teeth - and likewise at the end of a trip, a day or two back in familiar surrounds to re acclimate. We ventured forth to a nearby hotel, seeking money exchange. The foyer of this hotel had several bellboys, an entrance to an empty restaurant, a bar/seating area full of smoke, a reception desk, a retrofitted elevator, a small fountain, and as we waited to talk to someone, part of the bar's plaster ceiling detached and sailed gracefully down onto the bar right in front of someone nursing one of the 400 different kinds of excellent Cuban rum that can be had here. The bar keep shrugged, wiped the mess onto the floor, and then topped up everyone's drink. 

We spent most of the Sunday walking around the city, venturing as far as the train station (under restoration) and the Capitolio (same). Just north of the station is an old dockyards which is now a market, in which we got some pina coladas and admired the amazing paintings everywhere. Our luggage was too minimal for souvenirs, so if you ever go to Cuba, buy us a painting! 

I was initially surprised, given Obama's recent visit, that many of the old building facades were still in dire need of repair. In contrast, my experiences in the Beijing Hutong before and after the 2008 Olympic games showed that the most popular thoroughfares were thoroughly facelifted. Later I realised that actually many buildings have partially collapsed behind the facades, and the people living there do what they can with the materials they have to keep out the rain etc etc. Most buildings have at least partially rebuilt or retrofitted subdivisions, stairways, concrete floors, plumbing, electricity. I had no idea of the history at all, and no easy way to find out (no internet or Spanish skills to speak of) though later we found out that Cuba's economy was in dire straights through the 1990s following the collapse of the Soviet Union.

That afternoon with clouds brewing we took a pedal taxi (made of MIG-welded rebar) to the Museum of the Revolution, located in the early 20th century capital building, full of history of the early revolution and subsequent struggles against (mostly not imagined) CIA interference in the period thereafter. Parts of the building still had bullet holes in the walls, and out the back were a few planes and the motor yacht (Granma) on which the revolutionaries traveled to Cuba in the 1950s to start the revolution. It is uncertain exactly how many people were on the boat (designed to sleep 12). Some sources say 62, others say around 80. It's possible that a few people became honorary passengers post-facto, I suppose. That evening we'd heard of a great restaurant in Vedado called Decameron, so being not even half-tired, we set out to walk there (it was good) and back, which only took 3 hours. We could have taken a taxi but it was super interesting just walking and looking. My phone contains a fitness tracker and we later discovered we had averaged more than 4 hours walking a day.

Well if that sounds exhausting, strap in, we were only just getting started. The next morning we packed up and went to a cafe we'd heard about. We turned left at a three legged dog, right at the toothless man, and behind the burned out car found the place. The breakfast was good but overall it was much too clean. We eschewed the line of coco taxis and walked to the ferry terminal. They checked our bag for weapons (one was hijacked in 2003 to go to Miami!) and we motored across the harbour to Casablanca, the much quieter northern shore of the old city. There we attempted to buy train tickets on the >100 year old Hershey electric train, walked around a bit, and clambered all over an obviously disused train carriage, a rusting hulk tucked at the end of the line. After an hour, a brave man disconnected two fat copper wires twisted around bolts emerging from the carriage's side, it thumped to life, and we all clambered on - mostly locals (for whom it acts as a bus, stopping and starting anywhere along its 90km length) and one other set of backpackers, from Lithuania. 

The train was slow (outrun by birds) and rather bumpy, but it had good ventilation (the doors stayed open sometimes) and it was faster than walking. After 2 hours or so we got to the town of Hershey, half way, and briefly surveyed the rusting ruins of the old sugar and chocolate factories, nationalized after the revolution and now mostly defunct. Not long after the train broke down. A few people including me jumped out to have a look around. Behind the train were several ominous looking pools of black sludge - did we have a coolant leak? It turned out to be caramel that had leaked from another train! Ours had broken an air line and our engineer was unable to effect a repair. An hour later another train came and pushed us to a siding, then proceeded down the track for another hour or so, until we got to San Antonio. Currently the train terminates here, 14km short of our destination: Matanzas. The 10 remaining passengers set off on foot, and after an hour we reached the first town, a small hamlet with a rusting bridge, a food distributory, no facilities for foreigners (who are legally compelled to use a separate currency at special shops etc), and mostly uniform looking concrete houses all closely spaced. It was the smallest town we saw on the trip and it was interesting to get a view into how the Cuban experiment functions on such a small scale.

We carpooled with the Lithuanians in an old American car the last 10km into town. The town, Matanzas, began abruptly - no more than 10 feet separated open fields (one valley) from high density concrete houses (the next valley), with narrow sidewalks and many busy one way streets. Matanzas dates to the 1690s, and much of it in the original buildings. We found our airbnb (again, special accommodation only for tourists), a large rental house with copious fish tanks and terrariums, then walked into town to find internet, dinner, and spectacular clouds at sunset. The house had an electric hot water system that runs an element right over the showerhead. I've heard them referred to as Brazilian showerheads and although I'm sure they have good QC and big fuses, I've always preferred to have a cold shower - which after a day like ours was no imposition at all. 

Day 3 (indexing from 0) and we got up early. Our airbnb hosts provided breakfast for an extra $5, consisting of pawpaw, mango, pineapple, eggs, bread, and juice. We were picked up by two guys who drove us 20 minutes north west, over a huge canyon, and down through a *very* faded seaside resort, complete with cabanas, oil derricks, and an empty seaside pool containing chunks of concrete. Down on the beach we geared up and went on two dives - both C and I are certified SCUBA divers. I hadn't dived in the Atlantic before and the coral really stood out. We saw lots of fish, two kinds of lobster, a puffer fish, trumpet fish, a lion fish, a cone shell, and all kinds of other stuff. Resurfacing was a shock after nearly two hours of neutral buoyancy, especially with all the tanks and stuff. By the time we got back to the city, it was lunch time, which we enjoyed in the atmospheric foyer of an old hotel facing the central square. I ordered a Cuban soft drink, which uses EDTA as a sweetener! Next door, a staggeringly good choir practiced what might have been Vierne. 

Thus refreshed, we set out toward the eastern end of the town, looking for the train station, which was mislabeled on the only map we had. After a couple of hours of semi-random walking and strange directions, we found the elevated concrete hall, deciphered the timetable (highly aspirational) and then walked back to town for dinner. We had some difficulty booking further accommodation, as https payment portals on the usual apps didn't seem to function on the CubaNet. Fortunately we were able to arrange the details via text message with a buddy in the states. That evening we discovered that ants had set up shop under my pillow, so we transitioned to a different bedroom!

Day 4 we had to relax and revive before the evening's train trip. For some reason most trains in Cuba run overnight - possibly the rails are better behaved when they are cool. We took a trip up the hill to the caves of Bellamar, the oldest tourist attraction in Cuba. Discovered by chance in the 19th century, the network stretches for 27km. The entrance drops down into a BIG cavern, around 100 steps or so, then a series of narrower passages stretch away. The cave guide had a good sense of humor. At one point there was a fountain of love (for the young people) and a fountain of youth (for the old people, but it was nearly empty because a lot of old people came the previous day). Further down was the fountain of the Americas, through which further passages could be accessed, but not on the public trail. At some point the lights went out for a second and it was super dark. On the way back up, the guide said "there's 139 stairs to get to the top. If you feel your heart beating faster don't worry - it's working!" 

Back on the surface we enjoyed a very cheap lunch (Bellamar caters mostly to locals), walked down the road a bit, found the cave's air vent and some lonely looking chickens, then eventually got on the bus back to town. Just as we got on it poured with rain, but surprisingly little came in the windows. Back in town we walked around a little, found some interesting art studios, packed, then took a taxi to the train station. We were in plenty of time, but not to worry, the train was running 2 hours late. The waiting hall was painted in faded yellow, illuminated by three flickering bulbs and featured surprisingly fast ants. A small TV played a movie, and after it ended, about half the room stood up and left! Around 30 people remained in several rows of plastic chairs. 

At length everyone suddenly went bezerk. The ticket office opened just long enough to sell one ticket (about 15 people including us were in line), so we walked down to the platform with everyone. Foreigners *never* take the train so they were a bit confused what to do with us. Around 11:15pm the train arrived, a huge clanking diesel engine, followed by a carriage full of prisoners (with several fresh ones on the platform to join them), then first class, a baggage car, then second class. We climbed on and found seats, settled in, and C went to sleep while I flicked the odd bug off her. The train rattled along, much more smoothly than the Hershey train, with the odd big bang and shake (possibly suspension bottoming out), and my GPS said we peaked at about 80km/h, with stations every 50-100km. 

After a while some passengers across the aisle decided it would be fun to try to convince me that the fare was $5 and I had to pay them. A nearby off-duty conductor kind of shrugged and I played dumb. The true fare is about 8c. Messing with foreigners is extremely unusual/illegal (vis. the prisoner car at the front of the train) and I interpreted it in a joking light. Later, the flow of bugs intensified and after a stop we found our seats sold to someone else, so moved further down the train. For a while we rode in the vestibule with a gigantic drum of water sloshing around, then found another seat. As we approached our destination (the small town of Colon) the train slowed to a crawl for about 30 minutes, we got up, and waited near the door. Just as we arrived the train lights went out for a few minutes and it was really dark! But nothing unusual happened. By the time we got out it was after 1am, so we hightailed it through town to our booked place (foreigners must stay in casas particulares, marked with a special sign), checked in, dispatched a couple of friendly roaches (a baby two inch one ended up under my shoe), and enjoyed the hot shower. Then sleep! 

Day 5 we slept in a bit, then took the day to enjoy the scenery, starting with the hotel room which was adorned with some unusually erotic art. The town is about 20 blocks on a side, not really set up for tourism, and bustling! Several markets sold all sorts of unusual things, including plumbing parts, blender parts, arts and crafts, car parts, and so on. Several 1920s style buildings on the main street, and a typically abrupt transition from dense single or two story dwellings to farm land. Many people got around by horse drawn cart so we took one! I couldn't understand how much the ride was so held out a fistful of (tourist) coins, which could easily have been a week's salary for a Cuban. But the driver took the right amount and we proceeded on our way. I swung back via the station to gather timetable information and admired its reinforced concrete architecture - very clever ways to get the wind in while keeping the water out. But very quiet. The Cuban trains and rails are some of the oldest in the world and the system is just barely limping along. Trains the world over have fallen victim to reliable cars and trucks and excellent roads, and I would be surprised if Cuba's apparent move to liberalize and open trade doesn't deal the trains the death blow. When I was in my teens, it was possible to take trains from Singapore to China via Malaysia, Thailand, Cambodia, and Vietnam. That route is now very (and probably permanently) broken. 

C and I jumped in a car and were driven to Santa Clara, a town in the center of Cuba, thus continuing our mission to use every mode of transport possible. Along the way we saw a number of giant storms roll through, mostly defunct factories, and the usual rolling hills of the Cuban countryside. The car was initially full of mosquitoes, so that kept us amused. In Santa Clara we found our accommodation, relaxed for two, maybe three milliseconds, then set off into town to find an excellent dinner. To my pleasant surprise, a lot of the info on Cuba is 5-10 years out of date. We had feared eating nothing but rice, beans, and plantain, but we found numerous restaurants with all kinds of stuff on the menu. Service wasn't the same level you get in the USA, where wait staff need tips to not starve, but we found a few smiles went a long way, especially once we got off the beaten track. Matanzas felt a bit strange, possibly because most tourists in the area are going to the foreigner-only resort area of Varadero, and possibly fail to comport themselves in a manner best representing the pride of their home nation.

After dinner we walked to the central square, where an orchestra played some Cuban music on the bandstand. But alas shortly after we arrived it began to pour with rain, the orchestra packed up, and we began to explore the loggias around the central square. Santa Clara's square is home to one of the eight famous pre-revolutionary theatres in Cuba, through which many of the opera stars of turn of the 20th century performed! Unfortunately this one is no longer structurally sound and must be appreciated from the outside. The rain cleared up and we walked back to our place. Along the way I noticed a TV show about Pavarotti through someone's open window. I would have liked to stay and watch, but C thought that was weird so we walked home. There are only 5 channels in Cuba (same as Australia) so we actually heard Pavarotti singing the whole way. But when we arrived we channel surfed for a bit and couldn't find him! Just before bed I walked to the Santa Clara railway station, got a lot of strange looks, checked out the timetable, and then retired for the evening. 

Day 6. The $5 breakfast in Santa Clara was enormous! It covered the entire table. I took only one of each thing and I nearly exploded. Given the uniformity of breakfasts in these places I wonder how expectations are being transmitted! We decided to spend the day exploring Santa Clara, while dodging very enthusiastic taxi drivers. We checked out the Che Guevara monument and museum, which contained many of his guns, writings, and even his 6th grade report card! We sussed out the bus station, which required yet more avoiding taxi drivers, literally dozens of them screaming "taxi my friend habanabadadedomatanzasinfugo", which made me wonder about the incentive structure. Have they ever gotten a fare by screaming louder than the guy next to them? It was pretty clear the whole trip that there were way more people wanting to work in tourism than tourists, but that the underlying infrastructure to support the tourists was pretty much at capacity. 

That afternoon we checked out the cigar factory, which was amazing. About 40 people each working at a specialized desk with various presses and containers for different kinds of leaves. It takes them 9 months to learn to make a cigar, and each person makes the entire cigar, between 70-150 a day, from start to finish. There is no production line! The QA procedure included measuring the back pressure of the rolled leaves to ensure that they weren't too tight or too loose. 

Later on, we met up with some couchsurfers who I had found the previous day. Our surfer, M, studies banana genetics and CRISPR (!) at the university, and showed as a cool hill from which there was a good view. We ended up talking for nearly 4 hours, met M's husband (who is obsessed with rockets!), the dog, the family, and had a great time. They explained why Cuba is so proud of political autonomy, and wary of foreign investment. It is a compelling argument but it does illustrate the industrial precariousness of wanting to be un-aligned within the western hemisphere. We also took in a monument to the battle Che led in Santa Clara, which was the turning point of the revolution. They managed to interdict a train filled with weapons for the opposition, and then achieved a convincing victory despite a terrible numerical disadvantage. That evening we found a good pizza place, packed up, and slept. 

Day 7 we got up before 7am, confronted a total and ongoing failure to connect to the internet, then walked back to the bus station. Dodged the taxi drivers, chilled in the waiting room, killed mozzies, then eventually boarded the bus. It was overcrowded (they pick up hitchhikers along the way) and had window shades that made looking out impossible. I was reading a good book, and I'm glad we eventually used the system that foreigners are recommended to take, but the three hour trip along an almost empty three lane highway was nowhere near as exciting as a midnight train to an uncertain destination! We determined that the bus station was a lot further from the city center than the point of closest approach, so jumped off in a great hurry as the bus turned away from downtown Havana. We walked into town, arriving at our place just as two other tourists we had met on the bus also arrived, having gotten off at the terminal and taken a taxi. Ha! Saved $5! We found a place to stay, did a lap of the old city, then went on an art gallery crawl finishing with the national gallery, which was pretty good. Unfortunately our plan to go salsaing on our last night failed when every salsa club we tried was closed! We'd heard a lot earlier in the week but missed our chance! We headed off to dinner on the fifth floor of some 19th century palazzo, where we encountered a father/son pair who had sailed to Cuba to support a Hobie Cat race from Florida. Dinner was pretty tasty, after which we walked back along the Malecon, took an electric shower, and abruptly passed out from exhaustion.

Day 8, Sunday, the last day. We packed our bags, checked wifi, then took a Coco Taxi from out the front of the old hotels through the town towards the University of Havana. It turned out to be closed on Sundays, and the physics department was derelict. We walked further into the distant reaches of the town, seeing the hospital, Jose Marti Plaza (my sandal broke at this point), and the Colon Cemetery (applied duct tape to sandal). This cemetery had nearly a million interees, hundreds of varied mausoleums, and distinct areas separated by class and profession. Apparently its architect died before completion and was the first occupant! These days it is overfull so remains are removed after a few years and warehoused. 

From there, we walked to the John Lennon park, and eventually stopped at a fancy hotel overlooking the ocean, where we sipped drinks in the bar, which probably made us ill. We watched the fancy yank tanks with their incredibly shiny and probably structural paint glide by, and relaxed before our mad rush to the airport.

We scoped out a fancy bright red 1959 Impala with wings and white seats, and took it to the airport. Along the way, we got rather hot under the sun, and I admired the workmanship that had gone into making this ancient vehicle look and run okay. Almost everything except the chassis was non-original, including the suspension! The silver trim seemed to have been made from some shiny metal stock by hand, the windshield was plexiglass, and so on. Incredible! He dropped us at the fancy terminal so we spent our last $5 taking another, slightly less shiny ancient car to the old terminal, where we got through to the departure lounge with no hassles at all. Unfortunately we had no money so we couldn't buy any food, but an engineer from Virgin Galactic recognized C's astronaut and south pole patches and we had a good chat. He had spent a week with Cuba's national television and animation studio, which apparently has a large focus on education. 

Walking out along the tarmac to the waiting 737-900 was an odd feeling. Passenger jets are miraculous enough at the best of times, but shimmering in the heat, every rivet precisely flush with its compoundly curved double winglet, it looked like a spaceship. A spaceship that would zip us up into the stratosphere to hurtle homeward at a solid fraction of the speed of sound. 

Cuba. Wow. What a place!

Saturday, May 13, 2017

A roadmap to an industrially self-sufficient Mars base in the minimum time

Edit: After this post was initially published (May 12 2017), it generated a flurry of wonderfully constructive comments, particularly on Hacker News ( I have used them all to improve the text, flag some limitations, and better understand the problem. Let's keep the conversation going!

Dear reader(s), let’s talk about how to get to a self-sustaining Mars base as quickly as possible. This is a challenging question to approach, because we just don’t know enough about huge slabs of the problem. Nevertheless, it is possible to approach this problem in a rigorous way and paint, at least in broad brushstrokes, much of the solution. Some of this material is introduced in Chapter 22 of my book “How to get to Earth from Mars: Solving the hard part first” published in 2016 (, but this blog post will take a slightly different approach.

The problem of a self-sustaining Mars base requires the development of much technology that does not exist. Copious and reliable electrical power will be required on Mars, provided most likely by a nuclear fission plant(s) or solar, but is beyond the scope of this discussion. Similarly, a transportation system capable of flying to and from the planet is a substantial problem, but not one I will deal with here. I will be assuming something like SpaceX’s baseline ITA system is available, capable of delivering payloads exceeding at least hundreds of tonnes every 2.2 years, coinciding with the launch window. Details can be found at This blog attempts to answer the question of “What will we do once we’re there?”

Let’s illustrate a picture of how emplacement of industry on Mars may occur, bearing in mind that this will be a rather ambitious timeline, then fill in some of the detail. Technology and ability to fly cargo and humans to and from Mars may not exist forever. Therefore it is wise to try to achieve self-sustainability within a fixed timeline, of perhaps 50 years.

Today on Earth, which is better adapted for life than Mars, between 10 and 100 million people are needed for a sufficiently diverse economy to support the “full industrial stack”, which includes primary resource production, secondary manufacturing of basically everything, and other tertiary services. The number of economic blocs capable of “making anything” number perhaps 5: China, Japan, USA, Europe, India, and perhaps South Korea. Several larger countries are not sufficiently economically advanced. Cuba, North Korea, Australia and Russia (once part of the former club but now enduring industrial decline) all have populations well over 10 million but are entirely dependent on trade to obtain some advanced technology such as computers, aircraft, container ships, engines, cars, and so on. It is impossible to predict with certainty the minimum number of specialists needed to create industry efficient enough to support itself on Mars with the technology of 2060, but one million is probably within an order of magnitude of the true number. To elaborate slightly, I can imagine a machine fab shop with 1000 very clever engineers who can make basically anything from ore given enough time, but sooner or later  (sooner with fewer people) they would be unable to make parts rapidly enough to replace them faster than they break in real world use. Sufficient manufacturing efficiency demands a higher production rate with fewer resources, most prominently human labor!

Scaling to one million people in 50 years, or around 20 launch windows, implies a doubling of population every launch window, which is about a factor of 10 every decade. One decade per decade. Ambitious, indeed, and a great place to start crystallizing an approach.

It seems wise to assume, at least initially, that cargo capacity is closer to constant than exponentially increasing. Therefore, each increase in population mandates a commensurate increase in self-sufficiency, so that the same total cargo capacity can bring enough machinery and supplies to keep everything working.

In the following figure, I plot a hypothetical trajectory of a population from exploration/outpost phase to full self-sufficiency assuming limited cargo transfer capability. On the vertical axis I have constructed a rough order of goods by some metric of inverse manufacturability, and on the horizontal axis I have population. The red line marks a hypothetical population- independence trajectory, and the purple dot the inflection point at which demand for cargo reaches its maximum. Beyond this point, industrializing becomes easier.

The “cusp of settlement viability” is an important concept. It is possible to imagine the dropping of cargo and humans on Mars with instructions to “get cracking”. But every machine and human on Mars represents a future liability for the replacement of that machine and life support of that human, a liability which has to be fully priced into the future. Scaling more quickly than technology and shipping capacity can support guarantees a point in the near future when those liabilities come due, machinery and local industrial capacity undergoes dramatic collapse, and everyone dies of suffocation. There is a serious side to this speculation.


Let’s dig a little deeper into the list of goods or capabilities on the vertical axis. For this figure, I ranked commodities according to specific cost, that is, their cost on Earth normalized by their mass. The reason for this is that the major cost of importation to Mars is driven by the mass of the item, while the cost is a very blunt proxy for manufacturing difficulty. For reference, the cost of flying a tonne of cargo to Mars will not be less than $1m, and could easily be 10x or 100x this, at least initially.

In terms of mass, the greatest requirement on the surface, by far, is oxygen. Oxygen is an underrated element, but accounts for something like 89% of the mass of water, the majority of the mass of rocks, and we also need it to breathe. More importantly, each SpaceX Mars ship needs thousands of tonnes of it for propellant to fly back to Earth. In fact, any non-trivial Mars return flight requires oxygen to be made on Mars, so that’s the first thing on the list.

Fortunately, oxygen is readily available on Mars as the atmosphere is mostly CO2, which is 73% oxygen by weight. It is also worth pointing out that not all in-situ resources are created equal. Atmosphere-derived materials (oxygen, carbon) are easier to obtain than liquid water (via an aquifer or well), which in turn are MUCH easier to obtain than metals from various ores on the surface, or anything that requires digging (although: Boring Company!). The next most important thing to obtain is fuel, of which the SpaceX Mars ship also requires hundreds of tonnes to return to Earth. Potentially the vehicles could bring enough hydrogen from Earth to make methane on Mars, but doing so would consume much of their cargo payload. Therefore, the capability to make enough fuel on the surface of Mars entirely from local resources marks the “efficient cargo utilization threshold”.

The list of items in the figure are based on Earth-costs of production, which do not always map perfectly to cost of production on Mars. In particular, human labor is vastly less available on Mars, and arable land is non-existent. The cost of producing food (carbs) is therefore higher and perhaps should be promoted at least above masonry. One other salient point is that beginning the process of a masonry-producing industry does not mean that the oxygen production plant no longer requires shipment of any parts or humans from Earth. Making a product locally implies an improvement in overall mass efficiency, but not the complete elimination of supporting cargo shipments, something which is not well illustrated in the diagram.

Human labor is so expensive, in fact, that it is worth considering the trade between maintaining and replacing machinery. Obviously machinery sent to Mars must be designed with a high level of reliability, but labor is so constrained on Mars that machines must be capable even of self-maintenance or problem diagnosis. This is a completely different paradigm to the “rugged individual trying to survive” such as Mark Watney in The Martian. I estimate that a machine must have at least 99.9% no-worry uptime reliability to be worthwhile, because the marginal cost of sending and supporting another human solely to maintain the machines is so high. Human labor is so expensive on Mars that it will have to be employed almost exclusively on the deployment on new equipment, rather than constant maintenance of existing machines. For Earth-supplied machinery, it will be more cost effective to provide machines that operate with very little to no intervention and replace them frequently, than to have a labor-intensive machine shop and humans working in it. For Mars-manufactured machines, the calculus is a little different, since it is easier to make a new machine from an old machine than from raw materials. As we will see below, however, there is likely to be little direct human involvement in the (re)manufacturing of machines on Mars.

The situation is even more dire than that, in terms of the scarcity of labor. Not only is there not enough labor available to maintain a constant level of productivity given inevitably decreasing machine health, productivity has to scale with the scale of the base. In the above diagram, the population increases by a factor of 10 every 10 years. Each decade, a new industry is brought online. Therefore, there are four launch windows to deploy, pilot, test, and scale that industry. The next decade will bring 10x as many people, but those people will be primarily devoted to that new, more labor intensive industry. The first 10 people who operate the oxygen plant are mostly “locked in”, while the productivity of that plant has to scale aggressively to meet the needs of the growing base. There are few industries on Earth that can point to doubling the productivity of a human every 2.2 years, but to maintain the schedule that will have to be achieved during the early phases of base construction.

During the latter phase, per-capita productivity will have grown enough that it will not be necessary to send a million people in the final decade to do state-of-the-art computer microchip fabrication, but it is difficult to predict how many will be needed, or even exactly what computers will look like by then. The rate at which individual productivity grows or tapers largely determines the shape and progress of the red trajectory, with the win and peak population demand occurring very soon after the purple cusp. At present, all we can say for certain is that any progress in the initial decades depends on rapid exponential growth of the capabilities of the first generation of settlers.

It seems clear that no matter how fast the Mars base astronauts can swing wrenches, growing demands for productivity will mandate the deployment and exploitation of automated labor. Humans will, in some sense, nurse into existence a base populated mostly by and for robots. An individual robot is probably even less capable of scaling its productivity beyond its design than a human, therefore the number of robots will also have to double every launch window, which provokes another interesting modification to the technology priority acquisition timeline.

The Mars base will need to make robots, or at least parts of robots, as soon as possible. Fortunately, the capability to make copious methane fuel creates the foundation for ethene and polymers: plastics. That is, a Mars base that has not yet scaled to the mining of solid ores is able to make plastics accounting for the majority of the mass and bulk of a robot arm (or leg), and scaling this ability will be of paramount importance. Other essential robot components like actuators and processors are extremely labor intensive to produce, but relatively light and can be flown from Earth while local manufacturing scales according to its needs. Pumps, valves, filters, bearings, latches, brushes, robots, and regulators are all wear parts, some of which can be made locally of printable or machineable plastics where doing so is cheaper than importation from Earth.

The thought of huge facilities full of brightly colored 3D printed plastic robots building each other at a fabulous pace is not what I had in mind when I started thinking about Mars industrialization, but it is a compelling vision. Large scale integrated robotic factories are currently being developed around the world, such as the Tesla gigafactories. Tech development that's good for Mars also makes a lot of economic sense on Earth. In fact, some hobbyists on Earth have gotten dangerously close to building microgigafactories in their garages. The reprap project ( represents a microcosm of the overall problem - a 3D printer which can print (most of) itself. A more complete vision for hobbyists might be the creation of a “robotic garden” with commercial off the shelf components generating plastics from CO2 and water, and gradually 3D printing replacement parts until the entire manufacturing chain has evolved into a self-maintaining software-defined plastic ecosystem requiring minimal hands-on human involvement.

At the beginning of this post, I mentioned that all but five or six countries on Earth were incapable of making enough stuff to be self-sufficient. I am a big fan of trade and economic efficiency provided by trade, but it has left smaller nations vulnerable to industrial dependency, economic weakness, and potentially global trade disruption. In fact, any disruption of the global economy in its current hyperinterdependent phase may not be recoverable, seeing as we’ve already depleted all the easy-to-obtain surface resources. It is much easier to emplace industrial self-sufficiency even in some bone-dry valley in central Nevada than on Mars, so the development of technology which permits that is an essential safeguard for civilization on Earth, as defined by the ability to make or obtain “anything” with a trade-competitive level of overhead.

Although we have had to remain agnostic about huge facets of Mars industrialization, including precise numbers on who, when, where, how much $, how big rockets, and so on, we have made some progress. We have seen that a labor-cost focused approach, normalized by the requirement of “self sufficiency, ASAP”, has illuminated the importance of understanding the relative value of transportation, human labor, maintenance, and robotic labor.

Monday, April 17, 2017

Does Lunar resource exploitation make sense?

Hello loyal reader(s). Although I haven't blogged now for a few months, that doesn't mean I've been doing nothing. On the contrary, I have been advancing several super cool projects and today I'm going to write about an aspect of one of them.

Every few years (roughly coinciding with congressional budgeting schedules) NASA gets antsy and proposes some new ideas. Recently, they have included the asteroid capture mission, the Europa lander mission, and all sorts of other cool concepts. On the crewed side, however, NASA is (and has been) stuck in an organizational quandary, wherein it is allocated just enough $$ to do what it has been doing, and not quite enough to make a solid start on any of its mandated new programs, such as the Mars mission.

I have written extensively about crewed Mars exploration in the past, and a distillation of much of that is kept at . The main problem with Mars exploration is that there is no way of doing it with existing rockets. Developing new rockets is expensive, large rockets particularly so, and so the hunt has always been on for finding smarter ways of getting more mass to (and from) Mars using rockets that fit, somehow, within the current budget. This is a conceptual mistake, in that huge new rockets are certainly expensive, but they are cheap compared to the programmatic costs incurred by having a rocket that while undeniably huge, is just not quite huge enough. I am reliably informed that similar cost inefficiencies can occur in other areas too!

This blog post deals with one particularly baroque proposal, namely the installation of a robotic fuel mining base and "gas station" on the Moon, to refuel spaceships on their way to other places. This proposal has been floating around for a while but has recently gotten a lot more attention than is, perhaps, warranted, hence this blog. The topic is quite arcane so I will do my best to keep the writing both concise and precise. First, I will summarize the results, then delve into entirely inappropriate levels of detail.

Much of space exploration advocacy is performed by way of analogies. Unfortunately there is no good analogy for this particular proposal, so instead I have used math to compute some best case cost estimates for Lunar resource exploitation, and compared them to the alternate method (Earth-launched resources) computed using median case cost estimates. This biases the comparison toward Lunar fuel, but will it be enough?

This table shows the per year cost for a program designed to deliver 100 metric tonnes of cargo (such as water) per year to various locations in cis-Lunar space. It also estimates the development and deployment time to reach rate after program start.

Earth originEarth originEarth originLunar originLunar origin
Δv (km/s)
Cost ($m/year) expendableCost ($m/year) reusableTime to reach rate (years)Cost ($m/year) reusableTime to reach rate (years)
Earth surfaceKSC0NA0.150.05NA>15
Low Earth orbitLEO9.43001202>1000x5>15
Geosynchronous transfer orbitGTO2.446002402>1000x5>15
Trans-Lunar injectionTLI0.687503002>1000x5>15
High lunar orbitHLO0.147503002>1000x5>15
Low lunar orbitLLO0.689003602>1000x4>15
Lunar surfaceLS1.7318007205>1000>10

The most optimistic cost estimate for the robotic Lunar port suggests costs of $1b/year for 15 years to reach rate, and that's what I've used in this graph. I think all reasonable experts would agree it's highly unlikely to cost less than that, or to reach rate (100T/year delivery to some location) faster than that. The xN quantities encode the fact that moving fuel from the Moon to other locations uses >75% of that fuel in delivery. So if $1b/year for 10 years is enough to produce 100T of water a year on the Moon, additional time and tech and fuel and money is required to move that fuel to, say, Low Earth Orbit.

In contrast, we see that using today's technology at today's prices, the same quantity of water (or any cargo) can be delivered from the Earth to all the same locations at a fraction of the cost and a fraction of the time. Employing reusable rockets, such as those currently being pioneered by SpaceX, may reduce costs even further, to the point that the cheapest, fastest way to get even raw materials on the Moon is to launch it from Earth instead of mining it locally.

Before I dive into the nitty gritty, it is worth stating that a similar analysis focused on the use of Mars' atmosphere (rather than the deep frozen heavy metal-laced dirty snow of the moon) for propellant production shows a clear advantage over launching all the fuel required for the Mars-Earth trip from the Earth. 

Now I can dive into the nitty gritty. First I'm going to write about the why, then I'm going to write about the how.

A really good rocket can launch about 4% of its initial mass into low Earth orbit (LEO). For the Saturn V (the most powerful rocket ever built), the orbital payload was about 140T. To get from LEO to the moon, Mars, or elsewhere, yet more fuel has to be burned. For LEO-Mars, around 25% of the LEO mass can be payload, the rest has to be fuel and oxidizer. At this point even the Saturn V can launch only 35T to Mars and that's not really enough to keep four brave astronauts alive for a three year mission and then bring them back.

Instead, the 140T in LEO can be the payload and spaceship with empty tanks. 3 more launches of the Saturn V can increase its mass to 560T, at which point it has enough fuel to fly to Mars with 140T of payload, which is much better.

Unfortunately, four launches of the Saturn V is much more expensive than one, and building a rocket 4x bigger than the Saturn V, while exciting, is not part of the solution space NASA is presently looking at, possibly because the manufacturing facility at Marshall Space Center in Alabama couldn't fit it through the door. 

If ~400T of propellant is needed in LEO, however, perhaps it could be obtained from the Moon? But how? Remember that the baseline expense case is three more launches of an already existing launch vehicle, so any alternate scheme should be some combination of cheaper, safer, faster, or more scale-able.

The best Lunar resource extraction architecture I've come across so far looks something like this.

The following new robotic vehicles are developed on Earth:
- A solar electric propelled orbital tug.
- A hydrogen/oxygen powered lunar orbital shuttle and lander, based on the Centaur upper stage.
- A solar powered fuel processing plant with some capacity for remachining or replacing worn out components.
- A Lunar orbital nanosat platform containing numerous guidable lead or steel rods.
- A battery powered combine harvester robot that ingests lunar regolith.
- A battery powered generic transfer truck with robot arms and useful tools.
- A solar powered deep space electrolysis cryogenic fuel depot. 

The lunar components (in sufficient numbers) are deployed near one of the permanently shadowed regions at the lunar pole, landing on the landing vehicle. The orbital nanosats deorbit cavalcades of dense metal rods to precisely impact the mine site, performing a kinetic drill and blast procedure. The combine harvesters scoop up the fractured regolith, physically process it for water and other volatiles, and transfer the ore to shuttle trucks while dumping the depleted material, which can also be used (eg sintered) to make roads or landing pads. The trucks shuttle the physically separated ore back to the fuel processing plant, which performs chemical separation and packages water ice in aluminized mylar coated pallets for transportation. It also performs limited electrolysis to make fuel for the lunar orbital shuttle's ascent flight.

The shuttle flies the water ice to low Lunar orbit, depositing it at one of the deep space fuel depots, refuels with electrolysed fuel from that depot, and returns to the lunar surface. That part of the operation has a mass efficiency of just 20%. That is, 80% of the extracted water is used propelling the shuttle to and from the Lunar orbital depot. Hydrogen boiloff may be mitigated by (eg) platinum catalysis and conversion back to water.

Non-hydrolyzed water ice is collected at the lunar orbital fuel depot and transported by solar electric tug back to low Earth orbit, consuming a relatively trivial fuel fraction but taking at least several weeks. Water ice is stockpiled at the low Earth orbiting depot(s), which must hydrolyse it all in time for the required launch to Mars, or wherever, and requiring huge solar arrays to do so. 

There are numerous other proposed systems which are less mass or time efficient, or have less overall benefit. As an example, it may be possible to fly a Mars vehicle to land itself on the Moon, refuel there, and then fly on to Mars. However, it would take less fuel to fly from LEO to Mars directly. Similarly, the mass benefit of any post-launch refueling drops off extremely quickly for any depot beyond LEO. Although the Moon has relatively low gravity, its lack of an atmosphere extracts a toll in both directions; launch and landing.

If the above scheme for mining propellant from the moon sounds complicated, that's because it is! In fact, of millions of potential failure modes, the net outcome is the same - not enough water delivered to LEO, or even none at all. To mitigate the programmatic risk for the crewed flight to Mars, a mechanism for the delivery of water from Earth to top up the LEO-based solar powered fuel depot must be provisioned for. At which point, of course, it is (by the table above) far cheaper and quicker to cancel the lunar program entirely and refuel the depot, or the Mars vehicle itself, using that same Earth-launched mechanism. 

I really do not believe there is much more to say about the Lunar-derived fueling concept. Here are some links to other resources if, for some reason, your curiosity is not entirely sated.

Sunday, December 4, 2016

14 days to have a relaxing holiday.

2016 trip to New Zealand

Regular readers may note that of late my holidays have been somewhat compressed. In this blog I will describe how C and I filled 14 days away from Los Angeles.

On Saturday November 12 I woke exhausted. All I had to do was pack, complete a six hour dance rehearsal, eat dinner, clean the house, then go to the airport. The checking agent was in training and said "You're in seat F, which is not window, not aisle... it's nothing. Ooops." Said I "Did you accidentally upgrade me to first class?" Alas, it was not to be. Seat F, on this particular aircraft, was in the exact middle of the plane. I felt like the world was turning around me, noone climbed over me, and I slept like a baby.

The following day, Sunday, was my sister A's birthday, but thanks to the international dateline, I did not have to observe it. Instead, I landed in Brisbane on Monday, stumbled through immigration, and attempted to pick up my rental car. My credit card fraud division helpfully blocked my card, although (as usual) I booked the relevant flights with the same card. Get on it, people! Needless to say I couldn't recharge my Australian card with a broken credit card, but I eventually broke the cycle of endless pain, and drove at the ludicrously low speed limit south to the border. On entering NSW, I turned the clock forward one hour and 20 years, picked up some groceries, and made my way to one of the old family farms in Huonbrook. 

I was dismayed to find that all the chickens had been eaten by snakes, but I spent the next two days cataloguing everything, from the platypus pool to the spring to the solar power system to ancient photos going back to my grandmother's grandmother. The house belonged to my grandmother's sister R, who passed abruptly a few months ago. 

At about the same time, it wasn't entirely clear if my fiance C would be able to get out of the South Pole where mostly weather had trapped her. If she was delayed a week, I would cancel my trip to Christchurch and fly instead to Canberra where my brother is operating on people. At the very last minute I heard that one of the key flights made it to the South Pole, so I resolved that optimism would triumph and, early on Wednesday morning, headed back to the airport. 

On arrival in New Zealand, I saw the effects of various recent earthquakes, including one from a few days before. During my time in Christchurch I felt about half a dozen aftershocks, which is more than I've felt during my six years in LA. I checked into an AirBnB where my host was a 3D printing enthusiast with a pet talking parrot. Over the next day or so I explored the city, which has been mostly destroyed (and since very partially rebuilt) since my previous visit about 15 years ago.

On Thursday evening I headed back to the airport and, on Friday morning only one day after we initially guessed, C arrived! She only smelled lightly of jet fuel, and was beside herself with excitement, mostly at the prospect of unlimited showers and 24 hour internet. 

The earthquake had thrown our previous plans into disarray, so instead we picked up a rental and headed south into the remote and sparsely populated mountains of the South Island. Over the next few days we stayed at a series of gorgeous lakeside towns, including Tekapo, Wanaka, Queenstown, and even drove across the mountains to Haast for a trip to the beach. Our mission to locate penguins was defeated by sandflies, so we took out some kayaks and paddled through the wind and scattered rain for a few hours. 

We did numerous side trips to various lakes (for skimming rocks) and forests (for examining moss and waterfalls) and in general just had a bloody marvellous time. We checked weather forecasts for Milford Sound and tried to be clever, taking a plane from Queenstown. In the end we were defeated by low cloud, so settled for a quick zoom down the Shotover River gorges in the quiet, peaceful jet boats, followed by a haircut, trip to the laundry, and zoom up the hill to the Overlook Restaurant, where we ate dinner as the sun set over the lake. We followed this with a hike among the wildling pines, then finally got some rest.

The following day we flew to Auckland, drove to Parakai hot springs, checked out their local aerodrome, soaked in the geological water, made dinner, and got some sleep. The following morning we checked out as the police arrested someone else staying at the hotel, drove back to Auckland, and had an amazing tour of Rocket Lab, a New Zealand-originated company that is building the Electron, one of the world's cutest rockets. It got started as a backyard inventor (Peter Beck) building rockets for his motorbike and has now developed into one of the only surviving microlaunch companies. They're focusing on hundreds of launches of small sats to Low Earth Orbit, at $4.9m/launch, and it was really amazing to see what they were up to. One of the most interesting aspects of the Electron is that its turbopumps are powered by electric motors. It turns out that with current batterytechnology, this constrains the overall size of the rocket to smaller payloads. These days most satellites are getting smaller as companies try to iterate the technology more rapidly.

We found lunch, C did an interview, then we headed for our next hotel in the hills to the west of Auckland. I thought there might be a nice walk to a beach near Piha, and I wasn't wrong. The hike started as an easy stroll throught the coastal scrub, before it became a near vertical series of boulder problems which eventually deposited us on an empty beach surrounded by gigantic cliffs. A waterfall tumbled down and flowed into a dark cave, from which we could hear the roar of the surf. The hike back up was faster than the descent but rather hard going. Back at the hotel we had the most amazing dinner and explored the grounds rather thoroughly.

Up until this point we had been extremely lucky with the weather, mostly skipping town just as the rain came in. Finally, it caught up with us. The next morning, it thundered down. We went on a deceptively long hike to a nearby waterfall with one rain jacket between two. By the time we got back to the car I was rather soggy, but the waterfall itself was spectacular. 

The next stop on the agenda was the Auckland Zoo, where we spent most of our time exploring the exhibit on New Zealand animals. We saw a Kiwi! It was rather large, like a soccer ball with feathery fur and a spectacularly long beak. We also saw some little penguins, which were just adorable. 

That evening we checked into our last hotel for New Zealand, splashed about in their pool, tested the pillow menu against pillow fights, and got lost in a room considerably larger than my house. We ate yet another spectacular vegan dinner, closely followed by a spectacular breakfast, both at Hectors restaurant, then headed once more for the airport.

We had a 16 hour layover in Sydney, during which we found various Australian animals (kangaroo, quokka, platypus, echidna, koala, bilby, wallaby, etc) and ate a great dinner with my parents. The following morning we headed to the airport for the last time, found a friendly looking plane, and headed back to the states. The flight was uneventful, and I got through secondary screening in a record 13 minutes. We followed that with a Lyft back to Pasadena in a near-record 26 minutes. As I write this I'm surrounded by the detritus of unpacking and moving, as C and I are moving in together! 

That, dear reader, is how one can spend 14 days, six hours, and one minute in luxurious relaxation!

Thursday, September 29, 2016

SpaceX Mars plan analysis

Update: Try your own simulations of Mars EDL with my code:

On September 27, 2016, SpaceX finally revealed their Mars transportation architecture ( It was a very exciting moment. Regular readers will know that I have engaged in idle speculation on the topic, and I was gratified to see I got the details mostly right, though their system is a lot larger (up to 450T cargo!) than what I initially had in mind. If you're interested, see my best guess from 2015:
That said, I would be very surprised if the final product looks much like what we saw today, especially for the ship. The architecture presented is fairly conceptual, especially on some of the less mass-affected issues.
With that in mind, what SpaceX presented today can be broken down into a few different parts: a conceptual concept of operations (conops), a CAD draft and pretty animations, and most enticingly, early demos of core tech. Let's look at each in turn, and I'm going to assume familiarity with the presentation: .
The architecture is designed around the principle of "cheaper is better" which almost always drives "simpler is better". Yes, it is possible to get more mass (maybe) with less fuel if there is an intermediate stage or multiple cores, but the most overlooked handle is the size of the rocket. Mars requires a developing a new super heavy lift rocket anyway, so it may as well be BIG! The SpaceX booster, with a nominal 550T to LEO capacity, fits the bill. 
Having total reusability drives a big Mars vehicle that can fly from Mars back to Earth with a single stage, requiring about 8km/s of delta-V. Indeed both ship, tanker, and booster can fly single stage to orbit on Earth, albeit with no payload. The same Mars vehicle also has to perform entry descent and landing on Mars, and has enough fuel to fly from Earth LEO to Mars, and from a suborbital boost to LEO. This means it has to be refueled along the way: In orbit by 3-5 tanker flights, depending on how the masses wash out down the line, and on the surface of Mars. The rest of the presented masses and thrusts all check out. The engine clustering on the ship is an interesting approach, with 6 vacuum engines and 3 sea level engines (smaller bells). Thrust wise, sea level engines are only needed to land on Earth or under high dynamic pressure on Mars, and one is plenty. Three provides some redundancy, and may figure in some launch abort scenario. Mars is so close to vacuum that the vacuum raptors will work there too. Given that landing on Earth happens at the very end, it may even be possible to detach part of the expansion bell so that the vacuum raptor engines can function in the Earth's atmosphere.
Areas that were light on detail include the transition to powered flight during descent on Mars (or Earth). The video showed it nosing up indefinitely, though that would require terrific pitch authority and amazing anti-slosh fuel tank baffles. Downmass capability on Mars is driven by aerodynamic constraints, so I ran the SpaceX sizes and masses through my Mars EDL simulator:

(Click to expand) Left panel: Historical data from robotic missions, showing Mars entry profiles. Parachute descent typically commences in the bottom left at around 500m/s. Central panel: Results from my ballistic motion simulation reproducing behaviour of previous landings, validating the code. Right panel: Entry profiles of several hypothetical future Mars vehicles, with Curiosity for reference. LDSD levels out a little higher (depending on total loading), while Red Dragon needs a significant mass offset to achieve enough lift to not hit the ground. The three curves marked ITA (Interplanetary Transportation Architecture) represent different lift parameters for the SpaceX ship. Horizontal flight represents banked turns to prevent multiple skips out of the atmosphere. Their high lift and high entry speed compensate for their high mass, and they don't get too close to the ground. Mars' highest mountains are >20,000m tall.

I was pleased to see that despite the high mass (up to 800T) the high entry speed, generous cross section, and lifting body concept results in an entry profile that doesn't involve a compulsory crater. Thermally speaking, SpaceX claimed a maximum temp on entry of 1700C, which seems a little low. If PICA can endure 1.2kW/cm^2 heat load, that implies a peak heat shield temperature of about 3800K, given a sensible surface emissivity. A fully loaded ship decelerating at 6gs is dissipating more like 67kW/cm^2, but most of that turns into a very hot, shiny, pretty wake like a shooting star.
Similarly, the propellant farm was presented as a series of chemical reactions, without specifics on mass, efficiency or output rate. About a megawatt of electrical power, continuous, is required to refuel the ship on Mars is a single year (365 days). Most of this power is spent on electrolysis. A solar array capable of producing this (without tracking) would be around 10,000m^2, which is not impossibly large. Solar panels are virtuous, in the mass sense, since they can be made practically two dimensional. 

CAD Models
The CAD models look great, but clearly represent an early draft. The interior space of the crewed module is a bit spartan (needs bulkheads), while the oxygen feed lines to the 42 raptor engine cluster look a lot like a brain angiogram scan. Getting prop feed to 42 engines that are throttling and pogoing, across a giant thrust structure trampoline, while damping every instability and cavitation, sounds like a nightmare/worthy engineering challenge to me.
Similarly, I'm not convinced about the giant window or the downward facing aero strakes, but these parts are less important at this time. The long lead stuff is engines and tanks, and those parts in the CAD are nicely specced out. 

Core Tech Demos
This was the most exciting part by far. The reusable architecture calls for single stage return from Mars. It's all very well to draw spaceships (spaceship!) all day long, but when the rubber hits the road, the system requires a monster engine, as well as fuel tanks with practically imaginary mass. That's a good place to start, and that's what SpaceX has been working on.
I don't know enough to comment on their carbon fiber fuel tank prototype (though I liked the chandelier), so I'll focus on the engine. The Raptor engine has haunted my dreams for years. Unlike the rest of the architecture, here cheaper does not drive simpler, at least at the combustion cycle level. When it comes to high efficiency, the Raptor uses every trick in the book and probably a few that aren't written down yet.
These include full flow staged combustion, multi stage pumps, very high chamber pressure, and the latest in materials and manufacturing tech. Big moving parts in this engine have to withstand high pressure high temperature preburned (ionized) oxygen, which makes a lava-proof submarine look easy by comparison.
And to their credit, SpaceX designed and built the hardware, and showed a video of a short test firing, probably at around the 20% thrust level. Obviously, the engine is far from qualified. But a working demo is a long way from a paper study, it convincingly demonstrates that SpaceX has world leading vision and core competence in rocket engine design.
Final Thoughts
The SpaceX Mars plan is a compelling vision for moving lots of humans to Mars. A complete system will be much more detailed and probably a bit different, but importantly this lays a technical foundation and is a great starting point for future system discussions.
To read more about these and other technical challenges facing crewed Mars exploration, check out my book "How to get to Earth from Mars" at .

Sunday, September 25, 2016

Mars Society Talk: Confronting the Credibility Gap for Crewed Exploration of Mars

Confronting the Credibility Gap for Crewed Exploration of Mars
(Notes from talk on September 22, 2016, at the Mars Society Conference. YouTube video!)

Look at this amazing picture of Mars! I don't think I have to try very hard to convince you that it would be cool to stand in Gale Crater and look through the haze towards Mt Sharp. But to achieve our goal and send humans to Mars we have to convince a lot more people, and that's what I'm here to talk about today.

First, a bit of information about me. I did a PhD on gravitational waves at Caltech, and got an opportunity to sword fight with my collaborator. More recently I'm the levitation engineer at Hyperloop One, where we're building high speed vacuum trains. On Mars, I made this neat 3D printed ring and then later did some research into emergent flow networks using MOLA data. The Mars crust has deformed, the geoid has changed, and so the rivers don't always go the way you might expect. (arXiv:1606.05224)
So, I'm here to talk about a difficult issue, but I'm not here to criticize pointlessly. It's easy to be negative. I am overwhelmingly enthusiastic about Mars exploration and extended habitation. The credibility gap amongst Mars crewed exploration advocates is a serious issue that hampers that effort. It's vitally important to raise our profile among the general public, since ultimately they will foot the bill, and in general opinions on crewed space exploration range from ignorance to ambivalence to skepticism. And this is not entirely unwarranted. I'm going to talk about three different aspects of credibility, working from the outside in. First, I'm going to talk about public credibility, as mediated by an occasionally unreliable or sensationalist media. Second, I'm going to talk about mixed messaging within the space community, and reconciling authority with humanity. Last, I'm going to offer a couple of illustrative examples to point out that there are still serious unsolved problems relating to crewed exploration, namely entry descent and landing (EDL) and earth return. We have to be more internally and externally honest about confronting our ignorance in this regard.

First up, let's talk about the role of media. Mars One is a perfect case study. More publicity than any other human Mars mission has gotten in years, and also completely vacuous. I googled "Mars One credibility" and got 189,000 hits. The first 6 hits include how Bas Lansdorp, the CEO of Mars One, whose only job is to know everything about putting people on Mars and keeping them alive, got absolutely smashed here in a debate with MIT students last year. "Do you realise the astronauts will run out of nitrogen on day 59 and die?" So Mars One isn't really funny, it has probably set back the credibility of the movement by a decade. Hype, opacity, haste, are all hallmarks of counterproductive media strategy. There is a dark side to publicity.

Let's look at a few examples of imperfect media coverage. Here are two cases from the recent, and highly flawed study suggesting that space radiation caused heart disease in the handful of Apollo astronauts who already died - at rather advanced ages, given their lifestyles! What blew my mind here is that there is not one, but two different stock photos of depressed astronauts in space suits. The ultimate slow news day is hand wringing about radiation or wishy washy psych factors.

The other major kind of shonky coverage covers mythical propulsion. The idea is that spending 6 months getting there is too long, so we can't go until we have warp drive. And so we have articles about actual warp drive. I did my PhD on this sort of thing, not only is it complete garbage, even if it wasn't, it would still be extremely inefficient. Yet these articles have images where we know how many windows the spaceship has! We also have "Mars in three days", from 1g acceleration the whole way with lasers a million million times more powerful than any existing laser, and no mention of how to slow down, how to get back, or how to handle the thermal issues of being shot with the death star. And then you have the EM/reactionless drive, which is less efficient than a Hall effect thruster, and also impossible. Not to mention the VASIMR thruster, about which no-one ever mentions the need for gigantic gigawatt scale space nuclear reactors. Sure, it's cool and an interesting propulsion system to research, but the full picture should be available.
Of course, it's not all bad. A lot of these articles are actually pretty good, the headline just refers to the most controversial aspect of the article to be click baity. The writers aren't bad people, to be writing about Mars already they're one of us, maybe they just need some expert help. I reached out to the writers of the articles I referred to and one of them has already gotten back to me. Which leads me to a deeper point - it's easy to sit in the ivory tower and criticise, what I'm trying to do is show that communication between the general public and the experts is mediated by the media, and we can collate the information better. Sometimes they even get it unbelievably right - how good was The Martian? The first step is to take the Socratic approach (no longer punishable by death) and ask questions. Search Google, Quora, or even the Mars Society Facebook page. And, if you want to be told you're wrong by a thousand people, you can try Twitter.

So, what are warning signs an article is probably bullshit? Does it violate laws of physics? Does it promote transit times of less than 90 days? Does it involve warp drive? What about content-free hand-wringing over psych factors? No-one is saying that psych factors aren't an issue for crews in space for years at a time, but there's a gulf of credibility between the typical slow news day and some actual serious stuff backed by real data. Does the article have no quotations or endorsements from recognized experts? Does it have no reference to peer reviewed papers? Does it have a naked agenda, or uncritical reporting? Lastly, does the headline ask a rhetorical question to which there is an obvious answer: No!?

What can we do to help? Reach out and if you're an expert, make sure your local writers have you on their rolodex. If you like working with writers, consider joining the Science and Entertainment Exchange. Many of my colleagues have consulted on Marvel Movies, and it's always a lot of fun getting a whispered phone call at 2am saying "you're a physicist, how can I destroy the world?" "well, strictly between you and me…"

So we can help improve media coverage, and our problems are solved, right? Well, not really. It's easy to criticise, but it's unfair to do so without also taking a hard look at our own internal messaging. Even the pros make mistakes, and we need to be honest and circumspect about it. To what extent are we responsible for the credibility gap? We should know better than anyone that there are real challenges that can't be wished away, that Mars is hard, and that "all you gotta do" doesn't really cut it when human lives are on the line. Yes, humans will die in space, and on the ground building space machines, but I'm sure we can all agree that we want to minimize people dying for stupid reasons. And so, as a couple of illustrative examples, I'm going to look at the titans of the movement and nitpick for a bit. First, Elon Musk's suggestion that space radiation can be solved with a column of water between the astronaut and the sun. This only works if the column is of a comparable size to the gyroradius of protons in the solar magnetic field, which is a few thousand km. So, the pros sometimes make mistakes, as we saw with SpaceX's last attempted launch. And then the original slides for Mars Direct, I saw as a kid when the Mars Direct book tour came to Australia, which suggested a first launch in 1997. We earn no credibility by pushing optimistic or aggressive timelines. Or, for example, our own Robert Zubrin's oped in 2012 in the Washington Post, suggesting 3 Falcon Heavies to fly 2 humans to Mars, a mission plan that no expert I know hasn't found a problem with. The Dragons are too heavy to land on Mars, and too crowded for people to live in, once all the provisions are also added, like Gemini but for 150 weeks instead of 2. It doesn't pass the sniff test - it smells of desperation. Falcon Heavy is a terrific rocket, but it's not for humans to Mars, or back.

At the end of the day, though, Elon or Bob miscommunicating some small aspect of a hypothetical mission is not the end of the Earth. It's easy to be critical, let's be constructive. Let's go one level deeper and look at two giant issues which are recognized but mostly unsolved, that of EDL and Earth Return. Rob Manning (JPL chief engineer of Pathfinder, MSL, and LDSD) held a series of conferences at JPL starting in 2004, recounted in Chapter 5 of his enjoyable book. At these conferences, the EDL challenge was recognized, defined, explored, and even now, 12 years later, there is no dominant, obvious solution architecture. A lot of the proposed solutions will be covered in the following talk by Kshitij Mall, so instead I'm going to describe only the problem. A great book if you are looking for a description of the state of the art is (MSL's EDL lead) Adam Stelzner's "The Right Kind of Crazy".

What is the EDL problem? We don't know how to land more than about 1T on the Martian surface. We obviously need to land 10-100T for human missions. Existing solutions do not scale. Without >10T landing, we have no Mars ascent vehicle, we have no ability to return to Earth, so we have no program. This is a serious issue! Entry, descent, and landing is composed of 3 parts. The entry part is where a heat shield is used to slow down from 5.7km/s, which is escape velocity, to terminal velocity, which is around 500m/s or Mach 2. This procedure burns off more than 99% of the kinetic energy, and the limiting factor is that Mars' atmosphere is really thin. The ballistic coefficient is a measure of surface density, or 'thickness', defined as the mass divided by the heat shield surface area. For all successful landers, it has been very very low, between 60 and 150kg/m^2. If we imagine a heatshield as big as the biggest payload fairing we can imagine, maybe 11m diameter, then we have a vehicle on the surface of perhaps 11T, which is really too low. This methodology, a gigantic flat flying saucer, has no headroom. Blunt bodies do not scale to 10T-100T range - there is simply not enough atmosphere to slow you down before you hit some tall mountain. There have been a few attempts (ADEPT, LDSD) to increase the size of the heat shield, but they are marginal, structurally problematic, relatively unguided, and have poor scaling characteristics. We need a new approach to entry. Bi/triconic hypersonic lifting bodies are, in my opinion, our best hope.

The good news is that landing, under subsonic propulsion, does scale extremely well. But there is still the descent problem. At 500m/s, the vehicle is still supersonic, which complicates propulsion. Heritage solutions use a gigantic supersonic parachute originally developed for Viking. The key issue is that parachutes also don't scale. They don't scale on mass, on timeline, or peak structural loads. On mass, it's pretty clear that the shroud cross section scales with vehicle mass, as does the canopy area, so the mass has to scale at least as vehicle mass to the 1.5. For 10T-100T payloads, we're talking a parachute the size of a stadium, since the Kerbal approach doesn't work where parachutes are made of fermions that obey the Pauli exclusion principle. A parachute of this size, mass aside, can't inflate fast enough to catch the vehicle before it makes a rather small but deeply unfortunately crater. And last, even if these scaling arguments were acceptable, all of LDSD's parachutes, at only 26m diameter still broke, for reasons we do not fully understand. There are potential solutions, SpaceX seems to be serious about supersonic retropropulsion, but nothing that's understood for certain, and it does our movement no favours to pretend that every problem, including these problems, are trivial.
The second major unsolved engineering issue to cover is Earth return. Of the three phases of a crewed exploration mission, outbound, surface, and return, return is by far the hardest. Deep space life support, razor thin margins, tiny mass allowances, long term machine reliability, completely unsupported launch ops, no indigenous industrial capacity whatever. Broadly speaking, there are two potential Earth return architectures. One is a tiny, even LESS-sized vehicle to fly to Mars orbit and rendezvous with a vehicle big enough to contain humans for 6 months to get home, which has to carry a lot of fuel and generally be a battlestar galactica. The other approach is direct Earth return from the surface of Mars. While on the one hand you need a much larger vehicle, you can't get away from 30T landings anyway. So you have to solve the EDL problem. And on the plus side you don't have some orbiting autonomous platform, orbital rendezvous, and Mars is the easiest place to get return fuel, by far. That said, even in Mars Direct, the Earth return vehicle (ERV) architecture is not explicitly sketched out, though clearly the vehicle is a lot smaller and the margins a lot tighter than the outbound voyage. On the plus side, it may be just possible to fly back from Mars with a single stage, which greatly simplifies vehicle architecture.

There remains a substantial credibility gap in crewed Mars exploration, but I hope I've sketched a set of ideas for improving the discourse going forward, both on a public and internal messaging level. I've been writing a (free!) book on these and other as-yet-unsolved crewed Mars mission engineering challenges and I encourage you to read it, leave comments and questions, and help us get specific! It can be found at .