Elon Musk wants to build a “self-sustaining city” on Mars. Experts aren't convinced

Would you board a spaceship built by this man? Elon Musk last week. Image: Getty.

Elon Musk, the founder of SpaceX and Tesla, has released new details of his vision to colonise parts of the solar system, including Mars, Jupiter’s moon Europa and Saturn’s moon Enceladus. His gung ho plans – designed to make humans a multi-planetary species in case civilisation collapses – include launching flights to Mars as early as 2023.

The details, just published in the journal New Space, are certainly ambitious. But are they realistic? As someone who works on solar system exploration, and the European Space Agency’s new Mars rover in particular, I find them incredible in several ways.

First of all, let’s not dismiss Musk as a Silicon Valley daydreamer. He has had tremendous success with rocket launches to space already. His paper proposes several interesting ways of trying to get to Mars and beyond – and he aims to build a “self-sustaining city” on the red planet.

Musk outlining initial plans in 2016.

The idea depends on getting cheaper access to space – the paper says the cost of trips to Mars must be lowered by “five million per cent”. An important part of this will be reusable space technology. This is an excellent idea that Musk is already putting into practice with impressive landings of rocket stages back on Earth – undoubtedly a huge technological step.

Making fuel on Mars and stations beyond it is something he also proposes, to make the costs feasible. Experiments towards this are underway, demonstrating that choosing the right propellant is key. The MOXIE experiment on the NASA 2020 rover will investigate whether we can produce oxygen from atmospheric CO2 on Mars. This may be possible. But Musk would like to make methane as well – it would be cheaper and more reusable. This is a tricky reaction which requires a lot of energy.

Yet, so far, it’s all fairly doable. But the plans then get more and more incredible. Musk wants to launch enormous spaceships into orbit around Earth where they will be refuelled several times using boosters launched from the ground while waiting to head to Mars. Each will be designed to take 100 people and Musk wants to launch 1,000 such ships in the space of 40 to 100 years, enabling a million people to leave Earth.

There would also be interplanetary fuel-filling stations on bodies such as Enceladus, Europa and even Saturn’s moon Titan, where there may have been, or may still be, life. Fuel would be produced and stored on these moons. The aim of these would be to enable us to travel deeper into space to places such as the Kuiper belt and the Oort cloud.

The “Red Dragon” capsule is proposed as a potential lander on such missions, using propulsion in combination with other technology rather than parachutes as most Mars missions do. Musk plans to test such a landing on Mars in 2020 with an unmanned mission. But it’s unclear whether it’s doable and the fuel requirements are huge.

Pie in the sky?

There are three hugely important things that Musk misses or dismisses in the paper. Missions such as the ExoMars 2020 rover – and plans to return samples to Earth – will search for signs of life on Mars. And we must await the results before potentially contaminating Mars with humans and their waste. Planetary bodies are covered by “planetary protection” rules to avoid contamination and it’s important for science that all future missions follow them.

Musk inspecting a heat shield at the SpaceX factory. Image: Steve Jurvetson/Flickr/creative commons.

Another problem is that Musk dismisses one of the main technical challenges of being on the Martian surface: the temperature. In just two sentences he concludes:

It is a little cold, but we can warm it up. It has a very helpful atmosphere, which, being primarily CO2 with some nitrogen and argon and a few other trace elements, means that we can grow plants on Mars just by compressing the atmosphere.

In reality, the temperature on Mars drops from about 0°C during the day to nearly -120°C at night. Operating in such low temperatures is already extremely difficult for small landers and rovers. In fact, it is an issue that has been solved with heaters in the design for the 300kg ExoMars 2020 rover – but the amount of power required would likely be a show-stopper for a “self-sustaining city”.

Musk doesn’t give any details for how to warm the planet up or compress the atmosphere – each of which are enormous engineering challenges. Previously, science fiction writers have suggested “terraforming” – possibly involving melting its icecaps. This is not only changing the environment forever but would also be challenging in that there is no magnetic field on Mars to help retain the new atmosphere that such manipulation would create. Mars has been losing its atmosphere gradually for 3.8bn years – which means it would be hard to keep any such warmed-up atmosphere from escaping into space.

The final major problem is that there is no mention of radiation beyond Earth’s magnetic cocoon. The journey to and life on Mars would be vulnerable to potentially fatal cosmic rays from our galaxy and from solar flares. Forecasting for solar flares is in its infancy. With current shielding technology, just a round-trip manned mission to Mars would expose the astronauts to up to four times the advised career limits for astronauts of radiation. It could also harm unmanned spacecraft. Work is underway on predicting space weather and developing better shielding. This would mitigate some of the problems – but we are not there yet.

Europa. Image: NASA.

For missions further afield, there are also questions about temperature and radiation in using Europa and Enceladus as filling stations – with no proper engineering studies assessing them. These moons are bathed in the strongest radiation belts in the solar system. What’s more, I’d question whether it is helpful to see these exciting scientific targets, arguably even more likely than Mars to host current life, as “propellant depots”.

The plans for going further to the Kuiper belt and Oort cloud with humans is firmly in the science fiction arena – it is simply too far and we have no infrastructure. In fact, if Musk really wants to create a new home for humans, the moon may be his best bet – it’s closer after all, which would make it much cheaper.

The ConversationThat said, aiming high usually means we will achieve something – and Musk’s latest plans may help pave the way for later exploration.

Andrew Coates is professor of physics and deputy director (solar system) at the Mullard Space Science Laboratory, UCL.

This article was originally published on The Conversation. Read the original article.


Why doesn’t London build an RER network, like Paris did?

A commuter walking by a map of the RER B line at the Chatelet-Les Halles station in Paris. Image: Getty.

I’ve heard many people make many different complaints about the Parisian transport system. That it does a bad job of linking a rich, white city with its poorer, more diverse suburbs. That, even as subway systems go, it’s a hostile environment for women. That the whole thing smells distractingly of urine.

I’m familiar with all of these complaints – I’ve often smelt the urine. And I’m aware that, in many ways, London’s is the superior transport network.

And yet I can’t help be jealous of Paris – In large part, because of the RER.

Central Paris. The Metro lines are thinner, and in pastel shades; the RER lines are thicker, and in brighter colours. Image: RATP.

Paris, you see, has not one but two underground railway systems. The more famous one is the original Paris Metro, opened in 1900: that’s the one with those fancy green portals with the word “metropolitain” written above them in a vaguely kooky font.

The Metro, though, mostly serves Paris Intra-muros: the official city, inside the Boulevard Périphérique ring road, site of the city’s last set of walls. As a result, it’s of very little use in most of the city’s suburbs. Its stations are very close together, which places a limit on how fast its trains can cross town. It was also, by the mid 20th century, becoming annoyingly overcrowded.

So starting in the 1960s, the city transport authorities began planning a second underground railway network. The Réseau Express Régional – Regional Express Network – would link suburban lines on either side of Paris, through new heavy rail tunnels beneath the city. Its stations would be much further apart than those of the metro – roughly one every 3km, rather than every 600m – so its trains can run faster.

And fifty years and five lines later, it means that 224 stations in the suburbs of Paris are served by trains which, rather than terminating on the edge of the city, now continue directly through tunnels to its centre.

The RER network today. Image: RATP.

London is, belatedly, doing something similar. The Elizabeth Line, due to open in stages from later this year, will offer express-tube style services linking the suburban lines which run west from Paddington to those which run east from Liverpool Street. And Thameslink has offered cross-town services for 30 years now (albeit not at tube-level frequencies). That, too, is going to add more routes to its network over the next few years, meaning direct trains from the southern suburbs to north London and vice versa.

Yet the vast majority of suburban National Rail services in London still terminate at big mainline stations, most of which are on the edge of the centre. For many journeys, especially from the south of the city, you still need to change to the London Underground.

So, could London ape Paris – and make Thameslink and Crossrail the first element of its own RER network?

In a limited way, of course, it’s doing just that. The next big project after Crossrail is likely to be (original name, this) Crossrail 2. If that gets funding, it’ll be a new south-west to north-east route, connecting some of the suburban lines into Waterloo to those in the Lea Valley.

The proposed route of Crossrail 2. Click to expand.

But it’s not immediately obvious where you could go next – what Crossails 3, 4 or 5 should cover.

That’s because there’s an imbalance in the distribution of the remaining mainline rail services in London. Anyone who’s even remotely familiar with the geography of the city will know that there are far more tube lines to its north. But the corollary of that is that there are far more mainlines to the south.

To usefully absorb some of those, Crossrail 3 would probably need to run south to south in some way. There is actually an obvious way of doing this: build a new tunnel from roughly Battersea to roughly Bermondsey, and take over the Richmond lines in the west and North Kent lines in the east, as a sort of London equivalent of RER C:

Our suggestion for Crossrail 3. Image: Google Maps/CityMetric.

But that still leaves a whole load of lines in south and south east London with nowhere to send them beyond their current terminal stations.

In fact, there are reasons for thinking that the whole RER concept doesn’t really fit the British capital. It was designed, remember, for a city in which the Metro only served the centre (roughly equivalent of London’s zones 1 & 2).

But London Underground wasn’t like that. From very early in its history, it served outer London too: it was not just a way of getting people around the centre, but for getting them there from their suburban homes too.

This is turn is at least in part a function of the economic geography of the two cities. Rich Parisians have generally wanted to live in the centre, pushing poorer people out to the banlieues. In London, though, the suburbs were where the good life was to be found.

To that end, the original operators of some lines weren’t just railway companies, but housing developers, too. The Metropolitan Railway effectively built large chunks of north west London (“Metroland”), partly to guarantee the market for its trains, but partly too because, well, housing is profitable.

In other parts of town, existing main line railways were simply added to the new underground lines. The Central line swallowed routes originally built by the Great Western Railway and London & North Eastern Railway. The District line absorbed part of the London, Tilbury & Southend Railway.

At any rate: the Tube was playing the same role as the RER as early as the 1930s. London could still benefit from some RER-type services, so hopefully the Elizbaeth Line won’t be the last. But it doesn’t need an entire second metro network in the way 1960s Paris did.

There is another idea we could more profitably steal from Paris. Those suburban railways which aren’t connected to the RER are still run by the national rail operator, SNCF. But it uses the Transilien brand name, to mark them out as a part of the Parisian transport network, and – as with the RER – each route has its own letter and its own colour.

The Transilien & RER networks in Paris. Image: Maximilian Dörrbecker/Wikimedia Commons.

This would not have the transformative effect on London that building another half a dozen Crossrails would. But it would make the network much easier to navigate, and would be almost infinitely cheaper. Perhaps we should be starting there.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites

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