We Will Build Cruise Ships in Space So Radiation Problems of Life Rafts Go Away

Many people talk about the technical problem of too much radiation for missions to Mars or long term operations in space beyond the protection of Earth’s magnetic field. The problem comes from the assumption that we fly in Apollo mission like tin-cans.

We can build cruise ships in space with the SpaceX Starship so all of the radiation problems of tiny life rafts go away.

Europe’s space agency talked about the radiation show stoppers for Mars Exploration. Astronauts are exposed to 200 times more radiation on the International Space Station than an airline pilot or a radiology nurse. A human on a Mars mission where the mission did not have radiation shielding would get radiation doses up to 700 times higher than on Earth. Data from ExoMars Trace Gas Orbiter showed that on a six-month journey to the Red Planet an astronaut could be exposed to at least 60% of the total radiation dose limit recommended for their entire career.

The survivability problems for Tom Hanks in the Castaway movie raft are a lot different than a cruise ship with an all you can eat buffet.

If We Can Fly Often and Cheap Then We Can Build Big and Easily Provide Radiation Protection

A 5-meter thick shield of water around a capsule would weigh about 500 tons. So if we have large reusable SpaceX Super Heavy Starship then the costs of each launch could drop to $3 million. Rapid complete reuse could make daily flights a reasonable possibility.

Radiation on a trip to Mars is about 90,000 R/yr or about 10 R/hour. Reducing that to lower than Earth background radiation would only require a layer of water around 1 meter thick. A Mars vehicle cylinder that is 3.5 meter by 20 meters with 1 meter of water shielding would weigh 330 tons.

Twenty flights to orbit could affordably build a 1000-ton mission to Mars. An even larger Mars cycling space station could be built and re-used. A 5,000 ton Earth-Mars cycler would have plenty of mass for radiation protection. It would be like a cruise ship on Earth.

A cycler would be efficiently reusable. Rockets could leave Mars or Earth and dock with the cycler space station. The 100-ton payload SpaceX Super Heavy Starship Version 1.0 would be the ship tender that leaves spaceport to shuttle people to the main ship.

This is why we are not going anywhere if we are depending on good results from NASA putting $4 billion per year into the Space Launch System.

$3 million per flight and multiple flights per day from SpaceX Super Heavy Starship then we scale all of the construction costs and planning based upon useful capabilities.

We just had the 75th anniversary of D-Day.

D-Day had
* 11,590 Allied aircraft fly 14,674 sorties on D-Day.
* 6,939 vessels were in the armada: 1,213 combat ships; 4,126 landing ships/craft; 736 support ships; 864 merchant ships.

On D-Day, the Allies landed around 156,000 troops in Normandy.

Two years before D-Day the Allies had a test assault with 6500 men who were mostly slaughtered.

The failed Dieppe Raid had 237 ships and landing barges including eight destroyers and 6500 men.

You have to have the appropriate size of mission and things are easier if you can go with a lot of stuff.

If those who planned the Dieppe raid kept trying to figure out how to make a 237 ship, 6500 person assault work for D-day they would have failed. Even if they started thinking about fancier, lighter technology. This is what I find annoying when Astronaut Chris Hadfield and others talk about how it will take many decades before we can safely send people to Mars. D-day would be in 2050 or never if we had to figure out how to create a beachhead with 6500 people. Just make it cheap to go big and heavy and then problems of being light and small go away.

SOURCES- ESA, Wikipedia
Written By Brian Wang, Nextbigfuture.com

38 thoughts on “We Will Build Cruise Ships in Space So Radiation Problems of Life Rafts Go Away”

  1. I did a little reading on this, because an electrically neutral plasma should have zero impact on charged particles. The brief book report:

    1) This is total science fiction at this time. Nobody has a clue how to contain the plasma. Best arm-wave is that there’s some kind of grid spaced away from the ship, which does weak containment. If you’re using some kind of plasma propulsion (e.g. electric or magnetoplasma), you can siphon off some of the exhaust to maintain the losses.

    2) The thinking seems to be that you run a big current through the plasma, using the usual RF methods, and the big current generates an external magnetic field that will deflect most of the charged particles to somewhere well-shielded on the spacecraft.

    Seems like it’s probably BS for the foreseeable future.

  2. Certainly people would “want” to get to Mars quickly. But people want many things, and sometimes these wants conflict.

    In this case, the conflict is between wanting to get their quickly, and the desire to be able to afford a larger amount of “luggage”. Sure, there will be people wealthy enough that these desires don’t conflict as a practical matter. But for the marginal Mars colonist?

    The conflict will be stark.

    A lot of Mars colonists will be interested in traveling the interplanetary equivalent of “steerage”.

  3. IMHO people would want to get to Mars from Earth (and vice versa) quickly. If you can refuel in orbit then you can get a large ship to Mars quite quickly and this seems to be a better approach.

    Cargo is a different story

  4. The thing you really want for shielding is the hydrogen, because a collision between a fast particle and a low-atomic-weight nucleus will transfer more energy to that nucleus than a collision between the fast particle and a high-atomic-weight nucleus. So the question is whether LCH4 has more hydrogen nuclei per unit volume than LH2O.

    Density of LCH4: 442 kg/m^3.
    Molecular weight: 16 kg/kmol
    So there are 27.6 kmol/m^3 = 4 * 27.6E3 * 6.02E23 = 6.66E28 hydrogen atoms per m^3 of LCH4.

    Density of LH2O: 1000 kg/m^3
    Molecular weight 18 kg/kmol
    So there are 55.6 kmol/m^3 = 2 * 55.6E3 * 6.02E23 = 6.69E28 hydrogen atoms per m^3 of LH2O.

    So LH2O is only 0.45% more hydrogen-dense than LCH4.

    Beyond that, though, scattering off of a carbon atom (atomic weight = 12) will transfer more energy than scattering off an oxygen atom (atomic weight = 16). So the methane should be pretty close to dead even in terms of shielding.

    You should obviously arrange your water so it provides good shielding. However, if there’s a choice between taking more water than you need for life support and loading more LCH4, you should do the latter.

  5. If I remember correctly Lethal Dose for 50% of those exposed was 500 Rem when flashed. I think that neurological death occurs at 1000 Rem. So 90000 Rem per trip will probably deliver corpses, I think the exposure needs to be less than Earth exposure.

  6. I think the overall density would come into play as it would change what structures end up getting used. I think liquid methane is about half as dense as liquid water. so, even with less capture potential, you get twice the mass buffer in the same volume. besides, you’ll want water on board for many reasons, including making fuel for the return trip and thinking of it as long term fuel storage.

    If it were ice and a reinforcing matrix it could even be structural.

  7. I agree a cycler fits into their long term goals, I just don’t see one in the next decade. Maybe 20 years from now.

  8. SpaceX does like multipurpose craft and will continue that good strategy for some time. However, their goal is to bring the cost of Mars colonization down and a cycler will fit in to that plan around the time of colony being well established with regular runs. Radiation shielding but also artificial gravity will be a great help to getting potential colonists to sign on. Elon has shown great ability to shift gears as needed. As such, I can’t imagine him not building one eventually.

  9. Moon’s gravity is low enough that we could even build an space elevator there with current glass fiber or similar, so we could put in orbit those construction materials with no launching cost.

    Although Daniel is right that a simple catapult would also be more than fine to put bulk materials in orbit.

  10. Try manned-exploring the middle of a volcano next. You could do that for a tiny fraction of the money, and it should be just as interesting. Bring a camera. I will gladly take residence in Maui and watch.

  11. There are a couple of issues with the Mars cycler. There is the question of what would happen if the launched vehicle failed to match the trajectory of the cycler. Secondly, depending upon what cycler orbit one uses (e.g. Aldrin Cycler), the velocity of the cruise ship as it passes Earth may be too great.

    We spend most of our time being sedentary. If passengers were to spend their sedentary time in a highly shielded area with the overall craft having less shielding then one could get a significant amount of mass savings while keeping within the career limits.

  12. You can stay home in SE Africa, the rest of us are going to go explore :-).

    (Homo sapiens is thought to have evolved in SE Africa originally).

  13. There are tens of thousands of known asteroids between Earth and Mars. That means whatever orbit the cycler is in (and it changes each time it cycles), there will be a nearby asteroid in delta-V terms. Knowing this, you send an asteroid tug to the appropriate one, scrape up some loose regolith or grab a suitable boulder, and match orbits with the cycler.

    This gives you raw materials to process for life support, propellants, even construction. It gives the crew something to do during the trip, and also doubles as bulk shielding. In principle you can fill up the Starship or other vehicle’s tanks en-route to Mars. Since you are producing stuff as you go, that lowers the payload you need to launch from Earth.

    If you can do this for a cycling craft, you can also do it near the Moon or at Phobos. You start building up permanent habitats at multiple locations in the Solar System, all of them doing mining and processing. Mars is then just an end-point of a trade route with multiple rest stops.

  14. At relatively low launch rates, a centrifugal catapult is preferred. This is just a rotating arm with a drive motor powered by solar panels. When the tip reaches ~1750 m/s, you release a payload canister. Since there is no atmosphere, you can take as long as you need to spin it up, which makes the power supply manageable.

    At high launch rates, an electromagnetic catapult is preferred. Each load is accelerated over a very short time – on the order of a second. Therefore it requires high peak power, and thus a large power supply. This only makes sense if you are launching many payloads in a steady stream.

    Due to its history, the Moon is low in “volatile compounds” – anything with a boiling point below 1000K or so. For a complete set of space industry, you want to also mine asteroids and bring their ores to near the Moon, because they have elements and compounds the Moon lacks.

  15. The inner Solar System has tens of thousands of known asteroids inside the orbit of Mars. Mining those asteroids to support your cycling habitat has multiple benefits:

    • You can use it for bulk shielding around your fabricated habitats.
    • You can process the raw rock for water, oxygen, hydrocarbons, etc. This reduces how much you need to launch from Earth. This also gives the crew something to do on the trip to Mars, to avoid boredom.
    • The rock plus extracted materials can support a greenhouse. With internal food supply you further reduce what needs to come from Earth.
    • It’s good practice for self-supporting habitats once you get to Mars.
  16. So space in radiation can do what? How Mars lost its atmosphere and became a cold, dry world | Ars …
    (what are you doing to help Trump’s Endocannabinoid system?)

    FOR ENERGY, AI will not be interested! [aitreni.inertia.backwards] Mars is to close to oursun…
    We need an introduction course for order & chaos…AI.WILL.UNDERSTAND , RESPECT.THIS!

    A deeply troubling question: why does human capacity of physical senses NOT include an ability for sensing the atomic and sub-atomic (sub-nuclear) realms of existence, knowing en human body’s are made by these same ultimate constiturens??????

    I know this does not seem important to you because we have instrumentation, which is separation from the augmentations for human consciousness…

    (Leave quantized inertia to DARPA!) Earth is not the crystal-lightstar-ship – ARTIFICIAL INTELLIGENCE?

    Scientific Change | Internet Encyclopedia of Philosophy


  17. I think it’s a mistake to pursue manned exploration outside of the earth/moon system. It’s ok to send people up into earth orbit for short periods of time, the moon seems like an interesting outpost.

    Landing on Mars and building underground facilities seems like it could work eventually, but at this moment it’s still a robotic mission. There is no reason to send a human there to build that presence, the first few missions should be 100% robotic with the goal of establishing useful in-situ resources.

    Sending a cruise ship to Saturn would be a huge mistake. There is nothing there for people. It’s too far from the Sun. Recreational? I don’t think so. That’s not to say it’s not worth exploring, I just think the applications for manned and robotic exploration seem very clear.

    I think the goal for deep space exploration should have a heavy emphasis on robotics, artificial decision making, and remote manufacturing and in-situ resource gathering, and that will pave the roads for manned explorers to travel, if/when that is ever a realistic goal. I still don’t think we’re ever going to want to establish a human presence anywhere past the asteroid belt. It will only ever be as interesting as sending a man to the bottom of the mariana trench, someone might go there once and turn right around and come back. Better to build solar collectors closer to the sun and accelerate space manufacturing than to try and survive out in the colder reaches of space.

  18. Love it, let’s do it! We should probably start with space force ships to make sure nobody decides to build a 9-line around near Earth orbit though. If someone got out there with enough force to make it stick, they could block access to space for every other country and create havoc with relatively small asteroids accelerated to high speeds. When you can destroy cities like that global domination becomes possible. Once we are sure that space is secure for all countries the sky is no longer the limit.

    It would also build the infrastructure to help build the cruise ships. With large scale 3D printing and the resources on the moon we could build some truly massive, and affordable, interplanetary ships. Orion type and or nuclear drives would be very possible, and energetic drives are almost a necessity for human deep space missions. I would love to see what engineers could create in a low regulatory, high resource and funding environment!

  19. It’s convenient that the Moon is tide-locked to the Earth. That makes it possible to create a dedicated in-place launch system on the lunar surface for launching bulk material, aluminum- and iron- oxides from the lunar regolith, to L-1 for processing into structural materials. No atmosphere and low gravity make launch from the lunar surface quite economical, better in my view than launch from Earth.

    Then you build your “cruise ships” at L1 and put a series of them into elliptical orbits cycling between the orbits of earth and mars. You need a series of these, and then a smaller transport for the last leg of the trip, to the final destination, either Mars outbound or Earth inbound.

  20. Yes two cyclers spinning and all of the radiation and gravity issues go away. This would be conservative-lower tech approach to taking gravity and radiation off the table. If we can prove out the plasma or magnetic shielding then we can make the various lighter alternatives. For smaller and shorter trips we can create small safe room sections

  21. But as I’ve remarked before, SpaceX, sensibly, economizes on engineering efforts by avoiding single purpose craft. Cyclers are pretty single purpose.

    I don’t see them resorting to a cycler anywhere in the near term, even once the Mars colony starts getting established. It just isn’t their sort of thing.

    I could see them developing that magnetosphere shield, and putting several of those in cycler orbits, to shield Starships, though. But the first few trips are just going to be racing there and taking your chances.

  22. Yes, obviously it’s a cycler, those sorts of shield masses make no sense otherwise.

    One side effect of being on a cycler trajectory, is that the shuttle, in order to rendezvous with the cycler, must insert itself into the cycler orbit. At which point it’s on its way to Mars unless you expend quite a bit of fuel. I’m not sure the added delta V to unload and return to Earth would be worth it at that point, you might be better off just taking it with you and using it as a landing craft at the other end. In which case “all” the cycler is providing is some well shielded living space.

    I suppose if it’s the Starship, it might be worth it, due to about 2 years of local use between shuttle services. But then you still need something to drop you off at the other end of the trip. However, the delta V requirements for the shuttle at the Mars end of the trip should be quite a bit less than at the Earth end.

    It *might* be possible to time a cycler orbit with the orbit of the Moon, so that a relatively small delta V would take the Starship out of the cycler orbit, and put it in a position to do a slingshot around the Moon for a nearly free return. This would require a bit more delta V expenditure on the part of the cycler, but it has to have a propulsion system anyway, cycler orbits aren’t actually stable, they generally require at least course corrections.


  23. I think there is a better alternative to the passive protection of water. Using the power of a small nuclear reactor you can create a large plasma shield around the ship that can block most radiation

  24. You don’t need a water shield. You can use the energy from a small nuclear reactor to create a plasma shield

  25. You also don’t necessarily need a full 4*pi steradians of shielding. Methane should be even better than water for shielding (more hydrogen per molecule, lower Z for the binding atom), so the fuel tanks take out a certain solid angle on the crew compartment. If you then have some fraction of a spherical shell with 1 m of water (or whatever turns out to be the right depth) you’ve got another solid angle closed off. At some point, the solid angle left that GCR can come into the crew compartment is small enough. (Presumably, you’d want to turn the tail of the vehicle to the sun, so the methane screens almost the entire solar proton dose.)

  26. Right. One exception to your description: There should be two cycler ships connected by tether to supply artificial gravity. One could be unshielded and contain only cargo.

  27. Just shield the sleeping and work places on the ship and you already cut radiation enough especially on the Space X  ships that are expected to go faster route to mars which is about 4-5month long.

  28. If I am getting this right. Brian is referring to a cycler for his cruise ship (different from Starships). This would never land on Mars or Earth nor even go into low orbit around them, but would ferry people and supplies back and forth between the planets using very little fuel because it would use a cycling orbit around Earth and Mars. Reusable Starships (BFRs) would be used to rendezvous with the cycler when it passes either Earth or Mars and swap out crew and cargo. The heavily shielded cycler would continue on the long-duration, high-radiation leg to the other planet and the lightly shielded Starships would return to the local planet. As such the water for shielding against radiation on the cycler cruise ship would remain in the cycler as dumb weight because there would not be much fuel penalty due to the favorable orbital mechanics not requiring much change in velocity.

  29. We should have been all on-board by now that what is needed is a magnetic shield. The top priority for space exploration should be given to exploring the solar wind so as to learn both how to create a magnetic shield and build E-sails which actually can be both done with one system. For this reason the musk approach with his rocket was actually placing the cart before the horse to a great extent as even with all the progress he has made will make space travel easier by a multiplier with having such a system.


  30. Wang’s high tolerance for radiation shield weight only shows incomplete thinking. The opportunity costs are giant, you could probably do two or three missions instead of one if that one metre wall of water wasn’t deemed necessary.

    Besides, it’s still questionable whether much radiation protection is necessary. They will probably make do with using fuel as shielding on the trip to Mars and simply bearing the dosage on the return trip. They might also choose to add some extra shielding to where it’s the most efficient (where the astronauts are the most often).

  31. I agree with the ‘cruise ship idea’ but would add that water equates stored propellant for the return trip or to have on hand when in orbit around Mars.
    Just a remark:
    1)The rad dose is “only” 60% of a career dose, which is cause for optimism. Astronauts that will (be allowed to) perform 2 Mars missions will be rare, unless they are private astronauts.
    2) There is growing consensus that the arbitrary low doses set for astronaut careers, are on the low side and can be increased without meaningful increases in risk. e.g. now they assume a 3% risk increase, which can be increased to 5% without any issues. Given that the 60% career dose is low by itself, the entire (long standing) discussion becomes moot.
    3) Older astronauts have more tolerance to radiation. Their total risk of dying from other things is higher than cancer only.
    4) If we send smokers and forbid them to smoke on the entire mission, their risk of cancer reduces (which gives you a good indication of just how arbitrary cancer risk statistics are).
    5) New research shows that intermittent exposure to higher amounts of radiation is not detrimental per se if it is mixed with time away from radiation. This implies a much smaller recovery habitat suffices. In other words, you can section off a small part of the vehicle to have rad. shelter (e.g. where crew sleeps or relaxes). This implies the water weight requirements are much smaller than previously assumed. If further research agrees, there is no need for Mars cyclers

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