The Occupy Mars Learning Adventure

Training Jr. Astronauts, Scientists & Engineers

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Calling all Occupy Mars chemistry students

Toxic Mars dust could hamper planned human missions

Mission Report for Asa:  How can we help  with chemistry ideas for our fourth grader and the other Occupy Mars Learning Adventure astronauts in training?   We have one student that loves chemistry.

Don’t know if an oscilloscope is needed, but the pervasive fine red dust on Mars will contaminate everything with iron oxide.  Detecting and measuring iron in water would be a safe and inexpensive chemistry experiment.  Iron content might be an indicator of other contaminants in the Martian dust.  See for example


If a simple, lower-pressure (not vacuum) chamber could be built to simulate the Martian atmosphere, the pressure and temperature could be continuously displayed and logged as ice melted.  This dynamic experiment would invoke the gas laws and phase transitions (Physical Chemistry).  The concepts are mind-stretching, but the math is simple and amenable to visualization and analysis with both two and three-dimensional graphics.

John, Occupy Mars Physics Team.

Occupy Mars Physics Department.

By Victoria Jaggard in Washington DC

Mars dust is dangerous to human health and could severely hamper proposed missions to send people to the Red Planet. So say space-health and life-support researchers who met this week to mull over the possibility of sending a crewed mission to Mars by 2030.

Laboratory studies had suggested that Mars dust might be a health hazard because it contains fine-grained silicate minerals, which are common on Mars. If breathed in, the silicate dust would react with water in the lungs to create damaging chemicals.

Recent robotic missions suggest that the outlook for a crewed mission may be even worse. Delegates to the Humans 2 Mars Summit (H2M) in Washington DC, an effort to chart and overcome the challenges of getting humans to Mars within the next two decades, yesterday heard the latest evidence of the dangers of Martian dust.

Richard Williams, NASA’s chief health and medical officer, pointed out at the meeting that perchlorates, which are known to harm the thyroid gland, increasingly look to be widespread on Mars.


Baked for analysis

Perchlorates were first detected by NASA’s Phoenix lander in 2008 near the Martian north pole. More recently, there was a possible detection by NASA’s Curiosity rover, which landed in August 2012 and is now exploring Gale crater, near Mars’s equator. Last December, Curiosity’s Sample Analysis at Mars (SAM) instrument baked up a scoop of soil, taken from a site called Rocknest, to analyse the dust’s composition.

“We believe that there could be perchlorates in the Rocknest dust sample,” says Paul Mahaffy, principal investigator for SAM. “Since dust blows all over Mars, this certainly should be considered along with other human health impacts.”

That’s not all. In the past few months Curiosity has found veins of a mineral, most likely gypsum – and that is also worrisome, says Grant Anderson, co-founder of Paragon Space Development, a company based in Tucson, Arizona.

“Gypsum is not really toxic per se, but if you breathe it in you do start to see a build-up in the lungs that’s equivalent to the coal-dust lung experienced by miners. That leads to breakdowns in lung capacity,” says Anderson. The US National Institute for Occupational Safety and Health classifies gypsum dust as a nuisance particulate that can irritate the eyes, skin and respiratory system, and sets recommended exposure limits.

Sticky nuisance

But with limited atmospheric oxygen as well as dangerous radiation to contend with, astronauts on Mars won’t be going out and breathing in dust directly. They will have to remain inside special habitats, donning spacesuits if they venture out. So could this dangerous stuff still wend its way into their bodies?

The problem starts with the spacesuits, which Martian dust will stick to persistently, says Anderson. “That’s one thing they learned from the Apollo missions on the moon,” he adds.

Those missions showed that lunar soil has been ground into fine, sharp-edged grains that cling to just about everything, thanks to bombardment from micrometeorites and charged particles from the sun. Although Martian dust has been somewhat protected by a thin atmosphere, it has been blowing around for 3.5 billion years, and that has worn down the particles into very small, round grains. The grains aren’t sharp, but constant roiling around the planet has probably given Mars dust a significant static charge, says Anderson, which could make it sticky.

The fear is that since the dust cannot easily be cleaned from suits, it will get into astronauts’ living quarters, even if they return via an airlock – an intermediate space between their quarters and the low-pressure, CO2-rich environment of Mars. “What you’re going to want to do is pump out the CO2 and then let in air,” explains Anderson. “That creates eddy currents, which creates flow. You’ve got such fine dust on Mars that you won’t be able to keep it down, and the person will be breathing it in.”

Robotic answers

Dust wafting inside the astronauts’ quarters might also clog air filters, water purifiers and other critical instruments, warned Greg Gentry, an engineer at Boeing in Houston, Texas, and the technical lead for the Environmental Control and Life Support System on the International Space Station. But for now no one really knows how Mars dust will affect the equipment people will need to survive on the planet. “Dust is a problem because no one knows what it is going to do on Mars,” says Anderson.

The good news is that robotic missions such as Curiosity could help provide vital answers. “The Apollo programme spent $17 million trying to solve their lunar dust problems, and I’m not sure they made much progress, because they had to do the tests on Earth,” says Anderson. “For Mars, the precursor robotic missions should all have some way to test how dust is going to kill you.”

So far, such practical concerns have done little to curb enthusiasm for a human Mars mission. Two weeks ago, the private Mars One venture started taking applications for its one-way trip to the Red Planet. On 7 May, the company announced that it has received 78,000 applicants, and counting. “This is turning out to be the most desired job in history,” Mars One co-founder Bas Lansdorp said in a statement.

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Colonizing Mars Reading Assignment

Online STEAM++ Reading Assignments:  Your mission is to read this article by Dr. Robert Zubrin.  You will have an opportunity to join in on the discussion.  Send your feedback to


Elon Musk debuting the ITS plans

Colonizing Mars


A Critique of the SpaceX Interplanetary Transport System

Robert Zubrin

In remarks at the International Astronautical Congress in Guadalajara, Mexico on September 29, 2016, SpaceX founder and CEO Elon Musk revealed to great fanfare his company’s plans for an Interplanetary Transport System (ITS). According to Musk, the ITS would enable the colonization of Mars by the rapid delivery of a million people in groups of a hundred passengers per flight, as well as large-scale human exploration missions to other bodies, such as Jupiter’s moon Europa.

I was among the thousands of people in the room (and many more watching live online) when Musk gave his remarkable presentation, and was struck by its many good and powerful ideas. However, Musk’s plan assembled some of those good ideas in an extremely suboptimal way, making the proposed system impractical. Still, with some corrections, a system using the core concepts Musk laid out could be made attractive — not just as an imaginative concept for the colonization of Mars, but as a means of meeting the nearer-at-hand challenge of enabling human expeditions to the planet.

In the following critique, I will explain the conceptual flaws of the new SpaceX plan, showing how they can be corrected to benefit, first, the near-term goal of initiating human exploration of the Red Planet, and then, with a cost-effective base-building and settlement program, the more distant goal of future Mars colonization.

Design of the SpaceX Interplanetary Transport System

As described by Musk, the SpaceX ITS would consist of a very large two-stage fully-reusable launch system, powered by methane/oxygen chemical bipropellant. The suborbital first stage would have four times the takeoff thrust of a Saturn V (the huge rocket that sent the Apollo missions to the Moon). The second stage, which reaches orbit, would have the thrust of a single Saturn V. Together, the two stages could deliver a maximum payload of 550 tons to low Earth orbit (LEO), about four times the capacity of the Saturn V. (Note: All of the “tons” referenced in this article are metric tons.)

At the top of the rocket, the spaceship itself — where some hundred passengers reside — is inseparable from the second stage. (Contrast this with, for example, NASA’s lunar missions, where each part of the system was discarded in turn until just the Command Module carried the Apollo astronauts back to Earth.) Since the second-stage-plus-spaceship will have used its fuel in getting to orbit, it would need to refuel in orbit, filling up with about 1,950 tons of propellant (which means that each launch carrying passengers would require four additional launches to deliver the necessary propellant). Once filled up, the spaceship can head to Mars.

The duration of the journey would of course depend on where Earth and Mars are in their orbits; the shortest one-way trip would be around 80 days, according to Musk’s presentation, and the longest would be around 150 days. (Musk stated that he thinks the architecture could be improved to reduce the trip to 60 or even 30 days.)

After landing on Mars and discharging its passengers, the ship would be refueled with methane/oxygen bipropellant made on the surface of Mars from Martian water and carbon dioxide, and then flown back to Earth orbit.

Problems with the Proposed System

The SpaceX plan as Musk described it contains nine notable features. If we examine each of these in turn, some of the strengths and weaknesses in the overall system will begin to present themselves.

1. Extremely large size. The proposed SpaceX launch system is four times bigger than a Saturn V rocket. This is a serious problem, because even with the company’s impressively low development costs, SpaceX has no prospect of being able to afford the very large investment — at least $10 billion — required to develop a launch vehicle of this scale.

2. Use of methane/oxygen bipropellant for takeoff from Earth, trans-Mars injection, and direct return to Earth from the Martian surface. These ideas go together, and are very strong. Methane/oxygen is, after hydrogen/oxygen, the highest-performing practical propellant combination, and it is much more compact and storable than hydrogen/oxygen. It is very cheap, and is the easiest propellant to make on Mars. For over a quarter century, I have been a strong advocate of this design approach, making it a central feature of the Mars Direct mission architecture I first laid out in 1990 and described in my book The Case for Mars. However, it should be noted that while the manufacture of methane/oxygen from Martian carbon dioxide and water is certainly feasible, it is not without cost in effort, power, and capital facilities, and so the transportation system should be designed to keep this burden on the Mars base within manageable bounds.

3. The large scale manufacture of methane/oxygen bipropellant on the Martian surface from indigenous materials. Here I offer the same praise and the same note of caution as above. The use of in situ (that is, on-site) Martian resources makes the entire SpaceX plan possible, just as it is a central feature of my Mars Direct plan. But the scale of the entire mission architecture must be balanced with the production capacity that can realistically be established.

4. All flight systems are completely reusable. This is an important goal for minimizing costs, and SpaceX is already making substantial advances toward it by demonstrating the return and reuse of the first stage of its Falcon 9 launch vehicle. However, for a mission component to be considered “reusable” it doesn’t necessarily need to be returned to Earth and launched again. In general, it can make more sense to find other ways to reuse components off Earth that are already in orbit or beyond. This idea is reflected in some parts of the new SpaceX plan — such as refilling the second stage in low Earth orbit — but, as we shall see, it is ignored elsewhere, at considerable cost to program effectiveness. Furthermore the rate at which systems can be reused must also be considered.

5. Refilling methane/oxygen propellant in the booster second stage in Earth orbit. Here Musk and his colleagues face a technical challenge, since transferring cryogenic fluids in zero gravity has never been done. The problem is that in zero gravity two-phase mixtures float around with gas and liquid mixed and scattered among each other, making it difficult to operate pumps, while the ultra-cold nature of cryogenic fluids precludes the use of flexible bladders to effect the fluid transfer. However, I believe this is a solvable problem — and one well worth solving, both for the benefits it offers this mission architecture and for different designs we may see in the future.

6. Use of the second stage to fly all the way to the Martian surface and back. This is a very bad idea. For one thing, it entails sending a 7-million-pound-force thrust engine, which would weigh about 60 tons, and its large and massive accompanying tankage all the way from low Earth orbit to the surface of Mars, and then sending them back, at great cost to mission payload and at great burden to Mars base-propellant production facilities. Furthermore, it means that this very large and expensive piece of capital equipment can be used only once every four years (since the feasible windows for trips to and from Mars occur about every two years).

7. The sending of a large habitat on a roundtrip from Earth to Mars and back. This, too, is a very bad idea, because the habitat will get to be used only one way, once every four years. If we are building a Mars base or colonizing Mars, any large habitat sent to the planet’s surface should stay there so the colonists can use it for living quarters. Going to great expense to send a habitat to Mars only to return it to Earth empty makes no sense. Mars needs houses.

8. Quick trips to Mars. If we accept the optimistic estimates that Musk offered during his presentation, the SpaceX system would be capable of 115-day (average) one-way trips from Earth to Mars, a somewhat faster journey than other proposed mission architectures. But the speedier trips impose a great cost on payload capability. And they raise the price tag, thereby undermining the architecture’s professed purpose — colonizing Mars — since the primary requirement for colonization is to reduce cost sufficiently to make emigration affordable. Let’s do some back-of-the-envelope calculations. Following the example of colonial America, let’s pick as the affordability criterion the property liquidation of a middle-class household, or seven years’ pay for a working man (say about $300,000 in today’s equivalent terms), a criterion with which Musk roughly concurs. Most middle-class householders would prefer to get to Mars in six months at the cost equivalent to one house instead of getting to Mars in four months at a cost equivalent to three houses. For immigrants, who will spend the rest of their lives on Mars, or even explorers who would spend 2.5 years on a round trip, the advantage of reaching Mars one-way in four months instead of six months is negligible — and if shaving off two months would require a reduction in payload, meaning fewer provisions could be brought along, then the faster trip would be downright undesirable. Furthermore, the six-month transit is actually safer, because it is also the trajectory that loops back to Earth exactly two years after departure, so the Earth will be there to meet it. And trajectories involving faster flights to Mars will necessarily loop further out into space if the landing on Mars is aborted, and thus take longer than two years to get back to Earth’s orbit, making the free-returnbackup abort trajectory impossible. The claim that the SpaceX plan would be capable of 60-day (let alone 30-day) one-way transits to Mars is not credible.

9. The use of supersonic retropropulsion to achieve landing on Mars. This is a breakthrough concept for landing large payloads, one that SpaceX has demonstrated successfully in landing the first stages of its Falcon 9 on Earth. Its feasibility for Mars has thus been demonstrated in principle. It should be noted, however, that SpaceX is now proposing to scale up the landing propulsion system by about a factor of 50 — and employing such a landing techniques adds to the propulsive requirement of the mission, making the (unnecessary) goal of quick trips even harder to achieve.

Improving the SpaceX ITS Plan

Taking the above points into consideration, some corrections for the flaws in the current ITS plan immediately suggest themselves:

A. Instead of hauling the massive second stage of the launch vehicle all the way to Mars, the spacecraft should separate from it just before Earth escape. In this case, instead of flying all the way to Mars and back over 2.5 years, the second stage would fly out only about as far as the Moon, and return to aerobrake into Earth orbit a week after departure. If the refilling process could be done expeditiously, say in a week, it might thus be possible to use the second stage five times every mission opportunity (assuming a launch window of about two months), instead of once every other mission opportunity. This would increase the net use of the second stage propulsion system by a factor of 10, allowing five payloads to be delivered to Mars every opportunity using only one such system, instead of the ten required by the ITS baseline design. Without the giant second stage, the spaceship would then perform the remaining propulsive maneuver to fly to and land on Mars.

B. Instead of sending the very large hundred-person habitat back to Earth after landing it on Mars, it would stay on Mars, where it could be repurposed as a Mars surface habitat — something that the settlers would surely find extremely useful. Its modest propulsive stage could be repurposed as a surface-to-surface long-range flight system, or scrapped to provide material to meet other needs of the people living on Mars. If the propulsive system must be sent back to Earth, it should return with only a small cabin for the pilots and such colonists as want to call it quits. Such a procedure would greatly increase the payload capability of the ITS system while reducing its propellant-production burden on the Mars base.

C. As a result of not sending the very large second stage propulsion system to the Martian surface and not sending the large habitat back from the Martian surface, the total payload available to send one-way to Mars is greatly increased while the propellant production requirements on Mars would be greatly reduced.

D. The notion of sacrificing payload to achieve one-way average transit times substantially below six months should be abandoned. However, if the goal of quick trips is retained, then the corrections specified above would make it much more feasible, greatly increasing payload and decreasing trip time compared to what is possible with the original approach.

Changing the plan in the ways described above would greatly improve the performance of the ITS. This is because the ITS in its original form is not designed to achieve the mission of inexpensively sending colonists and payloads to Mars. Rather, it is designed to achieve the science-fiction vision of the giant interplanetary spaceship. This is a fundamental mistake, although the temptation is understandable. (A similar visionary impulse influenced the design of NASA’s space shuttle, with significant disadvantage to its performance as an Earth-to-orbit payload delivery system.) The central requirement of human Mars missions is not to create or operate giant spaceships. Rather, it is to send payloads from Earth to Mars capable of supporting groups of people, and then to send back such payloads as are necessary.

To put it another way: The visionary goal might be to create spaceships, but the rational goal is to send payloads.

Alternative Versions of the SpaceX ITS Plan

To get a sense of some of the benefits that would come from making the changes I outlined above, let’s make some estimates. In the table below, I compare six versions of the ITS plan, half based on the visionary form that Elon Musk sketched out (called the “Original” or “O” design in the table) and half incorporating the alterations I have suggested (the “Revised” or “R” designs).

Our starting assumptions: The ship begins the mission in a circular low Earth orbit with an altitude of 350 kilometers and an associated orbital velocity of 7.7 kilometers per second (km/s). Escape velocity for such a ship would be 10.9 km/s, so applying a velocity change (DV) of 3 km/s would still keep it in a highly elliptical orbit bound to the Earth. Adding another 1.2 km/s would give its payload a perigee velocity of 12.1 km/s, sufficient to send it on a six-month trajectory to Mars, with a two-year free-return option to Earth. (In calculating trip times to Mars, we assume average mission opportunities. In practice some would reach Mars sooner, some later, depending on the launch year, but all would maintain the two-year free return.) We assume a further 1.3 km/s to be required for midcourse corrections and landing using supersonic retropropulsion. For direct return to Earth from the Martian surface, we assume a total velocity change of 6.6 km/s to be required. In all cases, an exhaust velocity of 3.74 km/s (that is, a specific impulse of 382 s) for the methane/oxygen propulsion, and a mass of 2 tons of habitat mass per passenger are assumed. A maximum booster second-stage tank capacity of 1,950 tons is assumed, in accordance with the design data in Musk’s presentation.

Table: Analysis of Alternative ITS Concepts
Concept A B C D E F
Type (O=“original”; R=“revised”) O O R O R R
Stage dry-mass fraction 0.08 0.08 0.08 0.12 0.12 0.12
One-way flight time (days) 130 180 180 180 180 180
Launcher 2nd stage ΔV (km/s) 7.0 5.5 3.0 5.5 3.0 3.0
Ship trans-Mars ΔV (km/s) 0.0 0.0 2.5 0.0 2.5 2.5
Trans-Earth ΔV (km/s) 6.6 6.6 6.6 6.6 6.6 6.6
Habitat mass round trip (t) 200 200 60 166 42 10
Habitat mass one-way to Mars (t) 0 0 200 0 200 20
Other cargo one-way to Mars (t) 0 210 190 174 208 20
Launcher 2nd-stage dry mass (t) 150 150 110 228 171 15
Launcher 2nd-stage propellant (t) 1,950 1,873 1,429 1,950 1,426    177
Ship stage dry mass (t) 0 0 36 0 58 13
Ship stage trans-Mars injection propellant (t) 0 0 462 0 482 60
Trans-Earth-injection (TEI) propellant (t) 1,574 1,574 465 1,900 482 114
Total useful mass delivered 0 210 390 174 408 40
Number of settlers delivered 100 100 100 83 100 5
Payload per settler (t) 0.0 2.1 3.9 2.1 4.1 8.0
Trans-Sys mass (5 missions/op) 1,500 1,500 470 2,280 751 145
Payload/Trans-Sys (5 missions) 0.00 0.70 4.14 0.38 2.72 1.38
Payload/TEI propellant 0.00 0.13 0.84 0.09 0.85 0.35

Concept A is the original ITS concept as presented by Musk, with a 130-day transit from Earth to Mars. The plan is technically feasible, but it has the downsides discussed above, including the glaring problem marked in red: no payload is delivered along with the people, leaving the colonists at Mars with no supplies or equipment or housing.

Concept B gives Musk’s original plan only a slight twist: the trip to Mars is longer — by fifty days — which means a lower DV is required for the journey, which in turn means (as marked in blue) that 210 tons of cargo can be delivered along with the colonists, for 2.1 tons of payload per colonist.

Concept C incorporates another of my suggested improvements from above, leaving the second stage of the launch vehicle near Earth. In such an arrangement, the second stage needs to do only 3 km/s DV, with the remaining 2.5 km/s DV needed to reach Mars done by the (now separate) spaceship’s own much smaller propulsion system. Concept C then leaves the 200-ton habitat behind on Mars, along with a further 190 tons of cargo, for a total of 4.1 tons per colonist, double that of Concept B.

Concept C has another even greater advantage over Concepts A and B: it requires only 465 tons of propellant to go back from Mars to Earth, less than a third of that needed by Concepts A or B. Furthermore, because of its rapid reuse of the launch vehicle’s second stage, the in-space propulsion system required to support a rate of five missions per opportunity in Concept C is also less than a third of that in Concepts A or B. If we combine these advantages, we see as a bottom line (as marked in green) that during each launch window, Concept C would allow for the delivery of about six times the payload to Mars as Concept B per each unit of transport system mass or per each unit of propellant produced on Mars.

However, Concepts A, B, and C all embrace an optimistic aspect of Musk’s proposal: the estimate of propulsion systems with dry-mass fractions of 0.08. The “dry-mass fraction” is the mass of a rocket or stage “wet” (that is, filled with fuel) divided by its mass “dry” (that is, empty). A dry-mass fraction of 0.08 means that the mass of the empty rocket would be 8 percent the mass of the filled rocket. For the remaining concepts, we will assume a more conservative dry-mass fraction of 0.12.

So Concept D repeats Musk’s plan (the slower version described in Concept B), but assumes a higher dry-mass fraction. And Concept E repeats my revised version (the slower and staged Concept C), but assumes a higher dry-mass fraction. Using these more conservative assumptions, the Revised version performs an order of magnitude better than the Original in all the relevant figures of merit. The advantages of employing the Revised design with the six-month trip to Mars are thus decisive.

But the relevant issue is not how these ideas might be implemented in a future Mars colonization program, but how we might put them to use in the sort of nearer-term Mars exploration and base-building program to be conducted by our own generation. Such a possibility is illustrated in Concept F. Like Concept E, Concept F adopts the revision suggestions I described above, and assumes the more conservative dry-mass fraction. However, in Concept F, the design is scaled down by an order of magnitude, so that instead of requiring a launch vehicle that can put about 500 tons into low Earth orbit, a launch vehicle able to put 50 tons into low Earth orbit will suffice. This is a critical distinction because, in contrast to 500-ton-to-orbit launchers — which at this point are the stuff of science fiction — at least three different launchers with capabilities of 50-tons-to-orbit or more may soon be available, including SpaceX’s own Falcon Heavy (54 tons to orbit, scheduled for first flight in 2017), as well as NASA’s Space Launch System (75 tons to orbit, first flight in 2018), and the Blue Origin New Glenn (about 65 tons to orbit, first flight by 2020). The improvements and revisions I’ve described make it possible to accomplish a Mars exploration mission using a 50-ton-to-orbit launch vehicle. Indeed, the mission presented in Concept F is comparable in crew size and capability to the Mars Direct or Mars Semi-Direct mission plans that I’ve described elsewhere, but with the advantage of using a 50-ton-to-orbit launcher instead of the 120-ton-to-orbit launcher employed by those concepts. This is a very exciting prospect.

Near-Term Mars Missions Using the Improved ITS Plan

Consider what this revised version of the ITS plan would look like in practice, if it were used not for settling Mars but for the nearer-at-hand task of exploring Mars. If a SpaceX Falcon Heavy launch vehicle were used to send payloads directly from Earth, it could land only about 12 tons on Mars. (This is roughly what SpaceX is planning on doing in an unmanned “Red Dragon” mission “as soon as 2018.”) While it is possible to design a minimal manned Mars expedition around such a limited payload capability, such mission plans are suboptimal. But if instead, following the ITS concept, the upper stage of the Falcon Heavy booster were refueled in low Earth orbit, it could be used to land as much as 40 tons on Mars, which would suffice for an excellent human exploration mission. Thus, if booster second stages can be refilled in orbit, the size of the launch vehicle required for a small Mars exploration mission could be reduced by about a factor of three.

In all of the ITS variants discussed here, the entire flight hardware set would be fully reusable, enabling low-cost support of a permanent and growing Mars base. However, complete reusability is not a requirement for the initial exploration missions to Mars; it could be phased in as technological abilities improved. Furthermore, while the Falcon Heavy as currently designed uses kerosene/oxygen propulsion in all stages, not methane/oxygen, in the revised ITS plan laid out above only the propulsion system in the trans-Mars ship needs to be methane/oxygen, while both stages of the booster can use any sort of propellant. This makes the problem of refilling the second stage on orbit much simpler, because kerosene is not cryogenic, and thus can be transferred in zero gravity using flexible bladders, while liquid oxygen is paramagnetic, and so can be settled on the pump’s side of the tank using magnets.

Using such a system, a manned expedition of Mars could be carried out any number of ways. For example, it could be done in a manner similar to the Mars Direct mission plan, with the first trans-Mars payload delivering an unfueled Earth Return Vehicle with an onboard propellant factory to make methane/oxygen propellant on Mars, and the second delivering a habitat module with a crew of astronauts aboard who land near the ERV, using their hab as their house on Mars. After 1.5 years of exploration they would return in the ERV, leaving their hab behind on Mars to add incrementally to the facilities of a growing Mars base as the missions proceed.

Or a different plan, closer in spirit to the SpaceX ITS, could be adopted, in which a single payload combining the hab and the ERV is sent, with the hab above and the ERV below. The ERV would use a limited amount of methane/oxygen propellant to perform supersonic retropropulsion of the combined payload upon Mars entry, bringing the assembly to subsonic speeds. Once this is done, the hab would pop a parachute, or possibly a parasail, to lift it off the ERV and then land nearby using a very small terminal landing propulsion system. The first such mission could send such an assembly out with no crew, allowing the ERV to be fueled in advance of the first piloted launch, which would then arrive two years later provided with a redundant hab and plentiful extra supplies. Once the base is well-established, the hab and ERV modules could be landed together, with the hab subsequently lifted off the ERV by a crane.

The number of such potential variations is endless. Another: In initial missions, the Falcon Heavy second stage could perform the full burn, allowing it to coast out to Mars in company with the piloted spacecraft, which could then use it as a counterweight on the opposite end of a tether to provide the crew with artificial gravity on their way to Mars (just as in the standard Mars Direct plan). This would entail expending the second stage, but it could be worth it for the first missions to have their crews in top physical strength, as they will reach a Mars with minimal support facilities. In later missions, the Falcon Heavy second stage could be left behind just short of Earth escape for ready reuse (as in the revised ITS plan I described above), and the crew be allowed to fly to Mars in zero gravity, since they would by that point have plenty of ample base facilities to provide local support for recovery from zero-gravity weakening once they reach the Red Planet.

Dawn of the Spaceplanes

Toward the end of his presentation, Musk briefly suggested that one way to fund the development of the ITS might be to use it as a system for rapid, long-distance, point-to-point travel on Earth. This is actually a very exciting possibility, although I would add the qualifier that such a system would not be the ITS as described, but a scaled-down related system, one adapted to the terrestrial travel application.

The point is worthy of emphasis. For three thousand years or more, people have derived income from the sea, for example by fishing — but far more by using the sea as a favorable comparatively low-drag medium for transport. Similarly, while there is money to be made by human activities in space, there is potentially much more to be made by human travel across space, taking advantage of the drag-free quality of space for rapid travel. It has long been known that a rocketplane taking off with a high suborbital velocity could travel halfway around the Earth (that is, reaching anywhere else on the planet) in less than an hour. The potential market for such a capability is enormous. Yet it has remained untouched. Why?

The reason is simply this: Up till now, such vehicles have been impractical. For a rocketplane to travel halfway around the world would require a DV of about 7 km/s (6 km/s in physical velocity, and 1 km/s in liftoff gravity and drag losses). Assuming methane/oxygen propellant with an exhaust velocity of 3.4 km/s (it would be lower for a rocketplane than for a space vehicle, because exhaust velocity is reduced by surrounding air), such a vehicle, if designed as a single stage, would need to have a mass ratio of about 8, which means that only 12 percent of its takeoff mass could be solid material, accounting for all structures, while the rest would be propellant. On the other hand, if the rocketplane were boosted toward space by a reusable first stage that accomplished the first 3 km/s of the required DV, the flight vehicle would only need a mass ratio of about 3, allowing 34 percent of it to be structure. This reduction of the propellant-to-structure ratio from 7:1 down to 2:1 is the difference between a feasible system and an infeasible one.

In short, what Musk has done by making reusable first stages a reality is to make rocketplanes possible. But there is no need to wait for 500-ton-to-orbit transports. In fact, his Falcon 9 reusable first stage, which is already in operation, could enable globe-spanning rocketplanes with capacities comparable to the DC-3, while the planned Falcon Heavy (or New Glenn) launch vehicles could make possible rocketplanes with the capacity of a Boeing 737.

Such flight systems could change the world.

Colonizing Mars

In his talk introducing the ITS, Musk suggested that a Mars colonization program using thousands of such systems could be used to rapidly transport a million people from Earth to Mars. This would be done to provide a large enough population to allow the colony to be fully self-sufficient. In subsequent interviews, he also said that none of these colonists would include children, since having kids around would be a burden upon the colony.

My own ideas on how the colonization of Mars could be achieved are different. Rather than a massive convoy effort to populate the planet, I see the growth of a Mars colony as an evolutionary development, beginning with exploration missions, followed by a base-building phase. As the series of missions proceeds, additional elements of the flight-hardware set would become reusable, causing transport costs to drop. Furthermore, as the base grows, its capability to produce more and more necessary items, including water, food, ceramics, glasses, plastics, fabrics, metals, wires, tools, domes, and structures, would expand — progressively reducing the amount of materials that needs to be transported across space to support each settler. This will provide the material basis for an expanding Martian population, which will grow exponentially as families are formed and children are born.

That said, Mars is unlikely to become autarchic for a very long time, and even if it could, it would not be advantageous for it to do so. Just as nations on Earth need to trade with each other to prosper, so the planetary civilizations of the future will also need to engage in trade. In short, regardless of how self-reliant they may become, the Martians will always need, and certainly always want, cash. Where will they get it?

A variety of ideas have been advanced for potential cash exports from Mars. For example, Mars might serve as a source of food and other useful goods for asteroid-mining outposts which themselves export precious metals to Earth. Or, since the water on Mars has six times the deuterium concentration as Earth’s, that potentially very valuable fusion-power fuel could be exported to the home planet once fusion power becomes a reality. Or maybe precious metals will be found on Mars, which, with a fully reusable interplanetary transportation system, it might be profitable to mine and export to Earth.

While such possibilities exist, in my view the most likely export that Mars will be able to send to Earth will be patents. The Mars colonists will be a group of technologically adept people in a frontier environment where they will be free to innovate — indeed, forced to innovate — to meet their needs, making the Mars colony a pressure cooker for invention. For example, the Martians will need to grow all their food in greenhouses, strongly accentuating the need to maximize the output of every square meter of crop-growing area. They thus will have a powerful incentive to engage in genetic engineering to produce ultra-productive crops, and will have little patience for those who would restrict such inventive activity with fear-mongering or red tape.

Similarly, there will be nothing in shorter supply in a Mars colony than human labor time, and so just as the labor shortage in nineteenth-century America led Yankee ingenuity to a series of labor-saving inventions, the labor shortage on Mars will serve as an imperative driving Martian ingenuity in such areas as robotics and artificial intelligence. Such inventions, created to meet the needs of the Martians, will prove invaluable on Earth, and the relevant patents, licensed on Earth, could produce an unending stream of income for the Red Planet. Indeed, if the settlement of Mars is to be contemplated as a private venture, the creation of such an inventor’s colony — a Martian Menlo Park — could conceivably provide the basis for a fundable business plan.

To those who ask what are the natural resources on Mars that might make it attractive for settlement, I answer that there are none, but that is because there is no such thing as a “natural resource” anywhere. There are only natural raw materials. Land on Earth was not a resource until human beings invented agriculture, and the extent and value of that resource has been multiplied many times as agricultural technology has advanced. Oil was not a resource until we invented oil drilling and refining, and technologies that could use the product. Uranium and thorium were not resources until we invented nuclear fission. Deuterium is not a resource yet, but will become an enormous one once we develop fusion power, an invention which future Martians, having limited alternatives, may well be the ones to bring about. Mars has no resources today, but will have unlimited resources once there are people there to create them.

Martian civilization will become rich because its people will be smart. It will benefit the Earth not only as a fountain of invention, but as an example of what human beings can do when they rise above their animal instincts and invoke their creative powers. It will show to all that infinite possibilities exist — not to be taken from others, but to be made.

No one will be able to look upon it without feeling prouder to be human.

Robert Zubrin, a New Atlantis contributing editor, is president of Pioneer Energy of Lakewood, Colorado, and president of the Mars Society. The paperback edition of his book Merchants of Despair: Radical Environmentalists, Criminal Pseudo-Scientists, and the Fatal Cult of Antihumanism, was recently published by New Atlantis Books/Encounter Books.

Correction: When first published, the opening of this article described Elon Musk as the president of SpaceX; he is in fact the CEO and CTO.

Robert Zubrin, “Colonizing Mars: A Critique of the SpaceX Interplanetary Transport System,”, October 21, 2016.

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Who want to live on Mars?

NASA is now hiring astronauts for trips to space and Mars that would blast them with radiation, but Crave’s Eric Mack learns that some corners of the world already get a similar treatment.


    Why the best Mars colonists could come from places like Iran and Brazil

by Eric Mack


Mars colonists will need to stand up to heavy doses of radiation.


On Monday, NASA officially opened an application window for the next generation of American astronauts it hopes to send to the International Space Station, lunar orbit and eventually to Mars. But to find the best candidates for dealing with the harsh levels of radiation in space and on the Red Planet, the agency may want to consider looking beyond the borders of the United States for applicants.

One of the biggest challenges in sending astronauts into deep space or setting up a base on Mars is dealing with the radiation from the cosmic rays that our sun and other stars send flying around the universe. Earth’s atmosphere and magnetic field deflect the worst of this radiation, but Mars has no substantial magnetic field, which has in turn allowed much of its atmosphere to be lost to space over the millennia.

Spacecraft can be equipped with radioactive shielding to some extent, and a base on Mars could also be constructed essentially underground, using several meters of Martian soil to provide radiation protection on par with Earth’s atmosphere (this is what Mars One hopes to do). But when it comes to roaming around the surface of Mars in a spacesuit or in a rover, there’s no real practical way for those astronauts to avoid some big doses of radiation in the process.

When I attended the New Worlds conference earlier in 2015, there was a discussion of the challenge that cosmic radiation presents for space exploration, and there were some pretty far-fetched possible solutions, like genetically engineering astronauts in the future to handle more radiation.

But I was more intrigued by one partial solution that was mentioned in passing and only half-seriously — to consider astronaut candidates who are already used to dealing with more exposure to radiation than most of the rest of us.

For years now, scientists have been studying residents of Ramsar, a town in northern Iran that is believed to have the highest levels of naturally occurring background radiation for an inhabited area. Levels up to 80 times the world average (PDF) have been measured in town, yet studies of the few thousand people living in the area show rates of lung cancer are actually below average. In fact, research shows that a gene responsible for the production of white blood cells and so-called “natural killer cells” that attack tumors was more strongly expressed among the population.

10 spots in our solar system worth visiting…

In other words, there may be no need to engage in controversial “editing” of human genetics to create radiation-resistant astronauts because there might already be good prospects in a few corners of the world.

Besides Ramsar, the beaches near Guarapari, Brazil, also exhibit very high levels of natural radiation. People in Yangjiang, China, live with radiation levels three times the world average but have below-average cancer levels, and the story is the same in Karunagappally, India.

Unfortunately, none of the people from these areas would be eligible for the program NASA is now hiring for — the agency is only looking for American applicants. So who in the United States might be best suited for withstanding the most cosmic radiation?

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As it turns out, I think it might be me. According to the US Nuclear Regulatory Commission and the National Radiation Map, Colorado — where my family has hailed from for generations — has some of the highest levels of background radiation in the country thanks to the high altitude and naturally occurring radioactive elements working their way up from the Earth.

Today, I’m actually about 50 miles south of the Colorado border, but I’m living at a higher elevation than Denver, and previous reporting has taught me that radon levels are actually quite high in the neighborhood as well.

Unfortunately, I am quite content just writing about space exploration and have no interest in ever leaving this planet myself. (As witness our CraveCast episode, Who wants to die on Mars?) Besides, some of my neighbors — who have lived with this region’s natural radiation for many more generations than my family has — would probably make better candidates.

So if NASA is unwilling to change its eligibility requirements to consider candidates from northern Iran, perhaps the organization ought to consider sending a recruiter to Taos Pueblo in northern New Mexico instead.