Elon Musk : "Retire on Mars" : feasible?

Factual Questions
1

Well, in order for Mr. Musk to retire on Mars, there would need to be a substantial amount of infrastructure in place in order for him to enjoy his twilight years in luxury.

I’ve been trying to “rough out” a basic mission to Mars in order to get an idea if his plans are even technically feasible.

Before a large base could be constructed, he would need to get a test group to Mars. 6-10 people or so. Suppose that the mission were to depart in 10 years, with 10 people, for a total budget of no more than 10 billion. Mr. Musk is worth a bit over a billion at the present time, but, presumably, he could get his buddies to chip in a few billion. Also, since NASA is willing to spend a billion per Mars probe, maybe they could sell a seat or 2 to NASA or do paid scientific research when there.

Ok, so his company’s Falcon Heavy is supposed to cost $120 million per launch. Assuming SpaceX is being honest about the production costs for the Falcon 9 being low enough that a launch can be done for $60 million, that seems plausible. The Falcon Heavy is basically 3 falcon 9 lower stages strapped together.

Listed payload to GTO is 21,200 Kg. Using a delta-V table, I find out that http://i.imgur.com/WGOy3qT.png you need about 1.16 km/sec delta V from GTO to reach Mars, assuming aerobraking for the Mars capture and other maneuvers.

That means 14,500 Kg of the payload make it to Mars aerobraking, and, assuming similar efficiency to the curiosity rover’s descent system, 6,889 Kg make it to the surface.

Yikes. Every Kg of supplies is $17,400. Anyways, an empty dragon spacecraft is 4200 Kg, so it looks like the Falcon Heavy is approximately a big enough rocket to get a crewed dragon spacecraft to Mars.

Of course, just 1 launch is nowhere near enough. You’d need enough launches to orbit modules for the journey to Mars (supplies, living space, etc), and a bunch of unmanned launches to test the landing system and place the initial supply dump on Mars before any crew get there.

But, at first glance, it looks maybe possible. I said a 10 billion budget, so if 25% of the budget were spent paying for launches, that’s 2.4 billion for 20 launches. R&D for the various new systems this kind of expedition would need would cost a few billion, and there would also be construction costs to build the spacecraft.
Long term, apparently, humans need something like 0.8 Kg of oxygen, 0.63 Kg of food, and 26 Kg of water per day.

Theoretically, you could recycle almost all the water and oxygen, and produce at least some of the food with algae or hydroponic plants. Assuming that cuts the total supply requirements to 0.5 Kg/person/day, 10 people would need 5 Kg per day, and 1825 Kg per solar year. From above, that comes to approximately 1 dragon spacecraft stuffed full of supplies per year, which means it would only cost $120 million/year to keep 10 people alive on the surface.

Now, there’s a couple of show-stoppers.

Well, water recycling is in use on the ISS, cutting that number down considerably if it works. However, it sure would be handy if the carbon dioxide could be converted to oxygen, and at least some of that carbon dioxide were made into additional food.

To do this, you’d need algae tanks or some other method, and I could not find any information about testing of these kinds of life support systems on the ISS… I’m not certain what they are doing up there, but, apparently, recycling food and oxygen is not one of them.

You could not depart on a Mars expedition without checking to make sure recycling systems actually work long term (several years) and in space environments (low gravity, radiation, etc).

Similarly, it is known that zero-G exposure is bad news. Bone density loss, retinal detachment, and a long long list of other unpleasant effects. The catch is, humans have never been exposed to 1/3 G for long periods of time, either. No one knows if humans will go blind or become too fragile to move or other nasty long term effects. The only way to even find out for certain would be to put humans in a centrifuge in space at 1/3 G for several years. (well, first doing it with other vertebrate animals, but, eventually, humans)

Surely they have some rats on the ISS at 1/3 G, spinning for years, right? Apparently not…

This is a big problem. It looks like Mr. Musk could theoretically get together the rockets and the other systems that would put people on Mars. However, without these crucial tests, he would have no way of knowing if people could live there for long.

http://www.projectrho.com/public_html/rocket/lifesupport.php
Anyways, I’d love to hear from some of the engineers on Straight Dope. Straight up, no b.s., could it be done for a reasonable level of risk?

2

Musk is crazy-to plant a colony on Mars would be the height of foolishness-just supplying the colony would require 10 times our world heavy launch capability. If he loves it so much, why doesn’t he live on Devon Island? Much nicer RE, and you can always leave if you get tired of the scenery!

3

Note that this is a small fraction of most estimates.

4

The key to living on Mars is using local resources to get oxygen and water. Here’s a recent paper describing a system to produce water (oxygen by extention) and methan using only hydrogen feedstock from Earth - http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4101.pdf By using local resources you can save a lot of mass but you need to get the systems and their power source to Mars in the first place.

But luxury? That implies manufacturing facilities, farms and habitats in excess of what is needed to live. I can see all of that but not within the next 40 years or so.

5

I always wonder whether Elon Musk intends to just go and see what happens. I’m thinking of the test-pilot mentality of Richard Branson, or S. R. Hadden sailing off into the unknown at the end of his life in the novel Contact.

6

Water and atmosphere on the International Space Station are controlled and provided by the Environmental Control and Life Support System (ECLSS), which despite being called a system are really a number of essentially independent systems of both US and Russian design. Oxygen and water are primarily provided by scrubbing the air for waste carbon dioxide, electrolysis, and filtration of waste water, but there are stores of both water and oxygen (in the form of solid fuel oxygen generators) which will suffice in the case of temporary failure of the primary systems to allow time to repair or evacuate. Both the US and Russian electrolysis systems have had numerous problems (although the latter moreso) and do require regular resupply in order to replace expendable elements.
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US$10 billion isn’t even on the low end of credible estimates of the cost of a crewed Mars mission. It may be feasible to perform a bare-bones, high risk flag planting mission (~80% chance of success) at around US$100B using commercial launch services. A low(er) risk mission with a higher probability of success (~95%) is going to run at least US$200B, and possibly as much as US$500B depending upon the objectives and scope of the mission. At that, it will expose the crew to amounts of cumulative radiation approaching if not exceeding lifetime maximums.

Setting aside the long term health risks to the crew from ionizing cosmic radiation, the major risks that have to be considered and mitigated in order to keep the overall mission risk to an acceptable level are: risks to health, such as the highly ionizing radiation from solar flares, health effects from the low/microgravity environment (bone loss, muscular degeneration, loss of coordination), hygiene control in the microgravity environment, moderation of carbon dioxide atmosphere levels, nutritional integrity of micronutrients in preserved food; reliability of the space vehicle, e.g. propulsion systems, thermal control systems, power generation systems, communication systems; and operational risks, such as deorbit and aerobraking operations, the landing operation, emplacement and habitat construction, any in-situ resource extraction and utilization, retrieval and return, and the Earth injection and aerobraking/reentry operations.

Every single one of these issues will require specific, purpose-build systems and processes, virtually none of which have been demonstrated to a level suitable for a crewed mission, and a failure to successfully mitigate a problem arising from one of these issues would result in not only loss of crew of a loss of mission (including the investment of tens of billions of dollars) but also blowback on crewed space operations of any kind.

Advocates of a near-term crewed mission to Mars (such as Musk) seem to view a trip to Mars as just an extended Apollo-type effort. This belies two very important points; one is that sending a crew of two men to the surface of the Moon required enormous technical effort and focus, driven almost exclusively by Cold War efforts to top the Soviet Union, with an essentially blank check and a willingness to accept any risk. Although it is commonly assumed that what we did then can be done now for pennies on the dollar based on the assumption that all technology has moved at the same pace as computing, the reality is that we cannot currently even accomplish the same objective that we did in 1969.

The second is that going to Mars isn’t just a twice as hard as going to the Moon, or 90 times as hard (the ratio of time to get to Mars versus the Moon) or even 350 times as hard (roughly the ratio of the difference traveled on a pseudo-Hohman trajectory to Mars versus that taken by the Apollo spacecraft to the Moon). It is many orders of magnitude more difficult. The duration and distance means that there is absolutely no possibility of rescue from Earth. Whereas the crew of the Apollo XIII mission could swing a pass around the Moon and make a free return trajectory to Earth, using the LEM engine for trajectory corrections, once a spacecraft bound for Mars leaves the Earth’s sphere of influence, it is gone for three years. Everything the crew may possibly need to survive for three years has to be carried on board, including air, water, and food. There is no stopping, returning, or getting any supplies or resources on the trip there or back. This argues for a fully redundant mission (e.g. two spacecraft, landers, full crew, et cetera), such that any catastrophic failure of a single ship is still recoverable as a mission and offers the potential to rescue the crew. Similarly, the duration the crew must survive on the Mars for over a year versus a few days on the Moon, and under a variety of environment conditions (such as dust storms and low solar incidence) which preclude solar power generation.

It should be noted that Mars is almost the most difficult body on the solar system to soft land. It has just enough atmosphere to significant result in aerodynamic heating, but not enough to be truly effective for flying or parachute landing of a large capsule. The Mars Exploration Rovers were just about at the limit of payload that can be landed with just parachutes and airbags (and did use some very modest sized solid propellant retrorockets to slow the final descent before release). The Mars Science Laboratory required a ‘sky crane’ to successfully land. A crewed vehicle will require essentially a reusable single-stage-to-orbit type system to safely land a crew, which is a capability that has not yet been successfully developed.

As for growing food, one of the critical nutrients required for this are nitrates, which provide fixed nitrogen for plants. Thus far, no significant amount of nitrates has been found in Martian soil despite the earlier expectation that it would be abundant. There may be nitrates available deeper in the soil, but this would entail more operations (digging and separating) and risk. The same distance from the Sun and atmospheric disturbances that preclude using solar power also make growing food using the Sun as an energy source problematic, which requires more energy.

So as can be seen, just moving payload to a Mars injection orbit is just one proportionally quite small element in any overall effort to send a crew to Mars. Practically speaking, there is no good reason to do this (nor a way to realistically mitigate most of the risks) until we have propulsion systems which are capable of sending a crew and supplies to Mars much faster than the current low total impulse chemical propulsion systems, notwithstanding the technologies and systems necessary to land a crew and sustain them for months.

As for the value of NASA paying for a seat or two on a private crewed Mars effort, this would not be a good value either in terms of science return for the dollar or publicity. NASA/JPL has received much public kudos for their highly successful MER and MSL missions, which have returned an incredible amount of information for a fraction of the cost of a single share of a crewed mission, and unlike a crewed mission, they aren’t constrained with the distance a crew member could travel and return in a single day, or the possibility of fatigue or radiation exposure causing a crew member to become ill, or ultimately having to return the crew member back to Earth. For the cost of a single crewed mission we could almost literally pepper the surface of Mars with hundreds of robotic explorers, returning a multitude of data from disparate points that a single crewed mission could not possibly hope to cover.

This isn’t to say that there isn’t a place for people in space; far from it. As versatile as robotic probes and rovers are, they don’t think, and their remarkable achievements are due to the designers and mission controllers working in concern to predict potential problems and come up with workarounds for issues that occur in the field. Indeed, every “robotic mission” actually has a massive crew of people who are all working through the conduit of the robotic explorer, and as the capabilities of such vehicles become more extensive and robust, the difference between what could potentially be done by a person in even the shirt sleeve environment and a rover or proper will shift toward the robotic explorer. And the physically closer people are to a probe, the less time lag mission controllers will experience and the more they can do to interact closely on the mission. Ultimately, we’ll want to build solar orbital habitats which can be self-sustaining and support resource extraction and as bases for further exploration of the solar system and surrounding regions. But sending someone to the surface of Mars to put down foot prints and peer through a hazy pressure suit visor versus a rover with a multitude of purpose-built instruments and which never gets hungry, tired, or cranky just makes very little sense from any practical standpoint.

Stranger

7

The first thing is that launch costs need to go down by an order of magnitude. Musk seems confident that this is possible with sufficient reusability. SpaceX is making good progress but it’ll be a while before they can fully reuse both the first and second stages, still it seems doable within his lifetime.

The second thing is that we need to robotically build up some infrastructure on Mars. Fortunately, it doesn’t matter if this stage is slow, because no one is eating supplies or getting a radiation dose while it’s happening. If we occasionally lithobrake a load of supplies into the Martian surface… so be it. Send another. We’re used to Mars being hard. The Curiosity landing was complicated in part because of the scientific objectives: the skycrane was only necessary because they didn’t want to kick up a bunch of dust. It was much more complicated than landing some dumb equipment would be.

The next thing is that we need faster transport of crew capsules, using VASIMIR or similar technology. The tech is still a ways away. Fortunately, this doesn’t have to be some monstrous rocket that carries the full supply load, since that’s already on Mars. It just needs to be comfortable enough for a month or however long it takes with the more advanced technology. This is probably the hardest part.

SOAT: I find this line in your post to be hyperbolic to the point of absurdity:
*A crewed vehicle will require essentially a reusable single-stage-to-orbit type system to safely land a crew, which is a capability that has not yet been successfully developed. *

Mars is definitely not easy to land at but it’s not even in the same ballpark as an SSTO. The atmosphere is thin but you can still aerobrake down to a few hundred meters/second, even without a parachute (the Curiosity rover parachute deployed at 450 m/s). That compares to 4.1 km/s for Mars->LMO or 7.8 km/s for Earth->LEO. Even with a very modest ISP of 250, 20% of the mass as fuel gives you 500+ m/s of delta V. And that’s even without any staging or parachutes.

8

Personally, I think we should devote our main efforts to cheap access to space, first. Once we have that, most of the other difficulties with a Mars mission become much more tractable. Get a space elevator or the like up and running, and we won’t care if we need hundreds of tons of shielding or fuel. Heck, once you’ve got one space elevator, you can make another one and send it to Mars pre-built.

9

You’re better off not waiting for the Earth elevator. A Martian space elevator is way easier than an Earth one. It can be done with synthetic fibers already in mass production (and of course would be nothing like the elevator in Red Mars). The engineering is by no means trivial but we don’t have to wait for nanotube production.

10

Reusability of the vehicle does not necessarily translate into a significant reduction in overall launch cost. In fact, vehicle fabrication, while not insignificant, is often not the biggest cost line item. Acceptance testing, system integration and testing, payload integration, launch operations, range support, and administrative costs are also significant drivers which may cost as much or more than vehicle and propulsion system fabrication. In fact, in the case of the Shuttle, the focus on reusability actually retarded progress in evolving the design. If the Orbiter had been flown for a more limited lifecycle–say, ten flights each–there would not have been such an emphasis on maintaining a configuration with significant problems for decades.

At any rate, orbital launch costs are a small part of a projected crewed Mars mission. Even at a presumed US$1B per launch for a super heavy lift system like the SLS, ten launches would still be only 5% of a US$200B budget. And this is the point that Musk seems to be missing; regardless of what SpaceX or another commercial provider can put into orbit, there are a massive number of other issues to be addressed before a credible crewed interplanetary mission can be launched.

You can’t just calculate the fuel/overall mass ratio for a given impulse to cancel orbital speed and call it good. It’s not just enough to cancel forward velocity; you also have to actually land in a controlled manner, which requires additional impulse.

Mars atmosphere is indeed thin, and this poses some highly problematic issues. For a given dynamic pressure, the true airspeed is going to be much higher. This translates in to high heating rates and a low L/D for a given lift area. So this means that to transition from aerobraking to controlled flight requires an enormous pressure surface which has to be protected from heating during the aerobraking phase. Most proposals for a large (i.e. crewed) Mars lander from the mid-'Eighties onward assumed a blunt based biconic (or squashed biconic) capsule which would enter base forward for aerobraking and then translate into a forward lift orientation for gliding, then finally going into a powered landing mode at somewhere around 150-200 m/s. Even this was fairly marginal in terms of fuel usage (the vehicle could not carry enough fuel to land and then take off again without refueling) and the experience with controlled gliding biconic flying shapes is still at a pretty marginal state.

What this boils down to is that the best approach to landing on Mars with current technology will be essentially an SSTO-type design, except descending in the fully fueled state. The total impulse requirements end up being surprisingly close to a RSSTO design, except for needing significantly greater lift area. In fact, modifications to the Delta Clipper form were actually proposed for some versions of a Mars lander. The Delta Clipper SSTO remains unrealized (though plausible) and one of many components of a credible crewed Mars mission would require the development of a lander capable of landing crew, instruments, consumables, and habitat.

Stranger

11

I agree with this, but it’s a two-way street. Consider the cost of launching some dumb cargo to Mars, like bulk food or water. How much effort do you put into developing a reliable cargo transport system?

Suppose you could develop a $10 M unit that only worked half the time, but it cost $100 M for a system that was 95% reliable.

Is it worth it to spend the extra effort? It certainly does if the launch itself costs $100 M. But if the launch is $10 M, then you’re better off with the low-reliability craft, because if it blows up or goes off course, you just send one or a few more, and you’ve still come out ahead.

Not all costs scale in the same way but dumb supplies and infrastructure are going to be most sensitive to this effect and that’s going to be a big fraction of any Mars mission.

Sure. 500 m/s is probably low-balling it sans parachute or fancy aerodynamics. But Musk thinks he can do it with the Dragon capsule on its next-gen hydrazine thrusters.

Well, that sounds pretty close to the current Dragon capsule. I don’t know how maneuverable it is, though. I don’t know how big a craft you’re thinking of.

Of course. This entire discussion is predicated on it being a one-way mission. Clearly, a return mission is going to be an order of magnitude harder and might require local refueling.

The actual crew landing capsule can be a very simple thing and only needs to carry the mass of the crew itself. It needs accurate targeting to land near the supplies, so it’s not trivial, but NASA has shown already that it’s not an intractable problem.

Again, it sure seems like you’re assuming a craft that can land and take off again. I’d certainly agree that such a craft is damn close to an Earth SSTO, but that’s not the proposal here, which is for Musk (or whoever) to land, live a few years, and die.

12

The materials might be cheaper, but a space elevator of any material is going to be big and heavy, and you need to either launch all that weight somehow, or find some way of manufacturing it on-site from local raw materials, either one of which is going to be difficult and expensive.

Besides, it’s not like carbon nanofiber would be developed just for a space elevator. It’s really practical stuff, and is sure to be developed for other applications with or without an elevator. Once we’ve got golf clubs and fishing line and skyscrapers and suspension bridges made with it, then we can start thinking about how to adapt it to an elevator.

13

This was the essential proposal of a number of Big Dumb Booster and similar systems, such as Bob Traux’s Sea Bee/See Dragon; accept a reduced reliability (in the case of the Sea Dragon, a loss of one flight out of three, or 67%) and reduced performance and accuracy for substantially reduced launch costs. This makes sense for moving bulk cargo, like water, air, or propellants, to orbit. However, it does not translate into a substantial savings for an interplanetary mission, where the majority of cost is still in delivering the payload to a target destination on another body. And you cannot hard land (“lithobrake” in your nomenclature) a cargo that you wish to remain intact for recovery. Tanks of water, air, and supplies still have to remain intact to be useful.

The feat of launching a cargo and returning the capsule to Earth in no way represents the unique difficulties experienced in landing a large craft on Mars. On Earth, the thick atmosphere provides the ability to attain lift with a relatively small working area at high altitudes and land via aerodynamic decelerator (parachute, parawing, or other controllable drag-inducing systems) or lifting body surface at low altitudes. On the Moon, the lack of atmosphere means that you can descent down at any speed and use thrust at intervals to optimize propellant usage. On Mars, the thin but significant (in terms of aerodynamic heating) atmosphere poses the worst conditions; you have to slow down relatively early in flight to prevent excessive heating and carry thermal protection systems (TPS) to protect the exposed areas of the craft, but the lifting surface required for gliding is so enormous that TPS would take a considerable amount of the mass budget to protect such a surface. The other alternative–using propellant to slow down and land the craft from high altitude–also carries a large mass penalty. During the time when NASA was aggressively pursuing an architecture for a crewed mission to Mars (1984 through 1991) there were an enormous number of studies on how to configure a large craft (sufficient for a crew of 8-12) for landing on Mars, and no truly ideal solution emerged that was viable given then (and now) current technology.

The SpaceX Dragon capsule is not a biconic, is not design for actively controlled gliding, and produces only a very small L/D, similar to other blunt arsed capsules such as Apollo. It is not designed for landing on the surface of Mars. The animations you’ve seen of it performing a purely propulsive return landing on Earth are nothing more than cartoons which are risible to anyone actually familiar with propulsion systems and reentry vehicles. The Falcon 9v1.1 Stage 1, by comparison, reserves about 5% of its total propellant mass to effect a soft landing, which is larger than its mass fraction. The Dragon capsule would have to have a propellant capacity nearly three times as great as the capsule volume to perform the same maneuver.

Despite holding the title of Chief Engineer for SpaceX, Elon Musk is not an aerodynamicist, propulsion engineer, or vehicle designer. There is a long history of Mr. Musk making public claims about what SpaceX would accomplish that have been later tacitly retracted. While SpaceX has made some impressive accomplishments–developing and successfully an EELV class vehicle on a commercial basis is no mean feat–the vehicle and its capabilities are largely very conventional, with the largest innovation to date being the attempt of a soft recovery of the first stage. Accomplishments at one part of a system for interplanetary transportation system–the launch to orbit system–in no way translates to overcoming the other significant obstacles that no one has yet proposed adequate solutions for using extant technologies. From a systems standpoint, it isn’t enough to have one part of the solution in hand, and sally forth assuming that all other parts will somehow technologically fall in line; the actual necessary technologies and processes need to be developed and matured before you can make a credible effort.

I know that twenty-five years of increasingly impressive digital effects in movies and t.v. make it seem like we should just be able to conquer any “engineering challenge” with the right gumption and guile, but the reality is that the same physical constraints that prevented us from doing this then apply now. The propellants and, in large measure, the propulsion systems we use today are essentially the same as were used circa 1975. Simulation tools and knowledge about the interplanetary and Martian environments have all improved, but those improvements have largely served to detail just how much more difficult such a venture would be compared to what was known twenty or thirty years ago.

As for Musk “retiring” to Mars on a one way trip, I can’t think of anything more wasteful and foolish. It would be a substantial expenditure of resources to no useful end, compared to developing actual methods for near Earth resource extraction and use which would support a sustainable human presence in space and ultimately provide the necessary technologies for interplanetary exploration without having to venture untold hundreds of billions of dollars on high risk flag-planting efforts capable by using terrestrial resources.

Stranger

14

Stranger, 100 billion? Really?

Here’s sort of what I had in mind : we do 20 heavy lift launches. Each one contains either a Red Dragon lander or a long cylinder that spaceX makes using the exact same technique they use to make the fuel tanks for their current spacecraft. No windows, bare bones.

We somehow lash all 20 launches together by putting them near each other and strapping them together somehow. I guess we’d need docking couplers. Since SpaceX already has one half of a docking system with their existing spacecraft, it doesn’t sound that hard to add the other half.

We stuff each one with lots and lots and lots of supplies and life support equipment. Basically, you’d cram in lots of duplicate ways to recycle water and air, and lots and lots of spare parts.

Somewhere in the middle of all these supplies we stick the radiation storm shelter.

Anyways, once we get near Mars we choose the non-failed life support equipment, and the best of the remaining supplies, and cram it into 10 or so dragon landers. I guess we distribute the crew between the different landers so if one or two crashes it won’t doom the rest.

I found a very good article on how to do a heavy landing : http://www.quora.com/SpaceX/How-does-SpaceX-plan-on-landing-a-heavy-craft-on-Mars

It’s not the same way the curiosity did it, it’s simpler, it just costs more rocket fuel.

Anyways, on the ground, just try to stay alive. All that planning you mention above? Too expensive. Frankly, human lives are not worth that much in reality. Statistically, people value their own lives at somewhere around 10 million dollars. So if exhaustive safety checks and planning like you describe cost more than that per astronaut, it’s not worth it. Better to just try it.

I think you’re making a mountain out of a moehill. It’s not 350 times as hard, it’s more like a factor of 2 or 3.

15

Sure, but that looks to be many decades off. No one has, even in the lab, produced even a single strand of CNT long enough that it could be woven into a ribbon. On the other hand, I can walk into the nearest sports mart and for $20 purchase a reel of Spectra fishing line–sufficiently strong, with the right taper, to work as a space elevator on Mars.

16

The 1990 Space Exploration Initiative “90 Day Study” proposed a space station/Moon/Mars infrastructure with an overall cost of US$500B in FY1990 dollars, approximately US$990B in 2013 dollars. The cost of the Mars exploration portion of the program was $258B (~US$510B in FY2013 dollars), so the cost evaluation of the program I worked on is remarkably consistent with prior estimates. To put that in context, the Apollo program, with development of the Saturn I/IB, Saturn V, Apollo CSM and LM, six test launches, and eleven crewed launches with a total of ~110 days total crew duration and less than 170 person-hours of EVA time cost approximately ~US$109B in 2010 dollars. A crewed Mars mission would have essentially five times the total duration, so even assuming the same overall level of complexity, an estimate of US$500B is entirely reasonable to develop the overall architecture.

When you don’t know anything of the complexities or difficulties of what you are talking about, everything seems very simple. The reality is that while we’ve become fairly accomplished at docking small capsules to the ISS and assembling modules, all of this has required substantial development and takes intricate mission planning for a structure that only sees very a very minimal amount of thrust during orbit-raising maneuvers (<0.01 G). It doesn’t just happen to work out, and in fact a failure in docking or assembling modules could result in catastrophic damage to the station. I get the impression that when you talk about “somehow lashing all 20 launches together…and strapping them together somehow” you are thinking about rafting boats or barges. But whereas boats will naturally drift to a stop and will float in formation with just some lash lines, objects in space will continue going until they impact, upon which they’ll then bounce around like pool balls, and in order to apply a thrust to the mass a rigid thrust structure needs to connect together all elements and permit direction of the thrust through the center of mass.

When it comes to handling objects in free fall, or indeed, orbital mechanics in general, you have to throw everything you “know” from terrestrial experience out the window. Just the problems of handling multiple masses alone require their own particular engineering solutions, and this is the reason that, after the actual lunar landing operation, the Lunar Orbit Rendezvous portion of docking the CSM to the LM was considered the highest risk of the Apollo program.

Saying that it “just” costs more fuel again belies the lack of understanding that you have about the essential problems. More fuel means a larger craft (to carry tankage the fuel), which means a larger amount of surface to protect, all of which means more mass. There is nothing “simple” about a powered soft landing, which is why the MER and MSL landings used such a complex multi-mode landing system.

Setting aside the callus disregard for the lives of the crew, it isn’t just the (presumed) $10M cost per crewman lost; the loss of a crew during a crewed mission means the loss of major mission objectives or the entire mission, i.e. the hundreds of billions of dollars poured into the mission. It would not be sensible to undertake a mission of such costs with a low order chance of success.

As for “on the ground, just try to stay alive”, this is not the New World. There are not abundant natural resources to use or natives to exploit. Everything a crew would need to stay alive needs to come along with them, and that requires extensive planning, a credible evaluation of and provision for contingencies, and a recognition that there is no chance of rescue or resupply. Yes, planning and providing for contingencies is expensive. It is also crucial to the success of an inherently risky activity with a high incidence of critical failure modes such as crewed space exploration. The crew of the Apollo XIII didn’t survive by just McGuyvering their way out of a series of problems (despite the impression that the Ron Howard film gave); everything they did to effect self-rescue was part of previous contingency planning and procedures as well as literally thousands of people on the ground performing analysis and simulations. And this was for a mission that could return in the span of a few days. A critical failure half way into a two year mission pretty much guarantees loss of crew and major mission objectives.

There is absolutely nothing in your posts which provides any basis for that estimation. Indeed, you’ve failed to address major issues, such as propulsion systems, in-transit and on-Mars power generation, and exposure to radiation in any depth whatsoever. And yet you want to assert that this should all be doable with extant technology for relative pocket change, which begs the question of it hasn’t been done previously, if not by NASA then by the former Soviet Union, the European Space Agency, or JAXA (which had a vigorous effort for a crewed space program before realizing that the costs would be orders of magnitude more than estimated.)

To some extent, it is true that NASA has made spaceflight more complex and costly than necessary, with the Space Transportation System (“Shuttle”) and ISS probably doing more to retard technical progress than to advance it. And there are certainly ways to reduce the cost, and increase the frequency and availability of launches that the ULA and other conventional launch providers have not embraced because there was no financial incentive to do so. (It is well understood in the space launch community that ULA could easily double the launch rate of the Delta IV and Atlas V by implementing a number of processing and integration operations, but doing so would reduce costs to a point that their net profit would decrease, so there is no incentive for ULA to do so.) But that doesn’t mean that all previous cost estimates go out the window, and any space activity–especially activities that are beyond what has been currently demonstrated–can be made arbitrarily cheap by adopting greater risk. One only needs to look at the evolution of cost estimates provided by SpaceX to see that with increasing design maturity also comes an increase in the actual costs versus what was originally advertised.

Stranger

17

Granted I’m no engineer, but the thing about living on Mars that strikes me as fanciful is that we haven’t yet figured out how to live on the planet that we were designed to occupy without destroying the environment. Perhaps we would be well served to master the art of living on Earth before endeavoring to live on less hospitable planets.

I apologize if this response misses the spirit of the OP.

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I don’t know about missing the spirit, but it highlights a point that most people don’t appreciate. We live on a world that is essentially designed to support us (more properly, we’re evolved to fit it) and on which resources that we need to sustain ourselves are so abundant that we have almost no concern about conserving or recycling them. Even the most self-sufficient individual still consumes and wastes far more resources than they can possibly recycle, and attempts at making a truly self-contained, sustainable environment have served to demonstrate how little we actually understand about the complexities and interactions of a completely independent ecological system. Going to another planet means carrying every possible resource to maintain life for a period of years without resupply, which is something no one has ever actually done with success. “Retiring” to Mars or living there indefinitely requires developing systems that are capable of recycling and conserving resources to a degree that has yet been demonstrated.

Stranger

19

The Sea Dragon was one of my favorite concepts. It also leads into another point I wanted to make: you can skimp on the materials if the launches are cheap enough. The Sea Dragon was made from a common steel–none of this crazy aluminum-lithium whatever that NASA and even SpaceX uses.

Likewise, bulk cargo lifted with a sufficiently cheap launcher should use lower performance materials. If the launch costs $10k/kg, then you’ll spend $9.9k to save a kg. That argues for expensive materials. Reduce by a factor of 10 and suddenly you’re better off with steel and more ordinary aluminum alloys.

“Lithobrake” was my little joke in referring to cargo that lands unsuccessfully. Still, something came to mind, which is that although we know that air bag landing has scaling limits, there’s no reason why bulk cargo has to land in one lump. The cargo could split into several-hundred-kilo lumps, each with their own air bag system.

Aim for a crater and the cargo might all roll downhill into the same spot :).

I’m still not seeing where this phase is worse than on Earth. LEO has like double the KE of LMO (I’m not counting MTO to LMO since that’s a separate and more gentle aerobrake maneuver).

Can you elaborate on the ways in which it is wisible… er, risible? From what SpaceX and others have demonstrated already, the control systems behind propulsive landing on Earth appear to be downright easy. The Dragon capsule has already shown the ability to make it through the atmosphere and splash down safely with a load of cargo. I am really not seeing where adapting their launch abort thrusters to a propulsive landing system is some kind of showstopper.

Uh, what? The F9 1.1 first stage has a payload fraction of 19%. Reserving 5% for a soft landing means losing 1/4 of the upper stage mass (IIRC, SpaceX has said this will result in a 50% total payload reduction).

I would really, really like to see some hard numbers here. In particular, how much delta-V are you proposing and what specific impulse? The SuperDraco thrusters are NTO/MMH bipropellant, like the Shuttle OMS engines, and 300 seconds seems reasonable based on similar engines I’ve read about (the OMS engines are 316 s).

I’m still not seeing where you need to dedicate more than around a quarter of the mass fraction, and that’s with the 1/sqrt(2) factor from the (apparent) 45 degree angling of the thrusters (so that they can have a continuous heat shield).

Conventional is exactly what we want, because it’s cheaper than tech that’s barely out of the lab.

As a general point, sure. But for a Mars effort to work, we need to take a step away from the tightly integrated systems that are so endemic to space travel. Earth tech is “easy” because our infrastructure is widespread, generic, and decoupled. Space tech is the exact opposite.

This isn’t about gumption and guile. To channel Musk: we must be careful to not reason from analogy, and instead reason from first principles. Reasoning by analogy goes like “all electric cars have been slow and low range; therefore our electric car will be slow and low range”. Reasoning by first principles goes like “lithium batteries have a power density of A, energy density of B, and we can physically fit C of them in a car body; from these numbers the car would accelerate at D and have E range.”

Others have thought more about the actual physical boundaries to what we can do, but from what I’ve seen so far, physical constrains aren’t the long pole. This is in contrast to a true Earth SSTO, where even from first principles it’s obviously a very hard problem. You do the math on the chemical propellants and it just looks very unfavorable all around. I have not seen the same hard problems in a Mars effort with more conventional tech.

I’d agree if the real cost was untold hundreds of billions. I don’t think that cost has been demonstrated yet for a one-way mission, which is obviously going to be far easier than a return mission.

Eventually we need to learn how to live on Mars. We also need to learn how to gather and process resources in space. Those are pretty distinct problems and there’s no reason we can’t do both (unless, of course, those problems cost a significant fraction of $1T to solve… again something that I don’t think has been demonstrated).

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Instead of going in tin cans like the Apollo program is it technologically possible (hang the expense) to build an actual space ship in orbit that would have the structural integrity to stand up to acceleration etc…, and be large enough to carry supplies, landing craft, shield the crew from radiation? An actual ship that could cruise back and forth. Seems we’d have to forget everything we’ve done in space up to now and start with a completely new direction.