Follow Slashdot stories on Twitter


Forgot your password?

Comment Re:Even this is wrong (Score 1) 683

The turbopumps in rocket engines may be 'similar' to turbine engines in general, heck, they're the same thing, but they operate in a much more demanding regime, as do all the other components of rocket engines. Check out the temperatures and pressures involved, the power outputs per unit volume, etc. Its many times more than jets, and every ounce is that much more critical. We ARE very good at building them, but they never get really cheap, no matter how many you build. Again, the fundamental HUGE challenge is in terms of materials and mostly design margin, there's just not a lot of room to make stuff cheaper and have it still fly every time you push the button.

Musk is a great manager, but actually his claims in terms of cost reductions haven't materialized yet. He's still more expensive than the Russians were in the 1980's (in adjusted prices). It remains to be seen if he can do better than that. He's a very capable business man and he's done a great job of breaking into an established market, but it was one that really had too little competition and fat complacent US providers that were protected from their cheaper foreign competition. He's just brought the cheaper prices on shore, its far from a huge revolution.

And yes, Mars is about science, but the 2050 generation of rovers will not need to be driven from Earth, will know how to look for new and different stuff (and can of course still be guided by humans), will have greatly increased sample handling and instrumentation, etc. Is there ever going to be a point where a human is 1000x better than a rover? Where it is impossible to design a specific mission to answer a particular question? The cheaper manned spaceflight were to get, unmanned spaceflight will get cheaper even faster. So, is science really served by sending men to Mars? I have to wonder.

But the Moon... Eh, mostly you don't even need more advanced systems than we have now, we can sit on the ground and run machines there today. Why wait? While launch costs will still be high for any manned missions they WILL still be significantly less risky and each mission can be a single self-contained launch, which is a LOT easier to plan and budget and subject to less overruns. Launch windows are not an issue, etc. Its much more appealing at this stage of the game. I get that sending someone to Mars has this emotional appeal, and so maybe it will happen regardless of ANY logic, but the logic is tough to find.

Comment Re:Even this is wrong (Score 1) 683

No, turbine engines operate at an entirely lesser, though still quite significant, level of performance compared with rockets. Really, go study the engineering of rocket engines in detail, you will be quite startled. These are objects putting out gigawatts per cubic meter of power, they are well beyond anything else made by man, and approaching the limits of what physical matter can do.

The problem with imagining 1000's of launches is that near-Earth space simply cannot accept that much stuff. Maybe in some unguessable far future, but simply suggesting that because some other random prognostication was wrong doesn't have any bearing on anything else. Your's is at least as likely to be wrong as mine.

Yes, except X-33 and Venture Star somehow have never made it. I don't accept that what has not been done is possible, do it, that's the only real proof. I think it will be possible, but I worked on the fuel systems for stuff like this, and with the guys that tried to design the fuel systems for these craft, and failed. They weren't idiots, it was just not viable. They could have built SOMETHING, but the cost and operational characteristics simply weren't worth it. That should tell you something.

There is no 10x improvement possible with rockets, you, and many other people, are simply deluded if they think so. 2x, maybe in time 5x, and then you've run to the final limits. I know Musk keeps claiming otherwise, but he still hasn't even caught up to where the Russians have been stuck for 20 years. 'These other technologies' are not even established to be possible. Not even close to established. We have VERY hard, maybe too hard, control systems, materials, energy generation/storage/distribution, etc problems to solve in all cases. There are a few different approaches, I think one or another may pan out, but then the question is will it REALLY be cheaper and more efficient, or are we just fooling ourselves because we haven't really got down to the details, where the devil is as we say. I suspect we'll find that some one of these ideas works, for a certain class of launches, and provides some sort of advantages, but 10x to 100x? Show me!

Look, we're not talking about colonists here. Nobody is EVER colonizing Mars, its a hell, nobody will want to live there. This is about science. For that, yes, I believe that someday men MAY set foot on Mars. I think its quite likely that some will make their way to the Moon, and other nearby places. OTOH I'm actually skeptical of the whole notion of permanent settlement anywhere off Earth. We're poorly adapted for it, and there isn't a real compelling argument. 50 years hence what I see is automation technology and machines in general being sophisticated enough to obviate the real need. Again, who knows what will happen far into the unknowable future, maybe we'll be so rich and capable that people will travel the Solar System just for a lark, or other less pressing reasons will be enough at that point, I don't know.

Comment Re:Even this is wrong (Score 1) 683

The problem with rockets is they operate at temperatures and pressures very near the uttermost physical limits of material objects. I've worked on some, though only in very small aspects. I recall we built the telemetry/self-destruct unit for the final generation of Titan SLVs (34D and IV IIRC). The electronics were a heavy board, mounted inside a block hogged from solid aluminum with 5CM thick sides and 5CM thick top and bottom plates lagged to it, with epoxy filling the whole thing. That's what it takes just for a piece of electronics to survive the massive vibrations and stresses of launch. Now, think about what the engine bell housing is subjected to, 5000C gas flows at 1000's atmosphere's of pressure, sound pressure levels that can't really be measured in DB. The shock wave from ignition of the SSMEs on the shuttle stack has to be absorbed by a pool of water the size of a large office building, otherwise it would reflect back off the ground and tear the entire stack into little bits. This is all just what is minimally necessary for big rockets. They will ALWAYS be very expensive. The Russians/Chinese/Indians/SpaceX can maybe chip away the costs to say 50% of what it costs ULA or NASA right now, but beyond that you just can't go because you can't make rockets out of cheap materials or skimp on QA very much before they just blow up on the pad. 'Volume' is supposed to be the key, but its hard to argue that the demand for 100's or 1000's of launches per year will ever exist.

As for loops and fountains, and bolos and etc. All very nice ideas, but none of them is anywhere close to realization. We don't know if any of them will ever work, and the costs to build a production system are much higher than the costs of a Mars program! I sort of feel like SOMETHING will happen at some point, technology seems to march on and materials will get cheaper, so will manufacturing, and some ideas ALMOST seem doable, like EM launchers, ground-based laser or even gun propulsion (IE not putting the fuel on the rocket, but its still a rocket). These would answer SOME needs, and presumably something will happen. Maybe an SSTO will become possible and practical in 50 years with advanced materials.

I agree, the Moon is one of many options, but don't discount the value of being close. You put a huge weight on energy, but real access to space in a big way will already have to rely on abundant energy. TIME however, is irreplaceable. I think its a choice between the Moon, and NEOs really. At least in the medium term. 300 years from now anything might be possible, but nobody can predict that.

Comment Re:Even this is wrong (Score 1) 683

ISS was a necessary step, as it has greatly advanced our long-duration expertise and general operations capabilities that will be needed regardless of if you are in Earth orbit or not.

The fundamental thing that people don't understand, even space people, is that space is NOT going to really get cheaper. Rockets are just barely possible, they exist at the outside edges of feasible engineering. The shuttle is more expensive that S-IV, which was more expensive than what came before, and SLS will be more expensive than shuttle because more capabilities cost more money. While you might think you just 'get better at it' space is so exacting, so bleeding hard that NASA was pretty much as good at it in 1968 as they were ever going to get. Yes, SpaceX can do some incremental ratcheting down of prices, but they're not really cheaper than the Russians, the Chinese, or the Indians have been for decades. People need to stop holding their breath for cheaper launch costs, until we have some entirely new type of system, some HUGE increase in launches (which right now would rapidly fill LEO and adjacent areas with space junk and end ALL launches) or stop launching lots of mass into space and produce it somewhere else its not getting a LOT cheaper. The options there are Lunar resources and NEOs, take your pick.

Since we need to go the Moon anyway, we might as well go now and get the process in motion. It means in EVENTUALLY, in the long-term, we'll have cheaper access to the rest of the Solar System, but the longer we wait the further in the future that will be.

Comment Re:Even this is wrong (Score 1) 683

The Moon has an advantage of at least 1.4 km/s of delta-V over Mars, surface-to-surface. Some of that may be mitigated by aero-braking but that requires extra equipment, which itself imposes extra costs. Also delta-V to Mars is much more expensive as mission mass must be considerably higher to start with, so blind quotations of 'delta-V is about the same' are nearly meaningless. Given that missions to Mars and the Moon would have significantly different objectives in many cases they simply cannot be compared one with the other.

Cost estimates generated by the engineering teams at NASA in 1961 for the Lunar surface were about $7 billion (in then-current $), actual program costs through Apollo 11 were about $21 billion (which was almost exactly what NASA administration reported to Congress as an actual total program cost estimate through simply guessing an underestimation factor, you can read all about this subject, it is touched on in the Wikipedia Apollo Project page). Assuming roughly similar cost factors but with somewhat lower underestimates for Lunar operations due to fewer unknowns we can estimate permanent operations on the Lunar surface can be initiated in the range of $100-150 billion. Applying the Apollo factor of 3 to Zubrin's estimates for a simple 4-man short-stay at Mars we get $165 billion. In other words the costs would be expected to be in the same range, with the Lunar project resulting in a permanent manned presence and some production of materials (besides just CH4 and O2) on an ongoing basis. Such a base can also be efficiently tele-operated from Earth, and follow up missions are relatively inexpensive. Any cost savings from the "SpaceX effect" would accrue equally to either program.

As for the Sabatier reaction, etc. Yes, its simple, but your car, as you use as an example piece of equipment, surely will not operate continuously for 2 years without maintenance, certainly not with 100% reliability. Nor are these kinds of chemistries fool-proof. Some nice perchlorate-laden Mars fines could be a really nice addition to that mix, but not so nice if you want CH4... Likewise O2 harvesting requires not only electrolysis but also catalysts, which could be damaged, compressors, which can wear out or fail, etc. All of this equipment is subject on Mars to penetration by exceedingly fine and highly reactive dust. Now, we know our equipment seems to stand up to it reasonably well, but its not just something you can take for granted. And yes, if you have a failure you can of course simply pay a lot of money to stretch out your program, figure out what went wrong (hopefully), fix it, and launch another. None of those possible costs is factored in by Zubrin, but a two-year program delay easily adds billions, and there's almost bound to be one.

I don't care how 'harshly critical' Zubrin is of a Moon Base, he's not objective about it. Just because someone is an engineer doesn't make them objective or unbiased about everything. There are PLENTY of other engineers who've come to the opposite conclusion. Given all the factors it makes more sense to take the smaller steps first and the bigger steps later.

As expensive as Mars is now, it will SURELY be much cheaper over time, correct? A manned Mars mission in the 2050 time frame could easily be 1/3 or 1/4 of the cost of one carried out in the 2030 time frame. Mars isn't going away.

Comment Re:Even this is wrong (Score 1) 683

No, what I'm saying is that Lunar Regolith Processing (ISRU on the Moon generally) is not on any critical path. Its something that we will WANT to do, but it can be developed over time starting with small experiments. If it produces some consumables, great, if it doesn't there's a 3 day transit time for a cargo lander, big deal. There's no working prototype of a Martian ISRU unit either. I'm a chemist my friend. Let me tell you, until you do the chemistry in exactly the place and conditions, you haven't done the chemistry. I don't think its going to be the hardest thing to do, but Lunar ISRU also has many other potential extra benefits that Martial ISRU doesn't, regolith is going to need to be handled in either case eventually, for shielding, construction materials, etc. So it makes perfectly good sense to do it on the Moon first, where a teleoperated robot is a perfectly sensible option. No need to have a guy on site at all.

Actually polar orbits are quite good for both landing on and leaving the Moon, you might want to study that....

Nobody is saying that a polar base is the be-all and end-all of Lunar bases, any more than any given base on Mars would be.

As for 'stricter requirements', again the issue is that your margin for errors is smaller when you are operating at the end of a 20 minute communications lag and a 9 month turn-around time. Just look at Apollo 13, the equivalent failure on a Mars mission is loss of spacecraft with all crew. Its much dicier and risks have to be reduced further in consequence to achieve similar mission success rates.

Comment Re:Even this is wrong (Score 1) 683

AGAIN, you are wrong about Apollo. Just go read the Wikipedia page on Project Apollo and you will learn a HUGE amount about it. Every aspect was tested in unmanned flights to a high degree. Apollo 3-6 as well as 3 early unnumbered development flights were all unmanned test flights in which the CM, SM, CSM as an integrated vehicle, and the LEM were all tested under space conditions. In fact Apollo 6 was intended to travel to the Moon as an automated spacecraft and undertake operations there, including direct abort testing, descent, rondezvous, docking, and an actual reentry from Lunar space were planned. A series of 3 engine failures resulted in that plan being cut back, but most of the tests were still conducted and changes made in later spacecraft based on them. Apollo 7-10 all included extensive testing. Apollo 7 was IIRC a full manned test of the CSM and the first manned Apollo flight. Apollo 8 was a manned journey to the Moon and back, testing out all phases of CSM operations in Cis-Lunar space, including some of the functions of the LEM. Apollo 9 was a full-up test of all LEM functions carried out in Earth orbit, except obviously for the actual descent and landing. Apollo 10 tested EVERY aspect of the mission short of actual final approach and touchdown. The only part of Apollo 11 that was a completely new untested aspect was the final approach and actual touchdown of the LEM, an operation which was very similar to that carried out by a whole sequence of unmanned Surveyor spacecraft (some of which included ascent capability as well). Nobody is pretending there wasn't considerable risk involved, but in case was any piece of hardware utilized for the first time in a mission-critical manned application, and EVERY piece was subject to review and redesign based on the lessons learned from unmanned and non-mission-critical manned testing.

Its also useful to note how compressed Apollo was. Much of its aggressive timeline was dictated by politics, not best engineering practice. It would be much more prudent, and probably more cost-effective in the long run, to do more thorough testing over a longer time frame with a Mars program.

And again with ISRU, all it takes is one factor we haven't counted on to gum up an ISRU attempt. Yes, that won't risk anyone's life, but its quite likely that the first attempt will be marginal or even unsuccessful, and thus we should expect to make more than one attempt.

You also have NOT read the LAT (Lunar Architecture Team) materials. Your assumptions about operations on the Moon are just WRONG in many respects. At the South Pole of the Moon sunlight is available for long periods of time, and in a relatively small area there are always spots where solar power will work, without any gaps. The current design calls for a modular 10kw solar panel array and an ion exchange power cell that requires 2kw to charge and can put out 2kw at 30% duty cycle. This allows an array plus 3 power cells to put out 6kw continuous 100% duty cycle. Each lander would carry this equipment, including both manned and cargo landers. ISRU would obviously be required AT SOME POINT, but isn't a critical part of the plan at any time in the first 10 years. Certainly digging up 50 grams a minute of regolith at 50% duty cycle and extracting its volatiles is not THAT much of a challenge, and would drastically cut back on costs. Any smaller amount would be cost-effective as well, and the whole system needs only 1% efficiency to be worthwhile. It is believed that 10% efficiency should be achievable with first-generation, and 50% efficiency with further iterations.

As for the utility of the Moon, it has abundant useful materials and its gravity is quite limited. Small railguns can place materials into Earth orbit, even building a beanstalk is well-within our existing capabilities if we so choose. It might turn out that near-Earth asteroids work out as more economical, but we just don't know. They certainly are much more remote, with all the extra time and automation issues that remote operations entail (many of these asteroids can be as much as 20 light-minutes from Earth during large spans of time). I think it behooves us to at least land at and thoroughly explore an area of the Lunar South Pole and determine what the value of a base there might be. ANY experience gained will be highly useful later.

Comment Re:Even this is wrong (Score 1) 683

1. There's quite a bit of debate about this 'Dragon can just land on Mars' thing. First of all it hasn't even landed ANYWHERE yet. Secondly only back-of-the-envelope calculations have been done, that's a far cry from a working landing system. It will require at least 2, maybe 3 unmanned attempts to man-rate such a system. That's several years of just flight time, which can't overlap. MRV/MAV and Hab modules would be MUCH heavier, nobody has determined exactly how to land those.

2. You are utterly incorrect about Apollo. Apollo's systems and technology were incrementally developed and tested in 26 Mercury Program missions (6 manned, 20 unmanned), and 10 manned missions of Project Gemini, which were explicitly used to develop and test each of the necessary steps required by Apollo (long duration flight, EVA, rondezvous and docking, etc.). This was followed by ELEVEN developmental Apollo missions (10 if you don't count Apollo 1) which tested ALL phases of the spacecraft and operations right up to Apollo 10 flying to within 15km of the Lunar surface and exercising every single component of the Apollo system short of the legs on the LEM. This was an intensive 9 year program consisting of almost 50 launches before Apollo 11.

Yes, I've read Zubrin, etc. I think they somewhat underestimate the difficulties that will ACTUALLY adhere to a program. It is always easy when you are just 'moon shotting' some engineering problem. Its always 4x harder when you have to do the actual engineering of the real hardware that men's lives depend on. I been there. Multiply by 3 and that's your optimistic end of reality.

And to be clear, again, I don't think it is impossible. I don't disagree with Zubrin at the level of "we basically know how to do it to a first approximation", of course we do. No challenge exists here that is fundamentally insurmountable, but an awesome number of challenges still exist, and the distance and mission time multiply the difficulties, risks, and dangers in ways that are difficult to quantify. I want to see the whole exercise proven out on our doorstep. The Moon is a massive gift, a stepping stone to space, our door stoop, use it.

Comment Sounds good to me! (Score 1) 130

I'm sure there's details that would change in reality of course, but I don't see where this is wrong at any basic conceptual level. I think we should built some NTR/NER 'tug' vehicles that can move heavy stuff around autonomously and move materials where we need/want them. Maybe starting on the Lunar surface makes more sense, I'm not entirely sure what order is most efficient, but the elements all seem right at least. NASA's LAT and Lunar mission planning is pretty advanced. We could DEFINITELY be at the south pole of the Moon in 5 years without even breaking a sweat, and have a manned base up and running by year 10.

Comment Re:Even this is wrong (Score 1) 683

Its hard to have a basis for this discussion when you have no idea what sorts of masses would need to be landed on Mars for instance. Curiosity masses 900kg, which wouldn't even come close to the mass of a manned Mars lander. The Apollo Lunar Module (LEM) massed 15,200 kg with a crew capacity of 2. It would require a MUCH more massive craft to descend to the surface of Mars and ascend again. Even granting ISRU obviated the need for ascent fuel such a craft still has to land on the much larger Mars, deal with its atmosphere, etc. Lets just be generous and assume it is no larger than the LEM, it is still 10x more massive than anything ever landed on Mars before, and thus requires a completely new entry system. Since this entry system will be significantly different from previous ones, and must be man-rated to boot it will require multiple actual tests at Mars to perfect and validate the design. These are the types of actual engineering details that have to be considered when you go from speculating and dreaming about Mars missions, or publishing idealized mission profiles, to actually implementing them.

You really think you can just design and test a machine on Earth and it will 'just work' on Mars?!?!? You clearly don't know squat about engineering things. There are a million reasons why a machine we invent on Earth might not work well, or at all, or break down quickly, etc on Mars. Many unknown factors, and many chances for error. It is exceedingly naive to believe that you will just invent and build an ISRU unit and it will 'just work'. It will have to be iterated several times, and each iteration is a several year process simply because that's as fast as launch windows open.

And remember, 50% of all robotic missions to Mars have failed before reaching orbit/touchdown. There's going to be a pretty large loss rate. Maybe its only 25%, we're getting better, but with larger, more complex and untried spacecraft my bet is that the loss rate will remain quite high. No plan I have yet seen factors any of these realistic considerations into account. They are all highly optimistic and thus IMHO likely to run into serious problems.

I think something LIKE Mars Direct might be a good plan, but the idea that we 'have the technology' and its all just off-the-shelf, build it, fire it towards Mars, and watch everything go to plan, is very very naive. I don't really think the people who came up with the plan even believe it literally. I think they created it as a sort of baseline, a blueprint to say "these are the elements", but the actual implementation will be FAR more involved than they have stated. Its just you can't say that, it becomes monetarily infeasible and you need to spin it like you can do it. Once a program is started and lots of prestige and money sunk in it then the problems are more likely to be worked through vs to scratch the whole thing.

Comment Actually Not (Score 1) 130

Its in fact a very modest program that has only maybe a 30% chance of success as conceived, I'd say (assuming its carried through as planned, I'm talking about mission/technical risk, not political risk). Probably 70% chance of issues leading to massive cost increases to deal with unknown hazards/issues/requirements. Then even if you launch something on this agenda, there's a pretty good chance it isn't going to get where you sent it with a functioning crew, lander, etc. 2039 is only 24 years, BARELY enough time to iterate enough deep space manned missions (all those trips to 'cis-lunar space') to sort out the deep space mission issues. I think if they spent 5x more, then 24 years would probably be pretty adequate, but...

And the end result is going to be what? A few weeks on the surface of Mars? Stuck in one small area of the planet? What's the total program cost? Divide that by the cost of Curiosity, and see what it buys you.

Comment Re:Even this is wrong (Score 1) 683

Delta-V is FAR from the only issue, you have to have upper stages for Mars injection that are long-term storable, and stages of that size that can operate after a year in space haven't even been built yet, nor ever tested. Mars has much higher gravity than the Moon, meaning you must send much more mass, thus much more expense. These expenses grow GEOMETRICALLY with mission mass.

ISRU is a wonderful concept. So how are you going to test it and perfect it and insure with complete certainty that it actually works? You're going to have to send equipment to Mars, test it, iterate that design, send it again, test it again, etc until you have a working facility on the planet, plus probably a backup facility, before you even send the first men. That's going to require a bunch of heavy equipment and its ancillary propulsion and landing equipment, launched a number of times over a period of years. I predict that using ISRU will itself add 10 years to the timeline and thus increase total program costs substantially. Maybe enough to negate its entire advantage (though it may prove to be technically infeasible to do without at any cost).

The notion that the Moon isn't drastically easier, from a total program standpoint, is naive at best. Equipment sent to the Moon can be operated telerobotically from Earth without any issues, any ISRU or other equipment sent to Mars will have to be operated from a vast distance and probably semi-autonomous, a capability we utterly lack. If something fails on the Moon you can send the replacement in 3 days. It takes 3 YEARS to send a replacement to Mars.

I think in theory it is conceivable that we could 'damn the torpedoes' and get a guy onto the surface of Mars in 20 years. It will cost 100x what building a small Moon base will cost, just to set foot there, and then what? He just comes right home again? With a few samples that the rover we are sending in 2020 could collect at 1/1000th the cost? Its just not the way to efficiently and logically approach the human presence in space. Spending $30 trillion just to plant a flag is too much even for me, and I'm not an opponent of manned space exploration. What I fear is that we will try to do this, and get mired in something hopelessly expensive with such limited ultimate returns that the whole notion will be abandoned forever.

Comment Re:Even this is wrong (Score 1) 683

I've lived and breathed aerospace my whole life. My father worked on this stuff, I worked in the industry myself. I have a very good idea what the engineering is about and what the tasks are and how its done.

You need to get down to the details of the actual engineering to see why its harder. First of all long-endurance deep-space is going to be pretty tricky. You have to keep your craft operating PERFECTLY for realistically on the order of 2 years in space. Nobody has done that, and its an incremental task to do where there's no exact "its good enough." In fact it can't BE good enough, and we won't even be able to measure the risk without years of operating such systems. Every single component of the Apollo program was tested fully in its actual configuration and under actual mission conditions before Apollo 11 went to the Moon. With a Mars mission testing a 2 year endurance spacecraft takes TWO YEARS, at least, and then you have to go do it again, and again.

Landing is its own problem and is MUCH MUCH harder than landing on the Moon. Mars has a considerably greater amount of gravity, and approach velocities are nearly an order of magnitude higher. Plus you have an atmosphere, just thick enough to kill you and not thick enough to slow you down to a safe velocity. Its a HARD place to land. While we certainly understand this and we CAN obviously design systems to do the job, again testing them takes a long time and is very expensive. This is MUCH more difficult than the Moon where relatively cheap rockets could chuck landers at the thing all day until we stuck a couple landings, and then we learned from those and with often 2 months turn-around sent the next one. Read up on the Ranger and Surveyor programs. The problem with Mars is NONE of the landers we have sent will work for a manned mission, they can't just be scaled up. LEM was very much a scaled up Surveyor in essence, the lessons were directly applicable. Even the latest rover's landing system can't be adapted for manned missions to Mars.

And Heinlein, bless his soul, is just wrong. Energy is one thing, and being in orbit may be 'halfway to Mars' in that sense, but rocket technology is the LEAST of our hurdles getting to Mars. Yet even our existing rocket tech is BARELY adequate to the task. We really need an NTR or NER so that we can send adequately sized payloads to Mars and back for reasonable money, and a source of in-orbit reaction mass for them.

I predict no manned activity at Mars prior to the initiation of industrial activity in Earth orbit, and I suspect we're 30 years away from that, if not 50.

Comment Exactly (Score 1) 683

We can't even live off the land on a frozen continent that's what, an 8 hour air trip from civilization? Nor does anyone WANT to live there permanently.

I'm sure a few people THINK they want to 'live on Mars', but almost none of them really do if you ask me. Nobody is going to create a colony there, probably ever, certainly not for centuries.

A bug in the hand is better than one as yet undetected.