What "all purpose robot"? A robot or person's capabilities are limited by what scientific equipment they have on hand, not by whether they can digest corn or catch a cold. I'm talking about a robot like Curiosity. A person could mass-manufacture and dispatch a hundred Curiosity rovers to every corner of Mars for the cost of one manned mission and would collect dozens of times more data.

Ref. It took 30 seconds. Please don't ask other people to use Google for you, you're (presumedly) an adult and should be able to manage these sort of things on your own.

But in order to avoid thermalizing your fission fragments the reaction is going to need to be in near-vacuum

The reaction is done in a near vacuum. But that doesn't mean that there's almost no fuel. Fission fragments and neutrons behave totally differently, fission fragments are positively charged and respect Lorenz force, neutrons are neutral and do not, so it's easy to separate the two (as well as from the fuel, which becomes negatively charged and is not moving at relativistic velocities).

These things have been fully simulated, there's nothing unreasonable about them.

but our best neutron mirrors can only get total reflectance at angles of incidence of less than a single degree

I have no clue where this is coming from. Neutron reflectors (more properly thought of as scatterers) can scatter back, and in fact moderators produce a relatively anisotropic thermal neutron flux. The current proposal for a dusty fission fragment reactor involves U235 fuel and a moderator in the shell of the reactor.

Oh please, be serious. It's humans running the robots who make the decisions. The only benefit a human on Mars has is latency. But that's a really silly benefit, given that there's no urgency to get the data and just travel there takes months and the limiting factor on how much data you'll collect overall is how long your scientific equipment lasts. And no, an astronaut on Mars isn't going to be repairing a broken mass spectrometer or the like, it's a silly concept. And it'd, as noted, be orders of magnitude cheaper just to send a second robot.

I am correct, look it up if you don't believe me. The energy is primarily in the form of fission fragments. And no, chain reactions work exactly the same, the neutronicity doesn't vary. You're confusing fission fragments and neutrons.

I don't have anything backwards. As far as solar sails go, interplanetary travel is short distance.

The thrust is really, really, really tiny, for really, really, really huge sails.

I prefer the OS X method of window/application switching. But more to the point, I think expose is a better method than the alt-tab method, straight up. You can do it for all windows or just the application you're in. I've always found it faster. It's something I miss when I'm on other systems. (I've tried the Windows versions, but I've yet to find one that's nearly as good.)

You may want to look into uBar (ubarapp.com)--I've heard good things about it. I'm considering it myself, though I've never had problems with the dock.

Different systems have different control paradigms. The fact that things don't work the way you expect doesn't mean they're bad, just that they're different.

For instance, cycling through open applications makes a lot more sense to me. I really like that I can raise a single window without bringing the entire application to the front. This is something that consistently infuriates me in Windows with certain applications. I also like that an inactive window that you have your cursor in will still respond to the scroll wheel. (I know that's something that works in most XWindows window managers, but it doesn't in my Windows work environment.)

Anyway, a lot of the functionality can be hidden, but that's why Macs are popular among us that are buying computers for other people. Most of what you want is available in some form or another. You may have to learn some new tricks, just as I'd have to relearn a bunch of tricks if I went back to Linux or OpenBSD. Context switches are never free.

I totally disagree. A dusty fission fragment reactor has been demonstrated using a non-nuclear substitute fuel, which demonstrated proper containment and thermal management. And modelling shows that such a configuration should produce a collimated fission fragment beam. So what's so grossly impractical? Have you come across a paper indicating that it's impractical? Because I sure haven't.

My previous comments apply to NEP

I'm not talking about NEP. I'm talking about generating a RF plasma and funnelling it through a nozzle, like in VASIMR, but with primary heating being from an IR nuclear lightbulb. And even if I wasn't, commentary on conventional nuclear reactors vs. solar is inapplicable when one is talking about totally different type of reactor.

Hmm... I'm not sure what you're thinking about doing with CAD, but a Sim that handles real inorganic (and potentially simple organic) chemistry and materials properties could be incredible for enabling the crowd-sourcing of simplifying the tech chains of refining and production, which on earth are just ridiculously long and totally impractical to just migrate to Mars. The users would be given a realistic distribution of raw Martian minerals, and would have to feed the 3d printers / molders / CNC machines / lithography / robotic assembly that makes products. These products would include a (long) fixed set of needs to keep colonists alive and comfortable, as well as spare parts for your refining / mining equipment and the manufacturing hardware's equipment. Users could then try to produce as much of a colony's needs as possible with as little imported hardware as possible.

Simulating wear and corrosion on the refining, transport, and mining hardware would be a must. I think requiring the users to design the full details of the 3d printing and other manufacturing hardware would be overkill, but they should be able to choose what materials different "major parts" for them are made out of and what they want to supply as raw materials, which would affect wear / corrosion rates / efficiency / etc. Game consultants should include a wide range of people with real-world experience in different industries to make sure it's realistic, and the game should be launched with a variety of real-world pieces of Earth mining and refining hardware so that new players have something to start out with and tweak (albeit starting out heavily reliant on imports from Earth). As each person designs a new piece of hardware and tries it out, it should be saved to a global database, along with a history of what it's been taking in (raw materials, parts, etc) and producing as an outputs. Others could then search through the global database for equipment that does a function that they need to incorporate into their hardware.

The game could run in a MMO mode or single-user sandbox mode. In MMO mode there would be multiple users each with their own mine, refining center, manufacturing center, or whatever they want to build) on Mars, while in single-user mode a user would have their own whole planet to play with on their own. Once they get a production line running they can dispatch transport to carry materials or goods to where they're needed, there can be mishaps along the way, etc - all of the elements of your typical enjoyable Sim game - except with real-world chemistry and mechanical properties underlying key aspects. The victory condition would be total manufacturing indepence from Earth. The loss condition would be overstraining Earth's ability to supply you, leading to shortages and colonist deaths.

I think something like that could, if well designed, be both potentially fun for users and useful for engineers designing real-world infrastructure.

Great! Now you just need to invent an actually functional confinement method for the absurdly-hot gaseous/plasma nuclear fuel to stop it from destroying its containment vessel or leaking out its fuel in short order. And while you're at it, you should probably go ahead and invent a way to stop the quartz / fused silica bulb from undergoing blackening when exposed to a neutron flux, something it's so prone to doing that people deliberately expose quartz to nuclear reactors to make opaque black quartz for jewelry. And of course, a way to start the whole thing, a process that's been so problematic that they've been investigating bombardment by sizeable amounts of bloody antimatter as a potential solution.

Easy as pie, surely! Riiight around the corner.

What isotope are you thinking of as fuel? Unicorn-235?

The shuttle wasn't thrown away, nor were the boosters - only the (rather simple) ET. How did that work out, price-wise?

It's simply not fair to pretend that launch costs are a minor issue. They are the limiting factor, and progress in reducing costs has been lethargic over the past decades. "in orbit operations" are expensive precisely because launch costs are so high. Bargain basement, pay-out-the-nose-for-insurance launch rates are $4-5k a kilogram. More typical Russian rates are about $6-7k, while typical US and European rates run about $10k. And that's for large payloads, for small payloads expect in the (very) rough ballpark of $20k. How do you expect to live affordably in space if launch costs are even within an order of magnitude of that?

That's not to say that rockets fundamentally can't provide cheap access to space. But today's rockets certainly can't.

Presently working or theoretical? If you want "presently working", then that would defeat the point of asking for suggestions, would it not? If you want theoretical, there's tons. I kind of like the Launch Loop concept - sort of like a space elevator except that it doesn't require unobtanium, avoids or reduces the countless other problems with space elevators (micrometeorite damage, oscillation modes, power transfer, lightning and ionospheric discharge, and about 50 other things), and it gives you much more ideal/customizable orbital momentum, plus is 1-2 orders of magnitude more energy efficient at lifting cargo (space elevator climbers have to rely on beamed power, there's no practical way to send it through the cable, and beamed power over great distances where one receiver is only a few square meters at best is very low efficiency) AND offers a far higher launch rate.

Earth-based space elevators, the stuff of sci-fi nerd dreams, really are an awful solution when you start looking at the details. There's far better solutions out there.

Space has resources. They're called asteroids. Often quite valuable resources, actually - although learning to mine in microgravity will be a trial-and-error process.

Let's be honest, the main sellable goods of a Martian colony would be martian minerals for the jewelry / collector industry (which would sell for many times their weight in gold... a fundamental requirement of martian exports, given the cost of return payload deliveries) and tourist trips for the few multi-billionaires obsessed with space. It's hard to envision in even the medium term much more coming from a Mars colony than that which could pay for itself. And these things wouldn't come close to paying for the cost of the colony, in any regard. I certainly don't expect to see, say, industrial minerals exports in the medium term; a "creative economy" means people which means ridiculously high upkeep costs; and the concept of martian manufacturing being competitive with Earth's is just laughable. And science is much more cheaply done with disposable robots. One could probably factory-produce a hundred Curiosity rovers and mass launch/land them in every corner of Mars for the cost of one manned mission (let alone a "colony"). One could probably launch an automated nuclear submersible-drillship into the oceans of Europa for less than the price of one manned Mars mission.

If you thermalize your fission fragments. Sure, that's what all current fission reactors do, but it's not a fundamental requirement. About 80% of a nuclear reaction's energy is in the form of fission fragments - high energy heavy ions - which can be decelerated for power without Carnot losses, without a thermodynamic sink. The key is that you can't use fuel elements with any serious thickness to them (otherwise most fragments will thermalize) - the fuel elements have to be wires, sheets, dust, things of that nature, with magnetic fields to separate the fragments from the fuel.