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5 years of thrusting? can you please stop now?


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The amount of Xenon gas you would need to do that would be... A lot. It's over $100 per 100g of the material. While that may not sound too bad, we need to consider that it is considerably heavier than most other things. The further down the periodic table you go, the heavier you get. The differences are not subtle either.

Notwithstanding the cost would rise exponentially as noble gas ejected outside of the atmosphere is unrecoverable ^_^

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Notwithstanding the cost would rise exponentially as noble gas ejected outside of the atmosphere is unrecoverable ^_^

while xenon is the preferable gas for current ion propulsion pretty much any noble gas will do. some engines like mpdt can run on hydrogen. engines such as LiLFA, hall effect, feep can run on metals like lithium, bismuth, and caesium, respectively. ion engines are diverse and very flexible in what kind of propellants they can use.

Edited by Nuke
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Because human beings actually being there would be a monumental moment in history?

That's the point in and of itself, if we get some science done too that's just the icing on the cake. Humans are driven by achievement and discovery.

What planet have you been living on? Humans are driven by greed, narcissism, and prejudice.

We didn't go to the moon for "Achievement and Discovery," we went to the moon because those damn Commie Bastards were going to get there before us.

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I would much rather see money go to unmanned craft that can do the same science than a manned one at a fraction of the cost.

Currently such unmanned craft are the stuff of science fiction. You want a fraction of the cost, you get a fraction of the capability.

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Currently such unmanned craft are the stuff of science fiction. You want a fraction of the cost, you get a fraction of the capability.

So the Curiosity is science fiction?

man I can't stop laughing at your "You want a fraction of the cost, you get a fraction of the capability." like you never tried to find a cost effective solution to a problem. If we send a human geologist with the same laboratory the Curiosity has, will we get more science?, the cost would be many many more times the cost of the Curiosity, will it worth it? how many other stuff we could have done with the same money? What mission has more chances of failure? what would be the cost if the mission fails?

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while xenon is the preferable gas for current ion propulsion pretty much any noble gas will do. some engines like mpdt can run on hydrogen. engines such as LiLFA, hall effect, feep can run on metals like lithium, bismuth, and caesium, respectively. ion engines are diverse and very flexible in what kind of propellants they can use.

Those metals corrode the engine, because they react with the casing. xenon is (virtually) %100 inert, and so therefore it doesn't react with anything. However... it is a bit expensive, since (according to Scott Manley) 100 tonnes of atmosphere will yield about 1 kilogram of xenon. It's about $120 per 100 grams of pure Xenon. To put that in perspective, the Dawn spacecraft used 425 kg of xenon propellent, which would cost $510,000.

Edited by Themohawkninja
There was more xenon than I first read.
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If we send a human geologist with the same laboratory the Curiosity has, will we get more science?

Yes, we will get a lot more science. The biggest problem with robotic exploration is the light-time lag. A robot can't make on-the-spot decisions when presented with new information. It's possible we might have the technology to make robots which are autonomous enough, and whose circuitry can survive the trip to another planet, a few decades from now, but right now we don't. A human on the ground can make important decisions in real time instead of waiting several minutes for each command to come back from Earth. And the difference is enormous. A geologist on Mars could do in an hour what it takes the Curiosity rover a month to do with the same tools.

Anyway, human spaceflight was never about science. It's about exploration, prestige, inspiration, and extending humankind's reach into the cosmos. The Apollo astronauts did all those scientific experiments mostly just so they would have something to do while they were on the Moon, and because it looked good on camera. Science was never a top priority then. Sure a human mission to Mars might cost 50 times more than a robotic mission. The scientific return might not be 50 times as much (it will still be significant though), but science is not going to be the top priority for the mission.

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To put that in perspective, the Dawn spacecraft used 425 kg of xenon propellent, which would cost $510,000.

That is true, but that is only about 0.1% of the cost of the entire Dawn mission. So xenon is worth it even if its advantage over other elements is pretty small.

If we do ever need inexpensive ion engine fuel, we can always use krypton or argon, which are much cheaper, for only slightly worse performance.

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Yes, we will get a lot more science. The biggest problem with robotic exploration is the light-time lag. A robot can't make on-the-spot decisions when presented with new information.
A key capability in the new version is image processing to check for obstacles. This allows for longer drives by giving the rover more autonomy to identify and avoid potential hazards and drive along a safe path the rover identifies for itself.

http://www.nasa.gov/mission_pages/msl/news/msl20120810.html

As I said in another thread; we've had self driving cars since the 2000's and probably even earlier. I don't need to "google for pics" what I know are extremely simple algorithms. (I wouldn't be surprised seeing it done in the 1980's either; implementing the basic algorithms for driving are a good "college design project.")

The problem has always been unpredictable conditions; generally "other drivers." The complexity of the A.I. skyrockets when it has to PREDICT events occurring before they occur. In Curiosity's case, it doesn't need much intervention, and if it did it would just ask which subroutine to run; manual control would be an absolute last ditch effort.

The whole "RemoteTech" idea is preposterous. Why would anyone "pilot" it manually anyways? Send a data packet indicating the times at which to execute a behaviour (or better yet, call a subroutine to automatically make the calculations using onboard sensors) and then you can see it all happen in "delayed real time".

Hollywood's "Humanoid Robotics" has been masking the... well... applications of decades old technology. Curiosity should be able to operate its robotic arms and grab an item all on its own; we are not the only ones capable of doing such actions. But "humanoid robotics" are much dicier, making all the "hollywood mobility" is a level of complexity unto itself. (Let alone that you're placing the mass in all the wrong places.) Just because it looks like a rover, doesn't mean it cannot perform actions like a "SciFi Robot."

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We could give rovers more autonomy, but there are still some problems.

One is that more autonomy generally requires more computing power (at least for the input data analysis if not for the algorithms). And that requires more circuits/transistors. There is a problem here since these circuits have to be transported through interplanetary space for months to years, and to endure radiation and other dangers. Electronics used in space have to be radiation hardened, which makes them more redundant and less able to be miniaturized. This is why electronics in space are usually at least 10 years behind electronics on Earth.

Another problem is the risk involved. Curiosity might well be able to drive by itself for a short distance but cannot react to unforeseen circumstances. A self-driving car on Earth generally drives on flat asphalt with clearly delineated boundaries where the terrain is known, and might use GPS to know its position. None of those things apply on other planets. It cannot tell if the patch of brown dirt 10 feet away is a hard surface or a sand trap. It is impossible to program it to avoid all the hazards on Mars, when a lot of the hazards are unknown even by the programmers. When you consider that a single misstep of the rover can doom the entire mission, it makes sense that there are extensive controls from Earth operators, who can react to situations for which the rover was not programmed. And it is not just driving around, that's the easy part. It's also deciding what science to do. A computer can't currently tell that that rock over there looks odd and might require further investigation. That is the deciding advantage of humans over machines, at least for the next few decades: that humans can make decisions in unforeseen and unplanned situations.

It's likely that the 2020 Mars rover might have more autonomy than Curiosity does, and that will only go up in future missions. But we are still at least a couple of decades away from sending to another planet a probe which can act autonomously without significant human intervention.

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I don't really get the hate for Ion Engines. I mean really, we're going places that would be extremely hard to get to with chemical rockets for a fraction of the price. While most of you base your hate on them for their speed, does it really matter? It's not like there is some disaster impending where we would need to hop on over to Pluto, or any of the other outer planets. We've got all the time in the world, really.

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Those metals corrode the engine, because they react with the casing. xenon is (virtually) %100 inert, and so therefore it doesn't react with anything. However... it is a bit expensive, since (according to Scott Manley) 100 tonnes of atmosphere will yield about 1 kilogram of xenon. It's about $120 per 100 grams of pure Xenon. To put that in perspective, the Dawn spacecraft used 425 kg of xenon propellent, which would cost $510,000.

while the liquid metal engines do have their issues, argon and hydrogen based ion engines are still viable alternatives. i was merely trying to point out that xenon is not the only option for ion propulsion.

I don't really get the hate for Ion Engines. I mean really, we're going places that would be extremely hard to get to with chemical rockets for a fraction of the price. While most of you base your hate on them for their speed, does it really matter? It's not like there is some disaster impending where we would need to hop on over to Pluto, or any of the other outer planets. We've got all the time in the world, really.

with a chemical rocket you do a fast burn and then wait for days/weeks/months/years for your next maneuver. if you are going to do all that waiting anyway why not use that time to increase your velocity slowly with an ion engine. then you whole ship get lighter, fuel tankage decreases in size. i think the hate comes from the fact that people dont like flying them in ksp. you spend hours transferring a small satellite from kerbin to mun. but in the real world you just let the computer do the flying and monitor the telemetry for anomalies, a job for the intern.

Edited by Nuke
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So the Curiosity is science fiction?

No, Curiousuty is not science fiction. Nor is it as capable as a human. Let's look at Spirit and Opportunity - which *together* took years to cover the same amount of ground as the Apollo 17 rover did in a single *day*. Or the time (IIRC) Spirit took three *weeks* to maneuver around and get pictures of an unusual rock, something a human could do in three *minutes*. Etc... etc... This quote from Steve Squyres (If you don't know who he is, look him up) really puts it in perspective - "Spirit and Opportunity together accomplished in their first year what a human could accomplish in a long afternoon or maybe two".

Remote and automated operations are not nearly as advanced as the general public seems to believe. To take an example from a related field, military drones (which have money poured into their development, operations, and support by the bucketload) crash almost 10 times more often than manned military aircraft. (And no, that's not due to battle damage. Such damage to drones is extraordinarily rare.)

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Let's look at Spirit and Opportunity - which *together* took years to cover the same amount of ground as the Apollo 17 rover did in a single *day*.
I'm sorry, I thought we were discussing the science returned per dollars invested, not which would win the space Olympics.
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The disaster in mind is us and it is lowering the numbers on the clock exponentially.

And are we going to self destruct within the next 10-100 years? No, of course not. The Outer Space treaty proved that. If we have lasted this long since the invention of nuclear warheads, I don't see why we can't last any longer.

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I'm sorry, I thought we were discussing the science returned per dollars invested, not which would win the space Olympics.

Heck, Lunokhod 2 traveled further in less than five months than opportunity has in eight years. Therefore it returned more useful science, right?

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We have the knowledge and technology to do many things that are space related, unfortunately the majority of people who are in power have a very narrow mindset that follows the "if-it-doesn't-bring-profit/benefits-in-the-very-near-future-it-isn't-worth-doing" principle. We could have been to mars already, we could already have a permanently manned moon base, we could have/ be having a large scale interplanetary mission that involves sending a team of people around the solar system like in that one BBC documentary (2001 Space Odyssey or whatever its called), but our leaders decided that worthless money is more important than the future of mankind so thats why we still are so primitive in our society.

As a species and as a society at this point in time we are incredibly inefficient, ignorant and very self centered with no true purpose nor plan of what our future will behold.

Get rid of money and start investing more time and resources into science, especially Space related sciences.

*end of rant

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I'm sorry, I thought we were discussing the science returned per dollars invested, not which would win the space Olympics.

We *are* discussing the science returned, or at least I am. I'm not sure at all what you're discussing. So, just to even the playing field, I'll being you briefly up to speed;

Did you ever stop and think about why NASA flew rovers to the moon, and why they keep flying them to Mars rather them limiting themselves to a few hundred feet around the LEM or the reach of a lander's arm? Science is about observation and testing, and if you're tied to one spot there's a pretty low and sharp limit on how much of that you can do. The more you can observe, the faster you can process the observations, the faster you can get to interesting bits observed in the distance, the faster you can move around those interesting bits and decide where and what to examine in detail... All these factors add up.

It's not just all about the science package (which Lunokhod didn't carry much of, which you should have known, but snark is easier than knowledge), nor is just all about being able to move fast. It's the integration of all these things. Computers absolutely suck at doing this as compared to the human brain - which is why the Mars rovers have to send megabytes of pictures back daily just so the science and operations teams can spend hours and days trying to decide what the rover will do in an hour. Which is the Chief Scientist for Spirit and Opportunity favorably compared the years of work by the rovers to an afternoon's work by astronauts.

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why do you want bigger rockets? for send people to Mars and to do what? to pick some rocks and plant a flag? We aren't kerbals, I would much rather see money go to unmanned craft that can do the same science than a manned one at a fraction of the cost.

Honestly i just want humanity to get off this damn planet as soon as possible. Not send little robots everywhere.

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We *are* discussing the science returned, or at least I am. I'm not sure at all what you're discussing. So, just to even the playing field, I'll being you briefly up to speed;

Did you ever stop and think about why NASA flew rovers to the moon, and why they keep flying them to Mars rather them limiting themselves to a few hundred feet around the LEM or the reach of a lander's arm? Science is about observation and testing, and if you're tied to one spot there's a pretty low and sharp limit on how much of that you can do. The more you can observe, the faster you can process the observations, the faster you can get to interesting bits observed in the distance, the faster you can move around those interesting bits and decide where and what to examine in detail... All these factors add up.

It's not just all about the science package (which Lunokhod didn't carry much of, which you should have known, but snark is easier than knowledge), nor is just all about being able to move fast. It's the integration of all these things. Computers absolutely suck at doing this as compared to the human brain - which is why the Mars rovers have to send megabytes of pictures back daily just so the science and operations teams can spend hours and days trying to decide what the rover will do in an hour. Which is the Chief Scientist for Spirit and Opportunity favorably compared the years of work by the rovers to an afternoon's work by astronauts.

A human can't do any research by itself, it needs tools, its capability to do research is limited by the tools it has. If you put a human in Mars with the same laboratory the Curiosity has, it will do the same science the rover does, not more. You're right that it will do it at a much, much faster rate, but I question that the several orders of magnitude in cost will worth it.
Honestly i just want humanity to get off this damn planet as soon as possible. Not send little robots everywhere.
And go where? this is the only planet we can live on, and any colony we build in space will depend on Earth for a long, long time. We're facing great unsolved challenges right now, such as climate change, no suitable replacement for fossil fuels and the finite Earth problem. Any space dream you might have will depend on getting those problem resolved in a not so distant future. Edited by m4v
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And go where? this is the only planet we can live on, and any colony we build in space will depend on Earth for a long, long time. We're facing great unsolved challenges right now, such as climate change, no suitable replacement for fossil fuels and the finite Earth problem. Any space dream you might have will depend on getting those problem resolved in a not so long future.

But here's the other side of that coin: it has been proven, many times over, that the resources we want/need exist elsewhere in our solar system, in quantities that are undreamed of on Earth. And a (SMALL) self-sufficient colony "right off the bat" IS possible, given time for development and the requisite political willpower. As a thought experiment, consider the following:

1. A small crew (anywhere between 1 and 3 dozen colonists).

2. A high-density hydroponic agriculture system, such as is being developed for high-intensity urban farming RIGHT THIS MINUTE.

3. Some means of producing (or recycling) a breathable atmospheric mix (as already exists - see: submarine, space station).

4. Some means of producing (or extracting) drinkable/usable water (already exists).

5. Some means of producing power (solar/nuclear, already exists).

6. Some economic activity to make the colony, if not profitable, at least partially economically self-offsetting (for instance, mining valuable minerals or extracting hydrocarbons - for instance, Saturn's moon Titan has been known for some time to have SURFACE OCEANS of combustible hydrocarbons, and many near-Earth asteroids are believed to have platinum deposits with current market values well into the trillions of USD).

7. A low-gravity environment (moon or asteroid) on which to plant all this.

I maintain that all of these things EXIST, and have been demonstrated - the question is not of HOW, but WHEN. I present, thus, a potential (albeit rather crude, I'll admit) roadmap to such a colony existing within the next few decades.

1. Development of a low (or, at least, lower)-cost launch system than currently exists. See Skylon Project.

2. Development of orbital refuelling and spacecraft construction infrastructure. Orbital refuelling and construction are well-understood, and the only obstacle preventing these things is the high cost of trucking materials to space (see point 1).

3. Development of a system whereby a colony can be quickly and efficiently deployed, ready to start (the "colony ship"), with modular elements for different industrial payloads (mining, refining, etc.).

4. Construction of one or more of these colony ships using the orbital construction infrastructure from point 2.

6. Deployment of these ships on the target bodies.

7. Return of raw or processed resources to Earth for sale, using the orbital refuelling infrastructure (chemical, ion, doesn't particularly matter).

8. Use the newly acquired money to expand economic activity at the colony, and repeat steps 4-8 ad infinitum. As new resources are discovered, plant new colonies.

Total time to step 8 completion (given correct amount of political/corporate willpower and funding)? Approx. 4 decades. End result: a profitable (or nearly so) human colony on a non-Earth body, within one human lifetime from project inception.

And, FYI, some of the world's biggest billionares are, you guessed it, teaming up to perform such a venture, almost exactly along the roadmap I just described.

In the words of Randall Munroe,

"The universe is probably littered with one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision."

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And I suppose that your "self-sufficient" colony is going to produce its own high-tech spare parts when things break down? if their air filter breaks they will manufacture a new one? Self-sufficiency doesn't involve air and food only, it means that it doesn't need any aid or support for survive, and no colony that we can build now will survive without the support of Earth.

Anyway, what resources you're thinking to sell to Earth? There are abundant resources in space, yes, but getting them is not cheap, and I can't think in anything that you can't get here cheaper: If we're buying oil from Titan then oil prices must have gotten really really high, I would suppose that at that point alternative energy sources must be more attractive. Platinum is so expensive because is so rare, not because is needed, start selling an asteroid worth of platinum and its price will dramatically plunge.

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And I suppose that your "self-sufficient" colony is going to produce its own high-tech spare parts when things break down? if their air filter breaks they will manufacture a new one? Self-sufficiency doesn't involve air and food only, it means that it doesn't need any aid or support for survive, and no colony that we can build now will survive without the support of Earth.

Anyway, what resources you're thinking to sell to Earth? There are abundant resources in space, yes, but getting them is not cheap, and I can't think in anything that you can't get here cheaper: If we're buying oil from Titan then oil prices must have gotten really really high, I would suppose that at that point alternative energy sources must be more attractive. Platinum is so expensive because is so rare, not because is needed, start selling an asteroid worth of platinum and its price will dramatically plunge.

OK, fair point. For the initial push, bring along a set of spares for virtually every component, and design as many components as possible to be rugged and simple to service (an air exchanger, for instance, is nowhere near as complex as a rocket engine). In addition, bring along enough equipment such that your nascent colony could produce raw materials (for instance, steel) in at least small quantities for internal use (i.e. the manufacture of new/replacement components), in as autonomous a nature as possible. In addition, make sure you provide (at first, manual) machines and plenty of schematics for the colonists to have the ability to fabricate replacement parts. Now, I'm not advocating for complete, closed-system sustainability right off the bat - yes, you're right, that's impossible. But such a colony could MATURE into such a system within a matter of decades, especially if new colonists moved there, with new skills. There's even precedent for this - the American colonies became self-sustaining (though harsh) comparatively quickly. While, yes, such a feat would be more difficult under the hostile conditions of another planet, I still believe it to be doable, especially with sufficient political/business willpower back Earthside.

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