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Forget Space Travel, It's Just a Dream
An anonymous reader writes "The clash of two titans — physics and chemistry — are major barriers to human space travel to Mars and beyond, and may well make it impossible ... at least with current technologies."
Most people have no real appreciation of the scale involved in psace travel. As daunting as our own solar system is, even that pales in comparison to the scales involved in traveling to other solar systems. Currently it takes us about 9 years for a probe to reach Pluto. When I ask people to guess how long it would take that same probe to reach the nearest solar system (a mere 4.2 light years away), people's estimates are usually comically far off.
120,000 years is the correct answer. Most people guess between 100-1000. That's why people think it is plausible for mankind to colonize space. They don't appreciate the scale we're talking about.
SJW: Someone who has run out of real oppression, and has to fake it.
The problem (for biological things, like human beings) is going out of Earth magnetic shield.
There are fully contained nuclear rockets. They are called gas core nuclear rockets, or nuclear light bulbs. The reaction uses uranium hexafluoride gas, spun into a vortex. This vortex is contained within a sealed, quartz walled chamber. The reaction produces a lot of UV radiation. Quartz is transparent to the UV radiation, so it escapes the container. Propellant is run past the quartz wall and absorbs the UV radiation, and heats up, expanding in the process. Voila, a nuclear rocket with no radioactive exhaust.
When our name is on the back of your car, we're behind you all the way!
http://en.wikipedia.org/wiki/Mars_Direct
http://en.wikipedia.org/wiki/Mars_for_Less
Or try this, if you are more partial to video.
And then... there's the colonization option.
Best part is, no unobtainium needed. Everything is based on current, tried technologies already in use.
Mit der Dummheit kämpfen Götter selbst vergebens
Yes, the GPP's numbers are definitely off. We had astronauts spend four days each way on the moon missions, so it isn't quite as bad as that. I do recall reading though that a trip to the outer planets of our solar system with our current technology would leave the astronaut quite damaged by radiation. This is pretty old news, BTW, and TFS reads like some sci-fi fan just got his bubble popped after learning a few facts. Kinda cute, but on the front page of slashdot it just gives all the "/. == digg" complainers more ammunition. As if they needed it...
Caveat Utilitor
Yes, of course you're entirely correct; whole body exposure to 10 Sv is lethal. Your parent is way, way off.
From your parent's post's own link - "Actual radiation dose measurements of Apollo crews measured by onboard dosimetry were, on average, 12 mSv." That's for the entire two way flight, not per hour.
He may have been talking about the calculated dose of 6 Sv in space at Earth's distance from the Sun if a major solar particle event occurred. That's 6 Sv TO THE SKIN PER EVENT, not per hour, or 0.9 Sv to the bone marrow. Or intersecting the path of a coronal mass ejection or solar flare, you could take 10's of Sv if floating naked in space, but fractions of 1 Sv inside a spacecraft. Cosmic ray exposure could be between 0.3 to 1 Sv per YEAR. While all these considerations are very serious, they are far from the cataclysmic levels portrayed by the poster.
I'm sure James Watt's engine was the only design that was built for quite a few years too
Actually, the Watt engine was a third generation engine.
The first commercial steam engines were built by Thomas Savery. The second generation were Newcomen engines. James Watt invented the separate condenser, which allowed a more economic operation than Newcomen engines.
Watt then went on to invent further improvements, in the double action and rotative beam engines. Until them, steam engines were limited to back and forth motion, adequate for pumping water from mines, which was their first application, but in industry one usually needs rotating motions.
Voila, a nuclear rocket with no radioactive exhaust.
False. Quartz is also transparent to neutrons, which will be copiuously produced by the fission reaction going on. I haven't looked at the link, and don't need to. If this thing is fission powered, there are neutrons. If there are neutrons the exhaust is going to be radioactive, unless the gas is pure helium-4, in which case the whole gas vortex UV thing is irrelevant. You can run 4He through a pebble bed reactor and have it come out non-radioactive (more or less.)
Blasphemy is a human right. Blasphemophobia kills.
I thought the big problem with nuke ships was the momentum incurred, and shedding it in time to land without detonating on impact. Slowing down in space is a sonofabitch. On a trip to somewhere like Mars, you have to expend nearly as much energy slowing down as you did speeding up. You can't air brake into mars without one HELL of a big shield/parachute due to the relatively low atmospheric density (about 1% of earth). You basically gotta turn around and thrust directly 180' into your forward path until you're slow enough not to escape the gravitational pull of your destination.
Even chemical fuels have hardly evolved as far as is physically possible. Metastable compounds offer a whole new class of propellants with performance as much as an order of magnitude greater than current propellants. Cryogenic solid and hybrid rockets have hardly even been studied yet (you can even use solid oxidizers). Etc. And then there's the whole other class of improvements: spacecraft mass. Anyone here want to argue that materials have advanced as far as they're ever going to? Anyone?
Then, as you mentioned, nuclear energy is tremendous -- and need not be harnessed directly (you don't have to have a radioactive plume shooting out the back). There's also external energy delivery mechanisms, so your craft need not carry its energy onboard. And there are even some more radical concepts that I know some people who are working on. I can't discuss all of them, as not all of them have been published about yet, but I'll point out one that has: digital quantum batteries. This involves storing energy in arrays of nanocapacitors, whose small size enables quantum effects to require huge voltages for dielectric breakdown. When you take quantum effects into account for energy storage, the theoretical upper bounds on your energy density are similar to that of nuclear reactions (although the specific case I mentioned has tensile strength limits which are much lower -- but this does not apply to all systems).
And finally, the whole premise of the article is totally wrong. The article acts as though energy costs are the primary -- or even a major -- cost of launching rockets. They're not. If you can make a rocket where your propellant cost is a significant fraction of your launch costs, you're doing something *right*. Rocket costs are overwhelmingly parts and labor. Anyone want to make an argument that parts and labor costs on a complex system can never be reduced? Anyone?
Pretty much everything they wrote is wrong. For example, concerning the difficulty of mining water, etc off-world:
*What*? We can't mine ice because it's "low grade"? What on Earth is he talking about? Many bodies in our solar system are covered in, or at least have regions of, nearly pure ice. Mars deposits 100% pure frost on surfaces near its poles. The frost will get contaminated by dust, of course, but it's freaking dust. If you can't filter dust out of water, something is wrong with you. "Other resources"? Like what, iron? Lunar regolith is 1-2% pure iron. Not iron oxide -- *metallic*. As in, "attract it with a magnet and then melt it". Iron miners on Earth would kill to be able to get iron that easily. Low grade resources my arse. The problem with off-planet mining is the cost and difficulty of engineering and transporting light-weight, highly autonomous mining/processing equipment and providing them with their needed consumables and maintenance. It has nothing to do with the quality of the resources.
Who decided to give this person a platform?
..my sister, who got the Donnie Darko numbers tattooed on her arm so she looks like shes making fun of Holocaust victims
If there are neutrons the exhaust is going to be radioactive, unless the gas is pure helium-4, in which case the whole gas vortex UV thing is irrelevant
If the gas is hydrogen it will not become radioactive. When a hydrogen nucleus captures a neutron it becomes non-radioactive deuterium.
Hydrogen has the added benefit that it's the best gas for a propellant, so it would be used anyway.