Nibb31

Once we have made the Earth uninhabitable, we could always dig ourselves underground, live on hydroponic lettuce, recycled urine, and don't forget to wear an EVA suit when you go outside. No need to go to Mars.

No it didn't. Having it as a separate part is good, but it really shouldn't be a decoupler.

I think it's pretty accurate really. What else would you expect with a question like that?

Already discussed many times. It falls into the fantasy megastructure category, with the giant railgun, the rotovator, the launch loop. It has all sorts of problems, like developing 36000km long carbon nanotubes instead of the 10 millimeter ones that we currently have, and building self propelled elevator cabins that go fast enough to make the thing worthwhile. And of course, it assumes that someone is ready to spend billions of dollars to build the thing and that people are willing to massively buy tickets to go to GEO. For what? It takes a 7 days to reach the GEO station of a space elevator at 200km/h. 2 weeks for a round trip. To make it worthwhile, you need a decent payload, something like 10 or 20 tons. For people, you need food and supplies and decent comfort for those 2 weeks. Imagine a high-speed train, with enough grip on the cable to carry its own weight including its own power source and heat dissipation equipment, plus the payload, and without damaging or eroding the cable. Major engineering challenge here and not realistic with current technology.

prograde, retrograde, normal, antinormal, radial, antiradial? The ISS uses forward, aft, port, starboard, zenith and nadir. It isn't always in the forward-prograde orientation. The ISS sometimes rotates on another axis to facilitate docking of supply ships.

1- Because there is no time to develop, launch and use a centrifuge module before the ISS is decommissioned. 2- Because microgravity scientists don't want their own experiments messed up by the vibrations of a centrifuge.

I've seen that before...

There is a huge difference between theoretical design and operational hardware. It involves this pesky thing called "engineering". Things that may seem trivial take years or decades to actually implement. Each latch, hinge, hose, interface, takes years to design in the real world. Components have to be sourced, materials have to be tested, suppliers have to be selected, fabrication procedures have to be written, personnel has to be trained... There is this measure that NASA uses that is called Technology Readiness Levels. Many of the technologies that are needed for a manned Mars expedition (let's not even talk about colonies or bases) are around TRL 3 or 4. You need to reach TRL 8 or 9 to start building vital mission hardware out of it, and it takes years, and sometimes decades, to move from one level to the next. Things like closed-loop life support (or even a reliable 3-year ECLSS), ISRU, shielding, simply do not exist... The infrastructure for launching and constructing a Mars vehicle simply do not exist and there is no budget to develop them.

The centrifuge won't happen on the ISS. There is not enough time before the end-of-life of the ISS to develop, launch, and use it. Also, it induces vibrations that might interfere with the microgravity research that's being done in other labs. For use on a spacecraft, it makes more sense to spin the entire vehicle instead of relying on a vital rotating joint. You want to minimize moving parts as much as possible. The thing is, we simply don't know anything about centrifugal artificial gravity. It might be beneficial or its side-effects might be detrimental. The induced Coriolis effect might cause nausea, dizziness, blood-circulation problems or internal-ear issues. We don't know how much is necessary or viable and we don't know if it's any better or worse than using medication and exercice like we do now. In the current state of knowledge, it doesn't make sense to design a hypothetical medium-term interplanetary mission around it. There is no reason to claim that artificial gravity is absolutely necessary, but it does make the vehicle design much more complex and expensive.

You do it progressively over a long period of time. It's not a problem that will be solved with some sudden breakthrough. The problem is that there is no "killer app" for space. The lack of demand is partly due to the cost, but mostly due to the lack of any worthwhile return on investment. Simply put, nobody really needs to go to space. The only profitable business up there is com sats and government contracts. Space fanboys talk about tourism, mining, and microgravity manufacturing, but those activities all lack a viable business model, regardless of cost. Even if you cut prices by 50%, they still won't be queueing up for tickets.

We are only lacking one thing: will and money! Er... We are only lacking two things: will and money... and technology! ...and ruthless efficiency... Um... Among the things we are lacking are will, money, technology, ruthless efficiency, and a near fanatical devotion to the Pope! Alright, I'll come in again... NOBODY EXPECTS THE SPANISH INQUISITION!

The CM weighed 5.8 tons. The fully fueled LM was 14 tons. The LES weighed 4 tons. A LES capable of carrying the CM+LM+its own weight would need need to be considerably heavier.

Just get a free AVG. An antivirus isn't really necessary since Windows 8 anyway.

In the early stages of the Apollo program, there were two mission architectures. - Earth Orbit Rendezvous (EOR), which involved two medium-sized rockets, and assembly of the spacecraft in orbit. - Direct Ascent (DA), which involved one big rocket (the Nova, which was bigger than the Saturn V). Two launches doubles the risk of failure. LOX and LH2 have a limited shelf life once on orbit. The propellant boils off if you leave it to loiter for too long. If one of the launches was scrubbed, you would lose the mission. With a single launch, you simply postpone until the next launch window. It also involved rendezvous and docking, which were technical problems that hadn't been solved yet. Some people even thought that they were unsolvable. On the other hand, everyone knew that the Nova rocket would be a huge challenge. Saturn V was already stretching the limits of logistics and infrastructure. Nova was probably beyond those limits. Both the EOR and DA Apollo plans had the entire CSM land on the Moon. The SPS would have served as an ascent engine (which is why it was over-engineered), but the CSM weighed 30 tons, so a descent stage would have much heavier than a separate LM that weighed only 15 tons. There were also other problems, such as viewing the ground for the landing or getting the astronauts in clumsy EVA suits from the CM down to the surface 12 meters below (a 4-storey building) without breaking their neck. All sorts of contraptions were devised, like winches, rope ladders, and inflatable airlocks, but the whole idea was really impractical. There were some big fights at NASA about which approach to use. Then, someone came up with the Lunar Orbit Rendezvous (LOR) architecture that we all know and all those problems were solved.

The CM needed to be on top for the Launch Escape System to work properly. If the LM had been above the the CM, then the LES would have had to carry away the weight of the CM and the LM, which would mean that it would have to be more powerful and much heavier. The CM also needed to be in the upright position with the astronauts facing upwards. If the CM was facing downward, already attached to the LM, the astronauts would have taken the Gs in an "eyeballs out" position, which is most uncomfortable and unsurvivable in case of an abort. In this case, the LES would have to carry away the entire CSM, which was even heavier than the CM+LM. It was envisioned quite early that Apollo would require rendez-vous and docking, which is why the Gemini program was devised after Apollo started.

You are assuming that the major cost factor in the space industry is the hardware. It isn't. It's the people. Reusable launchers don't necessarily require less people to operate. On the contrary, because you are reusing your rockets, you need to build less of them, which makes each unit more expensive. You might need less people at the factory, but you need more people to handle and refurbish the reused rockets. So any actual cost reduction is marginal. Reusable only makes sense when launches are frequent enough to justify reusing the hardware. This means that there must be market demand for frequent launches, which there isn't. Even if you manage to slash launch prices by 50%, you might increase demand somewhat, but you won't double the number of customers.

One could argue that there is very little difference between a one-party system and a two-party system. Most democratic systems offer a much greater choice... but we are digressing. And the United States gave it up as soon as they realized that it makes no sense from a strategic or tactical perspective. The Moon is useless as a military asset.

You need to read up on the definition of communism. There really isn't much left of communism in China today other than the name of the party.

I guess so.

Yes, but the barycenter of the Earth-Moon system is inside the Earth, so it won't move much.

First: There are no communist countries with any space capability (Hint: Russia is no longer communist and Chine is just about as capitalistic as it gets). Additionally, "High ground" is a military tactical concept that is meaningless when considering the Moon. Second: Land will only be claimed if a- It has any value. b- The claim can be defended. c- The cost of defending the claim is lower than the value of the land. There is no profit to be made on the Moon, Mars, or on Asteroids and there won't be for a very long time. There is no point in amending the Outer Space Treaty until we start seeing routine flights to those places. Who says that humanity is to ever become a spacefaring race? You do, obviously, but can you generalize that to the entire human race? Other countries, other cultures, other demographic groups, might have other ultimate goals in life. We have a lot of work to do here before we can even be considered a united race, let alone spacefaring... Again, you are generalizing western cultural traits as if they were inherent to our species. Competition isn't more or less part of human nature as cooperation. It all depends on the context and what there is to gain. To do big things, humans are only motivated by 3 things: safety, comfort, and wealth. Space projects don't tend to increase any of those things.

It falls towards the parent body and crashes into it unless you do something to slow it down. That's how spacecraft come back from orbit.

That still fits in the "seeking wealth, comfort, and a better future for their children" category. To relieve any sort of demographic pressure, you would need to ship people by hundreds of billions, which falls into the science-fiction category. And there is no lack of space on Earth. If you are going to live on closed-loop life support and hydroponics inside a hab module, then you might as well do it in the antarctic or the sahara desert in an environment that isn't instantly lethal and where it doesn't cost so much to get there. At any rate, if we can master closed-loop life support for millions of people, then there will be no more demographic pressure.

Sure. Now look at what it takes to put those 6 tons into orbit: a two-stage Falcon 9 that weighs 500 tons. To make the Falcon 9 an SSTO design, you would have to remove the upper-stage, which means that the first stage has to burn longer, which means more propellant, more thrust, therefore more engines and more weight... In the end, your SSTO rocket would have to be significantly bigger than a Falcon 9, which is why SpaceX (and most other rocket companies) went for a two-stage design. It also has to re-enter from orbit, and designing a heatshield for an entire rocket is a major challenge. You are going to bring that heatshield and some sort of landing capability, whether wings or propulsive landing, all the way to orbit. All that stuff is going to weigh much more than your 6 ton payload, which means that the rocket needs to be even bigger.

Yes, but we don't have the technology to assure that we can keep a colony alive. Also folks, what is the point of a colony? In the past, colonies were created where there were resources (gold, spice, slaves, exotic produce, etc...) that would increase the wealth of the colonizing nation. Another reason was to grab land before other countries would get their hands on them. The colonial effort was usually initiated by governments or government-controlled companies for two main reasons: greed and power. And the whole thing fired back when those colonies went independant. The big difference is that in those days, you could sail for a few weeks and live off the land when you arrived there. You had air, water, construction material, and a temperate climate. You could grow food locally, build a farm, and rely on trade routes. You didn't have to rely on supplies or technology for long-term survival. And even then, it was tough. If Mars One wasn't a scam, with today's life-support technology and no assured supply lines, it would be more likely to end like the Roanoke Island colony in 1587. Any space colony would have to be massive in order to be self-sufficient. It would need farmers, miners, doctors, children, cooks, teachers, janitors, engineers. It would require hundreds of inhabitants just to have the minimum skillset for survival of the group. This means that it would need hundreds of interplanetary launches to bring the equipment, supplies and people. It is simply beyond any short or medium term capabilities. Now, why would a government or a corporation invest hundreds of billions to build a colony on Mars or the Moon when: a - There are no useful resources that would increase anyone's wealth back home. b - There is no possibility of a land grab, firstly because of a and secondly because of the Outer Space Treaty. c - Any self-sufficient colony would be hard to control, which increases the risk of losing it to independance. As for the colonists, just like all migrants since the dawn of humanity, they moved there to seek wealth, comfort, and a better future for their children. Mars on the other hand is a sterile wasteland, bombarded with cosmic radiation, where you can only go outside with a 50kg EVA suit. You would spend the rest of your life living inside a prefabricated hab module, breathing canned air, drinking recycled urine, and eating hydroponic tomatoes. You will never feel a drop of rain on your face or feel the wind in your hair. It is not a great place to seek "wealth, confort, and a better future for your children", even if you could have any.