One of the big problems with long distance space travel is the amount of radiation coming from the sun. ATM, the only way to stop it is lead shielding, which isn't practical for spacecraft. I expect they will ship up smallish amounts of lead and other materials, and build a ship up there. This also means that the ship design wouldn't have to have any of the design problems of ships that have to get through the earth's atmosphere.
IIRC, the lack of practical radiation shielding is the big reason we haven't gone to Mars.

Water is actually one of the best radiation shields. Have a layer of water between you can the ship's hull. Your drinking water is clean and you don't get fried by radiation.

Centreri. Heat resistant plates are 9000 kg+. Metal plating weighs more. Weighing more means it gets harder to brake from re-entry, and touchdown. There are no other workarounds.
It is Metal armour + Slow re-entry, or Heat-resistant + atmospheric braking. And the previous is obviously better.

Even with fusion reactors, we're stuck in our solar system unless we have a viable FTL technique. You cannot travel faster than the speed of light in normal flat space- and the closest nearby system would take an extremely long time to reach even with light speed. The only seriously considered is the Alcubierre Drive (http://en.wikipedia.org/wiki/Alcubierre_drive). Theres 3 problems with the drive though. 1. How do you make space stretch in a wave?
2. How do you make a flat space bubble inside that wave? 3. Can you even imagine how much energy it would take to create such a thing?

Well if this becomes possible, you won't have to worry about decelerating your spacecraft from c.

/Facepalm

Water, or rather the hydrogen in water,(which is also in concrete) stops neutrons penetrating. However, it doesn't stop gamma particles. For that, you need lead or another heavy metal, such as tungsten.

If your Alcubierre Drive is available and energy required doesn't increased based on mass, there's no necessary reason to choose between those two. Metal Armor + Heat-Resistant + Atmospheric breaking is an option, and we've put ships to space that had metal armor before.

We're not physicists, lets not ask questions that someone probably knows the answer to as if no one does. However, that's a very shiny nonexistent technology.

It's cool how you just kind of ignored my argument Centreri.

Why bother thinking up what you'd make this space ship out of when the topic isn't even about the spaceship? Also, why bother when there are hardly enough of those heavy metals to make the massive starships that you'd need? Furthermore, how do you power gargantuan ships made out of something like Tungsten(That was just the one guy that mentioned that, can't remember his name.)?

Your argument was that it's hard to communicate. It's a pointless argument referencing an obvious problem that we don't have a solution to yet. Also, since when are there not enough metals?

And I believe I answered the energy problem, at least in part - fusion energy.

No the alcubierre drive theoratically does not depend on 'mass'. It mostlikely will decide energy consumption on the basis of how large you're making your bubble, and the amount of space contraction you will have. But while you have stated a point like that, you've forgot an axiom of Spacecraft. The amount of force required to change the kinetic state of the craft increases based on mass. Plus if you have a viable slow reentry method, that way is 'cheaper'.
But our electricity bills will never go down.

It's not a pointless argument, it's an argument that answers the question, saying that, no, it isn't viable. Why think of solutions to what sort of spaceship you'd build when such a necessity as communication doesn't work?

And it's not really metals in general, it's Tungsten. I don't know where you'd get enough to make the enormous amount of enormous ships that you'd need to do all the things you people are suggesting we do (Mainly sending goods back and forth). Of course, that wasn't your argument, atleast I don't think it was, so you shouldn't have really been the one to retort against what I said regarding metals.

Also, regarding fussion energy, how are you going to use that to propell the ship? Just blow it forward with nuclear blasts (Okay, this question is rather stupid)?

The thing is, it's the cost of getting lots of metal to space fast versus the cost of getting less metal to earth over more time. Both viable, and we really don't know which is more expensive. As for the axiom - doesn't it contradict what you just said, that the alcubierre drive doesn't depend on mass? Isn't an axiom itself just an observation that's been true so far, but can easily be incorrect?

Mebbe they will.
Rapid communication between trade ships isn't a necessity. All that needs to happen is them getting to a location with something we want, grabbing it, and hauling it back. Communication allows you to speed up the process, but it's not a requirement. Additionally, if the alcubierre drive isn't science fiction, it might be possible to send signals along it (hell, I don't know), or just message-ships.
... the same way we currently get space shuttles or rockets to move in space. Energy is energy.

Ugh, please go read the article of Alcubierre drive to understand. You aren't accelerating. You will be riding in a wave of contracting and expanding space. So no, it is not contradictory. You aren't even moving at all when you warp yourself lightyears away.
Also, alcubierre drive is only a theoratical drive- but it beats other wacky scifi FTL models.

Energy is not energy. You need to convert fusion electrical energy into kinetic energy, which would take some form of propellent or other propulsions.

I assumed that you were pointing out with ' The amount of force required to change the kinetic state of the craft increases based on mass.' that it's a problem. If it's not a problem, then why bother saying something obvious and irrelevant?

... no, der. we've been transforming steam into motion for more than a century. We've transformed fuel to enough energy to arrive at the moon. I think we can turn electrical energy into propulsion.

Turning electrical energy into kinetic energy can be harder than you might think. Modern rockets (even the space shuttle) use conservation of momentum to launch into space, and for conservation of momentum to push you up, something else needs to push down, in this case, it is the rocket fuel flying at high speeds downward that pushes the rocket upwards. Electrical energy has no mass with which to propel the ship forward.

On the other hand, electrical energy could certainly be used to power something to propel the ship.

And you can't just say "fusion electrical energy"(whoever it was that Centreri quoted), the energy produced by fusion is heat, heat makes steam, steam turns a turbine, turbine turns a magnet which induces a current, which is where the "electrical energy" comes from.

I say we use a propeller thats connected to the turbine.

Now before this convorsation gets any more outta the playing field, whats the point of making a spaceship that can do all these things, if we dont know, WHERE to build a colony, if its a good idea to build one, if its financially a good idea, or if we even CAN. The spaceship is obsolete if you cant use it for the purpose it was intended.

In other words, one thing is useless if you cant have both.

Its not irrelevent. Because warpiong space will inevitably be inaccurate- more so easier covering large distances between a vector. And when you get close, you will be using conventional method of propulsion (all spacecrafts use this propulsion at any given time- making it relevent), which requires you to accelerate- at a given speed that won't take a life time. And to do that, you require force- and the force required to accelerate to a certain point increases based on mass- and same to decelerate.

We can. There are several methods including propelling ionized gas. But it is so slow that it will take 7 years just to get a probe to jupiter. Imagine, a huge honkin ship with that kind of small force- it would take a lifetime.

Someone mentioned earlier (as a joke) that in order to use nuclear power for spaceship propulsion we'd have to detonate nuclear blasts behind the ship.

Well, I was doing some research and strangely enough, that idea was proposed in the 1940s/50s and still has a lot of potential today. However, due to the nuclear treaty of 1963 the idea was abandoned.

I give you Project Orion.

The theory is that given the right materials and structural design, it is possible to build something which will withstand a nuclear blast at close range. An Orion-powered ship would drop small shaped-charge bombs (fission or thermo) containing some working mass (to 'push' against) behind it with a time delay, designed to detonate 60m from the rear of the vehicle. The blast hits a plate, connected to a robust shock-absorption system to reduce the acceleration down to a level which won't kill the occupants of the ship (2-4g as opposed to 100g+). Using this method of propulsion, thrust in the region of meganewtons would be achieved at a very high specific impulse (given the efficiency of a fission/fusion reaction) and a thermonuclear Orion could reach about 10% of light speed. According to the article, a ship powered in this way could, potentially, make a round trip to Pluto in one year.

Now, there's always a drawback with spaceship designs and with this one there are two I can think of. The first is that it would be stupid to use nuclear blasts to propel the ship into orbit. Nobody wants a load of nukes detonating in Earth's atmosphere (or too close to it due to the massive EMP that would result), so it would be necessary to build a large Orion design in orbit, then move it to a safe distance using more conventional propulsion methods before switching to nuclear pulses.

The other major drawback is the size and mass required of an Orion ship. General Atomics proposed three designs: a satellite class Orion of 300t, a mid-range one of 2000t and a 'Super-Orion' of 8,000,000t! The head of the Orion programme believed that a 4000t design would be sufficient for Moon landings and visits to Mars. 4000t is a little more than the Saturn V rockets which took men to the Moon, so that's not too bad in terms of mass. However, I want to look a bit more closely at this Super-Orion design.

An 8 million ton design would be an 'Interstellar Ark' type ship, capable of holding many thousands of people. Scaled down versions of this design could be used to transport all the materials and personnel needed for a permanent Moon or Mars base, for example. Basically it could be a kind of mothership or colony ship. Some designs had the plate at the back of the ship being made mainly of uranium, so it could be used as fuel at the end of the mission.

What do you think of an 'Interstellar Ark' idea? There are big social/cultural problems associated with such a concept if an Ark was used to explore Proxima Centauri, for example (would take 44 years for an Orion powered Ark).

The Ark would essentially be a generation ship. Where people would live several generations before reaching another solar system. A round trip would be atleast 1 or 2 generations from here to Proxima Centauri.
Although, I would hope that when we get to build an 8 million ton 'Ark' ship, we'd have a viable FTL drive with a better conventional propulsion system.
This thing will never be able to land on a planet though, it would have to land via small ships. If this kind of ships were used as colony ships, it would expect it to 'act' like a cargo ship, making round trips between colonies to colonize more, leaving some modules behind to accelerate the colonization process.