Big theoretical questions about intersteller spacecraft?

Question

What raw materials would I use to build one? Would the engines be in the front or the back? How long would it take to accelerate or decelerate from near lightspeed? Best SERIOUS answer gets the 10 points.

Answer 1

Much depends on the type of drive used. Let's say an ion drive powered by nuclear fusion, producing an acceleration of 1 gravity, would reach a distance of around 10 light years in 5 years, or could reach Proxima (4.3 light years), our nearest neighbouring star, in the triple star system of Alpha Centauri, in little more than 3 years (shiptime, due to the relativistic time dilation effect - much more time would have passed on Earth). With turnover at midpoint, so it could actually stop once it got there, it would take more like a decade, shiptime. The vast bulk of the craft should be forward, to act as radiation shielding, as interstellar hydrogen/helium would produce the effect of cosmic rays, as they collided with the forward section. Lasers could be used to ionise any oncoming matter, and powerful magnetic fields could then deflect the ionised particles, and the efficiency boosted by locating the deflector/ ioniser on a long radio antenna structure, minimising the power drain from the drive. The drive should be located aft, just behind crew quarters, with water, food, immediate supplies, hydroponics, life support, etc. next, followed by fuel and heavy equipment, transport, and long term supplies. Unfortunately, as you accelerate to near lightspeed, your mass increases as well, until you have around twice your resting mass at .8c, or 80% of lightspeed, which, under 1g of acceleration, means double the weight, too. But the human heart and vascular system is not designed to cope with blood or other fluids having a density of 2gms/cc. The heart is a muscular pump, and all muscles operate by breaking Adenosine Tri Phosphate down to Adenosine Di Phosphate, producing a fixed amount of chemical energy, so the blood pressure of the crew would drop, even if the acceleration was reduced to .5g, so they only weighed their normal Earth weight. For this reason, I now consider an upper speed limit of, say, .6c or .7c, will need to be introduced. The crew would also need to constantly adjust to their new circumstances, not being able to accelerate or stop so easily, and accidents may be expected. Artificial hearts could help, for a short time, as would reducing the acceleration. The craft's design and comopsition really depends most on the type and acceleration produced by the drive, or operating principle. Lightweight carbon fibre and plastics, in part, and/or Titanium and/or Magnesium/Aluminium alloys, mostly, with limited steel, due to its heavy weight. An alternative is to send robots (androids, too), with human zygotes in cryogenic suspended animation, placing them in artificial wombs on arrival, and being brought up by androids (robots in semihuman form), with the best parts of our language, culture, science, and traditions. All such interstellar craft are best built, or at least assembled in space, because their large bulk would be impractical to launch from Earth's surface, and a craft built to accelerate gently, as with a lightsail with a centrifuge for "artificial gravity" (as in '2001,A Space Odyssey'), would not need to be anywhere near as heavy.

Answer 2

You'd need materials that can protect whatever is inside from radiation from the Sun and particles whizzing about pretty fast in space, so a heat shield, radiation shield, and just a basic shield.

Engines can go wherever as long as they work. You really can't get near lightspeed though, you'd have to be continuously accelerating for, well, pretty much forever. And you can't bring enough fuel up with you to do that. The space shuttles use up more than half their fuel just getting off the ground, much less getting around space.

Answer 3

I don't know if I believe it's possible to travel at lightspeed, however I know that since there is little/no gravity in empty space an object in motion stays in motion and therefore a powerful engine is not required. Currently spaceships are launched with an initial thrust and then they just keep going as long as there is nothing to stop them. I guess you could "brake" by having some kind of thrusters in the front.
Umm I know this is just from Star Wars, but it makes sense to me when Han explains that a lot of calculations are needed before you jump into hyper space. It would be very easy to hit something.
If you were traveling at or above the speed of light, then there would be know way to see anything! If lightspeed travel were possible then we would have to create space highways or something so that you knew where you could fly with out hitting things, since you have no way to see for yourself. Imagine the traffic accidents if people miscalculated or flew someplace that was unexplored.

Answer 4

I would use materials that would both withstand the stress of space flight, absolute zero temperatures, and the heat of re-entry.

Fiber composites and other additives. The materials used for the space shuttle these days are bulky, outdated, and hellishly expensive to maintain.

Technology is making it much easier to achieve human spaceflight without the need to resort to obsolete composites.

The engines would be in the back--of course. Frontal engines would be an impossibility; as you would be going *forwards* and not back.

Given the severe engine limitations of our current spaceflight technology--we can't even reach lightspeed; let alone break out of orbit.

Answer 5

An interstellar spacecraft would not have conventional engines, it would more likely have an umbrella shaped sail and use solar wind for propulsion ... yes, the first interstellar space ship will be a sail boat.

Acceleration, deceleration and course changes will likely be planned years or even decades in advance and involve using gravitational forces of stellar objects.

The biggest problems are going to be:
1. energy, food and water self sufficiency
2. shielding against cosmic radiation
3 at speeds required for interstellar travel even a small object has a lot of kinetic energy. Some type of electromagnetic shield will be necessary against everything, even a speck of dust.
.

Answer 6

You could use any material, that isn't really a problem. Aluminum, steel, plastic, whatever.

The engines would probably be in back. At least all our current space craft have the engines in back, pushing the space craft, not in front pulling it.

At 1G, it would take about a year to get up to a good fraction of the speed of light. The problem would be to carry a year's worth of fuel. Not just fuel, but propellant. A rocket depends not only on the energy gotten from the fuel, but the impulse gotten from throwing the reaction products out the nozzle. Rockets are very inefficient that way. Most run out in a few minutes, even if 90% of all the weight in the rocket is fuel to start.

Answer 7

I have seen plans for a interstellar ship that will go 65% speed of light. Theoretically it will work. It looks like a funnel and works on a ram jet type principal. It would travel with the funnel side toward the front to scoop free hydrogen out of space and funnel it into a hydrogen reactor. Scale-wise, if the ship itself were as big as the space shuttle, the 'hydrogen scoop', or funnel, would be thousands of miles across. But it was made of a mylar type substance. The nearest star is 6 light years away, and at 65% light speed, it would take around 10 years to get there.

Answer 8

You can't see me, so you can't tell how serious I am, but take my word for it: I'm SERIOUS.

Interstellar travel is not practical, and will never be achieved; therefore there are no materials from which an interstellar craft could be constructed. It does not matter where the engines are mounted, as no such thing exists. It would take an infinite time and an infinite amount of energy to accellerate to near light speed.

Believe me, listening to your girlfriend's stomach gurgling is much more fun, and is a much more worthwhile and practical way to spend your time.

Answer 9

The best postulate calls for the Ram Jet Hydrogen engine, which can be positioned almost anywhere.

Conventional chemical propulsion gets you to speed and then fusion of hydrogen in the Ram Jet generates a plasma stream that moves you faster and faster with unlimited fuel.