There are lots of things about Han's ship, and other ships that you see in Star Wars, that are extremely appealing. For example, Luke's X-Wing fighter is small enough that you could imagine it fitting in a garage, but it apparently has enough fuel and supplies (like oxygen) on board to travel distances of many light years. All of the ships seem to have:
No one has the slightest clue of how to accomplish items 2 through 4 in this list today, so let's ignore them and focus just on the engines. Will you ever have a car-sized vehicle that can fly to the moon?
- Incredibly powerful and efficient engines that use very small quantities of fuel
- Extremely effective artificial gravity systems
- Equally effective inertial damping systems, allowing the ship to go from zero to million of miles per hour in just a few seconds without crushing the ship into a pancake
- The ability to travel faster than the speed of light.
The Saturn V rockets that sent U.S. astronauts to the moon show you the state of technology today. The Saturn V is a chemical rocket. It was 363 feet (110 meters) tall and weighed 3,000 tons (2,727,000 kg). This is hardly something that would fit in your garage! Plus it would be hard for the average person to afford it. Or to fill it up -- It carried over 5 million pounds (2,272,000 kg) of fuel!
To be able to blast off to the moon from your garage, one thing you need is fuel with a much higher energy density. For example, the article entitled How Nuclear Radiation Works discusses the fact that a pound of highly enriched uranium has enough energy in it to equal approximately 1,000,000 gallons (4M liters or so) of gasoline. In other words, approximately all of the energy stored in a Saturn V rocket could fit into a pound or two (a kilogram) of enriched Uranium (assuming that you had an efficient way to extract the energy in a controlled way). Other ways to create energy efficiently include nuclear fusion and matter-antimatter annihilation.
The problem with rocket engines today, however, is that they are by necessity reaction engines. The only way we currently know of to propel a spacecraft through space is to throw something out the back of the spacecraft and take advantage of the equal and opposite reaction. The article entitled How Rocket Engines Work goes into this in a lot of detail. A chemical rocket burns the fuel to accelerate it, and then throws the weight of the fuel out the back of the rocket at a speed of perhaps 6,000 MPH (10,000 KPH). The spacecraft then benefits from the equal and opposite reaction and moves forward.
Because of this dependence on reaction engines, you have to carry more than just "energy" in your spaceship. You also have to carry something to throw out of your spaceship in order to move forward. This mass could be in the form of a solid, liquid or gas. Ion engines, for example, ionize something like Xenon and accelerate the ionized atoms in an electric field. The atoms are moving a whole lot faster when they come out the back of an ion engine, so you get more forward motion per atom thrown. But you still have to throw lots of atoms to go anywhere. By throwing the atoms at speeds approaching a reasonable fraction of the speed of light, you get maximum movement per atom. However, you still have to carry enough mass to get the ship up to speed and then stop again once you get to the moon. Using today's technology, that's a lot of mass.
From this discussion you can see that your personal spaceship needs a very exotic energy-production system (using nuclear fission, nuclear fusion or antimatter), and you have to carry the mass that will be thrown out of the ship to create motion. That mass will be significant using current technologies. One last problem involves heat production. Nuclear fission and fusion generate lots of heat, which you will need to dump somewhere. Dumping heat into space is hard because the vacuum of space makes it the world's biggest thermos. The size of the thermal radiators will prevent your personal spaceship from fitting in the garage.
So it doesn't look good right now. Unless someone invents something like a cheap anti-gravity machine or a way to warp space-time, we will not be flying to the moon in our cars any time in the near future...
Here are several interesting links: