What sort of propulsion technology would allow spaceships to lift off the surface of the Earth and ascend into space like we see in sci-fi movies? In many sci-fi films, spacecraft are easily capable of lifting off the surface of a planet like a Harrier and ascending into space. It's clear that the propulsion system/jet engines aren't your average chemical rockets, as the ships are usually very sleek and lack a huge reservoir of propellant. Ion propulsion also seems to be out of the question due to limited thrust density.
I'd love to know if any aerospace engineers or physicists out there can chime in to discuss the plausibility of these types of ships. It would be amazing to see them in my lifetime, and it'd be a huge disappointment if they're not really in the realm of possibility at this time. That being said, I've always wanted to get to the bottom of this and figure out what sort of technology would be necessary.
 A: The answer based on accepted physics is trivial: none. That's why they call it science FICTION. One can theoretically reduce the amount of propellant, but then the required power these ships would have to develop would go trough the roof. Keep in mind that a medium sized rocket develops on the order of 10GW of power for a few minutes during first stage burn and then something like 1GW for six, seven minutes during second stage burn to get to LEO. Reduce the amount of propellant by a factor of 10 to make a "sleek" ship, now you would need 100GW during the first stage burn. In effect that would be a giant waste of energy for no good reason.
There is nothing really wrong with rockets except for the one thing that SpaceX is trying to fix, right now: we are basically throwing a machine of the size, cost and complexity of an airliner away after the first use. Once we stop doing that space access will become cheaper by quite a bit. It won't become really cheap (as in \$49 to the Moon and back), but it will, for all practical purposes, become cheap enough, given the difficulties and cost to survive in space once we get there (the launch technology can't get rid of those). A cost reduction far below the order of \$100k per person for manned flights will therefor have next to no economic impact on any scientifically imaginable form of space economy. 
The more interesting questions, physically and technologically, are related to space elevators and electromagnetic mass drivers and such... but those are not "ships" in the sense that you are looking for, right? 
A: It sounds like what you're looking for in general is an SSTO (Single Stage To Orbit -- http://en.wikipedia.org/wiki/Single-stage-to-orbit -- meaning it doesn't drop off boosters on the way up) rocket with a high payload fraction ( http://en.wikipedia.org/wiki/Payload_fraction -- meaning most of the spacecraft isn't fuel and fuel tank).
Unfortunately, current SSTO designs have very low payload fraction.  They would be a lot of fuel tank and a little useful payload, so much so that those designs just aren't used.
The bottom line is, to do what you want we'd need an engineering breakthrough.  Not a physics breakthrough -- a spacecraft propulsion system like the one you're talking about wouldn't violate physical laws as we know them.  But we've got no idea how to build a highly efficient rocket (high ISP -- http://en.wikipedia.org/wiki/Specific_impulse -- how much thrust you can get out of a bit of fuel ) that is also a high-thrust rocket.  We have designs for rockets with far higher ISP than the shuttle's main engines, but the the rocket would be too heavy to lift itself off the ground.  It would just sit on the ground, firing away, wasting fuel.  Although it'd be wasting fuel very efficiently.
If someone ever develops a thermonuclear reactor that you can fit in a soda can and fuse a kilogram of deuterium every second, you'd see rockets that'd go straight up, laughing at the Earth's gravity all the way, but we don't even know the design principles for such a beast.
A: If you're thinking of the type of spacecraft we see in Star Wars|Trek and similar, it is clear these cannot be reaction-based rockets.
Look at the power that has to be unleashed to get a Space Shuttle into orbit and compare it to what happens in the movies; The Millenium Falcon, for instance, is a few times larger than a Space Shuttle yet it scoots into space with barely a condensation trail. Note that changing the efficiency of the fuel source just changes the amount of fuel you need - it doesn't alter the amount of energy required to get into space.
We have to conclude, therefore, that these craft are using a novel technology to fly. Anti-gravity repulsion perhaps? Or some space propeller that pushes against the fabric of space-time?
In any case, the technology is well beyond anything that currently exists. You might live to see it - if you are very young and live a healthy life :-)
