How could a space-craft achieve light speed?

No object with any mass could ever actually reach light speed (but it could get really, really close).  To get close to light speed, any set up where you have constant thrust will eventually get you going very fast - only problem is you run out of fuel.

One proposed system to get around the fuel problem is a hydrogen ramscoop.  Basically you have a very large funnel on the front of your ship, which collects the very disperse interstellar hydrogen present throughout the universe - once you are going fast enough you actually collect a large amount of fuel this way.  Then you run a fusion reaction and use the resulting thrust to keep going faster.

The funnel would probably have to be made out of magnetic fields rather than solid material because of potential impact danger.

by using the light to propel the craft even faster.

Theoretically, no object could ever reach light speed.  According to the theory of relativity, it would take an infinite amount of energy to accelerate an object to the speed of light.

Hi. An engine with infinite thrust.

Dear sir:

I liked your last sentence in the question the best. That was where you said "theoretically of course." There are no present, practical or theoretical means of accelerating man made devices much faster than about 50,000 Miles Per "Hour" in space, that I am aware of. That speed is not anywhere close to 186,000 Miles Per "Second" which is the speed of light. Current space launches stress astronauts very severely (High G's) just getting up to around 15,000 Miles Per Hour from a standing start on the launch pad. I cannot honestly imagine the human body accelerating from zero to some velocity close to the speed of light and remaining intact. Please consider that with all seriousness before moving on with these ideas. The human body can only withstand so much force applied onto it.

I think that part of the difficulty people have in understanding the vast differences in the two velocities has to do with overlooking the terms "per second" and "per hour" which I placed in quotation marks above. To help you see the difference, let me convert 186,000 Miles Per Second into Miles per Hour...

to do that, you must multiply 186,000 times 3,600

That equals

669,600,000 Miles Per Hour

and the closest we have come to that is about

55,000 Miles Per Hour

Regards,
Zah

according to quantom physics, its impossible to travel the speed of light. the craft and the people inside would materialize into little dots and we couldnt get back out of it, you keep traveling that speed...newtons law. and theres nothing on earth than can propel someone to light speed, its too fast.

Not much, except all of the energy (including rest-mass energy) of all the matter in the universe to accelerate it to light speed.  

In other words, it looks impossible (....with our current understanding of the laws of physics).