# Max space velocity?

Ok.. first of all excuse my English (not my native).

I had a conversation with a friend and we were thinking.. We have a spacecraft or something like that. Let's tell that it has a lot of fuel and we are moving with a = x m/s^2, where a is acceleration and x a value (we don't care how big or small). What is the MAX velocity that we will go with? Theoretically v-->c (no abrasion with something wright?), but obviously that's not possible. What is going to make our spacecraft move with a max velocity and what's that value?
Thanks

The max theoretical velocity you can obtain is very close to c, the closer you get to c the larger force you will need to obtain your acceleration. Let's say that you want to maintain constant your acceleration to x m/s^2 then the real problem is that (not taking in account any feasibility of it)
a = F/M where F is the force applied and M is your mass
but the faster you go the larger is your mass that means that the faster you go the larger the force you need to apply to your spacecraft to accelerate.
What will happen, considering that you have engine powerful enough, is that the closer you get to c the smaller your acceleration will be (going to the limit at 0)
Regarding what is going to make your spacecraft moving, that depends on the engine you have.
You can have normal thrust, but probably they will fail to accelerate you beyond a certain point, you can have ion thrusters or any other propulsion system you can imagine. There are many type of hypothetical engine that go from ion thrusters (see on wikipedia how they work) I suggest you to give a look to http://en.wikipedia.org/wiki/Spacecraft_propulsion

Thanks AGADOTTI!! obvious i can tell but i couldn't think that this was the reason!! thanks for the link also