I would like someone from ISRO ansswer this. Why can't we build a rocket at a space station like ISS?

Well, one way or another - either in pieces, or as a whole, the mass of that ship going to Mars needs to be lofted into orbit.

When Apollo went to the moon, the actual "moon package" was lofted into orbit by the 1st, 2nd, and partial-burn of the third stages, where it parked. Once in orbit, they inspected their ship, making sure it was ready for a trip to the moon. If it was (and, every time it was) - they burned the 3rd stage again, in a "TLI" - Trans Lunar Injection - burn.

What you're describing is pretty similar, only instead of putting the pieces together on Earth, and lofting the whole structure, send the pieces up separately, and assemble them in orbit. And, you're right - they'd only need to add about 40% more velocity to their "stack" - and, the forces they'd feel (and the wear & tear on the ship) would be far less.

Unfortunately, we don't have the shuttle anymore; it would cost more to re-furbish them than to build new ones; Easier still is to go with the Ares-V heavy-lift vehicle on the drawing board (or, maybe use the existing Atlas-V's), and launch the modules that way, unmanned, into orbit for assembly.

It could be because the ISS isn't a mine, doesn't have metal smelters, or the resources to produce fuel or any machined parts to make rocket engines from.

EVERYTHING that is used at the ISS MUST be sent to the ISS from Earth.

Then, there's the issue of the inclination of the ISS' orbit; It's not a useful orbit (being too inclined) for most Earth departure spacecraft.

So, 0-2.

NO,you cannot send a rocket into area with out the authorization of the government above all no longer in the usa.It's illegal to launch a rocket int space.However no executive tec can discover a small rocket but when it's a big one they will probobaly attempt to shoot it down.The rocket might go wherever.It could go to the white condominium or the pentagon and blow up there.

You would expend so much fuel there would be no advantage.Think also about the time line of completing a project like that in a environment that exerts no gravity.Then your idea about a 12 stage vehicle, you would add such complexity to that endeavor especially in that environment.It could take decades to complete the job.

You could, but:

* Building something in space presents difficulties not encountered below.

* You'd still have to lift all the components plus the tools to assemble them

into orbit, so you don't save over a 'staged' earth launch.

Once interplanetary missions become more common assembly of vehicles

in orbit may well become practical.

Maximum weight PSLV biggest of isro caN LIFT IS ONLY 2 TONS TO EARTH ORBIT

http://www.biodiversityinfocus.com/blog/wp-content...