[carlr]

One last question because have gotten way off topic of the thread.One of my complaints about space exploration has been money spent compared to practicality.That is for scientific exploration on its own accord or for the potential of "mining" for resources the time to travel within our solar system makes it unpractical at this time.It does`nt seem much has been done to advance the travel time.Why couldn`t this be used sort of as a corollary?
We put a several stage craft into orbit and than at successive intervals one craft fires another and so on each one adding to the speed of the one that "fired"it.

[PatrickHenry]

One of my complaints about space exploration has been money spent compared to practicality.

Almost everything NASA does is likely related to defense. Propulsion systems, guidance systems, missile controls, miniaturization, communications, spy satellites, etc. They blow some of their budget (more than I'd like) on stuff I see as unproductive, but mostly it's probably okay. I don't mind if, having developed a new system, they send it to Saturn to look around. The stuff has to be tested anyway, and the astronomy payoff is obtained at little additional cost.

[longshadow]

We put a several stage craft into orbit and than at successive intervals one craft fires another and so on each one adding to the speed of the one that "fired"it.

I'm afraid you've lost me..... all I can say is velocities are directly additive as long as the craft's velocity is <<"c" (speed of light), but not as you approach light speed.

An additional consideration is the increase in apparent mass as the velocity approaches "c" -- this requires vastly increasing expenditures of energy (read: fuel) to obtain the same incremental increase in velocity.

IOW, it takes virtually an infinite amount of fuel to accelerate an object having mass to a velocity="c", because the apparent mass ---> infinity as "v" ---> "c."