The novel was written in 1974. The first chapter takes place in 1997. In that slim, 23-year stretch, humans have developed spacecraft that can accelerate to 99.9% of light speed and now routinely make journeys to collapsars a light-year or more away from Earth, to the point where they've encountered an alien species and have gone to war with it. In Real Life, we don't even have feasible designs on the drawing board today for spaceships that can go more than a few percent of the speed of light before running out of fuel, and no spacecraft that's actually been built has a delta-v budget anywhere near that high. Surely, Haldeman should have been able to tell that his timetable was a bit ... overly optimistic?
Haldeman admitted that it was unrealistic, and that he mainly set the timeframe so that he could have Vietnam vets as the commanding officers (Haldeman himself is a Vietnam vet, and writing the novel was basically his way of coming to terms with his experiences).
The Tachyon Drive allows a starship to accelerate continuously, at several g, without ever running out of fuel. Since acceleration implies kinetic energy, and lots of it, this further implies access to an almost unlimited source of energy. Such an energy source should easily be able to power human civilization many times over, resulting in an unprecedented age of prosperity. Yet by 2007 Earth has become a Crapsack World where nearly everyone is a hair's breadth away from abject poverty. Even with the best and brightest turned into cannon fodder by the Elite Conscription Act, shouldn't the existence of unlimited energy more than make up for it?
Yeah, but its being dumped entirely into the war effort.
Perhaps the powersource used by the ships doesn't scale up enough to use on Earth, or perhaps there are other problems with using it to do anything except power spaceships.
What was the point of having psionics in the fisrt part? Unless I missed soemething, it was never addressed or brought up again, neither directly nor indirectly...
It seems to have been to emphasize that Mandella and his buddies don't understand what they're fighting and are in way over their heads.
It's possible that psionic abilities were phased out when when humanity went for eugenics programs. They didn't seem to confer any significant advantages in the chapter they appeared in anyway.
Potter's father comments that the war is the reason why everything is so bad when they return after their first tour; "the very best fell to the Elite Conscription Act and wound up being cannon fodder." Yet the small size of the forces doing the actual fighting appears to contradict this. OK, so they need a large military industrial support network to fight a war in space. But surely a lot of that would still be based on Earth, unaffected by relativity and therefore still able to contribute to Earth's economy?