Should scientists focus on interstellar travel more than interplanetary?(Lightspeed travel)

As you have appropriately said that NASA did not have enough resources, I do believe that if all major space agencies successfully collaborate together they may have ample resources. You also state that it will take massive amounts of fuel to propel a 1 kilogram object to 99% of c, but considering the sudden growth of innovative new technologies more efficient fuels are definitely on the way. If once again NASA put more of its resources into finding new fuels (or any science agency for that matter) I am sure that perhaps with 4-5 decades we may find an efficient enough fuel (and applications) to propel your textbook with say just a kilo of the stuff. I personally am a big fan of sci-fi, and I see interstellar travel as more than a trillion times more profitable than say putting a man on Pluto. As Interstellar travel opens up new habitable planets for us, Humans no longer need to fear of dying with the sun. Whilst certainly in the very short run inter-planetary travel might be helpful in learning more, in the long term mankind has much more profit outside of this solar system. Let us say that the UN formed a science agency comprised of the best men and women from around the world and it had as much funding as the US give the military. If this truly could happen, the interstellar travel may be in the bag by the end of the 21st century. Maybe inter-galactic travel by the end of the millennia. As we know mars is the most Earth-like planet in our solar system, and as it might have had water, intelligent life clearly does not exist and the low gravity of mars proves that oceans may be lost into the solar system or the atmosphere will also escape mars' gravity. This is a theory thought to be a reason to why Martian riverbeds are seen, the water evaporated and escaped mars' weak gravity. This shows that humans have nothing to gain from mars. In Jupiter we cannot send a probe to deep otherwise it will be ripped to shreds so nothing other than observations from the giant. However Titan does seem like a possible habitable planet but its low gravity will not be able to sustain a water body. Also the temperatures do not help. Other than more water for Earth and some minor knowledge we clearly have nothing much to gain from inter-planetary travel. As if we do fervently research on a large topic as such, many new branches of science will open, dedicated to study samples of thousands of new planets. And as you said that propulsion might take a lot of fuel, there are other possible methods. One is Stephen Hawking's Wormhole theory (Whilst the energy expenditure for this is also very high, we can fit in a number of objects through it and in the long term may be much more efficient) and there are some really far out topics like inter-dimensional theories and traveling through black holes, but you must understand that propulsion may soon be an outdated version of space travel. It is inefficient, polluting and most of all wasteful. There already are scientists working on better ways to escape Earth's gravity. So it is safe to assume that propulsion is not the way forward (ironic don't you think?) and that we may need lots of complicated stuff. And for propulsion who said we need nuclear fuel? There are plans for using nuclear bombs as propellers or even a far out theory of using small black holes! Now again these are extremely far out theories but we have split atoms! We have divided the indivisible! We have come up with wonders as a race and can do more. Mankind has thought big but now we need to think bigger! Reach the unreachable! After all Albert Einstein famously said "Imagination is more important than knowledge"