Stages of Energy and Payload for Space Travel
Looking far into the future as science future, not science fiction, we categorize the stages of propulsion to explore the universe. The key point is ratio of energy in fuel to the mass of the propellant and energy source. The other point is the mass of the payload for exploration. While these concerns are maybe centuries into our future, they relate to the question of whether advanced civilizations could have visited our planet or will shortly, now that we are evidencing our own advancing and struggling technical civilization.
There is also the question of whether there can be intelligent civilizations of much smaller and lighter, but better organized, life forms, which would find space travel much easier. We have to remember that we started our own space travel with small monkeys and dogs. I’m really thinking about smart or trained ants and mice. Plus, super smart mini or micro robots, or nano bots. Flying saucers that are really the size of saucers. I was told about tardigrades that were flown outside a rocket and survived the temperature extremes of space, lack of oxygen, and radiation. Their size goes up to 1.2 mm, but can also be 0.3 to 0.5 mm. They are also water dwelling and called “water bears”. They have been around for 500 million years. They dedicate themselves and hibernate. They are also inhabit many extreme earth environments. I am of course not saying that these life forms developed space travel, but they could be evolved, trained, or genetically engineered to be the work horses of guided exploration. Ants work to build their own homes, explore their environment and secure nourishment, and propagate further colonies. Missions with smaller explorers will allow us or other civilizations to send out probes at much higher speeds. We or they can also send out many missions for the same price as a single human mission.
As far as we are concerned, a large part of our bodies are used to move us around on a planet with strong gravity. There is no gravity in outer space. Our bodies are equipped to do a lot of tasks, other than just running a space shuttle. Species that spend their times space traveling, would evolve into cerebral blobs using voice responsive machinery. Since we now have Artificial Intelligence (AI) driving cars and flying airplanes, AI would also take over the long term flights and space exploration. Really, if we land on another planet, it may not be in a habitable zone for humans. AI and robotics could do the necessary exploring, and only needs an energy source, not the enormous payload of life support for humans. Burning local fuels would generate energy and heat, even if not compatible for food for our life forms. Of course, our probes would also have the rocket energy source, and stellar radiation available.
Now that we can efficiently send and receive radio waves to receive knowledge from and inform other civilizations, the usefulness of space travel is moot. Does anybody actually fly to New York to pick up their NY Times for the day?
We are of course assuming that there is no travel faster than light, no warp speed, and no available multiply connected wormholes that we can use to tunnel around the universe. For perspective though, we can consider how our development of transport and communication brought new surprises. Columbus took 10 weeks to reach the Americas. Now, Madrid to Miami is less than 10 hours by flight, which was not perceived of then. The pony express took 10 days to go from St. Joseph, Missouri to Sacramento, California, to deliver a letter. Now, email between the two has to be on the order of a second.
Then again, what if the advanced civilizations have explored all of the planets already, but have just left us alone, until they will have to come to our rescue, which means, soon.
So, back to the stages of power generation and rocket thrust. We currently power rockets and most of our planet with chemical fuels, with yields of an electron volt per nucleon mass of about a GeV or billion electron volts, or a ratio of 10^(-9). Our cleanest power in large amounts comes from nuclear power, with yields of 200 MeV or million electron volts from U235 with mass of about 200 GeV. The energy to mass ratio is 10^(-3). Our present devices of attempting fusion are growing more and more massive, but the ratio of the energy output of 20 MeV per He4 nucleus of about 4 GeV is about 10^(-2). We don’’t know how to construct Mr. Fusion yet, but who knows. The final rocket propulsion fuel would be particle-antiparticle annihilation, like proton-antiproton or electron-positron. The thrust or energy output to fuel mass is one to one, or 1. The confinement of antiparticles without unwanted annihilation is of course the problem.
The Breakthrough Starshot of Yuri Milner and Stephen Hawking is to blast essentially all of the power in California with a massive collection of lasers somehow focused on a square meter solar sail that doesn’t vaporize instantly, and accelerate it until it is out of sight. The payload is a tiny chip. The chips just do fly-bys, not deceleration and landing.
There is also ion propulsion, but that requires a lot of energy, which is still only as efficient as the sources mentioned above. The antiparticle annihilation supplies its own ions, or photons, but half of the ions have to be absorbed by the rocket to push it forward, without crippling damage.
Let’s not forget that much lower cost telescopes can detect signs of life elsewhere, with complete safety, and not requiring millennia to send out a starship and get a return radio signal. This will answer the first and most important question, as to whether we are the unique planet with life. Some people have a religious investment in this answer. The conditions for life also seem to have a lot of requirements attached to them, and it may be rarer than common-place.
Again, telescope arrays can give us the fastest and cheapest method of finding life as advanced as reaching an early scientific stage where they master radio waves, like we recently have.
Would receiving messages from advanced civilizations help us overcome our present challenges of inequality, global warming and nuclear weapons? We know most of the answers here already, but we are not all listening to our wisest people. We don’t need a planet B. We have a wonderful planet A. Nobody can comprehend the vast wonders of life on it, and we still have most to learn about it. Yet we are destroying a quarter of its species, due to unarrested greed. We wouldn’t treat planet B any better than we are treating planet A, anyway.