# Is general space-travel really even possible or just a hollywood invention?

General Spaceflight: Normal people can buy fares or own private spacecraft. I'm using the word 'general' as an analogy to 'general aviation' - the (mostly-american) private aviation sector where many private citizens own their own planes.

### Why I do not think it will ever happen, please prove me wrong

• Spaceflight is incredibly expensive
• Spaceflight is resource-consuming
• We have no existing technologies that have eliminated these barriers, even our cheapest commercial space endeavors are far out of reach for an average citizen to utilize on a regular basis.

The world is getting poorer, and resources are going to become scarcer as we continue to multiply and consume them. I just don't see a future where humanity travels to other planets and settles them. More than likely, we reach our 'peak' and enter a long age of austere and sustainable lifestyles.

• When you say "spaceflight" do you mean getting to Low Earth Orbit or other planets or other star systems? – Schwern Feb 23 '17 at 3:14
• For simplicity, let's leave out Low Earth Orbit from the definition since it has significantly lower delta-v requirements. – AuthorizedUser Feb 23 '17 at 3:17
• Then the answer is a profound "no". We haven't put a human past LEO in decades. I'd suggest you ask only about LEO, that's on the horizon. Anything else is billions of dollars. – Schwern Feb 23 '17 at 3:21
• Does it fit your question if the spaceships travel in space but not from a planet? (for example, they're put in orbit through an elevator) – PatJ Feb 23 '17 at 16:39
• Getting from Earth into LEO and from LEO to Mars (soft landing) requires about the same delta-v. – Alexander Feb 23 '17 at 18:37

Yes, it's possible. Technology finds a way. Right now the energy requirements require billions of dollars to achieve the delta-v... but the amount of energy available to the average American is amazingly huge compared to one hundred years ago, or even 50... 25 years ago.

As you say, General Aviation tends to be a mostly American mainly because even General Aviation takes a massive amount of energy to accomplish. It started with a few rich pioneers, and started trickling down into more of society... but it's still a "upper middle class" activity... due to energy constraints.

I am not a malthusian nor a catastrophic boiling planet believer.(*) In the history of our planet, we've constantly discovered ways to increase the energy budget of everyone. Everyone's energy budget isn't EQUAL, but just about everyone has more energy available now than they did in the past. Right now it's all fossil fuels, but we've been working on alternative energy sources for a while, and I have to believe we're only going to get more and more efficient.

Right now we're in the very early days of spaceflight; due to the much larger energy and life support requirements, (You can bail out of an airplane. You can land an airplane on any arbitrary flat surface. The atmosphere allows you to control flight without power... there's a few other advantages moving about an air envelope provides...) we're definitely advancing, but we are still in the "pioneering aviators of WWI" zone. From here it looks impossible that anyone who's not an astronaut or fabulously wealthy will ever fly in space, just as it looked to be a rich person's toy or the government's plaything in 1915.

There's more options for interplanetary delta-v than there is for escaping our gravity well. Once you've made it into space, there's way more options available for changing your delta-v, but getting off the ground is our sticking spot right now. We're working on cheaper fuels and more efficient ways to gain altitude. What we're waiting for is some sort of "Black Swan" event to make this bit easy or trivial. Discovering a way to exert control on inertia, or a cheap antimatter drive, or anti-gravity would make this bit much cheaper and easier. I'm not saying anti-gravity is definitely coming! But I am saying nobody expected jet engines to utterly change aviation. Or carbon fiber. Or high-precision avionics. Or portable weather radar. It used to be only the richest of the rich could fly a glider or get a seat on one of those giant metal blobs we used to call airplanes. Now a moderate well-to-do person can buy a Piper Cub and skip around the USA for relatively cheap, and almost everybody in the USA has the ability to ride in a jet at least once, with some of the more constricting airlines providing travel for a similar cost as the bus lines.

TL;DR TO SUM UP:

• Spaceflight is currently incredibly expensive
• Spaceflight is currently resource-consuming
• We have no existing technologies that have eliminated these barriers

Breaking through these barriers looks as unlikely as heavier than air flight looked in the late 1800s; the costs for space travel now are on the order of the earliest pioneers in space.

I think we got spoiled by airplanes. In the space of 20 years, we went from powered kites to war planes; in another 20 we had solid steel construction planes. 20 years later everything was jets, 20 years after that cockpits were mostly automated with onboard sensors, 20 years after that planes were fly-by-wire and made out of advanced composites. This is a VERY rapid advance in technology. (Computers have evolved even faster.) So we look at Apollo and go "Where is my backyard rocket already?!"

I think rocketry is more like sailboats. Humans have been sailing for thousands of years. Only the richest merchants and the most powerful governments could afford to do it at first; the knowledge required to build a functional sail, and a sturdy water-tight boat, was way beyond the means of the common citizen, for much of our history. Eventually, though, as with aviation, even private citizens eventually gained the ability to rig sails on small boats; technology innovations in sailmaking materials, GPS navigation, food storage, and the like have made it more and more likely that a general citizen can boat around the ocean and survive. Even today, I'd put this as a middle-class activity in most of the world.

If spaceflight is like sailing, you and I aren't likely to see "general spaceflight." It may take hundreds of years before your standard middle class citizen can fly their shuttlecraft to the moon. But I wouldn't put it past ourselves.

• To put the arguments to bed; I'm not claiming climate change is not real or anything stupid like that. I just don't believe that the predictions coming out of the GIGO computer models are realistic, and I'm not convinced that human CO2 emmissions are the leading cause for climate instability. I'd also state that I believe we must keep our current energy system until we have something better, because making better solar panels and wind farms and cow-fart-trapper generators requires the very modern high-energy society we currently enjoy in the west... but I also believe strongly that we aren't, as a species, suicidal, and we'll switch to better tech when it's actually energy efficient to do so while keeping our standard of living up.
• You sailboat analogy is a bit off. Pacific Islanders were cruising hundreds, if not thousands, of miles in pretty primitive sail driven canoes. Granted, they couldn't carry much more than themselves in them, but it could be done pretty economically with the right conditions. There isn't really a comparable spaceflight comparison. – Jason K Feb 23 '17 at 17:46
• You're right, @JasonK, I was thinking Western sailing. Necessity's the mother of invention, and Pacific islanders HAD to be able to navigate the ocean, so they figured it out. Most Western civs had plenty of land; only traders like the Phonecians cared about sailing, really, until the big empires of Europe used sail to spread their dominions. Part of the problem with spaceflight is, unlike the Pacific Islanders, we don't NEED to get off this rock; there isn't the huge rush to find any economic solution to the problem. The question was about general aviation; commodity flight for flight's sake. – Zoey Boles Feb 23 '17 at 20:20

# We Haven't Been Beyond LEO Since 1972

The last time we put a human past Low Earth Orbit was Apollo 17 in 1972. We'll start doing it again in a decade or two as various government and commercial Lunar and Mars programs get started.

# Reusable Rockets!

The cost of getting to space has been likened to flying to Europe in a disposable jet; pretty damn expensive. The Space Shuttle was supposed to fix that, but it didn't fly often enough to recoup it's immense costs (it was supposed to shuttle to a space station, but that didn't happen until late in the program), and it was too big.

SpaceX has been successfully landing its Falcon 9 rocket for about a year now. The rocket lands on it's tail like a 50s sci-fi movie. There were many explosive failures, all part of the plan, and they seem to have the hang of it now. SpaceX has yet to reuse a rocket, it plans to do so in April 2017. This is only possible due to advances in computers and material science, as well as the commercial pressures to cut costs. While each rocket can launch less cargo, they have to hold onto some fuel for landing, their reusability will theoretically slash costs.

# Air Launch

The other innovation for private space flight is air launched space planes. A lot of a rocket's thrust gets used up just pushing through the thick atmosphere. This is why rockets go up and then turn to gain orbital velocity, they want to spend as little time fighting drag as possible.

An alternative idea is to fly the spacecraft as high as possible with a conventional airplane, then release it in the thin atmosphere to fly to space. This is what Virgin Galactic is going for. They're currently testing a small, sub-orbital space plane (it will get to space, but not orbit) launched from a carrier plane at about 16km. The price is a cool \$250,000. They also plan to launch satellites using this system. They plan to start testing launches from a 747 this year. # Getting To Mars On The Cheap But none of these is going to get the price of getting to orbit down to$1,000 or even $10,000. We will see$100,000, but that's still outrageously expensive. Such is life at the bottom of a gravity well.

If you want to get to space on the cheap, you could try to volunteer for a commercial Mars mission. There's various in the works, but SpaceX seems most likely. Their stated long-term goal is to colonize Mars. If they pull it off, they're going to need people to send to Mars! It might be a one-way trip, so they'll need volunteers who are skilled in multiple disciplines, mentally sound, and ok with dying on Mars.

# Climb To Space!

The basic problem with all rocketry is the rocket has to carry all its fuel with it. This adds weight, so it has to carry more fuel to carry the fuel. And more fuel to carry that fuel. And so on. This is known as the Tyranny of the Rocket Equation. It means that in order to get to LEO about 90% of your mass is going to be fuel.

The Holy Grail of space flight is to somehow defeat the rocket equation. Getting out of Earth's gravity well is particularly difficult because while there's some very efficient engine designs out there, they don't have the raw thrust to reach orbit against gravity and through the atmosphere. But there are alternatives.

The Space Elevator and the Launch Loop both use the same idea: attach the craft to some sort of tether and get it into orbit using power from the ground. This avoids having to carry all that fuel, but it does involve a massive up front investment. They could, potentially, slash the cost of getting to space to something a middle class person could do as a major vacation.

A Space Elevator works on he same principle as a spinning a ball on a tether. You put a counterweight beyond Geostationary Orbit (no small feat) attached to a cable on the Earth. Centrifugal force will keep tension on the cable and if it's all balanced just right, it will remain vertical to the Earth.

Now instead of a rocket, you climb to space! Power would come from the ground, possibly from lasers. What's more, you're not just climbing up, you're gaining orbital velocity. By the time you reach space, you'll be in orbit and can just let go. No fuel required. Make the cable longer, and you can achieve escape velocity.

This has the potential to massively cut the costs to get to orbit and beyond. Unfortunately, there are two major problems. First, no known material is light enough and strong enough to withstand the tension. Second, it's still a long climb, and we're just starting to do the engineering to power things with lasers. How far out this is is unknown. With a breakthrough in material science it could be 20 years, or it could be never.

A Launch Loop looks even nuttier. It's a cable 2000 km long and 80 km high and anchored at both ends. It moves like a conveyor belt and that force causes it to arc into the air and stay aloft. Payloads ride the loop like a maglev train and let go when they reach orbital speeds.

Unlike a space elevator, it does not require exotic materials, but there's a lot of engineering to be done to show it's feasible. Also the tiny problem of finding somewhere to put a 2000 km long structure spinning with the energy of a 350 kiloton bomb and powering it.

Those are some of the near and not-so-near future technologies that will cut the cost, economic and otherwise, to get to space. Some of them, like reusable rockets and a commercial colony on Mars, will happen in a few decades. Others, like the launch loop, could maybe be done in our lifetimes with the money and the will. While things like the space elevator are indefinitely postponed pending new material discoveries.

• One hell of an answer. I'm reading it for a second time. – AuthorizedUser Mar 9 '17 at 20:59

In 1950 standing around on the moon like awestruck tourists was just a Hollywood invention. By 1970 it was old news.

Never underestimate the future.

• Although, I'm not predicting that I will be taking off-planet business trips within the next twenty years. – A. I. Breveleri Feb 23 '17 at 19:12

Yes. We can do it if we want to.

The big problem is getting out of Earth's gravity well. Once up, everything is much easier.

With a base on the Moon, we can build vehicles and make rocket fuel. Fun fact: it is 200 times less expensive to lift something off of the Moon and send it to low earth orbit (LEO) than it is to lift it from the Earth to LEO.

The big kicker for interplanetary travel is radiation. We can add radiation shielding but that takes mass. It would be much less expensive to lift that from the Moon.

I believe that with current technology, we could lift enough people and equipment to the Moon to begin mining it for the material needed to get to the asteroid belt where we would have access to lots of resources without the annoying gravity wells.

Right now, if they were to send the planned manned mission from Earth to Mars, the half that survived the trip would need bone marrow transplants. 6-9 months outside our magnetic field and thick (relatively) atmosphere does bad things to people.

Answer is no, it's not possible YET.

Currently cost of launching one kilogram of mass into space is at least few thousand dollars and only government and huge corporations such as Spacex can afford it. Why is it so expensive? Because you not only need to pay for spacecraft fuel and maintenance, but also for spacecraft themselves, which are not entirely reusable. All rockets today are made from few separate stages that get jettisoned away one by one into the ocean as their fuel burns down. So basically it's like if you had to throw your car away every time you come back home from work.

Fortunately new technologies are on the way. SSTO (single stage to orbit) spacecraft such as Skylon are being developed right now. This would eliminate the need to reconstruct your entire vehicle after each flight. Also fusion power is soon to be harnessed, just imagine a plane with engines powered by nothing more than heat from fusion reactor and atmospheric air or a manned Mars mission using plasma/ion engines many times more powerful than any of those mounted on modern interplanetary probes!

Possibilities are almost there, we just have to wait.