“Space” as many a great person has been oft to say “Is big. Very big.”
Whether this is a metaphor for the sheer incomprehensibility of the vastness of space to the human physce or a statement of the bleeding obvious is up to you, but it does essentially capture the number one problem with space. It’s big.
Actually the problem here is we think of it a big.
The units of measurements that are used to measure even interplanetary distances are so vast that conventional measurements (such as miles or kilometers) breaks down and turns into numbers that are stupidly high, high enough for most people to simply slap the “too fucking big” sticker on it and forget about it.
For instance every second light travels almost 300,000 kilometers a second, fast enough to lap the world about 7 and a half times a second. put into perspective it takes light some 8 minutes to get to earth. Now on the surface that seems, well quite far. It’s not really.
The problem here is that even though while light imposes a cosmic speed limit, earth is possibly one of the largest speed sinks in the solar system. We exist at the bottom of one of the strongest gravity wells (at the surface) of the solar system, second only to jupiter, dragging down everything We breath at the bottom of several dozen kilometers of air that presses down on everything, causing friction with everything. By cosmic standards, moving anything on earth is like moving through ultra-mollasses.
In the spirit of misquoting Einstein “Speed is relative”
Space doesn’t work like that. You throw something in space and it’ll fly until it hits something, no strong gravity to bring it crashing down, no air to slow it down. New Horizons, the fastest thing ever to leave earth orbit, was traveling at 16.26kms, and that’s positively a snail pace. It’s in fact slower than the relative velocity of “stationary” objects such as the earth to the sun.
In fact in terms of travel speed, what NASA has been doing is basically the equivalent of chucking paper aeroplanes. It throws them with strong arms, but then they basically glide until they get to where they want to go.
The travel time of probes such as Voyager and rovers such Curiosity isn’t because space is big. It’s because they’re slow. In fact for the vast majority of the trip they don’t “move” at all, they simply glide.
With an acceleration force of 1G (the same as earth), accelerating half of the time, and deacelerating the other half, you can make it to the moon in less than 3 hours from earth orbit, or about a third of what it currently takes to fly from Melbourne to Bangkok, and a fifth of what it takes to fly from LA to sydney. Travel times between the inner planets (mars, venus and earth) would be measured in a few days at most, while even transits to the ‘far’ planets such as Uranus or Neptune would be far shorter than say a trip between South america and China some 140 years ago.
So reader, now you’re wondering why NASA doesn’t move a little.
The answer is actually fairly simple. We’re at the bottom of a well. It’s not a particularly deep well, but it’s an extremely steep one. Earth is one of the densest planets in the solar system, and as such it has (as i previously said) a relatively strong gravity well. Of course being also relatively tiny this gravity well dies off quick, but the fact is that if we want to get anything into space at all we need to have large rockets.
And expensive rockets. very expensive.
At the moment it costs between 10,000-24,000 dollars a kg to throw anything up into orbit. This above everything else is the one cost in space travel that keeps us tied to the earth. Because despite how far we’ve come since the 60s, the launchers that NASA was planing to use to go to moon (via Constellation) would have been almost identical (except for the computers and control systems) to the Atlas V.
Before we can do anything really, we need a fix. We need a solution to the launching cost problem before we can even think of sending people to the outer planets, let alone putting any meaningful presence on the moon. Don’t even think about sending enough people to counter the earth’s natural population growth.
So what are the solutions.
One of them is to simply build a better “rocket”. I use the term rocket loosely. I mean anything you strap on the bottom of your spaceship, and use it to generate thrust to get out of the well.
The problem here is chemical reaction rockets are just about the most efficient they are ever going to get. You can’t “improve” the way that rocket fuel burns, you can regulate thrust better, a more efficent system, make a lighter rocket, but after that there’s not a whole lot.
You need something a lot more powerful than chemical fuel.
The first solution was fission rockets. This of course arose from the late 40s and early 50s, when the hot military ideas of the days included nuclear powered bombers. and nuclear powered cruise-missiles. There’s no reason why nuclear fission can’t power a cruise missile or even a rocket, the heat of the reactor providing power for a ramjet or the direct thrust of the fission providing the thrust in a vacuum. It even got tested in the 50s, as the aptly named SLAM.
But as people discovered kinda quickly, using fission rockets was a fast way to dying of radiation sickness, for you and everyone on the planet. SLAM never got beyond a few tests in Nevada.
The other is of the nuclear coin is of course nuclear fusion. In nearly all respects nuclear fusion is far superior to nuclear fission. It’s cleaner, more powerful, and fuel is more plentiful (well at least at a stellar level). Nuclear fusion’s only real drawbacks is
1) the fact that at present it’s nigh uncontrollable, but that’s a limit of our time rather than the theory, and
2) the fuel needed to pure almost completely radiation free fusion, He3, is extremely rare on earth. As it makes up a good portion of the Sun’s mass and as such is relatively plentiful on the solar winds (note- “plentiful on the solar winds is to be interpreted as, okay there might be more than a kilogram over a space the size of the earth) and as such planets without atmosphere, or with a very cold one and particular without a lot light tend to gather a lot of the stuff. Everyone who has watched Moon will get the idea. So fusion fuel would actually needed to be dropped from orbit, then used as fuel. Kinda counter-intuitive.
Variations on fusion, plasma fusion ect fall under that category.
The two other types of rocket are a bit too outlandish to consider. One is an antimatter rocket, which while extremely efficient has some inherent problems (namely the possibility of turning itself into a multi gigaton nuke at a mistake), and how hard it is to produce any meaningful quantities of antimatter (much harder than successful nuclear fusion).
The last is completely unviable except for quite large craft. it involves inserting a mirco-singularity inside the engine of a ship, then using it’s immense gravity to create nuclear fusion. Density is far more important in determining the surface gravity of an object than it’s total mass. Of course at a certain point enough mass (such as a blue giant) crushes itself down into hyper dense degenerative matter, increasing it’s gravity further.
Now like all radiation, including gravity, the inverse square law applies.the strong gravitational pull of the singularity drops off exponentially, limiting the “effective” gravity pull beyond a certain distance However at the surface it’s still enormous. Enough to cause nuclear fusion in any mass you happen to blast through it, thus generating thrust.
Of course how you would artificially create a type of matter that usually requires several hundred million and more than a hundred solar masses worth of mass to create is well as truly beyond me. A reverse application of the E=MC^2 might work, using energy to create matter at a single focal point rather than destroying matter for energy as we do with antimatter and nuclear fusion/fission. If so creating such a singularity would require a truly phenomenal amount of energy.
Even with a perfect energy to mass change, creating 2kg of matter would require 1.8×10^17 joules, since you’d need to create substantially more than 2kg in order to create a singularity, energy requirements would probably exceed yotta joules. if you want to see exactly how much energy that is, google it.
Both Antimatter and Singularity based drives are probably better kept to safely outside earth orbit.
However no matter what rocket-like system you use, there’s a fundamental problem with using rocket based systems over the long term to spacelift large amounts of mass. It’s called waste heat.
All these systems don’t reduce the amount of energy it takes to lift something up to earth orbit, or how this energy is releaed. In all cases your sending your ships up on pillars of fire. And all that heat has to go somewhere, namely into the atmostphere itself.
If you try to lift anything substantial (let’s say something mass of a moderately sized sea going vessel today) off the earth via this method, not only do you risk torching vast amounts the land below in your thrust, but you also risk creating freak storms and other weather systems due to the sudden release of heat. Do it regularly with hundreds of ships and over the long term you risk heating up the earth’s atmosphere faster than the heat can disperse, causing global warming.
There will probably always be a place for fusion hybrid scramjet/thruster space planes. if it be for lifting high priority packages from remote locations, military uses, or just the private transport of the shockingly rich. But you can’t use them for bulk transport.
As such, the rocket is an impractical tool for getting the tens of millions of humans off the earth (per annum) required to keep it’s population stable. You need a method that is fundamentally different in it’s execution.
So the second method of getting off the earth, that of Structural Orbital lifting. I call it structural lifting, because rather than firing rocket, we either climb, get shot off, or get pulled up by structures in space or earth that are large by our standards. Quite large. This includes Tether propulsion which includes skyhooks, orbital elevators, orbital fountains, and other tether structures, but also maglev based structures that essentially fire their payload out of a massive coilgun.
The first tether structures are hard to understand. Crucial to understand that while earth has strong gravity it’s also spinning quite fast, very fast, and things in orbit spin extremely fast as well.This is why the International space station is described as being in “free fall” it’s spinning around the earth so fast that the gravity from the earth can’t actually ever bring it down (well aside from a few booster bumps every so often), the relative velocity of the ISS is 7.7kms.
Now it turns out that between gravity and the centrifugal force of the earth you can do some cool stuff. Some very cool stuff.
The best known, and the one that stretches the human mind the least is the Orbital Elevator. Now because it’s one of the few i’ve stuided in detail, i’m not going to attempt to explain how orbital/space fountains work, i’m too much of a coward, so i’m just going to focus 0n elevators.
The concept is actually quite simple. It’s the same as the effect that you have when you spin a ball on a string around your hand. The rapid rotations and the centrifugal force on the string (well, in actual fact centrifugal force is a pseudo-force, it’s inertia but for simplicity’s sake that’s what i’m going to refer to it as).
In an Orbital elevator, the earth becomes the hand, the space station becomes the ball, the rotation of the earth becomes the force, and all you need then is an extremely strong string. Gravity and centrifugal act against each other, and up until geostationary orbit (36,000 kilometers or so) gravity wins, but past that centrifugal force is the stronger of the two, so provided you have an equal amount of force acting on both sides of the boundary (which can either be distance or mass, the force increases with distance at both end), the string is kept taunt.
Of course one of the main barriers to the concept is you need an extremely strong matieral to make the cable out of, something of incredible tensile strength. Carbon nanotubes are the current idea, but MIT has just barely managed to make a few cm of the stuff, let alone tens of thousands of kms, and it’s not of sufficient strength. Of course, that’s once again a limitation of our time not of the concept.
There’s more to it than that of course, but that’s the basics. The essence of the space elevator is it gives us a literal “rope to heaven”, a cable we can swindle up without the use of rocket as at all.
At it’s most basic, you have the aptly named “crawler”. the crawler is basically a glorified skiing gondala that climbs up instead of down, except since the cable doesn’t move itself you have to actually “crawl” up it. A crawler moves at a cosmic snailpace, literally taking days to get up to an altitude that modern rockets can make in hours. And the lift capacity isn’t great.
Now as i said, in order to keep earth from imploding due to population pressure in the long term you need to lift off millions of people. Obviously that means a lot of elevators, but it also means elevators capable of handling a lot of traffic. So you need something a fair bit faster than the crawler.
One idea is the vacuum train. It works on the same principle as the as we currently use for maglev trains today, and what the US navy uses for their experimental railguns. By starpping a vacuum sealed tube to the side of a orbital elevator, along with a whole load of super conducting magnets along the tube.
You then take a train, perferably traveling at a substantial velocity, and fire it up the tube, using the magnets to produce a progressive coilgun effect, accelerating the train up the tube.The benefits are good. With multiple cables you could have dozens of trains running at hypersonic speeds at earth level, to orbit and back each day, from stations all over the world. It’s fast, efficient and clean. In fact if you manage to get your train moving at Mach 5 (1.6 kms) before you even begin to ascent (probably via a very long ramp and an existing planetary vacuum train network) you don’t actually need to accelerate the train. All you need to do is keep it moving at it’s present speed, countering the 1G gravity pull of the earth, and the train will be some 100 kilometers up within a minute anyway, and since gravity falls off with distance, the energy needed to keep it going quickly drops.
The problems with this system are actually quite simple. first of all you need an ungodly amount of energy (but not nearly as much as attempting to create a singularity!) in order to keep something that weighs several dozen tons accelerating at a bare minimum of 1G for even a minute would be a serious strain on power grid. Assuming that the train weighs some 50 metric tonnes, you’d need to apply a force of half a million newtons per second, or 1,800 Megawatt hours if you had to accelerate it at that force for an hour. And this is provided for perfect efficiency, which of course won’t happen. Running dozens of trains concurrently is well beyond our current energy production, but not beyond nuclear fusion. Furthermore since carbon nanotubes condusct electricity you could even send energy from massive orbital solar arrays back down, powering the trains on the way. Either and both work.
The second limitation is you need a cheap, high temperature superconductor, both to manage the immense amount of power and to act as the magnetic accelerator rings.
Eventually you could catch a train from London to a space station 60,000 up in less time than it currently takes to fly to bangkok. the first leg of the journey down to a elevator down near the equator, then straight up.
Of course, if you want to build a bona fide spaceship, the ones that never grace atmosphere or go anywhere near a gravity well, then it’s still too expensive to actually haul matierals up.
Simple answer- don’t. The space industry will be dominated by the moon rather than earth, producing the bulk of the space stations, ships and anything else as it doesn’t have any of these problems with getting off the surface that earth has. Perhaps more interestingly, Most people on earth are at a base level incapable of grasping the reality of space, it’s vastness. It’s a weakness in our society that ultimately jarred the space race rather than anything else. Space travel is far from impossible, but most people on earth would like to think that it is. In our hearts of hearts the concept is just too strange to actually consider outside the purview of science fiction. That’s soft science fiction always has a nice safe disconnection from the present. Star wars is in space yes, but it’s in another galaxy, safely shies away from null gravity, phsyics in general and any relationship with earth in general.
But more on that next time.