The [Final] Frontier - Space Part Four, The Finale

Space travel is mindboggling to think about. Space is so utterly massive, the distances so unfathomably enormous, that our perception of speed is rendered stunted. Things we consider fast here on Earth become laughable when measured against the distances between stars.

Trying to reach the closest star to us not our Sun with our current technology would take more time than we’ve actually lived as a species on this planet. With our current technology, if you left before the last ice age, you would still be on your way to just that next closest star. A probe we launched into space four decades ago is only now reaching the edge of our solar system. To put it simply, we are not going to get too far in space with our current technology.

So we obviously need to come up with a better way of getting about in space. Luckily, scientists have a few ideas.

The simple problem is propulsion. Fuel weighs something. Because fuel weighs something, it has to be included in the calculations in determining how far and fast a space vehicles (or any vehicles anywhere really) will travel. Thanks to the bane of speed junkies anywhere, Einstein’s E=mc², the amount of energy you need to increase speed is dependent on mass, but as you go faster you likewise gain mass, therefore you will reach a point where you will become super massive to the point that there is not enough energy in the universe to help you gain speed. That is the crux of the challenge of space travel right there – how do you get power to move without adding weight from all that fuel.

As a result you need to eliminate weight as much as possible. One way of helping that process along would be as I’ve noted in past posts is this series is to build, fuel, supply your ship in space. We use up a lot of fuel just getting our vehicles out of the Earth’s atmosphere and escaping Earth’s gravitational pull. Putting that to use on a ship already in space would be at least a range booster.

But that doesn’t really solve the main problem, which is the chemical rockets, chemical fuels, are not conducive to particularly fast space travel. They simply weigh too much and release too little useable energy.

The first alternative is concussive pressure plate acceleration. The concept is very simple. The utility is very dangerous. Essentially you take your ship. Behind it you have affixed a pressure plate and shock absorbers. Called nuclear pulse propulsion, you detonate a nuclear bomb behind the ship. The detonation strikes the pressure plate, which pushes against the ship. Because you’re in space where there is no friction once you attain a direction and speed, you don’t lose speed. There’s also no tail winds so you’re not going to gain any speed either. So you detonate another nuke. That boosts you forward again. The idea is that you keep detonating nukes behind you, repeatedly boosting your speed.

This idea works in theory. You can test it with conventional explosives (well YOU shouldn’t, but researchers can and have). The problem is that you are using nukes. The use of such a system for trying to escape Earth’s atmosphere would cause widespread radiation fallout (hence why we started with a ban on testing nukes in the atmosphere). There is also the issue of the durability of a craft for such a propulsion system being that you are essentially repeatedly blasting a ship with nuclear bombs. And of course there is the impacts on the living inhabitants of the ship.

The good news? This form of propulsion, using our current technology could conceivably get a ship to 1/10^th the speed of light. The bad news? That would still mean 44+ years to reach Alpha Centauri. So, it would be conceivably doable, but it would still be an incredibly long time.

There is also another variation of the same theory, which uses nuclear fusion, fission, and antimatter. The idea is that you introduce antiprotons into the nucleus of normal matter. It reacts with the protons, self destructing. This causes a fission reaction at a more efficient means than conventional nuclear fission. The split apart matter could then undergo fusion, releasing more energy. You would essentially repeat this process in conjunction with the nuclear pulse propulsion setup, using the concussive force of the energy releases to push your ship to incredible speeds.

The good news with this one? Like the straight nuclear option we more or less know exactly how to do it. Furthermore this method could get a ship up to 80% of the speed of light. That makes that trip to Alpha Centauri only about five and a half years – not exactly a run to the grocery store but not bad at all for the distance. Bad news? We don’t have antimatter, and if we don’t do everything absolutely perfectly, the antimatter could come into contact with matter causing a runaway reaction and destroy the ship, everyone on it, and possibly a huge area around the launch pad.

So, the explosive options are worrisome. How about something with a little more elegance? What can be more elegant than sailing through space with a ship that’s powered by a sail? Solar sail technology is another one of those elegantly simple concepts that is really difficult to accomplish.

A sail has to be thin, lightweight, and durable to move a ship across the seas. Weight/mass impacts Einstein’s equation. It also makes it difficult for the propelling medium to act effectively. Make it too thin and lightweight and it’s liable to be torn easily, which would make it useless. That all applies doubly for a solar sail, which uses light energy (photons) to gain speed and momentum, the same way a regular sail captures the wind. The beauty of a solar sail is that it doesn’t necessarily need the sun. Like putting a fan to your sail on a tiny sailboat, you can artificially accelerate a solar sail vehicle by way of a rather rudimentary laser projecting light onto the sail.

So, good news is that this will work and we do have the right materials to build a solar sail. The bad news is that while a solar sail will eventually get a ship up to 1/10^th the speed of light, the process of doing so is rather slow. Light doesn’t exert much force, which is a good thing because if it did we’d all be dead. As with the pulse propulsion system you’re more relying on building momentum rather than the relative instantaneous speed of a chemical rocket. In other words a solar sail vehicle will have the acceleration of a drunken turtle, but the top speed comparatively of a fighter jet. The caveat, it never fully runs out of fuel. You run out of nukes or antimatter for your pulse propulsion system, you’re stuck wherever you are. There is tons of background radiation and photon emissions traveling through space, which is all a solar sail vehicle needs to move, eventually getting to that top speed.

So, is there some way to get even faster? So far an antimatter pulse propulsion system is the fastest, but most unattainable and the moment and potentially most dangerous. And in fact scientists have yet to stumble onto anything directly faster. But there is a loophole… or rather a wormhole.

Wormholes have been suggested to exist by the same equations that are used to establish the physics of the universe. Problem is we haven’t seen any. If they do exist, or we could create one, the basic theory is that they are shortcuts to other parts of the universe. So let’s say you’re in your bedroom and you want to get to your friend’s bedroom in the house four houses down from you. You’d have to go out your room, out your house, down the street, through the front door other their house, and work your way through their house to their bedroom. Not an overly complicated bit of travel. But what if instead you could cut a straight line trough your wall, through your kitchen, living room, thorough those four neighbor’s houses, and right into that friend’s room? Assuming you traveled both routes at the same speed, you just cut the distance you travelled by not having to make all those turns. You effectively raised your average speed because you covered the same amount of physical distance in less time. We learn this in grade school – the shortest distance between two points is a straight line. That is what is perceived through wormhole travel.

The basic assumption is that space is curved, the same way the planet is curved. A wormhole bisects this curvature of space and creates a shortcut. If you go through one end, you pop out the other at your target destination – like taking a tunnel through a mountain instead of driving over the mountain. This allows you to essentially cheat the speed of light, covering the same effective distance (25.73 trillion miles to Alpha Centauri) in a much shorter time.

The good news? Wormhole travel could get you almost anywhere in the universe in a fraction of the time of any other mode of transportation, even possibly faster than the speed of light. That means going to Alpha Centauri could take less than the four years and three months it takes light. Best of all we wouldn’t need to go about making supremely more complicated ships to traverse space since it would be like opening a door in your backyard and coming out the other side wherever you were planning to go. The bad news? Wormholes remain only a theoretical construct of space. We haven’t seen one, can’t make one, so we don’t even know for sure if they actually exist. As such we have no clue how they work so as to say if you could even use one to travel or how close it would get you to where you want to go.

That leaves one conclusion – space travel technology is a necessary and difficult obstacle. Consider this; I’ve only been talking about the nearest star to us in our galaxy in the Alpha Centauri system, which is a distance of only about 4.24 light years (Proxima Centauri). The visible universe, as seen from the Hubble Space Telescope, stretches a mind rending 15 Billion light years. Yes, BILLION! That means if you could travel at the speed of light it would take 15 billion years to get to the farthest visible star. You would need one heck of a speed boost to hope of even seeing that star up close.

It can be a little disheartening if you have dreams of travelling through space and visiting distant worlds to realize how monumental a task that really is. That said, each monumental task requires taking one step. One step at a time. There may be speeds yet attainable that we don’t have a clue of how to even measure yet. Or technology that conceptually shrinks the universe to a more manageable size. If we just take the next step, there’s no telling what could happen.