I’m sure at one point we’ve all dreamed about zipping around the galaxy in a spaceship like Star Trek. To explore the unknown and see the beautiful wonders that are sure to exist out there. But why haven’t we yet? Will it ever be possible?
The short, simple answer as to why we are not taking day trips to Alpha Centauri, is because of energy. Energy is the key to exploring the stars.
Right now, we currently use rocket fuel to lift payloads into outer space and escape Earth’s gravity. Unfortunately, rocket fuel is heavy and expensive. It also is very slow. Voyager 1 and 2 were launched from earth way back in 1977 and are only now just exiting our solar system. Space is immensely vast. We don’t have enough rocket fuel on our planet to send a ship to our nearest star within a human lifetime, let alone explore the galaxy.
What are the alternatives?
There are a few alternatives. Some are already a reality, some are just hypothetical. We’ll list them here, then explore the benefits and drawbacks of each:
- Nuclear Propulsion
- Ion Drive
- Solar Sail
- FTL Drives
Nuclear propulsion is not a new concept. There are many different types of nuclear propulsion, but the most promising for speed is nuclear pulse propulsion. And surprisingly, is actually a fairly old concept. It was developed back in 1958, led by Ted Taylor at General Atomics and physicist Freeman Dyson. The project was named ‘Orion’.
The project required a spaceship to drop small nuclear bombs behind it, and a buffer or “pusher” plate would absorb energy from the detonation and the ship would ride the shockwave of the bomb. Since space is a vacuum, you could continue to drop nuclear bombs out behind your ship and continue to increase your speed to mind blowing velocities. Some proof of concept was tested during the 1954 nuclear test series at Bikini Atoll which showed that nuclear explosives could be used for propulsion.
Recent calculations show that it could be possible to achieve 12% the speed of light. This would allow a human to travel to a few of our nearby stars within a human lifetime. Since 1998, the nuclear engineering department at Pennsylvania State University has been developing two improved versions of the Daedalus design known as Project Ican and Project Aimstar. Their research has been very promising.
Ion DriveAn ion thruster or ‘ion drive’ is a form of electric propulsion used by spacecrafts that creates thrust by accelerating ions. The thrust created is incredibly weak when compared to chemical rockets, but it has very high specific impulse. That means that while the thrust is very small, it can be held for a very long time requiring less fuel than its chemical counterpart. Over the course of months to years, incredibly high speeds can be attained.
While extremely more efficient than chemical rockets, it’s still has the same limitations. Fuel. The faster you want to travel and the further you want to go requires exponentially more fuel. Once you reach a certain point, it no longer becomes feasible to use ion propulsion. Ion propulsion is great for short jaunts around our solar system — we’re actually using them right now on the Dawn probe and the upcoming LISA pathfinder missions. Unfortunately, an ion drive won’t allow us to explore our galaxy, nor reach our nearest star within a human lifetime.
Solar SailA solar sail is a sail made of CP1, a lightweight aluminum coated fabric that is thinner than a human hair. It works just like how it sounds. The sail is deployed and as the suns rays hit it, it gives it a small push. These ‘small pushes’ over the course of time add up, and can allow a starship to achieve high speeds using only the power of the sun.
The drawback to such a device is that not only does it take a long time to achieve a relatively decent speed, the further you get away from the sun, the less acceleration or “push” is available. We could try using high powered focused lasers to give an added boost, but over time and distance, even those would become useless. In addition, to push a starship which contains humans and the equipment they need would require a sail hundreds of miles wide.
This is the most powerful fuel currently known to man. A gram of matter and gram of antimatter colliding would be equivalent to the bomb that was dropped on Hiroshima. Which makes it the best candidate as an energy source to go sightseeing in our galaxy. It’s nearly 100% fuel efficient, and the amount of fuel required to take us to our closest stars within a human lifetime would only be the size of a few sugar cubes. The way it works is relatively simple. Antiprotons are shot out the back of a ship which strikes a uranium coated sail which produces enormous thrust.
The drawback is scarcity and storage. We currently only have the technology to create a few atoms of antimatter at a time in particle accelerators. These require massive amounts of energy to run. According to researchers at the LHC, it puts the going rate for antimatter at $24 thousand trillion dollars an ounce. And how do you store something that is destroyed when it contacts normal matter? Researchers are optimistic, they’re currently experimenting with magnetic fields and liquid nitrogen which has been semi-successful. They have been able to store a tiny amounts for short periods of time.
FTL or ‘Faster than Light’ drives are seen in many science fiction TV shows and movies. From Star Trek to Battlestar Galactica, they offer tantalizing alternatives to conventional space travel. But is it just science fiction? Will we ever discover technology which allows us to travel faster than light?
Maybe, maybe not. One such way is a warp drive. Normally the stuff of science fiction, it may one day be science reality. In 1994, Mexican physicist Miguel Alcubierre proposed a method of stretching space in a wave which would in theory cause the fabric of space ahead of a spacecraft to contract and the space behind it to expand. A loophole in the laws of physics.
This means you wouldn’t actually be traveling faster than light, the space around you would be. You would be riding inside a bubble of space that is zipping through the galaxy at speeds that are faster than light. We’ve all learned that nothing can travel faster than light, but there are no laws against space itself traveling faster than light. In fact, it already has. During the Big Bang.
However, there are some serious problems with wanting to build a warp drive. The most glaring is energy. The power that is required to warp space around a spaceship is equivalent to the mass of Jupiter. You would have to contain and harness the power of our largest gas giant in your spaceship. We are thousands of years (or more) away from attaining or inventing that kind of technology.
Also, exotic “negative energy” is required to maintain the bubble. The existence of this exotic energy is currently only theoretical, but the Casimir effect and the accelerating universe both lend support to the proposed existence of such energy or force. Though, even if it existed, harnessing it and using it would still be an issue.
So will we ever explore our galaxy?
Maybe one day we will, but not anytime soon without radical advancements in technology and science. Our biggest current limitation is energy and we simply don’t have the capability yet to harness the amount required to explore our galaxy. But that doesn’t mean we shouldn’t stop dreaming. Stephen Hawking said, “The human race shouldn’t have all its eggs in one basket, or on one planet.” Which is all the more reason we should leave our cradle.
“Imagination will often carry us to worlds that never were. But without it we go nowhere.” – Carl Sagan