The movies make it look easy: Humans landing on new planets and ships moving around the galaxy with ease. Well, reader, it isn’t that easy…like getting along with the in-laws it takes a lot of work and time. We may see the Chicago Cubs finally win a World Series again before we send a man to Neptune. Here is a guide to teach you the basics of traveling to and from planets and stars – and why even NASA has their brains tied in knot over this stuff.

Introduction to Interplanetary Travel

Traveling between planets gets a lot of tough love. It’s cool to theorize and understand (that’s why you are reading this), but some of the time wasteful in execution. There are plenty of botched launches and space travel horror stories out there to turn a proponent into full skeptic. Remember the Beagle 2?

Don’t you wish $68 million was spent elsewhere?

Okay, accidents happen and traveling to another planet is cool – why aren’t we doing anything about it? Well science pundits conflict over how much the human race can benefit from exploring other planets. Lots of ideas seem like pipe dreams out of a pulpy science fiction novel; asteroid mining, harnessing energy from solar panels and space colonization to avoid a catastrophic asteroid impact.

Others believe the observations taken from first hand probes of planets nets our society invaluable information, regardless of its immediate application. Once scientists get past the premise, they are in conflict over sending man to planets or keeping it exclusively robot helmed.

Breaking Down the Theories

All theories regarding interplanetary spaceflight must overcome two primary feats:

1) Adjusting the speed of travel. The planet of take-off is moving at a different speed than the landing planet. This is because planets are not the same distance from the Sun. For any planet further away from the Sun, this requires an increase in speed.

2) In addition all planets further away from the Sun require the shuttle to overcome the force of the Sun’s gravity.

3) Oh yeah, transporting a ship hundreds millions and sometimes billions of miles away without running out of fuel and/or blowing up.

But really…the main problem is managing energy distribution to control the ship’s velocity.

Hohmann Transfers

Walter Hohmann originated this theory of space travel in 1925. The idea isn’t too complex: Launch a ship in an orbit that will meet the destination planet’s orbit at its tangent.

Simple AND easy to draw.

Why This Works Well: Hohmann’s idea is great because it is one of the lowest energy routes between any two orbits. A ship only requires a little thrust to propel it into the destination orbit.

Why This Doesn’t Work Well: You have to wait too long for the planet to catch up. The main flaw with a Hohmann Transfer is the delay between entering orbits. Planets close to the Sun are fine, like Mars, but outer planets require many years for the planet to near the waiting ship and that is too long for many missions. Also, the further the planet from the Sun, the harder it is to accurately produce calculations necessary for travel. Yes, there is a point where even MIT manned computers can produce unreliable readings.

Read more about the Hohmann Transfer: http://www.absoluteastronomy.com/topics/Hohmann_transfer_orbit

Can you blame them?

Gravitational Slingshot

This theory, developed in 1959, allows spacecraft to reach those distant planets in shorter time and with less fuel than with a Hohmann Transfer. The ship uses the gravity of nearby planets to alter its path and speed.

Clearly, the velocity can be doubled.

Why This Works Well: We use gravitational slingshots because it saves a lot of fuel, time and expense compared to a Hohmann Transfer. This method has worked well for the Voyager program to slingshot the probes around to the outer Solar System.

Why This Doesn’t Work Well: If planets didn’t orbit then this theory would be perfect but also be useless. That’s the inherent limit to this method of planetary travel. Because planets aren’t always where we need them to be, much of the time a gravitational slingshot is out of the question for travel. The Voyager missions in the 1970′s won’t have the same alignment of planets until the 22nd century. It was a one trick pony. So travel by this method is severely limited to the alignment of the planets and other celestial objects.

Read more about Gravitational Slingshots: http://www.mathpages.com/home/kmath114.htm

No way toothpicks are an adequate metaphor for planetary orbit.

Fuzzy Orbits

Thanks to modern advances in computer technology, we are now capable of calculating the trajectories of lesser gravity fields of astronomical bodies. These are called fuzzy orbits and are even slower than Hohmann transfers but require significantly less energy. They are most useful for transportation of cargo, not research missions.

Difficulties of Sending Man to Other Planets

Whether or not we end up sending man to distant planets is beyond this column, but the feasibility is an interesting discussion nonetheless.

Humans face the problems of life support and survival from radiation. Traveling between planets requires months and years. So the problems of rationing food and maintaining a breathable atmosphere are of concern. Outside the protection of Earth’s magnetosphere lies the Van Allen radiation belt. Here, astronauts are at the mercy of intense cosmic rays which will kill you over time.

James Van Allen – The REAL reason no one wants to travel to another planet.

In addition, spacecrafts are at the mercy of accidents at any time, where many of them are impossible to repair while in space. Even if we decided to send man to another planet there are constraints of accessibility. Only for certain time periods are planets reasonably within reach with regard to resources and even then, the trip back may never be possible in the crew’s lifetime. Apollo 13 is a poor example of the hijinks that can really go down in outer space.

Introduction to Interstellar Space Travel

Ask an astrophysicist about interstellar travel and they may refer you to the science fiction section at your local library. True enough, the idea of traveling between stars is probably further on the academic back burner than reviving the dead. It’s not just because Alpha Centauri, the closest star system, is over 4.23 light years away (25 trillion miles).

Okay, that is the real problem.

The future of mankind? Sid Meier was on a whole lot of drugs when conceiving this game.

Be thankful the geniuses over at NASA still daydream about this type of exploration so there are a few theories on the table.

Initial Difficulties of Interstellar Spaceflight

Every couple of years a bunch of scientists gather in a large room to discuss the nature of interstellar travel. Ideas are thrown around and arguments ensue until everyone kind of agrees that traveling to other stars is dumb and there is no realistic way to power a ship that far into outer space, without help from aliens of course.

Above: Legitimate example of space travel.

Take all the hardships of traveling to another planet and multiply those by five bazillion – that is the problem with interstellar exploration. Since these stars are so far away, a ship has to have enough energy to make it and also survive the ridiculous environment outside our solar system like damaging vacuums, weightlessness, micrometeoroids (try saying that five times fast) and our old friend radiation.

The distance alone is an enormous task to overcome. Right now the Voyager 1 is on its way to the nearest star Proxima Centauri and it won’t be there for another 72,000 years. A couple theories, explained below, have a chance of taking a ship to the nearest star within a century. The current goal by scientists is to obtain ship velocity of 10% of light speed and with that power a craft can make it to the Proxima star within 40 years.

Nuclear Pulse Propulsion

As it turns out, nuclear explosions are more useful than ending world wars, they can propel a ship to nearly 10% of light speed. Small nuclear bombs explode and with the help of a pusher plate, drive the ship forward into space.

Why This Works Well: Nuclear explosions are nothing new for us and every day we are progressing in using them more efficiently, just ask Iran. A nuclear powered ship would have extraordinary specific impulse, space travel lingo for fuel efficiency, and moderate costs for construction.

It’s safe to say Iran just wants to travel to Mars like the rest of us.

Why This Doesn’t Work Well: We aren’t good enough at math yet. Most of the derivatives are still out of our league and current renditions of a nuclear powered ship, Project Orion, were drastically under performing in cruise velocities. Only time will tell if mankind is able to apply the theory into a perfect practice.

Read more about Nuclear Pulse Propulsion: http://www.islandone.org/Propulsion/ProjectOrion.html

Fusion Rockets

The use of fusion reactors can potentially power a ship to 10% of light speed. The ship will be equipped with multiple fusion reactors that burn deuterium, tritium, and other elements you know nothing about.

Why This Works Well: Nuclear fusion for this application is more efficient than nuclear fission and scientists believe to be able to manufacturer such a ship in the next few decades. It helps that we already have a working knowledge of fusion reactors.

Why This Doesn’t Work Well: Fuel for this stuff is heavy. Really heavy. The balance of weight versus power is one thing that may keep this theory on the table. The plausibility of long term travel weakens when you take into consideration the enormous weight of the nuclear infrastructure that is required.

Read more on Fusion Rockets: http://science.howstuffworks.com/fusion-propulsion.htm

Even the Chinese can’t make it any smaller.

Light Sails

This theory is arguably the best, but it is also the most confusing. Imagine taking charged particles from the Sun and using them to propel a ship into space. The ship uses magnetic sails to deflect the particles found in the solar wind from the Sun and create forward thrust. At the meantime, the ship’s engine is being powered by a laser back on Earth.

Why This Works Well: There is no reaction mass on the ship, so the only weight onboard is the cargo. This theory also uses known physics and proven technology. It is also cheaper than nuclear pulse propulsion.

Why This Doesn’t Work Well: The laser beam sent out to power the ship loses its efficiency the further out you go. Charged particles jostle each other and eventually the beam weakens, meaning the ship will lose its juice. Also, using this propulsion method exposes the crew members to 1,000g’s, pressure only one animal on earth can survive – the salamander. And most importantly, once the ship reaches its destination there is no way back because you need another laser to power you home.

Read more on Solar and Light Sails: http://www.solarsails.info

Future astronaut.

Difficulties of Sending Man to the Stars

Unfortunately it even more perplexing to send a man to the nearest star than Mars. Even if we nailed the technology to reach a star within half a century, it takes the same amount to get back home. Barring major advances in life expectancy, a crew would be all dead long before they made it back home.

But say we could live longer. Even that won’t help us right now because most of these theories lack the foresight or resources for a return trip. So right now the best interstellar travel theories are suicide leaps of faith.

“Cool” Ways to Stay Alive on These Long Trips: But what if a person did want to travel on a one way mission and not be dead when they arrived? The most common theory is cryonic preservation like you see in the movies. We are eons away from perfecting that science, so you may want to investigate the idea of shipping out frozen embryos and raising them with educated, friendly robots when they arrive at the destination. Obviously this idea lends it self best to colonizing another planet, but it is pretty ridiculous in and of itself.

Johnny 5…arguably funny robot, definitely bad parent.