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Image: Rocket
David A. Hardy  /  www.astroart.org
Unpiloted Daedalus star probe design was the output from a British Interplanetary Society study completed in the late 1970s.
By
Special to MSNBC

Marc G. Millis of NASA’s Glenn Research Center manages the Breakthrough Propulsion Physics Program.

Have you ever wondered when we’ll be able to travel to distant stars as easily as in science fiction? Believe it or not, scientists are seriously looking at concepts such as wormholes, space-time distortions and space drives.

But transforming these flights of fancy into reality will require scientific breakthroughs on three fronts: propulsion, speed and energy. Although we do not yet know if these breakthroughs can be achieved, we at least know how to begin making the progress to find out.

The real question is not whether interstellar travel can be done, but when it will be fast and easy enough to send the first mission.

In a sense, interstellar travel is already happening. The Pioneer 10 and Voyager 1 spacecraft, both launched in the 1970s, have traveled more than 6.5 billion miles from

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Earth and are on their way out of our solar system. But at the speed they’re going, it would take tens of thousands of years for a probe to reach our nearest neighboring star. That’s longer than all of recorded human history. Further technological developments can significantly reduce this time, but further scientific breakthroughs are needed before interstellar travel becomes practical.

The propellant problem
The first challenge is propulsion, specifically propellant mass. Unlike aircraft that can use the air as their reaction mass, rockets need to bring along their own reaction mass, propellant, with them. By blasting propellant out the back, rockets push spacecraft. The problem is quantity. Propellant needs rise exponentially with increases in payload, destinations, or speed.

For interstellar voyages the numbers get, well, astronomical. For example, to send a payload the size of a school bus to the nearest star within 900 years, you’d need ... well, more mass than there is in the entire universe. This assumes that you’re using chemical engines like those on the space shuttle. With nuclear fission rockets the situation gets better, but not by much — the propellant required would fill a billion supertankers.

Although the situation gets much better with ion propulsion or antimatter concepts, the numbers get astronomical again if you want to get there in less time than 900 years, or if you actually want to stop when you reach your destination.

Ideally, we would want to use a space drive that doesn’t need any propellant. A few researchers have begun studying how to achieve this, searching for something else in space to push against, perhaps even by pushing against the very structure of space-time itself, or by finding a way to modify gravitational or inertial forces.

The need for speed
The next and more obvious challenge is speed. Our nearest neighboring star is about 26 trillion miles away. That’s more than four years away at the speed of light, and light-speed is about 17,000 times faster than the Voyager spacecraft.

Although the search for a non-propellant space drive would dramatically improve this speed situation, some researchers have even contemplated circumventing the light speed limit for interstellar travel.

Break the light speed limit? No. The trick is to circumvent the light speed limit by distorting the fabric of space-time itself to create “wormholes,” which are shortcuts in space-time, or by using “warp drives,” which are moving segments of space-time.

The warp drive idea is something like a moving sidewalk, similar to what you find at many airports. By expanding space-time behind the starship and contracting it in front, a segment of space-time moves and carries the ship with it. The starship itself still moves slower than light within its space-time, but when you add the “moving sidewalk” effect; the apparent motion exceeds the speed of light. There are numerous difficulties with these concepts, however.

Looking for energy
The last challenge is energy. Even if we had a space drive that could convert energy directly into motion, it would still require a lot of energy. Sending a shuttle-sized vehicle on a 50-year, one-way trip to the nearest star would require 70 quintillion joules of energy — the equivalent of running the space shuttle’s engines continuously for that same 50 years. This amount is roughly the same as the output of a nuclear power plant.

For our warp drives and wormholes, the energy situation is much, much worse. To create a 3-foot-wide wormhole, you would need to convert something with the mass of Jupiter into negative energy. To overcome these difficulties, a few breakthroughs in energy production would help.

To find out if we can actually begin making progress toward these grand ambitions, NASA established the Breakthrough Propulsion Physics Program in 1996. The program has supported conference sessions, workshops and Internet sites to foster collaborations and to identify affordable research.

The next step is to sponsor a few, small research tasks. After two years of supported research, we’ll ask if the progress gained is worth sustaining the program. If the answer is “yes,” increased support will be sought. If the answer is “no,” then the program will be put on hold until further significant developments emerge from general science.

Why bother with these seemingly impossible goals? Well, progress is not made by conceding defeat. History is replete with conquered impossibilities — flying machines, moon landings, and tapping the power of the atom, to name but a few. It took four decades to go from the first liquid rocket to the first landing on the moon, and three decades to go from the confirmation of radioactive decay to the first nuclear reactor.

Physics continues to uncover new possibilities — possibilities that might someday solve the challenges of interstellar flight. Even if we don’t achieve a propulsion breakthrough during my lifetime or my children’s lifetime, and even if such a breakthrough is impossible — I am firmly convinced that we as a society will gain far more from trying than if we didn’t.

© 2013 MSNBC Interactive.  Reprints

Explainer: 10 pieces of Star Trek tech

  • Paramount Pictures

    The latest reboot of the Star Trek franchise follows the story of a young James Kirk on his way to becoming captain of the Starship Enterprise. The movie gives Trekkies a fresh dose of fictional high-tech wizardry. But is any of this possible in the real world? Click the "Next" arrow above to see how 10 pieces of Trek tech, from teleportation to warp drive, are faring here on Earth.

    -- By John Roach, MSNBC contributor

  • Teleportation: a work in progress

    Ray Strange  /  AFP via Getty Images file

    "Beam me up, Scotty!" Oh, how easy travel would be if the technology existed to disintegrate our bodies in one place and nearly instantaneously make them reappear at our destination. Unfortunately, that kind of teleportation remains firmly fixed in the realm of Star Trek fiction. However, scientists are meeting with some success as they try to teleport messages encoded in beams of light across table-length distances, such as this experiment from 2002. More recent advances include teleporting information from one trapped atom to another.

  • Tricorder-like device scans for cancer

    Boris Rubinsky et al.

    Star Trek fans know tricorders as familiar handheld devices that scan unfamiliar planets (and organisms). Real-world citizens, too, are becoming familiar with a host of futuristic gizmos that do everything from reading a critter's DNA to scanning patients for cancerous tumors, as shown in this side-by-side comparison of a fictional tricorder (left) and a medical scan of simulated breast tumor displayed on a cell phone.

  • Deflector shield envisioned for Mars missions

    Ruth Bamford And John Bradford

    A so-called deflector shield surrounds the Starship Enterprise, protecting the spacecraft and its crew from lethal doses of radiation. Lab experiments now suggest that a portable magnetic shield could protect real-life astronauts on a mission to Mars. The shield would force harmful particles to curve around the ship. The engineering details remain to be worked out, and for now, the shield protects only against particles from the solar wind. Gamma rays and X-rays would remain a threat. An artistic depiction of the technology deployed on the Enterprise is shown here.

  • U.S. Air Force develops PHaSER

    Image: PHaSER
    U.s. Air Force

    The weapon of choice for Trekkies is the phaser, a device that directs an adjustable beam of energy at its target. The phaser is capable of a range of effects, from a momentary stun to instant obliteration. The U.S. Air Force has developed its own prototype device with the Star Trek moniker PHaSER (Personal Halting and Stimulation Response). The hefty gunlike device was originally developed to blind an attacker temporarily. A second laser has since been added capable of heating up skin.

  • Holodeck tech emerging

    Tom Uhlman  /  AP

    Starfleet members seeking knowledge or fun can step into holodecks to experience an interactive virtual reality eerily close to life itself. Similar technologies are beginning to emerge in the real world, including this 3-D lab at Wright State University in Ohio, where businesses can use the technology to speed up and improve the designs of products. An energy company is using it to enhance their search for oil. Other firms are embracing advances in video and audio technology to make telepresence, or videoconferencing, more realistic. The most lifelike experiences, however, remain in science fiction.

  • Tractor beam manipulates cells on a chip

    MIT

    In Star Trek, tractor beams are used by starships and space stations to control the movement of objects usually to pull them in closer, tow them along, or push them away. Researchers at the Massachusetts Institute of Technology have used a tractor beam of light to pick up, hold and move around individual cells on the surface of a microchip. To demonstrate the technology, the researchers moved around and held in place 16 E. coli cells to spell out MIT, as shown in this image.

  • Cell phones are pretty good communicators

    Apple Inc. via AP

    Trek-style communicators are those little devices, handheld or sometimes worn as a badge, that allow Starfleet members to speak to others in different parts of the ship or different parts of a planet. Modern-day cell phones, including the iPhone shown here, just might wow even the likes of Captain Kirk.

  • Universal translators making strides

    iTRAVL

    In Star Trek, language is seldom a barrier thanks to universal translators, devices that allow people of different tongues to converse. Communication among cultures in the real world remains a challenge, but basic words and phrases are no longer stumbling blocks, thanks to gadgets such as the translator from iTRAVL shown here. Speak into the device, and it will translate the word or phrase and speak it aloud.

  • Cloaking devices coming out of hiding

    Naomi Halas, Rice University |

    Cloaking devices are rampant in science fiction, from Star Trek to Harry Potter but they are no longer confined to the imagination. Real-world scientists are creating new materials that manipulate wavelengths of light in ways that can hide objects from detection. This graphic shows the basic design of a 3-D metamaterial lined with nanocups that redirect the flow of light that hits it, making the object invisible.

  • Warp drive? Don't bet on it

    Les Bossinas  /  NASA

    The Enterprise can travel faster than light via something called warp drive — essentially, a device that warps the space-time continuum around a starship. Many scientists have batted around ideas about how to achieve blistering speeds in real life, but most experts have concluded that, at least for now, warping the fabric of space is beyond human understanding of the laws of physics. Among the difficulties is harnessing the energy required to kick-start the propulsion.

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