February 24, 2013 – A starship without an engine: It may seem a fantastical notion, but hardly more so than the idea of building a starship of any kind. The space program needs a dream. If there are no dreamers, we’ll never get anywhere. However, this dream may be closer to reality than many people think.
First, find an asteroid in an elliptical orbit that passes close to the Sun. Second, put a starship in orbit around the asteroid. If the asteroid could be captured into a new orbit that clings close to the Sun, the starship would be flung on an interstellar trajectory, perhaps up to a tenth of the speed of light. The chaotic dynamics of those two allow all the energy of one to be transferred to the other. It’s a unique type of gravity assist.
Still, the sheer distances are daunting. The problem of the stars is larger than most people realize. Think of it this way. If Earth were in Orlando and the closest star system, Alpha Centauri, were in Los Angeles, then NASA’s two Voyager spacecraft, the most distant manmade objects, have traveled just one mile.
Another way of looking at the challenge is that in 10,000 years, the speed of humans has jumped by a factor of about 10,000, from a stroll (2.6 m.p.h.) to the Apollo astronauts’ return from the Moon (26,000 m.p.h.). Reaching the nearest stars in reasonable time — decades, not centuries — would require a velocity jump of another factor of 10,000.
The first steps, however, are easy to imagine. Even in the 1950s, rocket scientists realized that the current engines — burning kerosene or hydrogen and spewing flames out the nozzle — are the rocket equivalent of gas guzzlers. They designed nuclear engines that use reactors to heat liquid hydrogen into a fast-moving stream of gas. NASA has such engines ready for a manned mission to Mars, if it can acquire the funding.
More advanced nuclear engines would use reactors to generate electric fields that accelerated charged ions for the thrust. Then fusion engines — producing energy through the combining of hydrogen atoms — would finally be powerful enough for interstellar travel.
The Starship (pictured above) dwarfs the Saturn 5, the rocket that took astronauts to the Moon. However, it’s no bigger than a Nimitz aircraft carrier. We have the ability to create big things. We just don’t have the ability to launch big things. However, it could be launched in segments and reassembled in space.
There is another approach, harking back to the era of sailing ships. Giant sails on the starship could billow from photons beamed from Earth by lasers or giant antennae. Here’s a case where we know the physics, and the engineering is doable.
“Vision without execution is daydreaming,” paraphrasing a Japanese proverb. It seems unlikely that asteroid flinging would be sufficient by itself. Still, it could prove a useful and cost-effective supplement for other propulsions systems.
Starship engines will change NASA. The first goal will be colonizing the solar system, starting with Mars. From there, it’s on to the stars!
The Master of Disaster