Science fiction has offered us all sorts of visions of interstellar spacecraft, from avian-inspired Klingon birds of prey to hulking masses such as the Borg cube. In general, sci-fi leans toward sleek designs with lines borrowed from planes or cars, since those are the kinds of looks we?ve been conditioned to think of as "fast." But if there?s no air in space, why make things aerodynamic? Does it matter what a spacecraft looks like?
Yes, it turns out, and it depends upon what kind of space travel you?re looking to undertake. The reality of starship design is more complex than anything Hollywood has dreamed up and implanted in our collective unconsciousness.
While a manned interstellar mission isn?t exactly on NASA?s upcoming schedule, researchers haven?t abandoned the topic to science fiction. In fact, the 100 Year Starship initiative?which began as a DARPA-funded contest to lay the foundations for a flight across the stars, gathering physicists, entrepreneurs, and anyone seriously interested in long-distance space travel?just finished its annual symposium this past weekend.
One of the participants of the 100 Year Starship project is Marc G. Millis, founder of the Tau Zero Foundation. The foundation has proposed candidate technologies and designs, including the Icarus unmanned fusion-powered probe, which would accelerate (theoretically, of course) to one-tenth or one-fifth the speed of light. Icarus, as it?s currently envisioned, isn?t the sleekest space ride. The skyscraper-size behemoth is comprised almost entirely of rows and clusters of spherical fuel tanks. But according to Millis, Icarus isn?t a definitive, catch-all prediction of what an interstellar craft might look like. It?s simply the design that might make sense to build first.
We asked Millis, who once led NASA?s Breakthrough Propulsion Physics Project, to take us through the basics of starship design.
Starships Aren?t Spaceplanes
One look at the Icarus design?or its predecessor, the Daedalus?and it?s clear what starships don?t need: wings. The only real-world spacecraft that bother with wings are ones designed to make regular landings on runways, such as the retired Space Shuttle, the upcoming Lynx (a suborbital two-seater from XCOR) or the Dream Chaser, an in-development orbital craft from Sierra Nevada. And wings aren?t even required for landings. Like the Russian Soyuz capsule, SpaceX?s Dragon currently splashes down in the ocean (though SpaceX plans to move toward rocket-powered launchpad landings).
In both the near and far-term future, experts such as Millis imagine interstellar vessels won?t spend much of their time in an atmosphere. Perhaps the small ships that carry people from surface to starship will remain winged, but truly interstellar vehicles can scrap aerodynamics and all of the design principles that are beholden to reducing wind resistance. A starship doesn?t need to be sleek or have a pointy nose?even the stocky Battlestar Galactica is pointlessly aircraft-shaped. If anything, the equivalent Cylon ships in the rebooted TV series are more rational interstellar travelers, with their spindly arms and flagrant disregard for the entire air-centric history of aerospace.
Surviving Sublight
Predicting what the first unmanned starships might look like is relatively simple. In the case of Icarus, for example, the entire structure is devoted to propulsion. It?s a colossal rocket, albeit a weird fusion-powered one.
Millis says the first person-carrying starships, however, will be dominated by the technologies that keep those passengers alive. Consider gravity, a necessity on long-distance spaceflights. In prolonged zero-g, the human body erodes, losing bone and muscle density. "With the physics we know, you create gravity with a giant centrifuge, a rotating cabin, basically," Millis says. The spinning disc on the Jupiter-bound Discovery One in 2001: A Space Odyssey illustrated this concept well, but Millis says that to better simulate Earth gravity, the real thing would actually have to be much larger. The smaller the centrifuge, the less consistent the centrifugal force is across a crew member?s body?the head, in other words, will feel lighter than the feet. Aside from being disoriented by chronic light-headedness, if the goal is to re-create the way blood circulates under the influence of gravity, consistency is key.
Discovery One, from 2001: A Space Odyssey
Of course, mankind can?t survive on gravity alone. A starship designed to keep its occupants alive for years, decades, or even centuries, would require systems unheard of in current spacecraft. Sections for growing crops or livestock, for example, could dwarf more traditional compartments. And spacious recreational facilities, with enough room and resources to support vast interior parks, might be crucial for fighting off the existential crisis of spending an entire lifetime crammed inside a spacecraft. What might seem laughable today, and a colossal waste of mass, could become the most defining feature of a vessel filled not with astronauts, but a wider swath of humanity?including, quite possibly, children born en route. Suddenly, a giant, rotating playground bisecting your vessel isn?t such a bad idea.
The look of your starship depends a lot on your method of transportation, too, and all of the proposed methods of interstellar propulsion carry their own problems. Anything that requires the ship to have a massive surface area?such as using a sail propelled by the sun?s photons or onboard lasers?would have to contend with intergalactic dust. There isn?t much material out there in space, but even tiny particles are a hazard to vessels moving at some significant fraction of the speed of light. Those dust particles could cut through a solar sail; perhaps the crew would have to replace or repair the sail when it comes too perforated.
Ikaros, Japan's solar sail project. Credit: JAXA
Perforated sails might be replaceable, but all fast-moving starships will need to worry about dust. Forget the layouts of Firefly?s Serenity or the more recent eponymous vessel from Prometheus, with their swooping birdlike profiles and aircraft-style front-mounted cockpits. The risk of dust impacts probably means turning crew compartments into bunkers, and sticking people and any essential systems behind redundant layers of physical shielding. The result would seem ugly by sci-fi standards closer to the Icarus from 2007?s Sunshine (not to be confused with the work-in-progress concept), with its solar shield making it look more like a giant umbrella than a bird of prey.
gwen stefani overeem laron landry mary j blige burger king islands joe flacco 2013 nissan altima
No comments:
Post a Comment