The world's first engineering study of an unmanned spaceship to explore one of the nearer stars was made by a technical group of the British Interplanetary Society between 1973-77. The target selected for the exercise was Barnard's Star, six light years distant from Earth. The team recognised that the work, based on the technology extrapolated to the beginning of the 21st Century, could represent only a first approximation to the solution of starflight.

The results showed it would be a formidable task requiring a massive craft that would dwarf the Saturn V moon rocket, the largest space vehicle yet flown by man. Daedalus, as currently conceived, would weigh some 54,000 tons, nearly 20 times the weight of the Saturn V, carrying nearly 500 tonnes of fully automated payload. Because of the enormous time lag involved in radio communications between the Earth and the ship, a semi-intelligent computer would have to control the entire ship and work out all actions necessary for the exploration phase of the mission.

The result was a two stage, nuclear fusion powered vehicle, unmanned and under autonomous operation due to the distances involved, accelerated to 16% of the speed of light, and armed with a variety of probes, sensors, robotic wardens and intelligent decision making computers. Although the journey could take as long as 40 years, a flyby at such speeds would be over in 70 hours.

Although the study was conducted during the 70's, it's still referred to today, even in NASA, as a baseline study. Any future mission to the stars probably won't look anything like Daedalus, but it gives a good idea of the complexity and scale of task, and the length of time it would take to get to even the closest stars.

No estimate of the cost of such an enterprise could be made, but it would be way beyond the capacity of an individual nation, and would probably need a period of world stability unlike any we have seen to date.

The Daily Galaxy with thanks to Bisbos.com http://www.bisbos.com/space_n_daedalus.html

Related articles

Image of the Day: NASA Sizes Up Pluto and Its Moon Charon

"A Universe of Planets" --A Short History of NASA's Search for Life Beyond Our Solar System

Yesterday's headlines reported that China's first space station Tiangong-1 was "in freefall," "hurtling towards Earth" and would "rain molten metal down onto Earth." The eight-ton Tiangong-1 serves as both a manned laboratory and an experimental testbed to demonstrate orbital rendezvous and docking capabilities. It was launched unmanned aboard a Long March rocket in September 2011.

According to astrophysicist Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics who works on Chandra X-Ray Observatory and comments on space launches and space activities, "it's too soon to tell whether Tiangong-1 is out of control. “In the history of the Space Age, uncontrolled re-entries have been common,” McDowell told  the Smithsonian. “And the chance that debris from any one of them hits somebody, it's one in thousands.”

The concerns over Tiangong-1's fate stem from two main sources: a press release the Chinese government published earlier this year and amateur astronomer observations.

This March, the Chinese Manned Space Engineering office (CMSE) announced that the space agency had terminated its data link with Tiangong-1 and would monitor its orbit as it descends into the Earth's atmosphere and burns up, the state-run news agency Xinhua reported at the time. But because the release didn't explicitly state that the CMSE was in control of Tiangong-1, some interpreted it as a sign that all was not well at mission control. In the meantime, amateur astronomers reported witnessing the space lab flicker as it orbited Earth, which some took as evidence that the station was spinning out of control.

Terminating the data link is not evidence of certain death, it just means that they are no longer using the module to collect data, says McDowell. They can also reestablish communication in the future, if necessary. McDowell speculates that CMSE is putting the module into hibernation until after its replacement, Tiangong-2, launches. But the Chinese government's reticence on the matter has further magnified all rumors.

SpaceLab, a craft ten times the size of Tiangong-1, reentered the atmosphere in 1979 and most of it went up in flames over western Australia. “Last year, a couple of farmers in Spain found these metal spheres in their fields,” McDowell says. “That was probably from a two-ton rocket stage left in orbit. It didn't even make the news at the time.”

Tiangong-1 is orbiting at about 215 miles above the ground—a relatively low altitude for an orbital satellite. That makes it easy to spot and could account for some of the worry among amateur astronomers who have noted changes in its appearance. But not only has Tiangong-1 been at this low altitude before, so has the International Space Station (ISS).

ISS and Tiangong-1 both have relatively low orbits, experiencing slight drag from the Earth's atmosphere that causes them to lose altitude over time, McDowell says. But the engineers for both crafts developed ways to ensure they don't fall too low in the sky. The ISS relies on its regular vistors to nudge it back into higher orbit. "They fire their engines and give it a boost," McDowell explains. But Tiangong-1 doesn't receive quite as many visitors and is much smaller, making it more effective for the CMSE to periodicly reposition the space lab using the onboard engine.

In the worst circumstances, the space station wouldn't enter the atmosphere until at least 2017. And reentry isn't something to be feared. “Most likely, some people will see a nice re-entry like a meteor overhead,” McDowell says. “If this were the day Tiangong-1 was re-entering, it still wouldn't be high on my list to worry about.”

The Daily Galaxy via Smithsonian.com

Image credit: With thanks to Adrian Mann/Bisbos.com