Will nuclear-powered spaceships take us to the stars? (BBC)

[eppur_se_muova]

by Richard Hollingham

In the 1950s, rocket scientists dreamed of atomic-powered spaceships. Now these far-fetched designs might help a new generation explore the cosmos.

Project Orion has to be the most audacious, dangerous and downright absurd space programme ever funded by the US taxpayer. This 1950s design involved exploding nuclear bombs behind a spacecraft the size of the Empire State Building to propel it through space. The Orion’s engine would generate enormous amounts of energy – and with it lethal doses of radiation.

Plans suggested the spacecraft could take off from Earth and travel to Mars and back in just three months. The quickest flight using conventional rockets and the right planetary alignment is 18 months.

There were obvious challenges – from irradiating the crew and the launch site, to the disruption caused by the electromagnetic pulse, plus the dangers of a catastrophic nuclear accident taking out a sizable portion of the US. But the plan was, nevertheless, given serious consideration. Project Orion was conceived when atmospheric nuclear tests were commonplace and the power of the atom promised us all a bright new tomorrow. Or oblivion. Life was simpler then.
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more: http://www.bbc.com/future/story/20140423-return-of-the-nuclear-spaceship

[FiveGoodMen]

1. Only if Einstein was wrong about the speed of light

[Silent3]

3. 3 months to Mars is fast by the standards of our limited tech, but compared to the speed of light...

...that's a snail's pace. No way the speed of light limit is being challenged by anything in this article.

Is there something else that you meant by your comment that I'm missing?

[FiveGoodMen]

4. Nuclear-powered spaceships won't take us to the stars because they're too far away

If the trip's too long for anyone to take it doesn't matter if the fuel holds out.

[Silent3]

5. In *your* own lifetime, you can get practically anywhere while remaining under the speed of light...

...so long as the acceleration doesn't kill you, simply by getting very close to the speed of light. Whether mere nuclear power as we currently know it can help us attain this kind of close-to-light-speed travel is another matter, but basic relativity doesn't rule out arbitrarily close to instantaneous travel within the frame of reference of the traveler.

After the daunting technological problems are solved, the biggest remaining problem is more social than physical. If you want to travel somewhere that's 100 light years from here, you can get there and back arbitrarily fast -- 50 years, 10 years, one year even if the acceleration was tolerable -- but when you get back home, at least 200 years will have passed for everyone you left behind on Earth. Unless medical technology had vastly improved along with space travel technology, everyone you ever knew who didn't travel with you would be dead when you got back home.

At any rate, the nearest star is about 4 light years away. We wouldn't even have to push the extremes of relativistic effects to get there and back within both the lifetimes of the travelers and the lifetimes of the people waiting for them back home on Earth.

[qazplm]

6. huh?

The nearest star is only 4 LYs away.

If you can go even at just 10 percent of the speed of light, you get there well within a human lifetime, particularly if you can figure out how to put them in suspended animation for all or most or even part of that trip.

Nuclear rockets or some of the other propulsion ideas can easily reach that speed and more.

[bananas]

7. At 1g acceleration, you can cross the galaxy in 12 years.

Lorentz contraction brings the stars to you, so you don't have to go so far!

http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

The Relativistic Rocket

... the galaxy is about 100,000 light years across ...

... use the relativistic effects of time dilation and length contraction to cover large distances within a reasonable time span for those aboard a space ship ...

... If a rocket accelerates at 1g (9.81 m/s2) the crew will experience the equivalent of a gravitational field with the same strength as that on Earth. ...

<snip the calculations>

... So in theory you can travel across the galaxy in just 12 years of your own time. ...

[FogerRox]

8. Busssards QED Polywell powered design Mars in 38 days, Titan in 76.

Using proton Boron 11 fuel.

Using Lithium fuel 550 AU in 5 years. Bussard thought placing a telescope at 550 AU to use the sun as a grav lens would be worth the time to do the math.

[sakabatou]

2. It's possible

A fusion-ion engine could be feasible as a generation ship.