Thrown off course by relativity

Tom James @ 24-08-2009

Cosmos1-2006-2A preview of space-flight issues of the future: how do you account for the effects of relativity when travelling long distances? A solar sail launched from close to the Sun would have to account for relativistic effects when navigating to the edges of the solar system:

And even though those effects are relatively minor to start with, they have a significant effect over long distances.

The calculations carried out by Kezerashvili and Vazquez-Poritz show that the effects of general relativity could push a solar sail off course by as much as a million kilometers by the time it reaches the Oort Cloud

The promise of solar sails as a propulsion mechanism is impressive:

By one calculation, a solar sail with a radius of about a kilometer and a mass of 300 kg (including 150 kg of payload) would have a peak acceleration of about 0.6 g if released on a parabolic trajectory about 0.1 astronomical unit (AU) from the sun (where the radiation pressure is higher).

That kind of acceleration would take it beyond the Kuiper belt to the heliopause, the boundary between the solar system and interstellar space (and a distance of 200 AU), in only 2.5 years.

In 30 years, a solar sail could travel 2,500 AU, far enough to explore the Oort Cloud.

Of course we need to actually build one of these things first.

[from Technology Review, via Technovelgy][image from Wikimedia]

Bussard ramjet revisited

Tom James @ 10-06-2009

star_and_barsAn interesting discussion of Bussard ramjet interesteller propulsion technology here at Centauri Dreams and Adam Crowl:

Robert Bussard put the interstellar ramjet into the public eye back in 1960 in a paper proposing that a starship moving fast enough would be able to use the hydrogen between the stars as a source of fuel, enabling a constant acceleration at one g.

One of the key problems with Bussard ramjets is the speed of the fusion reactions:

Physicist Daniel Whitmire tackled this problem in a 1975 paper that proposed using hydrogen for fuel but exploiting a catalytic nuclear reaction chain instead of straight proton burning.

It’s all interesting stuff, but even if the Bussard ramjet is unfeasible as a propulsion system it may be feasible as a brake for interstellar spacecraft.

[image from kevindooley on flickr]

Biotech to the stars

Tom James @ 28-05-2009

dendritesCentauri Dreams discusses a DNA-based self-replicating interstellar probe:

Think of a probe that gets around the payload mass problem by using molecular processes to create cameras and imaging systems not by mechanical nanotech but by inherently biological methods.

A Von Neumann self-replicating probe comes to mind, but we may not have to go to that level in our earliest iterations. The biggest challenge to our interstellar ambitions is propulsion, with the need to push a payload sufficient to conduct a science mission to speeds up to an appreciable percentage of lightspeed. The more we reduce payload size, the more feasible some missions become

This is similar to Robert L. Forward‘s starwisp concept (popularised by Charlie Stross in Accelerando).

I suspect that if and when we do get round to interstellar exploration it will involve sending small-mass packages that are capable of bootstrapping themselves to a broadcast/exploration mode using local materials on arrival in the target system.

It remains to be seen what kind of space-based molecular replicating systems become viable. Will we be able to create space-hardened bioware, or good ol’ fashioned machine phase fullerene nanotech?

[image from neurollero on flickr]

Fuse me to the Moon… (with bombzzz!!1!1)

Tom James @ 02-02-2009

mandelbrot_fusionPhysicist Friedwardt Winterberg has a new paper here on a possible fusion-powered spacecraft, with shades of Project Orion and Project Daedalus:

Large scale manned space flight within the solar system is still confronted with the solution of two problems: 1. A propulsion system to transport large payloads with short transit times between different planetary orbits. 2. A cost effective lifting of large payloads into earth orbit.

For the solution of the first problem a deuterium fusion bomb propulsion system is proposed where a thermonuclear detonation wave is ignited in a small cylindrical assembly of deuterium with a gigavolt-multimegampere proton beam, drawn from the magnetically insulated spacecraft acting in the ultrahigh vacuum of space as a gigavolt capacitor.

For the solution of the second problem, the ignition is done by argon ion lasers driven by high explosives, with the lasers destroyed in the fusion explosion and becoming part of the exhaust.

The key point is that it’s designed without $MAGIC_FAIRY_DUST technology and is intended to be feasible from a purely engineering standpoint.

[via Slashdot][image from SantaRosa OLD SKOOL on flickr]

DVD gift ideas for science-minded kids

Tom Marcinko @ 29-11-2008

My son, age eight, has always been interested in animals, extinct or otherwise. But he’s played to death the three-DVD documentary series The Future Is Wild, which depicts the evolution of life on Earth millions of years into the future. The CGI animation is pretty good; the extrapolated life forms in the post-human world are mind-bending.

My son doesn’t seem frightened or depressed by the depiction of a universe without human intelligence or galactic empires, which is more than I can say for his dad. You don’t have to be a kid to get into this. And if you’re even considering writing an sf story about nonhuman aliens, please see it.

There’s an animated TV adventure series on Discovery Kids, but my son and I agree that it’s not as good as the original.

Just as good, and getting almost as much screen time in my house, is Alien Planet, exploring via space probe the planet Darwin IV, where evolution produced creatures like nothing on Earth.

I hope they go over as well in your home as they have in mine.

[Bladderhorn from Alien Planet]

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