Thanks again Anthony, Damn Interesting indeed!

First time this material has been publically available they say.

Interesting stuff…

Floj says:
I wonder, would a hydrogen bomb disintegrate the metal shielding? I know it’s a fusion bomb; it might get too hot.

No; any given blast-plasma is not in contact with the pusher plate for long enough.

middlenamefrank says:
It’s a chasing game of diminishing returns which pretty much precludes, for instance, a chemical rocket ever taking a manned mission to Mars

If you mean a constant-acceleration ship, sure; the fuel requirement would indeed be prohibitive. The usual style of mission, though—accelerate, coast, decelerate—would be quite feasible. See, for instance, Robert Zubrin’s “Mars Direct” proposal.

davidw987 says:
You would need an awful lot of fissionable material to launch one of these suckers.

Not as much as you might think. Nuclear reactions are about 1,000,000 times as powerful as chemical reactions. It takes less than 20 lb. of plutonium to make a 4 kT nuke, such as was mentioned in the article, and we can produce almost arbitrarily large amounts of Pu via breeder reactors.

PresMatt says:
If one of these things blows up with 70 nukes on board, how much of the planet goes with it?

A negligible amount, even if all 70 bombs went off on a planetary surface. Hurricanes and earthquakes release much more energy than that, and even they don’t tear up the crust to a notable degree. (Note that I’m talking about planetary-scale effects, not human-scale, here.)

It’s a novel idea, and I’d love to see it happen if it weren’t for that nasty radiation thing. Maybe we’ll figure cold fission out someday and be able to use it instead.

Do you mean “cold fusion” there? If it were to become workable, it could perhaps be used as the energy source for, say, an ion engine or a laser drive, but not for a high-impulse drive such as a chemical or nuclear-pulse rocket. Even a nuclear thermal rocket wouldn’t be a suitable application, I believe, because of the relatively low energy density of the putative cold-fusion process.

to-be-betrayed says:
hmm…I suppose if you found fissionable material with a short half-life, e.g. a day or two maximum, it *might* work…

By this, do you mean a fission reaction whose product nuclides have short half-lives, so as to minimize the fallout problem? Or do you mean “use short-lived stuff as the propellant”? (Which, as was said above, would be very impractical.)

PresMatt says:
It’s not so much planets I was concerned about, but asteroid belts (Kuiper Belt for example) and/or smaller bodies in close proximity (moons for example). If 50 nukes blew all at once near an asteroid belt, there’s no telling how many new Near Earth Objects COULD be created…

Asteroid belts are not nearly as dense as many people imagine them to be. A field of asteroids such as was raced through by Han Solo in Star Wars: The Empire Strikes Back would quickly collapse into one large lump. Setting off a cluster of nukes in a real asteroid belt might not affect any of them; at best, just a few.

And if 50 nukes blew close to the moon, say as it was slingshotting via gravity, there’s no telling how it could affect Earth.

50 nukes detonating in a close lunar orbit would briefly heat a small part of the surface. Even detonating them on the surface would only make a new crater and would cause a few moonquakes, but the change of Luna’s orbit (and the consequent change in terrestrial tides) would be essentially zero.

exsomnis says:
Of all the novel ways to propel one’s self into space, I think nuclear blast propulsion is by far the most ill-advised and narcissistic method ever. Even reading about it in sci-fi wasn’t enough to suspend belief.

Narcissistic, exsomnis? Please explain.
And—if you couldn’t suspend disbelief by reading fiction, could you do it by reading the physicists’ reports from actual calculation and observation?

1c3d0g says:
I recall NASA launched a Pluto-bound rocket this year which had a plutonium-powered engine. So, even though it may not use the same technique. successful remnants of the projects continue to be pursued to this day.

Indeed; the RTGs (Radioisotope Thermal Generators) have been successfully used for many years now. (Plutonium, even in combined form such as the oxide that is used here, is active enough to keep itself rather warm if properly insulated. This heat can then provide electricity via thermocouples.)

Shandooga says:
How disturbing that such obviously intelligent (in one sense of the word) people could be seduced by the ridiculous fantasy of space travel.

Space travel has not been a fantasy since 4 October 1957 (Sputnik I).

Why would anyone would assume that they are *bound* to meet with success just because they spent a WHOLE LOT OF MONEY on a space ship?

Such assumptions are based on prolonged, careful investigation, which must take place before anyone will be willing to spend money on the project. Be careful with your assumptions, OK?

With all the knowledge we (should) have of what makes planet Earth so very special you’d have to be a fool to the 3rd power to expect to find anything even remotely similar within whatever paltry distance a human lifespan could travel.

We don’t blindly expect to find “Class M” (Roddenberry’s notation) planets nearby, Shandooga. We observe and measure, and from the information so gleaned we estimate the chances. Then we do further tests to refine the estimates. Astrophysicists and planetologists do not sit around idly!

Earth is big enough for all of its inhabitants (whether or not you like most of them) and there’s NOWHERE ELSE TO GO! Just accept it.

Earth’s resources—the economically useful ones, that is—are small compared to the off-planet resources. More than 90% of the accessible energy and materials in the Solar System are not on Earth.
As far as “nowhere else to go”—nonsense! Space provides an enormous livable volume, even if we never terraform a planet—which we’ll also be able to do, eventually.

I refuse to “just accept it”. As I’ve seen it put: “The meek shall inherit the Earth. The rest of us will go on to the stars.”

etonalife says:
As a species we have an utmost obligation to survive. By spreading out and diversifying ourselves will only increase our chances of success, such as we have done for the past thousands of years. We also have an obligation to understand space simply because of the destruction it can so easily wage on our little ball here.

Indeed! “Earth is too fragile a basket for humanity to put all its eggs in.”—Robert A. Heinlein

Shandooga says:
Had so many people not been misled by the MATHEMATICALLY IMPOSSIBLE theory of evolution

A process that is easily observable in the lab (or in the hospital) is not “mathematically impossible”. Brush up on your mathematics, especially probability and statistics.

Life doesn’t just “spring up” from non-living matter

And you know this how? (Consider the Urey-Miller experiments, for instance. They did not produce life, no, but various essential precursor molecules were found to be easy to produce from entirely non-living (and non-biogenic) molecules.)

True we have not explored the *entire* universe

Or even a tiny, tiny fraction thereof.

The consideration of what we *do* know about these few planets is enough to establish that life is *not* randomly distributed throughout the universe and, therefore, *cannot* be a product of a series of random events–however long the series.

Eh? A random distribution would ensure that there would be spots with plentiful life, and spots with no life. So far, we’ve seen one life spot and many non-life spots…and tantalizing hints of other possible life-spots. We need to do more research and less pontification.

Shandooga said: “Anthony Kendall said: ‘… it is technically possible to do so; we just need sufficient motivation.’

“Again, technology and motivation will not, of themselves, produce any viable planets for humans to also ruin.”

Wrong again; see here: http://en.wikipedia.org/wiki/Terraforming for some basic information on terraforming.

Vivendi says:
While I’m sure that we could build something like this, I don’t see how it’s better than our current methods… In terms of energy, I’m pretty sure our current methods are more efficient than this.

A nuclear-pulse drive would be much more efficient than a chemical rocket, Vivendi. Consider the propellant-to-payload ratios where one type of propellant is 1,000,000 times as energy-dense as the other….

Phill says:
Don’t correct me if I’m wrong =P, but according to the String Theory, there should be alien life forms.

Sorry, gonna correct you there. ;-) String Theory deals with cosmogony (the origin of the universe), not specifically with biology (or even abiogenesis).

Gary Goldfinch says:
Ok, I’m no scientist :) but can someone explain this:

So… there’s a lot of solar radiation out there? Wouldn’t the whole craft need a meter-thick (or more) shield to protect it from this radiation then if it’s so intense?

The key is: it’s not so intense. SparkyTWP was referring to the total amount of energy received by Earth, which is spread out over one-half the globe at a time. The power density is only about 1 kW/m^2.

Ok, so this solar radiation would be a problem for space travel further from the Earth then I assume? I had a quick Google on the Magnetosphere and it doesn’t seem to stretch that far into space, how did the moonshots cope or did they have the appropriate shielding? Or did they time their missions so the moon was within the magnetosphere?

The missions were short enough that the astronauts’ expected cumulative dose (principally from cosmic radiation) would be acceptably small.

plowshare says:
I greatly enjoy books that talk about Orion and the more sophisticated Project Daedalus … they all seem to think that shielding the astronauts on 50-year journeys from radiation is nothing to worry about.
They all seem oblivious to the hydrogen-to-radiation problem, though.

I’ve read an article or two in Analog that addressed the problem. One solution was to have a block of tungsten mounted forward of the spaceship on a long mast; the tungsten, because of its great density, would cast a gamma-ray (and fast-particle) shadow that enveloped the ship.

http://www.space.com/businesstechnology/060927_techwed_orion.html