July 21, 2012
by Benjamin Solomon
Bruce Dorminey posted a link to his Forbes interview with Marc Millis titled “Leaving Earth: Former NASA Rocket Scientist On The Politics Of Going Interstellar” on the LinkedIn group Science & Technology Media Network.
http://www.forbes.com/sites/brucedorminey/2012/06/15/leaving-earth-former-nasa-rocket-scientist-on-the-politics-of-going-interstellar/
Andrew Skolnick gave an unbelievably good response to this article. I have reproduced it here with his permission. I could not have done it better. Remember we have to check the feasibility of proposed interstellar projects before we fund them. Thank you Andrew Skolnick.
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Andrew Skolnick • I’m tempted to call such starry-eyed dreamers “pi squarers,” but squaring pi is impossible and faster-than-light — and even human travel to the stars — is not. It’s just beyond doing — like constructing a building tall enough to take people and cargo up to low-earth orbit by elevators. Not impossible. Just beyond any prospects of achievement, now or in the foreseeable future.
I have good friends who are Star Trek and Babylon 5 fans who cannot be persuaded that interstellar travel will likely remain beyond reality. They Babylon about “warp speed,” “worm holes,” and other inventions of science fiction writers. But let’s do some math to understand why only our imaginations are ever likely to travel to other stars and galaxies:
In the referred-to article, former NASA physicist Marc Millis says if we make it a priority, in half a century we could send an unmanned probe to Alpha Centauri at 1/10th the speed of light. Obviously it wouldn’t be for the purpose of setting up a human outpost and a McDonalds for future tourists from Earth. It would be like probes we’ve sent to Mars, Jupiter, and beyond — just to get a closer look at those worlds, to sniff around and search for important stuff like signs of life.
So if we do make it a priority now — backed up by enormous effort and money — let’s see what we’d get and how long it would take to get it.
Millis says if we would pull out all stops, we could launch such a probe in about 50 years. It would speed towards A. Centauri at 18,600 miles a second — which is more than 2500 times faster than the fastest space probes Earthlings ever launched and almost 2700 times faster than the Apollo spacecraft that took men to the moon.
Reaching that velocity would require more than 2700 x 2700 the amount of energy that was needed to propel the Saturn rockets that took men to the moon. And that’s more than 7 million times the amount of energy it took to launch each Luna mission!
The Saturn rockets that took humans to the moon required 5.6 million lbs. of propellent. Multiply that by 7 million and we get approx 40 million million pounds. But the mission Millis proposes would require a great deal more energy than that.
First, you’d have to double the fuel needed if you want the probe to stop and study A. Centauri and not just wiz by at 1/10th the speed of light. So the energy needed would be equivalent to 80 trillion pounds of Saturn rocket fuel. But accelerating 80 trillion pounds of fuel to 1/10th the speed of light — and then decelerating it would require far, far, far, far, more energy than just accelerating and decelerating a space probe with comparable weight of the Apollo rocket — a feather weight of 6.2 million pounds, by comparison.
Of course, space travelers in science fiction use nuclear powered ships, “dilithium crystals,” and “warp drives.” With the exception of nuclear power, the rest is just that, fiction. While nuclear power might provide the needed energy at a small fraction of the weight of chemical fuels, you’d still need more than 26,000,000 pounds of Uranium-235 to propel the craft to A. Centauri and then slow it down when it gets there.
Compare this to the total amount of U-235 consumed in a YEAR by ALL the WORLD’s nuclear power plants: All those plants consume about 8000 tons of low-enriched uranium (less than 20% U-235) — about 1600 tons (3.2 millon lbs) of U-235 consumed annually.
So even if we were able to build such a nuclear powered ship to the stars, it would be a ship of fools. We would need to stock it with the amount of fission fuel ALL the world’s nuclear power plants consume in more than 8 years!
And after diverting the fortune of a million Midases to this mission, what would we get and when would we get it? See part 2.
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Part 2:
So when would our grand investment pay off?
Millis predicts that if we make star travel a priority, we could launch our first star probe in 50 years. Traveling at 1/10th the speed of light, the probe would take more than another 40 years to reach A. Centauri (the larger of a pair of binary stars of relatively minor interest since it doesn’t appear to have any planets). So it would take almost a century before this unimaginably large investment would begin to “pay off.” Not one person who would vote for in favor of such a program today would be alive when the probe reaches our nearest stellar neighbor — that is IF it even reaches the star.
We need to consider the enormity of such a technological undertaking and remember how NASA continues to suffer hugely expensive set backs when their rockets go boom. Just last year, NASA’s Glory atmospheric research mission satellite crashed into the southern Pacific Ocean due to the failure of a protective nose cone to separate. Ouch! That disaster cost almost a half-billion dollars. And it followed the loss of another very expensive environmental satellite due to a similar nose cone malfunction in 2009. Ouch! squared.
A star ship that could travel thousands of times faster than rockets carrying satellites into orbit would be far more complex and would face much greater technological challenges than just getting a protective nose cone to separate when it’s supposed to. It would not cost a half a billion, but thousands of billions to build in addition to the costs of developing and testing the required technologies that do not exist today.
What could we do with all those trillions of dollars invested over the next 50 years? Think about it. What we’ve learned about our nearest and farthest cosmic neighbors and the origins of our universe from the Hubble telescope is beyond calculation. It surely was expensive (an estimated $4.5 to 6 billion to date), but nothing like the trillions of dollars it would cost to develop and launch a probe to A. Centauri some 50 years from now.
Over the next 50 years and beyond, we can develop technologies far more powerful than the technologies that gave us the Hubble telescope. Rather than invest trillions of dollars to build a ship of fools — that, if it works and reaches its goal, would pay nothing back until a hundred years from now — we can invest our limited resources in funding space missions that pay off well.
For example, the James Webb Space Telescope (previously known as Next Generation Space Telescope) was almost killed by U.S. Congress last year due to delays and cost over-runs. Planning for this incredible eye on the universe began in 1996 and may take another 6 or 8 years before it’s completed and launched — unless the anti-science contingency of Congress succeeds in killing it.
As astoundingly successful as the Hubble telescope has been in opening our eyes to the universe, it’s a Captain Cook’s spyglass compared with this next generation instrument. The James Webb Space Telescope mirror will not only have 5 times the light-collecting power of Hubble’s, it will see in the infrared — allowing it to see through curtains of cosmic dust to study the birth and evolution of the universe and the formation of the earliest galaxies, stars, and planets. It will have even more breath-taking resolution than Hubble and — being stationed in an Earth-Sun L2 point orbit — will not have its view of the heavens constantly interrupted by Earth, as Hubble has, traveling in a low-Earth orbit.
Over the next 5 decades — the time Millis says it would take to develop the technology to send a probe to A. Centauri — we could develop and deploy ever more powerful technologies for studying our planet, our sun, and our cosmic neighbors as far as the most powerful eyes of science can see — if we invest our resources wisely.
Building a ship of fools would not be wise.
Andrew Skolnick
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Lets put some numbers together,
8E13 lbs of liquid hydrogen & oxygen at 1980s prices is $3.6/lb & $0.08/lb, respectively without adjusting for inflation that translates to $238,596 billion dollars. The 2011 world GDP was $69,970 billion, that is the rocket fuel required to do a one way trip to Alpha Centauri would be 3.41 x the 2011 world GDP using 1980s fuel prices!
Using inflation at 3% the price of fuel would increase by 11.3x 50 years from now and assuming a world GDP growth of 5% (give Millis the benefit of the doubt) world GDP would increase by 12.1x. That is, it does not get any more realistic or feasible the longer we wait.
But wait the world production of liquid hydrogen was 50,000,000 tons or about 1E11 lbs or the liquid hydrogen required to get us to Alpha Centuari is about 660x our late 2000’s world production.
Do we really think that this is feasible even in 50 years?
And there was another article A Poor Formula for Interstellar Travel which said that it would require 5 tons of antimatter to get to Alpha Centauri. Really? What does anyone think the price of antimatter would be? My guess is that in the context of world GDP it would be more expensive than liquid hydrogen, assuming that 50 years is enough time to make it. Note that in more than 70 years we still have not figured out how to do fusion how are we going to do antimatter?
Andrew Skolnick pointed me to Penn State University’s estimation of antimatter cost,
http://www.engr.psu.edu/antimatter/papers/nasa_anti.pdf
This is excellent scientific authority of Penn State University to bring us back down to Earth. I redid the calculations it is actually worse, 5 tonnes would cost $3E+18 (!!!) or 42,876x our 2011 world GDP.
Thanks this is fun. Don’t people (especially the proposers) check their facts?
Which raises the question, is this why DARPA ‘privatized’ this effort into the 100 Year Starship Study? Because they had already done their calculations and recognized that this approach was not feasible even in a 100 years?
But seriously, funding any project because it is the only one we know of is not exactly a wise approach to doing science, engineering or in any other field of endeavor.
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Benjamin T Solomon is the author & principal investigator of the 12-year study into the theoretical & technological feasibility of gravitation modification, titled An Introduction to Gravity Modification, to achieve interstellar travel in our lifetimes. For more information visit iSETI LLC, Interstellar Space Exploration Technology Initiative
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