Monday June 13th 2011


Notes & Queries 2/8/10

Prospects for Interstellar Travel

Be aware of Paul Titze’s continuing exegesis of John Mauldin’s book Prospects for Interstellar Travel (Univelt, 1992). I used Mauldin again and again as I developed my Centauri Dreams book, finding the dense and lengthy volume covered every conceivable aspect of interstellar flight as understood by current physics. But the book was published in a small press run and is hard to track down, although Amazon usually has a few copies from independent resellers available. Paul is doing the community a service by going through Mauldin chapter by chapter, highlighting the salient points with commentary.

A quote from an early chapter:

Relativity makes energy a serious problem through the limits imposed to prevent speeds greater than light. Relativity also offers tantalizing solutions: the slowing of time and Total Conversion of mass to energy. How closely propulsion might approach TC is explored in Chapter 4. One could hope to find a way to travel without the action-reaction rocket method–no exhaust, no acceleration, little travel time, no deadly beams, no titanic low-mass energy source–but these are still mostly dreams from sf. Thus far it is not surprising that “visitors” from other stars have not appeared recently nor left their garbage laying about. They also must contend with what their Einsteins discover about interstellar travel. If visitors were to arrive, one of the first facts we would want to know is “how did they do it?”

All of which, as Paul notes, impinges on the three goals once defined by the Breakthrough Propulsion Physics project:

  • Mass: Discover new propulsion methods that eliminate (or dramatically reduce) the need for propellant.
  • Speed: Discover how to circumvent existing limits (light-speed) to dramatically reduce transit times.
  • Energy: Discover new energy methods to power these propulsion devices.

Mauldin’s treatment of other propulsion options, from solar sails and beamed propulsion to nuclear fusion and antimatter, is exhaustive even if dated, but there is much to engage the interest in later chapters on interstellar navigation, the building of colony ships, shielding options, starship subsystems, and the advantages of self-replicating probes. Science fiction writers will find enough fodder in Mauldin’s pages to justify the price, as will anyone serious about making the case for venturing beyond the Solar System. Paul Titze is doing us all a service by going through these pages sequentially and with thoughtful annotations.

SPESIF 2010 Approaches

The Space, Propulsion & Energy Sciences International Forum 2010 will be held beginning February 23 at the Kossiakoff Center, Applied Physics Lab, Johns Hopkins University. Aerospace engineer Glen Robertson moderates the sessions, which include NASA’s Les Johnson presenting “From Research to Flight: Surviving the TRL ‘Valley of Death’ for Robotic and Human Space Exploration,” and a panel on the first fifty years of the space age and prospects going forward moderated by Roger Launius, curator of the National Air and Space Museum. Robert Zimmerman, author of The Universe in a Mirror and other books, will speak at the conference’s banquet. More information available at the IASSPES site.

Looking Back at Life Elsewhere

In a lively new article, the Daily Mail takes a retrospective look at two events that tantalized us with the possibilities of finding extraterrestrial life. In fact, author Michael Brooks simply declares Gilbert Levin ‘the man who found life on Mars.’ Well, we thought so for a few days back in 1976, when an experiment on board the Viking Mars lander got a positive result, prompting Champagne, a party, and a jubilant phone call from Carl Sagan. But later experiments found no carbon in the Martian soil, the Champagne lost its bubbles and Sagan retracted his congratulations. These days Levin would like to see the mission results revisited, especially the possible malfunctioning of the carbon-detecting instrument, but we may have to wait for future probes to really understand what Viking did or didn’t find.

Which takes us back to August 15, 1977, when Jerry Ehman found a puzzling signal in data from a radio telescope in Ohio. The signal’s frequency looked promising — it came in at the 1420 MHz hydrogen line — and to this day Ehman says ‘I am still waiting for a definitive explanation that makes sense.’ From the Daily Mail’s article:

Ehman and his colleagues have explored every possibility: military transmissions, reflections of Earth signals off asteroids or satellites, natural emissions from stars, but nothing fits.

The strangest thing of all is that it came from a blank patch of sky. When Ehman and his colleagues looked at the exact location of the source, it turned out to be devoid of stars. Ehman’s only thought is that it could have been beamed from a spaceship travelling through the universe in search of some sign of life.

Not that he is totally convinced it really was aliens but he has never come up with a better explanation.

‘It had all the earmarks of being a signal from an intelligent civilisation,’ Ehman told me on the phone. ‘There it was, like it was saying, “Here I am – can you see me?”‘ But, he concedes, we may never have proof one way or the other.

Proof, of course, is what we need, but the WOW! signal still stands as perhaps our most interesting single SETI reception, one that could not be confirmed but impels many in the field to renewed commitment to the search. Brooks wonders whether we have been both extraordinarily lucky in possibly receiving a genuine signal of extraterrestrial life and amazingly careless in that we couldn’t follow it up or, for that matter, the elusive evidence of what happened on Mars. Good stories both, but the only practical thing is to go forward with new life detection methods for planetary surfaces as well as the depths of interstellar space.

The Shape of ETI

What would any alien we heard from via SETI actually look like? New Scientist took a crack at this question in its January 23 issue (thanks to Gary Bennett for the tip), noting factors like its probably predatory instincts, or the fact that an extraterrestrial must be able to send and receive radio waves, laser beams or some other forms of communication. That seems to presuppose a basic technology and a social structure. From the article, quoting astrobiologist Dirk Schulze-Makuch :

So message-sending aliens will probably have some form of society. It need not be anything like human societies, however. “There are meta-intelligences in the societies of bees and termites. I can imagine something like a termite or ant colony that gets really intelligent,” says Schulze-Makuch. This does not tell us, however, whether they will be furry, scaly or slimy. Even on Earth, clever brains come in a wide variety of packages: dolphins and primates, parrots and crows, sea otters, honey badgers, octopuses and squid.

Yes, and what about convergent evolution? Do hearts and eyes and other features develop independently in different branches of life’s tree? We might then find aliens with recognizable eyes, and probably some kind of manipulating organs to work with their technology:

Putting it all together, the daring astrobiologist might be prepared to make a very small bet that SETI-type aliens will be social multicellular predators with eyes, sexes, and sticky-out bits of some sort. Unless, of course, the aliens were usurped by smart machines or decided to modify themselves using biotechnology. In that case, we might find tentacled monsters, pale skinny humanoids, shimmery beings of pure energy…


This article was originally posted on Centauri Dreams