Deck Hands for a Four Decade Journey

by Paul Gilster on October 23, 2012

If you were offered a chance to make an interstellar journey, would you take it? How about a garden-variety trip to low-Earth orbit? I’m often asked questions like this when I make presentations to the public, and I have no hesitation in saying no. Though I’m no longer doing any flight instructing, I used to love flying airplanes, but getting into a rocket and being propelled anywhere is not for me. To each his own: I’m fascinated with deep space and hope many humans go there, and you can count on me to write about their missions and robotic ones as well while keeping my office right here on Earth.

The point is, the percentage of people who actually go out and take the incredible journeys and fly the dangerous missions is vanishingly low. But throughout history, there have always been a few intrepid souls who were willing to get into the canoes or the caravels or the biplanes and open up new territories and technologies. Thank God we have the Neil Armstrongs and Sergei Krikalyovs of this world. And somewhere in England there are the relatives of some young 18th Century adventurer who signed up as a cabin boy and wound up living out his life in Australia. People like this drive the species forward and put into action the yearning for exploration I suspect we all share.

Image: Sara Seager, who specializes in exoplanet atmospheres and interiors as the Ellen Swallow Richards Professor of Planetary Science at MIT. Credit: Justin Knight.

I’ve told this story before, but in the past few weeks a high percentage of the people coming to this site are coming for the first time, so I’ll tell it again. Robert Forward was the scientist who more than any other argued that we study methods for reaching the stars, saying that it could be done without violating the laws of physics and would therefore one day occur. Forward’s son Bob told me what happened one night at dinner when he asked his father whether he would get on a starship if it landed nearby and he was asked to go out and explore the universe, with the proviso that he could never come back. Forward’s response was instantaneous: “Of course!”

To which his wife Martha could only reply: “What about us? You mean you would just leave your family and disappear into the universe?” That made Forward pensive for only a moment as he replied, “You have to understand. This is what I have dreamed about all my life.”

MIT’s Sara Seager always manages to work the personal participation question into her talks on exoplanets. She pushes the audience this way and that and it always turns out that there are some people who would go no matter what. Here’s what she told The Atlantic’s Ross Andersen in a recent story, after describing how nuclear pulse propulsion or some kind of sail might conceivably get a spacecraft up to ten percent of lightspeed, which makes for a four-decade journey to the nearest stars:

“…I explain the hazards of living on a spacecraft for 40 years, the fact that life could be extremely tedious, and could possibly even include some kind of induced hibernation. But then I always ask if anyone in the audience would volunteer for a 40+ year journey, and every single time I get a show of hands. And then I say, “Oh I forgot to mention, it’s a one way trip,” and even then I get the same show of hands. This tells me that our drive to explore is so great that if and when engineers succeed at traveling at least 10 percent of the speed of light, there will be people willing to make the journey. It’s just a matter of time.”

I don’t doubt that Seager is right. What she might have gone on to say, if she really wanted to push the point, is that at ten percent of the speed of light, the Alpha Centauri mission that reaches its destination in 43 years is clearly a flyby. Spend more than four decades in transit and then whisk through the target system in less than a day. Would the hands still come up? My guess is that a few still would. A few would probably come up in answer to the question: “Would you go to Alpha Centauri if the only planet in the system turned out to be heat-blasted Centauri B b?” Explorers do this kind of thing — Percy Fawcett didn’t push into the Mato Grosso because he thought it was a clement place to be, nor did Robert Falcon Scott think highly of Antarctic weather.

Seager mentions what Marc Millis always calls the ‘incessant obsolescence’ problem, namely that sending one probe may simply result in its being passed enroute by another probe built later with faster technology. You can keep working that scenario until your head spins (go re-read A. E. van Vogt’s ‘Far Centaurus’ for just one science fictional take on the issue), but waiting for technology to improve gets you nowhere. At some point, you have to launch something, because we learn both through our successes and our failures, and waiting for things to happen can result in stagnation. Pushing the envelope with our crew of hand-raisers is what makes for progress.

Andersen is always a good interviewer, and he homes in on a key issue with regard to interstellar technologies. How do we develop them? Specifically, we would like to wed improved space science to the industries that can benefit from what a space infrastructure can produce, but what kind of industry would benefit from the technologies that can get us to the stars? Noting her belief that the first interstellar missions will be robotic probes, Seager responds:

Right now, I can’t see any connection between capabilities for interstellar travel and industry — at this point, it would purely be for exploration. But we can still benefit if industry decides a low-Earth orbit platform for assembly and launch would be useful. That’s because much of the fuel used for space missions is used to combat Earth’s gravity. If you have a way to assemble these probes in space, you actually have a chance to be more efficient and go faster. It’s conceivable that the private sector would be interested in something like that.

We’re going to be learning a lot more about what the private sector is and isn’t interested in as we experiment with different business models — Planetary Resources comes to mind (Seager serves as an advisor to the company), but ideas for turning a profit in space are hardly limited to asteroid mining. The suspicion here is that we will be unable to get a good read on commercial space interests until we’ve pushed that envelope as well, actually trying mission concepts and business models across a wide front to see what works. But surely Seager is right that low-Earth orbit is a key to the space infrastructure we want to build. Get there, as the saying goes, and you’re halfway to anywhere.

tzf_img_post

{ 63 comments }

GaryChurch November 2, 2012 at 20:22

“Would 14 feet be enough?”

I recall reading somewhere a grain of sand hitting your Starship at even a small fraction of C is going to explode with the force of …. a large amount of explosives. I think Star flight is pretty much reliant on there being almost nothing out there and what there is we can avoid- even specks of dust.

Avatar2.0 November 3, 2012 at 3:14

GaryChurch
“I have the worlds foremost authority on space radiation saying it is a showstopper. He says so, not me. You have……no data.”

I have decades worth of experimental data (astronauts/cosmonauts, high attitude pilots, high radiation regions on Earth).

You have an appeal to authority.
And your usual impressionistic arguments. BTW, ‘impressionistic’ means your argument appeals to phobias/fears as opposed to scientific data. If it had any validity, the pilots/astronauts that stayed in space for any length of time would not be as healthy as they are.

Dan November 3, 2012 at 10:58

Human nature being what it is, once it becomes possible to spend around $10 billion and build a ship that can make an interstellar journey, there will be no shortage of volunteers signing up to spend their own cash. I can well imagine ten such ships departing earth orbit. Back on Earth everyone’s enthusiasm would be cooled by the grisly fate of each crew, as they all slowly die by equipment failure, radiation, interpersonal conflict and disease.

But this is nothing new for humans. The desperate stories of the early colonists in North America stand as a warning to anyone trying to settle terra incognita. But the few who survived rapidly became wealthy.

Better, faster, more reliable, more comfortable ships will be built. Many more will die but eventually, humans will land on another world. Most will never return but as the technology improves, round trips will become possible and an interstellar economy will be created. One day colonisation rights will be sold on the financial markets, and squabbles between individuals and governments over such rights will be common.

This isn’t farfetched. Given suitable technology for interstellar travel it is a mathematically certain outcome because it is what humans have always done.

Eniac November 3, 2012 at 15:15

According to Wikipedia (http://en.wikipedia.org/wiki/Health_threat_from_cosmic_rays#Human_health_effects):

Estimates are that humans unshielded in interplanetary space would receive annually roughly 400 to 900 milliSieverts (mSv) (compared to 2.4 mSv on Earth) and that a Mars mission (12 months in flight and 18 months on Mars) might expose shielded astronauts to ~500 to 1000 mSv

There is a reference following that in the article for further study.

According to here: http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10098, table G-18, the annual limit for occupational whole body radiation exposure is 5 rem, which, if my calculation is correct, is about 10% of the expected exposure in interplanetary space. This would indicate that radiation is indeed a problem.

On the other hand, government health and safety regulations do not have reputation of being too lax, so a ten-fold dose just might be tolerable with a mortality risk comparable to, say, that of smoking. It is hard to find data on this, mostly because high level long-term radiation exposure is not common.
It is known that receiving ~1 Sv instantaneously (instead of annually), is assorted with a significant mortality of 0-5% (http://en.wikipedia.org/wiki/Acute_radiation_syndrome#Signs_and_symptoms).

The colorful descriptions of how radiation damage happens have to be balanced by the fact that our bodies are constantly under attack from all kinds of sources. Radiation (normally) just being a very small part of that. Viruses and such will routinely kill cells, a task that even a direct hit by radiation will not usually accomplish.

Relatively thin shields should be sufficient to reduce the interplanetary radiation by the 90% necessary to bring it into OSHA compliance. About the high energy heavy nuclei, please be aware that only part of the interplanetary radiation is galactic cosmic rays, and only 1% of that is nuclei heavier than helium.

GaryChurch November 3, 2012 at 16:51

From “Shielding Space Travelers” by Eugene Parker, 2006:

“The implications were recently studied by Wallace Friedberg
of the Federal Aviation Administration’s Civil Aerospace
Medical Institute in Oklahoma City and his colleagues. In a
report published last August, they estimated that Mars astronauts
would receive a dose of more than 80 rems a year. By
comparison, the legal dose limit for nuclear power plant workers
in the U.S. is five rems a year. One in 10 male astronauts
would eventually die from cancer, and one in six women (because
of their greater vulnerability to breast cancer). What is
more, the heavy nuclei could cause cataracts and brain damage.
(To be sure, these numbers are highly uncertain.)”

This is what we know with the data we have. Partial shielding to protect astronauts during solar storms actually increases secondary radiation from heavy nuclei so the only option without a massive shield is to stay outside the sanctuary with no protection until a storm hits and then of course the only way to survive is to go into the sanctuary.

You just keep saying the same thing over and over again Avatar; it is not a problem. It is.

GaryChurch November 3, 2012 at 16:57

https://engineering.dartmouth.edu/~d76205x/research/Shielding/docs/Parker_06.pdf

Just read it. You can accept it or dismiss it as you will. Those who want to fly to their retirement condo on Mars are going to ignore it. Those who want to explore the outer solar system on voyages lasting several years are going to understand that a massive shield and nuclear propulsion is the only answer.

Rob Henry November 3, 2012 at 21:27

Eniac alludes to a cause that has also given me pause for thought. We know how common disease causing infection, is and have an idea of how many subclinical infections occur during some epidemics, but what to the true extent of subclinical viral infection that has never been linked to disease? and what gross (but subtle?) effect does it have on us? I remember old figurers that placed the level of Epstein bar infection among sexually active Americans at 95%, an infection that they hold for life, yet few of them ever display glandular fever, and I also note that it took years to find HIV in AIDS patients, even when one research team was looking specifically just for retroviruses. Finally I note that Craig Venter found that there were ten times more virus particles in seawater than there were organisms in our biosphere.

Also I am interested in data hinting that radiation exposure is inversely correlated to malignancy (usually, below some sort of threshold), such as how cancer rates are so low for workers in the nuclear power industry even when you try to adjust for all known risk factors, and how skin cancers are more common in nightshift workers.

This problem of space radiation hazard could be so complex, that we really do need more direct data, gathered from the first wave of explores who are fully informed of the risk potentials.

GaryChurch November 4, 2012 at 13:50

“This problem of space radiation hazard could be so complex”

Like smoking cigarettes can actually be good for you- look at the proof, those 100 year old cigarette smokers.

When people refuse to accept the only possible solution they always go back to minimizing the problem.

ljk November 5, 2012 at 12:09

Manned spaceships on missions going past Luna could be surrounded by tanks of water. Similar missions in the outer Sol system could be surrounded by layers of ice. Both forms of contained water would block and reduce many types of radiation from space while being obviously useful to the crews both for drinking and propulsion.

When our early colonies settle down on the target worlds, they may have to go underground and/or cover their dwelling places with layers of surface material to continue avoiding cosmic radiation. Regarding Mars, have we determined just how radioactive the very surface of the planet is in terms of lethality to settled humans?

Rob Henry November 5, 2012 at 16:18

GaryChurch points out how most of the general population can’t comprehend the difference in significance between statistical findings, and inferences drawn from anecdotes when he comments
“Like smoking cigarettes can actually be good for you- look at the proof, those 100 year old cigarette smokers.”

And for just that reason, when the relevant statistics are entirely absent, experts should not be much better than a chimp on a Ouija board.

I could have equally well have just commented… you might be right.

GaryChurch November 5, 2012 at 22:18

“when the relevant statistics are entirely absent, experts should not be much better than a chimp on a Ouija board. ”

When something is obviously a bad idea- like going into space for years without earth radiation and earth gravity- people who keep dismissing the hazards are worse than chimps on Ouija boards.

Avatar2.0 November 7, 2012 at 6:53

GaryChurch
“When something is obviously a bad idea…”

GaryChurch, as I have already told you, appeals to authority and impressionistic anecdotes prove nothing.

You said I repeat myself – which is correct.
I repeat myself because you repeated yourself – and because what I have just said negates any arguments you presented and repeated.

Your conclusion I have quoted has no factual support – and you repeating it as if it is absolute truth changes little of this.

GaryChurch November 7, 2012 at 13:18

“what I have just said negates any arguments you presented and repeated.”

Uh huh. Let’s just think about the math; my numbers say radiation is bad for you. Your numbers say radiation is…… not so bad for you. My numbers are about 3 times larger than your numbers.
I have an authority on radiation warning of this problem. You have…….the P.R. machine for space tourism dismissing it as trivial.
Hmmmm.

Comments on this entry are closed.

{ 2 trackbacks }