Planetary Radio: Space Exploration, Astronomy and Science - A Microwave Push to the Stars?

Episode Date: January 13, 2003

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This is Planetary Radio. Whether you're listening on KUCI or the web, we welcome you back to Planetary Radio. I'm Matt Kaplan. The Benford name is famous to pretty much all science fiction fans, and that name figures mightily in this week's show. This time, though, it's very much to do with science fact, as we learn how microwaves may take us to the stars. And no, we don't mean the microwave on your kitchen counter.

Bruce Betts will be here with a new and improved What's Up, including our brand new trivia contest. How long could you hold your breath in space? No, again, it's not a new challenge on Fear Factor, and we don't recommend trying this at home. But we will learn the answer in just a moment on a rather macabre edition of Questions and Answers. All that, he said breathlessly on this week's Planetary Radio. Planetary Radio. Hi, I'm Emily Lakdawalla with questions and answers.

A member from Baltimore, Maryland asked, what would happen to a human body if it were ejected into space without a spacesuit? This is a very popular question. We asked Dr. Roger Billica, a NASA flight surgeon, to answer it. He explained that water on Earth is present in its liquid form due in part to the flight surgeon, to answer it. He explained that water on Earth is present

in its liquid form due in part to the air pressure exerted on it. If this air pressure is reduced or eliminated, the water will become a vapor. Remember that the human body is made up mostly of water. An astronaut ejected into the vacuum of space without a pressurized spacesuit, or even one whose suit developed a significant leak, would quickly experience this vaporization, which would affect all of the water in his body. The air in his lungs would quickly expand and rush out of his nose and mouth. The astronaut would lose consciousness

within about 10 seconds due to lack of oxygen to the brain. Next, paralysis would briefly set in, followed rapidly by generalized convulsions and then more paralysis. Can the astronaut survive? To find out, stay tuned to Planetary Radio. Dr. Jim Benford is the president of Microwave Sciences in Northern California.

His field is HPM, high-powered microwave. Now, microwaves may not be quite as sexy as their electromagnetic cousins, lasers, but a good deal of very exciting research is underway that could make your lowly microwave oven proud and perhaps even help us get around the universe. Jim, welcome to Planetary Radio. Hi there. Just how high-powered is high-powered? Well, sources have been made, individual radiating sources,

which have peak powers as high as about 10 billion watts, if you can imagine that. Wow. Was that momentary? That couldn't have been kept up for any length of time. Quite momentary for typically like 100 nanoseconds. A nanosecond is the time it takes light to go a foot. So it's a very short pulse, but extremely high power. That's incredible. I had no idea you would mention anything so high. What kinds of wavelengths or frequencies are we talking about? Since microwaves, of course, are just another form of electromagnetic energy, like light or radio. Frequencies, high power has been generated all across the microwave spectrum,

from typically 1 to 10 gigahertz is the normal range where most work is done, but there's also work all the way up into several hundred gigahertz at high powers. You know, I mentioned the lowly microwave oven that's sitting in most of our kitchens. There we're talking about, what, maybe 800 watts or 1,000 watts or something like that for, what, a high-power one? That's right, and they're typically at about 2.5 gigahertz, where water can be heated easily. And that's continuous power. And pulse power, it's a lot easier to get high powers if you pulse the device.

Don't try it with your microwave oven, but pulse devices can be made extremely powerful. So this is incredible to hear, but to what practical purpose, if you'll pardon the expression, are people considering high-powered microwaves for? There are several varieties. The one that gets the most press attention is the possibility of using high-powered microwaves for a weapon against electronics, that is, not against personnel. The idea is to burn out electronics at a great distance with a short pulse of microwaves. Now, there's also the possibility of accelerating particles in particle accelerators.

And, of course, there is our own application, particles and particle accelerators. And, of course, there is our own application, which is pushing diaphanous objects to very high speeds in order to make probes for deep space exploration. Now, of course, that's the topic that we'll spend a good deal of time on, but I'm interested in that weaponry application. So is that sort of generating the same as a nuclear weapon, an electromagnetic pulse, but without the big boom?

No, it's rather different because the pulse that's emitted by an electric weapon is called electromagnetic pulse, EMP, is a very short single pulse that is not actually a cycle or several cycles. It is only typically about 10 nanoseconds. And it's a much lower frequency than microwaves. HPM tends to weapons would be up in the gigahertz range, many gigahertz perhaps, and would be generated not by nuclear means, by simply high-voltage devices that discharge into a specially designed microwave source.

And no big boom to go with the pulse. Oh, they're pretty silent, actually. I'm guessing that this may be an area of application which is getting some interest nowadays from the administration in Washington. Well, I certainly can tell you that my Aviation Week says they're about to be used, but I cannot confirm that at all. We'll have to see. Of course, such a weapon is best used like electromagnetic warfare as a weapon of surprise.

So you wouldn't expect to hear publicity about it before or perhaps even after. Let's go back to the sort of the plowshare type of application for these high-powered microwaves. Before we go on to propulsion, there was, of course, a lot of talk some years ago about this concept of putting huge space stations up into Earth orbit or perhaps between the Earth and the Moon and having lots and lots and lots of solar cells,

and generating electricity for an energy-starved planet called Earth, and that I think microwaves were discussed as the practical way to get that power back from that station to Earth? Yes, it has been, and it's probably the best method, although lasers have been looked at, especially recently. probably the best method, although lasers have been looked at, especially recently. Microwaves are generated very efficiently, you see, and they're pretty well understood. It's pretty advanced technology. In fact, the availability of those space solar power plants in orbit would mean the availability of an awful lot of power in the form of a microwave beam, and that's what we could actually use to drive propulsion.

Well, let's turn to that topic, but as we do, let's bring another voice into the discussion. Dr. Gregory Benford is a long-time professor of physics at UC Irvine, the home of Planetary Radio's host station, KUCI. He may be best known around the world as a member of the first circle of science fiction writers. His many books include the Nebula Award winning classic Timescape from about 20 years ago. More recently, Foundation Sphere, the first book in the

second Foundation trilogy based on Isaac Asimov's classic original series. Greg, welcome to Planetary Radio. Hello there. I take it you guys have met? Yes, we used to share a womb without a view. A womb with no view. Obviously, folks, these guys have not only met,

they are pretty intimately acquainted as twin brothers. I think you're identical twins? Yes. Okay, well, that will be a topic for another week, perhaps, when we can talk about clones someday. How does it feel to be a clone, by the way? Well, it's not unique. And it's perfectly natural.

Yes. Well, like I said, maybe some other show. But let's talk about how microwaves can be used in propulsion. And, Greg Benford, you've been a part of this research with your brother, haven't you? Yes, Jim and I have done a series of experiments and worked up some theoretical ideas. We actually managed to lift a thin sheet of high-quality carbon against gravity using microwaves. That is, to accelerate it greater than the acceleration of gravity. Talk about that experiment, which I think took place at JPL?

Yeah, the first one was at JPL, and we discovered a lot of things. We did it in a vacuum chamber and put fluxes up to 10,000 watts on these carbon fiber mats. We call them sails. And lifted them. And in so doing, they get so hot that they light up. No problem seeing them in the chamber because you can see them by their own light. They glow. Yes.

Fascinating. Kind of yellow glow. We got velocities on the order of about 10 meters per second and several Gs of acceleration. Really? And how massive, how heavy was this little piece of, I think it was that you said was carbon fiber sheet? It's just a few thousandths of a gram. Now, how would that compare, let's say, to a piece of Kleenex? Lighter than Kleenex. In fact, it's so diaphanous, it's made of carbon fibers tied together by

bonding, and you can see right through it. Oh, it's literally transparent, like a piece of glass or acrylic? Not that transparent. You can see it's there, but you can also read a paper through it. It's very thin and very light. In fact, it runs around 5 or 10 grams per square meter, if you can imagine roughly a square yard, something that weighs a lot less than a penny. That's a very diaphanous material, and its lightness is one reason we can lift it. The other is that, after all, Kleenex won't take over 2,000 degrees of temperature, but this stuff does.

And I guess that would be pretty important, especially, I mean, 10,000 watts is impressive, but I suppose that if we really start talking about using this as a means of propulsion, we'll be talking about much, much higher power microwave beams. Yes, I think ultimately a deep space probe would need something on the order of a gigawatt, a billion watts. Now, that's about the power that a nuclear, a single nuclear reactor such as Diablo Canyon uses to provide electricity for people. But we're not talking about using it for a long time, perhaps on the order of an hour. And that would give a sail sufficient acceleration to escape Earth orbit

and go out into interplanetary space at high velocity. And one could do it every day, for example, instead of having these very expensive probes that are launched every decade. I want to explore this in much greater depth when we come back from a break, which we're going to take now. We will return in only about a minute with the doctors Benford, Greg Benford and Jim Benford, to talk about high-powered microwave and this field called, I take it, beamed energy propulsion. Planetary Radio will continue in just a minute. This is Buzz Aldrin.

When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds, and we're building the first-ever solar sail. You can learn about these adventures and exciting new discoveries from space exploration in The Planetary Report.

The Planetary Report is the Society's full-color magazine. It's just one of many member benefits. You can learn more by calling 1-877-PLANETS. PlanetaryRadio.org, the Planetary Society, exploring new worlds. Planetary Radio returns with Dr. Greg Benford and Dr. Jim Benford. Dr. Jim Benford is the president of Microwave Sciences in Northern California, where he does lots of interesting research with our topic today, high-powered microwaves. He often works with his brother, Greg Benford, the well-known science fiction writer and physics professor here at UC Irvine, if you're listening to us on KUCI, and you probably are. Jim, you were just starting to talk about, or we were all starting to talk about, how practical it may be to use a very high powered microwave beam to accelerate a probe very quickly,

you said in the space of maybe an hour, to escape velocity, where it would leave Earth orbit and head out for parts unknown. That's amazing. I thought that it would take much longer to do that. You can certainly take much longer, and you can do that by operating at lower power, or you can simply work longer and get a much faster probe. And therein lies the possibility of going out of the solar system at extremely high velocities. The only way we really know to do that under current physical law is by using beamed energy propulsion. And there has been a lot of talk about using lasers to do that. Is the microwave

propulsion a somewhat newer topic, or has it been around just as long? Almost as long. Lasers were thought of first because they had just occurred to people earlier. But when Robert Forward, the recently deceased creator of serious ideas in this area, thought about it, he realized that microwaves might have some advantages over lasers in that you could make the sail like a screen instead of solid because microwaves can be intercepted and reflected by a screen. He also saw that microwaves are much more efficient to generate and are a far cheaper technology than lasers. But neither one has been ruled out, and I think it will all be settled on a cost basis eventually.

Greg Benford didn't, the late Robert Ford, I think he wrote a science fiction story about the Star Wisp, which was this sort of loose net of probe material or something. Yes, Bob did. The basic idea is that if you want to get to other stars, you try not to do it with a rocket. Instead, you leave the fuel at home and you beam the thrust with microwaves or, in the case of StarWisp, perhaps lasers, to the spacecraft. And you push it with that light pressure. Now, it's a very, very light pressure, of course.

No pun intended. It's like pressure of sunlight. But you can keep it up for a long, long time if you have the right kind of generating equipment and beam projection equipment, right? Right. Now, of course, you're going to go to the stars. You're going to need to accelerate it for a fair amount of time. But there's no in principle reason why this can't be used, of course, again and again. I mean, you spend all the money building the transmitter to send the beam.

Then you can send as many lightweight aircraft as you like. It's not like building a rocket, then to get another rocket you have to build a whole new one. No, you've got the transmitter. You can send out hundreds, thousands of very lightweight probes. And it's like building utility. A lot of cost if you're going to build a railroad, but once you've got the rails in place, you can run as many trains as you like. Was there a lot of discussion on topics like this last November, where I guess there was

the first international symposium on beamed energy propulsion in Huntsville, Alabama? in Huntsville, Alabama? Yes. The main focus of the meeting was in propulsion methods using lasers, but microwaves had their day as well, literally a whole day. And I think the field has really moved now forward into an expanding agenda. People can see their way technically to making these systems happen. Let's talk about what may be the first real use of microwave propulsion, beamed energy propulsion,

on a spacecraft, which of course is near and dear to the hearts of us in the Planetary Society, because it is Cosmos 1, the solar sail, which, if it gets off successfully later this year, we certainly hope so, is going to represent a lot of firsts, including this experiment that I guess the two of you are contributing to, are leading, to try and see if microwave propulsion will work on an object in space. Can you describe a little bit of that, Tim? Yes. Basically, the SAIL will be launched from a Russian submarine in the Barents Sea, as you know, off the northern coast of Russia into a polar orbit.

And Cosmos 1, which is named after the Carl Sagan TV series, will unfurl. It will be 100 feet across, and we'll see it orbit the Earth and propel itself by solar pressure for the first month of the experiment. But we'll also be tracking it and especially looking at it with the 70-meter goldstone dish, the dish that's out in the Mojave Desert that's used for deep space communications. Now, that dish has a microwave beam that it radiates at a half a million watts. We're going to catch the beam as it comes over the horizon in what we call the tracking mode and irradiate it for a period of about 20 seconds and accelerate it from the ground and measure that acceleration with accelerometers which are on board the sail.

And if this works, then you will have demonstrated for the first time that this concept of using propulsion without any rocket motors actually is practical. That's right. It's what we call a proof of principle for photon propulsion in space. It will establish a baseline enabling higher power missions in the future. Now, pulling something like this off, Greg Benford, has got to be much more complicated than just pointing a giant flashlight up at the right spot in space. You're often listed as having done a lot of the calculation that is behind this experiment

and I guess the earlier ones that have been done in the vacuum chambers. If you were to try and explain this to a mathematically challenged audience, what kinds of calculations are we talking about? Well, you take the power of the antenna we're going to use, which is a big 70-meter-across microwave dish out at Goldstone, California, which is used for spacecraft communication. And you max it up to half a million watts in a pulse, and literally you shoot at the spacecraft as it comes over the horizon,

and you hit it. The beam is larger than the spacecraft, and so the spacecraft will move across the beam, but you try to track it and keep on it as long as you can. We estimate that we can maybe illuminate it for something like two minutes before it starts moving so fast as it goes overhead that the dish can't keep up. So it's like shooting birds, really. You don't lead them.

You stay right on them. But you only have a short while to make your point. Gentlemen, we only have a couple minutes left. Greg Benford is the brother who's probably more identified with science fiction. I wonder if you could wax poetic for a moment about this experiment and what it might mean for humankind's future in space if it's successful. Well, this is the advent of a genuinely new kind of craft.

You might say the first truly 21st century spacecraft, light capable of being accelerated by beams at a great distance and also able to endure high temperatures. Because in the long run, you know, the best source of light in the solar system is the sun. And it turns out that missions to the outer solar system and beyond, to the stars, are best carried out by flying one of these light spacecraft close to the sun, then turning it full on to the sun and getting a very big push on its way out. It turns out you can get very high velocities that way if you can learn how to fly a craft that way.

It will be the first of what we call the sundiver class of spaceships. Jim Penford of Microwave Sciences, is this, do you think, the most practical way to really get around the solar system and maybe even reach the stars? Well, clearly the practical way to get around the solar system right now is rockets, but they have a very limited velocity. As we can see, the outer solar system is very difficult to reach. For going beyond the solar system, I think this is really the only way we understand to do it. Gentlemen, we're about out of time for this segment.

It has been a great pleasure talking to you, and we will eagerly await the results of your experiment in driving a spacecraft, Cosmos 1, the first solar sail, with microwave energy, and good luck with that. Thank you. And I hope we can talk to you again soon on Planetary Radio. We've been talking with Jim Benford, Dr. Jim Benford, and Dr. Greg Benford, brothers and also brothers in creating a form of propulsion that, who knows, maybe it will take us to the stars.

Planetary Radio will continue in just a moment. Hi, I'm Emily Lakdawalla, back with Q&A about what would happen to an astronaut exposed to the vacuum of space. After about 30 seconds, our hapless astronaut would be paralyzed and unconscious. The water in his body's soft tissue would quickly vaporize. Because water vapor takes up more volume than liquid water, his body would swell markedly, possibly up to twice its normal size if it were not restrained by a spacesuit. His arterial blood pressure would plummet within 30 to 60 seconds, while his venous pressure would rise due to distension of the veins by water vapor.

Gas and vapor would continuously flow from his airways. This continuous evaporation and outflow would cool his mouth and nose to near-freezing temperatures. The circulation of his blood would cease. It's very unlikely that an astronaut suddenly exposed to a vacuum would have more than five or ten seconds to help himself before he lost consciousness. However, some animal studies from the 1960s suggest that if immediate help is at hand, recompression within 60 to 90 seconds might save his life. Got a question about the universe? Send it to us at planetaryradio at planetary.org and you may hear it answered by a leading space scientist or expert. That's planetaryradio at planetary.org. Be sure to provide your name and how to pronounce it, and tell us where you're from.

And now, here's Matt with more Planetary Radio. And we end another edition of Planetary Radio, as we always do, with What's Up, featuring Bruce Betts. Bruce, welcome back. Thank you. We are going to introduce a couple of new little extras as a part of the What's Up segment, and we're going to get to those in just a moment. But first, what's up? What's up in the sky? Well, we've got four planets that are nicely up and easy to see,

two in the evening, two in the morning. Saturn is easy to see shortly after, right after sunset in the evening, 2 in the morning. Saturn is easy to see shortly after, right after sunset in the east, and then it moves up. So even by early evening, it's high in the sky in the east. And by kind of late evening, say 10, 11 p.m., it's almost right overhead. It's in the south and very high up, brightest thing in that area, and is really good to look at if you have a small telescope right around now. Jupiter, extremely bright and rising shortly after sunset in the east and moving up in the sky as the night goes on, brighter than any star in the sky. In the morning, rising around 4 a.m. is Venus, and you can see that in the east through dawn, basically, and Mars will be off to its right.

It's much, much dimmer. And the two of them, if you watch them over progressive mornings, are actually appearing to move apart over the next two or three weeks quite significantly. And when you were talking about how Saturn later in the evening will be high in the sky, it's actually the higher up in the sky, the closer to the zenith, as we say, is the better for the viewing, isn't it? Yes, excellent point, because you get it. You're not looking through as much of Earth's atmosphere. Earth's atmosphere is always the causer of problems when looking at astronomical objects,

and if you can get something right overhead, that's by far the best time to look at it. Well, I said at the outset that we have a couple of new little pieces of this What's Up segment to do, and I think we're going to go over one of those now. Sure. We'll go to random space fact. We'll have to put some appropriate echo behind that. Indeed. Now, on each of the following shows, we'll give you just a quick little space fact for your listening pleasure. In this show, we've talked about travel to the stars. will give you just a quick little space fact for your listening pleasure. In this show, we've talked about travel to the stars. To give you an idea of how empty space really is, if you suspend three grains of sand inside a large sports arena, one of the large basketball sports arenas,

that arena will actually be more closely packed with sand than our galaxy is with stars, emphasizing that space really is pretty darn empty out there. And big. And really, really big. Wow, that's amazing. Let me give you a This Week in Space history real quick, which is on January 14, 1969, there was the first docking ever of two manned spacecraft in orbit, Soyuz 4 and Soyuz 5, obviously Soviet.

Now, wait a minute, because I thought that this was an American accomplishment, a couple of our Gemini spacecraft, no? No, it's interesting, it's actually not. Gemini did the first ever docking in space, but they docked with an unmanned booster, basically, and practiced docking that way. So they did the first docking.

This happens to be a subtle point of the first docking that actually had humans aboard, which was then not too long after, within months, done by the Americans as part of the Apollo program. Docking which was realized from very early on as an essential part of spaceflight, that you would have to get together with other things, for example, the lunar module, the Apollo lunar module, and the command module. Right. Very important skill.

And continues as such today with the space shuttle. We're going to finish up now, I guess. You've got something else that's new for us that we think is going to be, we hope, exciting and fun for people. And that is a trivia question with prizes. We'll have to put the echo back in there. Prizes. Prizes.

Indeed. We're starting a trivia contest with this show that those of you listening can compete in. The winner's name will be read on the next show along with the correct answer, so tune in next week for the right answer. And the winner will also receive from us one of the items in the Planetary Society online store. This week's trivia contest, a little background. Nitrogen is the primary constituent of Earth's atmosphere. Hydrogen is the main constituent of the giant planets like Jupiter. What is the main constituent of both the Mars atmosphere and the Venus atmosphere? A fairly easy trivia question to start things out. What is that gas?

You can enter through our website. And to do that, you simply go to planetary.org, and right there on the home page, you will see a link to Planetary Radio. And if you follow that, you'll end up where you can go to a form, and you'll use that form to put in your answer for this week's trivia question, and you might be the one to win the prize. Now, if we have multiple correct answers, we're going to stick them in a virtual hat, and we're going to pull one out, and that person's name will be read on next week's Planetary Radio,

probably with Echo behind it. So this is Mars and Jupiter, just to repeat. No, Mars and Venus. Oh, I'm not Jupiter. What am I saying? Mars and Venus, two rocky planets that both happen to share one particular gas, well-known gas, as the primary constituent of their atmospheres. Yes.

Something that if you were to visit and didn't have a spacesuit, you'd want to be able to breathe. That's one way to look at it, yes. Bruce Betts, that's about all the time we've got for What's Up this week. Next week, we'll get that first answer to the trivia question, and you'll be back to tell us more about What's Up. Yes, I will. Thanks. Bruce Betts is the Director of Projects for the Planetary Society, and that is all the time we have for Planetary Radio this week. We hope you'll join us again for our next installment, Monday, 5.30, KUCI,

or on the KUCI website. Or you can hear us anytime on the Planetary Society website, planetary.org. Thanks very much for listening.