Small Payloads to the Stars

by Paul Gilster on April 3, 2014

Making things smaller seems more and more to be a key to feasibility for long-haul spaceflight. Recently I went through solar sail ideas from the 1950s as the concept made its way into the scientific journals after an interesting debut to the public in Astounding Science Fiction. We also discussed Sundiver missions taking advantage of a huge ‘slingshot’ effect as a sail skims the photosphere. These could yield high speeds if we can solve the materials problem, but the other issue is making the payload light enough to get maximum benefit from the maneuver.

It puzzles me that in an age of rapid miniaturization and increasing interest in the technologies of the very small, we tend to be locked into an older paradigm for starships, that they must be enormous structures to maintain a crew and carry out their scientific mission. Alan Mole’s recent paper reminds us of an alternative flow of work beginning in the 1980s that suggests a far more creative approach. If we’re going to extrapolate, as we must when talking about actual starships, let’s see where nanotech takes us in the next fifty years and start thinking about propulsion in terms of moving what could be a very small payload instead of a behemoth.

I think sails connect beautifully with this kind of thinking. Mole envisions a sail driven by a particle beam, with the beam generator in Earth orbit fed by ground-based power installations, but we continue to look at other sail concepts as well, including laser and microwave beaming to ultralight sails made of beryllium or extremely light metamaterials. Payload-inefficient rockets don’t scale nearly as well to the kind of interstellar missions we are thinking about, but sails leave the propellant behind to enable fast missions delivering extremely small payloads.

This kind of thinking was already becoming apparent as early sail work emerged in the hands of Konstantin Tsiolkovsky, Fridrickh Tsander and others, and I’ll point you back to From Cosmism to the Znamya Experiments for more on that. For now, though, have a look at the marvelous Frank Tinsley illustration below. Here’s a startlingly early version (1959!) of sails in action, painted before Cordwainer Smith’s “The Lady Who Sailed the Soul” and Arthur C. Clarke’s “Sunjammer” ever hit the magazines. When Robert Forward began working on laser-pushed lightsails, he would have had images like this from popular culture to entice him.

solarsail_tinsley

Image: An early look at the solar sail from a 1959 advertising image by Frank Tinsley. Credit & copyright: GraphicaArtis/Corbis.

Tinsley’s career is worth lingering on. A freelance illustrator known for his cover paintings for pulp magazines, he covered a wide range of subjects in magazines like Action Stories, Air Trails, Sky Birds and Western Story, with a stint in the early silent film industry in New York City in the 1920s, where he served as a scenic artist and became friends with William Randolph Hearst. By the 1950’s, he was illustrating articles for Mechanix Illustrated. A representative sample of the latter work can be seen here, packed with speculations about futuristic technologies.

But back to sails carrying small and innovative payloads. In a 1998 paper in the Journal of the British Interplanetary Society, Anders Hansson, who had two years earlier described what he called ‘living spacecraft’ in the same journal, reported on NASA Ames work into spacecraft consisting of only a few million atoms each. The study speculated that craft of this size would travel not as single probes but as a swarm that could, upon arrival at a destination system, link together to form a larger spacecraft for exploration and investigation.

Gregory Matloff, who along with Eugene Mallove wrote the seminal paper “Solar Sail Starships: The Clipper Ships of the Galaxy” for JBIS in 1981, has recently discussed the design advantages of solar sail nano-cables that would be much stronger than diamond. Nanotechnology in one form or another could thus influence the design even of the large sail structures themselves, not to mention the advantages of shrinking the instruments they deliver to the target. We may one day test out these ideas through nanotech deployed to asteroids to harvest resources there, teaching us lessons we’ll later apply to payloads that assemble research stations or even colonies upon arrival.

The Hansson paper is “From Microsystems to Nanosystems,” JBIS 51 (1998), 123-126. Greg Matloff’s 1981 paper with Eugene Mallove is “Solar Sail Starships: The Clipper Ships of the Galaxy,” JBIS 34 (1981), 371-380.

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{ 30 comments… read them below or add one }

M Mahin April 3, 2014 at 9:52

My novel Mankind Reborn (available on Amazon kindle for $1) is all about a “featherweight” mission to colonize the nearest solar system. Such a mission could be launched if the payload consisted not of conscious humans but instead consisted of the “seeds” of humans — frozen embryos and frozen sperm along with a few other items such an incubators and robots. With such an approach, you could have an entire human colony established on another planet with a star-ship payload only as big as a tractor trailer.

Wojciech J April 3, 2014 at 11:54

I clicked on Tinsley’s art and his idea of “Battlevision” was pretty accurate in terms of general concept, but completely off the mark when it comes to how it was achieved. Interesting example on how futurism meets the reality.

jpg1000 April 3, 2014 at 16:46

I worry about the limitations of a very small , very high speed, one-way propellantless craft.

1) It would have to be able to carry the equipment and sensors capable of detecting planets in another system, especially during a very high speed flyby (say 1/10th speed of light). I’m thinking acquisition, aiming, tracking, imaging.

2) It would have to be able to transmit the information back to earth.

For example, lets say it transmitted back to earth on a laser beam… it would have to carry enough power with it to create a beam that was bright enough to detect from earth. I suppose solar cells might work since it would traverse an area the size of an earth orbit in about 3 hours, but how big would those solar cells have to be vs the power of the laser?

Very small artillery sized nuclear warheads were developed in the 1950′s. Its possible some sort of burst transmission might be powered by something like that but I can’t speak to the technical details of such a system.

JPG1000 April 3, 2014 at 21:16

A perhaps more limiting concern… I’m not sure I would trust microelectronics to function after traversing deep space for 40 years or more.
We may need to go back to something like vacuum tube technology to survive that kind of environment.
Years ago a Russian pilot defected and flew a Mig-25 to Japan. There was much criticism of the technology by western experts. Especially the old style vacuum tube technology. But later they realized this type of electronics would have been able to survive an EMP burst extremely well.

Malcolm Davis April 3, 2014 at 21:47

Interesting piece. My main concern with the proposed approach of ‘very small starships’ with humans ‘hatched’ at the other end is that the humans back on Earth don’t actually go anywhere. I realise we are still seeding the cosmos with human beings (assuming the ‘hatching’ is actually possible), but we lose something vital by not going ourselves – namely, exploration. I think interstellar travel when it happens, should not just be about setting up colonies that maybe have no contact with Earth, and thus mean nothing to humans back here (short attention spans), but should be really about exploration. In that sense I much prefer the traditional concept of interstellar exploration – crewed starships. There is no reason why Mole’s approach could not also be done, but it should not be an either/or proposition. Exploration – and a sense that humans are going out into the Universe – matters.

In that sense we are still left with the challenge of how to build a ‘crewed starship’. Your commentary above…”If we’re going to extrapolate, as we must when talking about actual starships, let’s see where nanotech takes us in the next fifty years and start thinking about propulsion in terms of moving what could be a very small payload instead of a behemoth”…suggests that traditional starships must all be like Daedelus. I disagree. If we have advanced propulsion and materials technology like nanotechnology, then it may be possible to build much smaller vehicles – though not micro-vehicles like Mole is suggesting – but something perhaps with a crew of ten to twenty people, and life support and habitation to support them on a journey to nearby star systems that might take perhaps ten years – so a high percentage of ‘c’ is required. The obvious challenge is speed – how to get a vehicle close to the speed of light. This is where we should be concentrating. Its propulsion and going as fast as we can that cuts the gordian knot!

Alex Tolley April 4, 2014 at 2:18

We needn’t think that nano vs macro starships are a binary decision. For those wedded to massive worldships or human crewed fast starships, tiny, robotic craft as suggested might act as precursor vehicles to prepare an abiotic system for human colonization centuries later, when the solar system civ is large enough to support such worldship endeavors.

To my mind, the logic of tiny craft (if non-biological, Drexlerian,nano-assemblers are possible) suggests that even human scale robots will dominate galactic ‘colonization’, rather than humans (or post-humans).

At this point I am somewhat skeptical that nano-assemblers can be realized outside of SF, and particle beam accelerators that could accelerate a small vessel by 1000′s g.

I do like the notion that many small ships, many (most) that would fail in flight, would still have a high probability of a few successful journeys being made. This is the logic of r-selection which is very successful for most life forms on Earth.

ljk April 4, 2014 at 12:35

There are only two really big reasons why humans should be on interstellar voyages in person:

1. Because they voluntarily decided to leave the Sol system as a group for whatever purpose that may be (part of a cult, Star Trek reenactors who are really into authenticity, oppressed minority – actually that may apply to the first tw0 items).

2. A major catastrophe is about to befall the human race if they stay on Earth so the only recourse is to evacuate in Worldships. This assumes mind uploading is not available by the time something like this would happen, so that the humans have to take their bodies along with their brains.

For any other reason, especially exploration, machines can do the job better and with far fewer resources. And they will only become more efficient as we become capable of interstellar journeys.

Look at the Spirit and Opportunity rovers on Mars. Sure a human might have been able to traverse their exploration zones in a matter of days, but imagine trying to sustain a group of humans on the Red Planet for ten years, especially in the early stages of manned Mars exploration. We got our money’s worth and then some with these wheeled robots. Over a decade of direct measurements and monitoring of an alien world by a device that only needed solar power and did not go crazy from loneliness or boredom.

Alan Mole April 4, 2014 at 13:18

JPG1000 writes ” I’m not sure I would trust microelectronics to function after traversing deep space for 40 years or more.”

Both Voyagers have been operating over 36 1/2 years and are going strong. See Wiki,”Voyager 1″. As I recall they were built with some of the first chips ever made, crude and unreliable by modern standards. And they passed through very high radiation fields at the giant planets. Nano electronics may have unknown problems, but the Voyagers prove chips can last a long time.

Michael April 4, 2014 at 14:18

@JPG1000 writes ” I’m not sure I would trust microelectronics to function after traversing deep space for 40 years or more.”

I am glad you wrote something about that Alan, I was chopping at the ‘Bit’ when I sore that comment. As we you have said Alan electronics is not the issue here communication abilities and optics is. Unfortunately Nano electronics do have issues, such as comic rays which could do serious damage to a circuit by sputtering/charged particle events and will need hardening and/or self healing rerouting architectures.

see article

http://www.caltech.edu/content/creating-indestructible-self-healing-circuits

Alex Tolley April 4, 2014 at 14:48

@Malcolm Davis

I realise we are still seeding the cosmos with human beings (assuming the ‘hatching’ is actually possible), but we lose something vital by not going ourselves – namely, exploration. I think interstellar travel when it happens, should not just be about setting up colonies that maybe have no contact with Earth, and thus mean nothing to humans back here (short attention spans), but should be really about exploration.

Most of the human population living in the Americas, Australia, etc. did not make an exploratory journey from our origin in Africa. Most not even from outside these continents. How many non-1st generations feel as though they have somehow lost something important?
How many feel the need to reconnect with their distant past African homeland culture?

Suppose we discovered that Earth is in fact a colony from another star. Would that make our prior knowledge of history and experience somehow less valid or substantive? It wouldn’t for me as all I know is Earth.

Michel Lamontagne April 5, 2014 at 13:27

If we can build a tiny factory that can seed a colony, then we can build a tiny factory that can turn an asteroid into a few thousand solar power producing stations. Should be much simpler. Then we can power up pretty much any type of starship we can dream of. It’s not like we are in any kind of hurry.
It took 2000 years to reach all of the Polynesian Islands, can’t we expect to take the same amount of time to reach the stars?

Eniac April 5, 2014 at 16:07

The idea is neat, but totally impractical. There are a few very fundamental realities opposing it. Micro-devices cannot:

1) harness any sort of nuclear energy
2) provide enough cross-section to receive beamed power
3) provide enough aperture for telescopic observation
4) provide enough aperture for directed long distance communication
5) generate or channel enough power for long distance communication
6) shield against or hold up to impacting interstellar gas

Interstellar micro- or nanocraft: DOA, RIP

Michael April 6, 2014 at 3:20

@Eniac April 5, 2014 at 16:07

‘The idea is neat, but totally impractical. There are a few very fundamental realities opposing it. Micro-devices cannot:

’1) harness any sort of nuclear energy’

-Radioactive isotopes such as alpha emitters sprayed on ‘included in the particle beam’ could create charge differences that could be used as a source of energy.
-Maybe there is no need for nuclear power, the magnetic field could pull power from charged particles as they wiz passed the spacecraft giving up some of the spacecraft’s kinetic energy in the process.
-Nano-electronics use a lot less power than microelectronics.

’2) provide enough cross-section to receive beamed power’

-On the completion of the acceleration phase the loop reconfigures some of itself to form a dish.

’3) provide enough aperture for telescopic observation’

-There may have to be more than one optic system that uses the interferometer principle, a series of probes in parallel?

’4) provide enough aperture for directed long distance communication’

-Mentioned in point 3

’5) generate or channel enough power for long distance communication’

-Mentioned earlier point 1, use the momentum of the spacecraft as a source of energy.

’6) shield against or hold up to impacting interstellar gas’

-The loop could be wound in, but not all the way in, the magnetic field would be perhaps be strong enough to deflect the oncoming ‘ionised’ gas. Dust could be an issue, but there should be a lot less of it than gas and the frontal exposure is very small and thin.

‘Interstellar micro- or nanocraft: DOA, RIP’

-Coroners verdict ‘Open’

Neat idea

Eniac April 6, 2014 at 9:16

Probably the worst obstacle is the gyroradius of charged particles in a magnetic field. It is a critical parameter in magnetic confinement of any sort: For fusion, shielding, or magnetic sailing. It assures that none of these technologies can be scaled down.

Essentially, if your magnetic sail is too small, the particle beam will fly right through it, without providing any thrust. You’d have to increase the magnetic field, but reducing the dimensions of your coil has the opposite effect.

Here’s some math: Field of a coil goes I/R, where I is the current and R the coil radius. Shrinking the coil, I goes as R^2*J, where J is the critical current density. The field B therefore goes down linearly with shrinking R. The gyration radius Rg is mv/(qB), where mv is the particle momentum and q its charge. As B goes down, the gyroradius goes up. For the sail to be effective, Rg cannot be much larger than R. Any scaling down will quickly (quadratically) violate this requirement.

Not much can be done about this, it is quite fundamental.

Johan Hoving April 6, 2014 at 13:32

Probes of 1 kg already exists (e.g. http://en.wikipedia.org/wiki/CubeSat). What fascinates me is: Can we beam a small probe to stars much sooner than in 50 years?
Instead of reducing overall size it could be shaped like a dish for observation and communication.
Or:
Split the unobserved results of millions of double split experiments, store 50% on the craft which will compose a binary message by deleting measurements (representing zero’s) while keeping others (1′s). After this observing the patterns stored on earth will reveal the probe’s data.

Michael April 6, 2014 at 14:59

The magnetic field density (B) in the coil increases as the radius decreases with the current staying the same. Do you mean the magnetic moment, its size if you like and hence its reach?

let I = critical current density

mag mom = nIπr^2

I was trying to reduce the size of the field to a smaller region (magnetic drag) but if I want to keep the magnetic moment the same I would just need to coil it up like a solenoid (many turns) which cancels out the radius reduction element.

Now as for the radius of gyration

R = (m(rel) . v (right angle))/ (|q| . B)

That can be resolved by adjusting the relativistic mass component (velocity), it will always be higher than the sail velocity, to suit the size of the loop (coil).

I am not sure how Alan has configured the loop layout, edge on loop or like a ring facing the sun.

Eniac April 7, 2014 at 21:13

The magnetic field density (B) in the coil increases as the radius decreases with the current staying the same.

The current does not stay the same. It decreases as the square of the dimension, if the critical current stays the same.

That can be resolved by adjusting the relativistic mass component (velocity), it will always be higher than the sail velocity, to suit the size of the loop (coil).

You can only “adjust” the velocity as long as it is sufficiently larger than the sail velocity. As you scale down, you have to reduce the velocity with the square of the dimension, and you very quickly run into that limit.

Alan Mole April 8, 2014 at 13:06

Eniac writes:

“The idea is neat, but totally impractical. There are a few very fundamental realities opposing it. Micro-devices cannot:

1) harness any sort of nuclear energy
2) provide enough cross-section to receive beamed power
3) provide enough aperture for telescopic observation
4) provide enough aperture for directed long distance communication
5) generate or channel enough power for long distance communication
6) shield against or hold up to impacting interstellar gas”

To repeat, the paper is available from ramole@aol.com. It proposes a colony probe which lands nanobots to be solar powered and produce ever-larger bots and a colony. It never communicates with earth but if the colony succeeds it may establish communications someday.

OK, as to “Micro devices cannot : 1) harness any sort of nuclear energy” No sort of nuclear energy is involved so this is irrelevant.
“2) provide enough cross-section to receive beamed power” A thin superconducting wire loop 280 m in diameter is ejected and forms a circle. It is this, not the nanobots, that interacts.
“3) provide enough aperture for telescopic observation” This occurs 50 years in the future. Earthbound telescopes have observed the target planet and its orbit. The probe navigates by dead reconing until near the foreign solar system. Then it corrects by observing the planet with a small lens like the human pupil, which is quite sufficient as evidenced by the fact that we can see Venus and Mars — in fact, Venus is the brightest “star” in the night sky.
“4) provide enough aperture for directed long distance communication”and “5) generate or channel enough power for long distance communication” Since it does not communicate this is irrelevant.
“6) shield against or hold up to impacting interstellar gas” We must measure this environment, both gaseous and particulate, and its effect on different types of sheilding with a precursor mission. This is true for any interstellar mission using any type of vehicle.

Malcolm Davis April 9, 2014 at 19:21

@ljk @ Alex Tolley

Thanks for your comments. This is an interesting debate. I think the ‘machine vs man’ debate is one that will go on and intensify particuarly as the ‘machine’ component becomes more capabable and advanced. I am all for robots working alongside humans, going where humans cannot go, and perhaps acting as the vanguard for human expansion and exploration. But personally, I’d hate to see humans merely send very advanced robots to explore the cosmos in place of human beings, and humans remain forever stuck on one planet. Sure, with robots we are gathering knowledge and doing it in a very cost-effective and efficient manner, but we are not ‘there’ ourselves and I feel we lose something tangible by not going ourselves. Its a philosophical issue. Humans have always been exploring, and I don’t believe we are wired to stop doing that, nor will we accept surrogate machine explorers in our place if there is a credible technological means for us to go ourselves. There will always be people who want to go out there and visit other worlds in person, and will never be satisifed just remaining on one world, particuarly as we begin to discover Earth-like exoplanets.

Alex – your points about African migration are well taken, but I’d argue that humans have changed since early man, and are much more aware of the environment around them, and ask questions to a much greater degree. So from the perspective of the humans stuck back on Earth, watching these tiny ships go out to colonise other worlds, but knowing they will never see them with their own eyes, that will be a sad day. Run time backward to the 15th and 16th Century, and the colonisation of North America – what made people want to go? Why were they not content just to sit passively in Great Britain or Europe? They wanted to go because they wanted to open up a new frontier and live a new life. Now go forward into the future – say, 300 or 400 years – and we have discovered a means to build starships which can take humans to nearby solar systems. Will humans be any less curious about a new world, and less desiring to open up new frontiers? Would they really accept being stuck on one planet, even though the technological means now exists to spread through the galaxy?

I guess what I’m saying is that humanity is going to feel rather short-changed if one day, we have the technological means to go to the stars, but then we are told – no, ‘humans’ can’t – only robots can. Human nature being what it is, that won’t cut it. It is not only Trekkies that want the future where humans are exploring the cosmos in person. I think most people would want that opportunity if it were made available. And they will want to go themselves – and not be satisfied that someone else, hatched from a micro-ship will get to experience standing on the soil of a new planet.

There is no reason you cannot do the ‘hatch-ships’ (if you want to call them that) as well, but I think it would be a mistake in philosophical and sociological terms to deny the humans that exist at that time, on Earth, the chance to explore the galaxy first hand. And those explorers must retain a link home. I guess I’m arguing for a ‘Star Trek’ future I know. But I see nothing wrong with that vision per se, if the technological challenges could be overcome (and they are huge, granted – including ‘new physics’). I’d argue that its a brave person who would say we will NEVER achieve something like that in the future.

Eniac April 10, 2014 at 0:24

Alan Mole: Thanks for your replies. My comments were more intended for those who wanted to send microprobes, i.e. probes even smaller than the 1kg you envision.

Your concept, as you say, addresses most issues quite well. I am still concerned about the survivability of the loop under the impact of two sources of hard radiation: Interstellar gas from the front and the driving beam from the back.

The driving beam is particularly powerful, when deflected by the field it should form a more or less isotropic super-hot plasma that might instantly incinerate everything in its vicinity. Even if you can somehow arrange the loop to be shielded completely from the beam by its own field, this might not work against the gas, which is neutral. We know the nature and density of the gas, so we do not really lack data here. At relativistic velocity, the gas imparts considerable heat flux and may also cause much worse damage by erosion.

intercoastal April 11, 2014 at 2:47

I think I have to agree with above commenters that small probes surviving hitting an interstellar dust grain is… problematic. At even 1% of c (3,000 km/s) an object has kinetic energy equal to roughly a million times its own mass in TNT … that one microgram dust grain is hitting like a fairly big rifle bullet, several thousand joules. At 10% of c it’s a hundred times worse, now that dust grain is a hand grenade.

I also think humans being raised by AI is really ethically scary and likely to lead to a really maladjusted colony. I am very skeptical of brain uploading or strong AI, at least with conventional computers (as opposed to say neuron-based biological brain-computers or quantum computers or something) — neurons are not binary switches, the fundamental basis is very different and I’m not sure that gap can be bridged, at least in a functional and not-horrible-mess manner.

Alan Mole April 12, 2014 at 22:39

Regarding the ethics of AIs raising children, my plan is to read out human brains and run them in android bodies, as in the anime Ghost in the Shell.

In the paper I say “It looks more possible to reproduce human intelligence and memory by placing them in a human brain by wiring the synapses or running them as a program in an android. The futurist Raymond Kurzweil predicts that it will be possible to read out a human mind and run it in a computer. Indeed, by 2045 he predicts this can be done for all the people on Earth and their thoughts run in the machine a billion times faster, leading to unimaginable progress per year. He calls this event the Singularity.[9] Supporting this possibility, Moore’s law is continuing as Kurzweil predicted, memory seems adequate today, and actual brain architecture is being simulated — in 2009 for a single column from the cortex of a two-week old rat, with a human brain simulation predicted by 2019.[10] The work was done by the Blue Brain Project headed by Henry Markram. The Swiss government and the European Council recently awarded one billion euros to the project over ten years. US President Obama has asked Congress for a hundred million dollars a year for a Brain Mapping Initiative. Clearly the plans are taken seriously.

It is impossible to predict whether or when this research will lead to the Singularity but it is likely that in fifty years it will be possible to run human brains on tiny CPU’s and these will be able to direct nanobots to build androids and then inhabit the androids and build a full colony.”

Someone has said that using androids to explore will rob us of the joy and that the thrill of human exploration is the main reason for going in the first place. I agree with this but I think the greater problem is that the Singularity will be so much smarter than we are that it will make all the great discoveries, probably including FTL travel, and we will be happy and comfortable but irrelevant. We will lose the chance to be great and make a difference in the world. Even if the Singularity takes much longer than Kurzweil imagines, Watson is pretty smart now and is answering questions like “What is the best treatment for kidney cancer in a patient with diabetes and heart failure?” How long before it starts suggesting research, and then making *all* the good suggestions for research?

How much longer will we be important?

Eniac April 13, 2014 at 0:29

intercoastal: The real problem is the gas, not the dust. The gas is 100 times denser. At ~ 30%c any shield (or loop) will be heated white hot from its kinetic energy alone. Erosion by sputtering (also caused by gas molecules) is an additional hazard, potentially much worse.

Dust grains are a red herring. While devastating if of the right size and hit, they are easily either too rare or too small to be relevant.

Michael April 13, 2014 at 11:12

@Eniac April 13, 2014 at 0:29

‘The real problem is the gas, not the dust. The gas is 100 times denser. At ~ 30%c any shield (or loop) will be heated white hot from its kinetic energy alone. Erosion by sputtering (also caused by gas molecules) is an additional hazard, potentially much worse.’

I agree that dust is quite rare and that the gas is the main concern however the loop is malleable. We could wind it up to form a coil reducing frontal area as I have mentioned before or even remove the power and string it out to form a long spear which would significantly reduce the frontal area to mm^2 (the payload would then be largest).

stephen April 15, 2014 at 14:31

James Blish’s story, “Surface Tension” posited genetically engineered microscopic humans adapted to another planet.

The silly Eddie Murphy movie, “Meet Dave” had miniature humans inside a starship which looked like Eddie Murphy, who also plays the captain of the ship. I wish Stephen Baxter and Terry Pratchett had worked on that one.

Jason Smith April 17, 2014 at 0:02

Just a thought. Launch several Xlarge magnification lenses ringed with solar panels (1 per year) to refocus, realign, & boost laser/sunlight onto sail for greater velocity.

Hubert April 17, 2014 at 4:41

Unfortunately, the problem with sails is that a spacecraft can’t accelerate enough to get out of the solar system. However, it is also not a good idea to boost it by means of a beam. Since its becomes difficult to navigate and hard to deccelerate on arrival. Therefore, I think it is a better solution to the problem of accelerating out of the solar system, that the spacecraft itself captures ions from the sun while solar energy is used to generate power for an ion engine. A few laps around the sun would provide enough speed to get away.
During the trip the spaceship used nuclear power to stay on course, and upon arrival to another solar system, the sun is used to slow the ship down, by using the same method as when the spaceship took off.

Michael April 17, 2014 at 14:36

@Jason Smith April 17, 2014 at 0:02

‘Just a thought. Launch several Xlarge magnification lenses ringed with solar panels (1 per year) to refocus, realign, & boost laser/sunlight onto sail for greater velocity.’

Although we could possibly use some of the laser energy to move the focusers outwards they are not brilliant at focusing over those distances, the lenses would have a lot of warp in them which would be hard to remove even by spinning them.

@ Hubert April 17, 2014 at 4:41

‘Unfortunately, the problem with sails is that a spacecraft can’t accelerate enough to get out of the solar system.’

Depends on how much energy you throw at it!

‘However, it is also not a good idea to boost it by means of a beam. Since its becomes difficult to navigate…’

If you use a neutral beam control fins could be used to control it electrically and with magnetic fields a smaller core need only be controlled. Maybe some of the ions used to move the craft could be hydrogen first then oxygen ions in the second pulse. They could then be captured and combined as a rocket fuel to control the crafts attitude and power on-board systems.

‘Therefore, I think it is a better solution to the problem of accelerating out of the solar system, that the spacecraft itself captures ions from the sun while solar energy is used to generate power for an ion engine.’

There are so few ions that you would have to accelerated them to very high velocity to make up for there scarcity and you are limited by the amount of energy per square meter from the sun.

‘During the trip the spaceship used nuclear power to stay on course, and upon arrival to another solar system, the sun is used to slow the ship down, by using the same method as when the spaceship took off.’

You have to move that nuclear power source, they can be quite heavy and the other sun would provide little resistance to slow the craft down.

Jason Smith April 18, 2014 at 0:13

I’m no expert, but maybe it comes down to literally building an interstellar highway of sorts: First launch the initial sail…then stagger another launch with a magnification lens (the lens will have a solar sail of its own to propel it along)….then launch a power source (nuclear powered laser, sunlight amplification, microwave, unknown technology, etc.) equipped with it’s own solar sail for propulsion (it will be propelled by yet another power source that launches behind it…then repeat these steps so on and so forth).

Initially after the first sail is launched, I imagine a SpaceX Dragon “chaser” going after it while emitting one of the power sources described above (the Dragon will have it’s own Xlarge sail to receive a “push” from yet another DragonLaser to be launched afterwards).

Once the first DragonLaser is launched…another solar lens (to refocus whatever power source is used)…then another Dragon laser propulsion system will launch…then another solar lens…and another DragonLaser…

The goal is to maintain a steady power supply for the initial sail by launching enough infrastructure to maintain that intensity (Essentially building a “space highway” to support energy flow vs. automobiles).

As better solar sails come online they will be launched and propelled by even more efficient power sources. The highway will constantly be upgraded as new technologies evolve.

At some point, the first generation of power supply units will be close enough to AlphaC that they can be redirected & used as a brake for next generation solar sails in transit. There will eventually be two lanes to the highway (the ability to send spacecraft to AlphaC and send them back).

The challenge is in the fact that it will likely take an exponential number of DragonLasers to propel the DragonLasers that go before them. By the fourth round of power supply launches, it will take eight DragonLasers to accelerate the seven DragonLasers currently in transit.

It would be like driving from point A to B by fueling up your car with one gallon of gas and then using another car to follow along with two gallons to replenish your car then add another 2 cars to replenish the replenishment car, etc. (not very efficient at all BUT if you put enough fuel cars on the road you will get there at a decent speed vs. walking).

This is the best idea I can come up with to get there in one lifetime…

Michael April 19, 2014 at 10:48

I would love to see a competition between a laser and a particle/mass beam system that could be used to move the first interstellar spacecraft. My money is on a particle/mass beam.

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