Starship Thinking

by Paul Gilster on January 29, 2016

It’s been awhile since I’ve seen Ian Crawford (Birkbeck College, London) — I think we last talked at one of the 100 Year Starship events — but I’m pleased to see his latest popular essay How to build a starship – and why we should start thinking about it now. A professor of planetary sciences and advocate of manned space exploration here in the Solar System, Crawford takes on the necessary task of acquainting a larger audience with something Robert Forward put forth as a maxim: ‘Starflight is difficult and expensive, but not impossible.’

Following decades of work on beamed sail technologies, antimatter and space tethers, Forward wrote that line in 1996, but it summed up statements he had been making for decades. Gregory Matloff and Eugene Mallove would echo him in their Starflight Handbook (Wiley, 1989), with an emphasis on the ‘difficult’ aspect of the journey: “Starflight is not just very hard, it is very, very, very hard!” So I guess we could say starflight is hard3. Matloff, who knew Forward well, has never entertained any illusions about the magnitude of the task.

Neither has Ian Crawford, who wants to keep Forward’s injunction out there. If there were some aspect of known physics that would have to be contradicted to make star travel possible, we would look at the matter differently. But instead we find vast problems of engineering and the need to overcome huge distances with craft that can operate for decades and perhaps centuries, returning data at the end of the journey. Crawford’s work has always engaged me because of his inherent optimism, and here he makes the case that ongoing work in areas like nanotechnology may get us to at least small, robotic space probes sooner than we think.

Igniting the Effort


The driver for such an attempt, in my view, would be the discovery of a nearby world in the habitable zone of its star. But it would take more than its presence. We would also have to have data from future space missions (and the next generation of ground-based telescopes) that showed biosignatures in the planet’s atmosphere. If we could make a strong case for there being a living world around, say, a planet of Proxima Centauri, we would surely want to make closeup investigations to learn about how evolution has played out on such a world.

Crawford gives a nod to the five craft that are currently on track to leave our Solar System altogether — the two Pioneers, the two Voyagers, and New Horizons. All will fall silent long before they approach another star, though I have been trying to resurrect a Sagan idea from the early Voyager days that one or both craft could have their trajectories adjusted with a final, tank-emptying burn to make a stellar encounter more likely in tens of thousands of years. If this sounds quixotic, it’s meant to be. It would be a purely symbolic statement of what our species can do (and as for the more practical details, I’ll turn you to my essay Voyager to a Star).

Image: Professor Ian Crawford doing astrobiological fieldwork on the Kverkfjoll volcano, Iceland. Credit: Ian Crawford.

But actual scientific return is another matter. It will require not ‘new physics’ but an expansion of our existing capabilities into areas of long-lifetime instrumentation and advanced laser communications, not to mention propulsion technologies like beamed power, fusion or more exotic methods. We’ve investigated the latter in the pages of Centauri Dreams, and Crawford has written them up in a 2010 paper called “‘A Comment on ‘The Far Future of Exoplanet Direct Characterization’ – The case for Interstellar Space Probes” (citation below).

Over the years, scientists have worked out a number of propulsion designs that might be able to accelerate space vehicles to these velocities… While many of these designs would be difficult to construct today, as nanotechnology progresses and scientific payloads can be made ever smaller and lighter, the energies required to accelerate them to the required velocities will decrease.

So we can talk about nuclear possibilities. Here I lean much more strongly toward nuclear pulse methods (think Project Orion) than fusion, though it will be interesting to see what the Icarus Interstellar team comes up with as it continues to refine the 1970’s-era Project Daedalus starship, which itself was based on a still-unavailable method called inertial confinement fusion, as studied by Friedwardt Winterberg. Using the energy released by either splitting or fusing atomic nuclei has long been studied by interstellar theorists, as has the much more powerful annihilation of matter and antimatter, though this is plagued by production problems (we can’t produce remotely enough) and certainly by storage issues for large amounts of antimatter.

Everything from interstellar ramjets to beamed laser or microwave sails is in the database here. Of the latter, Crawford says this:

Spacecraft using “light-sails” pushed by lasers based in the solar system are also a possibility. However, for scientifically useful payloads this would probably require lasers concentrating more power than the current electrical generating capacity of the entire world. We would probably need to construct vast solar arrays in space to gather the necessary energy from the sun to power these lasers.

Absolutely so, making the construction of a space-based infrastructure here in the Solar System a prerequisite for sending our first true interstellar probes. As Crawford notes, we are talking about systems far too large and certainly too power-laden to contemplate launching from Earth. They’ll be constructed in space as an outgrowth of this infrastructure. “This means,” Crawford adds, “that interstellar space travel is only likely to become practical once humanity has become a spacefaring species.”

Incremental Growth into Space

So there is a path for development here that acknowledges our current inability to send craft with data return capability to nearby stars, and addresses the problem by moving step by step to gradually acquire the needed expertise. This takes us to the Moon and Mars and beyond:

We need to progressively move on from the International Space Station to building outposts and colonies on the Moon and Mars (as already envisaged in the Global Exploration Roadmap). We then need to begin mining asteroids for raw materials. Then, perhaps sometime in the middle of the 22nd century, we may be prepared for the great leap across interstellar space and reap the scientific and cultural rewards that will result.


Image: To make the first interstellar mission a reality, we’ll need to move step by step from current space technologies toward a true infrastructure moving well beyond Earth orbit. Credit: NASA.

Crawford’s is a vision that places interstellar efforts into a broad context, one that will have to build the necessary levels of public support, and of course it will also have to show short-term value by way of scientific return and, in the case of asteroid mining, the necessary raw materials for growing the infrastructure. I think the middle of the 22nd Century is a highly optimistic goal, but it’s one worth working toward, and we can’t know what kind of breakthroughs may occur along the way (again, my money is on nanotech) to make the process quicker and more effective. Star travel may be hard3, but what else would we expect when it comes to translating a great imaginative venture into a mission that will someday fly?

Ian Crawford’s paper on interstellar propulsion technologies is “A Comment on “The Far Future of Exoplanet Direct Characterization”—The Case for Interstellar Space Probes,” Astrobiology 10(8) (November, 2010), pp. 853-856 (abstract).


Larry Kennedy January 29, 2016 at 11:29

Back up on my soapbox. Part of the next little step is putting a short arm centrifuge in orbit. Lack of data leaves us helpless to make the most basic decisions.

DJ Kaplan January 29, 2016 at 13:37

@Larry: are you referring to the development of artificial gravity in space? I agree; even a trip to Mars would be simplified with such a technology.

kamal ali January 29, 2016 at 18:00

seeing the HBO series on apollo, i was struck by how each flight was bold and did something not done before as well as building on previous flights. each flight addressed a component that had to be solved before lunar landing. presently, we’re faced with at least these 3 challenges , yet AFAIK little directed progress is being made on them:
1: propulsion (VASIMR is the only active player here),
2: radiation shielding (haven’t seen any missions with active shielding),
3: zero-gravity mitigation: again: haven’t seen any progress on this: no centrifuge missions, nothing on ISS.
it’d be nice to see from NASA a roadmap spelling out milestones for each of these 3 directions.

Larry January 30, 2016 at 16:25

I agree that the technologies you mention need to be explored, and others as well. What surprises me is that no one is even attempting to try, as far as I know. With the availability of cubesats, and the ability to launch one for something on the order of $100,000 it ought to be possible to do small scale experiments to see if any of these ideas actually work. These small experiments could be funded through Kickstarter campaigns if nothing else, and at least we would learn *something*. Right now we have nothing but half-century old ideas that we aren’t even sure would work. We have to start somewhere, sometime.

Alex Tolley January 29, 2016 at 12:59

It is a very interesting question of what would be the best way to collect local data from another star, especially life forms? If we could plant a thinking machine on the surface, it could provide a wealth of information just by wandering around the planet, rather like a naturalist of an earlier era. How to get this machine to the planet’s surface is definitely problematic, and I think we are going to be very frustrated waiting the centuries before we have a solar system sized economy that could do such a thing.

Our best hope is to scale down the transport and grow the machine at the target, to reduce the energy requirements to that manageable by an Earth based economy that is achievable this century or so. That suggests to me that a beamed propulsion system is the way to go, whether a sail of some sort, or a different propulsion system that needs a lot of energy to operate.

jim moore January 29, 2016 at 14:04

Our manned space program has huge economic costs and virtually no economic benefit. And hell, low earth orbit is the cheapest and easiest part of space to send people. We are most likely not going to be sending people to Mars let alone to another solar system. There is no real economic return on investment in doing so.

kamal ali January 29, 2016 at 18:03

somewhere i read that humans expand mainly based either for economic, militaristic or religious motives (science is lower down in the list). in 2015, there was a bit of US legislation that didn’t get the attention it deserved: that allows companies to lay claim to resources they have mined in space. this sets up an economic incentive for the moon and asteroids that wasn’t there before and will be key to speeding things up.

Sean Robert Meaney January 29, 2016 at 21:38

‘no economic benefit’? I would put extinction level event at the top of economic failure causes to be avoided.
As to what to build: thirty two billion cubic feet of hydrogen will lift a million tons to the edge of atmosphere. An O’Neil cylinder can be built on the surface, and it’s design would need to be say a half million ton space cylinder with thirty two billion cubic feet capacity. Added to that would be rocket motors and fuel not exceeding half a million tons that would burn once the habitat lifted to the edge of atmosphere pushing to orbit.
Say that works. We have a colossal cylinder in space with hydrogen- the ultimate zeppelin. So we make for mars and descend slowly to the surface. We pump in mars Atmosphere and burn what hydrogen we have with oxygen from Mars creating water. We now have a giant thirty two billion cubic feet tank of water on Mars. Let’s say that converts to two billion cubic feet of water. A Fish farm. A water supply. A big habitat space where a massive amount of agriculture can be undertaken by robotic and drone systems mining mars soil for indoors agriculture.
Say that costs a trillion dollars.

Michael January 31, 2016 at 4:24

Not a bad idea.

‘An O’Neil cylinder can be built on the surface, and it’s design would need to be say a half million ton space cylinder with thirty two billion cubic feet capacity. Added to that would be rocket motors and fuel not exceeding half a million tons that would burn once the habitat lifted to the edge of atmosphere pushing to orbit.’

The cylinder itself could hold both the gaseous hydrogen for lift and liquid for the engines, imagine a kilometer high tower block been put into space.

Would it not be possible to have a large torus ring built on earth and then use the space inside the ring as the fuel storage tank for H2/O2 engines. We then we strap solid boosters to the in and outside of the ring for added thrust at start off.

Ok, there will be a lot of air resistance and therefore a more powerful rocket engine system will be needed but we will have a rotatable habitat in space ready to be kitted out.

Getting the object down to Mars surface would not be possible the way you have described it, but why would we need to go to the surface of mars with it, leave it in space.

Giulio Prisco January 30, 2016 at 3:26

But the space program has huge indirect economic benefits: it keeps our spirit alive and young. Many young people in the sixties got a full charge from the Apollo program, which lasted for a lifetime. They didn’t become astronauts, but studied science and engineering, and built the first computers, the Internet, advanced energy systems, biotech, and other cornerstones of today’s economy. The prospect of interstellar missions would similarly energize the next generations.

Etienne January 31, 2016 at 6:25

Well said!I could’nt agree more, the indirect economic benefits are considerable. We must go on with the space program

Volucris February 2, 2016 at 11:08

I kind of agree in the sense that I think the focus should be on building economic opportunity, and not in whether or not we lift people there. If there is economic opportunity, people will follow, _and stay_, not just visit. With economic opportunity I mean ISRU manufacturing, self sufficient robotic factories/replicators, etc.

Michael January 29, 2016 at 15:24

The quickest way to know about a planet around Proxima is a trip to the Sun-focus point, nothing will give the resolving power to see what is there. In fact if I were an alien species I would concentrated on that stellar-surface-point as they would be able to see an incredible amount about the universe.

Black Sci-Fi January 30, 2016 at 14:07

A trip to the Sol Gravitational Lens focal point is ~550-700AU from Earth.
I would argue that we would encounter a technological breakthrough in astronomy before the SGL probe made it to its destination and started operations.

Michael January 31, 2016 at 5:14

We don’t have to go all the way to the 550 AU point although it is best, at 250 AU the distance between the bent rays are only 400 000 miles apart, not so difficult to have a few telescopes in formation communicating to a central hub communicator/processor.

Giulio Prisco February 1, 2016 at 2:03

That’s a conclusion of one of the first SETI Institute posts on Planet 9.

“Planet 9 is far enough away that if you landed a telescope on it, you could use the Sun as a gravitational lens, producing the mother of all telescopes. It would be an instrument whose capabilities would dwarf anything on Earth or in orbit. Sure, no one’s about to rocket telescope hardware to Planet 9 anytime soon, but that’s not the same as never.”

Joe Morris January 29, 2016 at 16:23

I know Sonny White’s work at NASA’s Eagle Labs on warp drives and other exotic propulsion systems is considered by the mainstream physics community as fringe at best, but I still wouldn’t discount it yet. How many times in history has someone on the fringe made a breakthrough discovery that was considered impossible? If you don’t try then failure becomes a self-fulfilling prophecy.

Michael Spencer January 30, 2016 at 7:48

So true. It is easy to forget just how little we actually understand. Even baryonic matter is poorly comprehend. Basic questions about the universe remain unresolved: it is quantified, or not? And this leaves aside the magic of dark energy/ dark matter, about which virtually noting, including actual existence, is known.

We are primitive in countless ways. Star travel is in our future, certainly, but it is for many generations in the future and will be built upon the shoulders of countless stunning discoveries. We will look back at notions like light sails as we see Leonardo’s vertical-screw helicopter. Amusing.

There’s an SF novel many decades’ old in which a generation ship arrives- at Proxima, I recall-and is met by a teeming human civilization that has long ago discovered FTL. Perhaps Paul recalls the name.

Is FTL possible? Who knows? Far too many unknowns. Again like Leonardo, the human race of 2500 or 2800 or 3000 will see Einstein with a wistful smile.

Joe Morris January 30, 2016 at 9:38

@Michael: It will take a 1000 years if we don’t try. Even if Sonny White is unsuccessful we will have learned something. If I learned anything In forty years as an engineer we learn more from failures than successes. Personally, I think Sonny will uncover something and your thousand yeas may be cut down significantly. However, even if he doesn’t, keep in mind too many financial types judge the value of R&D only on the successes and fail to understand what we learn from our failures, and how often we discover something of value from our failures that can lead to something revolutionary. Just ask Fleming, or Robert Wilson and Arno Penzias.

NS January 30, 2016 at 16:27

Re light sails, the difference is that unlike Leonardo’s vertical-screw helicopters, they actually do work. I saw a factoid the other day that even after the invention of coal-fired steam ships, sailing ships were still economically viable on some routes. So we may well have a combination of various technologies for a long time.

As for Einstein, I wouldn’t expect him to ever have less stature than (say) Newton does now. It may turn out that Einstein’s physics are radically incomplete (like Newton’s are now known to be) but I don’t think he’ll ever be the subject of “wistful smiles”.

Michael Spencer January 31, 2016 at 8:28

Wistful hyperbole, in the case of Einstein. I suspect you are right, but the basic thrust of my comment remains. Yes, we should try, although as we face the nameless void our knowledge is woefully inadequate.

I don’t think the comparison between steam and sail, while likely the case, even begins to approach our state of ignorance.

Joe Morris January 31, 2016 at 9:21

Einstein once wrote that hundreds of experiments could prove him right but it would take only one to prove him wrong. I’m not sure relativity is wrong. It may just be incomplete. The Alcubierre-White concept doesn’t violate relativity, it just gets around it, since it’s moving space, not matter FTL

Michael Spencer February 1, 2016 at 8:21

The technology for star travel will not come from current understanding of Einstein space. It will come, I *guess*– that’s all anyone can do– it will come from a deeper understanding of how the universe actually works. There are so many missing pieces that at some point in the future Einstein space and relativity will be something of a footnote to a much fuller understanding.

Again the list, as we see it from 2016: what is dark matter? what is dark energy? why is gravity so weak? And on and on.

Mark Zambelli February 1, 2016 at 13:04

Joe said…
“It may just be incomplete.”

It most certainly is incomplete as it ‘breaks down’ and returns gobbledygook near singularities…”You broke my equation!, you mean Black Hole”.

Newton’s physics ‘falls out’ of Einstein’s much broader Relativity as a simplified special case. Sometime hence, there will be a further improvement to our understanding as we uncover and learn to weild a more powerful version yet (though string theory probably won’t ever cut it)

Mark Zambelli February 1, 2016 at 15:37

A. E. van Vogt’s “Far Centaurus” (1944) maybe?

Michael Spencer February 2, 2016 at 7:46

Exactly, and covered here by Paul:

I read that story as a kid and for some reason it had a huge effect, not leaving my memory.

Mark Zambelli February 2, 2016 at 10:30

Me too :D

Giulio Prisco February 2, 2016 at 2:29

I think our descendants in 2500 will respect Einstein as one of the greatest scientists of all times, just like we respect Leonardo as one of the greatest scientists of all times.

Of course science will continue to advance beyond Einstein and perhaps develop FTL. The logical paradoxes could melt like snow in the sun when looked at from the proper perspective. For example in Everett’s MWI there’s no logical paradox in FTL and time travel.

Brett January 29, 2016 at 17:21

Big emphasis on the “mining asteroids” part of it, not so much the other stuff. Even a robotic probe that only masses a few tons at the destination is going to start off enormous back here in the solar system, so you’ll have to assemble it from space materials.

I don’t think Humans As We Know Them Today will go to the stars, but if we do, then same thing applies. We’ll need decades of experiencing in building habitats that can survive entirely off of stores of processed resources, recycling, and nuclear power for decades or longer.

H. Floyd January 29, 2016 at 19:43

And for folks (in good company here) who read “starflight is hard” and instead think of NASA’s tantalizing Alcubierre-White FTL concept work, it’s good to recall the frustrating barriers of antimatter production:

Brett raises a great point. I have the unsettling hunch that our species will not make it very far off-world, but that a variety of descendant species engineered from our genome will. For example, spacefaring Humans 2.0 with adaptions suited to low-oxygen, low-gravity or high-radiation environments presented by modes of travel too spartan for Humans 1.0. We’re probably closer to watershed breakthroughs in bioengineering than we are in habitat engineering or spaceflight, and by the 22nd Century we may find it easier to improve the tool user to suit the tool, rather than the other way around.

For what it’s worth, we’re already a long way down that path: technology has played a directly formative role in human brain evolution since Homo erectus started cooking food. We are Earth’s first self-domesticated species; that pace will quicken by leaps and bounds if we crave life beyond Earth.

H. Floyd January 29, 2016 at 20:59

(BTW, a citation is called for regarding the Alcubierre-White drive antimatter obstacle, and how it links to Paul’s previous discussion here. I read that on Jalopnik, 6/16/14, by Jason Torchinsky. Not a snowball’s chance I could have made that association myself.)

Project Studio January 29, 2016 at 22:06

I don’t think that the Alcubierre drive requires anti-matter per-se. There is a requirement for generation of a ‘negative’ mass/energy, but it does not necessarily come from matter-antimatter annihilation.
Still that does represent a lot of energy, but consider
1. Our methods of producing energy may improve (including production of anti-matter, zero-point vacuum energy, other)
2. 750 kg of mass-energy establishes the ‘warp’ to go virtually anywhere, and
3. To go virtually anywhere at super-luminal speed.

Even the author of the citation is cautiously optimistic.

H. Floyd January 31, 2016 at 20:17

You’re right. I think I was also mistaken referring to it as “FTL.” I’d love to see it happen.

Hiro January 29, 2016 at 20:36

Several years ago I read a paper using an exotic method to attain the maximum speed 10^30 c or higher but it requires using all the energy of this universe; of course this upper bound is totally useless but how about the lower bound? Has anyone worked on the infimum of energy & speed requiring by this method?

Joe Morris January 30, 2016 at 0:35

@ Hiro. That is the Sonny White work I’m referring to. He has modified the Alcubierre system to something required significant less energy. However, most mainstream physicists don’t support his concept. He is being funded by NASA to perform some early experiments. His results to date have been controversial, so we’re waiting for more data.

Hiro January 30, 2016 at 18:54

The first section of chapter 3 in the book Large Scale Structure of Space-Time (Hawking & Ellis) mentioned a paper which examined the break down of Special Relativity below 10^-18 m. I didn’t follow it thoroughly because the math is very complicated but I remember shaking my head after reading the main assumption in Dr. White’s paper about the size of extra-dimension.

Second, even though he managed to scale down the energy problem, I still fail to imagine how the concentration of something equivalent to a small gas giant could be contained inside the body of a “starship”.

Mark Zambelli February 1, 2016 at 13:15

Hiro, I believe the first version of the theory required a Jupiters-worth of exotic matter but, by tweaking the thickness of the toroidal part of their ship design, the current mass requirements plummet to about the same as a Voyager-probe, or thereabouts IIRC. The kicker though is that requirement for ‘exotic’ matter.

Byron Rogers January 29, 2016 at 21:31

Unless remote characterization from Earth orbit or other solar orbit distance of target exoplanets can be developed to a point where a human crew knew in advance quite a bit about what to expect on arrival, it’s difficult to imagine anything in the reasonably foreseeable future except robot missions. Sophisticated robot probes could be faster and return data within (say) a century or less from from nearby stars if they could achieve significant proportion of lightspeed – is 10% feasible? considering it would have to turn around and decelerate at some (mid) point?

Otherwise travelling humans to even the nearest star would be an incredible crap shoot – worse than going into court and asking questions of a witness without knowing the likely answers in advance. Even slight variations in target parameters could make a big difference to the fate of a human crew. Robots not so much.

william f collins January 29, 2016 at 23:44

Ironically, the new TV show “The Expanse” paints a portrait of a possible Solar System-wide infrastructure – humans as a spacefaring race which exploits the resources of the inner planets – albeit a necessary step for the launching of probes to the nearby star systems. (Sadly, I suspect Dr. Sonny White’s efforts are going to be mostly a dead end. It is still worth the effort)

Giulio Prisco January 30, 2016 at 3:11

Advanced in nanotech will permit extreme miniaturization (coke-can sized probes, starwisps), which would simplify robotic interstellar missions. But once we get there, why stop at unthinking hardware? Why not send software astronauts (uploaded human minds implemented as software running on the spacecraft hardware)? I have written about the concept here:

Perhaps we could be able to do that by the end of the century. I think that is the long term future of human interstellar expansion, but in the meantime we should pursue human (that is, flesh and blood human) space exploration to keep our spirit alive and young. I think we should consider our first steps into space as first steps on a sacred road.

The problem is how to build widespread motivation and public support for interstellar missions, or (perhaps more realistically) interstellar precursor missions. Reading recent posts and comments here I am starting to really like the idea of a mission to Planet 9 (if the existence of Planet 9 is confirmed), combined with first observations at the solar focus (FOCAL mission). Such a mission would be feasible by the end of the century (I guess) and able to energize the best minds of this and the next generations. I think the 100YSS project should consider the idea.

Michael January 30, 2016 at 4:11

My favourite is the micro fission drive where a small shell of say Pu 239 is imploded by laser/ion guns to critical density and therefore efficient fission. Just before maximum density a linac can fire protons into a neutron generating target to aid the fission process or if we get enough anti-matter it could be used to start the fission process. Although neutrons are given off they can easily be slowed down and stopped by water which we need anyway.

Our biggest problem at the moment is that we very little infrastructure in space and for the foreseeable future.

Mike Fidler January 30, 2016 at 10:37

Why do you think no one has been beyond low earth orbit for 44 years? Look I am not going to beat around the bush, UFO’s have been documented to have huge oscillating magnetic fields and plenty of evidence of microwave effects. Those are the areas that we need to concentrate on if you expect to get anywhere without your brain turning into goo. Send out the probes first!

Paul Gilster January 30, 2016 at 17:39

Let me interject a policy statement re UFOs in the discussion:


UFOs are not a topic we deal with on Centauri Dreams. This is not out of lack of interest in the possibilities but because of two facts:

1) There are many sites on the Internet that specialize in the subject, so we leave it to them, and:

2) Past experience has shown that when the discussion turns to UFOs, it quickly evolves — no matter what the original topic was — into arguments over the existence of UFOs, arguments that are all too often counterproductive and take us far off topic.

Centauri Dreams is not about the existence of UFOs. We have no idea what UFOs are. Because the evidence is anecdotal and non-reproducible, the Tau Zero Foundation chooses to leave their study to others. Tau Zero Foundation director Marc Millis adds this:

“Tau Zero does not study UFOs. The topic is too mired in anecdotal, perception-based evidence rather than on irrefutable physical evidence. Additionally, a fair and impartial study would have to include a significant investigation into psychology and sociology. Such excursions are beyond the scope of Tau Zero.”

Mike Fidler January 30, 2016 at 21:52

Thank you, I thought you may have a policy like that and I totally agree, you can see the kind of junk and stupidity that go on in the internet about “###”.
Just trying to point out the problem with hard radiation on long voyages, just wish there was some place that was dedicated to discussing this topic without the problems you speak of. This could lead to a better understanding but with the topic being too mired in anecdotal, perception-based evidence rather than on irrefutable physical evidence a lot of gullible people take anybodies word about it, because of that it does have a stink of swamp gas.

Mark Zambelli February 1, 2016 at 13:24

Mike said…

“…the problem with hard radiation on long voyages, just wish there was some place that was dedicated to discussing this…”

There is a fair bit of literature about many studies into the long term detrimental effects of increased radiation during interplanetary travel over on NASAs site. En route to Mars, Curiosity even measured the environment.

Mike Fidler February 4, 2016 at 5:07

Yes, but how to stop it, huge oscillating resonating magnetic fields can keep most of the charge particles out just as the earth’s field does. With ports along the edge of the spacecraft to create plasma you could have a nice MHD aerospike rocket, all you need is some gamma rays shielding.

Mike Fidler February 4, 2016 at 5:18

Correction: With microwave ports along the edge of spacecraft, etc.

Larry January 30, 2016 at 17:04

I find it interesting that these proposed FTL spaceship designs are all variations of Star Trek’s starship “Enterprise”.

BUT if:
* the spaceship requires this ring to generate the warp field, and
* the contents of the spaceship need to be inside the ring, and
* a smaller ring results in lower total energy requirements,

THEN perhaps the optimum, minimal energy shape is not the starship Enterprise, but a flying saucer.

Mike January 30, 2016 at 22:53

It’s intetesting how the bridge section of the Enterprise is saucer-shaped. Just sayin’, is all :-)
It would be interesting to track the idea if warp drives in Sci Fi, which certainly predates Star Trek.

(Apologies for typos –
@$/^ virtual keyboard)

Mike Fidler January 30, 2016 at 22:54

Magsail and Superconducting Cuttlefish? Do the aliens have one up on us?
A very high critical current density using light weight material can enable far better magsails.

Magnetic field oscillating amplified thruster (MOA)
MOA utilises a so-called Alfvén wave, a physical principle within Magnetohydrodynamics that was described first in 1942 by the later Nobel Prize winner Hannes Alfvén and which states that fluctuating magnetic fields can induce density waves in electric conductive media (e.g. plasma, salty water, etc.). These density waves can reach very high velocities and as the particles inside the medium are coupled to them, the particles are as well accelerated to very high velocities, accordingly reaching very high kinetic energies.

Michael January 31, 2016 at 4:57

I was thinking along the lines of a laser confined to a tube powered sail. By confining the laser in the tube we can recycle the photons back and forth improving the power to momentum significantly~ tens of thousands to hundreds of thousands. By using ‘dielectric gratings’ on the sails surface and walls of the tube we can get much higher photon recycle rates as the photons don’t have to go all the way back down the tube to be reflected just to the wall and sail. It would need a long tube of a few meters in diameter which is simple to build and a few hundred to thousands of kilometers in length, longer for the higher velocities. The tube could be used even in the early stages of construction as the tube is extended piece by piece. This concept could be used to power nanoscale spacecraft -multiple sails that could self collect in space is also possible- to very high velocities, perhaps a sun diver approach and it could also be used to throw fuel package out for other craft to pick up.

Mark Zambelli February 1, 2016 at 14:09

Would the frequency of the photons change though after each successive reflection flips the sign re momentum? and would this affect the design of your tube or gratings?
Would any gains be worth the addition of the cylinder over a ‘standard’ highly collimated beam emitter (even without their optional ‘need’ for gargantuan fresnels 10s of AU away)?

Michael February 1, 2016 at 16:17

The frequency would change after each successive reflection -upholding the conservation of momentum- but ‘gratings’ can be built to have a wavelength band of reflectance so allowing for a decent amount of reflecting before absorption. Keeping the beam reflecting between the sail and laser generator without a tube would be more difficult than doing it with a tube. With the tube you would have more control to bounce the light from the walls to the sail as you could change the ‘grating’ wavelength band along the tube to account for the shift in frequency. With dielectric mirrors the accelerations can be very high reducing the need for large lenses as the absorption-temperature limit is higher.

Maximum acceleration 3.3 x 10^8 m/s^2

Article by Dr J Kare

Mark Zambelli February 2, 2016 at 5:40

Thanks for the link.

Joe Morris January 31, 2016 at 8:24

@ Hiro: Sonny proposes that changing the proportions of the ring used in his concept reduces the amount of energy required. If you do a search on Sonny White you’ll find a paper on the concept. As I said, most mainstream physicists are skeptical. I’m not a physicist, just someone who has a physics degree but Iremain hopeful. As I said, if we don’t attempt the research you’ll never find out whast’s real and what isn’t.

Mike Fidler January 31, 2016 at 10:49
Project Studio February 2, 2016 at 0:58

Great links, Thanks — Valuable conceptual constructs and bridges for better understanding of issues such as anti-matter generation, the source of inertia, the structure and behaviour of light, electrons/positrons, the distinction between EM waves and ‘matter waves.’

Brett Bellmore January 31, 2016 at 10:51

I think it’s clear that the only near-term option we have for interstellar propulsion is some variant of Orion. Though fission fragment has promise, Orion lets you achieve much higher accelerations.

It’s possible advances in fusion research will produce something better than Orion before we can start building a ship. But I have my doubts: Fusion seems to ‘want’ to happen either small and very fast, or big and steady state. Orion works with this.

In the longer term, with much more infrastructure available, beamed propulsion has enormous promise, at least for the departure phase. The problem, of course, is that any beamed propulsion system is a Deathstar. That’s a political problem, not a technological problem.

I think for that reason we’re going to be stuck with self-contained star ships.

But Orion isn’t that limiting, with some advances in biology it wouldn’t even require generation ships.

Mark Zambelli February 1, 2016 at 15:06

“That’s a political problem, not a technological problem.”

… you’ve just hit a large nail right on the head. So many things will need to be developed to see humanity ever being able to set it’s sights on reaching the stars and the main thing will be to develop beyond this ‘political phase’ humanity is even more entrenched in now than ever before. Political mindsets apply a hand-brake to development of powerful tech such as powerful emitters even though the whole point is peaceful use, even with our extinction at stake via the all eggs in one basket motiff.
Even Apollo, a political tour de force and a pinnacle for human acheivement became “usefully scientific” in the secondary mode of ‘J’ missions. And that political stance leapfrogged so many stages and cost so much that it’s crippling knock-on effects are still felt after 44years.

Yet the idea is already in its fledgling form with such endeavours as the ISS and joint missions… can this lead to a better, more cooperative, less political future where we’ll truly join forces and go about doing the big stuff… maybe after the solar system wide infrastructure has begun but I hope before, as that’ll speed things up.

Rant over.
I’m not suggesting Rodenberry got it right with his ‘enlightened’ federation assisted future Earth but it was at least a good attempt to imagine a future where we were beyond politics and able to do such wondrous things.

Michael February 2, 2016 at 10:33

‘It’s possible advances in fusion research will produce something better than Orion before we can start building a ship. But I have my doubts: Fusion seems to ‘want’ to happen either small and very fast, or big and steady state. Orion works with this.’

The Orion concept does not need to be a complete fission drive machine, a hybrid fission/fusion drive works quite well with energy yields into the 90%’s from fusion.

erika January 31, 2016 at 18:17

Great article and discussion! Surprised to not see anything about photonic drives here. Greatly enjoyed Dr. Young Bae’s awesome demo at this years 100 Year Starship convention and his delightfully enthusiastic vision of a photonic railway that would transport travelers to Mars in a handful of days (purposely slowed from max possible speed so that we can relax and enjoy our drinks).

James Stilwell January 31, 2016 at 18:58

Science fiction has gotten too strong a hold on public expectations…
Few understand that a sub-light star ship would take many many centuries just to travel one way to Alpha Centauri…
The multi-generational star ship is likely until that day when the faster than light barrier is crossed…
I heard a Stephan Hawking quote just today:

Joe Morris February 1, 2016 at 15:33

Just think of the conundrum facing physicists. Relativity doesn’t work at the quantum level and quantum physics is not applicable to the macro world. The one theory that does work, string theory, is unprovable with today’s technology, plus disliked for various reason by many in the mainstream. For astrophysics we have the dark energy and dark matter conundrums, not having an explanation for either. That’s why I like rocket science, it’s more straightforward.

william f collins February 1, 2016 at 20:21

I find the creation of a future interplanetary infrastructure build on the exploitation of resources of Mars, the asteroids , and perhaps the Moon as well. From what I read, the expenditures for the launching of interstellar space craft – unmanned or manned – will be enormous. It will take , I believe, an interplanetary wide economy backed by a supportive political structure(s) yet to be determined or envisioned. Space travel must be seen by our descendants as of some benefit other than the alleged “urge to explore” or to the ” eggs in one basket” alarmist. This has been the case in the past – for profit,for for land, for food, etc.
The Alcubierre concept seems to be wrought with several issues: the “ginormous” amount of power needed to make it operate seems to be of a prohibitive nature, and it actions may actually incinerate any human payloads (!) Dr. White H. “Sonny” White’s efforts seem to have dubious plausibility. It does seem that some of my fellow space enthusiasts are looking for what might be magical constructs – warp drives, wormholes, faster-than-light – to overcome the vast expanse of the cosmos and the challenges /dangers for human space explorers . Perhaps yet to be seen bio-engineering of the human body will be more likely to enhance human ability to survive space travel to the stars vice fantastical propulsion systems.
Ion propulsion, nuclear fusion, nuclear fission, light sails, VASIMR, – these proposed propulsion methods are now our hopes of cutting down travel times in the interplanetary (outer solar system). These may be launched within the next 10, 20, 50, or 100 years. Perhaps Dr. White’s experiments will be useful in reducing transit times across interplanetary space. Or not.

Stan Erickson February 1, 2016 at 21:41

Perhaps a good way to proceed would be doing the easy stuff first. For starters, why not work on coming up with a good reason for supporting starflight that a majority of mankind, who would have to support it financially, would agree on. If there is none, then remove all ideas requiring huge expenditures and concentrate on cheap methods only.

Brett Bellmore February 2, 2016 at 7:26

Mark, we’re not moving past the political phase. The political phase started before we began using tools. It’s built into our DNA at a fundamental level. You’d have to make us into a very different species to eliminate the politics.

That a beamed propulsion system is dealing with enough power to incinerate continents, in a solar system where people live on continents, and don’t want to be incinerated, and don’t want to have to pay ‘insurance’ for the privilege of not being incinerated, is a real problem. It falls into the class of political problems, but that doesn’t make it an illusion.

It’s actually a good reason to avoid starship concepts that require Deathstars be built, until we’ve gone a century or two without wars, to suggest that they wouldn’t be misused.

Mark Zambelli February 2, 2016 at 11:01

Oh I agree with the dangers of powerful tech as you’ve outlined above. But…”
The political phase started before we began using tools. It’s built into our DNA at a fundamental level.”

I don’t agree with this though, or rather I have a different personal opinion that recognizes humans as social creatures, tribal and altruistic yet primed for survival. These qualities predate society, never mind tool use. Politics came along after trade and cooperation, right about the time tribes became too powerful to basically get away without impacting neighbouring tribes detrimentally as then you’d have a war. It’s all our greedy, selfish, agressive, fundamental drives and motives in our predator-genes that require us to come up with a solution for the longterm peace. Politics is the grease we’ve invented that lubricates our modern world and has both a useful side and a negative side and I can foresee a future for humanity that have moved onto a more enlightened(?)/different track. Also, futures where the politics ends us all. Perhaps the problem is politics demands politicians and they’re human, ergo politics is flawed (perhaps not in the ideal case, but when have we ever had one of those?).

I hope we do get to the stage when we will be allowed to build some über-emitter for the benefits that will bring, and I hope the politics of the future is more amenable to these possibilities (I mean, are we ever going to be able to construct a space elevator even? as I’m sure the list for scaremongerors is long enough for that one too).

Michael February 4, 2016 at 5:41

Here is a great site for space related info, Paul is it possible to put it as a quick link on your list of sites?

Paul Gilster February 4, 2016 at 10:02

Could have sworn I already linked to Winchell’s site. But I’ll check.

DNWilliams February 5, 2016 at 19:02

A more basic need is long-lived power for mission electronics (instruments, onboard AI, etc.) for a mission longer than ~100 years. Pu-238 has an 88 year half-life and Am-241 is 432 years, each with power density and radiation tradeoffs. If we can’t even power a robotic mission to the nearest star with current propulsion and power technologies, how can we hope to to more?

Michael February 6, 2016 at 2:41

There is the possibility of using the interstellar ions as a source of power by the use of a coil. The coil is charged electrically and as the ions wiz passed they induce a current within the coil which could be used for onboard power. In effect you sacrifice some kinetic energy for on-board power, since we will need to travel around 10% c there will be plenty of energy available to power on-board systems.

DNWilliams February 8, 2016 at 0:54

Likely a good source of power when cruising at 10% c but a problem in the acceleration and possible deceleration phases. RTGs or some other high energy density relatively low mass systems will need to be onboard. Even for an Oort cloud explorer or other mission out to 500+ AU transit times make Pu-238 a questionable energy source.

Michael February 10, 2016 at 2:51

More than likely we will use a Pu 238 source on the acceleration phase (ejected when used up) and then on the cruise phase the local interstellar plasma. Then a longer term U235/Pu239 fission reactor, which can be started up as and when, on the deceleration phase. Within the solar system of interest we could then use solar power ejecting the heavy fission reactor.

ljk February 19, 2016 at 10:02

Mae Jemison says the biggest obstacle to interstellar flight is humans, of course:

When we do finally get out there, a little cold, deadly vacuum and radiation ain’t gonna stop us – or our machine descendants at least:

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