Wednesday, September 28, 2011

World of Two Suns

Planets orbiting a binary star
Rocketpunk Manifesto has never claimed to be a space news blog, so I make no apology for being the last space blog in the known universe to mention last week's report of a planet found orbiting both components of a double star. (There is no indication - yet - of more than one planet in this system; see illo note at the end of this post.)

I will apologize for slower posting of late, the excuse being a couple of new work gigs I'm still breaking in.


But back to the world of two suns. The interesting thing about this - apart from the discovery itself - is that when I was growing up, and for long afterwards, the standard wise advice for any SF writer aiming for a speck of hardness was to avoid binary-star planets like the plague.

Any such planet was liable to be hurled out of its birth system. Even more to the point it was unlikely to form in the first place, disrupted before birth by the processes that formed a binary star in the first place. Which meant that in hard SF perspective, any planet of a binary might as well be 1930s baroque, with the blue sun rising as the red sun was sitting and the orange sun was at midafternoon.

Not for the first time - and surely not for the last - elegant inference has been trumped by observation.

Certainly not for the first time in the history of extrasolar planet discoveries. The first such worlds to be found, in 1993, were so hard to wrap our collective mind around - three planets orbiting a pulsar - that they were not fully acknowledged as 'real' planets.

Then came 51 Pegasi b, in 1995. The star is suitably sunlike, but no one expected a planet comparable in mass to Jupiter to be orbiting several times closer in than Mercury. And basically things have stayed weird ever since.

Before 1995, I'd venture that most people (who thought about it at all) expected more or less the same thing I did. Extrasolar planetary systems, when we found them, would mostly have the same overall organization as the Solar System. They'd have some rocky terrestrial inner planets between about 0.3 and 3 AU, and some gas giants out beyond the 'snow line.' Beyond the gas giants would be nothing much.

Details would vary, of course. Some systems might have only two or three planets, others well over a dozen. A few with planets bigger than Jupiter - even approaching brown-dwarf mass - and other systems with only Saturns or Neptunes. Most of these planets, big and small, would be on near-circular orbits, in striking contrast to the highly eccentric orbits typical of binary and multiple stars. The spacing of their orbits would likely be suggestive of 'Bode's law.'

By the current more or less official count of the Paris Observatory there are now 687 confirmed extrasolar planets. And precisely none of them are in systems with an overall architecture like I just described.

As I have noted here before, this is (probably) at least in part an artifact of observational 'selection effects.' Most of those 687 planets have been discovered by techniques that have a technical bias in favor of large planets close to the parent star. Indeed, a duplicate of the Solar System would be only at the threshold of detectability.

All the same it is starting to be just a little bit odd that so few known extrasolar planetary systems are even kinda sorta like the Solar System. Looking at the Paris Observatory website, there is just a hint that planets are more common around 5 AU - Jupiter distance - than around 4 AU or 6 AU. Some even have fairly circular orbits.

But all in all, the planets and planetary systems we have been finding have amazingly little in common with the ones we expected.


I don't want to draw very many large conclusions from this, except perhaps that 'large conclusions' are likely to be wrong. In particular, note that this particular discussion is entirely about the physical (and observational) facts about astronomical bodies, not about future human societies that might investigate those worlds, or seek to do more than investigate them.

But they are interesting, in themselves and for their possible place in human affairs, SFnal or otherwise.

Discuss.




The image comes from Space.com - but just to keep things interesting, it illustrates a discovery made last fall, not last week.

85 comments:

Anonymous said...

=Milo=



Rick:

"But back to the world of two suns. The interesting thing about this - apart from the discovery itself - is that when I was growing up, and for long afterwards, the standard wise advice for any SF writer aiming for a speck of hardness was to avoid binary-star planets like the plague.

Any such planet was liable to be hurled out of its birth system. Even more to the point it was unlikely to form in the first place, disrupted before birth by the processes that formed a binary star in the first place."


The interesting thing here is that the distance of the planet from the suns (0.7048 AU) is only 3.2 times the distance of the suns from each other (0.22 AU). It has been generally recognized that larger ratios lead to more stable orbits, but most estimates expected the minimum for stability to be more than 3.2. (I've seen a lower bound of 5 quoted somewhere, although that site doesn't list its own sources.)


"The first such worlds to be found, in 1993, were so hard to wrap our collective mind around - three planets orbiting a pulsar - that they were not fully acknowledged as 'real' planets."

"It is cool, therefore it must not exist." Far too common a sentiment.

Sure, pulsar planets might not be optimal for life (though I do wonder... just how much energy to pulsars put out?), but that doesn't mean that having planets in such an exotic place isn't cool.

If nothing else, one wonders if these pulsar planets are the charred corpses of planets that the pulsar had before its predecessor star went supernova, continuing to orbit their dead star for eternity. On the other hand, if new planets could actually form around pulsars, that would also be really impressive.


"Then came 51 Pegasi b, in 1995. The star is suitably sunlike, but no one expected a planet comparable in mass to Jupiter to be orbiting several times closer in than Mercury. And basically things have stayed weird ever since."

This is largely considered observation bias - such planets dominate the known universe not because they're necessarily more common, but because they're easier to detect.

On the other hand, it could also be the other kind of observation bias: Hot Jupiters may disrupt a solar system's other planets to the point that it's unlikely to harbor any planets friendly to life, so even if Hot Jupiters really are common, the anthropic principle still requires that they would appear unusual from the point of view of a sentient observer (like us).


"Most of these planets, big and small, would be on near-circular orbits, in striking contrast to the highly eccentric orbits typical of binary and multiple stars."

Speaking of which, Kepler-16b has an eccentricity of 0.0069, which is less than that of Earth (0.01671022), and surprisingly close (within error margins, in fact) to that of Venus.

The eccentricity of the stars themselves, though, is more, at 0.15944 (more than any non-dwarf planet in our solar system except Mercury, which is generally recognized as having an unusually eccentric orbit).


"All the same it is starting to be just a little bit odd that so few known extrasolar planetary systems are even kinda sorta like the Solar System."

So here's a question: are there any currently known solar systems where so far we've only detected far-orbit gas giants, and which are consistent with there existing rocky planets further inside that so far elude our detection?

I've poked around, and at a glance, HR 8799 especially seems to hint that way.

Anonymous said...

=Milo=



Oh, and one more thing: binary stars are very common, so even if ours isn't one, it should stand to reason that such a system featuring planets, possibly even habitable ones, would be found sooner or later. If anything, it's remarkable that it took so long.

CCL said...

Second time I'm participating here, but I just wanted to say one thing: when I was reading this entry, I was reminded of that old concept of geocentrism. I agree, in the case of stellar systems it was arguably justified (or excusable) geocentrism: our solar system was the only one we had to go on, therefore we seem to have assumed it would be normative. Not surprising, of course: all our models could only be derived from the one presented to us. Yet, as mr. Robinson observed, the exosolar planets we know now tend *not* to conform to any expectations. There are several imaginable reasons, the 'selection effect' is one of them. However, even then those new planets are only defined and interpreted in relation, or comparisson, to our solar system. They still, implicitly, diverge from the "norm" that our solar system provided us. I think there has been some sort of cultural bias (geocentrism) at play here: we are astonished by the the situations we find out there, because we assumed we're the normal ones, that our situation is the norm. For all we know, it actually more rational for gas giants to form in orbits close to their sun, or for binary star systems to have perfectly stable planets orbiting them. Not that I think that's likely, but being a human, I must be thinking geocentrically: our planetary model has always made more sense to me than those exotic exosolars. In other words: our models for how planetary systems are "supposed to" function may be logical, but I'm open to the possibility they weren't rational.

Cambias said...

How do we know this IS a stable arrangement? We may have caught a snapshot of an evolving system.

Anonymous said...

=Milo=



CCL:

"For all we know, it actually more rational for gas giants to form in orbits close to their sun, or for binary star systems to have perfectly stable planets orbiting them. Not that I think that's likely, but being a human, I must be thinking geocentrically: our planetary model has always made more sense to me than those exotic exosolars."

Well, we have more than just analogy to govern what we expect to find out there. We also have mathematical models and computer simulations. These are not perfect - there can be important factors that the model fails to account for, and formulas can be oversimplified to ease computation - but they give us some idea of what's likely and what isn't.

Thucydides said...

For the SF writer or story teller, the unusual nature of the solar systems we have discovered should lead to interesting situations.

Since Earth like planets seem to be rare, the intrepid pioneers colonizing other star systems will have to adapt to very strange settings. Solar systems with giant planets orbiting neat their sun may have extensive asteroid belts (given the giant planet probably disrupted the formation of other planets), giving rise to classical "Spacer" civilizations. If gas giants are farther out in the range of 1 AU, then colonists may choose to settle on a large moon orbiting the gas giant (with luck the moon may be as large as Mars in our system, making terraforming a possibility). I'm not sure about settling on giant "super Earth" sized planets, the high gravity may cause problems to our biologies and ecologies.

Of course, the settlers may choose to modify themselves to live in the new environments, which may lead to the question if highly modified "people" are really human or not?

Anonymous said...

=Milo=



Thucydides:

"Since Earth like planets seem to be rare, the intrepid pioneers colonizing other star systems will have to adapt to very strange settings."

Or they will select only systems that do have Earthlike planets (or moons) for settlement. Even if those are only one percent of the stars in the galaxy, that still leaves several billion planets you can live on.


"If gas giants are farther out in the range of 1 AU, then colonists may choose to settle on a large moon orbiting the gas giant (with luck the moon may be as large as Mars in our system, making terraforming a possibility)."

You can go considerably smaller than Mars. Titan manages to hold an atmosphere just fine. Furthermore, even a body too small to hold an atmosphere over geological time scales might still be able to hold one for a mere hundred thousand years or so, which should be enough for human purposes. Even an atmosphere that leaks away in a matter of centuries isn't such a big deal as long as the people who live there remember how to refill it (using the same techniques they used to add it in the first place).

Also remember that the distance might be more or less than 1 AU, depending on the size of the star.


"I'm not sure about settling on giant "super Earth" sized planets, the high gravity may cause problems to our biologies and ecologies."

Keep in mind that the gravity won't be more than 2 or 3 times Earth's or so. Given constant density (not a guarantee - larger planets may actually have lower density due to having an easier time holding onto volatiles), a planet's surface gravity will scale with the cube root of its mass. This means that a rocky planet with the same mass as Neptune (unlikely - if it's so large, why isn't it a gas giant?) would have only 2.6 gees.

2.5 or so gee is also the lower limit for when vision problems start to appear. (But granted, these experiments are usually for only several minutes at a time, not lifelong habitation.)

So on all but the improbably largest rocky planets, we're probably good to go.

Jim Baerg said...

Re: settling on SuperEarths

I've heard that in the few experiments in which lab rats were raised in centrifuges to give greater than earth gravity, the rats were healthier than the controls.

For a given density of planet the surface gravity is proportional to the radius or to the cube root of the mass, so a rocky planet would have to be a *lot* bigger for the gravity to be too high.

Anonymous said...

Having the universe validate our wildist speculations about alien planets is so cool. The more we learn about the universe around us, the more wonderful we find it; and I'm using 'wonderful' in its original usage. The exoplanets we have so far have been so far from our expectations that it boggles the mind.

Regardless of the method used, it would be so worth it to visit even some of those far off worlds. To be able to see, up close, those weird, wonderful worlds (and share with the rest of our world), would be the fulfilment of a deep-rooted fantasy held in common by many humans. Now that we've found them, just to go see them in person should be motive enough to find a way to get to them.

Ferrell

Tony said...

There's a little problem with settling gas giant satellites. Gas giants suck up all kinds of debris that comes near them. We have direct proof of that. It's not too far fetched to suppose that sometimes satellites get in the way of that debris, perhaps moreso than terrestrial planets get in the way of debris in their neighborhoods.

Jim Baerg said...

But anyone who can manage interstellar travel can divert an asteroid from a collsion course with the planet or moon they've settled on.

Tony said...

Jim Baerg:

"But anyone who can manage interstellar travel can divert an asteroid from a collsion course with the planet or moon they've settled on."

I presume you're speaking in terms of energy? Anybody that can make an h-bomb can manage controllable hydrogen fusion, right? Just because you can manage an energy source towards a given objective does not mean you have full control over it. Just because you can create a wormhole or have discovered the secret of the hyperspace jump doesn't mean you can control energies in any way you want.

Anonymous said...

=Milo=



Have we actually observed meteors large enough to damage a settlement crashing into Titan, Ganymede, etc., the way we've seen them crash into the gas giants themselves?

Because once again, common on a geologic time scale is not the same as common on a human time scale.

At least, large meteor impacts on Titan are rare enough that tectonic and erosional processes have largely managed to erase the craters.

Thucydides said...

Or they will select only systems that do have Earthlike planets (or moons) for settlement. Even if those are only one percent of the stars in the galaxy, that still leaves several billion planets you can live on.

While true, this may be irrelevant depending on what sort of interstellar travel is possible/postulated.

If the local wormhole geometry isn't correct, or your warp bubble runs out before you reach the nearest Earth-like planet, or your STL worldship's ecology will collapse thirty thousand years before you reach the solar system with an earthlike planet, you may be forced to accept what is available, rather than what is ideal.

You can go considerably smaller than Mars. Titan manages to hold an atmosphere just fine. Furthermore, even a body too small to hold an atmosphere over geological time scales might still be able to hold one for a mere hundred thousand years or so, which should be enough for human purposes. Even an atmosphere that leaks away in a matter of centuries isn't such a big deal as long as the people who live there remember how to refill it (using the same techniques they used to add it in the first place).

No doubt these conditions are true (although one of the reasons a small planet like Titan can hold an atmosphere is due to the intense cold), and ambitious or desparate colonists will do all of these things. I would expect that when choosing a planet to terraform, the colonists would try for one with lower housekeeping requirements.

Anonymous said...

=Milo=



Tony:

"Just because you can create a wormhole or have discovered the secret of the hyperspace jump doesn't mean you can control energies in any way you want."

If you can create a wormhole, the obvious solution to asteroid deflection is creating a wormhole in the path of the offending asteroid so it becomes some other solar system's problem!



Thucydides:

"I would expect that when choosing a planet to terraform, the colonists would try for one with lower housekeeping requirements."

I expect they would focus on planets that are cheap and easy to terraform. They'll probably insist on reliability and safety for their and their childrens' lifespans, but it isn't human nature to worry about things more than a few thousand years in the future, tops.

Jim Baerg said...

Tony:
Actually diverting an asteroid is something humanity is now almost able to do, while interstellar travel is at least several centuries in the future.

Tony said...

Jim Baerg:

"Tony:
Actually diverting an asteroid is something humanity is now almost able to do, while interstellar travel is at least several centuries in the future."


I wouldn't make such broad assertions.

But even if it is the case that space rock defense is is a lesser included capability, one has to remember that it's not cheap or easy. When putting together a colony equipment set, what are you going to prioritize, out of all the things possible and useful?

Tony said...

Milo:

"If you can create a wormhole, the obvious solution to asteroid deflection is creating a wormhole in the path of the offending asteroid so it becomes some other solar system's problem!"

Where does it say on the label that wormholes are that easy to create or control?

Thucydides said...

Just getting to the star system involves so much speculation and possible magitech that throwing in terraforming and planetary protection seems almost a given byproduct of such technologies.

Even if it is not, would be colonists will have plenty of time to observe the star system and make plans before they set off (or during the voyage if they are going STL) so they should be able to find "low houskeeping" worlds and avoid fairly obvious dangers such as showers of incoming comets, or if this is not possible, make plans to deal with these situations. Plan "C" is simply to write the system off as having too low of an ROI to bother with in the first place, and go somewhere else.

An interesting story might be set on a "Plan C" system which simply cannot be bypassed because of wormhole geometry or some other McGuffin.

Rick said...

Welcome to another new commenter!

HR 8799 does sound interesting, but maaan, what a heavyweight! The planet sizes and distances both are like the solar gas giants on steroids.

I tend to agree with Thucydides that if you have the techlevel for interstellar colonization you can probably deal with asteroid threats. But of course that is by no means a given.

I am also - and this should surprise no one - conservative in terms of what sorts of planets we'd be likely to colonize. Assuming that we colonize, in the classical SF sense, at all. In general, outer space is full of places that are great to visit, but you wouldn't want to live there.

Tony said...

Rick:

"I am also - and this should surprise no one - conservative in terms of what sorts of planets we'd be likely to colonize. Assuming that we colonize, in the classical SF sense, at all. In general, outer space is full of places that are great to visit, but you wouldn't want to live there."

Now there's a setting nobody's tried out, at least not explicitly: a galaxy-spanning civilization that has only a hundred -- or even a thousand -- habitable planets where people live, plus billions of places where people only go to work or study for a limited amount of time.

Tony said...

Thinking about things some more, living in habitats, on gas giant satellites, on places like Mars -- those are all part of an STL millieu, where choice is not a commodity. But if you have very efficient FTL -- let's say a light year an hour or better -- choice is every person's and institution's right. Why live on an airless ball of rock, or in a can, when you can have fresh air and a whole planet to roam just by going another thousand light years further out?

Sean said...

Rick:

"HR 8799 does sound interesting, but maaan, what a heavyweight! The planet sizes and distances both are like the solar gas giants on steroids."

I'm not much of an astronomer, but couldn't such a mass be attributed to not only the planet itself but also any moons that may orbit HR 8799 b?

Anonymous said...

=Milo=



Tony:

"Thinking about things some more, living in habitats, on gas giant satellites, on places like Mars -- those are all part of an STL millieu, where choice is not a commodity."

You're assuming that gas giant satellites are inherently less desirable than planets. This is true in our solar system - Ganymede is less hospitable than Mars, both are less so than Earth, and Titan looks appealing but has entirely the wrong chemistry - but I think it's by no means implausible for some stars out there to have gas giant moons that are as Earthlike as any planet. Why would you not want to live there?

Anonymous said...

=Milo=



Rick:

"HR 8799 does sound interesting, but maaan, what a heavyweight! The planet sizes and distances both are like the solar gas giants on steroids."

Keep in mind HR 8799 is 1.47 solar masses, and has 4.92 solar luminosity. This means planets need to be about sqrt(4.92)=2.218 times as far away to get the same amount of sunlight, and 3.177 times as far away to have the same orbital period.

With that in mind, HR 8799e is 2.78666 times Jupiter's distance, HR 8799d is 2.5164 times Saturn's distance, HR 8799c is 1.98 times Uranus's distance, and HR 8799b is 2.26 times Neptune's distance. Doesn't seem so unreasonable now!

That heavier planets are likewise probably a corollary of having a larger sun.

The size also means, though, that HR 8799 has a shorter lifespan than our sun. It currently seems to be only a few tens of millions of year old, and its total lifetime is probably in the order of one billion years, plus or minus a few hundred million. Compared to the four billion years it took multicellular life to evolve on Earth, that isn't promising. But, as I noted earlier, some millions of years is still plenty sufficient for human terraforming purposes (and there's nothing a priori stopping HR 8799 from already having a planet with prebiotic conditions).

Also, I note from those letter designations that it seems to have been the farthest planets which were discovered first. Odd, considering it's usually close-orbiting planets that are easiest to detect!

(Note: above values listed to way more significant digits than they deserve.)



Sean:

"I'm not much of an astronomer, but couldn't such a mass be attributed to not only the planet itself but also any moons that may orbit HR 8799 b?"

Moons are unlikely to contribute much to a planet's mass. Jupiter takes up 99.98% of its system, Saturn takes up 99.975%, Uranus takes up 99.9999%, and Neptune takes up 99.98%. (Note: Math may be off since I had to do it myself but you get the point.)

And while not a gas giant, Earth is 98.5% of the mass in its own system, and this is an exceptionally low value!

If a satellite actually represented a significant percentage of the total system, it would be more reasonable to model it as a double planet rather than a planet-and-moon combination.

Tony said...

Sean:

"I'm not much of an astronomer, but couldn't such a mass be attributed to not only the planet itself but also any moons that may orbit HR 8799 b?"

The mass of any moons is probably lost in the noise. The mass of our own moon is only 1.2% the mass of the Earth-Moon system. That's very much at the high end of planetary-satellite system mass ratios in our solar system (remembering that Pluto is not a planet). That's a very small sample size, compared to just the stars within 100 ly, much less the whole galaxy, but it tells us something about what to expect.

Thucydides said...

Thinking about things some more, living in habitats, on gas giant satellites, on places like Mars -- those are all part of an STL millieu, where choice is not a commodity. But if you have very efficient FTL -- let's say a light year an hour or better -- choice is every person's and institution's right. Why live on an airless ball of rock, or in a can, when you can have fresh air and a whole planet to roam just by going another thousand light years further out?

And we have the setting and conditions for classical Space Opera. Why let someone else have the nice planets when you have the ability to go there and take them for yourself. Giant battleships and space battles involving death rays of stupendous power to follow....

jollyreaper said...

track

Tony said...

Milo:

"You're assuming that gas giant satellites are inherently less desirable than planets. This is true in our solar system - Ganymede is less hospitable than Mars, both are less so than Earth, and Titan looks appealing but has entirely the wrong chemistry - but I think it's by no means implausible for some stars out there to have gas giant moons that are as Earthlike as any planet. Why would you not want to live there?"

Context, Milo, context. It was implicit that gas gian satellites were not the best real estate, for whatever reason.

Anonymous said...

@ Milo: The interesting thing here is that the distance of the planet from the suns (0.7048 AU) is only 3.2 times the distance of the suns from each other (0.22 AU). It has been generally recognized that larger ratios lead to more stable orbits, but most estimates expected the minimum for stability to be more than 3.2. (I've seen a lower bound of 5 quoted somewhere, although that site doesn't list its own sources.)

I've generally heard either 3 times the intersolar separation or 5 times the intersolar separation given as the minimum distance for circumbinary planets. (Or, for planets orbiting one component, 1/5th the intersolar separation or 1/3). So the distances here aren't *too* surprising.

Also, keep in mind that these are most likely not hard and fast limits but are most likely based on statistics of the form "x percent of circumbinary planets orbiting at distance d are ejected within n years" with the lower limit for d below which circumbinary planets are considered unlikely depending on what upper limits are chosen for x and n. Do you draw the line at the point where 50% of planets are ejected within 1 billion years? 90% within 5 billion?

Linguofreak

Tony said...

Thucydides:

"And we have the setting and conditions for classical Space Opera. Why let someone else have the nice planets when you have the ability to go there and take them for yourself. Giant battleships and space battles involving death rays of stupendous power to follow...."

I'll have mine without death rays. I like nuclear missiles and guns, a la Space Viking.

Thucydides said...

Nuclear missiles and guns are so 20th century. When you do the classical Space Opera trope you need death rays (and really improbable ones like pi0 meason guns are the best, with focused coherent gravitational beams close behind. Xasers striking targets at one light second away are distant third).

On a more serious note, invoking magitech like cheap and easy FTL will unleash a host of second and third order effects; cheap and easy diversions of asteroids is probably the least of them and magitech weapons using the ability to warp space, invoke wormholes or play with quantum effects needed to generate the FTL effect are probably some of them. (Superluminal computers or computer servers capable of doing calculations "backwards in time" and acting as oracles are probably also possible with FTL).

While Jerry Pournelle is one of my favorite authors, the CoDominium series and The Mote in God's Eye have far more of a sense of "here and now" about them because there is so little futuristic tech. (While I also recognize Pournelle did this on purpose, it still sometimes seems a bit out of place in the story setting).

Tony said...

Classical space opera used nukes on missiles, nukes fired by guns, and, towards the end, "energy beams". Nobody even knew what a laser was (because the term hadn't even been coined yet) until 1959. Aside from that, nuclear weapons were known to work, for real, in actual combat. Guess what? thousands of years from now, nuclear weapons will still work, for real, in actual combat.

Scott said...

Now there's a setting nobody's tried out, at least not explicitly: a galaxy-spanning civilization that has only a hundred -- or even a thousand -- habitable planets where people live, plus billions of places where people only go to work or study for a limited amount of time.

Actually, the Peacekeeper universe is something close to that concept. It's not been well fleshed-out in the novels, but it seriously sounds like most people live in space habs, with a large minority that live planetside. And you have the groups that live in the slowboats.

Since their FTL is dependent on slow-boats, it's not a huge setting... I think the typical slow-boat mission is ~40 years true time, although I may be mistaken. Even with a mere 1m/s/s acceleration (yes, they do have magitech drives), that gives you a 600ly reach between systems.

Scott said...

You know, it helps if you use a relativistic calculator instead of a simple brachistochrone formula.

Call it 35-40ly between FTL points in that world.

Anonymous said...

=Milo=



Keep in mind, a "galaxy-spanning civilization" with "a thousand habitable planets where people live" means that those planets average some 2000 lightyears apart.

Tony said...

Milo:

"Keep in mind, a "galaxy-spanning civilization" with "a thousand habitable planets where people live" means that those planets average some 2000 lightyears apart."

Yep. It wouldn't surprise me at all if Earthlike planets were that thinly distributed. It wouldn't surprise me if they were distributed every hundred light years or so. It would surprise me (mildly) if we found one within twenty or thirty light years of our Sun.

Thucydides said...

I think we are running into Rick's divergence problem again. What is "realistic" and what makes for exciting story telling are often two different things.

Would we be reading the Aubrey-Maturin series if 75% of the books concluded with a sea cruise where there was no contact with the enemy? How many police shows would focus on the reality that the vast majority of street cops never draw their service weapon in their entire career? Would Criminal Minds still be on TV after six years if the profiling unit was only on their second or third case?

While lasers were unknown before 1959, death rays were part of the Space Opera trope long before (as were world cracking explosives, probably even before the atomic bomb was demonstrated). If we combine the apparent reality of habitable Earth-like worlds being separated by 200+ LY with the real observation that Humans are greedy and tend to grab things if that is easier than making things, and add cheap and easy FTL then we have the background for a Space Opera setting.

After that, we can add our own assumptions and see what the result is (as long as we follow our assumptions to their logical conclusions. Sword fights in space or forgetting about drive throughs after the invention of the automobile are counter examples).

Tony said...

Thucydides:

"I think we are running into Rick's divergence problem again. What is "realistic" and what makes for exciting story telling are often two different things."

Not necessarily...

"Would we be reading the Aubrey-Maturin series if 75% of the books concluded with a sea cruise where there was no contact with the enemy?"

People that do read them -- I personally find them boringly self-absorbed, in the style of Fenimore Cooper -- know that there are historical examples that really did led almost as exciting and unlikely lives.

"How many police shows would focus on the reality that the vast majority of street cops never draw their service weapon in their entire career?"

A small minority only ever fire their weapons in the line of duty, though it's getting larger every year. Almost every cop that works the streets draws his weapon multiple times a year, for its deterrent effect.

"Would Criminal Minds still be on TV after six years if the profiling unit was only on their second or third case?"

Or NCIS?

Police procedurals fall into their own category of outlandishly unrealistic because police work is inherrently mundane most of the time. They're not really in the same calss as high romance. Maybe we should think of them as forced romance.

"While lasers were unknown before 1959, death rays were part of the Space Opera trope long before (as were world cracking explosives, probably even before the atomic bomb was demonstrated). If we combine the apparent reality of habitable Earth-like worlds being separated by 200+ LY with the real observation that Humans are greedy and tend to grab things if that is easier than making things, and add cheap and easy FTL then we have the background for a Space Opera setting."

Death rays were whatever the using author wanted them to be. They could be handheld blaster to weapons space battleships used to fight each other. It all depended on what the author needed them to be. But Heinlein, Piper, Dickson, Asimov, Harrison, and several others tended to stay away from them. Guns, missiles, HE, and nukes were for them more believable. Even when Clarke introduced energy beams in Earthlight, the ultimate weapon was still a plasma of metallic elements, projected by an electromagnetic cannon. Anderson, after lasers became public knowledge, was very careful to not overdo beam weapons, keeping nuclear warhead missiles prominent in space combat scenes.

Planetbusters, in the stories which they existed, seem to be extrapolated nuclear weapons. In Space Viking, for example, they could be purchased from any high end nuclear weapons supplier and didn't in fact bust planets -- they merely destroyed everything inside a thousand mile radius. Additionally, they supposedly used a "Bethe solar-phoenix reaction", which, in fact "was sunlight" (emphasis from the original). That shout-out to a famous contemporary nuclear weapon designer and the funtional description is highly suggestive of a weaponized nuclear phenomenon.

Having said all of that, I'm okay with any internally consistent set of assumptions. I'm actually quite fond of space opera in the classical sense, where the author doesn't try to bludgeon the reader into submission with spec-tech nonsense about how everything is supposedly possible within the real universe. Just get on with the story.

WRT beam weapons specifically, I think they're a ridiculously overdone and overutilized trope. If we can make any technical assumptions we want, I prefer mine to include things that go BANG!, whoosh, and BOOM! (In an atmosphere, of course.)

Rick said...

Quibble to the max, but Asimov definitely had beam weapons, 'blasters,' in the original Foundation books. He also mentioned atomic bombs, but less prominently.

I am a quite reluctant convert to beam primacy, and would be quite happy, aesthetically speaking, if all those things that might severely limit laser weapons actually do so.

Of course in my own setting I would be fully in my rights to make that the case. But my gut feeling is that apertures on the order of 10 meters and effective ranges over 10,000 km are practical at the techlevel that makes 'space warships' a serious proposition to begin with. (YMM obviously V.)

Tony said...

Rick:

"Quibble to the max, but Asimov definitely had beam weapons, 'blasters,' in the original Foundation books. He also mentioned atomic bombs, but less prominently."

Absolutely, but blasters seem to be exclusively small arms. With warship armament, not so much. Describing Bel Riose's war against the Foundation, in Foundation and Empire, Asimov talks of planets capitulating when their capitals were put under threat of "massive artillery". Additionally, ships being destroyed in battle by "noiseless flares" of "atomic disintegration".

"I am a quite reluctant convert to beam primacy, and would be quite happy, aesthetically speaking, if all those things that might severely limit laser weapons actually do so.

Of course in my own setting I would be fully in my rights to make that the case. But my gut feeling is that apertures on the order of 10 meters and effective ranges over 10,000 km are practical at the techlevel that makes 'space warships' a serious proposition to begin with. (YMM obviously V.)"


From what I can tell by reading this blog and its comments, the primary advocate of superpowerful lasers is himself a dedicated laser enthusiast, who has no extensive military education, much less military experience. With all due respect to his scientific and technical education, he approaches laser weapons as an isolated technical problem, without understanding the necessity of integrating them into combat capable systems.

I can see lasers occupying a niche in certain narrow defensive circumstances. But projectiles, either gun launched or carried on missiles, purely kinetic or explosive or equipped with submunitions, are just too versatile to not be primary weapons far into the future.

Tony said...

BTW, the argument, "If we have the the energy to do this, we will have the energy to do that," is a non sequitur. If you have the energy to do one thing, you have to use that energy to do that thing. If you want to d osomething else at the same time -- which you usually do in ship-to-ship combat -- you have to have other energy. For example, in a dreadnought battleship, the propulsion plant is capable of 20-160 MW of instantaneous power at full output. But the armament outfit used other energy, put in at the chemical plants that produced nitric acid for nitrocellulose propellants and TNT explosives. I'm not a chemical engineer, so I have no clue about the exact numbers, but judging by the chemical energy that these weapons released, one would have to think that it was on the megawatt-hours scale.

The same will probably apply to space warships. Lasers may seem the perfect weapon to some people, but they rely on instantaneous, on-the-spot power generation, and probably in forms that can't be generated by the propulsion plant. In high explosives we can exploit the stored energy from static power production that does not to be brought along on the mission. Additionally, with nuclear weapons, we can exploit the stored energy of a supernova, plus the stored energy of a static nuclear power plant, in the form of processed, weapons-grade fissionables.

Anonymous said...

Yes, a mix of weapons would be best; however, unless there's someone on the world of two suns that we need to fight, I don't see how we got from speculating about this odd world to space warfare. Not that this isn't an uncommon occurence on this blog...

Ferrell

Tony said...

Ferrell:

"Yes, a mix of weapons would be best; however, unless there's someone on the world of two suns that we need to fight, I don't see how we got from speculating about this odd world to space warfare. Not that this isn't an uncommon occurence on this blog..."

Kill em' all. Let the Great Attractor sort 'em out.

Rick said...

Not only is it not-uncommon - it is pretty much invariable.

Of course, I have no one to blame but myself, after writing 15 posts in the Space Warfare series, and another dozen or so (at least) that deal mainly with the topic.


I am pretty sure that Asimov also implied that blasters were major (whether or not 'primary') weapons in space battles as well. But really he said little about the space tech of the Foundation 'verse. I may have just assumed that beam weapons were implied because I took them to be space opera convention in that era.

Tony said...

Rick:

"I am pretty sure that Asimov also implied that blasters were major (whether or not 'primary') weapons in space battles as well. But really he said little about the space tech of the Foundation 'verse. I may have just assumed that beam weapons were implied because I took them to be space opera convention in that era."

I don't think death rays were a convention as much as a well-tried option.

In any case, upon further research it turns out that the text I quoted from Foundation and Empire was written in 1944 and first published in April 1945. So I guess anybody's guess is as good as anybody else's WRT what Asimov was thinking. He could have guessed, but he wouldn't have known, what nuclear weapons exploding in space would look like. But writing about "artillery" in 1944 would definitely have evoked guns firing projectiles. What kind of projectiles? Who knows? Curiouser and curiouser...

Thucydides said...

I will have to dig it out of the library, but James Blish also had beam weapons in the "Cities in Flight" series, which seem to have worked by invoking nuclear reactions in the target material...

Tony said...

Beam weapons also came with a symmetric defence -- energy shields of some type. Which eventually led Weber to invoke gravity shields, because nothing else in the real world could deflect light.

Of course, the real engineering issue here is that not only do you need more power above and beyond propulsion for you beam weapons, you need just as much or more power for shields. I think i'll just hang back and toss kinetics at you until your heat rejection system overloads.

Stevo Darkly said...

@Thucydides:
I will have to dig it out of the library, but James Blish also had beam weapons in the "Cities in Flight" series, which seem to have worked by invoking nuclear reactions in the target material...


Yes, that was the "Bethe blaster." It was a beam that somehow initiated a fusion explosion (I think Blish did say a "thermonuclear explosion" specifically) in whatever sort of matter composed its target.

Also, the Bethe blaster couldn't be used when "adjacent to a planetary surface." I assume that's because the beam would create a fusion explosion as soon as it hit the surrounding atmosphere (if there was one). Or perhaps the beam "leaked sideways" enough that it would interact with the planetary surface it was resting upon -- in either case destroying the shooter before the beams could reach the intended target.

Also if I recall correctly, NYC didn't carry Bethe blasters itself, but warships might, or heavily armed and belligerent cities such as the killer bindlestiff that our heroes encounter in the Rift.

And that's all I can remember offhand. But I did read and reread Blish's Earthman, Come Home about eleventy-zillion times, and my memory for written material is fairly good. (I liked the other books in the serious, but not as much, so I only read them half a zillion times.)

-- Not a new commenter; I read here almost every day but don't have much time to post lately.

Stevo Darkly said...

Oh ... and the Cities in Flight novels also mentioned "mesotron rifles," which I presume were some kind of particle beam weapon. Blish didn't really describe how they worked; I only recall that someone fired one at Mayor Amalfi and missed, hitting the stone cornice of a building instead and turning it glowing hot.

Mesotron rifles could be handheld arms or mounted on a ship or flying city. They were a lot less destructive than Bethe blastes, and used as tools at least as much as they were military weapons. I think at one point they are used to drill holes in rock or something, and NYC carries some on its underside to clear out a landing zone (as when landing amid trees).

Rick said...

It is striking that in contrast to the ever popular purple/green debate about lasers v kinetics as weapons, force shields have been pretty much deprecated in hard SF since the golden age.

Yes, Weber, but I'd argue that Honor Harrington's claim to be 'hard' SF is fairly tenuous. Napoleonic Wars in SPAAACE !!! after all!

Tony said...

Rick:

"...the ever popular purple/green debate about lasers v kinetics as weapons..."

The debate is more than a little bit artificial, however. It juxtaposes lasers with unguided, monolithic (in terms of structure, not necessarily size) ballistics. The problem is that the material can include guided ballistics, guided missiles under power, explosive warheads, and the ability to shoot over the horizon (and there will be horizons in space, both temporal and physical). That capability template, if intelligently applied, makes lasers look pretty anemic, no matter how superior they may seem under ideal conditions.

Rick said...

I've always taken the kinetics side - whichever color that is - to be guided target seekers, or at least shrapnel frags of target seekers. (I now think that guided submunis are more effective than bus fragments, but that is a secondary detail.)

At a spherical-cow level of analysis, I assume that kinetics will always hit a target within their maneuver envelope unless actively engaged and 'shot down.'

Thucydides said...

In the "real" PMF, ships will have both types of weaponry, since they compliment each other.

Ships might still be divided into Laserstar and Kineticstar categories (I doubt any Navy will want to designate their ships as "Purple" or "Green", much less "War Cows") depending on what the primary mode of the ship is; one can imagine in Jovian space the IJN "Luke" has a massive spinal LINIAC for its gigawatt Xaser and batteries of missile launchers attached to the trusswork; while off in the orbit of Uranus the USN "Tony"'s barrel shaped hull is packed with missiles, but clusters of mirrors dot the ship for the short range defense lasers...

Tony said...

IMO there's no percentage in using lasers for any military purpose. They're too high precision and prone to failure. If you have a central beam generator, they also become a single point failure mode. One of the reasons I like missiles and guns is that all of the mounts or launch box clusters are discrete units. A casualty in any one does not effect any of the others. Also, missiles or gun projectiles are discrete rounds of ammunition. A failure of one does not mean a failure of any others. Finally, with kinetics, a ship itself can be used as the delivery system, by using its own drives to put ballistic bombs or KKVs on their attack trajectories.

Anonymous said...

=Milo=



Thucydides:

"I doubt any Navy will want to designate their ships as "Purple" or "Green", much less "War Cows""

The military's bureaucracy and higher-ups? No. Irreverent nicknames by the soldiers themselves? Easily.

Anonymous said...

Milo said:
"The military's bureaucracy and higher-ups? No. Irreverent nicknames by the soldiers themselves? Easily."

I totally agree with you, Milo.

Ferrell

Scott said...

I dunno, Tony. We've weaponized FELs and Chem-lasers down to smallish individual installations that either would replace a (rather small) deck gun (Boeing ABL) or flatout augment a bolt-on system (the laser Phalanx). Those systems aren't powerful enough by my standards, but they could be developed into something with that kind of power in the future.

I do agree that the probability of a major warship mounting a single laser-generator is a number virtually identical to zero. Note that the Jovian Chronicles ships with spinal lasers typically have 3 generators.

Rick said...

I agree with Milo and Ferrell - 'war cows' is just the sort of term that would never be official, but that I could see catching on with the troops.


IMO there's no percentage in using lasers for any military purpose.

That's quite a hard line position!

I can see I'm gonna have to revisit this topic. (Always a good way to pimp for traffic, too!)

Short form, I see the trade-offs as having to do with overall technical balance, and particular requirements on the other.

Classic nuclear electric propulsion, IMHO, favors laser armament because you've already got beaucoup electrical power, plus radiators and so forth. So all you need is the laser (bank) and targeting optics. At the same time, this propulsion is too sluggish for much tactical oomph.

On the other hand, orbital combat with chemfuel or nuke thermal propulsion favors kinetics because there is no handy built-in power supply for lasers, and the combination of high accelerations and strong gravity fields makes it fairly easy to deploy fast kinetics.

Tony said...

Scott:

"I dunno, Tony. We've weaponized FELs and Chem-lasers down to smallish individual installations..."

Rick:

That's quite a hard line position!

Please allow me to revisit an observation I've made about technology before, but with a slightly different twist. The observation is that technologies mature.

The different twist I want to put on it is that we live in an age of rapidly and decisively maturing technologies. For the purpose of the point I want to make, let's say that a mature technology is one where one of its artifacts can find practical use fifty years after it was first perfected. For example, though it is not the latest in bleeding edge weapons technology, a German StG 44 assault rifle could still serve as an assault rifle today. So we could say that assault rifles matured for all practical purposes in 1944. For another example, the R-7 launch vehicle first put a satellite into orbit in 1957. It put another one in orbit today.

Okay? Technologies do mature to the point that only margnial improvements can be made. Heck, a hammer's been a hammer for, like, ever.

But let's take a step back and realize that these days, with all of the super-insta-rapid communications, and cross-polinations, and synergisticizing, technologies mature really quickly. Taking the above example 100 years before the StG 44, the average infantryman carried a muzzle-loading smoothbore, onto which they had just introduced the percussion cap lock. 30 years before the R-7, Robert Goddard had just barely invented the liquid fueld rocket.

So, what am I saying here? Well...maybe lasers are just never going to be all that. Maybe we've really pretty much plumbed their depths. We won't know whether we have or haven't for several decades, but based on the recent history of engineering technologies, I think maybe -- just ma-a-aybe -- we have.

Anonymous said...

=Milo=



Rick:

"Classic nuclear electric propulsion, IMHO, favors laser armament because you've already got beaucoup electrical power, plus radiators and so forth. So all you need is the laser (bank) and targeting optics. At the same time, this propulsion is too sluggish for much tactical oomph.

On the other hand, orbital combat with chemfuel or nuke thermal propulsion favors kinetics because there is no handy built-in power supply for lasers, and the combination of high accelerations and strong gravity fields makes it fairly easy to deploy fast kinetics."


I disagree when it comes to nuclear-thermal - bimodal nuclear-thermal engines can be made, and while less efficient than power plants designed exclusively for electricity production, they should be pretty good for laser purposes.

I do, though, conceptually appreciate the idea of different weapons being optimal in different tactical environments, and getting to use both lasers and kinetics.

Thucydides said...

I would not count out lasers quite so easily. The on again/off again R&D effort may have made it seem like lasers have taken 50 years to mature, but in reality, many programs were stopped in the 1980's at the end of the Strategic Defense Initiative, and newer programs start and stop as well. The US Navy had funding cut to both laser weapons and electromagnetic railguns, despite having demonstrated excellent test results. The USAF's airborne laser efforts are hitting a similar "wall" despite successful tests as well.

Short bursts of effort followed by longer funding lulls, and the inevitable "reinventing of the wheel" as programs are restarted or new programs pick up where old programs ended suggest to me that high power lasers are really about halfway to maturity.

New ideas, like ganging high efficiency diode lasers (Lasermotive) are appearing all the time, so I think we could be in for some surprises. (Perhaps the biggest surprise may be which nation fields the first viable tactical lasers...)

Anyway, the argument is a bit moot, lasers and kinetics are complimentary, and the decision by Fleet HQ will be deciding what proportion of laser to kinetic will be used, and how that will be balanced across ship classes and the fleet as a whole. Factors such as nuclear electric or nuclear thermal will be a big factor in guiding the decision.

Rick said...

I would side with Thucydides in this case. Military lasers have not been pursued with any great consistency. Even more to the point, there has been rather little effort put into space-to-space weapons in general, for strategic rather than technological reasons.

Also note that there have been some very major developments in optics in the last 25-odd years. Much larger telescopes, adaptive optics, and so on.

Tony said...

I evaluate it this way:

Lasers have been adapted to every possible application over the last fifty years. Who in 1960 would have predicted fiber optics or CDs, for example. If lasers haven't been adapted into weapons, it seems to me that, in this age of rapid technological development, it's a reasonable question to ask if they can be.

And in all honesty, I really don't see where it has been demonstrated that they will ever be practical as weapons. They've been shown to work technically. But they haven't been shown to be practical. And the limit to practicality (for rail guns as well, BTW) is the portability and reliability of a combat power supply. Even in shipboard applications, it turns out that one would have to add large and heavy auxiliary generators, plus their cooling systems and fuel supply, because you can't use propulsion power for weapons.

As I have stated before, this last is something that people seem to be systematically missing about space lasers -- just because you have propulsion power, that doesn't mean you have beam weapons power. That takes other power. The big attraction to guns, missiles, and explosive warheads is that all of the energy they use is put in by commercial power plants that don't have to be brought along on the mission.

Simply put, I just don't think lasers will ever achieve the level of practicality to be even complimentary weapons.

Tony said...

I wanted to add: Beam weapons, laser or otherwise, are something we hold close because they are right at the center of long cherished canon. But like the family nuclear interplanetary rocket, or the geosynchronous Earthport One space station, they may just be another thing that reality has overtaken. In fact, given the way reality has overtaken much of the rocketpunk canon, it seems to me to be somewhat quixotic to hold onto beam weapons so dearly.

Rick said...

Meta note that it is very odd to be defending a weapon tech that I don't particularly like on 'aesthetic' grounds, and certainly have no SF-sentimental attachment to!

Note also that I'm not arguing for laser small arms, field artillery, naval guns, or whatever - my interest in laser weapons is strictly as a long range space weapon.

just because you have propulsion power, that doesn't mean you have beam weapons power

For most propulsion systems I would agree, but nuclear (or solar) electric space propulsion seems to be a notable exception. Electric spacecraft have available onboard power equal to their thrust power, with radiators capable of shedding the waste heat. And their milligee acceleration is so modest as to be pretty much irrelevant to tactical maneuver.

So a nuke electric ship loses nothing by diverting its full electric output to a laser (bank), even for an hour or more of steady zapping.

A few provisos, from technical to rather meta:

1) While the main radiators can shed the waste heat, the cooling system that takes heat from the laser to the radiators may well be so noisy as to produce excessive beam jitter. This topic is pretty deep into the technical weeds.

2) A case an be made that the techlevel of milligee electric drives is not conducive to the sort of warfare in which laserstars would have any mission. (Such as combat between terrestrial powers in Earth orbital space.)

3) More futuristic/speculative electric drives have different characteristics. A torch-level drive almost certainly does NOT have plug power equal to anything like its (outrageous) thrust power.

Anonymous said...

Perhaps the best use of space lasers would be as point defense weapons; short range and either causing the seeker heads to be 'pulled' off target, or generating a jet of super-heated gas that knocks the projectile off course. Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons.

Ferrell

Anonymous said...

=Milo=



Ferrell:

"Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons."

Well, we're looking into laser communication today. They could be used against asteroids. I guess lasers could have scientific uses for vaporizing samples. Or you could just bounce them off something to measure its distance.

But a laser designed for communication is going to work very differently from one designed as a weapon. They aren't interchangeable.

Of course, ships will have numerous micro-lasers onboard for a variety of purposes, such as in the DVD reader for playing the in-flight movie, but no-one is actually going to count those as ship-mounted lasers.

Tony said...

Rick:

"So a nuke electric ship loses nothing by diverting its full electric output to a laser (bank), even for an hour or more of steady zapping."

Stay outside of zapping range and attack it with small, hard-to-hit, unguided kinetics until the radiators are shredded. It's not like the ship will be maneuvering to complicate the targetting. If the ship elects to maneuver, because it doesn't have other ships to shoot at, it becomes a better target for guided kinetics that it can't shoot at while maneuvering.

This is one of the big reasons lasers just strike me as way oversold and unlikely to be viable. They just represent a ridiculous vulnerability in the form of large and fragile power systems. Or if you choose to use consumable power generation and cooling, well, they're just another gun.

Tony said...

Ferrell:

"Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons."

Lasers as a class are very versatile. Individual lasers are extremely limited, since they have to be optimized for operating frequency and power output.

Rick said...

Stay outside of zapping range and attack it with small, hard-to-hit, unguided kinetics until the radiators are shredded.

That is a pretty easy tactic to defeat. I don't have what I think of as 'tactical maneuvering power' (e.g. to choose the time and place of engagement). But I surely have chemfuel thrusters good for dozens of meters per second.

And I'll have a approximate idea of viable trajectories, because the kinetics have to be launched from a ships/missiles on a collision course. I only need to sidestep by a few hundred meters to render non-guided kinetics ineffective.

Also, for most geometries I can position myself so that my radiators are end-on to your attack, minimizing cross section (and making a Whipple shield a worthwhile investment).

You could theoretically defeat these defensive measures by engaging me simultaneously along widely separated axes. But that is VERY hard to arrange unless I am totally asleep at the switch.

Tony said...

Chemical attitude control thrusters used for maneuvering is a pretty limited resource. You can't just burn all of your attitude control juice, even in survival mode. You'll need it later. I doubt it would be smart to use them except to face your shielding/armor in the appropriate direction.

Also, you really can't point your shielding armor in the direction of the attack, unless it's coming from up or down orbit (WRT your orbit). The smart attacker will arrange his salvo so that it intersects your orbit from an off angle. With careful timing he can have an attack arrive over a pretty wide sector, maybe 50-60%.

Rick said...

If I don't have ~100 m/s of OMS delta v available I have no business zapping people, and ought to work on mutual understanding through dialogue.

That gives me 10 evasion burns at 10 m/s.

And bear in mind that even with pretty conservative assumptions my zapping range is impressive. Suppose that my main mirror performance is degraded by 90 percent, i.e. my 10 meter main mirror delivers the spot size of an ideal 1 meter mirror.

If I am zapping at 1200 nm in the IR, my spot size is 1.83 m at 2500 km. With 100 MW average power, I can burn through various armor materials at rates on order of 1 cm/minute - and keep on zapping more or less as long as I can hold down the trigger.

Remember that this is with a range degradation of 90 percent - comparable to the difference between the bench range of an assault rifle and typical firefight range.

At this sort of range, flight time of kinetics will be hundreds of seconds, and getting more than a few degrees of spread would be problematic.

Tony said...

Rick:

"If I don't have ~100 m/s of OMS delta v available I have no business zapping people, and ought to work on mutual understanding through dialogue."

If you have 100 m/sec of attitude control available, that's becaue you need it for attitude control. If you have extra margin for jinking, it's because you skimped somewhere else. Tell me what you traded off, and let's see if I can't exploit it.

Also, if you jink in orbit, you have to reestablish your orbit after the fighting's done (presuming you're still around). Whether you do that with your electric motors or with your attitude thrusters, you still gotta carry extra remass for that eventuality too.

"At this sort of range, flight time of kinetics will be hundreds of seconds, and getting more than a few degrees of spread would be problematic."

The flight time is almost immaterial. The projectiles, if unguided, are going to be golf ball sized at largest, but probably more like marbles, and number in the thousands. If you can engage enough of them to avoid getting hit, be my guest. I don't think you can.

WRT dispersion, we have to remember that we're operating in three dimensions. My solution to your shielding is to give my attack depth in three dimensions. When the orbits of the attack and your ship intersect, some projectiles may in fact be absorbed by your shielding, but unshielded parts of your ship facing in the direction of your orbit will run into projectiles as they pass by.

Or I can be a little more efficient and arrange for depth in time, so that the first attack hit's you from off orbit, while the second one you run into because it's timed for you to run into it, instead of it running into you. Or variations of this theme. The problem you're faced with is that you can't re-orient your shielding that quickly.

Or, borrowing from emerging (in 2011, not SFnal) AFV point defense technologies, I don't worry about the particular aspect of attack, I wave the dumb kinetics and have my attackers shoot EFPs at you on the way by. Surely a few of them will hit from an unshielded angle.

That's kind of my whole point -- lasers are good for shooting at something along a straight line. Kinetics and chemical energy explosives can be made to do all sorts of fun things to screw up the best laid plans of lasermen.

jollyreaper said...


So, what am I saying here? Well...maybe lasers are just never going to be all that. Maybe we've really pretty much plumbed their depths. We won't know whether we have or haven't for several decades, but based on the recent history of engineering technologies, I think maybe -- just ma-a-aybe -- we have.


That's possible. On the other hand, how far would aeronautics have gone if the European powers were able to settle their differences peacefully in 1914? If R&D was only paid for by private concerns and not public money, it's not inconceivable that we could still be looking at piston and prop aircraft even now.

While not wanting to get into a tech stagnation debate, it does seem to be the case that each development requires more people and more research and more money but how much of this is driven strictly by the requirements of the task at hand and how much is bureaucratic inertia? I have no idea.

I'm pretty agnostic on the whole idea. I won't say for sure whether X is possible or X is impossible, I'm simply prepared to see it go either way or just muddle along kicking the answer-can down the road.

Tony said...

jollyreaper:

"That's possible. On the other hand, how far would aeronautics have gone if the European powers were able to settle their differences peacefully in 1914? If R&D was only paid for by private concerns and not public money, it's not inconceivable that we could still be looking at piston and prop aircraft even now."

By 1909, all major governments in Europe and the US were already financing aviation development. Planes were first used for bombing in 1911 (by the Italians in the Italo-Turkish War). Many advances were also made between the wars. Many more advances were made after WWII. Wartime accelerates things somewhat, but the fact is that anything with even marginal military utility is developed to its maximum extent, with or without war.

Rick said...

If you have extra margin for jinking, it's because you skimped somewhere else. Tell me what you traded off, and let's see if I can't exploit it.

That's true of every military capability, and the penalty for this one is a few percent of combat mass. What did you sacrifice to carry those marbles you're tossing at me?

The flight time is almost immaterial.

Huh? These are unguided projectiles - the longer the flight time, the longer my jink time, and the less delta v I need to cover whatever deflect radius I estimate to be enough to make a hit difficult.

How do you propose to give your attack 'depth in three dimensions?' Your grapeshot has to be deployed from ships or missiles that are basically easy to track - I will know hours in advance what the threat vectors are.

Things get different in low orbit, but that is no place to take a laserstar anyway; they are intended for more open space - say, geosynch and beyond. (If there's no reason to fight out there, I wouldn't build laserstars.)

I wave the dumb kinetics and have my attackers shoot EFPs at you on the way by.

Did you mean 'waive'? Or am I missing something?

In any case, this is basically a target seeker, since it needs to be oriented the right way and set off at the right time in order to hit. I'll engage them as I would any other target seeker.

I'm not claiming that such an attack can't throw me off, just as the German torpedo attack at Jutland threw off the Grand Fleet and allowed the HSF to bail.

Tony said...

Rick:

"That's true of every military capability, and the penalty for this one is a few percent of combat mass. What did you sacrifice to carry those marbles you're tossing at me?"

Just so. I was simply forestalling one of those well-then-I-pull-out-my-vorpal-blade-that-goes-snicker-snack type arguments by pointing out that there are limits.

"Huh? These are unguided projectiles - the longer the flight time, the longer my jink time, and the less delta v I need to cover whatever deflect radius I estimate to be enough to make a hit difficult."

It's like any other long range gunnery exercise. A dodging target is just part of the problem. I only have to hit you a few times out of several thousand projectiles.

"How do you propose to give your attack 'depth in three dimensions?' Your grapeshot has to be deployed from ships or missiles that are basically easy to track - I will know hours in advance what the threat vectors are."

Certainly you will. But with proper timing I can have attacks arriving within a few seconds of each other from different directions, so that you simply can't re-orient your shielding quickly enough.

"Did you mean 'waive'? Or am I missing something?

In any case, this is basically a target seeker, since it needs to be oriented the right way and set off at the right time in order to hit. I'll engage them as I would any other target seeker."


They're not quite like any other target seeker. They wouldn't maneuver, so they wouldn't have to be much bigger than the warhead, a sensor-control package, and a small attitude thruster plus about a second of remass. (You only need one attitude jet because you spin the projectile on launch.)

"I'm not claiming that such an attack can't throw me off, just as the German torpedo attack at Jutland threw off the Grand Fleet and allowed the HSF to bail."

Oh, it's intended to do much more than throw you off.

Thucydides said...

I seem to recall that one thread here (or was it Atomic Rockets?) actually tried to work out the mathematical relationship between incoming warheads and laser weapons of "stupendous power".

My Google Fu seems weak today, but the magnitude of kinetic vs WSP laser was in the order of thousands of warheads needed to be launched to ensure overmatch against a single laser weapon. I suppose it would be fair to ask Tony what his ship is giving up to operate as a huge missile carrier?

Indeed, the tradeoff would seem to be favouring size; Luke Campbell's Xaser with its kilometer long LINIAC would be a large and robust ship (the optical train would have to be held in a massive truss, with power and cooling units mounted on vibration isolating "rafts"). This would be more than sufficient space to mount hundreds of VL cells carrying the thousands of missiles desired.

Even smaller ships would still be large in our terms; there is a proposal for a megawatt class FEL capable of fitting into a 747 (much like the ABL, but a tunable, electric weapon rather than a chemical laser). This implies the smallest spacecraft capable of fighting with a laser weapon would be at least as large as a 747, and probably much larger once the reactor, tankage and so on were added; plenty of room for missile batteries as well.

Tony said...

Re: Thucydides

That's kind of how I figured it -- lasers with thousands or tens of thousands of kilometers of effective range are prohibitively large, expensive, and nowhere near as effective as the armchair admirals imagine.

The spin on the EFP projectile isn't to provide any kind of laser energy resistance. The device is only going to be about the size of a modern antitank missile, maybe smaller. If it gets hit, it gets hit all over. The point of the spin is to minimize attitude control system mass. With a spinning object, any attitude change WRT the spin axis can be accomplished with a couple of burns of a single thruster, providing that thruster is acting along a vector that doesn't pass through the object's CG.

Rick said...

Thucydides, the thread you're thinking of was Further Battles of the Spherical War Cows.

The ships I have in mind are big, but not humongous - on order of 1000 tons departure mass, 500 tons dry mass, perhaps 200 tons gross payload, give or take.

If you are fighting demi-operatic deep space wars at all, you should be able to afford capital ships on this scale, whatever armament you choose to provide.


Also bear in mind that the 'ideal' spherical-cow laserstar is a conceptual exercise, not a service proposal. I can see a 'monitor' vehicle - designed purely to defend a planet's orbital space against intruders from Somewhere Else - coming fairly close.

But my mental image of an expeditionary 'capital ship' is something on the lines of one keel-mounted main mirror, a couple of secondary mirrors (port/starboard or dorsal/ventral, the distinction being arbitrary), and payload capacity for kinetics, 'gunships,' or whatever.

Tony said...

Rick:

"But my mental image of an expeditionary 'capital ship' is something on the lines of one keel-mounted main mirror, a couple of secondary mirrors (port/starboard or dorsal/ventral, the distinction being arbitrary), and payload capacity for kinetics, 'gunships,' or whatever."

As I've stated before, space warships are likely to resemble fighter-bombers than they are to be like dreadnought battleships. So I have serious doubts about the subordination of everything to a spine mounted weapon system. And even as secondary or co-primary weapons, lasers are too narrow in application.

Anonymous said...

OK, my posts lately have been hit-or-miss, but here goes...My opinion of space warfare is that it will be dominated by either orbital combat or high speed fly-by intercepts. Most combat spacecraft will probably mount a mix of weapons; lasers, missiles, and ballistics; each will cover the other's weak points and concentrate on their strengths. Versitility is very important to millitary success, no matter what the battlefield is. The only other space combat mission is likely to be convoy escort/attack, but that would likely blur into the other two.

Ferrell

jollyreaper said...

OK, my posts lately have been hit-or-miss, but here goes..

HIT! You sunk my space battleship!

Rick said...

LOL