Stuff about space. This is post 515, which is 103 × 5.
- I redid that thought experiment about a fusion-rocket Blackbird—I was able to find more specific information about its mass-ratio. It turns out, an SR-71 Blackbird weighs 60,000 pounds without fuel, and its fuel weighs 84,180 pounds. That means it has a mass ratio of 2.364. If you built a magnetic-confinement fusion ship with that mass ratio, it'd get you up to 1.17% of the speed of light (assuming you like to stop at the end). And if your rocket engine is the same size as the Blackbird's (9 times as massive as the minimum size for an MC fusion engine), you get 168,750 newtons thrust. Unfortunately that can only accelerate a fully-loaded Blackbird at 5.35 m/s2, which comes to .545 g's.
- Two other changes occasioned by my spin-gravity research. First, I think I might make the human "space fighters" (which are really parasite missile-ships launched from a mother ship) more like Orion-type ships, rather than the long skinny dragonfly-shaped design of most human ships. They'll probably replace the "big steel wall" pusher-plate with a magnetic field, though, proton-chain fusion involves a hell of a lot more energy than a hydrogen bomb. This lets them be a lot smaller than even the smallest Orion ship, since a major portion of the mass of those is the pusher-plate.
Second, I'll need to figure out how to describe the distortions created, in the topology-sensors the zledo use, by artificial-gravity inertial protection (they bleed the force of accelerations into the surrounding space-time). I think, if they accelerate at 8 gs, their ship, or part of it, would seem to stretch eight-fold in the opposite direction. It occurs to me whenever I posit a technology like this, to worry about the environmental impacts—but there's plenty of asteroids thousands of times bigger than any ship, and the gravitational perturbations they cause are infinitesimal.
- One of the articles I read about cats in free-fall had numberless comments (I think because it was a British site—maybe even a Daily Mail article?) about how "cruel" that was, and how if you want to study the effects of free-fall, you should study it on humans (yes, they ignored the fact there were humans free-falling right there with the cats—it was on the Vomit Comet, they didn't just turn the gravity off for the cats without becoming weightless themselves). But the point of studying free-fall's effects on cats is, humans do not have that kind of righting instinct. Cats do. You can no more use humans to study how that righting reflex works in free-fall than you can use them to study tails or retractable claws.
Come to think of it, it was definitely a Daily Mail article; one of the other commenters was some idiot identifying the blatant, obvious, familiar-to-anyone-who's-seen-I Dream of Jeannie 1960s USAF uniforms as Soviet Army uniforms, and saying that this "inaccuracy" showed the Mail was making the whole story up. But, uh, mate? Aside from how, whoever did the film, there's free-falling cats clearly shown, 1960s Soviet uniforms were olive drab (Army) or black (Navy), not blue, and outside the Navy they had Sam Browne belts, with the shoulder strap, up till at least the Afghan war. They also had "peaked" hats (as your distorted, decadent dialect calls 'em, for no reason—a "peaked" hat would be pointed, if you mean "beaked" maybe you should say it), known in the civilized world as combination caps. The guys in the video in question were wearing "side caps", AKA garrison caps, AKA "flight caps", because they were freaking USAF officers. It's practically impossible to get the two confused, without actual effort.
- Been looking into SSTO vehicles. When I switched it so none of my ships landed, I decided the Japanese guy's ship used an SSTO entry-vehicle as its habitat section—which, I find, is something that ought to be known as the "Kankômaru" type. The dimensions of mine are a bit different—it's smaller, and has several actual cabins, rather than an airline-type "theater seating" setup—but the principle is the same. I find the same thing was proposed by Chrysler in 1971, as the SERV ("Single-stage Earth-orbital Reusable Vehicle", which says "SSEORV" to me but whatever). The SERV was actually put forward as an alternate to the Space Shuttle. And not picked. Somehow.
There's also the SASSTO ("Saturn Application Single-Stage to Orbit"), by Douglas, from NINETEEN SIXTY-SIX—it was claimed to be derived from Saturn rockets but basically the only way that's true is it could launch from the same facilities. From the same company, a quarter century later, we get the Delta Clipper, which in its final form as the DC-Y was supposed to be commercial spaceflight like grownups would have, with spaceports throughout the country and flights regulated by the FAA. Not to be, sadly.
- SSTO ships are interesting, because they are ships with extremely high mass ratios and yet they accelerate at very high rates. The DC-I (an intermediate form of Delta Clipper, from the study) would accelerate at 11.34 m/s2, with a mass ratio of 13.05; a SASSTO would accelerate at 12.59 m/s2, with a mass ratio of 14.68; the SERV has 12.64 m/s2 and a mass ratio of 9. These are ships that land, too; you could almost certainly push the mass ratio even higher in vacuum. So, why, exactly, are we always being told to keep our mass ratios under 5 or 6 or so? Significantly higher ones can be sustained. Of course, there may be other reasons not to use that kind of mass ratio. I don't use it in my books (I go with the "under 5 or 6 or so" one) because the speeds my ships need, due to the time-frames involved, require proton-chain fusion rockets. And with a proton-chain fusion rocket, even a SERV's mass ratio of 9 gives you a cruising speed of 10.99% c! Sure, that gets you where you're going faster—but you have to circle the block a couple times to slow down.
A back of the envelope calculation suggests the SERV's 12 toroidal aerospike engines probably massed 1400 kilos each, while each of its 28 turbojets could've massed a mere 320 kilos. That means that of its 226,757 and 1/3 kilo (dry) mass, 25,760 kilos is engine; if we assume a proton chain fusion rocket has performance on par with an Orion rocket, in terms of acceleration ("1 meganewton per megagram" optimum), then, even with the same mass of engine as a SERV, the ship would take over 30 days to get up to speed or drop down from it, and it also needs 574.87 AUs to do it. In other words, if the ship is at the mean orbital difference of Pluto? It has to circle the Solar System two and a third times to slow down. (At the current mass ratio, an engine like the SERV's—but twice as big, because that's the mass-ratio I use, 9/2 instead of 9—would only need 10.34 days to accelerate, but it'd still also need to circle the sun once partway between Uranus and Neptune's orbits, to accelerate to or from typical orbital speed for an Earth-sized planet.)
See? Acceleration vs. delta-v is an essentially unsolvable conflict in spaceship engines. Whatever time you save increasing your Δv, you might well lose it back in the time it takes your engine to accelerate to that speed. Obviously, this doesn't matter for long-haul interstellar flights taking decades or centuries, where days, weeks, months or even years of acceleration make up a small component of the total time—but when your setting includes FTL it feels very inelegant for starting and stopping to be the longest part of any space-journey.
- There is an idea in speculations about space-colonization, called the "Three Generation Rule", namely that the kind of discipline necessary to maintain a space habitat for longer than three generations, is beyond the grasp of "normal" human cultures. But...nobody Western or Westernized has a normal human culture. For the last nineteen and a half centuries or so, you've been involved in a mystical movement that tells you it's okay to relax, you can just worry about what you can fix, nobody blames you if you didn't mean to—your apologies actually mean something—and similar purely religious propositions. (Large portions of Asia have had this too, to a lesser degree but half a millennium longer.)
Honestly, get off the reservations built for you by Christ and Buddha; at least look at the world through the eyes of an Orthodox Jew or a conservative Hindu. Better, go find some Neolithic subsistence-agriculturalist who lives in abject terror of saying or doing the wrong thing, intentionally or not, and ruining his luck. The Navajo are a good choice, there's a quarter million of 'em and their purity-code's been extensively studied. Traditionally, they will not build with driftwood or look at corpses or let dogs in their houses during storms or be in the same room as snakes or speak of the dead or dance with someone who has the same surname as any of their grandparents or play "cat's cradle" outside of winter; they live in one of two kinds of shelters, which they switch between at set points during the year, and they build them according to a strict geomantic formula and with every component strictly determined by ritual laws. That about the kind of discipline necessary to maintain a space-habitat? Well good news, everybody, that is "normal", historically and, even now, statistically, for the human race. Maybe that mindset can't build rockets—but they can definitely crew and maintain 'em, better than your precious "freedom-loving" Belters ever could.
Alternatively, the fact that you need to adopt a Neolithic purity-code mindset to safely maintain a space-habitat, might be an excellent justification to have future space-colonies, in defiance of Tsiolkovsky, Heppenheimer, O'Neill, Niven, and all the rest, living primarily on planets, rather than in artificial habitats. Because no sane person, having been freed from the purity-code, voluntarily goes back to it—it's just too much damn trouble. That's why "neo-pagans" have about as much in common with historical paganism as William Stukely.
- The "4% a year" number, considered to be the likely rate of increase of the population of space, is also the average of the growth of Australia's non-aboriginal population since 1787. It's harder to track the population of the Americas, since the English colonies didn't have extensive censusing and there's no legitimate reason to restrict the French or Spanish ones to non-aboriginals—but it's practically impossible to track all the Indians' populations (plus, you get negative growth, thanks to epidemics). The peculiar character of Australia's colonial history makes it a more convenient model of space-colonization, in quite a lot of ways—not only are the numbers easier to find but the actual setup of the Australian colony was more like what you'd see in space, than any of the New World colonizations (or Africa, for that matter).
- I have a feeling that, given the average hydrogen atom in a star survives for millions of years before ever undergoing fusion, the proton-chain fusion rockets in my books are probably actually catalyzed by the CNO cycle, as Bussard recommended for his eponymous ramjets. Only my rocket engines do not simply slam the stuff they're fusing into a funnel at relativistic speed, they compress it with a combination of magnetic fields and an application of the direct topological gravity-control. I think, thus, that the full name of the system would be "CNO-catalyzed topological confinement proton chain fusion". I think they just call it "proton-chain fusion" rather than, say, CCTCPCF, or (with some liberal sprinkling of hyphens and a liberal interpretation of "hyphenatin makes it one word instead of two") CTPF.