wumpus

Infinite acceleration (of a rocket) implies emission of infinite momentum in the other direction (conservation of momentum and such). If you want to read how that works in a story, try L. E. Modesitt Jr. at least the early sci-fi stuff. Mostly Ecolitan, maybe Timegod. He moved on to mostly fantasy and mostly moved on from the terrorist/war crime apologia (it is a lot easier to accurately justify ramming a planet at nearly light speed when an all-knowing author is feeding you information).

Engineering games? I.e. anything by Zachtronics (seen in various Scott Manley videos. I'm partial to TIS-100, the assembly language programming game, although I didn't play it all that long). Various bridge building games. Construct a vehicle and operate it? Simple planes is KSP in the air. BeamNG appears to be KSP in cars (buy Automation for a career mode). The floating point issues are that Unity uses single precision numbers for all calculations. Few things on Earth need more (which becomes a problem for KSP). "Floats" (not "doubles") give 32 bit values. This gives you values from 10-38 to 1038 which isn't a problem. Unfortunately, it also only gives you 7 decimal places or so of precision. And while you might have learned that was more than enough "significant" digits for hand calculation, repeating hammering keeps adding random error from the rounding. And as those errors get more and more significant, they creep into the the values. Try doing FFTs on audio (<16 bits, more if you are using samples outside of the "loudness war" era) with 23 bits of significance with 32k points or more to see what I mean. Using "doubles", which have entirely replaced floats for nearly all scientific use outside of strictly DSP work, should easily be enough. Granted, sometimes in astronomy you might need even higher exponents (but not precision), but that is more for extra-galactic calculations. I'd also assume that replacing the Unity physics engine would mean switching to Unreal graphics engine, and I'm not sure extremely accurately modeled kerbals would work as well.

Except that to reach those conclusion it seems they didn't stop at "go meatless", but had to remove dairy and eggs. Why kill the chicken that gives nearly 100% protein eggs? Why eliminate dairy? I'll admit that huge chunks of the world population* can't enjoy [much] dairy after infancy, but it is an extremely useful food supply that is continually produced by the cow, instead of a one shot harvest (cue vegans pointing out that you typically wind up with more calves than you want milchcows. But that really isn't an environmental issue, and could easily contribute to low level meat production). * Is cheese really that prevalent in authentic Mexican cuisine? I don't think purely Spanish genes would be enough to spread lactose tolerance across the nation like that. Or is that level of cheese merely for gringos (and possibly rich Mexicans, also likely to be more Spanish than typical)?

The planets are much smaller (Kerbin is 10% the size of Earth, and the rest are scaled to Kerbin). My guess is if you scaled the moons down as much, you wouldn't be able to find them (especially Mar's moons), so they are likely much closer to reality. So the bump thanks to Jupiter is huge (it will get you out of the solar system), while the bump from the Moons isn't so hot (I don't think NASA uses lunar gravity assists, even though they use multiple assists of various planets for a single mission). I'm also reasonably sure that no gravity assist from a Galilean moon will get you anywhere near Jupiter escape velocity. The gravitational field of Jupiter is huge. PS: I think clipping on lithobraking brakes most of the point of RSS.

A lot of the smoke plume from the SRBs has to do with the chemicals being burnt and the large leftover particles. Certainly the thrust has a lot to do with it: you can't see the exhaust of a SSME, but you certainly can see the white-hot plume of a Delta III (both hydrolox), but SRBs tend to have stuff that doesn't necessarily turn into gas. Some of this is likely similar to changing the color of the plum via oxidizing chemicals, like coloring fireworks.

Don't forget the scaling issues. Scale it down and your aero drag increases, meaning even more mass for you heatshield. Scale it up and all your materials strength issues get worse (mostly in the launcher). I think at some point Scott Manley was talking about this and noted that the heat shield needed for spin launch was similar in mass to the electron rocket (not sure which stages he was talking about), which might make the initial system pretty useless (depending on the cadence they get). And don't forget all the g-forces on your rocket that you would get in an equally long cannon/railgun to orbit, only sideways. I think the real issue is the timing. They need a huge cadence, but since they have such a small launcher they aren't likely to make a profit sending less g-sensitive stuff (fuel?) to orbit en mass. I'd have to assume that now is the moment to strike (any later and they wouldn't be able to bootstrap their way to a larger launcher), but it still doesn't seem like there ever was going to be a window for this type of thing.

I still insist on using "j" for -1.5, especially where current is nearby.

The Paris Gun had a muzzle velocity of 1500 m/s (so sayeth the infallible wiki), so would it be possible to build a multi-stage SRB with the rest of the velocity needed for orbit? You'd presumably be limited to gunpowder based rockets, but you wouldn't need much TWR thanks to the initial velocity. Granted, you'd have to shoot the thing across Germany, but assuming the French demanded this (and used it as such), this would hardly have mattered to the French at the time.

I'll be the one to mention that this might imply metallic hydrogen. But for any newcomers, metallic hydrogen isn't the "miracle fuel" that was hyped across space. Hyped "metalic hydrogen" means meta-stable metallic hydrogen, which appears nearly impossible for it to exist. If this is metallic hydrogen, it almost certainly popped back into normal liquid state right after losing the pressure. Of course if it exists, what happens to astronomy? Astronomers often talk about matter consisting of "hydrogen, helium, and metals (i.e. everything else)". Will they now have to talk about "normal hydrogen, helium, metals, and other metals"?

So instead of leaning during launch, they are doing the "gravity turn" via side boosters? Initial designs of rockets were controversial in Japan thanks to similarity with ICBMs. So early rockets lacked guidance systems and relied on a specific lean of the rocket for orbit. Extremely Kerbal design (I like my rockets to lean in KSP).

Farming the land between Baikonur and just north of China? Gotta be tough to do that. The health problems are vastly more likely to be thanks to the Proton (UDMH) vs. the Soyuz (kerolox). Your links references "perchlorates" which sounds like an important part of US launches (solid rocket motors) which are heavily used by Orbital (Minotaur) and (RSN) the SLS. Do Russians even use SRB mini-boosters wrapped around the boosters like Delta or something? I think India might mix SRB stages with hypergolic stages, but I doubt it adds up to as much atmospheric pollutants as the American launches.

And has all the control of a hot air balloon.

3D printed engines... snicker. Actually, nothing wrong with their tech, just laughing at the marketing. But once you look closer at that "3D printed" bit, you realize that it might give you a bit more control than casting, and not require X-raying to check for cavities (oxidizerless fuel is safe to X-ray, no idea how they handle SRBs). Couldn't find what oxidizer they are using, looks like N2O, but might be LOX. Almost certainly pressurized: see notes on how they throttle and restart.

I've heard they've been in the "firm, fixed price" part of the contract for awhile. If so, it was an oversight. But remember the whole point of the SLS is to be expensive and provide as much pork as possible.

Sure that name isn't Acme? With one Wile E. Coyote as test pilot? Anybody know the Isp of the pressurized air/water combination you had from air pumped toy rockets that were popular in the 1970s? Probably pretty close, especially in terms of "getting to space". This isn't to say that "steam" isn't a good idea, as long as you use hydrogen instead of water (water shows they are clearly optimizing the wrong thing, presumably the better to con investors). NTR uses superheated hydrogen to get amazing Isp (although don't expect to get the TWR to launch from Earth). Launching from Earth may be possible by using lasers to continually heat the "fuel tank" as it loses pressure by providing thrust. On company that went out of business trying to get money for the R&D was called "Escape Dynamics". My guess is the idea is to let the military develop the lasers, and then somehow obtain the tech.

While I'm not as hostile as JoeSchmuckatelli, "geoengineering" implies a far greater grasp of climate and ecology than humanity currently posses. I strongly suggest replacing the name "geoengineering" with "geokludging" to represent how much a last ditch effort it should be. But we still might have to do it. Thirty years of knowing just what we are doing and *now* we should stop poisoning it? I've only seen half-hearted efforts all this time. And the Earth's resiliency typically involves the death of the problematic species in the first place. I don't think it is something we should count on.

After further pondering, I think that last bit misses the point. The problem with nuclear propulsion isn't that the nukes don't get hot enough (i.e. stability levels), but that they don't get hot enough (for higher Isp) because much hotter and you simply can't construct reactors that won't melt. So for conventional NTR the melting point of your reactor is the limit, and then you pass hydrogen through to cool the reactor and heat the hydrogen, and then your Isp is based on the temperature of the hydrogen leaving the reactor. From memory (no time to watch the video), salt water reactors aren't so picky about what is "the reactor" and "the rocket exhaust". This helps bump up the temperature (and thus the Isp) a lot. Presumably enough to justify ejecting matter that isn't hydrogen. Or perhaps it is a different containment mechanism, but the issue isn't the temperature of the reactor, but how you heat up the ejection mass without melting down the rocket.

Too far away? Because it's in the right L2 position. https://www.nasa.gov/topics/universe/features/webb-l2.html

Obviously I was thinking about lunar L2, while Webb is in Sun/Earth L2 and thus shaded by Earth. Any other Lagrange point wouldn't have that, and you would have far more heating/light pollution problems. But the other points still don't make sense (any of the Earth/Moon points, or any other Sun/Earth points).

A few notes: Torchdrive implies constant thrust between planets, and typically 1g acceleration (which provides natural gravity for Earth dwelling people). There's little reason for them to land. SSTOs require TWR>1 (or wings for lift. But anyone with the tech to do SSTO [and especially torchships] won't be using wings). Sure it will change humanity. But would it change humanity more than teleportation, FTL travel, instant communication, replicators, reversible digital circuits (i.e. very low power), and magical batteries? The replicators, magical batteries and what not are far more possible than SSTO and torchships. Look at the equations already. Or just think about how a school for magic would change humanity, because that's what SSTO (and moreso torchships) really are. PS: .001g "torchships" are a thing. Well, maybe with a few more zeros. But ion drives should provide more than a few tricks for moving cargo (don't expect them to be fast enough to transport people directly).

L2 is shaded by the Moon. I don't think the others make sense. I also heard that NRO gave NASA (or at least made availablefor some time) a spare hubble-class mirror. They haven't bothered to launch another Hubble, or even plan a second go after the first gets re-entered. I think the biggest problem in building the thing are the delays. You'd have to build from print, which likely includes parts that haven't been made for 20 years. Don't expect to hire the people who made it originally, so you lost all that expertise. My guess is that you'd start all over again, and the next would cost > $10 Billion (although making a few at a time might make sense).

Look up the nozzle of the shuttle and any other "sustainer" 1.5 stage rockets. They all had to deal with this issue. And why do you keep banging on about designing things that make no sense? If you want to design rockets, learn the rocket equation and all the rest of the physics and engineering. If you want to write a book, either learn the rocket equation (there's a nifty little game that teaches it painlessly linked somewhere on this website) so your readers don't leave nasty reviews saying just how bad the so-called science in your science fiction is or simply don't include the details. Between KSP and the internet, I'd expect a good chunk of anyone reading "space science fiction" to be reasonably aware of the rocket equation and why SSTO is stupid. But if you simply include a belly lander that does SSTO, you can handwave it into "zip fuels" (the name of the search for fuels with higher than hydrolox Isp. They don't appear to exist, but you never know what they might find) if you like. Just don't include a pusher plate, the less details the better. See how intersteller travel is covered with hyperspace, without anyone worrying about causality violations.

And to repeat myself again, go back to the rocket equation. Ramps, slopes, and runways only make sense if your TWR<1. If the slope is low enough (or flat), you'll need wings. SSTO implies "magical" Isp. On the other hand, air-breathing engines tend to use such launch methods and can have enormous Isp. One possibility is a ramped rail system (something like a linear induction motor) to get a ramjet/scramjet up to speed. Note that even with all the advantages of the Isp of air-breathing engines, it still only gets that high Isp while in the atmosphere (and all the drag/heating that comes with it). I'd expect 21st century rockets like this to leave the atmosphere at a respectable speed (mach 6-mach 12) and then switch to rocket engines. Going SSTO would still involve using shear technical power to make such things happen anyway. Not to mention the clunkiness of working the explanation into a sci-fi novel would be fairly contrived: "as you know Bob, the unobtanium widgets allow us to bleed the compressed heat of the scramjet air into the bypass ducts and get enough velocity to make orbit". Contrast it to a "golden age" work having two passengers flying from NYC to Paris in 2000 discussing how the jet engines work. Except as far as I know, 2000 "jet" engines didn't work that way and are high-bypass turbofans. Closer to turboprops than "real" jets (which are mostly confined to military use). I guess you could always play it up for laughs by having Dr. Alice Bechtel saying "as you know Roberta...".

Scott Manley had a video on that as well: I think the title screen sums up his opinion of it. But it is clear that the answer wanted isn't "can we make a nuclear reactor more like a bomb (supercritical)", but really "can we increase a nuclear reaction at a level that remains stable but at a higher rate of energy production". I believe this does this, but maintaining that stability is questionable.

Pretty sure those are more "autogyro" (unpowered) than "helicopter" (powered) blades. Also you know they are "trying everything" when this idea lasted long enough to hand to the artist (probably canceled before he was finished, but a commission is a commission). I have to wonder if the image (without blade system) would have had a glide ratio worse than 1:1 (the Shuttle's) and how much a parachute would weigh to achieve that "lofty" goal. Anybody finally find the fuel tanks in that thing? Pretty sure they are those round things near the engines. Whoever designed this was still thinking of aircraft engines with their amazing Isp. Not rocket engines, full_mass/dry_mass and the rocket equation.