wumpus

I'd expect that asteroid mining will eventually be a thing, but done with robots until proven valuable enough to bring humans along and that humans can get enough done that robots can't.

Commercial crew (both teams) seems to also get a lot of artificial blocks placed in front of them (by NASA) and having the budget cut (both NASA and the Senate), presumably to try to get SLS to launch first. NASA is a big place, but I suspect that the entire Marshal Space Center (and anyone else sufficiently coupled with SLS) doesn't really want to see it fly.

I'm fairly sure Boeing (space)/ULA doesn't do *anything* at their own cost (not sure about their own lobbying. Probably not even that). This makes a lot of sense when your entire business revolves around a single customer. If that customer won't pay for something, it means they don't want it and won't pay for any follow on work. Boeing might be a bit more willing to do such stuff (and used to going at it alone to win airline sales), but that simply isn't how government contractors work.

I suspect the app sold in Norway probably doesn't do full surveillance on students as Norway has laws about such things and enforces them (at least one Scandinavian country busted the maker of an app I was using [Runkeeper] for transmitting GPS data for times not in use). In countries that don't enforce such privacy, I'm certain that the app with the most development and best marketing is going to obtain all the surveillance it can to pay for that development and marketing. And you get to choose between consenting to full location surveillance and your attendance grade. Sometimes in the US you get to choose between surveillance and unemployment (although I suspect such companies find it harder and harder to hire qualified people. Expect more attempts like this during a ressesion). Note that the cellphone companies have known your phone location (or at least which tower it was closest to) since they were "car phones". The network has to know where you are to send a "your phone is ringing" signal. Looks like this topic popped up in a computer security and privacy blog I follow (includes links to those suggesting resistance via hacking): https://www.schneier.com/blog/archives/2019/12/hacking_school_.html#comments

Not just the parents, the professors at college are getting into the act: https://www.washingtonpost.com/technology/2019/12/24/colleges-are-turning-students-phones-into-surveillance-machines-tracking-locations-hundreds-thousands/ Note that this appears to be more about getting your phone to connect via bluetooth pairing, but if they get you to install the app, you better believe the professor, all college staff, the app company, and anyone they sell your data to will all know everywhere you've been and when you were there.

A back of the envelope check says that Falcon 9 gets 3600m/s delta-v from its first stage (in expendable mode. I just plugged mass and fuel into the rocket equation). Scaling the Isp from 282 (sea level) to ~500 gives a first stage delta-v of 6300 m/s (assuming it doesn't burn up in the atmosphere). This would be enough to take the "old" launchable mass and fling it to GTO. Presumably they thought Falcon Heavy would be easier, because that's basically what Falcon Heavy does. Or you could simply reduce the size of the rocket, but that wouldn't give you much of an advantage. I'd also expect that the Meteor missile has the advantage of a narrow range of velocity (highly supersonic, but not trying to reach orbital velocity) and ceiling (roughly the ceiling of fighters and bombers). Any rocket designer trying to use such a ducted engine would have more problems trying to get anywhere close to half orbital velocity. If you want a reusable SSTO with decent payload and chemical propulsion you are on the wrong planet. While you might get a high Isp through air-augmentation, you still are going to need to get the bulk of your delta-v outside the atmosphere, and the best you can do is hydrolox. Consider an air augmented space shuttle (since it already lands and uses hydrolox to orbit, it is as close to an SSTO as we have seen). You would have the "shuttle problem" (80 tons dry weight, 24 tons payload) only with the extra bonus of the fuel tank and [air-augmented] boosters. Do you really think the boosters and fuel tank weigh less than 24 tons dry? Otherwise you don't have *any* payload until you start adding (and carrying) bigger and bigger boosters (which because a worse and worse problem). You might get close with a "real" SCRAMJET engine, but even that requires additional power to get up to speed and then to carry it all the way to orbital velocity (nevermind that the X-43 was thrust limited to ~11km/s, and that's the fastest ever made). I strongly doubt that NTR (the only nuclear rockets* tested) would improve to positive TWR via air-augmentation. But I won't ignore the possibility of a nuclear SSTO, just that chemical rockets won't have the Isp. * ok, I can't include the rocket engine that allegedly exploded in Russia recently. They aren't saying much about what it was and how it worked.

Non-crewed launches are also far more likely to launch on time. Especially for an initial launch. You'd probably have to reserve a few months of your life around Florida's Space Coast to expect to see an initial crewed launch.

There's a ton of problems with air breathers in general, and GNOM and air-augmented rockets have almost all the issues and gain very little. As mentioned "the entire airframe needs to be designed around the intakes". Had Falcon 9 used this design, evolving to block 5 and nearly twice the mass to orbit would have been impossible. Even if you manage to increase Isp to "over 500s", this only works for the first stage. You might save a bit of mass (which would certainly help the costs), but overall it wouldn't change rocket performance as much as you'd expect. Since you are lifting a fairly hefty second stage, fuel usage scales fairly linearly with Isp (once dry mass is reduced to just payload you will see exponential gains), so it isn't all that great. Don't forget that the more delta-v you want out of this stage, the faster you will have to plough through the atmosphere: big gains are a chance to burn up your spacecraft. Oddly enough, I'm a big fan of air breathers, especially the X-43. The catch here is that you are optimizing the wrong problem, the cost of the fuel in the rocket simply is in the noise for a rocket launch. SpaceX is currently attempting to re-use the Falcon 9's fairing (whether or not Mr. Thomas catches it). The cost of the fairing is something like 10 times the cost of the entire fuel budget of a Falcon 9 launch. I'm sure there are plenty more "low lying fruit" to discover and optimize before a huge and expensive project to shave maybe $50k off each flight. Perhaps with Starship [booster] using considerably more fuel, there would be some justification for building some sort of air-breathing booster to launch it, but I doubt there are any plans for that in this decade. I've noted that the crew Bezos hired for Blue Origin seems to have solved a ton of "the next low lying fruit" on an earlier project, perhaps after New Armstrong (assuming the ever build New Glenn) they might work on an air breather sooner. There's an old (from the 1960s) saying in software that "premature optimization is the root of all evil". Designing an air breather now would certainly qualify as premature optimization. For sci-fi, it is quite reasonable that by the time that anybody can simply buy a ticket, go to a spacesport and be in space the next day to be flying by airbreather. Just don't assume it will happen in the 2020s. What would an SSTO look like? Same as any other SSTO (from Earth): comically big, next to zero payload, and definitely single-use-only. And definitely with liquid rockets, unless you want to either relight a solid rocket or have multiple solid rockets on your SSTO. The X-43 has the potential to be an SSTO, but remember that it has almost no payload and barely gets anywhere near orbital velocity: it will still need other stages for pre and post-SCRAM flight (and the research "pre-SCRAM" booster was much bigger than the X-43 itself). There's this great game that teaches things like orbital mechanics and the rocket equation so you don't fall for any pipe dreams like SSTO: it is called Kerbal Space Program and although it is no longer on sale for the Steam Winter Sale, it is still available to teach you these things (although you might need the Realism Overhaul mod to really understand the issues with SSTO. Like the real Moon or Mars, Kerbol is a small planet and SSTO is possible on these bodies).

Pretty sure L. E. Modesitt Jr. used this (or just the freighter) in an early work. Easily justified assuming the character had absolute knowledge of the state of the universe via direct connection from the author, but without that would be a horrendous war crime considering the chance of "I could be wrong". Hydrogen bombs on ICBMs already have hit the "end of the arms race", they inflict sufficient damage such that the target ceases to exist functional society and can't be effectively stopped. The "high speed freighter" has the advantage that any attack that adds energy to it is unlikely to stop it in the least (you have to hit it very early to deflect it, much like a very real asteroid threat to Earth). As far as "radiators for deathrays", elsewhere on this forum* I've calculated that even with unobtanium cooling systems, you'd still only get 36kW/m2 out of your heat sinks (or 60MW for heatsinks the size of ISS). I wouldn't assume any "deathrays", or if you do all combat is trying to stealthily move around (probably next to impossible) to attack from three different angles so you can saturate the heatsinks. * my notes just say ~60MW for ISS-sized heatsink. So I could be wrong by a factor of 14. 21st tech might be able to get close (within half?) but the "unobtanium" requirements are *severe* and the rest is basic thermodynamics.

Back in the 1990s I had a job at a company that made a lot of RADAR consoles for the US Navy. Those consoles would not have looked out of place at NASA during an Apollo launch: some rather basically shaped sheet metal* supporting CRTs and plenty of switches. I suspect that modern consoles are rather similar, with LCDs replacing any display surface, and possibly touchscreens being used. The key point here is that aerospace is a conservative field. And those old control panels *worked* (actually I suspect they are still in use). 10 years ago putting touch surfaces for control would have been asking for a launch failure when one of your critical engineers kept having to cycle through screens because his touchscreen insisted on "interpreting" his touch instead of showing him the data he needed. Even now there is always the danger of the screen being dirty or the new software being buggy in ways that the old wasn't, and all to change something that wasn't broken or even adding mass to the rocket... I doubt that 1960s had anything resembling a GUI as the idea is typically credited as being introduced in 1968 (the mother of all demos by Douglas Englebart). Much of those fancy screens were showing little more than simple slides, although often subtly moved in ways that transmitted important information well (plus a few TVs that were really fancy at the time. Although creating a display on them must have pushed several computers to their limits). * "bent sheet metal" was typically only used for shore duty, while the consoles on ships were milled from a solid block of aluminum. Plenty of business designing entire consoles just for shore duty that could be built for lower costs.

Has a booster hit at 6 m/s and survived? Some of them have come down pretty hot, this might be more a real number than a calculated one.

Mostly by determining atomic weights and then showing that it takes twice as many moles of Hydrogen per mole of oxygen. Showing that hydrogen has an atomic mass of "1" is pretty tricky, as molecular hydrogen almost always wants to combine with just about anything (including itself). Oxygen is also tricky, but I suspect easier than hydrogen (and once you figure out that trick, it will probably work with oxygen). - A chemistry teacher once mentioned that monotomic hydrogen would be roughly as effective as a nuclear rocket (I'm assuming a ~3 digit Isp, we were freshmen students, not rocket scientists so there wasn't any more explanation).

Sitting in front of the consoles or the ones you can hear cheering in the videos? I'd expect them to have plenty, although most of the peoplehours will be spent pouring over the data saved after flight.

The idea is that "skipping off" will avoid flying down to Pe (and slowing the spacecraft enough for re-entry). Raising Ap is impossible, but it is entirely possible that you can gain enough velocity escaping the Moon to have a hyperbolic trajectory (Ap outside of Earth's "sphere of influence") and still having that after the "skip". I wouldn't expect to have such velocity, but if you don't have the life support for a second, lower orbit (that will only go as low as the original "skip") than it doesn't really matter what your final trajectory is. - pedantic note: this assumes that the spacecraft will enter Earth's atmosphere near Pe. If you somehow managed to concoct an orbit where the ellipse is sufficiently narrow to enter it on the sides, it just might be possible to transfer some velocity in a way that increases Ap (at the cost of other velocities). I can't think of any offhand.

I'd assume it means much like a flat stone can be skipped across a pond/lake. Any reader wouldn't expect such a skip to add energy, but it isn't clear that it would necessarily come back down. Accelerating from lunar orbit is already quite close to escape velocity, but I'm sure the skip would slow any ship down enough to put it well under lunar orbit (but still using up all the life support before returning for a second try). Apollo capsules were designed to allow a limited "skip", that is they were designed with the center of mass offset from the center of drag. This let them rotate the spacecraft to correct their course and was apparently originally meant to come down deeper into the atmosphere, raise up (and cool off how?) and finally make a full descent. This was not apparently used (but I doubt they added any ballast to move the CoM closer to the center. Possibly just rearranged some gear). I've heard this myth over and over (before KSP). I can't recall *anyone* pointing out how wrong it is. Does anybody remember Apollo 13 (movie)? I seem to recall them making up a silly story about why the spacecraft had to continue on the way to the Moon instead of something like "as you know, Bob, once we made the burn for the Moon we were committed to at least TLI. Even if we had a working rocket and all the fuel (+oxidizer) was available, we couldn't turn around right now". They seemed to imply that the only reason they couldn't do that is that the damage was in the rocket (oxidizer tank). People aren't expected to know or ever understand orbital mechanics. Perhaps the Smithsonian can add a small area to their "how things fly" exhibit showing the basic idea that you start with an usually only need to increase or decrease the altitude of the opposite side of your orbit. - Edit: according to linked ESA blog above, they included that old myth in the Apollo 13 movie as well (read the book, might have missed a bit where they explain the real issue with "skipping"). Granted, if they were about to re-enter the pacing had to be far to fast for a break for a lesson on orbital mechanics. But it could have easily fit in one of those planning tables at Houston.

And that's enough of a reason. Since 1972 no human (thus nothing but probes) has left LEO. Without any ships going outside of LEO, there's no reason to build an interplanetary engine (although NASA did build a NTR). I'm also not sure what's so great about it. It sounds far more dangerous to develop (see recent Russian missile disaster), while yielding barely any Isp gains over existing NTR designs (which also have political benefits from being grandfathered in by NASA as "man rated"). For probes and other non-crewed vehicles, there is always ion propulsion.

By their explosions shall you know them.

To be honest, I think there was a lot we all didn't know about orbital mechanics before Filipe and co created this wonderful game. Even Randal Monroe has admitted how much he didn't know, with perhaps only Scott Manley leading the way toward getting to orbit. - that said, I remember digging back to the very start of his videos, and he seemed to imply a misconception I had before the game about escape velocity sending you "infinitely far" from your home planet. Granted, this was before the Kerbal system was implemented, so Scott could argue that it was actually the case. But now I know that Earth escape velocity just means you will vary between 0-2 AU from the Earth.

Sure it could, but if you simply lockout any lead slower than the fastest British Vne you don't have to worry about IFF (assuming you are only targeting V-1s).

Which sure enough mentions a British use to target German aircraft responding to their own IFF. The technology just wasn't there to make the encryption fast, light, and strong enough at the same time. But apparently it didn't stop them from trying (and of course British vs. German air battles were typically fought at night where visual identification was far, far, worse. So they pretty much had to try).

True, and a gun optimized to hit a V-1 is unlikely to hit a spitfire (wrong lead times). But I doubt that electronic IFF (identify friend or foe) was a thing during WWII. Somebody had to see the aircraft and decide shoot/don't shoot.

I've heard this a number of times about multiplication of Roman numerals and am shocked it is still repeated (I'm not sure how Egyptian multiplication worked). But Roman multiplication is even easier to learn than with Arabic numbers: n| I V X L C -------------------------------- I| I V X L C V| V XXV D CCL D* X| I D C L* M L | L CCL L* MMD* D** C| C D M D* M** (tack on an extra order of magnitude [base 10] for "*" values. In practice, it appears the Romans didn't need them). Just do multiplications on each number via the multiplication table for each roman numeral. No need to worry about position, just group the whole batch up. Then sort and reduce (by converting groups of numbers into larger ones, etc). But still, you only need to remember a multiplication table 1/4 the size of our own. And far easier I might add. The only thing I know about Egyptian division was that they really only had "proper" fractions (that is 1/some denominator). Possibly, they could figure out that 5/6 would give you 1/6+1/6+1/6+1/6+1/6, but they never had a good way to call it "5/6". And simple tricks like that won't scale well when a scribe has to do some real accounting. But multiplication was never as scary as historians say it was. I won't say that division is even possible with roman numerals. What is psuedo-phonetics? This sounds like the old "ideograms" bit that was an early published attempt to read hieroglyphics. Once it was shown just how much it resembled the modern (might be dead now) Coptic language, it was pretty clear it was reasonably phonetic (Spanish is phonetic. Can't say the same about English). There are something like 5 giant pyramids. King Tut (and any other Pharoh within 1000 years or so of him) was buried in an underground chamber. No "condo made of stona" for him. So unless you are talking about Ramses II or similar Pharoh (I think he clobbered the Hittites at some point), the pyramids had nothing to do with it. Also don't trust trust the hieroglypics painted on temple walls claiming they brought back those spoils of war. They were probably started before the chariots left and finished before word of how the battle ended (or otherwise not changed to reflect reality). They were meant to be impressive (and perhaps act as propaganda to anyone who could read them). Trust the papyruses written in the scribes' shorthand. That will tell you how many chariots came back without riders (of course the chance of finding both writings for number of chariots leaving and returning is almost zero, but sometimes you can get a good idea). Pretty sure they had bronze (although they presumably had to trade/raid for it. Thus Ramses II in the lands of the Hittites [who didn't invent iron smelting like I was taught in school]). It really isn't clear at all if large scale iron production happened anywhere in the first bronze age in the ancient Middle East (the period that ended with the sea people and the fall of every civilization nearby. Except Egypt). Lastly, my father is convinced of this "Egyptians made the pyramids via canals/locks" theory. Without understanding that locks simply aren't ever used unless you have a supply of water higher than the object you want to move (moving the water yourself is far, far, heavier than anything you want to move. Let alone all the water pressure issues). Dear old dad believes strange things (dragged me at a young age to see Chariots of the Gods when I was 5 or so. Found a paperback of the book it was based on while studying biology in high school and couldn't believe just how many trivial, show stopping errors it contained). Still, he would take me to the Smithsonian and gawk with me at the mighty rockets. That and a love of science that includes asking the questions needed to debunk some of his most cherished beliefs...

While it isn't an issue for the Phalanx weapon system (which controls the Navy's big gatling guns), before jets took over those AA guns were controlled/fired by hand and the gunner had to identify friend or foe visually and quickly. Early in WWII, the US found itself shooting down more friend than foe through AA guns (by the time Yamato deployed, they really didn't have enough zeros for this to be an issue). This was eventually corrected, but the techniques to do this became obsolete with jet aircraft (and fortunately published. Far too many are lost since secrecy was maintained by shear habit). For Heinlein fans, much of this was done by one Samuel Renshaw who shows up as "inventing a super memory training device" in several of RAH's works. Pre-google, this took nearly an hour to track down all the information you could get in a single google search, and all day (a trip to the Library of Congress) to confirm no other material was published).

If you absolutely can't afford both (and are set on waiting for KSP2) I'd at least recommend looking for the free demos. There were at least two: .18 (demo) [.02-.18 were also freely available and presumably stuck on a thread somewhere]: this was the game right before it went into "open access". Expect all the weird features you may have heard about "old school KSP": needing aspargus staging to for any large craft, aerodynamics really don't matter and flat, round spacecraft made much sense, and the means to orbit is straight up to 10k, then hard West. 1.0.0 (demo) learning this at least won't require learning KSP(1) again, assuming you find KSP1 on an extreme sale. It has the aero model (both drag and stability. Stability will be the biggest problem if you cut your teeth on .18) and most of the major improvements for release (but is likely more intentionally limited than .18. In .18 I doubt there was any real limits on what you could asparagus together with tiny little rockets). Be warned though: plenty of gamebreaking bugs will be present that weren't really stable until 1.0.3 (if your demo says 1.0.3 then breathe a sigh of relief, but I'm pretty sure it was only 1.0.0).

One thing is that the speed of light has an inverse square relationship with the electric and magnetic permeability of vacuum. So if you reduce the speed of light, you increase the strengths of magnetic and electric fields. This would do wonders to chemistry (probably immediately extinguishing all life) let alone such obvious issues as electronics and electrical devices. And of course the reverse would be likewise true (except for the effects on life of course). The math is beyond me, but I've been told that altering the universes' constants tends to result in a boring, trivial universe that can't support life, and probably can't really support matter as we know it. That said, I highly recommend Vernor Vinge's "A Fire Upon the Deep" and later books that takes this idea (speed of light is variable by location) and runs with it.