wumpus

The "speed of light in a vacuum" is a math abstraction. A photon will only achieve it in an infinitely hard vacuum. So your "fuzzy definition" is accurate. - this is the only bit on this whole section of comment I'm reasonably sure about.

Mass, Mass, and more mass. If the plane starts being more than half its weight in fuel, expect to be able to change plenty of other parameters. I'd expect a hydrogen powered plane to fly higher and be longer as a first-order attempt to reduce air resistance, followed by a wider cabin with the top of the aircraft filled with fuel (possibly something in the bottom allowing a more rectangular cargo space). If insulation is the issue, it is possible that fore and aft sections of the plane will be entirely filled with hydrogen (pulled together to maintain CoM). This should allow a longer airframe with equal stress as the areas furthest from the wings (and thus the worst leverage) will have the lightest mass. This type of design probably winds up looking like an A380 thanks to the need for so much fuel, which is a terrible idea since Dubai was pretty much the main customer of A380s and they aren't interested in direct flights at all. But even when the A380 was designed, I really don't think they ever considered hydrogen. The other huge issue for hydrogen is needing special handling at specific airports, and since A380s basically need specifically wide runways, airports could upgrade both at the same time. The point isn't that it is a good design. The point is that of all hydrogen's few advantages, airlines are customers who really care a lot about at least one of them (weight). They just don't care enough about that to design a plane around it. If airlines won't use hydrogen, and Spacex can originally plan on using hydrogen in BFR (before switching to methane), then you can see that the "hydrogen future" isn't going to happen. Note that hydrogen still is ideal for all stages from MECO to "Earth Escape Engine Cutoff", although spacex probably cares more about being able to use the same engine design for both 1st and 2nd stages (like Falcon 9) and also being able to use a single type of fuel (also like Falcon 9). And they probably want to use the same engine for "Mars escape and return" as "Earth Escape and Hohmann transfer", so "all things are never equal".

Oddly enough, I'd have to assume that the original mission (intercontinental heavy bombing) of the B-52 would have made a lot of sense to use liquid hydrogen. Same for any air flight expected to go more than 1/4 the way around the planet. The catch is that using hydrogen would tie each to such a narrow role to make designing and building such aircraft completely unfeasible. Oddly enough, I mostly point out to hydrogen car fans that the vehicles where hydrogen is a huge advantage is long distance jetliners. And nobody is talking about using hydrogen in them, and for good reasons. One thing that the BFR P2P plan is likely to do is kill any funding for a second generation SST. Any real plans to build a SST would take 20-30 years before the first customer is flow, and do you really want to be that BFR won't be ready to eat your lunch? Spacex may never even try to develop P2P, but if you prove the market is there, they are likely to have just the thing to swoop in and eat your lunch.

Any suborbital BFR would be roughly as dangerous as a trip to orbit in a BFR. While people might accept the danger for going into orbit, I can't imagine somebody betting their life to save 6-10 hours on an international flight (you could presumably book a "sleeper cabin" in a jet cheaper than BFR, so a red eye would be the way to go). Maybe the 3rd or 4th generation "BFR" will be sufficiently safe. I just can't imagine them working out all the bugs withing a decade or two (humanity has been launching people into space since 1961 and there is still at least more than 1% chance of death. It really wouldn't make sense to fly BFR to avoid the cost of a trip at sea). Perhaps the BFR will have a launch cadence high enough to work the bugs out faster, but it will take awhile before enough customers come forth with things they want in space (Falcon is eating up Earth's space manifest, and BFR could launch pretty much Falcon's manifest in one go).

I wonder if they rented a few more tugs to pull the barge faster and outrun the hurricane. It is supposed to be heading far north, but they pretty much need every booster they have.

As far as I know, this is something that Harvester (and presumably whoever else was handling this at Squad at the time) quickly decided that there would be no achievements in KSP, probably right when they contracted for Steam distribution. This makes a lot of sense, although at least with achievements you don't have a specific (and sometimes annoying) order like you do with achievements. Some things I'm glad I skipped: docking (at least until gaining lots of experience on Mun and Minmus) Intercontinental rocketry: really, that was listed on the "wiki campaigns" long before contracts and even "science career mode" airplanes and jet-to-orbit

If biologists ever get tired of dealing with creationists, they ought to forget trying to reason with them and agree that God created all living things. Then work with the Church of Satan to go into great detail about such living things with the tag line "pray to Satan to save you from the Creator". Myth can fly in the face of infinite numbers of facts, but claiming to be the source of that much nightmare fuel is something else entirely.

First: Humans aren't the only species with symbionts large enough to eat: ants and aphids come to mind. There is at least one ecosystem with a single carnivorous animal and plants. The frogs are carnivorous, the tadpoles eat plants. This was exploited by science fiction authors Larry Niven, Jerry Pournelle and Steven Barnes in a book called Beowulf's Children. A new space colony lands on a planet and finds the local predators dangerous to humans and hunts them to [local] extinction. While doing so much havok to an ecology you don't understand isn't a good idea in general, in this case all it meant was that once the next generation of immature predators reached maturity there was a population boom of said dangerous predators.

The requested planet has "Kerbin's surface gravity", so the stock kerbal jetpack doesn't have a TWR >1. I really don't know if "toy solar system's" Kerbin requires more than 600m/s delta-v to get into orbit, but that seems low (Earth is 9,000 1/10th with the same surface gravity (Kerbin) is 3,000, presumably 1/100th with same surface gravity >600 m/s).

If only there existed someone to explain science to KSP players... That said, I'm not sure how you would go about googling this one: https://www.youtube.com/watch?v=Bt54lfOFsDs&list=PLYu7z3I8tdEn2m_lLL3Vn7BDwkvMLo_hl&index=112&t=0s [for some reason embedding the video embeds the wrong one]. The catch here is that you need the object far enough from any other mass so that its sphere of influence is large enough to allow an orbit (you also need Squad to bother allowing a sphere of influence that large when most players will be more interested in how they are orbiting Kerbol). I'd recommend installing Principia if you want to play with such low power orbits. http://google.com/toy-solar-system-mods/ Note that they have dire warnings about not being compatible with 1.0.5, so you might have to pull an ancient copy (from the souposphere era) to be able to use it. I'd expect a jet-powered car to be able to get a kerbal going fast enough to get into orbit using a jetpack (you might even manage on a jetpack powered go-cart, the problem is you can't liftoff in a one-g gravity).

You'd want more than that. One of the tests would be to digitally sample the vinyl and see if it can exactly reproduce whatever Green Baron prefers. The math simply says that you can store an arbitrary waveform on the CD and that there can exist (but certainly didn't in the 1980s but should now) a player that can reproduce that waveform exactly as recorded. It doesn't mean you will prefer it to whatever distortion happens when you press to vinyl. I know I've seen warnings about "studio monitor" headphones and speakers claiming that while they may produce wildly better sound, consumer recordings are mastered with such flat levels in mind.

Here's a link to Shannon's mathematical proof of the Nyquist criterion : https://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem You can perfectly reconstruct a sound wave from 0-22.05kHz up to 90dB S/N ratio. Good luck finding a recording to master with that has a better S/N ratio, but children capable of hearing >22kHz might notice the difference. Aside from that, every "harmony and overtone" in the original recording is on the CD (if the recording engineer wanted to put it there). If the CD was mastered for "loudness" (the recording engineer's equivalent of dumping salt and sugar all over the food) you won't hear the subtle cues over the "loudness" (it will be masked much the way the stuff that gets removed in MP3s are masked), but that isn't the fault of the media. Anything you can record and hear will fit in a cd (with the possible exception once you play over 90dB, but I'm almost positive that will still mask your hearing, and some things only young children can hear) but don't really think the same is true on vinyl. Note: 90dB hits "regular sustained exposure may cause permanent damage", so be careful in listening at levels where it is even possible to hear the difference. As mentioned above this is the weak point in cd recording, they should have used logrithmic levels or encoded some sort of "maximum volume of the next few miliseconds" and recorded a ratio of that. But even then 90dB of range is next to impossible to beat with vinyl and equally difficult to design ADCs (analog to digital converters) to put on a CD.

The reason I specified the 1980s wasn't the quality of the recordings (although most of them were taken from analog masters, digital mastering was a new thing and you were still likely better off having an experienced analog engineer using the toolchain he was familiar with), but the output devices. It all came down to sampling theory and the electronics of the day: CDs are sampled at 44.1kHz. According to Shannon and the Nyquist criterion that means that we can't reproduce any signal under 22.05 kHz. More importantly, all frequencies >22kHz are copies of the spectrum from 0-22kHz and since roughly half the output power of music is <1kHz, that means you have a godawful screetch at 22-23kHz. To get around this, "oversampling" is done where zeros are inserted between the samples on the disc giving a new sampling rate of at least 176kHz (at first they used "four way supersampling". It might be higher now, but 2 is probably enough and I have no idea if your dog will thank you about using more. Even your kids won't hear it). Note that this doesn't do anything about the screetch at 23kHz, but at least it allows the engineers to fix the digital signal instead of the analog signal. Modern cd players almost certainly use 1024 point FFTs to completely eliminate the screetch (that algorithm* is required to play MP3s), but that type of thing was completely out of the question in the 1980s and early 90s. More likely the engineers of the time used notch filters (to just scrub the screetch) and IIRs (which have nasty phase issues). I'd expect any 1980s cd player to have lousy reproduction of high frequency ranges, especially messing up the phase. No idea if the recording engineers tried to compensate for this type of thing (which would mess up modern players). I'd be very, very impressed if someone managed to get vinyl up to cd standards, especially if it didn't wear down below cd standards after the first listen or so. One large error in the cd standard was that they used linear recording instead of a logarithmic encoding. Expanding the A-law to a 16 bit linear input would have been more efficient, although I don't know how you would "spend" the efficiency: obvious choices are even greater range (although 16 bits was already >100dB S/N, pretty much beyond human hearing), expanding the sampling range (which as noted above would mostly only temporarily help, there's a reason modern systems rarely go beyond 44kHz sampling), and simply extend the amount of music on the disc (a cd can fit Beethoven's Ninth, and most labels seemed content with leaving the amount of music sold on a disc to ~40 minutes, at least during the 80s) * ok, technically it is a DCT. I'm pretty sure you can replace the FFT with a DCT with barely any change in your filter design (except of course the obvious change in complex coefficients). PS: Apparently not only do modern computers (at least LCD screens) make noise, you can even attempt to read the screen that way: https://arstechnica.com/information-technology/2018/08/researchers-find-way-to-spy-on-remote-screens-through-the-webcam-mic/

According to Scott Manley (the Oracle of KSP), that was step one. Step two involved space tape (I'd thought "aircraft grade" tape would work, even common duct tape should work). Duck tape was insufficient: I think the unpatched 2mm hole would leak out in 2 weeks, suspect it leaks much slower with duct tape. No idea what the pressure for "in 2 weeks of unpatched time" leaves: 1/2 STP is about 4km up (serious mountaineering, but survivable), I think the "dead zone" is 30-40kPa or 1/3 STP. https://www.youtube.com/watch?v=QzTSnvthZYw

There's a somewhat new saying amoung EMTs “Nobody is dead until warm and dead”. So resurrection is mainly an issue if you let the body die (legally required in the US) instead of frozen while kept alive by machines. As far as I know the only way to tell if a patient survived heart bypass surgery (the patient is taken down to a few degrees C during the operation) is to complete the surgery, warm up the patient, and wait. Current technology can freeze a mouse and revive it (although I have no idea of the mouse's chances), but as far as I know no cryogenics firms have even attempted research to work their way up to and through primates. This should tell you all you need to know about human cryogenics. If you need anymore I'd suggest following the rationalwiki link. Until somebody has a reasonable understanding of how to freeze a primate without leaving a useless corpse, there's little reason to change the law to allow freezing while technically alive. https://www.sciencedirect.com/science/article/pii/S0300957214005243

I remember one guy in high school electronics class that could hear up to 22kHz (possibly a bit beyond). We were testing amplifiers that we built up to 22kHz and typically the kids would leave them there because they couldn't hear it, eventually leading to the cry of "turn it off already!". To be honest, if you can hear above 22kHz you might find cd players (especially early ones) make unpleasant sounds. According to the infallible wiki, dog whistles start at 23kHz (did cds sound weird? Were you around and could hear like that in the 1980s?). Back then, I think my hearing cut out at 16-18kHz. According to various youtube tests, it doesn't go much above 10k (maybe I should download one of those old mp3 encoders that simply lopped of the upper frequency range).

The catch is that you still have to bring a lot of food and other supplies from Earth. Biosphere 2 was pretty much a disaster and had essentially an infinite mass budget (compared to anything on Mars).

Still? console (dim, low power) LEDs shouldn't have enough power to make [audio] noise (they are often dimmed by strobing at frequencies you can hear, but I doubt they make any sound). Lighting LEDs should have constant current power supplies and should not be dimmed by strobing at all (and the power supplies should be at least in the 100kHz range and typically 1-10 MHz [probably higher nowadays]). Not sure what would make noise in a computer, but too many components to keep track of (the CRT was a big one, but that should be gone. Don't expect to hear the same from an LCD). There are a ton of high frequencies bouncing around a computer, but don't expect anything in the audio range.

I generally point out to new KSP players that having MECO 1/2 your orbital delta-v (or more specifically, having each stage with equal delta-v) is generally a good place to start your rocket design (unfortunately, there is no clear optimal and you have to iterate any design). Early (and current non-recoverable) Falcon 9 rockets appeared to have a much later MECO (obviously that last 10% or so provides significant delta-v), and Falcon Heavy returns the center stage after a significantly delayed MECO (and the first crashed). I'm curious to see if BFR has a MECO above 4 km/s, as that is likely to be more efficient (and probably necessary for that claim of "SSTO with no cargo, and presumably no return"). And if SpaceX wants to return the second stage (as planned), they will need to deal with significant speeds (although probably through backburns as they are doing now).

Note that the reduced heating is presumably due the hottest part of the compressed gasses in front of the heatshield being pushed further away and around the heatshield. The total heat generated should be higher as it is proportional to the area and speed of the heatshield. I think I was only aware of the failed 2016 test. I'm impressed that there were two previous successes. I still don't expect any recovery effort from ULA to be more than "checkbox engineering" where they go through the motions because the contract demanded it (if you want them to recover, you better put "use a previously used engine" requirement for some flights).

Lasers are an inefficient means of increasing or removing momentum, although I can't understand why the OP wants to increase orbital height (and thus keep junk in space much longer). I'd recommend an ion-powered device capable of rendezvous (more or less ahead of the device) and firing whatever (preferably something sticky, possibly magnetic if sufficiently ferrous) at the junk to lower its orbital velocity (only needs a 100m/s or so lower to de-orbit junk at ISS orbits). Lasers might work as well, but I suspect that any space junk at such heights might naturally decay before the laser removes enough delta-v. At sufficiently low orbits, it might be enough that the 'pellet' would be a parachute made of an extremely fine film, which would be expanded (presumably by a gas) after the line adhered to the spacejunk. A parachute might work slow in orbit, but when it only has to reduce velocity by 100m/s, it should work well enough (and once it reduces velocity a little, the parachute should get more and more effective. It might even let you chose where to land the thing). Increasing orbital height is the idea for GSO and similar satellites. For anything between LEO and GSO, things aren't terribly obvious (I'm guessing capture and de-orbit, so things have to be extremely large and/or dangerous).

Hate to tell you but Dream Chaser is 9tons with 5 tons of cargo. It doesn't appear to have significant delta-v, and would be lifted by an Atlas V. While your numbers fit the rocket equation, I don't think you can land the craft that can wrap itself around that fuel with only that mass.

Appears drawn as single stage, which strongly implies suborbital. Note that the Minotaur 1 used a modified Pegasus (Orion 38) rocket to put a 1.7 ton load into LEO (I think. That might be with the upgraded Star engine. Wiki isn't explicit or its usual infallible self). Even so, strapping additional stages to a pegasus in an effort to launch .5tons to GTO instead of LEO is likely a useful thing for a Pegasus (and launch into GTO makes much more sense for air-launch). Note that I doubt that anyone would be too worried moving an engine/nozzle designed for 40,000 feet and above to vacuum only flight (if not just grab the nozzle from minotaur I or IV). As far as "what's changed", I'm guessing that management changed. Once Northrup Grumman acquired Orbital-ATK, somebody thought it would be a great idea to build a rocket for Paul Allen. Or maybe Paul Allen thought that if NG wouldn't build for him he'd have to build for himself. But I'd be pretty surprised if the first effort didn't build on the Pegasus.

There's also the possibility of the metal suit being an excellent heat conductor and the dangers of hypothermia. In this case it would be more of a danger of falling from 15,000 to 10,000 feet. Mountains at 5,000 feet aren't so bad, I don't know about open cockpit planes, but I doubt that hypothermia from a <1 minute fall would kill you.

If you click the "stay prograde" icon without a small lurch at the start, you will continue burning prograde all the way up. That isn't an efficient means to extreme altitude. The issue is gravity will dragging you antigrade if you fire straight up and radially if you follow a pitchover (gravity turn in KSP-lingo). Your rocket should burn prograde in either situation. Having gravity pull radially will chart a vector (on a polar graph) at a higher altitude (over someplace towards prograde) while having gravity pull antigrade will simply slow you down going straight up. "Prograde" simply means following your current velocity. It doesn't assume you are heading into orbit.