brdavis

Short answer… I don't think so. But I'm ready to be corrected It's going to depend on a heck of a lot. You would need to take into account what the T/W ratio is, as well as what the ascent profile is (where do you start your gravity turn, etc.). As one example, picture two identical spacecraft… one with a T/W ratio of 2.0, and one with a T/W ratio of 0.9. The first will perhaps reach orbit, but the second would just sit on the ground… even infinite delta-v isn't going to do it. You can make some rough estimates… For example, picture a really poor way of doing it: one big impulsive kick from the launching pad, and then at the peak of the "arc", one big impulsive kick sideways to acquire orbital velocity. If you want to use this to reach a circular orbit at, say, 100 km, it will take roughly a delta-v = sqrt( 2 g h ) = sqrt (2 g (100 km) ) to "toss up" the spacecraft to that height, and then a kick sideways of delta-v = sort ( G M / a ). That's a lousy way of doing it (not efficient), but it's one estimate. A second way would be to launch with a single impulsive kick right from the ground into a Hohmann transfer orbit that just "kisses" the ground, and just "kisses" the desired orbit. That's just a standard transfer orbit calculation. None of these are "right" - an actual gravity turn is different, and atmospheres play a significant role that's hard to calculate exactly (not only does atmospheric density matter, but so does scale height, which is different for each planet… but, hey, at least the designers used a constant scale height instead of a temperature-varying one ). So now… what are you trying to communicate in your video? Because the complete problem is perhaps more than you want to deal with in a YT video (do some research on the Goddard problem if you desire). PS- Why, yes I have spent the last couple days trying to work out exact delta-v's for a Duna-Ike mission. So i might be a bit buried in calculations… but for some of us lost souls, that's half the fun.

Strangely I've not yet had an overheat warning on my laptop (MacBook Pro). Of course this could be due to me balancing the bottom of the laptop on a gallon-sized Ziploc back of water. Heat sinks are easy on laptops

To put it another way, Don Quixote is clinically insane and delusional, and yet still an inspiration. I'm never going to even think of trying to build the things Whackjob has… but I still get a kick out of seeing them (even when my personal style is exactly the opposite - what's the smallest[i/] mission to Duna I can manage, etc.)

I used KSP (Demo version, actually) to design a college-level lab around. Orbital mechanics, yes (I had a prepared game set up with a basic ship already in orbit), including calculating orbital velocities, circular orbits, what thrusting prograde/retrograde/up/down/in/out all do… and while they were at it, figuring out what the thrust of the engine was (very good physics there - do five trials, why is the acceleration different each time, leads to the idea of changing mass, etc.) There's lots more.

XKCD for me.

While I agree with you that would be nice… they've already said the asteroids aren't going to have gravity. If a spaceship isn't gravitationally attracted to them… it's hard to use the gravity tractor beam approach to alter their orbit. But now I've starting thinking… solar sail? Yarkovsky effect? Just how complex a physics model can you have and still run at a frame rate better than 1 fps?

And Mac players don't have either to begin with

Sort of ironic. I could do all those things long before KSP… so "expert" is in the internal eyes of the beholder (no, I'm *NO* expert, but I play one while teaching physics ).

The magnetic field isn't needed - even for Earth, with just 1 Atm of N2/O2, the atmosphere (not the magnetic field) is what's shielding out high energy radiation. With no magnetic field over billions of years you can have atmospheric erosion… but that's not really the big problem for Venus As to the day… there actually are proposals for how to "spin up" Venus (and, for that matter, change its orbit… yes, that's possible, it just ties very large-scale engineering. John Birch did some great work on this, using the same technique to build a habitable 1 G environment over the entire sphere of Jupiter (yes, really), etc.). Getting rid of the atmosphere (will, 98% of it anyway) is tough. The best plan I've seen calls for importing things like Ca from Mercury - you need to pretty much strip-mine Mercury to get enough Ca to lock up Venus's atmosphere however. For those with access to a good library, see if you can lay hands on Martyn Fogg's "Terraforming" textbook. Put out by the Society of Automotive Engineers (yes, really), this has all the references, works the numbers (energy, not materials, is often the limiting factor), and details the timescales. It does not worry too much with the economics

Well that should be interesting. Not sure how that could work with the current two view modes, but I could see it being done with a special Science! instrument. Mount a space telescope on a satellite and it starts "painting" or "lighting up" everything that's at opposition (opposite the Sun in the sky). Once "painted" you know the orbit (shows in map view), but until "painted" not discovered (invisible)? Just WAGing. I've only installed my first mods this weekend (Kethane and KAS), but it would seem to me that the KAS grappling hook (or something with similar functionality) would be ideal here. You're assuming asteroids spawn completely randomly in orbit… and you're right, even in the tiny Kerbal system, the chances of a collision are negligible. But… this is a game. And the inspiration for this seems to be an 'asteroid on a tremendously unlikely course is headed for Kerbin, what are the odds?!?' sort of set-up. So… the occasional non-random asteroid "stormlet" headed towards your space station might be possible. The thing I don't see how to manage yet actual impact between an asteroid and a craft. Even at 1x warp, the cloying velocities make for a likely 'teleport through' scenario as far as I can see. It would be fun if impacts left scars of some type… if not actual craters on the Mun, at least albedo variations. I can see it now, one of the contracts is painting "Jeb Must Die" on the near side of the Mun in letters 2 km high, using only targeted asteroid impacts. Personally, gigantnormous parts doesn't make me quite as excited. It's not because I can't use them… they will make producing really large massive boosters easier. But I guess for me (maybe because I'm a 'young' player) the challenge is minimalist - just how small a margin can I have and still make it back from Duna, for example. Meh, something for everybody here… and if I want incentive for keeping things small and under control, I guess I just have to wait until all those parts actually cost something

This is sort of curious, as I'm teaching this on Monday… so here's my take on it, for what it's worth. The Ptolomaic (Earth-centered) system with epicycles was a good system - it predicted things rather accurately, and had a number of simplifying features (everything moved in perfect circles, for example. The Copernician (Sun-centered) system offered a couple of predictions - first, it predicted the distance to the outer planets (the Ptolomaic system didn't constrain that), which, while nice, they had no way to measure. It also predicted there should be a shift in the positions of the stars over the year… which was very pointedly *not* observed. So, observationally… the Earth-centered system made more sense. More specifically, Copernicus (who nicked the idea from the ancient Greeks - they, too, had proposed a sun-centered system) worked with perfect circles… and in order to get predictions as accurate as the Ptolomaic system, also had to add back in epicycles, deferents, and the whole load of baggage that went with it. By the time you patched the Copernician system up to the point where it worked as well as the Ptolomaic system… it wasn't any simpler. Far from it. It really wasn't until Kepler took Tycho's data, tried to fit it to any existing model, and realized neither of them worked, that he invented a fix - not just Sun-centered paths, but eccentric paths, with varying velocities. With that, he finally had a system that could out-perform an Earth-centered one. and it still took about 100 years until some kid in his 20's explained it all while inventing calculus and integration in his spare time (Newton). You don't throw out a model, or theory, until there's some good reason to. Copernicus really didn't have one - and in fact observers like Tycho had good evidence that Copernican theory didn't match the observations. It wasn't until Kepler tried to reduce Tycho's (astoundingly precise) data that there was any really good reason to pick one over the other… and as it turns out, what resulted was really a third, novel system.

Interesting. I'm still brand-spankin'-new to all this, and every time a new version comes out, I start a brand new career mode (hey, we're supposed to be testing, right?!?). So i've not gotten too far, but just completed my first Kerbaled mission to Duna. 1. Set goal (get to Duna and back with a live Kerbal; sanity optional) 2. Sit down and work out exactly how that's going to work, backwards: --Kerbal atmospheric entry? --Duna-Kerbal transfer stage? --Duna ascent stage? --Duna lander? --Kerbal-Duna transfer stage? --Kerbal heavy lift vehicle? I work out all the delta-v's, required thrusts, fuel loads, docking & reconfiguration procedures, all at this stage. 3. Go to the VAB and build first part, testing it unmanned 4. Refine until it works, then back to step 3 for the next part. Repeat until finished. 5. Launch it and perform the mission, discovering something like "oh yeah, I really did need batteries" or similar. 6. Success. Or, spectacular, very well-researched failure. Whatever. For me, planning it out is as important a part of the game as anything else - because for me, that's fun. when I did the mission and got the Duna ascent stage to dock with the interplanetary transfer stage that had been left in orbit, that was wonderful… but the fact that I only had just enough reaction mass to do it is what made my day .

Heard from my son, across the room playing 0.22 … "Well, that can't be good…"

Agreed. Daedalus was a looong time ago, and other than minor economic problems*, they had touched on most of the problems and possible solutions of fusion/orion style missions. For laser sails, I've always thought Starwisp would be an interesting way to go (really really cheap in some sense). Beamriders (using smart pellets, not energy-based beams) are another possibility. Forget (currently) mythical warp drives of one form or another - there's ways to do this under current physics and understandings. But… Sadly I have to agree there too. It's not that we can't do these things… it's just that right now, there are better and cheaper ways to accomplish most of the goals of such interstellar missions. Which doesn't make me stop wanting them… but does make them hard to justify. *here "minor economic problems" can be viewed as "make a unified world government and focus the bulk of the world GDP into a production program aimed at mining Jupiter's atmosphere wholesale using hundreds to thousands of floating atmospheric refineries, over a period of 50+ years… Just To Get The Fuel". So, yeah, you know… no serious practical problems

Whoa. Really? Do you have a source, or a BotE calc for this? There's a whole lot of oxygen in the Earth's atmosphere… and not a lot of reduced stuff like methane or reduced sulfur compounds being produced by volcanoes. Yes, the atmosphere will eventually go from oxidized to natural (or even reduced), but a timescale of a couple centuries seems *amazingly* short - I would have guessed a couple million to several tens of millions of years, minimum. Rocks aren't going to oxidize - they already are. The same for the current sulfur compounds and iron compounds in the surface and crust (oxidizing those in the first place is where the bulk of photosynthetic O2 went… but those reservoirs have been fully oxidized, which is exactly why we managed to build up an oxygen-rixh atmosphere after. source? Help a Kerbal out.

Agreed There is, sort of, an aerobraking way of capturing a moon too (this is a mechanism for the outer moons of Jupiter and Saturn, for instance). A passing object is captured into orbit via gas drag from the pro to-Jupiter nebula, and then the remainder of the nebula gets blown away as the Sun "turns on". The result is that extremely distance moons are often as much prograde as retrograde. The inner gas giant moons (Io, Europa, Titan, Dione, etc.) likely formed in situ via accretion in mini-nebulas that a gas giant planet could form. You can have moons captured via likely traumatic three-body interactions (up to and including lithobraking with a pre-existing moon). Triton around Neptune is a likely candidate (which would also explain why Neptune doesn't have much of a "regular" moon system; it was likely disrupted by the capture of an object as large as Triton into a retrograde orbit) You can have moons generated via the "giant impact" mechanism (Earth and Pluto would both fall into that category, as likely would a whole lot of asteroids with moon lets). You can have planets that tidal effects would have removed the moons - a moon of Venus or Mercury above a certain (rather small) size wouldn't exist until the current epoch, because it would tidally lock to the planet below, and then solar tides would actually start moving it down towards the planet, resulting in the once-moon either deorbiting or reaching escape from the smaller SOI of these inner worlds by the current time. And then you can have things like Phobos & Deimos around Mars, which… well, umm… they look like captured asteroids. So we can try that. Even if the dynamics really doesn't work out. So, yeah... jury is largely still out on those.

Read "Downbelow Station" - ships doing combat at real-space FTL. No, not possible… but Cherryh at least addresses the "what you see isn't where it is" with a technique called "longscan", essentially a probabilistic mapping of where other ships might be in an FTL firefight. It may not be great science… but it's a great example of addressing a flaw and turning it into an strength in the story (the space-based conflicts are very interesting).

A lot of bombs. A whole whole lot of bombs. Each of which is really really really big. To the point of being utterly silly. The gravitational binding energy of the Earth is around 2e+32 J - so the reduce the Earth to a cloud of expanding rubble, you have to add in at a minimum that much energy. Assuming you don't loose anything to heating the rubble (neat trick), compare it to some other really really energetic event - like, say, the Chicxulub impact (around 5e+23 J). "Planet busting" the Earth would be like 400,000,000 Dinosaur-killer impacts in terms of energy. It's the equivalent of the solar energy intercepted by the Earth, all of it, for 36 million years. If you can handle these sorts of energy… you have no need for planets. Or probably even stars. And it's overkill by ten's or orders of magnitude as a method to kill a civilization… or even to completely sterilize a planet. No… "planet-busters" would be another dumb one for me. I can only think of one story that's ever done it halfway convincingly is Bear's "The Forge of God"… and it was honestly still a huge huge stretch to figure out why anyone would ever even consider doing it.

One of my YT videos uses a track I created myself in Apple's GarageBand, using the stock loops. I eventually found my video blocked due to copyright dispute from some guy in Europe. I listened to his stuff… sure enough, he'd slapped a few of Apple's loops together, and indeed when he did an automated search mine used some of the same sounds. Imagine that. It was a very enjoyable email exchange. I enjoyed pointing out that if the music he was so proud of could be duplicated by some physics teacher fooling around in GarageBand… then maybe his creative skills might be slightly lacking. He went away

Once a particle gets trapped in the Earth's field, it spirals around the magnetic field lines (OK, I hate that analogy, but it's sometimes useful). For low-energy (relatively) particles, they are "bounced back" or reflected from the polar regions (due to a higher field strength)… but if they are energetic enough, they spiral around those lines right down into the polar atmosphere, kicking the snot out of oxygen, nitrogen, etc., and making pretty lights. You're right, that doesn't hurt you, even if you are "under" them… because a little bit of atmosphere is great shielding. Those particles are dumping energy into the upper atmosphere, instead of you, so this shows both the energy involved, and why an atmosphere (not a magnetic field in all cases) is enough to protect you. Upshot: a gas giant moon can have a habitable surface (due to an atmosphere), but might have a very very inhospitable radiation environment right outside the atmosphere (due to charged particles piled up in the gas giant's magnetic field). On Earth, we've got the "Van Allen radiation" belts… around Jupiter you have the "Van Allen you're already dead if you're here" belts.

In that case, then, it's possible. Maybe due to a whole bunch of Squad miniliths acting as radiation-free fusion sources all over the bottom of the oceans. But short of nearly magic tech like that… yeah, highly highly HIGHLY unlikely Magnetic fields… they can save you, and they can kill you. Jupiter has a strong magnetic field, which means that any charged particles that end up in it, end up staying in it. The result is a belt of magnetically trapped high energy particles around objects with strong magnetic fields. Earth has them as well - they are just weaker. And still to be avoided on space missions, if at all possible. Yeah… put that in. Radiation environments harsh enough to 'kill' or at least 'break' mission to some of KSP's planets. Ouch. Almost up there with an earlier suggestion that KSP model occasional unplanned engine failure.

I'd say yes, absolutely. A large Moon (planet-sized) in orbit around a very large gas giant, where the gas giant orbits in the habitable zone of the parent star, seems eminently "doable". Although the length of a solar day on said moon might be inconveniently long, still not a show-stopper by any means. Hmm… on the surface? Open water? With an insolation that's 1/25th the Earths? It would seem very, very doubtful to me Yes. All you need is shielding… although getting off-world is likely to be a rather short-lived endeavor. True, but note that there's a tremendous selection bias operating here. Distant gas giants (distant planets in general) are far less likely to be detected by both transit and radial velocity methods. You can guess the total numbers of planets in the galaxy, for example, but the precision depends on some assumptions about detection efficiency that are really not well understood as yet.

(Forgive me for what follows; I’m a physicist who teaching 100-level planetary science, so... yeah, these conversations resonant with me. The pun is coming.) I’d agree, but have to add applying rigorous science... to a game where the planets are made of unobtanium, denser than all known materials, and is based on a star that can’t exist... well, rigorous physics probably isn’t going to help resolve the question Yep, excellent analysis. At Laythe’s distance it is receiving 1/25th the solar energy as at Kerbin’s distance: Kerbin receives a *surface* average of 343 W/m^2 (not, actually, the 1370 W/m^2 that’s been thrown out there - that’s the intensity at 1 AU from the Sun, but a planet absorbs that over not its whole surface, but only its cross-sectional area; that throws in a factor of 1/4th). Laythe would then receive about 14 W/m^2 (again, averaged over the entire surface). In order to get the same amount of heating as Kerbin, Laythe would seem to need at least 329 W/m^2 additional. Tidal heating? Well... Io, the most tidally heated object we’ve got as an analog, produces 2.5 W/m^2 global average. So... Is Laythe a minimum of 130 times as tidally heated as Io? I have my (extreme) doubts. Furthermore that 0.8 Atm isn’t going to help much... not as much as the 1 Atm on Kerbin, for example. Greenhouse effect can help... but not that much. Got it in one, Mr Garibaldi . Neutron star matter isn’t stable at normal pressures. Don’t read this, you’ll find out it’s impossible. Oops . That’s a good point, but I think it’s worth pointing out that the developers got this right - tidal heating in a Galilean resonance* means those orbits *can’t* be circular... but the very small dynamically excited eccentricity does result in significant tidal heating even through the orbits appear very very close to zero. Io has an eccentricity of 0.0041. That’s something like an order of magnitude smaller than any listed KSP eccentricity (I think?), so I’d say you can easily assume Laythe has an eccentricity... just one small enough you don’t bother modeling it. Note that while a magnetic field is very handy, an atmosphere is a *great* shield. A breathable atmosphere will probably shield you from radiation here just fine (at least for as long as it lasts**) There is an important exception - given a planet that is entirely water (little to no rocky core at all, but overwhelmingly dominated by water), you actually would expect an oxygen atmosphere in some circumstances. UV splitting of H2O will give you an extremely oxidizing environment if the planet is small enough that H2 can escape, and with no significant reduced surface materials to oxidize... the O2 builds up. And up. And up. The result would be an interesting world... the water would end up with a lot of things like peroxides in it in potentially pretty significant concentrations. Want to watch your boat dissolve due to the water while potentially burning like a magnesium flare under a high-pressure pure oxygen environment? That could make an interesting world for boating Kerbals . *that was the pun. Got it? Yeah, it’s a stretch*** **because let’s face it, we haven’t even touched[/] on atmospheric lifetimes here ***â€Âa stretchâ€Â. See what I did there? PS- At what point should this end up in “Science Labsâ€Â?

There does seem to be a bit of irony when we're all playing a game with a "star" that's a factor of ten off from the smallest star possible in a "solar system" where everything would pretty much fit within the orbit of Venus… and the #1 complaint on the poll currently is "unrealistic distances".

Niether was I, actually. The abstract talks about detecting 21-Ne, 36-Ar, and 3-He, all gases (and all used for CRE age estimates… what tells you it's been on the surface), as well as the K-Ar dating. So I'm guessing this was done with SAM, which has a mass spectrometer so it can do isotopic analysis. The actual article, alas, is locked behind a paywall… I might grab a copy when I'm at work later this week (the university has access).