wumpus

They *are* storing it as a liquid (and getting the cold effects as it boils when used). The whole point is that you don't *want* any fuel that *has* to be that cold (a good part of the reason that hypergolics are still used). Also it has been used as the sole oxidizer by space ship one (but not two/three) and plenty of amature rockets.

Have hybrid (solid/liquid) rockets been considered for RCS? My guess is that they would be more for corrective burns and other things that require higher (but still moderate) Isp and fewer re-lights. Basically they allow a broad level of temperature storage (hot rodders keep N2O under the hood of their cars. Boiloff isn't an issue), allow easy throttle abilities and reuse. The missing ingredient is that they aren't hypergolic and that re-lighting will probably kill any attempt for integrating them into an RCS (no matter how reliable, no part is more reliable than not needing the part in the first place).

It is hardly my chart (this one came from KSP-wiki, with plenty of cites to reddit). But once you understand delta-v (like the OP was learning), it is a great time to see it. I have an older one printed out taped to the side of my monitor.

You will always get more delta-v by burning low Isp fuels first. The catch is, that when launching a rocket in a gravitational field you also have gravity losses. So instead of getting all of your delta-v, you get a percentage of your delta-v equal to ((TWR-1)/TWR). If this corrected delta-v is higher due to the increased TWR of your rocket (because you are burning both liquid and solid boosters), then you will get more delta-v out of your rocket. Note that for higher TWRs this only works on airless worlds and that the "1" implies that TWR is localized (technically, the "thrust to weight ratio implies localization). I'm guessing that there should be some simple relation between (TWR-1)/TWR and the ratio of the two ISPs (assuming you have boosters and liquid rockets) that tells you to throttle down the liquid rockets, but in my experience it merely give me an opportunity to botch the steering.

Calculating the delta-v for simple craft is trivial. Strap on some SRBs (while the main [liquid] rocket is also firing and you will either need to download KER or dig into the derivation to figure out where to plug in all the changes). Note that the equation will naively insist on using low-Isp fuels first, without any checking on the efficiency changes due to the TWR changes. This is pretty critical to understanding where delta-v fits in importance. It is more or less everything between bodies (assuming you are willing to perform Mangalyaan maneuvers to get there) but you must balance TWR for take-off and (powered) landings. Once you understand delta-v, get a load of this: Pretty much a complete guide to the Kerbol system. Just remember ULA's recent launch and have a good sized fuel margin.

And having engine gimballing being cheaper than ailerons is oh so much more realistic? Even the kickers don't get beyond the atmosphere.

The two 1.5 engines are simply given to you at the start of the tech tree. Don't expect much. On the other hand, the LV-909 ("terrier") remains one of the best engines throughout the entire game (even after being nerfed in an atmosphere). The poodle might have a slight advantage in TWR, but typically where the LV-909 shines the advantage in mass simply overwhelms it (the poodle's mass puts it closer to the "nerv" which is simply the way to go if you can afford the mass). The biggest issue with the reliant/swivel is that you can typically get cheaper delta-v via SRBs (especially at that tech level). Typically the rockets are small enough that the capsule torque can control SRBs, and once they burn out there often isn't a window where the LV-909 isn't the better choice.

I have to admit, when I downloaded the demo over the Christmas holiday (and somehow got the old .18 demo), I had a chance to re-experience a more "pure" kerbal experience. I still prefer the modern game (and the unforgiving nature of a "real" atmosphere makes me highly recommend KER to beginners) and won't be uninstalling mods anytime soon, but it did help to come down to kerbals, boosters, and more boosters. The thing that the demo really brings is the part limitation. With the full suite of KSP parts, there is nearly always a bigger engine to lift whatever you want efficiently. With the demo, it pretty much comes down to asparagusing parts over and over until you have enough delta-v. Then there is the issue of not knowing your amount of delta-v and simply overbuilding so you can get to the Mun and back. There is a fundamental disconnect between players and Squad over this, but I suspect that 1.1 will finally admit to the amount of delta-v in the rocket. So I would recommend that even the most hardened KSP players consider trying the demo* once again. Try to remember when the game was more about kerbals and less about delta-v. When getting to orbit was a challenge, and getting back from the mun was still a long-term goal. This is what grabbed you into your KSP obsession, go visit what it was (even Scott Manley mentions in a recent GDC video with the kerbal animator that "kerbals made KSP take off while Orbiter stays obscure"). There is no reason to give up the modern game that allows you to put a flag on every planet, just don't miss the extra experience with the fun little game that was (hint: a great time to try this will be during the horrible interim when 1.1 drops (and steam updates) and before the mods are ready). * warning: you may need a dummy steam account. I noticed that it wouldn't let me download the demo since I already had "KSP". Also downloading directly from steam is what gave me .18. To download the 1.0 demo, I had to go directly to the Squad website.

That's weird. I'll have to look into this, as when I first read your post I assumed it was wrong (an independent body traveling around a mass has only a few options: all of which are described by conic sections. If it is on an ellipse it has to be orbiting). The kicker is that as Slashy mentioned, orbiting bodies don't travel at the same angular velocity, but by Keplar's laws. The idea of dark matter acting as irregular clumps of mass is weird enough, the idea of it acting as some sort of rigid body that drags stars along regardless of gravitational forces is something else. For those wondering, the easiest way to determine the speed of the stars is by measuring the red/blue shift they emit as they burn. I'd suspect that our understanding of the spectrum the stars emit is a little wonky before I believed that dark matter acted as a rigid body. I'd also wonder how much time those few physicists who are really good at tensor calculus spend trying to work such things into general relativity ("the ether grabs things and carries it along" sounds like exactly what relativity is supposed to solve).

Note that in 2009 Iridium-33 (an active communication satellite) collided with Kosmos 2251 a defunct Russian military satellite. There have a few (wiki says 9) other satellite collisions, but apparently the others involved dead satellites (I think a few active ones have been taken out by debris). Typically, both satellites and debris occupy certain areas, and have dangers depending on those areas. LEO: this is where satellites crash, and will continue to do so until everything is cleaned up. The catch is that "everything cleaned up" only happens for stuff with a periapsis that dips into the "atmosphere" (lucklily nearly everything in LEO has at least some "atmosphere", so eventually it comes down. Especially that wrench you lost on the ISS). Also note that both "equatorialish" and polar orbits tend to cross around here, allowing spectacular collisions like Iridium-33/Kosmos 2251 (which hit at roughly a 90 degree angle). [a bit higher than] LEO: One of the first US satellites is still up there, and probably will stay for a couple of centuries. If you don't need any stationkeeping power to stay in orbit, you should know that the debris doesn't either. Make absolutely sure such a beast can de-orbit. Not sure how many orbits use this range, the Molniya orbit periapsis I found was listed as 500km, I'm guessing that this will decay (slowly, that aposis is huge). Note that if just your aposis is sufficiently out of the atmosphere that it is in the "won't decay anytime soon region", your satellite is in danger of debris that has that as a periapsis. [GEO-graveyard] assumed safe (collisions won't kick stuff up into GEO). Obviously you don't want to put a working satellite here. GEO: presumably reasonable safe. The nature of GEO means that just about everything is in one tiny band that prevents the wildly different velocities that wreck havok in LEO. Satellites are still expected to move themselves into the graveyard orbit when they are done. Replacement satellites presumably want to keep station exactly where the last one was (although such an area is presumably big enough to make it hard to hit by accident, and it would presumably be tracking any known dead satellites anyway). The "good slots" are pretty much taken up, and you don't want to interfere with your neighbors.

The plan to send a VASMIR to the ISS was canceled. With such an engine, I would expect you could find a graveyard orbit that wouldn't decay (probably not the "official" GTO graveyard, but sufficiently above LEO). Note that since the engines planned required more power than the ISS could supply, lifting the station might require few/no crew (it would be fine for stationkeeping burns, but lifting a 400 tons is another story). Also managing to stay in the SLS program does little to convince me that they are beyond the powerpoint stage in bringing VASMIR out of the laboratory (where it does work). If I were building a whoever-prize cubesat to the Moon, I would certainly calculate how much mass it would take for a lunar probe to right the flag (covering it with a new colored film would just too complicated (although require less theoretical mass)). I'm guessing its just a little too much (and would blow any prize-craft's budget), but it would be a lot less than the Ranger's sent to the Moon in the early 1960s. The engineers for the Apollo mission that I knew have been dead for twenty years. Neil Armstrong was 38 when he "leaped for all mankind" and has died of old age. We are losing plenty of that information, and I can only hope that a good chunk of it was passed on to the next generation. I can't see how ISS could be considered "essentially squandered". It does what it was meant to do: give astronauts a place to go in space. While recent claims of "year in space" giving critical information for travel to Mars is highly exaggerated (basically insisting that the Russian data is NIH). Building the bridges needed for international cooperation is probably more important than anything else technically done on the ISS. The idea of using the ISS for deep space exploration is pretty weird. It would only make sense for crewed exploration, and then only by sending up crew-rated stages up on cheap non-crew-rated boosters (space-x and orbital-STK come to mind). You still pay 9000 m/s delta-v regardless of the means to get to LEO.

"Space is big. ... I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." Rovers are fun to play with, but you really don't want to be stuck with them for actual exploration. Generally, it is a long way between biomes, and a rover isn't the way to get there. If you must use rovers, try to get them at transition points between biomes (Mun is often a problem, rovers have issues entering/exiting craters. And too many of the biomes are just craters). If you are extremely lucky, you will find a transition biome between them (no idea how long it takes to find one if you don't just run through it).

I've heard rumbling of huge boosts to Roscosmos, but all google could show me (for recent years) was further cuts. I don't expect any more money (and further cuts) until the price of oil comes back up. While I'm not at all familiar with Russian politics (reading the biography of Sergei Korolev is enlightening, at least for old-school USSR politics), but yo-yoing the NASA budget tends to be a disaster. Somehow cranking up the budget always finds new places for congressional (and friends') pork just to do what NASA wants, but reducing the budget means protecting the pork and throwing away NASA goals (check the SLS and shuttle debriefing threads for plenty of examples).

The best examples of space stations at end-of-life I know of are Skylab (more or less unplanned deorbit) and MIR. MIR lasted quite a bit longer than expected, but was up during the fall of the USSR and doubtless lead to much uncertainty for the cosmonauts and insufficient maintenance. The reoccuring theme on any description of late MIR flights was always the threat (and often occurrence) of fire. If you've heard the old chestnut about NASA spending millions on a space pen (they didn't, it was spent privately) while the Soviets/Russians used pencils, MIR taught us why not to use pencils: graphite conducts. The graphite (or pretty much anything else in an aging space station) would float into where it shouldn't and cause a short circuit, with a fire starting later. Not sure what the total time cosmonauts took putting out fires (even if it was short, it was way too much), but it was a strong indication that the MIR should no longer be used. My claim about Skylab's "unplanned deorbit" was something of an exaggeration, there was some plans for a shuttle rescue, but obviously the shuttle was far too late to save Skylab. I don't think there was any serious plans about using the shuttle to send astronauts to Skylab (they probably could have saved it if they really needed further excuse to build the shuttle). According to wiki the last astronauts left supplies near the hatch and left the hatch unlocked, but officially wouldn't consider sending anyone else up "due to its age". One curious thing about the Skylab breakup is that it occurred 10 miles above ground (far lower than they expected). I'd expect the "spiraling in" pattern of an unplanned reentry (they had angled it up for maximum reentry length) would produce the smallest pieces (if least control over where it goes, I'd rather dump bigger pieces into the Indian Ocean, somewhere like where MH370 was expected to wind up). I'm guessing that without the "eternally at the powerpoint stage" VASIMR plans going forward (they have already been canceled), the only possibilities for the ISS are planned deorbit and breaking up and getting much closer to Kessler syndrome. It can't remain unmanned. It can't remain manned without either keeping the Russian section or replacing the Russian section. I'm curious if the ESA is picky about who owns the USA parts (assuming the agreements can handle a Russian exit in the first place), if the thing politically breaks up, you pretty much need to de-orbit it anyway. It certainly hasn't reached MIR-levels of aging, but such will happen eventually, and I doubt that any module as designed for much more than 2020. One thing that always struck me are the fans. Since hot air just sits there on the ISS, fans are needed to cool *every* piece of electronics (a fanless heatsink does nothing). The sound of the ISS is the constant drone of all those fans. Fans also are a common source of electronics failure. I suspect that as ISS ages, finding and replacing dying fans will be a common job for any astronaut on the ISS.

Are the delta-vs of each stage even vaguely similar? Typically, the most efficient sizes for you stages should be fairly close to one another (in delta-v, as mentioned already this will be exponentially increasing in mass), and that is one of the best places to start (another starting point is to double the mass of each stage). These are pretty basic tricks I've seen elsewhere that rarely get mentioned in kerbal sites. If your "final stage" is too massive, it shouldn't be that hard to break it into more stages. Note that adding another stage need not require an additional engine, simply using drop tanks can let you leave orbit on an intercept course, do a capture burn, de-orbit to land, and then drop tanks so you land with minimal mass. Adding drop tanks does fight with the 1.0+ (or FAR) aero model a bit (fairing might help, but can often be ignored, especially until that bug is fixed) but the overall gains are likely worth it.

I suspect that most of the vagueness was how the Jupiter flyby effected its trajectory. Considering the distance to Pluto, the error in distance for the Galillean moons (and the gravity the pulled the New Horizons with) was a lot bigger than any uncertainty where Pluto was. Pluto showed up fairly well (as a multi-pixel blob) on Hubble: they knew where it was. New Horizons was another story, and part of that was a SRB (final stage) that burned a bit longer than expected.

While all this is true, it is pretty pedantic to suggest that liquid oxygen is anything but an explosive. It might not be, but it can make virtually anything it touches an explosive (charcoal + LOX is a favorite industrial explosive. If the detonator fails, just wait for the thing to be a dud detonator (still dangerous) and a pile of charcoal (not so much)). For all the Hindenburg's ability to be remembered, explosiveness isn't a big problem of hydrogen (everything else is). I'm also guessing that building a SRB construction site near either Cape Canaveral (probably inhabited, extreme issues in digging a bunker) or Vandenburg (if there is an area nearby that isn't heavily inhabited, it will be) just aren't good places to build an SRB. They might do better if Spaceport America had a chance to take off (what were they thinking?). * I think Wallops has issues mostly like Canaveral. You would have to pretty far inland to dig a bunker, and anywhere on the coast is prime real estate. Considering I live in Maryland, it is embarrassing to forget that one.

Going vertical means you have full (or at least 90% due to decreased gravity in orbit) of your gravity losses the entire flight, including most of your circularization burn. It also means that your circularization burn is going to be at least the square root of the orbital velocity (assuming you punched through the atmosphere with another square root of to orbital velocity). You would be better off going somewhat sideways, and using something resembling a pitchover (gliding into an angle). From memory, the steering losses are equal to the cosine of the angle between prograde and the direction you are firing: in this case they are going to be huge. You still want a pitchover, and for roughly the same reason. Another question would be "is there a muzzle velocity that makes sense for firing SRB-based rockets into orbit? Instead of attempting to fire a projectile all the way to orbit, you would visualize a three stage (SRB-based) rocket, and replace the first stage with a supergun. Such an system wouldn't be remotely cost effective now (its only possible common mission would likely be ISS resupply, much like any other supergun), but it is likely to make much more sense earlier* than other approaches that eschew rockets at least part of the way (Skylon and others). * consider building a space elevator. Presumably the [carbon nanotube] "rope" could withstand arbitrary g forces, and you needed to launch a lot into space before you had a working space elevator. It might even work for chucking fuel into space (for large values of "if", such as a reasonably low cost gun, and really cheap SRBs (much lower size means easy transportation, dirt cheap cargo implies simplified construction [if it explodes, so what]). I'm guessing from the excess number of small satellite launchers and the lack of SRB-based solutions they use, building small SRBs don't give you enough of a scaling advantage (something I've seen here as a reason why you don't see many SRBs), and don't expect a quick and dirty SRB to be sufficiently cheap.

Er, yes. Presumably you would quickly turn from 45 (preferably steeper) to 90 as your velocity increased. That and that gravity seems to be about half of Kerbin's means you should be able to manage local TWRs higher than 2 or so (try for more). While it technically will be a gravity turn, it will appear a highly abbreviated one (of course you could say the same for Minmus, but a pure sideways course (assuming mostly flying over flats, you don't want to become geography) is close enough to not worry about any fuel being wasted).

The bulky "spacewalk" spacesuits or the orange jumpsuits worn by NASA types that aren't pressurized? Certainly the latter, I'd think that a spacesuit hanging around without gravity can get pretty big.

Not only do you need circularization, you also will have extraordinary difficulties trying to do anything resembling a pitchover (typically called a gravity turn in KSP, especially before 1.0). Presumably this could be done mostly by control fins (letting you convert vertical velocity to horizontal in a reasonably efficient manner). Once you leave the atmosphere, you better be going [nearly] horizontal (and obviously, you will need a bit more delta-v to avoid coming back to the atmosphere. Plus all the standard issues: full orbital velocity inside the atmosphere (I'm guessing that over 4,000m elevation is as good as you can hope for). Mind boggling g forces: 1 1km gun would hit 6400gs (best possible case). Basic guns are limited to Ve (the Ve of the Rocket Equation). Expect weird multi-combustion guns to get near orbital speed (Bull certainly wasn't stopped by this, but it makes things hard). Scott Manley has one of his science videos on this:

Note that in general this is right, but the specifics can get hairy. The big catch here is that if you assume the SRBs are providing >1 g of thrust (whatever you do, don't throttle the SRBs, replacing SRBs with liquid fuel is [nearly] always wrong). Assume the following rocket: SRBs provide ~1.25 of TWR, Liquid boosters provide ~.5 of TWR (and they roughly scale upward during flight, but maintain similar ratios). 1 g gets lost to gravity. The SRBs provide roughly .25g of vertical acceleration (even kickers rarely finish the gravity turn) with an Isp of 195s. The liquid boosters provide .5g of vertical acceleration (unless throttled down) with an Isp of 285s. The kick here is that while you may appear to be saving 33% of your fuel by using the less efficient fuel first, the SRB is wasting 4/5 of its fuel fighting gravity and the liquid rocket doesn't. I'd guess that as long as the ratio of the Isp of the fuels is less than (1-TWR), then things get pretty complicated. Note that the TWR increases as the rocket climbs, so eventually throttling likely becomes obviously efficient. I'd suggest experimenting by launching with and without throttling. I found no real difference, except the chance to botch my steering while adjusting my throttle, but that might have been due to my style of rocket design and launching curves.

For "the Martian", I've heard (yes, I need to read that book, as well as see the movie) that the trip takes less than ~2.5 months, so they easily have the delta-v (having the life support is another issue. Apollo certainly had the delta-v to afford "skipping off the atmosphere", but not the life support). I remember reading (around ~2000ish) about a GTO satellite that was out of position, so (after dealing with insurance) looped it around the Moon to get it into proper insertion (of course, that probably didn't involve much attitude adjustment, but did take a chunk of delta-v). No idea how much that effected the usable life expectancy (presumably it used the stationkeeping thrust), but it went from zero to non-zero.

One way to help fix this that doesn't require any cost or further unlocking of the tech tree (although I really love those AV-R8 winglets. Don't try high TWR launches without them.) is to simply stick the fuel tanks above the passengers (no FAA/OSHA/Health and Safety issues on Kerbin). Since the engine is heavier than the capsule, moving the passengers down should easily move the center of mass (with empty/nearly empty) fuel tanks should mean easily coming down prograde. Maintaining a small bit of reserve fuel (nowhere near the 10% space-x uses) should get you under the ~220m/s needed to release the parachutes. As far as landing horizontal, one way that works would be to only use parachutes along a single side. Two parachutes should be enough. Unfortunately, you probably can't afford an asymmetric rocket that small. Use symmetry to place to guide chutes (or just use what's already there) to place individual parachutes (no symmetry) just under where the old ones were, then remove the parachutes placed with symmetry. Then put your "real" parachutes on a stage above your "dummy" parachutes. Land with just your "real" parachutes (I have no idea if you can open your dummy chutes in time if two aren't enough. Note that groups of three should work better in that you should still float horizontal, and you only need one "dummy" parachute out of three. Sufficiently big rockets shouldn't have to bother with dummy chutes.

"Lightning Bolt! Lightning Bolt! Lightning Bolt!" While the above are certainly good arguments, I would strongly suggest the electrics as you pretty much need the ox-stat panel for anything (if you didn't you can still turn off battery power during your interception course, turn it back on for your orbital and possible descent burns.). Getting the octoprobe just seals the deal. Getting more science instruments is usually best, but in this case you would open up upper/lower space near Minmus, upper/lower space near Mun, land probes on Minmus/Mun (and if you are adventurous and willing to learn about transfer windows, probes to Duna and Eve). Also, you get the octoprobe which makes launching Bob up into orbit (or Minmus) and resetting all those experiments a snap (because the octoprobe gives you SAS). Getting one more instrument would be nice, getting to use all your available instruments on all available biomes is priceless.