wumpus

While this is mostly true, not everything has to be "one rocket: one mission". LV-Ns are often ideal tugs to carry things around a system. High delta-v helps, although a smaller tank might also help (with some constraints about the lifter having to refuel the tug). To be honest, my favorite tugs were never designed as such, there just were more useful "up" than returning them for scrap.

Now that I think about it, Micheal Collins mentioned* that you couldn't see out of Apollo during launch/[atmospheric] ascent. I'm pretty sure the heat shield covered the windows and was removed along with the escape tower once they were in space. *"Carrying the Fire" basically an autobiography/insider's view of Apollo and Apollo 11 in particular.

The procedure for astronauts before a flight was to breath pure oxygen for several hours before a flight. This is why you saw them carry boxes on their way up to the rocket. Micheal Collins mentions (in "Carrying the Fire", an excellent description of the Apollo program and Apollo 11 in particular) that he thought he had a slight case of the bends during his Gemini flight. It was significantly less during Apollo, presumably he started de-nitrogenating earlier. If you needed an atmosphere or so of pressure in the command module at launch (presumably helium would have worked as well, the astronauts were breathing pure oxygen) it didn't turn out to be that big a deal (although venting it out must have cost a bit in the oxygen supply).

Apollo hit max-Q at .8km/s or 2900 km/hr. Not exactly blackbird speed, but it should be causing heat issues for the command module. Depending on how you would term "exit the atmosphere", it was probably going twice that when it left. Also, Apollo lifted off at something like 1.1TWR. Falcon 9 FT (and later) launch at 1.3+, so expect them to have more issues on ascent (the shuttle flew off the pad at TWR=1.26 but didn't seem to match Apollo's speed in the atmosphere. Maybe I'm misreading the poorly labeled graph). https://upload.wikimedia.org/wikipedia/commons/2/2c/Apollo17_Ascent_Trajectory.pdf https://www.nasa.gov/pdf/466711main_AP_ST_ShuttleAscent.pdf

NASA (and the space industry in general) has really weird ideas about "development" vs. "production". I wonder how long it takes Elon to go from "Tesla mode" (they have produced and sold even tens of thousands of model "X") to Spacex mode (where 8 is a long production run).

I thought we were discussing the second stage of the booster. Cryogenic isn't an issue there, and it will certainly use them for any burns still done in vacuum via the merlin engines. If you want to land the Dragon[2], you are already insisting on hypergolics. You will also expect to use hypergolics for the second stage of the booster, but only because the merlin engine won't work at sea level.

Isn't Kestel pressure fed? A Kestel needs its own tanks that are far heavier than a super Draco. This really looks like a job for a Draco. If it were heavier or needed more kick, I'd recommend adding SRBs, but you still need something for control and enough Dracos for control (of a Falcon upper) are enough Dracos to land. I'd imagine a raptor upper stage would land on Merlin engines, but the Kestel doesn't seem to fit. If they were playing KSP, they would likely be using Ruthorford engines, but this isn't KSP.

It has to be roughly as powerful as the onboard engine throttled down to limit (40%?). It can be light, but I'd still expect a 7 second SRB to be a lot lighter than a fuel engine + fuel. Also I think its "deployable wings" would be similar [probably identical] to the [first stage] Falcon's paddles. From what I understand, even scaled composites has given up on deployable wings for re-entry (they might recommend such a scheme for the first stage booster).

The problem with that demo is that while it captures the spirit of the game, it doesn't say much of anything about the actual gameplay. I'd recommend sticking to the demo: if you can't get excited about doing rocket science with lego rocket parts, this game isn't for you.

During the Apollo program, there was a plan (DoD, not NASA) to build manned spy space stations. It was canceled for similar reasons.

Apollo couldn't throttle down those F-1 engines, so shut one off before max-Q (I know it shut one down, so I'm assuming before max-Q). Most of the reasons for a hot launch involve SRBs. I can't imagine using a mainsail for such a hot launch (mechjeb might do something funky like launch at 1.8 and throttle down before breaking the sound barrier, but I don't have the dexterity for it. You still wind up with an overbuilt rocket). You can also get the wrong ideas about launch TWR (for kickback first stage) by launching straight up (and using apogee to determine delta-v) . Since you need horizontal velocity instead of vertical, you will get the wrong results. Many of my designs have a lot of thrust on the first stage (kickback-based) and wimpy second stages (LV-909s, Poodles, maybe even LV-N). If I'm "launching hot" it isn't because that would be best for an ideal second stage, but because it works with a second stage that takes a long time to circularize. If you hate atmospheric effects, why aren't you following the "standard" launch at TWR=1.1-1.3? It seems to work for most people.

Nope. The "best" is clearly the LV-N. It's also the "only" as the others are "liquid fuel + oxidizer engines", while only the LV-N is liquid fuel only (jet engines obviously need oxidizer, even if they don't have to carry any). Of course if you insist that oxidizers are implied or simply allowed, that does open things up a bit. /s (I'm quite smitten by the LV-909. Lots of Isp, and cheap/low tech. But I obviously can't claim its the best for many things).

SRBs can be heavy, but if you only need them for a short, high thrust burn they should be wildly lighter than carrying a rocket motor for a short burn. My kerbal solution would be SRBs (two or three arranged around the center) that would be constructed to match the trust profile you need (KSP gets it wrong: having multiple levels of thrust for SRBs is easier than on liquid rockets. The difference is you don't get to change the thrust level in flight). Hopefully you the center of mass is high enough you can mount them so they are still firing after it lands (obviously TWR<1). Then add some hybrid rockets (easy to make throttleable) for actual control of the landing. https://www.youtube.com/watch?v=glEvogjdEVY If my eyes got it right, the landing burn was 6 seconds. That really screams "use a SRB" (assuming the main rocket is right out), although you will need something else for fine control.

Spacex has been claiming this, with the usual Elon schedule. I have my doubts, but the second stage should come down with a lower terminal velocity (only one merlin engine instead of 9, same cross section, same rough shape). One big issue is landing the thing on a vacuum-optimized engine: I have no idea how much thrust that thing puts out at sea level. They seemed to have shelved the whole idea indefinitely and recently brought it back. Possibly they found a return trajectory that they've managed to get a few to survive (even if they never bothered with the other burns and fin control).

Hint: if the retirees outnumber the workers, it is not a good situation. Declining population doesn't necessarily mean good. Although robotic care for the elderly might be interesting.

Now go and check Japan's population. Individual control of reproduction isn't making an ideal population, is it (Japan being weird as usual, didn't legalize the Pill until 1999. Presumably other means were used to crash the population). Another example would be around the neolithic revolution. Basically the old "hunter gatherer" is a far superior lifestyle for 99% of the population. Unfortunately, the "good" areas can support enough population until they use them up, and then they have to move on to marginal areas. And things get worse once people start farming (and defending) the best areas. For rock-bottom tech, the ideal human population is extremely low. For high tech, I haven't a clue (you need a pretty big population to allow for the amount of specialization our economy requires). Zero growth doesn't just mean avoiding overpopulation. Negative growth is just as bad and can be preferred by couples.

Good luck. Remember that population levels are the classic example of how exponential grown/decay happens. Long term, the growth level needs to be zero, but people get rather testy if you make decisions about their reproductive freedoms for them. Also, if you are moving humanity: why not Trappist-1? Change a billion year lifespan of your topopolis to a trillion year (I doubt any known material actually lasts that long. But if you are going that extreme, why not go for the long tick).

Pretty much the point of Robert Heinlein's classic "The Moon is a Harsh Mistress". At one point the targeting computer asks for a new target. The operator asks why. It points out that Cheyenne Mountain is now Cheyenne Plain and continued bombardment would produce Cheyenne Crater (I think this was written in the brief moment that Cheyenne Mountain was considered impervious to atomic attack). This mainly worked because one side (The Moon) held the high ground and the Earth didn't. The catch is that between any Earth nations (or really any two or more enemies in the same gravity well), it is quite possible that any diverted asteroid would be detected, followed by a tug-of-war where various nations try to impart enough last minute delta-v to drop the asteroid on an enemy nation (or at least not their own). Since the delta-v to divert an asteroid to Earth >> the delta-v needed to change the location on Earth such an asteroid will land, it seems a dangerous strategy. This would make a lot more sense for two planets (in the same solar system) attacking each other. Also consider the issue of having a large body scheduled to collide at a later date: what do you do when your enemy surrenders?

Note that these "optimal trajectories" on airless worlds, especially Minmus tend to be steeper than you can steer a retrorocket. Anybody build a minmus lander in the spaceplane hanger (I think Scott Manley did a long time ago, presumably versions have changed too much to count)? I'm guessing that landing on the flats as a runway is ideal. I'm pretty sure you can't steer a tail-sitting lander sideways fast enough on Minmus for an ideal launch (and thus can't do an ideal landing either, even if you were Jeb himself). Of course, this only works on Minmus (and the flats).

For me, it mostly depends on the TWR of my orbital-insertion stage. I often use some pretty small engines (LV-909, poodle on significantly larger. I'll even use LV-Ns (expect a stage in between) if I'm using them to leave Kerbin). Doing this often means a higher TWR than 1.3 (if it takes more than a minute to circularize, you probably need TWR>1.3) or more stages. I won't argue that this is actually more efficient than a 1.3 launch, the following link pretty much blows me away (and they launch with low TWR). One reason I stick with low-TWR insertion stages is I want to keep using the same stage/engine to leave Kerbin (not an issue in the challenge). If you haven't already downloaded Kerbal Engineer/Flight Engineer, go do so. The critical things you need to watch in flight are apoapsis and time to apoapsis (they can be seen in map mode after minimal upgrading, but this often requires keeping the mouse on them. I'd rather slap KE on all my ships. The two easy ways to do orbital insertion are: 1. Create a maneuver node at AP. Burn like any other burn (you might delay the burn with experience). 2. Use KE (or the map, but at that point I'd just create the node and be done with it). Burn at 1:00 before "time to AP" and burn until "time to AP" starts increasing. Repeat at :45, :30, :15, and then finish around zero. The point of my post is that a minimal speed for ascent in the first stage requires a maximal TWR in the second stage. The way the rocket equation works, you can typically afford to make Isp of the first stage much lower than you can the second (and good Isp typically means poor thrust). I really don't recommend going for a minimal ascent speed.

The delta-v isn't much of an issue, but navigation is pretty impressive. I think Mariner and some Soviet missions to Venus happened (or were at least launched) while the Gemini program was still going on, so it isn't exactly a huge technological hurdle. A number of probes have been lost even before landing, so the trip isn't exactly trivial.

Less likely than any individual satellite getting taken out by the combined crush of all other satellites orbiting the planet during any specific hour. Way less, considering the ones that crash are almost certainly in LEO and the GSO birds are vastly further apart (sure, there's always the difference in the size of Apophis vs. most satellites, but I suspect the ratio of Apophis vs. a regular satellite isn't quite as big as the ratio of LEO satellite spacing vs. GSO spacing). Don't worry about it.

Ok, I expect it will fly. Now the real question is if it will ever launch a real spacecraft or find any other worthwhile mission?

The difference here is that unlike the typical EA scenario, Squad goes back to being a marketing company. It might look the same to us, but hopefully plenty of Squad will remain. One of the issues with capitalism and franchises is that you it is quite possible to extract too much out of a franchise too fast and kill the franchise. EA seems to believe that this is the more profitable means, and plenty of other companies follow a similar path (see movie studios). To be honest, I suspect that Squad has been following the various "KSP sequel" threads and has yet to come up with a workable sequel idea. The DLC idea* makes sense, and I have to wonder how they work with/around KSPEDU (I seriously hope this doesn't interfere with RO. I'm going to have to create a bunch of zip files with "complete" sets of mods and KSP editions from here on out. Good to be hopeful, better to be prepared). I really wonder if TT really knows what they are doing for KSP2/Kerbal "whatnot" Program or just sees a wildly successful early access and assumes more money will follow. Guess who publishes the *other* big Linux game, Civ 5? Personally, I dual boot to windows for my gaming (I typically lose half my resolution keeping the fps similar in Linux), but I'm aware of what I can play in my Steam list, and mostly it is KSP, Civ 5, and TIS-100. Wierdly enough, I think I sank more time into TES:IV oblivion than I have into KSP (weird, I know). I think most of what you are experiencing is simply rose-color glasses. Also, just because we weren't forced to search out every nook and cranny of Cyrodill doesn't mean we didn't. We just had the option to do our quest or go exploring. Also the character progression was simply broken, and the complexity wasn't an excuse (of course this is a bit specific to Oblivion, while Morrowind has optimal leveling, it isn't quite as critical). Jumping off cliffs/bridges to improve acrobatics or having your feet gnawed by rats to improve armor skill simply isn't fun gameplay, and it was all gone (or at least unnecessary by Skyrim). Yes, Skyrim was still a bit of a letdown, but only because I had already tasted The Elder Scrolls. I've bought Morrowind, but can't get myself to really get into it. The only real point to this (other than to counter this rather common argument) was that I expect the old hands will have similar ideas about KSP, and won't really enjoy KSP2 the same way the next Kerbal generation will. But don't expect to sell them on KSP (especially if KSP2 is full VR and KSP is stuck in Unity).

Chained refuel doesn't effect the rocket equation. And if you plan ahead and use ions to move chemical rockets into position [a great idea for less expensive trips inside the solar system], that really only works for values less than the Sun's escape velocity (which could presumably be done now with chemical rockets, especially if Jupiter is in the right position). There are various 4-figure Isp rockets in various labs. Getting Isp much higher doesn't make much sense in the solar system (things like low TWR and power requirements are overwhelming once Isp>>1000) but they are out there and exactly what you need for interstellar travel. The general claim is that Orion was expected to get to roughly .1C if used for interstellar travel.