wumpus

I can't believe that nobody has mentioned this (being the science and spaceflight tab), but real life launches pitch over as soon as possible (not sure if this applies to crewed flight). Not for flight optimization purposes, but so the rocket doesn't crash back on the pad during a failure like the Anatares recently did. In KSP my initial pitch usually depends on how much control authority I have. If I need control winglets, I can typically wait. If I have a lot of TWR, I need to pitch early (I will lose control soon enough). If I am relying on the capsule (or worse, octo) for all my control authority (and have a relatively large rocket), I need to pitch as soon as possible to get the thing to move at all.

The really surprising thing is that the biggest benefit to altitude is effectively less "back pressure" (we see this in KSP as more thrust and thus higher Isp) as air pressure goes down. An ideal vacuum nozzle is infinitely long, but real nozzles have to be chopped off at some point (although some are known to slide into position for an extension that interferes less with staging). Ideally you would launch at a point that would fit your truncated vacuum nozzle, but I suspect that "near enough" will have to do (so your wings and turbofans still work). Less aerodynamic drag can't hurt, but it turns out not to be as important as the air clogging up the nozzle. Free altitude is effectively irrelevant, although if you compute the altitude's "delta-v", it might not be that bad (considering it counts for the fully fueled rocket), but both that and the few hundreds of m/s from the jet won't begin to justify the costs. If you are launching a satellite into GSO (or otherwise really want the thing around the equator), then choosing your *latitude* is even bigger. But I doubt that any LEO satellites need to be in equatorial orbit.

Any idea on the reflectivity of gold-leaf? Would Na/Li/Be work as "metal-leaf" in space and have the reflectivity/g needed? Also make sure your sail is "reflective" on each side (or at least non black/absorptive), that "white hot" energy preferentially radiates from the darker side. You still aren't getting anywhere near relativistic speed (the W/g calculations won't change), but you might get to the "we might even know we launched a spacecraft hundreds of years ago" stage when it gets there (or more likely the probe that *was* sent via relativistic speed a few century's later detects it and they have to re-write history not knowing how advanced [or not] 21st century tech actually was).

The reason this works in KSP is that Kerbin needs ~3km/s delta-v to get into orbit. Earth needs ~9km/s to get into orbit. Kerbal jets go faster than "real" jets, but the big reason KSP SSTO is a thing is that jets can get so close to orbital velocity on their own. The SR-71 blackbird had more delta-v than any other air-breathing aircraft. It also had a prototype means of launching a drone/rocket, but that was canceled after one death in two flights. Even so, 1km/s is not all that significant when you need 9km/s delta-v. The X-43 is my favorite example of at least a possibility for this type of thing. The important thing to remember is that while the X-43 set some amazing speed records for maintaining air-breathing flight, it couldn't significantly accelerate at mach ~9, and I doubt it could get to mach 6 on its own (from anything less than mach 3, and even that is iffy). Look at a picture of it: tiny little aircraft, massive solid rocket booster to get to speed. KSP's favorite youtuber explains the benefits of mountain launch (oddly enough, altitude *does* matter for air-launch although not in the way most people expect). https://www.youtube.com/watch?v=RsbDRDFVObE

Betteridge's law of headlines says no. This is pretty much the same reason NASA tried to put a teacher in space. It wasn't a good idea then, it is worse now. If you are mass limited, look for a small enough woman (NASA required all astronauts [at least until the Shuttle] to be under 6 feet tall (roughly 180cm), although some of them were pretty stocky).

I doubt NASA would bother handing out the plans (although you can try asking the team that printed it, it is probably technically publicly available [but you might have to license it from an agency tasked with maximizing profit]). You might find them in that UofM dump (there was at least one other place that has a copy now, but I have no idea where it is), but I suspect it would be the proverbial needle in the haystack. If these methods are more precise than what you could do with 1940s slave labor, I suspect that pressure fed rockets to orbit (or even the karman line) are obsolete. Is there enough knowledge in this forum to even bother with a new thread on amature turbopump-driven rockets? Plenty of us (well I did, but a few others pointed out how it would cause waves through the pipes that turbopumps wouldn't like) thought "how hard could it be" with respect to asparagus staging, but it didn't take that long for Spacex to abandon that idea.

Before embarking on this course I would suggest saving, jumping to a higher via hyperedit and checking how much delta-v it takes from an orbit that allows a ~50 minute burn. Add the delta-v needed to get that orbit and make sure you have the required fuel (if you built the spacecraft based on the "subway map" numbers, you might be in for a bit of a shock). In any event, you are almost certainly going to need multiple burns simply to get up to the orbit needed for a final burn. A burn of 1-2 minutes on each side of periapsis (and/or the initial "burn here" mark) will quickly raise you up to a longer orbit (don't make it too long, you don't want to significantly change your trip to Duna) [hopefully you can deal with 2x physics acceleration. Be careful, big motherships don't like much physics acceleration]. Once you are ready for a final burn, [save game] raise your PE (to allow for a longer, more accurate burn, if a less efficient one) and create another maneuver node. [Check your fuel reserves and be ready to reload with a lower orbit]. Hopefully it will be much less than 50 minutes, but you should be able to now handle even that much if needed. PS: thanks to the difference in escape velocity vs. hohmann transfer, you shouldn't have much of a problem doing this Kerbin->Duna. You can start with up to 900m/s on Kerbin (don't go that high or your orbits take so long they throw off your window calculations) and only need ~200 m/s for the final kick to Duna. Going to Jul means an extra ~1000m/s from Kerbin (according to the subway map, which assumes a burn from LKO. Don't expect to be able to burn 1000m/s efficiently from there), so the final kick needs as much delta-v as all previous kicks combined.

Unless it is cheaper than starting with the CNC, that only works for the available surfaces (there will likely be exceptions, but since the main point of printing an F1 engine was to get the plumbing without all the difficult and critical welds, you don't get to CNC the insides). Hopefully your 3d printed plumbing doesn't have significantly more resistance than NASA's printer.

How fast does the spaceplane go on your Kerbin? I think it would be possible to get 4km/s delta-v (plus drag/gravity losses) with current Earth tech in a SSTO (1km/s jets are "known", 2km/s have "been done experimentally"), but it would be close. It also makes you wonder about "Goldilocks planets", they apparently need a heavy iron core to achieve 1g if you need to go up and down very often. Scaling a x5 Earth would likely mean a ~20km/s orbital delta-v: not an issue for an star-traveling civilization colonizing the planet, but if anything happened to the civilization they aren't getting back up.

https://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf (the above are NASA's ideas. I think they have formally abandoned nuclear power. To many this might as well be abandoning Mars itself). The ship to/from Mars is likely going to look a lot like the ISS. That is the best/only known way of building large things in space where a crew of 6 can live for months (look up "launch windows" for a good explanation why it takes ~2-3 months to get to Mars (regardless of the fuel used) and you aren't coming home for 2-3 years. I think that is well covered in the link). The fuel used is either nuclear (and needs a lot of hydrogen heated by the nuclear reactor and thrust out like a rocket. This is by far the most efficient means known to get humans to Mars) or a mixture of liquid methane and liquid oxygen (hydrogen is a possibility, just expect a lot to leak out while spending years on the surface of Mars). Getting up/down on Mars is pretty straight forward. It is much less massive than the Earth, so expect to need a smaller rocket to launch land. The big catch is that landing will stir up a cloud of engine-damaging dust: the whole point of Curiosity's "skyhook" was to land without this issue (I don't expect manned vessels to use a skyhook). Something like Spacex's dragon (only a bit bigger) might work. Most launch/land plans bring fuel but require producing oxygen on Mars. Making sure this happens could easily lead to a heap of drama. No oxygen = a grave on Mars. The only real "new" info not in the NASA link are: Spacex likes methane, it weighs more than any suggested fuel but works well with their rockets. Curiosity landed with the spacehook. It is one more way to land. Preparing oxygen on the surface of the planet seems to be taken far more seriously.

I suspect that "stealthy orbital insertion" on the Earth might be unlikely. My "most stealthy guess" would be connected to a meteor that would burn up in the atmosphere, but the thing would break up and eject a "probe". Obvious Gotcha: you can't create an orbit by aerobraking that won't quickly decay without an obvious burn. That includes any means of ejecting the probe as well. Possibly, it could have a sufficiently eccentric orbit that angling the (conveniently colored) rock in *just* the right way will allow it to act as a solar sail in an extremely eccentric orbit and raise the perigee enough to maintain orbit. This coloration would be the means for any maneuvers afterward, but they would mainly have to mostly rely on gravity-chaos to avoid tracking. No idea if you can have a sufficiently discrete solar panel (perhaps disguised with a light rock coating over it) and a nearly "magical KSP" gyroscopic alignment system (you really want to avoid using RCS to desaturate your gyros. That's a giveaway that you aren't natural). I'm guessing that in any society where anyone would build/launch such a thing, all bodies orbiting a planet (especially anything inhabited) are assumed non-natural and tracked. You aren't going to do a stealthy insertion.

While the most efficient configuration is complicated (there is no trivial way to optimize it), a good starting configuration is often equal amounts of delta-v from each stage (another good starting point is each stage half the mass of the previous one). And while the upper stage should typically use a very small engine, it doesn't always follow that the fuel&oxidizer tanks have to be tiny. It certainly helps to have a small dry weight (including payload), but you need the wet weight for delta-v. Don't forget it is far easier to get delta-v without the dry weight of an additional stage. Don't forget that the Falcon9 first stage provides a lot more delta-v when it isn't coming back to land (and the first stage is considerably more powerful with the 1.1 and later models that started trying to perform a powered landing).

While "just print a F1" might seem unreasonable, it likely is a valid strategy for trying to get into orbit. Back when Moore's law was still enforced by physics and economics, there was alleged to be a "slacking law" that said any program that required more than 2 years to run could be accelerated by simply doing nothing for n years and then running the code on a computer with the advancements made during that time. I could easily imagine one group simply waiting for availability of the class of printer NASA* used to build their engines could beat a group using our various pressure fed liquid and hybrid rockets to orbit. The problem is that once you posit such machinery, there is no longer much point to this thread. I'm also of skeptical the rate of availability of such printers being available to the public, although there have been print shops willing to do work far beyond consumer printers for at least a decade. I'm curious what is available now (don't forget to check your local machine shop for more traditional competition, at least where topologically possible). The importance of forging and the cost and availability of subtractive (CNC milling) vs. additive ("3d printing) shouldn't be ignored. While 3d printers get more press and appear magical at first glance, CNC milling devices are the actual workhorses of prototype and low volume (and sometimes high volume if such precision is needed) production. I'd expect them to always be able to make a superior product for anything topologically possible to produce (even if this requires blasting bits off with a laser). One catch is that plumbing is obviously topologically unsuitable for milling (and this not only allowed improvements in the F1 design, it also made things possible without needing to teach welders 1960s welding skills). I'd still expect that things like turbopumps (and presumably housings) be done by milling. * I'm not sure they contain actual engine blueprints, but the University of Maryland received a "complete copy of all NASA records from [~Apolloish era- ~shuttleish era] around 1990. They are probably in the technical library unless the US archives (on campus) snagged it when it was built. Since 9/11 NASA campuses (at least the one I've been on) are mostly closed to visitors and it might be easier to get to UM (a subway ride from Washington DC).

It would still take a long time to create the spacecraft that can latch on to an asteroid and either bring the whole thing back or smelt it onsite. Also expect a year or more to get there and several years back. It would still have everything smelted and in ingots long before an enrichment reactor was in space and fueled for operation.

The amount of hypergolics used in modern rockets are pretty small. On the other hand liquid oxygen has a tendency to turn everything it touches into an explosive (charcoal makes a high explosive). If you tried to launch a Proton out of KSC or Vandenburg I would expect a bit of an outcry, and I have trouble believing that the Russians are still launching those things. Of course, the usual "public panic" about toxic substances always ignores the dose. Ignore the dose and any toxicity report is mindless babel.

My understanding is that there are plenty of nickel asteroids, and likely a platinum or iridium asteroid that can be found (those are typically suggested when mining asteroids). Certainly plenty of things heavier than aluminum (or whatever the heaviest bit of moonrock is), although you have to find asteroid. Anything flung into space via similar action would have large chunks of heavy materials. I wasn't thinking: smelting is trivial, especially compared to the energy source needed to move it around. Enrichment is the problem (assuming uranium is out there, it is still a big step up from nickel and iron), which is why I knew such a program would need one (fueled) nuclear reactor to enrich the material as it is mined and/or lifted to orbit. This method would be ideal for dealing with spent fuel rods (cooled down "correctly" or simply ejected and sent back to base). I wonder if it would be possible to ship up low level U238 and enrich in orbit/L2/wherever (and ignore the asteroids until they are mined for other reasons)? I'm guessing this would have all the same political issues, but it seems sad that such would stop a possible real interplanetary space program.

1.3 is non functional for me. Reverting to 1.2.2 is fine. I was away long enough that I couldn't use old saves in 1.2.2, but a new game fixed that. This seems pretty rare, but since I didn't want the language packs, once things worked in 1.2.2 I wasn't interested in fixing my 1.3 issues (although I'll likely try 1.3.1 to see if that works). Last I heard, RSS/RO works with 1.2.2 only. It is another reason I am happy on an earlier release. [Edit: the above may have been due to mods. I upgraded to 1.3.1 and had similar issues, then moved all mods from gamedata to a safe directory. Then 1.3.1 worked. I suspect 1.3.0 would have worked with similar treatment (note that my saves were too old to work with 1.2.2, so I expect the mods were pretty old).

Any guesses on the availability of Uranium or Thorium in the asteroid belt (like a large rock that can be trivially smelted to one or the other)? You would still need roughly the fuel for at least one full burn and maybe more, but the idea would be no more fuel flights. This is more a "decades out" idea, but the politics seems to be going away not toward this type of thing. Since step 1: build an ion system to find an asteroid and bring it nearby (L2?) is more or less within modern tech (ignoring failures in latching onto comets, and no tests on asteroids) it might be a good place to start.

Remember that each of these things has a high energy cost that is essentially stored in the target as its new phase. Most military lasers are only interested in blasting an arbitrarily small hole (however well they can focus*) on a fuel tank to destroy a missile. They have massive power and aren't remotely capable of digging a deep enough hole to cause a crater. I suspect nearly all craters made military action involved buried explosives (probably a shell going too far and burying itself, then immediately exploding. Or perhaps exploding sometime in the next century, see the "iron harvest"). Dropping a solid bullet is pretty inefficient, and only done to minimize blasts (I think the US Air Force has dropped guided blocks of concrete from B-52s to minimize nearby destruction). * make the pulse short enough and you don't need tracking. And anything in this power range is definitely pulsed.

I'd expect that you can drink distilled water all through a shuttle-length mission (but you never would because you would be carrying drinking water and won't bother with scavenging spent exhaust or similar). A flight to Mars (and surface stay) would be a completely different matter and expect to use reverse-osmosis and distilling (the RO filters I've seen only filter half the water at most, cascading them only would go so far), and presumably add whatever minerals you would expect after all that.

Ouch. And I just realized that Vandenburg* is a secure military facility, so I think you have to be a US citizen to be even considered to be on the grounds for a launch (I've joked that the only "weather" it gets is smog. Depending on the season that is probably close to the truth). Is there any "expect a rocket launch to be clear" season in Florida? Guiana Space Centre is possible (and presumably closest to Harvester's homeland, although I don't know where he lives now). Even in the winter (where freezing kerbalnauts might want to visit the tropics), I doubt you will get many to show up. * I think Wallops is Navy, but it is pretty low profile. If Orbital-ATK isn't launching to ISS, I don't think there is anything big going up there anymore.

For higher TWR launches, it often helps (even more than usual) to angle the rocket in the VAB. Of course, control of this gets iffy so expect to either revert a lot or ignite your stages before releasing the launch clamps. One thing to remember is that people aren't always clear on how long a rocket maintains its launch TWR. A two stage rocket using a SRB first stage will gain TWR faster as it climbs than most rockets, while a three-stage (or more) rocket will typically gain TWR much more slowly than most two stage rockets. Adding hammers might wildly increase TWR, but that TWR won't last long. Typically it makes much more sense to use smaller engines (especially using less SRBs to wrap a first stage) than to throttle the engine or set SRBs to less thrust. Don't forget that KSP is an extremely flexible game (note the train enthusiasts on this site), you should consider being flexible in your rocket design. A tall, ungainly rocket that has great difficulty turning (read losses control the moment you turn in a thick atmosphere) might be well off taking an extended old-school trip straight up before turning. Such a design (assuming your noodle can handle it) would be more efficient with enough kickers wrapped around it for a TWR at least 2.0. It won't be efficient, but it might be one of the few ways to get it in orbit.

Pick your (IRL) rocket launch. Said rocket launch schedule should ideally be as hard as possible, while still being a sufficiently high profile launch to draw a crowd. That said, the best I could likely swing in the foreseeable future is a Wallops launch, and that will never justify a kerbalcon. I still have my doubts about just how big a crowd KSP can draw on its own (it isn't like WoW or Quakecon), especially after the inevitable mission scrub (presumably the show would have to go on). [political speculation about Squad vs. customs scrubbed by poster. Which might be why it hasn't happened, considering this type of thing was their original business].

Then by all means just print an F1 engine. It (both the original and printed edition) are proven tech. It certainly is more likely to get into orbit than any other suggestion so far. You might also want to look up some brand new technology called "forging". It makes metals stronger than if you simply melt bits of pieces together (although not quite needed for said printed F1 engine, it will still make for stronger metals of the same material/mass).

I suspect it is more a matter of ejecting the core to avoid cooling issues. Running "exhaust mass" to cool the core is pretty disastrous for Isp, and I'm guessing it needs more cooling gas than the mass of the core. My guess is that any modern design that cools down the core for re-use is doing so to avoid the political issues of lifting up more "fuel rods". Turning a NERVA off is a pretty hard problem: ejecting the core is an easy solution.