wumpus

According to Robert Heinlein, there were similar movements about not letting any footprints spoil the Moon. Consider it rule 35: For any action, there is an equally reported on protest.

The only real advantages a monopropellant has are the obvious ones: only one turbo pump (big) only one fuel tank (small). The dissadvantages are pretty huge: ISP. I wouldn't be surprised if a pressure fed NO2/"rubber" hybrid motor works better overall than most possible monopropellants. Note that there are a few RP1/LOX rockets that share the turbopumps: the density of kerosene is close enough to LOX that they can effectively be 1.5 turbopumps (or less. I know pretty much nothing about turbine design). Once this is possible, it doesn't make much sense to use turbopumps with weaker fuels.

The problem isn't the undentonated bombs going off (although anything that scatters plutonium* is nuclear proliferation issue). It is more the entire energy invested in the Orion coming up crashing right down. Ordinary rockets do have the threat of all the fuel exploding at once (oddly enough, while SRBs are feared due to their tendency to "explode", this isn't really a danger for them). The difference is that an Orion will likely weigh as much as a battleship: the shear mass and velocity of all that coming down is the danger. If it took n atomic bombs to get it up, it is coming down with the force of n atomic bombs. Note the [fallout] analysis is from George Dyson's book "Project Orion: The True Story of the Atomic Spaceship". I'd assume that it was being more than fair to his father's space ship. * as far as I know, the Pu needed for a bomb and the Pu needed for a nuclear thermoelectric generator are two different isotopes. The Orion obviously needs the scary ones.

A few notes: The demo will tell you all you need to know if you need to play this game or not. Play that, then you will know. The Scott Manley "career mode for beginners" uses a roughly current KSP build (1.0.4, I think). It has 8-10 hours total, which will probably reduce the time it takes to get to munar bases by at least 8-10 hours. Just don't make a habit of watching all the other videos or you will find little time to play KSP. https://www.youtube.com/playlist?list=PLYu7z3I8tdEkUeJRCh083UT-Lq5ZIKI75 Career mode has it's problems. Consider sandbox mode, or at least running a sandbox game beside your "real game" to try things out. Quick hint: getting to space isn't that hard, but surviving the way down is another story (best guess is that getting to a 45 degree tilt on the way up will give you a better chance of air braking to survive). Minmus is probably easier to land on than the Mun. Sure, its further away and at an incline to boot (one of those nasty things you need to learn, it is far better to launch on the right incline than try to fix it when you are up), but the landing is *much* easier. Just aim at one of those big purple "seas" and you are done. It is easy to crash on the Mun when you are looking for *anything* that is somewhat flat. Note that in career mode I don't think you can get a contract for Minmus until you land on the Mun. Try Minmus in sandbox using only the parts you have unlocked in career (you might need to upgrade your base as well, but that typically isn't a problem. Just don't run so low on cash you can't make more). Don't overdo career mode. I got pretty burned out doing endless "launch yet another satellite" and spending way too much time keeping costs down (if you want reuse, use a mod. Don't try to get your booster in orbit so you can land it for reuse).

Note: In the almost certain case that "the EM Drive" doesn't really work, you can always build an EM drive by firing a laser/radio/EMwave of your choice as a rocket propellant. Photons have mass and momentum, you can use them as thrust (you can also use a ground-based laser and us that to push up a launcher). You could also rig up a cyclotron for arbitrarily high ISP. Note that such a thing would have insignificant thrust, so presumably would be on a multi-century sleepership and wouldn't be started until the ion thrusters ran out of fuel (and then run for a few centuries). Or maybe you just wanted something that would take a Voyager record into intergalactic space (after a few millenia).

The minimal requirements for asteroid mining involve: Locate a largely platinum and/or iridium asteroid with an orbit that gets "pretty close" to Earth (I'm pretty sure a few candidates have been found). Build a "miner" that can latch on to said asteroid (harder than it sounds, ask the Rosetta people) and have an ion thruster capable of an Earth transfer and capture. Launching said "miner" (megabucks). Fling said asteroid into a large shallow portion of the ocean, Antarctica, the Sahara, or some other place you can both safely hit with a returning asteroid and retrieve what's left of said asteroid. Note this may involve paying large bribes to change existing laws: as far as I know only the US recognizes asteroid mining and I doubt you could even drop it on Alaska. You would hate to have to race to the landing site against all the other treasure hunters in the world. Bonus points if the miner can be sent out for a second haul. Enough of these (and possible refueling in LEO) and you might even make a profit (ignoring lost interest costs). While most people would expect that a company that does such a thing would expect a profit from the actual metal, try to remember just how big an idiot magnet precious metals are. If there were gold asteroids, this would already have been tried, but I suspect that platinum is enough to get it done. I don't believe for a second that the amounts invested in precious metal mining on Earth comes even close to covering costs. And yes, you still probably want to beat "all the other treasure hunters in the world" to the site (just try not to be in the first wave of the shoot out). Another thing to remember is that steel (take your pick on the main alloy, you might have to recast the thing if you want specific traces in your alloy) asteroids are a dime a dozen (until you try to take them home, but asteroids fly painfully close to Earth all the time). Any large scale construction in space or anything with serious shielding requirements may very much want a handy asteroid nearby.

What could make an Orion OP/cheating? Blasting off Kerbin would wreck environmental havok. The initial calculations of minimal loss of life failed to include the existence of the (later discovered) magnetosphere. You need to be out around Mun to start it up. Newton also strongly implies that if you have multiple duds on your liftoff and the thing comes crashing down (see Antares), it will come down with the force of N atomic bombs where N is the number of non-duds that lifted it up. If you somehow drag/build the thing into Mun orbit, Bob's your uncle. The whole thing can be basically built with 1950/60's technology (except the whole "be in munar orbit bit). I'd certainly assume the whole pusher plate/ballast bit (the bombs explode off a plate that needs a mass similar to that of the rest of the ship) needs to be built out of an asteroid, and you will likely need a lot more shielding elsewhere that will come from asteroids or munar /[minmus] surfaces. One "limit" that might be missing a KSP mod is that the thing wasn't expected to go much past .1C. I don't know if this was a limitation of the rocket equation and the ISP of H-bombs or the issue of shielding while the ship is bombarded by .1C interstellar particles. Just understand that it likely takes tech not discovered between 1960-2015 to go faster than .1C.

I bought KSP through steam and can't get the demo (through steam). I guess I could create a separate steam account, but couldn't be bothered to answer a forum demo question. I think I downloaded the pre-1.0.0 demo. I know I built several ships using only demo parts and went to at least Minmus with it (but built the ships in "real" KSP and Kerbal Engineer). Note that with that demo you could use explosive staging...

How long was "air tourism" sustainable during the barnstorming era? On the other hand, I think the planes were paid for (WWI surplus). I'm also pretty sure that safety above all else wasn't the watchword of the time. But those barnstormers always made time for paid flights (of a few minutes a pop).

I'd really like to complain that re-processed nuclear fuel rods and fuel from breeder reactors should be considered "renewable". Using this stuff hasn't different issues (don't let another Ken Lay control the stuff), but isn't the same doom as fossil fuels.

This doesn't bode well for the Falcon Heavy then. On the other hand, I'm not sure what type of cargo SpaceX has contracted to lift with the Heavy: I suspect they don't have nearly the launch schedule. They might be launching in Houston and landing in Florida by the time Falcon Heavy really *needs* three landing pads (which just might be when Elon Musk says "that's it. Gas up a few Falcon Heavys, I'm going to Mars.").

Not bad ideas, but I suspect that the "retractable nozzle" would get cooked without LOX flowing through it and would add too much complexity with said LOX (or perhaps boiling kerosene, not sure which SpaceX uses). Mucking with turbopumps seems like another big issue. If I wanted pressure fed rockets, I'd probably strap some (hybrid* based) RCS thrusters around the rocket (possibly near the top, not sure how the math works for the pendulum fallacy with non-accelerating rockets). I'd also mention that there are two issues here. Landing on land and landing at sea. It appears that SpaceX is well on track to reliably land in a <10m area and keep the rocket vertical. It isn't remotely clear that the Falcon rocket could even stay vertical if it successfully landed on Feb 11, 2015 (13-20' waves. Reminds me of some 'impossible' (read lots and lots of reloads) Mun landings with foolishly tall rockets). Even with calmer seas, barge landings may well require hovering. And as far as I know, SpaceX only has one landing port on land. Falcon Heavy needs 3 landing ports. * hybrid meaning pressure fed NO2 into a rubberish fuel. Used by SpaceShip1/2 and a host of high end amatures. Should be a fairly good RCS rocket if you don't need to worry about multiple ignitions. If the initial ignition is a big issue, they you need hypergolics. I suspect that using hypergolics would make it harder to get permission to land on Cape Canaveral (I'm not a fan of them myself. The stuff is condensed liquid evil).

Usually the rest of the world (well all other industries) takes off with cheap oil. Pretty much *everything* requires a bunch of energy to do, and cheap energy makes everything that much cheaper. Not so good for industries governments dependent on oil sales. Also not good for anybody trying to replace oil (tar sands, solar cells, electric cars, wind plants). The Saudis have been doing this on a regular basis to prevent competition, but this appears a bit extreme. Not so sure how much longer they can pull it off (oil use keeps increasing and they can only draw so much out of those pumps without damaging the fields. Once those pumps pull water, the house of Saud likely falls and the whole country becomes irrelevant (with the presumed exception of Mecca and Medina).

While "we" are researching the next great means of nuclear power, just what will it take to use the means at our disposal? Must we keep burning coal?

Also Putin (or other Russian sources) is not selling for US DoD flights (why the US would use such rockets is another question). In this thread about the zenit, it mentions a Ukrainian source for much of these rockets (couldn't tell about the motor. From the sound of it each has parts sourced from both Russia and Ukraine). Even if the ULA decides to build in Alabama, Ukraine assistance might be the difference in go or no go.

Sounds like they were de-orbiting the whole adaptive*-focus mirror (I'd suspect they were *that* valuable). Even using large glass plates, I can't imagine a bunch of negatives (and deorbit rockets, and heat shields, and parachutes...) weighing a literal ton. I have to wonder if they were still physically sending negatives back by the time they were using adaptive optics (it would take a looong time before CCDs would give better imaging than film). * I've hear the phrase "adaptive optics" had some serious classification and could only be talked about after the proper "beyond top secret" handshakes were done.

Getting the probe to Alpha Centauri is pretty straightforward: aim it there and wait. Use an ion engine and keep firing prograde until free of Earth, then free of the Sun (and pointed to Alpha Centauri). Difficulty: you probably want to replace the Xeon with Argon (they are both noble gasses to avoid fouling the system, but Argon is more common than CO2, while Xeon is unbelievably rare. Unfortunately Argon will make your engine much less efficient, but you can bring along plenty of "fuel". Second difficulty: you will likely want something other than the Pu isotope currently used it space, the half-life won't get you that far out of the solar system. You will also likely want another [low power] RTG with a long-lived isotope for communication along the way and possibly getting there. Slowing down is the kicker. You can either flyby way faster than New Horizons ever did (well, you are flying through an entire solar system, but at relativistic speeds) or spend nearly half the trip slowing down. My guess is that this just isn't an option. The reason is that you have to start so you have roughly equal burns accelerating and decelerating, and designing a RTG with multi-century lifespan isn't going to happen (by the time solar works, you already left the system). Six year latency (three each way) means that you can pretty take as much time as you like to encode your signals. Current tech (ignoring the "last for centuries" requirement) should be able to hit Shannon levels (the mathematically ideal levels) of error correcting codes given that the time it takes to compute them isn't an issue. On the other hand, that latency means that all your assumptions had better be right (locating Sol, aiming the laser or whatnot at it and blasting the message away) had better work as even with centuries to wait you only get a fixed number of communications/responses. Don't ask me about "last for centuries in 3K and vacuum". I'd like to say that in interstellar space there won't be the nasty radiation, but if you want to get there at all you will be bombarded by particles traveling at [your] relativistic speed (this might mean that you have to do the [nearly impossible] slowdown manuever or have more "Alpha Cent wind" [see solar wind] than you can handle [at .1C]. This might be nearly impossible, but presumably *somebody* knows something about how most of the things [semiconductors, NTR parts [the isotopes are straightforward, but the other stuff?] and robotics [may all the gods help you with the servos]. This all assumes that *somebody* will remain in contact with it for 400 years. Presumably, that means that using 400 year old technology wouldn't be a problem (I've hammered a rail road tie in a blacksmith demo myself, as long as the tech keeps getting used it isn't a problem). While it seems weird that you would have to maintain a 400 year old protocol with 400 year old algorithms, don't be surprised if there are bits and pieces of TCP/IP 1.x still lying around then.

You don't. If you try landing on a planet with an atmosphere, the fuel suddenly becomes a huge problem (nevermind the nuclear issues already mentioned may be insurmountable). I've already gone over the fuel issue in space. In an atmosphere (temperature >30K) things get hairy fast. First and foremost, if the LOH goes >~30K you have a big explosion. Try closer to 20K at all times (a slury) to keep leaks to a minimum (H2 leaks through everything). Obviously, this isn't an issue with bringing a lander home to Earth, but do you want all the real and imagined nuclear issues in bringing a nuke back to Earth? Oddly enough, I'm working my way up to this issue in KSP. I'm taking a party (8 or so) of scientists for some xp gathering and the main rocket uses nukes. Being a cheapskate, the rocket has solid boosters and then switches to nukes at stage 2 and goes to Mun, Minmus, and beyond on just stage 2. Being even more of a cheapskate, this huge nuclear stage 2 is coming home to Kerbal. Best guess is that it will require asymmetric landing gear to land on its side (I've favored wide landing gear in the past, but mostly in versions without re-entry heating.

Looks like I simply remembered the only stroll down the hallway that contained KSP, or perhaps Randal Monroe isn't popular at Goddard (or the few hallways I remember there). However, we do have an existence proof of KSP at NASA (for at least values of razark).

Nope. First "powered landing" from space [to Earth]. Other rockets that have landed from space: X-15: First! And manned (199 X-15 missions, although few went into space. That's more X-15 launches on 3 planes than the whole fleet of shuttles). Shuttle: Manned and made it to orbit and back (for smaller value of rocket that left the launch pad). Space Ship One: Space, manned, and quickly returned to space. LEM "Eagle": first manned powered landing from space (not on Earth), (presumably there were probes as well). More LEMs followed. Curiosity: Powered landing from space (on Mars). Did use some parachutes/airbraking.

The problem was that the calculation ignored a bunch of radioactive material that was going to come back to Earth. It would likely kill more than 1 person (although I'm not sure they took into account how much the radioactive material would decay before hitting Earth). I don't think they realized this until after the project was canceled. 2000 bombs to orbit, 9000 m/s deltaV: 4.5m/s deltaV per bomb or 10mph per bomb. I thought the "pogo stick" shock absorber was bigger than that, or perhaps that is just the most efficient size for H-bombs (although I suspect Neutron bombs would be used to get into orbit, that *should* keep things down, but will still create at ton of radioactive oxygen and such).

I had a job as the onsite "Dell repairman" and fixed my share of laptops at Goddard Space Flight Center [DCish, Maryland]. There were a few KSP posters/pinups on the doors (roughly as many as XKCD). NASA employees all types of jobs, and there are many space enthusiasts who don't actually do rocket science/orbital mechanics. Consider the other famous XKCD KSP comic: Randal Monroe worked for NASA as a robotics engineer. He famously plays KSP. KSP gives you complete control over a mission (this may take mods depending on the control you want. It may require *writing* mods for further values of control). Kongress doesn't take your funding. It may be playing some sort of "dream NASA" for real rocket scientists.

Am I the first to name the Orion? Not the new pretender to that name but the original (never built) beast by Ted Taylor and Freeman Dyson. No, it really wouldn't work. The original calculations assumed that once the fallout was blown clear of the atmosphere, Earth would be safe from it. This is not true, any nuclear blast happening within the magnetosphere would be eventually pulled back (hopefully Earth would be spared most of the nasty half-lives, but still). You would have to build it out at least at Lunar orbit, presumably from steel harvested from asteroids (an Orion could lift the immense mass needed to build the thing. Chemical rockets, not so much). It remains the type of thing SpaceX would need if they wanted regular runs between Earth and Mars, but the required infrastructure is just huge. Still an awesome idea that makes the idea that pure space opera is in reach if we just had to guts to Build, Dream, Fly in real life.

[quote name='RainDreamer']Bows are still fundamentally limited by your draw length, so you might get a really big bow, but if you can't draw it to full, you can't utilize its full potential. [/QUOTE] That's what I assumed until I thought about it a bit more. You could presumably take a few steps back with a sufficiently big bow and then brace yourself for the last bit. Presumably the bow would also include two "kissers": one for the drawpoint on the string, the other as a reference sticking out from the end of the bow (you need some means of making sure the angle and length of those are the same). I was just wondering if anybody ever made one. Considering that castle archery points were essentially carved out of stone, you could easily mount something huge there and have an even greater advantage (you are already higher) over the attackers. [looks at google images]Pull *behind* the head? I wonder how you maintain your drawpoint? Although all I know about kyudo is that it each step is even more spelled out than the routine for firing a smoothbore musket in a musket square. Think archery moves taken to tea ceremony type obsession and you have my impression of kyudo.

[quote name='Motokid600']Thats a terrible analogy...[/QUOTE] Sorry, I just came from the deltaV of a human thread. At least I was able to try to move that one to human jumping.