wumpus

To be honest, the ISS was budgeted as someplace for the Shuttle to go. But ISS is also the "least expensive way" to get that much space experience. Out where the Gateway is, all you get is more radiation, and the chance for life threatening radiation bursts. But otherwise very little "real space experience" that you don't get on ISS. The delta-v from LEO to the Moon (LTI) is ~3000m/s. The delta-v from LEO to Mars intercept is ~4000m/s. I can't imagine an Adrin cycler needing a significantly higher delta-v than LTI, and such a gateway would be a *real* gateway (although I'm afraid you need a separate cycler to come home). Other options are to put the thing in L2, if you really wanted a gateway, but while things might hang out there, virtually all of it could be automated. The only really effective way to use a crewed "Gateway" is as a cycler.

I'd assume that it is more a naming gimick. The Chicago Loop is already there, has been there for a long time (100+ years?) and is far too small for a hyperloop. NYC and the SF Bay area would probably work best, especially between long spread subway areas (and commuter rail in San Jose and similar). DC would also work well, presumably just a single rail for Gaithersburg, Metro Center, Beltsville (Beltway), [Columbia*?], Baltimore. A "Virginia line" that meets at Metro Center would probably be next. There are test builds in DC (easier to get right-of-way in I95 between DC And Baltimore than most such right-of-ways, although I'm pretty sure that's the whole point of the Boring Company: to make the biggest problem the hyperloop faces, right-of-way, disappear).

The DC Metro (subway) stops 2-3km short of Dulles Airport, but the politics involved in the Metro don't make any sense (at least what I learned in school about how it was started made absolutely no sense. And it hasn't gotten much better). I'd expect O'Hare to be largely transfers, being right in the middle of the US. Maybe not as much as Atlanta, but mostly transfers. They wouldn't have more traffic than NYC and LA if it wasn't for transfers (plenty of international flights transfer to NYC).

Most of the reason for Mars is that it is far away, and a planet that isn't actively trying to kill you. Mercury: Way too hot. Might have been interesting if it really was tidally locked, but you simply must leave the surface quickly (20-30 days) or be exposed to the day. Venus: Almost as hot. It might as well be a gas giant as far as the surface is concerned. Moon: Close enough to be less exotic, and people have directly seen how dead it is. Mars: "some" atmosphere, and life isn't proven extinct Gas Giants: Nothing to land on, and an impossibly deep gravity well. If you aren't landing, you might as well stick to Venus. Gas Giant moons: Might be interesting, but no real advantage over Mars has been found. My guess is that any attempt to colonize will fizzle and fail: the only reason to move there is for science, and I don't see anyone setting up a permanent colony on Antarctica. The asteroid belt seems to have more resources to exploit (to the point of a possible economic return), but it isn't clear that it would justify human rather than robotic settlers. I'd expect any "colony" to show up much later to supply "belters" mining the asteroids (possibly mirroring the "mountain man to settler" progression settling America).

This http://www2.estesrockets.com/pdf/Estes_Igniters_and_their_use.pdf seemed the best information on the net, and doesn't go much beyond "parallel, not series". It does go into detail about using a 12V car battery, do you have a sufficient battery (or better yet, ultracapacitor) to do the job? I can't say I was impressed by the "attach everything by alligator clips", I'd like to make sure the wire can at least follow the rocket up the launch rod before connection is lost. Two engines shouldn't be much less than half as reliable as one, unless you don't have enough current or the ignition delay is too long.

As far as I know, the original ATK is a bullet company. They make all sorts of solids that turn into rapidly expanding gas, and military uses for projectiles are the biggest application (I'd expect they go down to small arms for military and commercial use, but didn't dig that far). I'd expect that this is how they got the original contracts from the Air Force (while either still Army Air Corps, or if not commanded by old soldiers) to build solid rocket motors for ICBMs.

Since both the potential energy thanks to height and the kinectic energy of velocity is proportional to the square, I suspect it scales linearly (I've thrown that envelope away), so 50m/s? Granted, that's 110mph and the speed I've heard for model rockets is ~300mph (this was from when I was "model rocket aged", so might be very, very off). But I suspect model rockets hit an aerodynamic wall once the rocket burns out and 150m/s of delta-v has more than 100m/s of aerolosses in a few hundred meters (gravity losses are non-existent: you need huge TWR for stability (you have to accelerate to a speed where your tailfins aren't stalling before you clear the rod).

I'm sure there are plenty of chemicals that are "more green" than hyrdazine that you wouldn't want in your garage/shed, but that could be tolerated on a secondary payload or wouldn't require technicians to suit up in hazardous materials outfits adding a million dollars or so to the budget, entirely thanks to the hydrazine. Ions not useful for "orbital changes"? I guess it entirely depends on the timeframe. I'd assume that ions are ideal for "orbital changes" (especially inclination changes and or migrations to something like GTO). On the other hand, if it is a "hot spare" for something like Iridium, you may be better off launching a new one in it's place (and have to have it scheduled to launch some months later) than have to wait for an ion engine to get it in position. Also, considering the cost of most GTO satellites, operators want them online within days of launch, not months. But anyone with a much smaller budget, any type of high-Isp electric propulsion will beat chemical.

Have you seen this? https://www.youtube.com/watch?v=d4EgbgTm0Bg I hadn't heard of quaternions until arstechnica had a write up on a post-doc's stalled career chasing them. Since complex math is so absolutely critical for dealing with any wave-based math, I'd be fairly shocked that quaternions don't describe wave-based reality in 3-4-8 (slightly different math for 8) dimensions. I wouldn't be at all surprised if the answer to "why chaos" isn't that "speed of light" waves propagate in even dimensions, but de Broglie waves (i.e. physical matter) have to propagate in some non-even fraction of that. This of course says nothing about the 3 body problem, so isn't a full answer.

In the "amature rocket to orbit thread" a forum member named Riven mentioned being in a contest to reach 10km (without exceeding 15km). Original budget was claimed $60k, but checking the SJSU rocket club website indicated a $10k target budget had been met (but no further mention of a rocket launch). 10km requires (after gravity/aero losses) 500m/s delta-v.

I think early shuttle wing designs looked more like an X-15, but there were some issues across the huge range of speeds the shuttle would encounter. The biggest problem with copying the shuttle (and then doing a hoverslam) is changing direction: I don't think that is realistic at any speed. Having the center of drag so far in front of the center of mass (assuming a propulsive landing) will stick out to Kerbal players. Better make sure your grid fins have more drag than the tail fins and are way in the front or kiss stability (even computer assisted) goodbye.

Fuel tanks are even worse. Kerbal fuel tanks have a ratio of (at best) 10:1 wet/dry ratio, NASA should get twice that. And I'm pretty sure that NASA's 20:1 ratio includes things like engines and everything else discarded in a booster stage (expect similar numbers from Roscosmos, although I'm less familiar with their numbers).

95-100 success rate? Real life isn't KSP and nearly everyone's first rocket explodes or otherwise doesn't make it to orbit. The Russians didn't mention any flight that hadn't already succeeded and do you know *any* rocket program whose first attempt to orbit succeeded? 0-5 is more likely, although I'd still advocate the "just a few grams" satellite if you want a chance. There are a few threads about "attempts to make a rocket engine" and see how many of them were successful in producing *any* thrust on the first go, let alone the thrust calculated as needed. SpaceX had a $90M dollar budget and still took 4 tries to get to orbit (don't ask about NASA. And for all the noise Blue Origin makes, they haven't launched an orbital craft yet).

My username comes from a game so old you had to type it into the computer from a book called "[More] BASIC Computer Games" (Creative Computing also published it a few times). If you had a TI99/4 computer, you could buy a cartridge so you didn't have to wait for the tape to load, but that's not what I had. I have a Steam account full of old games bought cheap: some played, some not. Bethesda games, especially the Elder Scrolls can really suck way too much time out of me (currently finishing Fallout 3, one I somehow missed). For the more "non-gamers", it would be hard to come up with a game anything like KSP. Minecraft has a similar cult following and a "build like LEGO" vibe. Civilization is one of the great all time games and has a similar "one more turn" similar to "one more design/launch itteration" in KSP. Typically you want the "next to last" civilization as they tend to ship less polished than the previous game, and then require patches and expansion before it surpasses the previous one. I'm stuck on Civ4 as I can't see any feature being worth giving up Leonard Nimoy's voice acting.

Crazy tin can idea: according to the "infallible wiki" (some criticism of my use of that phrase) https://forum.kerbalspaceprogram.com/index.php?/topic/91282-for-questions-that-dont-merit-their-own-thread/&page=85 Diesel direct injection can be used with pressure of an order of magnitude greater than needed by a turbopump (or at least in the combustion chamber). Unfortunately, no such numbers are so readily available for GDI (gas direct injection: we could presumably use diesel fuel as our rocket fuel, but diesel injectors require diesel fuel for lubrication. I strongly suspect the oxidizer may have to go through GDI injectors, which are less mature. Or we could use kerosene or ethanol and two sets of GDI injectors (I'd assume we would use *lots* of injectors, at least the whole "rails" worth, and probably multiple "rails"). I don't pretend that I'd expect such a rocket would have a TWR >1, but it might be a highly efficient rocket and quite useful for a second stage (assuming you are willing to ignite it). My understanding is that 20-40 minute burns to orbit are pretty standard, and this type of thing might be an option. The whole point is that the last think I want to build for a rocket is a turbopump: and if I can find such a thing on the shelf (or better yet, a junkyard) I will grab it while I can. - just stand as far away as possible when trying to put LOX through a fuel injector, especially the first time (perhaps we route LOX around the nozzles to cool them and fuel around the injectors to keep them from freezing).

A better question would be "how much mass does it take to send a Sputnik style 'beep' to Earth?". 4-10 *grams* might be better. Falcon 1 had a $90,000,000.00 budget (or spent that much, Musk was in trouble even with success). The most obvious way to reduce that cost by orders of magnitude is to reduce the mass to orbit by orders of magnitude. What is so important about HTP? Some quotes from Ignition!: Recovery is obviously not in the budget. I still like the idea of parachutes replacing upper stages during testing. Are you for or against side boosters? First you "veto" it, then you use them for guidance. I'd strongly recommend them to avoid ignition of liquids in flight while still getting a "stage and a half" out of ground ignited stages. - don't forget nitrous - propane for an intermediate stage. Although it would likely be canceled thanks to slow self ignition. While this wouldn't be a problem in flight, building the appropriate test stand to develop slowly igniting hypergolics (without pooling below the engine) is probably enough to can the idea. Synthesizing fuels are never a good idea, and storing HTP is a huge problem. I don't recall John Clark *ever* being interested in synthesizing his own fuels in Ignition! On the whole it sounds more likely to get a rocket scientist blown up.

I've been using the phrase "infallible wiki" for a bit under a year. I never thought anybody would post the slightest suggestion that I was serious. I've found errors, but never was willing to wade into the politics of wiki to correct it (I have edited a couple local wikis for specific domains). I find it good enough for "internet discussions", but for ones at least as accurate as here I have to admit when I'm using it as such data can't really be trusted (thus my use of "infallible wiki"). I loved that the Otiz page gave specific years for his birth and death. Carbon dating must have come a long way. But in the sciences I've seen at least one case where wiki had the sign wrong in an equation (eventually I figured out the mistake).

The cost was taken directly from the poster Riven who was claimed his[?] group needed $60k to fling 1kg at 500m/s. Checking their website it turned out that their final goal was $10k. The $10k was raised but no reports on building the rocket (or successful launches and/or explosions) were listed on the site. The biggest cost would be manufacturing, unless somebody has access to a CNC machine (or perhaps a lathe and gear that can approximate a CNC machine given enough time), especially if an iterated design process (design, build, explode, redesign). In other words, learning rocket science is expensive (see design, build, explode, redesign) . There are comments about "re-use". Any "built on the cheap" orbital rocket won't have the slightest delta-v budget for reusability, but strong parachutes (possibly adding soyuz-style retro rockets) might make a great dummy load for testing the first stag e. Still expect to lose a few boosters while getting them to work. Things to consider include: Staging: Serial or parallel? Fuel: Liquid, hybrid, or solid? Guidance: Gimbal, differential thrust, or aerodynamic Staging: Primary boosters should be parallel. This removes a lot of "how do you light the second stage" (procedure is almost certainly ignite verniers [if any], ignite sides: if everything is burning, ignition and liftoff). Expect to need plenty of serial staging after that simply for want of Isp. A third stage might by pressure fed nitrous into some sort of hybrid propane [might need to be pressure fed as well] as this combo is said to be hypergolic. Final solid stages would be ideal for sufficiently tiny satellites, presumably simply purchased ammonium chlorate in a carbon-fiber tube (keep costs low by making it small) [this should be available in the USA, no idea about exporting it]. Fuel: Liquid should be avoided as hybrids should reduce complexity by half (nitrous/propane might be an option for a stage lit in flight). Hybrid is pretty much the booster of choice. Solids make ideal rockets that can be arbitrarily small and lit in flight. Turbopumps are likely out (no way to reduce the cost enough) even if they are electric. Guidance: Expect legislated laws to drive the design more than physical laws, as rocket+guidance=missile. Gimbal seems a nightmare. Differential thrust might be done better by a set of verniers (like the Soyez). Note that any "vernier" we would use is almost certainly a small hybrid rocket with a throttle: it would have to be able to run at more than 1/2 throttle the whole way up (where full throttle is wide open and minimum throttle is as little oxidizer as you can get away with and keep the rocket burning). Aerodynamic guidance sounds good, but probably just left to "having fins" in the end (small rockets have even greater aerodynamic issues than the big boys, so such a rocket likely makes a pitchover well past where fins really work).

It wasn't music. It was just the clip of ET saying "ET phone home". 4k is *small*. Ötzi the Iceman (Italian Alps, 3100BCE-3400BCE) had a copper axehead. Copper was available to at least some neolithic tribes in the Mediterranean well before ~1500BCE (of course trading for copper and making it yourself are two different things when considering an ancient civilization). [dates from the infallible wiki, although I knew about the copper tool from elsewhere. Wiki also claims that Egypt was slow getting into iron as well (~500BCE even though "nearby" cultures were using it around ~1200BCE), even though you would expect them to have contact with the Hittites and other iron-using cultures.]

Ever try sourcing multiple tons of HTP? John Carmack claimed he did and found it to be impossible. If you don't like nitrous I'd go straight to LOX. I'd also be surprised if it is any less nasty than LOX. If Copenhagen Suboritals uses it, it is probably simply copying the V2 system (LOX/Alcohol is a great propellant if you want to trade a little Isp for a much lower temperature, but I suspect we want one solid/gel propellant and one pressurized one: see below about costs). I strongly doubt anyone is simulating it beyond Realism Overhaul (the KSP mod). It would be at least in the high six figures, seven if you're going bipropellant with turbopumps. Be prepared to ask executives of companies in person to sponsor you. Source: VP of operations for a space exploration org at my university. Our current flagship project is for the FAR-Mars competition. TL;DR for competition description: you fly an unguided liquid methane fueled rocket with 1 kilo payload to as close to 45,000 feet as possible, and we have until May 2018 to put something together that flies. We've done a lot of the theoretical calculations so far, and we have designed the engine already, but guess why we can't do testing and manufacturing yet? Money. We estimated that this rocket - including GSE, ground station electronics, custom fabricated test stands, test equipment - will cost us upwards of $60k. The engine itself would cost $15k to 3D print out of Inconel 716. It would be 3D printed because drilling extremely long and thin regenerative cooling channels into the thin, curved walls of a small methane fueled engine is probably impossible. While most of our efforts are focused on continuing to design, the president and I are organizing business majors to go to companies in person to attempt to get funding (or even spare rocket parts). We had limited success with Cryoquip, Inc. when we talked to them in person over the summer for example - they were extremely excited to design high pressure composite cryogenic tanks for us - but they got some LNG deal in South Korea recently and they dropped our project. I skimmed through this thread and saw something about using turbopumps. If you can shell out tons of money for the manufacturing of it, then sure. We considered turbopumps over our helium pressure-fed system for a week, but after realizing the engineering required for the complexity of designing and manufacturing one, we elected to use a helium pressure fed system pressurized to 15Mpa. We intend to apply what we learn building (and hopefully launching) this rocket to design an orbital cubesat launcher over the span of a few years because we need research, experience, and money/sponsors with operating something like this, and who knows, another university with extremely deep pockets (cough Purdue, USC, etc) could beat us to it by then. 1U cubesats - 10x10x10 cm. These can be as light as 1 kilo. If you have a highly directional VHF/UHF antenna and the right radio equipment, you can communicate with one in LEO. If KSP:RO can get the price anywhere near the "high six figures" we can discuss just where to find said money. That's basically the reason this is a necrothread. It would take several hundred thousand dollars not including the specialized knowledge and huge number of unpaid hours to design said turbopumps. Granted, this is simply what I've heard and I really don't know much about the process of designing said pumps. I know that designing relatively simple circuit boards "costs millions of dollars" when done by pros, but nearly all of that is engineer time and could be done for this project. I'm guessing that that the science of designing turbopumps is deliberately not published to limit "rogue nation" access and that a long design-test sequence will be needed. While blowing up test turbopumps up might be wildly cheaper in the CNC age than in the Vostok-Mercury-Apollo era, it still isn't cheap. Electric might well be an option. I'd also expect multiple (maybe just two) tiny solid stages at the very end, merely because you should be able to get the total stage at a much lower mass and a wet/dry ratio much higher (just don't expect to get more than a few grams into space this way).

10 km/s delta-v (*after* getting to orbit) will tend to cause spacecraft to run out of fuel.

I was googling about the safety of Finnish nuclear reactors and the results were primarily concerned about nuclear proliferation. ITAR might be US specific laws, but I doubt that the EU is all that crazy about dangerous tech being sold to certain nations and likely has their own set of regulations with a different name. I think that was the assumption that started this thread. I really doubt you are going to get the high test peroxide unless things have changed a lot since the X-prize was a thing (granted we are talking about right after 9/11 compared to 17 years later). I'd have to assume that nitrous oxide would be wildly easier to procure (at least in the USA, down under I doubt it) and use, while LOX would be easier to procure and almost as easy to use (although I've never heard of pressure-fed LOX). In the unlikely event that you can acquire HTP in Australia, that might change things (although I doubt I will ever be a big fan of HPT rocketry).

There was also an ET port for the Atari 400/800 (probably 600XL/800XL/1200XL were in production and mostly compatible by then) at roughly the same time. It was burned in ROM (like an early console game), so data was at a premium. When loaded (or the game started, it was way too long ago) it would play the famous clip from the movie "ET phone home". This was long before you could fit all the MP3s you wanted on cheap flash and took up something like half the cartridge's 8k ROM. The rest of the game (which had to be crammed into a 2600 sized cartridge) wasn't all that great, which is a bad idea considering that Atari had to price computer cartridges at twice the price of a normal game. It flopped, but I doubt they had to order a special landfill run. If you aren't assuming a specific speed for your photon there's also all sorts of other issues about how the "infinitely hard vacuum" exists and how big it is. Never mind measuring the speed, even trying to calculate what the thing is doing between two points should add additional "fuzziness" to the photon. Unless it is traveling an infinite distance it won't have a specific frequency, making the "width" it travels through effectively infinite. Unless the photon is traveling in its own universe, expect some sort of error bars around the speed that approach zero but never quite hit it (what happens when it gets to a planck length of zero?), but somehow the error bars "above" c never transmit enough information to violate causality. I think the above might show a difference between mathematicians, physicists, and engineers. The mathematician happily solves the pairs of differential equations (or not, because there are no useful theorems to prove) and considers reality an uninteresting special case. The engineer assumes that a fuzzy "real electron" only exists in the "real world" and figures that much of the fuzziness is by existing where all the other laws of physics hold. The physicist will simply ignore huge chunks of the physical world to ponder the interaction of certain equations and their effects (such as Einstein imagining what the world would look like from a photon's perspective). From this perspective, the job of the experimental physicist seems absolutely heroic: having to somehow "wall off" all the fiddly bits of the universe to peer in closely on the effects of just a few physical laws (the theoretician simply ignores them, but mother nature hates to be ignored). - Just schedule an intervention if one of them buys a CRISPR machine in order to produce a spherical cow.

Things that made a Space Shuttle Orbiter that you would never do today: If you can land (and reuse) a first stage, you will never put "main engines" on a second stage. That's way too much dead weight going to orbit when you can bring *anything* else with you. Yes, the shuttle did land and reuse the first stage "engines", but reusing huge steel tubes isn't saving any money. You want to reuse liquid rockets. The cargo bay only made sense if you are planning to return a satellite to Earth. In the unlikely even such might happen, I'd assume that you would make a custom capsule that would fit in the biggest fairing you can find (possibly the "new improved" capsule *is* the fairing to avoid these issues, but that requires complex retro-engineering for stability). Lose those and you have a dreamchaser. And it isn't really clear if it has real advantages, just that it is missing most of the disadvantages of the shuttle.

I'd also expect that the original design was to use the drop tanks to get to battle, then fill up before heading to the front. Only after realizing that tank fuel doesn't really affect anti-tank combat enough (it can survive a fire next to it, and not enough burns during the hit) that they changed how it was used. A T-34 example is also pretty weird in that it is often believed (at least in the US) that it proved that a tank needs to be just reliable enough to drive to the front and then drive the few minutes a tank is likely to survive in the brutal battles of the Eastern Front. I'm not sure the T-34 was that unreliable, just that those manufacturing them quickly learned to just push them out as fast as possible without worrying to much about how long they will last (battle will destroy them first). As far as bombers go, the entire aim of the Pacific Theater in WWII (after Midway) was the pushing to invade islands that could be used as air bases for bombers. The longer range the bombers had, the fewer islands Marines would die on. I'm sure that equation seared itself into a generation of American bomber designers. In Europe, bombers certainly would prefer to attack targets within "fighter distance" of home (or within "fighter distance" of friendly fighter airfields as they likely needed longer runways) for defense while doing a bombing run. Strategic command rarely seemed to go along with this idea as the number of targets increases geometrically with range (pi*r**2) and there was almost always something just a bit further they wanted to hit.