wumpus

Except that antimatter *does* exist (and was confirmed way back in the 1920s). Things like metastable (that's the important part) metallic hydrogen, or even worse, magical resonators that violate the conservation of momentum don't. I will admit that I've never even heard of a theorical way to generate anti-matter in useful amounts. There's some great commentary here : https://arstechnica.com/science/2020/05/microwave-thruster-makes-for-clean-burning-jet/ It claims that most earlier designs centered around spacecraft: presumably heating hydrogen.

I suspect that Venus' albedo is already pretty high, making it more reflective would be hard. I'd expect that in nearly all terraforming projects, some sort of genetically engineered life would be designed to thrive in the initial conditions and slowly move things more Earthish. Kind of like how early life caused Earth's (somewhat) oxygenish atmosphere. Presumably some floating plant-life, that could exist in the upper clouds and photosynthesize carbon dioxide into oxygen.

No matter how much you may have liked the show, there was no way Space 1999 could have worked like that (even had it been a nuclear ammunition dump instead of a waste disposal site).

Facebook does, but is transmission media agnostic.

I'd assume collisions. Like air-bags, only capable of surviving much higher velocity collisions. You know Jeb will be trying lithobraking the minute he has his mits on something like this...

Just started one after a long time off (have to install RSS/RO at some point). Stability was kicking me. Stage 1 was perfectly stable. Stage 2 ... wasn't. Probably have to remove the multilab and have Jeb (instead of Bob resetting all the experiments) fly the rocket...

First you put a planet's mass in the rocket equation under "massdry", include your Isp and then see how much fuel you'll need (and of course, make sure that Vexhaust>Vescape. I suspect you have to subtract Vescape from Vexhaust, thus killing your Isp)... Rocketry just isn't viable for moving planets, possibly even with anti-matter. Consider bombarding it with photons or something (so you only have to deal with the planet's mass and any fuel). From memory, there was a Star Trek book where this was the premise (the Enterprise had to pull a planet out of tidal lock). When you finished it you discovered that the entire book was written to (correctly) include the line "then dawn broke on the planet".

It isn't all that clear how useful asparagus staging would be in real life. In an ideal case, asparagus staging gives you the thrust of your second (or higher) stage for free. No more. In practice, this is ideal for booster/sustainer designs where the sustainer stage can fire "for free" and not carry any excess "empty propellant mass" until it stages. This really isn't a major factor in going to space (although any extra thrust while your boosters are firing is almost always helpful). It also means making sure your sustainer nozzle can operate down to sea level (or launch altitude). From what I understand, a major force in the booster/sustainer model was avoiding in-flight ignition. Don't expect such a rocket to launch until all boosters are ignited (the TWR isn't high enough). Asparagus staging got a huge boost from KSP players as KSP has artificially heavy fuel tanks (to compensate for the tiny planet, which in turn reduces the time required to get to orbit). It also helped that for pre-release versions of KSP, the aerodynamic model favored TWR=2.0 the whole way up. On the other hand, the Dynetics lander has drop tanks, a technology essentially similar to asparagus staging except it doesn't waste the engines. This can be used in a manner similar to "bamboo staging" (except that traditional "bamboo staging" is unstable: you have to stop, turn, and eject fuel tanks from the top and not the bottom if you want to make a stable rocket) that allows multiple "stages" to use the same engine (saving both mass and cost on your engines. Just don't expect much in the way of TWR).

Not to mention all the issues trying to create a counter moment to deal with the issue that your thrust/direction/center of mass aren't all in one line. NCC1701 was even worse, although a bigger problem was how flimsy the main structure was.

It is always great to be on a forum where that is the appropriate response...

The other issue is that any [magnetic] force you can exert to reduce orbital velocity can be trivially reversed and used to go from orbital to escape velocity. You can move a satellite by moving against Earth's magnetic field, but it is only good for stationkeeping, not significantly changing velocity. It also only works on a few planets, Earth being one of them (Jupiter might be another).

KSP doesn't penalize Qmax(maybe RSS players know when their rocket goes through Qmax, for nearly all KSP players, it is a non-issue). While I've always believed KSP TWR should approach 2, I didn't think that was popular amoung most >1.0 players (the pre-release edition "souposphere" worked best with TWR==2.0 the whole way up). One of the big differences between KSP and reality/NASA is that NASA (and other pro rocket builders) have fuelmass/fueltankmass ratios similar or less than the ratio to a coke can and the coke inside. TWR of 1.15 isn't a big problem (although SpaceX seems to like their TWR~=1.3 or more). The only orbital rockets I'm aware of with TWR>2 are all-solid rockets (I think Japan has launched a few with TWR of around 5).

Pretty scary how much room it takes when it still needs twice as much oxygen as kerolox... (quoted time incorrect as I can't delete the empty table).

50 Merlins is not a fantasy Saturn but a fantasy N1. Depends what you pick and choose from "legacy". NASA's prototype reborn F1 engine would make a lot of sense for a Super Heavy lifter, especially if you are not concerned with reuse (pretty much starts and ends with SLS). Building the rest of the rocket? You'll find a lot of "use asbestos here" and "perform a ton of hand welding operations that haven't been done since 1975 there" and "include lots of MIL-SPEC parts that haven't been available since 1990". And don't forget that everything electronic assumes lead-based solder and that could be important in the temperature ranges they encounter... Once you complete redesigning your rocket, you also have to redesign launch procedures as they really weren't documented well enough to replace the *entire* army of technicians needed to launch the rocket. You are essentially going to design an entirely new rocket. But don't ever assume you can ignore legacy altogether. Building any kind of Saturn-sized rocket almost certainly wants to use Cape Kennedy's Vertical Assembly Building, although I'm not sure of the status of the crawlers (which you want if available). You want any available launchpad, and should try to integrate your rocket with an available pad (replumbing for methalox will be expensive). Any available testing facilities will also dictate limits on just what you need to do (you don't want to build your own from scratch). And of course there are all the regulations that have been written in blood over the last 70-odd years (plenty of which were written *after* Apollo, especially the updates after Apollo 1).

Pretty much everything emitted beyond a planet's orbit will be swept out by the solar wind into interstellar space, probably decaying into iron or something over the billions of years before anything encounters it (or more likely just decaying into energy and winking out of existence after 10-100s of billions of years with no encounters). Production of said material matters (and again I'll nominate argon), but spewing nuclear material is a non-issue. Note that unlike leaving chemical residue between planets, nasty nuclear issues clean themselves up in days, rougher stuff in years (just in case it gets near a planet or trapped by an asteroid), and any measurable radioactivity will be gone after millions of years. Between orbit and escape velocity I'd like to nominate ion drives driven by argon. Obviously, xenon is just as inert as argon, but argon is so wildly common (more common than carbon dioxide in the atmosphere) that scaling up production to any level isn't a big deal. Power is obviously required, but that's typically solar (especially in Earth orbit. Mars and beyond probably requires nuclear power, but that's pretty green on its own). Generating fuel/power on Earth is always the tricky part, and expect much of the exhaust to remain on Earth. Hydrolox is famed for providing nothing but water, but produces plenty of carbon in production. Kerolox and methalox produce carbon dioxide during flight, but also don't appear to release more during production (although recent reports imply that this is completely wrong with respect to methane. Methane production appears to be far worse than we thought). I'm no fan at all of hypergolics, and don't think they really should be used for first stages at all, but I understand that they make a lot of sense for ICBM applications, and ICBMs get the funding that space programs piggypack on (and not vice-versa).

Care to compare cost of rail travel to air travel in the USA? As far as I know, air travel has energy costs similar to car travel while rail costs are somewhat above sea shipping but far lower than everything else. There's always the chance that the cost of domestic air travel gets quite expensive. Of course the real cost of interplanetary flight likely will be maintaining the passenger cabin. Unless you have some sort of cold sleep, costs will be similar to oceanliners in terms of crew and wages. Travel to Mars and Venus doesn't require all that much more energy than LEO (which might be used as a hub for intra-planetary travel for all I know).

The 650 ton Airbus A380 is going out of production, while the 50-80 ton non-max 737 has been extremely successful. Of course if you have a single destination of "Low Earth Orbit" (or possibly "just beyond the Van Allen belts"), perhaps you will do better with a much larger craft. Although I suspect that a Falcon 9 might match a Ford Trimotor as a better historical analog. - note the numbers are for the total weight of the aircraft: assume roughly half of that as payload (unless going London-Sydney, where you need almost half the weight as fuel).

For the "too short", "too long", "just right method" wouldn't two barrels (to throw the "too short" and "too long" shells at once) be better? Once they land you can calibrate your "just right" shot (or fire two more for successive approximation). Of course this assumes that time to load >> time of shell in flight.

I'd have to claim that "comet of the [20th] century" was Shoemaker-Levy. That said, I have vague memories of Comet Kohoutek (mostly remembering local department stores full of telescopes, plus one boring evening trying to see it) and *think* I saw Halley's comet when it swung by (it was hard to be sure which "star" was Halley's). But Shoemaker-Levy's trajectory was already established once you heard about it (unless you are *very* well connected with comet hunters: a possibility on this forum).

I still wonder if aluminum foil would make an effective parachute for atmospheric braking/capture. I'm guessing that using it as an inflatable heat shield would make more sense, as that even with a large hole in the center a parachute contracts the adiabatically heated atmosphere while the heatshield spreads the heated mass over and around itself. So while you would have to use more foil for an equal frontal area, you would probably have more deceleration per gram of Al.

I liked the story about "positrons travel backward" enough that I had to ask if enough had been assembled to observe entropy. Alas, entropy was moving in the right direction: no "Practice effect" anti-matter for us. https://www.goodreads.com/book/show/101893.The_Practice_Effect

That should be easy to find, just find a bunch of space glowing due to all the matter/anti-matter annihilation going on (hint: we don't know of any. We'd expect huge areas if there were galaxies of anti-matter, but there aren't. You think you'd find small areas of anti-iron, but I've never heard of any. When I first heard of Orion (probably from Carl Sagan's Cosmos), I've always heard an "can achieve .1c" with no explanation of 30000000m/s delta-v. Going by the 12,000s assumption, I'm seeing a wet/dry ratio in the googol (>10100) range. The pusher plate and spring system should account for a large proportion of an Orion. Well, at least until you load it up with a few googol nukes.

Done plenty of times on Mars with airbag landings.

The rocket equation depends on the conservation of momentum. In a NPP, this breaks down into two parts: the pusher plate conserving the momentum of the blast it is hit with, and the pusher plate and rest of the rocket conserving momentum as the pusher plate is pushed back toward the rocket and then pushed back to the initial position. I'm not really sure if it still holds (it probably should, as the pusher plate forms an elastic body. But I'm not sure I can justify the same assumptions as a rocket).

Does this happen when people move to NYC (or Europe) and don't need a car for several years and then start driving again later? I think that this should be a common enough experience. I tried to google if having a gap in insurance caused painful rate hikes but only saw hits for "gap insurance". "Won't save everybody" and "won't save a significant number of people" are two different things. By the time my father hit 80 it was obviously time to hang up the keys, but he lives in North Carolina so there really aren't other options. He's had at least one crash thanks to driving though a red light... I'd really like to know why everything has to be mandatory or prohibited. Presumably regulatory capture means that once a business is allowed to sell something, they want 100% market share.