shynung

There's a difference between 'chemically possible' and 'can be mass produced at an industrial scale'. For example, it's relatively straightforward to produce the oxidizer O2F2; heat a large chemical reactor to 700 degrees C, and pour liquid oxygen and fluorine into it. However, approach any commercial chemical supply firms with orders for a few tons of the stuff, and one should expect most of them to reject it immediately. This is rational, because from a safety aspect, dioxygen difluoride is one nasty son-of-a-booster. From what I read, they explode seemingly at will, even when left alone. Now, other products might be far more forgiving, but the industrial processes are much more complicated. Sure, it's possible to turn crops like corn or sugar cane into ethanol fuel; the Brazilians have been doing it for years. What's not so obvious is that they require several industries alive at once to turn that bushel of corn into a quantity of fuel. Even then, the product is relatively simple; ethanol has the formula C2H6O, while octane (the largest component in common gasoline fuels) is C8H18. The reason why gasoline (and oil-based fuels in general) are cheap today is the fact that it's already there, in the crude oil, just waiting to be separated via fractional distillation. Even without mentioning the relative simplicity of distilling crude oil compared to the farming, fermentation, and distillation typical of an ethanol fuel production cycle, crude-oil-based fuels already win hands down against ethanol in terms of price.

Oh, I'd love to see something like that. Just do your research carefully before making it. Conspiracy theorists are a crazy bunch.

Rockets and piston engines maybe, but gas turbines aren't very picky about what gets into their combustion chamber, as long as it delivers enough btu/second.

Well, if you put it that way... John D. Clark's book once mentioned a truly crazy propulsion system: a rocket burning hydrogen, lithium, AND fluorine. And guess what it got? 542 seconds of vacuum Isp, at a chamber temperature of only 2200 K; SSME's went into 3500 K, and only got 453 seconds.

I sincerely hope you're just kidding. What's next? Dimethyl mercury and dioxygen difluoride?

Aw man, I was waiting for this one!

There are places where a jack-of-all-trades craft would be useful. In the wars currently waged on the Middle East, F-16 fighter jets have been used for anything from air defense missions to ground attack missions, i.e. 'bomb trucks'. The advantage is that the same asset can be used for a variety of purposes, often at the expense of the craft's mission-related performance (number of bombs/missiles carried compared to a specialized air defense/ground attack jets). In cases where the all-purpose craft has been mass-produced anyway, a common tactic of reducing the lowered performance is to deploy multiple crafts for the same mission. This is less efficient than sending in a single special-purpose craft that have better performance, but simpler from a logistics standpoint, to further reap the benefits of economies of scale.

Rockets used for launch vehicles are generally heavily standardized, while spacecrafts are usually specialized for the mission they are planned to conduct. This is because for a launch vehicle, the mission is almost always the same: put payload X to LEO/GTO/TLI/whatever trajectory the client asked, and the performance margins are pretty small. Most of their development consists of trying to squeeze as much delta-V as possible while keeping costs down, all while keeping the rocket itself from exploding before the mission is done. Spacecrafts, on the other hand, have a far wider variety of missions, from a simple communications satellite all the way to rovers, space probes, and manned landers. Compared to a launch vehicle, the dV requirements are lower, and the spacecrafts themselves must be able to do more than simply flying there, like transmitting signals or obtaining data from sensors. For this reason, the spacecraft's equipment are much more complicated than that of a launch vehicle, and generally different from other spacecrafts, custom fitted for the mission conducted in order to lower total mass as much as possible, conserving propellant needs for the same dV.

Hence the line, "actual engine specs may vary".

Hmm. Large RAM, but crappy graphics card, perhaps? My setup's the other way around; not much RAM but decent graphics card. It can run KSP at the highest settings with little lag, up until some 200+ parts ship comes along. Then it either CTDs or lags like hell.

Suppose an alien-made space probe the size of Voyager 1 enters the solar system from interstellar space, having a perisol just below Mercury's orbit. It has no engines, nor is it transmitting anything; its power systems are already depleted. It comes in cold, completely powerless and unable to do anything besides simply following its current trajectory. How early (or late) can we detect such a spacecraft, and determine that it's actually a spacecraft and not some metallic asteroid?

My two pence: -Standardization: already tried, considered successful. SpaceX's Falcon 9 used 9 identical engines on its lower stage, and a modified variant on the same engine for its upper stage. Greatly simplifies manufacturing tools, and reaps the benefits of mass production despite lower launches. -Kerosene fuel: already used, considered successful. Numerous launch vehicles, among the Falcon 9 and Soyuz rocket, used a Kerosene/LOX mixture as propellant. -Fuel Crossfeed: not tried yet IRL successfully demonstrated in the Space Shuttle Orbiter. Planned in the upcoming Falcon Heavy. -Advanced nozzles: no significant development IRL so far. Successfully demonstrated in KSP, but actual engine specs may vary. -Composite tanks: already used, but mainly as tank insulation rather than main structural part. May be developed if prices come down, but unlikely for the moment. Feel free to correct me if I'm wrong.

I shudder to think how your computer setup would handle something like KSP. Would it end like those wayward Mainsails that break off before it was even empty? On a more serious note, you should consider a new computer, financial conditions permitting.

Nah, it's cool. Good luck with your next videos.

I think you'd know what's best by now. Watching the Asteroid video now.

Propellant crossfeed needs more powerful pumps. That is, the engines on the side boosters of a crossfed Delta IV Heavy needs bigger pumps than its center-mounted cousin, because it has to pump more fuel in the same timeframe. Designing a new pump may require designing a new rocket engine, since the two is closely-linked. That said, SpaceX's upcoming Falcon Heavy do plan to use crossfeeding.

Use better chemicals. The performance of a chemical rocket is tied to how energetic the reaction between the propellants are. If you can find a better propellant, you can push the specific impulse a little more. Current chemical launch vehicles run on either LH2/LOX, Kerosene/LOX, N2H4/N2O4, Aluminium/Ammonium Perchlorate (used in solid rockets), or any combination of them. If the agencies/companies were a little more adventurous (foolish!), they'd probably switch the aluminium fuel in solids with powdered beryllium, which is more energetic. Liquid-fuel rockets can improve their specific impulse by switching to more energetic oxidizers, like liquid fluorine, or better (worse?) yet, chlorine trifluoride. Liquid hydrogen is already tops in being a high-performance fuel in the mix, but the density is rather dismal, so you can replace some of it with a higher-density fuel that is at least as energetic, or possibly more, like liquid mercury or lithium. Now, if you know a bit about chemistry, you may wince at my choice of propellants, and consider anyone even planning to use these propellants quite a bit nuts. And you'd be right; these chemicals are either highly toxic, corrosive, explosive, or (more likely) any combination of these delightful properties; some of this stuff, like liquid fluorine, has killed people before. Not to mention they smell bad. Really, really bad; the kind of smell that makes one think that pig sheds smell like a perfume shop in comparison. In conclusion, chemical rockets can still be improved in performance. The question is, is that extra performance worth all the extra safety hazards the scientists and engineers have to put themselves into?

You could, say, pre-record the slideshow sans voice, and dub the speech in afterwards. Yes, I know it may not be easy from your end, but listening to a monologue accompanied by only a single still picture can hardly impress any audience; words alone can only explain so much. At the very least, you could use a decent camera to record yourself talking in front of a whiteboard or some other media, while simultaneously showing some pictures relevant to or demonstrating your idea, either in the form of drawings, physical large pictures being shuffled around, or an office-meeting-style Powerpoint presentation. Remember, you're attempting to lecture people on science. How would you feel when having to attend a class in which the lecturer simply reads off a book or slideshow without bothering to explain, elaborate, simplify (where appropriate), and articulate the ideas he's trying to teach?

Not bad for an intro. If you'd prefer, you can follow people like Scott Manley or Vsauce in their presentation methods, which is lecturing an idea while presenting a slide show and/or snippets from other videos/web page/historical documents. May need some work on visuals, but it won't be as complicated as full-fledged animations. I can't help much on that front, though, other than sharing ideas and pointing out flaws.

How did they manage that? Negative AoA? Or just flipping the aerofoil around - flat on top, curved below? If using something like FAR, is it possible to simulate it in KSP?

Suppose somebody built an indestructible probe and plunge it into Jupiter. What would the probe encounter, from the atmosphere down to the surface? Will it ever actually reach any definite surface?

I'm willing to watch. Where should I plug in?

So? A microwave-beam engine would still need propellant. That means either having some propellant production/storage facility nearby (cryogenic, if we're using liquid hydrogen), or an expensive precooled thermal turbojet/hybrid engine, the kind that's used in REL's Skylon, if it ever flies. I'm not just talking about individual plants. What I'm saying is that a plant, or several plants, that have a total production capability even close to a gigawatt would not be cheap. Even if you split the load between thousands of plants, the total costs wouldn't be very far off. P.S. Try to emphasize with italics rather than all caps. Caps are like shouting. Thank you.

The problem with microwave transmitters is that it requires an upfront investment in a gigawatt-scale powerplant situated not far from the launch pad. A cryogenic fuel production facility of a similar size would have been cheaper. Also, no one is going to fly microwave-beam engines if there are no gigawatt-class gyrotrons operational. No one is going to build gigawatt-class gyrotrons if there are nobody around using microwave-beam engines to buy energy from them. It's a chicken-and-egg problem.

Large solar panels powerful enough to run something like a VASIMR wouldn't be lightweight. It could be lighter than a nuclear reactor of comparable output, but I think not by much. It would still be quite advantageous, though, since every gram of extra weight would eat into the dV budget.