wumpus

There are two entirely separate things under consideration. 1. A metallic state for hydrogen: This is highly probable, and research is getting closer and closer to obtaining it and determining its attributes. 2. A meta-stable condition that allows said metallic hydrogen to remain metallic without the use of a diamond press at all times. This appears to be [old] science fiction and unlikely to be possible. Certainly hydrogen has been subjected to on the order of 400GPa, and any metallic hydrogen formed immediately went back to gaseous state after the test. It doesn't seem likely to remain in any form useful for rocket propellant tanks. Most of us expect that MH exists. There doesn't seem much hope that it will ever be used as rocket fuel. PS: I remember an aside my Chemistry Professor made: if we could store monotomic hydrogen (H1 molecules) in such a propellant tank it would be roughly as effective as a nuclear rocket. Since this was a chemistry class (and not rocket science) he didn't elaborate on exactly what Isp he was talking about (and I didn't have any more rocket science then than a typical science fiction fan of the 1980s), so I'm expecting that it would be on the order of MH. So don't assume that MH is the only way to store hydrogen in a high-energy state, but I have less imagination for some means of storing monotomic hydrogen with an acceptable dry mass.

That and the DoD pretty much financed the rebirth of Iridium. By that point it was the main communication network of the special forces. Somehow I suspect they'd love having the same thing, but with far more bandwidth (even if the antenna needed to be mounted to something the size of a humvee roof). But the real money is connecting Wall Street with The City (and presumably the Hong Kong/East Asia financial markets) with a few less milliseconds of latency.

I'm not clear on how a gentler flare, less runway, etc. is necessarily "safer" than a human pilot, assuming that they can be done within safety margins and the plane is refurbished more often to deal with the extra wear and tear from such landings. A better question is if the autolander can detect an aircraft on the runway (a far too common error). Can it detect an aircraft on the runway with a disabled transponder? How about a car on the runway (this might require a pilot on the upper end of eyesight, but military pilots are often chosen for exceptional eyesight)? Adding an autolander likely increases safety when the margins are thin enough that it is safer to come in blind than to try another airport. But I can't imagine that taking the pilot away from the controls in general is going to be the safer solution.

I'm not sure what you want the abort to do. In this specific case, the passengers would only have to survive Starship falling over after the "soft landing", and after that it would be similar to landing on the Hudson. And while the craft *did* abort (to a safe mode that wouldn't put a hole in the barge), I'm not sure what type of abort system you could have on the booster. Has *anyone* created a *landing* abort system? Either Soyuz, Shuttle, or otherwise? Yeah, but I was pointing out that it wasn't just "around", it was inescapable.

"Cryogenics on board" meaning the booster is >99% by mass of either cryogenic oxygen or kerosene cooled to cryogenic temperatures? Well during launch. During landing the ratio is far, far, less.

Randal Monroe did the calculations based on Estes E9-4 model rocket engines and determined that a 30 stage rocket the size of a tow truck could deliver a squirrel into space (i.e. suborbital). Going into orbit was roughly impossible. I'd claim that as long as you limited yourself to "gunpowder fuels contained by cardboard-based tubes", you could get rid of most of the stages with much larger rockets (you'd still have issues with the Isp of gunpowder and the thrust limits of your cardboard) and get rid of most (but still leave plenty) of the engineering nightmare with such larger rockets. I also suspect that the remaining engineering effort involved would be higher than a putting a "real rocket" payload into orbit. https://what-if.xkcd.com/24/

From the Scott Manley video, it looked like it took a second pass for the orbiter to catch up to the lander. I can't imagine that being in the final plan, requiring the lander survive a protracted period on the Venusian surface collecting data to be uploaded to the orbiter. Perhaps the lander will transmit directly to the Deep Space Network (or just Earth), but that's not how lander/orbiter combos typically work (and even less likely on Venus).

My first winter with traction control (and anti-lock brakes) made me feel they were the "cheat mode" for driving in snow. I'd love to have something like autopilot for trips over several hundred km.

Star Trek calls it "teching the tech". You insert "tech" in the script where you mean "magic" and they run it past people in the right fields (trivial for a Star Trek producer) to insert the right words. https://www.syfy.com/syfywire/ron_moore_calls_star_trek But it sounds suspiciously like at least someone editing the script knows what they are talking about.

Presumably you can trade launch success for paperwork (see ULA vs. SpaceX tests for abort testing). F9 was never built around crew rating, so needed much more proof of safety. Now explain just how much testing SLS needs before strapping astronauts to a Boeing safety-certified rocket. Personally by now I'd be throwing away any paperwork from Boeing (and thus ULA as well) and demanding full safety tests. But the Senate (and apparently the House) would never stand for such foolishness.

Isn't planetary density higher than uranium? As in, you'd need some "island of stability" in the far elements to build Kerbol? Metallic hydrogen would also be exceptionally hard to work into the game. Unless the metallic hydrogen was prohibitively expensive, it would just be a matter of gaining the science and infrastructure to obtain metallic hydrogen and then more or less "winning" the game (although to a certain extent so do spaceplanes and in situ fuel production). But the window has closed (if it was ever really open, I doubt it) to be honestly used as a "science fiction" element.

Electric cars certainly do more than just move the tailpipe to another neighborhood. High power electric motors are far more efficient than any ICE (typically at least a factor of 2), let alone their high-powered competition. Hybrids are another story, and allow high efficient/low power ICE engines to combine with electric motors (which could be high power). The problem is "a few generations of nukes" could be an entire century. "A few generations of solar" could be a decade (probably less generations, but still a far, far, faster turnover). One nuke plant is a huge commitment, and it isn't clear who is going to front the money. That said, I've heard there is work being done in India and I can hope for the best. EU data says that "transportation" creates 25% of the CO2 in Europe (power generation 33%). But "transportation" also produces 60+% of the smog. Granted, as long as China (and Germany*?) burns coal for power that will likely be the main cause of all air pollution (although cars won't help). https://www.eea.europa.eu/publications/2599XXX/page010.html * Because nuke plants chill your kidneys** or something, so Germany had to close them down and switch to fossil fuel. And apparently the softest/worst coal they could find. ** Something about German motorcycle riders being afraid of chilling their kidneys. Different places have different superstitions, and the one weird thing I could think of that I've heard Germans believed was "chilled kidneys".

The perfect is the enemy of the good. You're ignoring just how bad an ICE really is, and that a Tesla is more efficient even if the power plant is burning oil. Typically, they burn natural gas which has less emission issues and may have less geopolitical issues as well. You'll also have to wait a few decades before anybody will consider financing a nuclear power plant. It doesn't make sense to tie up the money for as long as it takes to build a plant and potentially be obsoleted by solar improved by multiple generations (that evolved during constructing that nuke plant).

Only if the pressure is constant. The link included (slightly above the linked section) even points that altitude is more important than raw temperature.

If and only if you are sure it is a virus. If it might be strep throat, you need to test it. I'm pretty sure there are some actual means to attack a virus, I don't believe they are a good idea for otherwise healthy individuals... Diseases that survive become less deadly over time. I suspect that more of this is to the disease mutating than the hosts.

Spinlaunch seems to be at least somewhat funded, so might even loose a payload in a suborbital test (I don't think they plan on giving the final "launch" enough delta-v to go suborbital, so presumably the rocket will be doing most of the work even then). I don't think there's even enough in this project for someone like Northrup Grumman (was Orbital-ATK, was Orbital) to buy them and others at bankruptcy prices and put something together (NG might be doing something with Stratolaunch...). There's way too many small launchers for not very much money, and I'd expect that this is the real competition for Rocket Labs (zombie competitors without all the debt needed to fund the R&D to get there).

Kerbal politics, if there are any, doesn't seem to get in the way of your Kerbal Space Program (although it might not be all that great for your popularity. Especially if one crashes down on Kerbal). So it should be a viable option. We also don't know if the unobtanium that makes up Kerbal creates a magnetosphere to drag back all the radioactive exhaust back to the biosphere. Even so, I suspect KSP2 will allow multiple launch sites, and allow arctic launches (expect to have to build the base with kredits/roots).

Unfortunately it is pretty clear that metallic hydrogen isn't metastable, and extremely clear that compressing it to 480GPa (and somewhat more) does not leave metallic hydrogen when the pressure is removed. It doesn't really qualify as a "science fiction rocket fuel" (for KSP2) as we know it almost certainly doesn't work that way.

Anybody know where the "best" part of the atmosphere to renter is (or at least best place to burn off the most velocity)? Is it the mesopause (lowest temperature, about 200K) or the stratopause (higher temperature ~275K, but more than twice the pressure). I suspect the stratopause, considering that all that heat comes from adiabatic heating. If they reach nearly the same pressure, you will be cooler in the stratopause (don't know if they will reach the same pressure). Or do you often have somewhere between each the "best" place?

I'm pretty sure you would still need lots of thrust as your acceleration would suddenly change to straight down (unless you could be supported while building up lateral velocity). You might not need quite as much thrust, and this might mean that SSTO might even work, but I'd doubt it. You could use only vacuum optimized engines, but you could do that from air (and possibly mountain) launch as well. I'd also wonder if the trip down might be more valuable. If you could kill all your lateral velocity in the "right part of the atmosphere" (and then not care about parachutes or retrorockets) you might save more than 1000m/s worth of mass. I'm also unsure of "the right part of the atmosphere": is it the mesopause (lowest temperature, about 200K) or the stratopause (higher temperature 275K, but more than twice the pressure). I suspect the stratopause, considering that all that heat comes from adiabatic heating. If they reach nearly the same pressure, you will be cooler in the stratopause (don't know if they will reach the same pressure).

You do realize that Orion (old boom-boom, not the current pretender) is possible with current technology. I even think it can launch relatively safely from Antarctica. It looks like we can *slowly* do most of what Orion could do in my lifetime with Falcon Heavy/Starship/New Armstrong especially with propellant transported by ion propulsion, but once an Orion is in space everything suddenly becomes trivial. The big difference is that an Orion drive is supposed to be configurable for interstellar travel*. Nothing else comes close to that. * I've seen the .1c number since Carl Sagan made Cosmos, but have never really seen the exhaust velocity of the nukes nor just how much fuel you need to deal with the rocket equation for such a number. I suspect this is a "using unobtanium or all the He3 on the moon" value.

You'd get 1000m/s delta-v (just from the altitude) and should be able to eliminate all aero delta-v. I doubt it would be worth it. This is pretty much the whole problem with stratolaunch. That and it greatly limits the size of the rocket it has to carry.

Apparently not yet (2019 link). https://www.popularmechanics.com/military/weapons/a28985236/future-tanks-powered-electricity/ Trains commonly are, and I'd guess that it would make even more sense for something like the M1Abrams to replace the transmission (from a turbine) with a generator and motor. For diesels it all depends on just how strong your transmission/clutch is (can it knock over trees?). Tanks aren't designed all that often, but I'd guess any designed now (depending on just how clean the paper) would be hybrids.

So all they really need are a lower visibility helmet (more places for cool logos) and that chest dohicky. NASA already does orange:

Perhaps borrow a bit from Morrowind: https://staticdelivery.nexusmods.com/images/110/6441881-1427836536.jpg