wumpus

It probably has something to do with the "Perseverance" name given to crew-1. I'm guessing that it also means that they are getting much closer to the all-seeing eye of Mordor (but that's *every* NRO mission, so little new).

It (the oldest parts anyway) is 20 years old already. Even 10 years ago it required nearly all available astronaut/cosmonaut time dedicated to repair/maintenance of the ISS (the crew is slightly larger, so presumably they have 1 man-day of non-maintenance work per day). By the time they straighten the politics out (assuming Ms. Shotwell handles all the negotiations and takes all of Elon's communication devices, otherwise never) it will probably be in a state worse than Mir when it was finally deorbited. It would be far easier for Spacex to put up their own space station than to acquire the ISS. It would probably be a lot cheaper than maintaining the ISS as well. Besides, that's pretty much how they do things anyway.

The coal industry managed to kill nuclear while releasing more radiation than nuclear ever did (I think they even do per Watt, including Chernobyl). You don't think solar and wind won't do the same? More likely, it will simply never be economical to build fusion power plants, and it will never make sense to subsidize them until they are (although I'm sure that plenty will expect such to be done). Where? There's no way you will get the loans in the US (the dollar per Watt loses even to coal, let alone the rest). In the EU they have perfectly good nuke plants shut down. They aren't at all popular in Japan. Are China and India building them? It would make tons of sense for them to do it, but I haven't heard of it.

No science here. But possibly being right by accident... Attitudes will be similar if space stations require Baikonur access. Altitudes can be matched (eventually) by any station with similar attitude selectively not firing station keeping rockets until they are all at the lowest common orbit. Or you could move the lowest one up (using up all onboard stationkeeping fuel) to conserve fuel. And it would be unlikely that all of them had enough station keeping fuel (let alone air) for the duration. If you can't MacGyver together a crash pod to survive a 70mpg deacceleration with years of warning, you don't belong on a space station. There couldn't be that much fallout, although I admit I know almost nothing about cobalt bombs (bombs designed to "salt the Earth" during the cold war). Wildlife around Chernobyl generally does better than in places near humans, although presumably predators find animals with cancer before humans notice them. Pretty much by definition, the worst fallout decays the fastest, leaving low-level stuff after a year (and the worst should be gone within a few days). Also, assuming the space station can be reached by a straight shot from Baikonur, pretty much everywhere in the world is an option: The Nile river valley obviously was a great place to live in ancient times, along with anywhere with a sufficiently mediterranean climate. New Zealand might be glowing less, and presumably less heavily mined for future generations (well, less "used up" by industry and agriculture). Or you could be like the Pilgrims (early American colonists) and essentially graverob a fallen culture to build your own (presumably the least glowing and most intact cities RADAR/LIDAR can find). And no. If things are glowing, you already have a lethal dose of radation poisoning and only have a few minutes (in the unlikely event you are still alive) left. Stuff just doesn't glow like that (nor is there a likely path to allow humans to mutate to "see" radiation).

The fact that I watched a lot of Superman as a kid doesn't mean I expect physics to allow human flight via a cape. Same with SSTO. Air breathing is probably the only way to go, but don't bother adding nuclear or antimatter to it.

So if you are using water you get 2m long, and we'll assume a 2m diameter rocket (width of a 737-200 fuselage that showed up from googling), so 6.28 cubit meters of shielding or 6.3 tonnes. Since shielding is mainly all about mass, I'd simply use that mass even if you use lead or depleted uranium. And how much will this reactor mass? And just how are you planning to go from zero to supersonic (and how much will that mass?). All those tonnes add up, and need to be sent to LEO. But the fuel an airbreather burns only has to be accelerated until burned.

There should be significant differences between Geosync and starlink (or any competitor). Weather is likely to be the same, as they both go through the same atmosphere. Latency is far lower. Bandwidth should be wildly higher. With Geosync, there can be one geosync satellite ever few degrees, and all the bandwidth from the hemisphere goes through those satellites. With starlink, the congestion is a completely different story. If the satellite you are using can be reached by Vancouver (and if Vancouver, Seattle is also an issue), Toronto, or possibly a big military base, then you will have a lot of congestion. If you are sharing your area with a bunch of caribou, you shouldn't have any problems. Data caps are entirely up to starlink, and I'd worry that they would base them on urban use rather than their more effective areas. It should be wildly better than current satellite internet. When people think about ditching their own ISP and moving to starlink is where things fall apart. If even Tater is willing to stick with DSL (I'm assuming that his area has rather low population density), that's a good indication of just how limited starlink is compared to any other non-satellite ISP. My understanding is the whole thing will make a profit just off military and Wall Street-City of London-Shanghai communication. Rural internet is mostly for PR and sucking up subsidies. But if you are using satellite internet already, expect a big improvement (although I can't guess what the caps will be).

First place I would look at is the X-43, an airbreather that managed to maintain in excess of 2,300m/s (it did rather well accelerating around 1000m/s, but that was a different flight and likely a different configuration. The idea that you could shield a nuclear reactor and get the whole thing to weigh significantly less than the liquid hydrogen needed to get to LEO is extremely unlikely. The kicker is that for a fuel powered rocket, you get similar thrust the entire flight, but your mass steadily decreases through the flight. The mass of the reactor would stay the same. There was a proposal for a nuclear bomber (and I'd suspect a Soviet program as well that I've never heard of) during the 1950s or so. I don't think that it is remotely possible for it to get into space. Your obsession with SSTO simply doesn't work well with "known physics". If you really want to understand the rocket equation, not only is KSP a great way to learn it, but it is on sale 75% off ($10) (until Monday, November 1, 2020. Probably noonish EST).

Saturn V. Born in 1969, and I'm pretty sure I saw (and remembered) Skylab going up. Of course I didn't know the difference between that and the Saturn 1B that brought astronauts to Skylab and finally Apollo-Soyuz, but I watched them every chance I could get (which was what, 4-5 Saturn 1B launches in the 1970s?). For unbuilt rockets, I remain loyal to Orion. The shear scale of the thing, combined with the ability to use fusion power with only 1960s tech (20 years away, pah! We've got all the fusion we need already!) makes it read like over the top sci-fi (but it really could have been made, and probably not much more than an Apollo budget. Or maybe the Nimitz's budget, but project power over the entire solar system...

The point is that Bennu doesn't have to be round thanks to hydrostatic equilibrium. If it is a collection of relatively small rocks held together by gravity, they would have a chance to reform every time it is perturbed. Granted, not all of those perturbations will lead to roundness (which might get inserted into the planetary definition), but I'd expect them to statistically lean that way and lead to the shape we see now.

As far as I know, at least one satellite performed a proof-of-concept maneuver with an all-electric motor. The key is that it was orbiting a planet with a magnetic field (Earth) and that it effectively used that field to move around. Such actions might be useful for stationkeeping, and possibly moving microsats.

This thread had a lot about lasers. I also included a calculation that for 60MW of power, you need heatsinks roughly the size of the ISS. And this assumes E.E.Doc Smith levels of tech (4000K Carnot heat engines, 3600K radiators). I assumed that any laser-based (or possibly neutron-beam based) combat would involve overwhelming those lasers. Ideally you would have to attack from at least 3 orthogonal angles, and you would have to attack from 3 non-planar angles to have any effect at all.

Somehow I suspect this is the reason the company is no longer in business.

Bennu is considerably smaller and considering how loosely it appears to be held together, may well be gravitationally rounded. Those are good goals. I was greatly irked to find out that animals that could crossbreed and produce grandcritters could still be separate species. It took me some time to realize that the fact that since such simply didn't happen in nature (typically due to distance), it was silly to allow an experiment to prove they are the same species.

I'm failing to see how any photons after the first bounce are not "free momentum". Now granted, it is a special case where two ships want to go in diametrically opposite (or will agree on gaining momentum in opposite directions, to be corrected after they are too far apart to be useful). If you have to drop a mirror (even a small amount of mylar, forgetting for the moment that you have to keep it aligned to the spacecraft and rigid), you will likely lose every Isp advantage that photons have over ions, without remotely gaining any power advantage over ions. And once you really get going, even if you can manage to keep the beam focused (you can't), expect to lose energy as each bounce shifts the photon more and more red (the low momentum side of the spectrum). So think of it as a very silly first stage, using a method of propulsion that should be for last resorts in some theoretical last stage. But the extra bounces are pretty free.

Why not Scott? Because for this forum at least, naming Pluto a planet gives (33434)Scott Manley an equal shot at being a planet. - (33434) Scott Manley is more or less a very large asteroid, but big enough to be in the "planet spectrum".

We've known since Voyager (or possibly Pioneer) that "dodging asteroids" was far easier than dodging satellites in LEO. I think the ISS has had to maneuver to avoid a near miss multiple times. I don't think any spacecraft has had to dodge an asteroid (and most of them can't and make it through). It would make the classic video game "Asteroids" a lot less fun if a single shot turned a "large" asteroid into a fine mist small rocks, although I suspect the "boulders" such as Mount Doom are in fact actual boulders. I don't think we can tell from Osiris Rex's data, but it would be great if we did.

Back in the 1990s I briefly worked at a tiny startup that took this to extreme levels. Called Freewing (then Freewing Aerial Robotics, they were getting into drones), the whole point of the company was to build airplanes whose wings would rotate freely around a shaft (the angle of attack would be near zero, the wings would simply rotate to be parallel with any airstream). The only way to stall the plane would be to drop down to stall speed, but in practice this wasn't true as the only way to use flaps would be to lock the wings. The aircraft (drone) I was working on (just the telemetry, I knew even less about aircraft then than I do now) was designed (more like architected, we had a grad student doing the detailed engineering) by Burt Rutan and the basics was that if the wings could rotate freely, and the propeller was fixed to the fuselage, you could angle the propeller (and thrust) by an actuator in the tail. I'm not sure if they were still around by the Iraq War, or partnering with the French closed that market, but they didn't last much longer. It was pretty much stuck with being a drone unless you want to takeoff/land while sitting at a 60 degree angle pointed upwards. But one of the claimed advantages was that it was much less effected by turbulent air, especially in smaller planes. Since the wings could slough off any sudden change of direction of air, that didn't leave much else to be pushed around.

Just that somebody figured out that they could make a ton of money on short range jet transport. But I doubt they significantly influenced jet design all that much, I doubt there is much point in making the fuel tanks significantly smaller on anything that doesn't already cross continents/oceans.

Go talk to the VP of Sales to Southwest. Although I suspect even he wouldn't try to have a 737 variant designed with shorter range.

If GR is correct, anything beyond the event horizon is non-falsifiable. You might as well claim that any claims past the event horizon aren't scientific (or at least can only be so if GR is invalid in this case).

And it would only make sense for long distance flights where the weight of the fuel (kerosene) is up to (or more) than half the takeoff weight. And that really interferes with hydrogen's other huge issue: low density. You'd have a huge amount of plane that would be nothing but fuel tanks. But for at least those long flights, it would easily beat kerosene (I think. Methane is cheap, but I'm not sure how efficient the whole process is in turning methane into liquid hydrogen).

Just one? Is the other out on reconnaissance?

The problem is typically described as "fuel leaking due to need for expansion in the fuel tanks", so I really don't know how hot the interior of the plane was (probably still top secret) nor the fuel tanks. But designing a cooling system with no external heat sink is a challenge and likely means that only the cockpit and other absolutely critical areas get cooled (possibly just the flightsuit). I wonder if it would make sense/even be possible to have "clean" intakes just for cooling air? I think that is central to the Sabre engine... but I'm not claiming much about Sabre's effectiveness.

The Blackbird needed ramjet action to hit mach 3. I'm not even sure the compressors were running at that speed, but most of the compression was thanks to aero. Aside from that, I can't think of a single reusable ramjet. Scramjets are still in the research phase: I'm pretty sure that X-43 was reasonably successful in the mach 6.8 range, and could presumably be a third stage of an effective rocket. But that will be used if and only if it is worth designing a rocket around a few tens of thousands of dollars (per launch) in fuel savings. Right now that is some really high fruit. Ramjets have seen much more use, but need some other means of getting them up to the mach .9 or so they need to function (and of course crewed aircraft would preferably not deadstick it back home). As far as I know, only the Blackbird had a reusable ramjet engine, typically they aren't, and probably get away with much cheaper ablative engine liners. Not to mention just how hard the Blackbird engine design was (no idea if computers would make the design easier. They certainly won't help at all in making the thing easier to machine). I'd like to think a modern blackbird could be made that used normal jet fuel, and possibly a steel [stainless?] body, but most of the problems would be just as hard as in the 1960s.