sevenperforce

The magnetoshell aerocapture design is only good for capture from hyperbolic trajectories, not for proper re-entry.

And crash goes the gateway. What did we expect?

My gut says #BoomerRemover is a real trend on the left while #boomerpox is trollfarm. The far right gets all its power from Trump.

If you engineer a highly contagious virus that disproportionately kills old people and sick people, then deploy it in China with a vector to the US, you accomplish a variety of things: Reduction in the long-term costs of end-of-life healthcare (because old people are dead) Reduction in the long-term costs of chronic-disease healthcare (because sick people are dead) Reduction in the right-wing voting population (because Boomers are dead) Increase in support for socialized medicine (because omg pandemic) Distrust in the current administration (because obviously he was going to bungle it) Distrust of protectionism (because it didn't help here) If I was a conspiracy theorist, I would say that all of these accomplishments would benefit the far-left in the United States. I am not a conspiracy theorist, however, and I think this is preposterous.

We really need a less efficient but more modular ACES.

Re-entry is the problem. For the record, I agree.

Mortality among those who sought medical care is 34K/16.5M or just over 0.2%, which is what I said. SK has socialized medicine and took proactive measures to prevent spread. The U.S. has neither.

These numbers are coming out so fast that I think we're treating deaths and infections as though they are linear when we should not. Take Italy (which, while more urban than the US, had an initial posture very similar to the US's). Right now they are reporting 827 deaths off 12,500 infections, which is 6.6%, but we do not know how many of those 12,500 infections are going to go on to die in the next few weeks, or how many total infections they'll have by the time the death toll ticks up. Pretty soon we will be running into appreciable fractions of the entire population. Death rate is also extremely hard to pin down because it depends heavily on whether the hospitalization rate exceeds triage carrying capacity. If we cannot get total case estimates, it is fairly straightforward to compare based on medical visits. We know, for example, that the seasonal flu's average death rate of 0.1% goes up to 0.2% among the population who require medical treatment for it. Conservatively, the numbers out of Wuhan suggest 2.3% of those who require treatment for coronavirus will die -- 11.5x more lethal. During a mild seasonal influenza outbreak with ten million total infections, you end up with 13,000 fatalities. Based just on this, it's easy to estimate the number of U.S. deaths based on how much of the U.S. population becomes infected: 10%: 489,000 deaths 20%: 978,000 deaths 30%: 1,467,000 deaths 40%: 1,957,000 deaths 50%: 2,446,000 deaths 60%: 2,934,984 deaths 70%: 3,424,000 deaths 80%: 2,913,000 deaths And that's if COVID-19 is no more likely to put you in the hospital than the seasonal flu. COVID-19 will likely infect between 40% and 70% of the U.S. population.

@kerbiloid and I were discussing the pure-rocket mode. That being said, a hydrogen airbreather has a much higher specific impulse and usable thrust range than a methane airbreather. Whether you're actually combusting your airflow or simply using it as added reaction mass, you want your exhaust velocity to be at max. A NERVA-type NTR pushing methane would be able to generate net-positive thrust in its airbreathing mode up to 4.6 km/s; if it is pushing liquid hydrogen it would be able to generate net-positive thrust in the airbreathing mode beyond orbital velocity. If you're landing, that is less important and you do want more thrust, which methane will certainly give you.

It comes down to atomic mass units. Diatomic hydrogen is 2.01 amu; a methane molecule is 16.04 amu; diatomic carbon is 24.02 amu. Diatomic hydrogen is constant at 2.01 g/mol. When a pair of methane molecules disassociate, they release four molecules of diatomic hydrogen and one molecule of diatomic carbon, going from 16.04 g/mol to 6.41 g/mol. So hydrogen still has 3.2 less atomic mass. Molecule velocity scales inversely with the square root of atomic mass so pure hydrogen will be pushing about 79% more Isp. Exhaust velocity squares directly with the square root of temperature so your methanuke would need to have a combustion temperature 3.2x higher than a comparable hydrogen nuke, just to break even. You'd need to get over 10 kK to get diatomic hydrogen disassociation.

Methane disassociates at 1000-1200 C, so well below rocket engine operating temperatures. This helps the specific impulse a little.

I doubt that, since specific impulse in simple terms is a measure of how efficient a rocket is at converting it's propellant into forward thrust. Shooting out several tons of propellant per second is less efficient than a rocket that could shoot out a ton of propellant per second for the same amount of thrust. That is my point. An antimatter or fusion reactor rocket using methane as its propellant will use more for the same amount of thrust than a solid NTR using hydrogen. If you're pouring antimatter directly into your propellant flow as it enters the combustion chamber (or annihilation chamber, in this case), then you can gin up the chamber temperature higher, but you'd have to really get the temperature ridiculously high before the propellant performance of methane would exceed the propellant performance of hydrogen. You would be forced to use methane to regeneratively cool the chamber, of course, but at some point the heat capacity of the methane simply isn't enough. Specific energy is the measure of how much energy your energy source has per unit of energy source mass; specific impulse is the measure of how much thrust your rocket can produce using each unit of propellant mass. They are linked when you're talking about chemical propellants, but not directly linked when you move away from chemical propellants. Well, it means that the dry mass of the energy source is lower. Which technically means it is possible too use less propellant, but not for the reason you're thinking. Entry and descent do not require engines. Landing is about TWR, not specific impulse, since you by definition need only a tiny amount of dV. The best way to land is chemical airbreathing without nukes at all; save your nuclear cycle for where specific impulse is needed.

"If you feel sick have a doctor check you" Check you for what? If you're in the U.S., there are no tests, because the f#&$!@ing President shut down the pandemic response office early in his term, because "that's never going to happen" so who needs it? Rationing healthcare is awful. Rationing tests is the apocalypse. If the government cannot react appropriately to a health crisis then you either need a new government or a new form of government. Triage nurses should not be tasked with deciding who lives and who dies.

Dicking around on KSP forums maybe

With some modifications I don't see why not. Use several reactors for different modes. High thrust low ISP: Use a solid reactor or reactors (however many it takes) encased in quartz, let UV rays heat the solid propellant for max thrust. Useful for boosting. Drop used tanks. Reentry: Plain nuclear airbreathing should work great, and if not good enough, augment it with chemical nuclear propelled propellant at the same time. If reactors can be made small enough we can use several. At once for different engine modes. The possibilities are several. Wait, what? In what universe can you have a nuclear thermal reactor with solid propellant? The whole basic, underlying concept of a NTR is that the liquid propellant flows around the reactor, cooling it while absorbing as much thermal energy as possible. NTRs (and, for that matter, antimatter reactors) are not magic; it's a matter of how fast the propellant leaves the engine bell. You can get better specific impulse by pushing hydrogen through a solid NTR than by pushing methane through an antimatter or fusion reactor. I don't know what you think is so amazing about antimatter. It has hella specific energy, but specific energy is not the same as specific impulse. You cannot "drop used tanks" if your propellant is solid fuel. It makes no sense. "Nuclear airbreathing" does not help you on re-entry. Re-entry is a function of cross-section, control surfaces, and thermal properties.

Building an SSTO is straightforward enough, and nukes (esp. airbreathing nukes) makes it almost trivial, once you have the powerplant. The better your propulsion package is (smaller, thrustier, higher-efficiency), the more margin you have for other parts of your spaceship. But the problem is not getting into space; it's getting out of space. EDL -- entry, descent, and landing. Bucknell's airbreathing SSTO is lovely but it has no good way of getting back down to the ground.

Given that I grew up in a conspiracy theory, I am always very skeptical of conspiracy theories. But I can see why people would believe that COVID-19 is some sort of nefarious plot. A virus that causes only moderate symptoms in most so that it is transmitted freely, infects 70% of the U.S. population, and then kills off only the old and the already-ill. Reduces the cost of socialized healthcare (because you just killed off all the expensive ones) while increasing demand for new healthcare solutions. Embarrasses the current regime, etc. etc.

As failures go, that is a good one. "Our robot determined that conditions were bad and therefore followed protocol in sacrificing itself rather than putting another robot at risk."

Love it.

The article mentions similarity to the Dyson bladeless fans -- they say that the bladeless fans can't produce meaningful thrust, but theirs can. Dyson fans use a compressor to suck in air, pressurize it, and spit it out in laminar flow, entraining the surrounding air. This system uses a gas generator -- essentially a small jet turbine -- to produce the pressurized exhaust for the same basis, but evidently uses a differently-shaped inlet to make entrainment more thrusty. I'm already thinking of an old idea I had about four years ago, illustrated here and discussed on the forum here (images dead so go click on the other link to see what I'm talking about). If an aerospike engine is a conventional bell nozzle engine turned inside out, this would be an aerospike engine turned inside out again, but leaving an inlet at the center. In other words, the same design as the Jetoptera propulsion unit, but with tiny linear aerospike nozzles all along the duct rather than just a pressurized air outlet.

So I truly believe this is MY idea and I should definitely get credit for it...I've been doodling extensively on these designs for years now! https://medium.com/predict/breakthrough-fluidic-propulsion-system-could-power-the-drones-aircraft-of-tomorrow-a6fe60da8f89 A new aerospace startup has developed a propulsion unit which uses a combination of laminar airflow and the Coanda effect to produce dramatic levels of thrust -- enough to enable VTOL -- without exposed fan blades. Just imagining all the ways this could be used to power an air-augmented rocket....

A major world leader said today, "So the same vaccine could not work? You take a solid flu vaccine, you don't think that would have an impact, much of the impact, on corona?" Not going to say who it is lest we delve into politics but.... .....Odin help us.

There is a confirmed case in my city (one of the biggest/most prominent cities in the US) and the official word from the public health department is that there are no cases.

I am guessing it is a rough way of saying "don't mess it up". Nah, nothing here suggests that they plan on testing SN2 to destruction. He just means that SN1 exposed a flaw and they are going to quickly put together the corresponding parts of SN2 in order to make sure they've fixed that flaw since.

I noticed this too. Technically encouraging, I suppose.