SinBad

the only real world monopropellant piston engines i know of are torpedo motors https://www.youtube.com/watch?v=eRCUqcwqu5w they are external combustion axial piston engines. the monopropellant is burned in a combustion chamber and the gasses are routed through the engine. the motor itself is really more of a high speed, high torque compressed air motor. only the compressed air is the high pressure combustion products rather than stored air. on a side note, the fuel (and exhaust) for these things is not something you want to have anywhere near anything biological. nasty stuff.

modern heavy weight torpedos are quite smart weapons. purely from an engineering perspective, they are closer to autonomous submarine robots than the dangerous to use dumb weapon most folks think they are. if properly set up they will way point their way to a target box (an area designated by the user as the area within which the target should be, but non-targets wont be), then try to locate the target using a combination of active and passive sonar. they can even go a further step and be set to identify the target by listening for the unique frequency combinations of that vessel. once acquired, the torpedo will work out where the target is and where its going, then plot its own intercept course aiming at the estimated centre of mass. only when its on the final leg of this course will it arm the warhead. this can be triggered a number of ways based on the torpedos position, depth, the targets magnetic signature, the acoustic changes as it passes under the target. oh yeah, torps dont hit anything. not on purpose. they explode under the keel of the ship making a massive shock wave that lifts the centre of the ship, which then falls into the huge cavitation bubble the blast made, then gets shoved upward again as the bubble collapses. this essentially breaks the ships in half like a toddler snaps a bread stick. if the weapon isnt happy with its position under the target, it will chose not to detonate and instead will try again by driving away and re-homing. if at any point the weapon leaves the target box it will shut down. if at any time it enters one of potentially many safety boxes, it will shut down. all the boxes can be made to move so a box can be drawn around a friendly passing through and made to move on the same course and speed. all this is what these things do without wire guidance. with wire guidance (assuming someone doesn't accidentally tell it bad info) they can be even more effective. also, not saying it isn't so, but satellite signals are quite hard to receive through a dozen meters of sea water with a necessarily tiny antenna... thats all in a huge death tube with almost half a cubic meter of sensors and computers. in a man portable, hand fire weapon you could probably load a set of defaults that would see valid homing most of the time. there is no reason that a 30cm long, 50mm mini torpedo couldn't be made. we have gyros and accelerometers that fit in coins, and computers small enough to process their information into inertial navigators as well. we also are able to pack quite a bit of digital audio processing into a tiny package. the only limitation i can see is the size of the acoustic transducers in the sonar. the smaller they are, the higher their lowest frequency is. lower frequencies have less attenuation than higher ones, so can make a longer range detection, but higher frequencies can detect smaller objects with greater accuracy. most likely such a tiny torpedo would have a detection range of 100 meters or so, but be quite accurate inside that range. thats not to say thats the max range of the weapon, just that thats the range at which it needs to get to before it can automatically home. so if you know that your target can move at 5m/s (pretty average swimming? i dunno? swimming is something for targets to do after they get hit) then if you fire at centre of mass you have 20 seconds before the target is 100m away from your aim point. assuming your mini torp can travel at 20m/s, that gives you a firing range of 400m. call it 350m to allow for the initial acceleration. of course the faster your target, the closer you have to be so it cant get out of the detection range before the torp gets there. you can add in fail safes: like if its within 100m of its firing position and moving towards it, it shuts down. mini torp: do-able.

wait, @WinkAllKerb'' is human? all this time i figure it was a sophisticated chatbot. huh, the more you know... @Kosmonaught, depends on the source of your pain: foot caught in snare, 4/10 downstream current too strong to swim to spawning ground, 2/10 struggling to attain perfect symmetry with your web, 1/10 keep running into out of memory errors, 0/10 cant find the right tool for the job, 7/10 never ending dread at the inevitability of your own death 9/10 the universe is just, soooo big and soooo old. and nothing you could possibly do will ever leave a lasting mark on it 10/10 the above deconstruction of probabilities displays my understanding of what it is to be human. only a true human would be able to reach this level of comprehension.

Look what we convinced our government to do! http://www.sbs.com.au/news/article/2017/09/25/not-nasa-government-says-new-australian-space-agency-will-be-small-profitable I'm both pessimistic and hopeful about this news. our government has a track record of underselling our tech industry potential in favour of mining, farming and retail. lets hope this is a new chapter for Australian Science instead of a one stop shop for other countries to purchase land for building launch sites.

complete control over an element... but its Astatine.

wrong side of the planet for me. but I saw a bunch of photos of folks of all ages and walks of life standing together and using pinhole cameras and dark lenses to look at the eclipse. and even a really cool shot of some pavers under a tree with hundreds of projected images of it (natures pinhole camera: leaves). but hey, I can't complain, we got skylab, so... and then there was a photo of a certain head of state just squinting up at the sun getting a great view of bare faced retinal damage...

I dunno, I saw it pop up and thought of a funny (I thought it was funny) reply.

its what they scraped off the crew capsule floor after that time they hit 45g on re-entry... the mystery is where the crew went, and where this goo came from...

true, but are such systems capable of intercepting objects over the oceans? are such technologies in use in this scenario? if you came down over the pacific for example. purely ballistic, pulling out and into an ocean hugging randomly chosen direction as late as you can survive. then get out of the area as fast and as low as you can. would a shore based interception system be able to get ordinance on location fast enough to still find you there? remembering that at this time they need to intercept a supersonic/hypersonic (depending on how advanced 'advanced civilisation ' means) seaskimmer, or if they are really slow they need to find a stealthed sub sonic sea skimmer rather than the expected high speed high altitude target they were designed to locate.

save the hiding for after reentry. come in fast and hot. fast and hot enough that interception during re-entry is near impossible. then hit the deck (under the radar) over a large ocean and do a few minutes at high speed to get away from the projected landing site. then you can slow down and start using more terrestrial stealth solutions. but at some point you are going to have to land and hide or dispose of the craft. thats probably the fiddly part as the farther it is from eyes, the farther you have to travel overland. the farther you need to go, the higher the need for a vehicle, which you either need to bring with you (making your craft larger) or have arranged to be waiting for you by some local agent, complicit or otherwise. if you want to be fancy you could re-enter at noon and use an ablater material that will emit the same spectrum as the sky, or do it over a storm (also good cover for sonic booms). the point is, they know something arrived, but they don't really know what, or where it is. after all, you have a whole planet to get lost in. even better if there is a high population that is used to strangers visiting from other cities.

Dont underestimate infrared laser for blinding folks. They are more dangerous at lower power levels than visible lasers because they dont trigger the blink reflex, which at low power levels is often what mitigates the potential damage of visible light lasers. At a tangent, i personaly think microwave lasers (masers) are the way to go. Thanks to nearly 70 years of radar research, we are rather good at converting electricity into microwaves (much more efficient than lasers) with far less heat produced. We also have a lot of experience with redirecting, lensing, pulse modulation and beam forming at tens of megawatts of power output ( for systems that transmit that power output every few seconds without extraordinary cooling). Additionally, microwaves couple with metals very well so barring widespread use of tupperware branded plastc armours, more of the produced energy can be dumped into the target.

line 1/10 error: index out of bounds. failure to create new instance of object: human. this is text displayed on a video device that was input by a human for the purpose of communicating to other humans the humanity of the human who originaly encoded this text.

@cubinator your name makes a lot more sense to me now... I made a thing, things, for dinner. I took cold mashed potato, then mixed in an egg, some corn flour and lots of shredded mozzerella. Made it into ping pong sized balls and deep fried them. Ended up golden and crunchy on the outside, soft and fluffy inside with melted cheese stringing out with every bite. Made the homemade cheeseburgers kinda plain tasting in comparison though.

where is the f-18? those things are incredibly manouverable. also, last I checked, the air to air combat requirement (the thing that makes it a fighter) for the f-35 had been dropped because it was so horrible at it.

neutron stars involed in collisions would likely cause a gamma ray burst. as we are here to look at the debris, I reckon it wasn't a neutron star.

That was a well spent 5 minutes

Rule 33 of Theoretical Physicists: hypothesised to exist by Plato , physicists have never been observed in nature and not be possible according to modern science. Pygmy Marmosets

Rule 7 of programming: never devide by 2 when you can multiply by 0.5 Loading a dishwasher

why not stage it... in reverse. assuming a mothership, how about a delivery/retrieval vehicle serviced by whatever fueling infrastructure the mother ship depends on? so the d/r vehicle grabs the lander, heads to to low orbit. then it does the re-entry burn, drops the lander and boosts back up to low orbit. the lander goes into a semi-ballistic glide until its slow enough for a nuclear thermal turbo jet (no fuel required, just air) to work, then it can hug the ground to its destination for a landing. once there, it starts compressing/liquefying air (worst case scenario, the hot exhaust from the nuke jet can be routed into a compressed air powered reciprocating engine coupled to an air compressor). lift off on the nuke jets again, then up into a a sub orbital flight with an apoapsis at low orbit (compressed/liquid air sent through the nukes at high altitude to maintain thrust.) timed to meet DR vehicle. DR vehicle does a retrograde burn, catches the lander around apoapsis, then boosts them both back to the mothership. no fuel is used in atmosphere, allowing long in air loiter times and very high cross range capability. that would help a lot when trying to match a suborbital hop with a low orbit rendezvous. because the only time the lander needs vacuum propellent is on its way up, and the excess compressed/liquid air can be discarded before docking, the mass the DR vehicle needs to brake and boost is very predictable and aside from payload (which should be known by the time it hits space) is always the same. this removes the need for efficient engines in both vacuum and atmosphere on the same craft by splitting it into two vehicles, each in its element so to speak.

I think as our own technology develops and we start looking at utilising mass and energy on solar system scales we will begin to see evidence that much of the natural universe around us isn't natural after all, but rather the debris left over by the the expanding spheres of ETs exploring thier way to a bubble bursting extinction. I mean, just look at our solar system. Murcury is mostly metal. Almost like someone needed somewhere close to an energy source to park the core of a small planet while they built new ships. Venus is sluggish Mars is shriveled The next planet had its core mined out Jupiter has retrograde moons

Dehavilland vampire for me. Insanly manouverable twin boom jet fighter? Yes please. For similar reasons im a fan of the F-18. Those things have control surfaces on the leading edge of the wing As well as the trailing edge. Aircraft that would benefit from having the squishy pilot removed before flight.

Think of the drag as the end of a lever attached to COM. The force applied to the end of the lever is in the retrograde direction. Suppose you have drag in front of COM, if the craft is flying with its nose pointed a few degrees above prograde, which isnt uncommon. When that drag is activated, the force on the lever will move the nose further away from prograde, the further away it gets, the stronger the force. Now if the drag is just behind COM, it has the opposite effect in the same situation. It forces the nose closer to prograde. The further away it is when you start, the greater the force. If your drag is level with COM, but off to one side instead, it will start with inducing a yaw towards the drag. But because its level, it will start with maximum force which will reduce the more the craft yaws from prograde. Thats cool, it can make for a craft thats quick to respond, but it also makes for a craft that cant make small yaw corrections. The further behind COM your drag is, and the closer to centre line, the more subtle its effect will be, making small corrections with small surface movements much easier. If you need a large correction, make a large control surface movement. One other thing, thats related. FAR also models shadowing, so if you have a drag rudder above the wing mirrored with one below the wont generate equal drag in all situations. A nose up orientation can cause the upper surface to be shadowed at some speeds, which means when you try to yaw the bottom surface creates more drag which pitches the craft as well as inducing yaw. So be aware of that effect as well. Tldr; the further behind COM a drag control surface is, the more sublte of movements it can induce. Forward of com often ends up with a runaway effect, behind COM self corrects towards stability Watch out for control surfaces loosing their effectivness if they are shielded from airflow at certain speeds and attitudes.

FAR models the shock cone produced by the crafts nose at supersonic speeds. The angle of the cone depends on how fast you go, faster flight having a narrower cone. Anything that protruds from the cone (like wing tips) will creat a shock cone of its own. When those new cones intersect with the original cone, you get a lot of turbulence/drag and heat. So for very high speeds, short wings are needed to stay inside the cone. To keep the required surface area, that means wings that are wider front to back. A supersonic flying wing would probably look more like a long narrow arrow head rather than the broad triangles of current subsonic ones.

Are there supersonic flying wings? If I recall, the drag profile becomes very Important supersonic. Also having wingtips outside the shock cone created by the nose causes some horrible effects, which is why supersonic tends towards stubby wings that extend down the fuselage a long way. I'm not sure the typical flying wing geometry has enough sweep to keep the whole thing inside the cone.