This thing, with 16 motors introduces many more points of failure. Very cool, but practical? No. And definitely not useful for real world applications. Not yet, anyway.
Hmm: think again: A normal current helicopter with some hundred moving parts around the head- and the tail rotors under heavy load and wear should be better than 16 moving parts running smoothly on ball bearings? The only critical part here is the flight control software, everything else is damn simple technology, compared to any existing heli design. It also already contains redundancy, 4 out of 16 motors are allowed to fail...
First, let me say that I agree that the pilot should probably be under the blades, although I'm more concerned about stability. Lots of people have commented on the possibility of broken propellers, and yes, that is something to consider. However, I'd say it's less of a factor than most people on
As far as I understood, the pilot position is wanted above, because it allows to use a typical parachute safety, as in many ultralights. This is impossible with normal helicopter setups, due to the rotor on top. As for stability: without the electronic controller this beast will be inherently instable (doesn't matter where the COG is). With the controller the neutral state is, that the thing balances itself, hovering on the spot. With some reasonable controller (GPS etc.) it would even stabilize it's absolute position. Therefore it is relatively easy to fly, especially in contrast to classic Helicopters.
No, it's not. On a helicopter, there's only two rotors, and they're mechanically linked together because there's no reason to spin them at different speeds (you control them by altering the pitch of the blades).
Exactly this is not necessary with these Brushless E-Engines. The control is done by some gyros and electronics. No complex pitch control as in helicopters. No horrible mechanics, required to be maintained every day. No redundant hydraulic systems, no prove that the system remains halfway stable and controllable by a (extremely experienced) pilot, if the single (turbine) engine breaks and you have to autogyro. This prototype is already able to fly up to 20mins with the current LIPO batteries. It stabilizes itself, it weight is about the same as the human on top. Engines Props and Batteries are nothing special, taken from the shop. Even if some of them break, the beast will be able to be landed.
... then send thousands of workers right into the heart of it to put a big concrete casket over it. without protective gear.
What was a viable alternative?:
The did what was necessary and useful at that point (*after* the reactor went fireworks). Protective gear for gamma rays did not exist and does not exist today.
The PBR is supposed to be self regulating -- higher temperatures reduce the rate of the reaction, so even a total loss of coolant means that the fuel heats up to some steady state temperature and will stay there forever. What happens to a TWR if the coolant flow stops for any reason?
The heat is self-regulating the chain-reaction only,
But the reactor will still heat up to some state above 2000 Degrees and you reactor structure needs to dissipate the generated decay heat at that point. It should not melt, crack (and let any air or water in) for possibly a loong time.
"the two biggest advantages of the fast reactor design is that it requires no spent fuel pools and uses cooling systems that require no power to function"
A cooling system without power for magnitudes like 10MW does not exist.
You may have a primary sodium circle, but you still need to remove the heat from it by pumping water through a heat exchanger and removing the heat from the water. If you don't do this, the sodium will start to boil at 900 Degrees and then the pressure will break out and be very reactive.
I don't think the melting point of beryllium would be a problem. The moderator is inside the sphere, not on the surface. The outer shell is ceramic.
No, you misunderstood the nature of the pebbles:
In the current designs only the Thorium/Uranium mixed with some small amount of carbon is embedded into a ceramic shield with 0.5mm size
(TRISO-Particle).
15000 of these tiny spheres are then embedded into graphite balls of about tennis ball size for mechanical handling.
The graphite in the outer ball is moderating the reactor and transfers the heat to the He-N Gas flow.
Graphite is also meant to 'lubricate' the movement of balls inside the reactor, but apparently this does not work in the hot and dry atmosphere.
Therefore replacing graphite with a metal would leave you with a molten mess.
There's nothing wrong with teenagers that reasoning with them won't aggravate.