sevenperforce

No matter how much the treadmill accelerates, it will not be able to prevent the plane from moving. Here's the experiment. Stand on a treadmill while wearing roller skates. Turn on the treadmill and use the grips to hold yourself in place, so that you are stationary while the treadmill rolls underneath you and your wheels spin. Test this at varying speeds. Does the speed of the treadmill affect how hard it is to pull yourself forward?

The next B5 flight, period, will be either Telstar 19V, in late June, or the final Iridium NEXT in July. For all we know, B1046 (the first B5 from May 11) may be refurbed in time to fly the final Iridum mission. I doubt it, though. I would not expect a "third flight" of any booster until at least Es'hail 2 in August or SAOCOM 1A in September.

Does the leg say "Yanny" or "Laurel"?

The new Roadster has the best acceleration of any production vehicle in the world, so I can't imagine it takes very long to get up to 250 mph. Obviously not enough to get off Pluto or something, but Mimas should be achievable. Might cook the motors in the process but you only have to do it once.

Wait, what?! A car can be winched in any conceivable direction without regard to whether or not the wheels spin, or what direction they spin in.

Teslas are software-limited to a top speed of 155 mph, but the new Roadster is able to reach 250 mph with the limit removed. 250 mph is about 112 m/s. Escape velocity of Ceres is 510 km/s so that's within half an order of magnitude. Varuna's escape velocity is 380 m/s. Miranda, Uranus's innermost moon, has an escape velocity of only 193 m/s so its orbital velocity is around 136 m/s. Mimas, the smallest gravitationally-rounded object we've discovered, has an escape velocity of 159 m/s and an orbital velocity of 112.4 m/s. Any smaller than Mimas, and you get into irregular moons. Hyperion could be escaped at a speed of as little as 45 m/s if you start from the right place.

Yes. How? The car is in neutral. Nothing the conveyor belt does can possibly prevent the winch from pulling the car forward. This is where my brain starts to melt. It's one thing to say, "The airplane on a treadmill problem is just a case of mistaken interpretation; one group is trying to show that planes don't use their wheels for propulsion while the other group is trying to insist that a stationary plane cannot take off." But....this? Another example: Put on roller skates. Stand on a treadmill. Hold onto the treadmill grip. Turn on the treadmill. You will now need to hold onto the grips more tightly, since the treadmill acting on the roller skate wheels is pulling you backward a little bit. Turn up the treadmill. Does it get harder to hold on? No, because the rotation rate of the wheels does not alter the force acting on the skates. Turn up the treadmill even more, faster and faster. Does it ever become impossible for you to pull yourself forward against the direction of motion of the treadmill, using the grips? The answer is no.

An amusing exercise: using the theoretical maximum velocity of a Tesla with no air resistance, which worlds in our solar system would allow it to jump into orbit? And which ones would allow it to jump into an escape trajectory altogether? Of course the lack of downforce would be problematic to say the least....

If a plane is on a conveyor belt in the forest and no one sees it, will the Yankees win the World Cup?

General consensus on landing leg removal is that they're taking it apart to inspect anyway, so taking the legs off in the post-landing state gives them better data than refolding.

Yep.

Obligatory: Also, related:

Of course, on Titan, propellers make a ton of sense. On Titan, you can fly with wings strapped to your arms.

A touch chilly though, I reckon.

It does eliminate the problem, to a degree. Their flight profiles do take a nearly perpendicular trajectory on landing, and the stage goes transonic at high enough altitude that the sonic boom is very muted. It's still audible from a great distance, but it's not the tooth-crunching, bone-shaking, window-shattering crack of a low-flying supersonic overflight. Recall that sonic booms are directly analogous to the bow shock of a speedboat. If you are in the water and a speedboat passes nearby at high speed, it is going to produce a large wave that will very likely swamp you. However, if the speedboat is moving directly toward you and then stops before it reaches you, the bow shock will weaken and fade to nothing very rapidly.

Presumably they want to inspect for damage before refolding, which conceivably could cause additional damage that would obscure the source of the original damage.

The image above is the outside.

Waaaaaaaaa?? I suppose that if they plan on taking this booster apart to nuts and bolts for inspection, it makes reasonable sense to take the legs off now and examine them separately. Odd. The old legs went on white and came off black. Now these go on black and come off sandblasted-white. I wonder if the white is from ablation.

The incidence angle of a supersonic bow shock has a major impact on its ground effect. A supersonic vehicle overflying a populated area produces a sustained shockwave that travels linearly across the ground, with a sustained peak pressure. A vehicle descending almost straight down and going from supersonic through transonic to subsonic produces a toroidal region of shock which has a maximum only within a very small ring-shaped area on the ground. If the shockwave from a supersonic overflight is like a tsunami scraping its way across the ground, the shockwave is like a sudden and severe but brief rainfall.

Place a giant treadmill on a steep downward incline. Place a car on the treadmill, in neutral, and set the brakes. Turn on the treadmill (going uphill) and release the brakes. Can the treadmill go fast enough to keep the car from rolling downhill and off the treadmill?

Which is why it doesn't fit the analogy. A paddle steamer is more like a car. Both get their propulsion by pushing against the surface. An airplane gets its propulsion by pushing against the air. A closer analogy would be a sailboat. A sailboat can move against the current with a wind, because the air is pushing on it. Not necessarily. If a Boeing 747 goes to full throttle and then applies the brakes, it will not take off. A 747's TWR is around 0.3; the coefficient of sliding friction between rubber tires and asphalt is around 0.8. No, because fluid drag is proportional to the square of velocity. In practice, seaplanes typically take off pointing upstream, because the downstream flow of water creates a headwind. But imagine that the air at the water surface is stationary with respect to the bank. In order to accelerate to takeoff speed, your engine needs to overcome the fluid drag on your pontoons produced when you move through the water. Suppose that a plane typically takes off at 40 knots. If the water is moving downstream at 10 knots, then it will need to accelerate to 50 knots relative to the water surface, and the drag produced on the pontoons just before liftoff will actually be 156% of normal drag. If the water is moving downstream at 20 knots, the plane will need to accelerate to 60 knots relative to the water, and the drag will go up to 225%. If the water is moving at 40 knots, then drag will go up to 400%. Contrast this with the airplane on the treadmill. Suppose the airplane's takeoff speed is 40 knots and normal rolling drag on a flat runway inhibits the airplane's progress by a force of 100 Arbitrary-Force-Units (AFU). If we move the airplane from the runway to a treadmill and do not turn the treadmill on, then rolling drag will still be 100 AFU. If we turn the treadmill on to operate at a constant 10 knots, rolling drag...will still be 100 AFU. If the treadmill is turned on to 50 knots, rolling drag will still be 100 AFU. If the treadmill runs at 100 knots or 200 knots or 500 knots, rolling drag will still be 100 AFU. The speed of the conveyor belt does not change the forces acting on the plane. If you want the pontoon example to match, you'd need to say that the pontoons are coated in some kind of nearly-frictionless oil that has a set amount of drag and doesn't get more draggy matter how fast it goes. If that were so, then you couldn't drive a car on a treadmill. You can, but it won't get anywhere. True - for a car, the treadmill can prevent it from moving because the rotation of the wheels is a determinant of how fast the car can go. For a plane, however, the wheels have nothing to do with how it accelerates. Maybe this will help. Replace the airplane with a car. Place the car in neutral. Attach a winch to the front of the car, and secure the winch to a big rock way out in front of the treadmill. Turn on the winch and the treadmill at the same time. Does the car move? Most importantly: Can the conveyor belt keep the car from moving?

Tungsten halfnium carbide? Yes, by far.

Also sounds like a way to reduce the problem of overpopulation in general.

Typically, planes disengage their brakes before attempting to take off. With the brakes disengaged, nothing the treadmill does can keep the plane from moving.