CompelTechnic

Scaling for static friction between rubber and asphalt does not follow the friction equation you are taught in high school physics class. Generally, for a given weight of vehicle, a larger tire surface area is able to produce more maximum braking friction. In other terms, minimizing the surface pressure and maximizing the surface area at the contact patch increases maximum braking friction.

-More expensive energy directly leads to less energy-intensive activity, and a lot of this energy-intensive activity is the sort of activity that helps human flourishing.

-A tendency to regulate activity such that the most energy-optimized activity is the only allowable/ affordable activity.

-Regulating away the ability to do things, especially things that have questionable externalities and the regulators don't see the immediate value of. Is it really a good thing that the Netherlands is destroying the livelihoods of farmers to protect natural areas from Nitrogen emissions? Who quantified the harm associated with the nitrogen emissions? How does this harm food security in the Netherlands? How does this fare in relation to the fact that energy independence and food independence go hand-in-hand, at a time when there is a global fertilizer shortage and a European energy shortage? Seems short-sighted to me.

do you have a source for this? Wikipedia data in the Launch vehicle estimated payload cost per kg table disagrees with you. By a factor of ~20.

https://en.wikipedia.org/wiki/Space_launch_market_competitio...

The pareto frontier of possible artworks approaches higher quality with increased labor input. This doesn't mean the Labor Theory of Value isn't totally bonkers.

The idea that D&D has hoovered up so much of the world as to deny people of their own creative expression is absurd and I couldn't get past the first paragraph without thinking the author is off his rocker.

(going off of memory here and a bit of speculation, hope I didn't misremember it)

It seems to me that there are two possible root causes (assuming the vehicle is constant, i.e. not from women driving smaller cars):

1. The crash test and vehicle designs are optimized around average male physiology 2. average female physiology would be more at-risk of injury and death regardless of crash test design/vehicle design

I'd like to know more about how much each of these factors contribute. The article does not make this clear.

Seems like we're doing fine.

Stick a load cell on a linear slide, measure accordingly.

I really like this snippet. Captures an idea I hadn't ever been able to put into words before.

If the price sensitivity tradeoff of customers ultimately dictates that these standing seats do not gain adoption, I would not be surprised.

History has shown that customers want cheap flights more than they want comfort, but complaining all the while.

1. Focus on producing novel content to keep the game interesting, mixing things up enough over weeks/months, but without killing the core mechanics.

2. Hire lots of new employees, all while knowing that the popularity bubble may burst and they may need to be laid off in the near future.

3. Give bonuses to my employees, who are working their tails off, to prevent resentment. Especially in the over-worked video game industry.

4. Acknowledge that this lucky streak is unrepeatable, and that if the game falls out of popularity, there is likely no one to blame. But when it happens, the demoralization will hit hard and the layoffs are inevitable.

5. All this, while the company reaps huge profits.

The graph cites the report linked above. Middle income is defined as household income between 75% and 200% of median on page 19 of the report.

if you hang a tensile load of 1000 Newtons from a 1mm x 1mm rod, the rod is under 1 GPa of stress.

1. Make the edge of the disc rub against a low friction, spring-loaded compressing element (similar to commutator brushes, but designed to really transfer a large load). This is probably infeasible because friction would eat more energy than your cycle would move.

2. Have electric actuators that are mounted on the disk itself. These would have to be powered by slip rings via the shaft. These would be active for half of the cycle and inactive for the other half. Not sure whether they should be radial, azimuthal, or axial mounted. Seems kludgey.

3. Have the disk pass through a magnetic field, exploiting the magnetic effects the article mentions. I have no idea of any of the implementation details of this, but it sounds like a better idea than 1 or 2...

1. My understanding: this material relies on mechanical work (force x distance = work energy) to add energy to the material by compressing (or tensioning, or "magnetically stressing", which I don't understand) it. Some fraction of this energy is converted phase transitions which absorb heat, and some fraction is retained as spring potential energy. If the material is then heated by ambient air, and then the material is allowed to expand, it will now be at a temperature above the ambient temperature at the start of the cycle. In this way it is similar to a standard refrigeration cycle- just without pipes.

2. The cycle described in point 1 is not particularly unique to this material. You could do a similar process with any mechanical spring (google "rubber band heat engine"), and achieve similar results. This material is likely uniquely well suited to this application because it has usefully large amounts of heat associated with phase transitions at temperatures that correspond well with the temperatures used in a refrigeration cycle.

3. You want the material to dump heat to a hot reservoir while hot and suck heat from a cold reservoir while cold. Standard, fluid based refrigeration cycles do this by pumping the refrigerant to different locations (the condensor and evaporator). (I am assuming) This process would have to open and close dampers to get the hot reservoir air and the cold reservoir air to flow across the material; otherwise you have to move the material between the two locations. Both of these sound expensive/tricky to me.

4. A large challenge here is creating an electrical actuator that can compress the material. It would the following design objectives/constraints:

4a. The material should be shaped into long, narrow rods, or another shape with a large surface area, to be ideal for maximum heat transfer with the air of the hot and cold reservoirs.

4b. The actuator must recover the work energy provided when the material is allowed to expand.

4c. The actuator will have a very short stroke (solids do not compress very far), and large force.

4d. The actuator must last many thousands or millions of cycles without wearing out.

5. This style of refrigeration does not have any higher theoretical or actual efficiency than a fluids-based cycle. However, refrigerants have historically been environmentally damaging when released to the atmosphere. R-12 kills ozone, and is obselete/ outlawed. R-134a is currently in a lot of new systems, there are also newer refrigerants being put into new cars. The only thing particularly bad about R-134a is that 1 kg of R-134a equals several thousand kg's of CO2 in terms of global warming effect.