Why do we still expect “successful failures” on rocket launches and not just scale up or scale down the same design on successful rocket ships and launch pads to make bigger or smaller ships with more stable structural material?
In: 1598
The physics of things change when you scale up. Years ago my father was involved with a massive smelter project to convert the source of heat from coal to natural gas. Lead-zinc. Traditionally smelting was done with coal mixed into the ore, which then burned in the molten metal furnace. The new idea was to force natural gas into the furnace with nozzles along the sides of the new furnace.
A German company did the research and built a 1/10 scale prototype smelter. Worked well and promised a 50% reduction in costs.
But scaling up was going to require, well, scale. In particular, in the full-scale plant, the pressure required to keep the nozzles that fed the natural gas into the molten mass would have to be scaled up. And my Dad, after considering it for a bit, did a back of the envelope calculation that showed that the higher pressure would fire the natural gas into the molten mass at quite a high speed.
High enough, in fact, that his calculation showed that the natural gas would pass right through the molten mass in less time that it would take to ignite.
It wasn’t going to work. He proved it wasn’t going to work.
Unfortunately they didn’t believe him, went ahead, built the $300 million full-size plant, and when they turned it on, yes, in fact, the natural gas went right through and didn’t ignite, the molten mass solidified solid, and they had a $300 million solid hunk of steel and slag on their hands.
So yes, scale can kill you in big projects.
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Material requirements do not scale the same rate as size.
If you double the size, you need 8 times the material capabilities.
Eventually we’re going to need materials as strong as titanium, but weigh as little as paper.
Material requirements do not scale the same rate as size.
If you double the size, you need 8 times the material capabilities.
Eventually we’re going to need materials as strong as titanium, but weigh as little as paper.
The mathematics of physics changes as you make things bigger. An easy example to demonstrate this is that we know that small things like insects and spiders can cling to the ceiling without much trouble – they make it look effortless. When was the last time you saw something larger than a mouse crawling on your ceiling?
Different scales have different problems. This is because different physical properties scale at different rates. If you double how long a cube is, you increase its surface area by 4 times and its volume by 8 times. The weight of the object scales with the volume while the strength of the object does not.
This is why the largest animal species (blue whales) are aquatic because the water helps support their large size.
The mathematics of physics changes as you make things bigger. An easy example to demonstrate this is that we know that small things like insects and spiders can cling to the ceiling without much trouble – they make it look effortless. When was the last time you saw something larger than a mouse crawling on your ceiling?
Different scales have different problems. This is because different physical properties scale at different rates. If you double how long a cube is, you increase its surface area by 4 times and its volume by 8 times. The weight of the object scales with the volume while the strength of the object does not.
This is why the largest animal species (blue whales) are aquatic because the water helps support their large size.
When I was small I could throw a Hot Wheels car from the back porch onto the grass and the car wouldn’t have any noticeable damage. It just fell from about 100x its own height and landed without a scratch. But if my dad’s car fell from 100x its height it would be totaled. Even if it fell from the back porch onto the grass, about equal to its own height, there would be a lot of damage if it landed on its top or side.
It’s pretty easy to break a popsicle stick in half but it’s much harder to break one of those halves in half. It’s nearly impossible to break one of the resulting pieces in half again without using tools.
u/armcie described the square/cube principle very well. Combine that idea with the popsicle stick theory and you can understand why bigger things can be so much more fragile than they first appear. Doubling in length means an eight fold increase in weight and volume and in the braces and brackets and supports needed to keep the thing together.
When I was small I could throw a Hot Wheels car from the back porch onto the grass and the car wouldn’t have any noticeable damage. It just fell from about 100x its own height and landed without a scratch. But if my dad’s car fell from 100x its height it would be totaled. Even if it fell from the back porch onto the grass, about equal to its own height, there would be a lot of damage if it landed on its top or side.
It’s pretty easy to break a popsicle stick in half but it’s much harder to break one of those halves in half. It’s nearly impossible to break one of the resulting pieces in half again without using tools.
u/armcie described the square/cube principle very well. Combine that idea with the popsicle stick theory and you can understand why bigger things can be so much more fragile than they first appear. Doubling in length means an eight fold increase in weight and volume and in the braces and brackets and supports needed to keep the thing together.
Because, contrary to what you have heard, rocket science is hard!
They did something never done before with the new super huge mega rocket. They now have new data for their models when they try again.
Because, contrary to what you have heard, rocket science is hard!
They did something never done before with the new super huge mega rocket. They now have new data for their models when they try again.
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