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
Largely because planning out very large rockets without testing smaller, scaled down ones, would be a waste of both planning and building time.
Let’s give an example: You are planning to make cupcakes for 1,000 people. In your mind, you plan out the flavors and recipes, plan out how you’re going to get 1,000 cupake tins, you plan how to bake the cupcakes. You plan out how you are going to stack the cupcakes into a box and deliver them. You plan everything out before making your first cupcake.
Then, you make 1,000 cupcakes and you taste them: They taste terrible. You now scrap 1,000 cupcakes and change your recipe.
Clearly, this is an enormous waste of time (baking and planning) and a tremendous waste of resources.
Instead, a better plan would be to make a small batch of cupcakes, then taste them. Do they taste good? Great. Now, with that small batch… see if the cupcakes will stack, even with small numbers. Are they too mushy or sticky to stack, even in small numbers? Ok, adjust your stacking plan.
Make small batches and test to see if they work in small numbers. Then, scale up and address the big scale problems. If it doesn’t work in small batches, it won’t work in large batches. Save time and resources by starting small.
Largely because planning out very large rockets without testing smaller, scaled down ones, would be a waste of both planning and building time.
Let’s give an example: You are planning to make cupcakes for 1,000 people. In your mind, you plan out the flavors and recipes, plan out how you’re going to get 1,000 cupake tins, you plan how to bake the cupcakes. You plan out how you are going to stack the cupcakes into a box and deliver them. You plan everything out before making your first cupcake.
Then, you make 1,000 cupcakes and you taste them: They taste terrible. You now scrap 1,000 cupcakes and change your recipe.
Clearly, this is an enormous waste of time (baking and planning) and a tremendous waste of resources.
Instead, a better plan would be to make a small batch of cupcakes, then taste them. Do they taste good? Great. Now, with that small batch… see if the cupcakes will stack, even with small numbers. Are they too mushy or sticky to stack, even in small numbers? Ok, adjust your stacking plan.
Make small batches and test to see if they work in small numbers. Then, scale up and address the big scale problems. If it doesn’t work in small batches, it won’t work in large batches. Save time and resources by starting small.
I haven’t seen anyone mention the rocket equation. Each additional gram of rocket requires additional fuel/propellant, which itself requires additional fuel/propellant, et cetera. A bigger/more robust launch vehicle != a better launch vehicle.
I haven’t seen anyone mention the rocket equation. Each additional gram of rocket requires additional fuel/propellant, which itself requires additional fuel/propellant, et cetera. A bigger/more robust launch vehicle != a better launch vehicle.
I’m seeing some overly complicated answers… Very simply, it’s really hard to scale up or down forces. I hate Elon more than the next person but it’s better that it blow up and it be empty than blow up and be full of people because the scaled down model didn’t account for atmospheric pressure
I’m seeing some overly complicated answers… Very simply, it’s really hard to scale up or down forces. I hate Elon more than the next person but it’s better that it blow up and it be empty than blow up and be full of people because the scaled down model didn’t account for atmospheric pressure
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Aaaaand. There’s the story of the Ariane 501 rocket. In that example they did exactly what you suggest here they should have done: they took the Ariane 401, which had flown successfully hundreds of times, and just scaled everything up.
In particular they didn’t look too hard at the guidance system.
So what happened when they launched it was the new rocket took off nicely, and flew 20% faster than the old one.
Unfortunately this meant that the thing was travelling at a speed whose number was beyond the space available in the computer slot allocated to keep track of it. It was going faster than the maximum on the speedometer, in effect (technically, the computer register was 8 bits, and the speed number exceed the maximum for an 8 bit number).
So the navigation system couldn’t read how fast the thing was going, and triggered a billion dollar self-destruct.
Because they thought scaling it up would be fine.
Aaaaand. There’s the story of the Ariane 501 rocket. In that example they did exactly what you suggest here they should have done: they took the Ariane 401, which had flown successfully hundreds of times, and just scaled everything up.
In particular they didn’t look too hard at the guidance system.
So what happened when they launched it was the new rocket took off nicely, and flew 20% faster than the old one.
Unfortunately this meant that the thing was travelling at a speed whose number was beyond the space available in the computer slot allocated to keep track of it. It was going faster than the maximum on the speedometer, in effect (technically, the computer register was 8 bits, and the speed number exceed the maximum for an 8 bit number).
So the navigation system couldn’t read how fast the thing was going, and triggered a billion dollar self-destruct.
Because they thought scaling it up would be fine.
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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