5 ms·

Nasa did the calculation with with ancient computers and these guys are speculating and not using proper technology to achieve success. It makes no sense in 20

Nasa did the calculation with with ancient computers and these guys are speculating and not using proper technology to achieve success. It makes no sense in 2021. They should not be experimenting. Their simulations should be been solid before this stage. It is good way to burn cash.

avmich 6y ago
Simulations of certain things are still a problem today, even though less than it was in 1960-s. For example, trans-sonic aerodynamics is still hard. I'd imagine a good simulation of Raptor's inner flow when Starship does active maneuring can be a problem, especially if you also need to take into account material properties under dynamic loads.
- GizmoSwan 6y ago
  Lets assume that is the case. That is where they should spend their cash to produce something of real value that can be reused. Simulation close to perfection is the end game. Not sending something chunky into space.
  - avmich 6y ago
    No. It's way easier today to test than to solve that problem.
    - GizmoSwan 6y ago
      They will get a single rocket from that ideology and get stuck again in the loop later on with any big modification.
      - avmich 6y ago
        Falcon 9 now flies and lands with no crashes, especially comparing to expendable rockets. Of course a modification big enough will require changing control parameters, but that's a routine task for engineering. Some day we'll have good enough models for air flows in all necessary modes and good enough computers to run those models; we aren't there yet. Testing is still required.
  - NortySpock 6y ago
    https://www.youtube.com/watch?t=2580&v=vYA0f6R5KAI&feature=youtu.be https://www.youtube.com/watch?t=2580&v=vYA0f6R5KAI&feature=y... Yeah, they were doing high fidelity high performance computational fluid dynamics simulations and aerodynamic simulations by 2015. So I think they've done the sims, and now they're doing it in real life.
nwallin 6y ago
I can't say I agree. They're developing this thing in stages; they've developed and tested the engines, they've developed and are testing launching the thing, they've developed and are testing the re-entry flop. They have partially developed the whole "landing" thing and if you're going to be testing the belly flop, you might as well put whatever you have with regards to landing through its paces as well. By having a small team develop and test individual parts in stages, you avoid needing a giant team, and you avoid needing to have all of the schedules line up to be ready to go all at once. And it's the engineers who develop the rocket that is expensive, not the manufacturing. IMHO the benefits of having a completely flexible schedule greatly outweigh the expensive of assuming failure.
- GizmoSwan 6y ago
  You can't say a lot of things, so what! Giant team is not prerequisite for doing proper simulation before launching a gigantic rocket. I am being sincere. Nasa is in fact leading you on, to have some of their people wasting their time on this pseudo venture for optics. You seem to be using faith as your guiding light too rather than reason. It is not a prototype bicycle for experimental launch. It is all evident from down voting game that you are not open to criticism and gaming the boards.
  - nickik 6y ago
    You are so confident in your opinion and you are so incredibly wrong. Pretty much every NASA engineer that has worked with SpaceX has been incredibly impressed by their methods. Literally every single one of their competitors, including nation states have started to change their who launch strategy because they saw no other way to compete with Spacex (and they are still failing) all of them have expressed how impressed they are with SpaceX. You also seem to have a very trivial understanding of what SpaceX is doing and how it is different then what has been done before. SpaceX is not just developing a the biggest rocket ever (double Satrun V lift-off thrust), or just the most advanced rocket engine ever, or just a new method of landing (very different from Shuttle), or a new type of heat shield (again different from Shuttle or SpaceX Pica), or a method of mass producing rockets. They are fully vertically integrated and they build and work on all of these and many other things at the same time. Having one prototype explode is fine, because they are not just testing the prototype, they are testing the production of the rocket and optimizing the operations and everything mentioned above. The goal is to have the most advanced rocket of all time by a long margin, and be able to produce it cheaper then a current generation rocket, and operating it as cheaply as a airliner. You can not simulate or plan anything so complex and get it right the first time. They are constantly learning and improving every single aspect. The engine team uses every test fire for new inputs and adjust their simulation and improve the design, the engine manufacturing team is trying to improve the cost per engine and the production quality, the rocket manufacturing engineers are constantly improving the way the rocket is built and later prototypes have these improvements, the materials team invents new materials and is measuring their performance on the prototypes, the operations team is trying to reduce the amount of work it takes set up a launch and I could go on and on like that. Literally every prototype coming of the manufacturing line is a incrementally improved and usually cheaper then the one that came before it. The current SN8, SN9, SN10, SN11 are only small differences and with them they want to test the landing. They will be museum pieces once the landing is done, them blowing up generates real world data that can then improve their simulations. One of SpaceX core believe with this project is that the manufacturing system is 10-100x more difficult then the design of the rocket itself, and that their goals can only be achieved if these two things are co-designed. A test of a prototype is not just testing the design but also the manufacturing and quality control. When you try to design something that has never been done before and is incredibly complex, and you have the requirement that it must be incredibly cheap and incredibly reliable there is no way you can simply design it on a white sheet of paper, simulate it and then simply have a mass production system of that vehicle. That is simply impossible. And your claim that this is just 'cash burn' for no reason is equally wrong. SpaceX approach to engineering has routinely beat everybody in every single competition and usually by quite a lot. Nobody knows better how to develop something with a small budget compared to SpaceX. The whole Starship program so far, including new revolutionary engines, has cost less half of the much smaller Ariane 6, or less then a single year of the SLS program. SpaceX is simply universally acknowledged as the most advanced rocket company in the world, and its not close. They are doing it this way for a reason, and they are a lot smarter then you.
MauranKilom 6y ago
Honest question: Have you worked with fluid simulations before? We cannot fully predict turbulent flow from first principles. I mean, we can, but when constrained by real-world computing hardware, we can only do it in very tiny domains. Turbulence requires way too many orders of magnitude in spatial resolution to fully resolve it in "real world" problems. Therefore, any practical simulation for engineering purposes involves some way of modelling (read: approximating) turbulent behavior at sub-grid scales. There are tons of these models suitable for all kinds of different applications, domains, flows, etc. - but they are all just models. Part of the engineering effort is finding the right model for the task on hand, and for that you need experimental data. This of course doesn't apply only to fluid dynamics (but also e.g. the overall dynamic behavior of the entire assembled rocket and rocket engine, which could interact with the fluid flows in a nontrivial manner), but the point is that simulations aren't automatically accurate because you do more of them or throw more money or compute at them (that is also a good way to burn cash) - they are still approximations of unknown accuracy until you actually compare them with data from reality to confirm whatever modeling assumptions you made. The "least cash expenditure" approach will thus involve both simulations and experiments, and you will eventually reach the point where putting money into making rockets (potentially) crash will give you better lessons than running yet another simulation with (unbeknownst to you) subtly flawed assumptions.
emilecantin 6y ago
SpaceX does do simulations, and tons of it. SN8 and 9 wouldn't have performed that well during the descent stage without amazing guidance software, which could only have been developed through extensive simulations. Simulations are always going to be "assume a spherical cow in a vacuum" to a degree, as the real world is unbelievably complex, and you have to use models at some point. These models _can_ be wrong, and the only way to test them is through experimentation.

avmich 6y ago

Simulations of certain things are still a problem today, even though less than it was in 1960-s. For example, trans-sonic aerodynamics is still hard. I'd imagine a good simulation of Raptor's inner flow when Starship does active maneuring can be a problem, especially if you also need to take into account material properties under dynamic loads.

GizmoSwan 6y ago
Lets assume that is the case. That is where they should spend their cash to produce something of real value that can be reused. Simulation close to perfection is the end game. Not sending something chunky into space.
- avmich 6y ago
  No. It's way easier today to test than to solve that problem.
  - GizmoSwan 6y ago
    They will get a single rocket from that ideology and get stuck again in the loop later on with any big modification.
    - avmich 6y ago
      Falcon 9 now flies and lands with no crashes, especially comparing to expendable rockets. Of course a modification big enough will require changing control parameters, but that's a routine task for engineering. Some day we'll have good enough models for air flows in all necessary modes and good enough computers to run those models; we aren't there yet. Testing is still required.
- NortySpock 6y ago
  https://www.youtube.com/watch?t=2580&v=vYA0f6R5KAI&feature=youtu.be https://www.youtube.com/watch?t=2580&v=vYA0f6R5KAI&feature=y... Yeah, they were doing high fidelity high performance computational fluid dynamics simulations and aerodynamic simulations by 2015. So I think they've done the sims, and now they're doing it in real life.

nwallin 6y ago

I can't say I agree. They're developing this thing in stages; they've developed and tested the engines, they've developed and are testing launching the thing, they've developed and are testing the re-entry flop. They have partially developed the whole "landing" thing and if you're going to be testing the belly flop, you might as well put whatever you have with regards to landing through its paces as well. By having a small team develop and test individual parts in stages, you avoid needing a giant team, and you avoid needing to have all of the schedules line up to be ready to go all at once. And it's the engineers who develop the rocket that is expensive, not the manufacturing. IMHO the benefits of having a completely flexible schedule greatly outweigh the expensive of assuming failure.

GizmoSwan 6y ago
You can't say a lot of things, so what! Giant team is not prerequisite for doing proper simulation before launching a gigantic rocket. I am being sincere. Nasa is in fact leading you on, to have some of their people wasting their time on this pseudo venture for optics. You seem to be using faith as your guiding light too rather than reason. It is not a prototype bicycle for experimental launch. It is all evident from down voting game that you are not open to criticism and gaming the boards.
- nickik 6y ago
  You are so confident in your opinion and you are so incredibly wrong. Pretty much every NASA engineer that has worked with SpaceX has been incredibly impressed by their methods. Literally every single one of their competitors, including nation states have started to change their who launch strategy because they saw no other way to compete with Spacex (and they are still failing) all of them have expressed how impressed they are with SpaceX. You also seem to have a very trivial understanding of what SpaceX is doing and how it is different then what has been done before. SpaceX is not just developing a the biggest rocket ever (double Satrun V lift-off thrust), or just the most advanced rocket engine ever, or just a new method of landing (very different from Shuttle), or a new type of heat shield (again different from Shuttle or SpaceX Pica), or a method of mass producing rockets. They are fully vertically integrated and they build and work on all of these and many other things at the same time. Having one prototype explode is fine, because they are not just testing the prototype, they are testing the production of the rocket and optimizing the operations and everything mentioned above. The goal is to have the most advanced rocket of all time by a long margin, and be able to produce it cheaper then a current generation rocket, and operating it as cheaply as a airliner. You can not simulate or plan anything so complex and get it right the first time. They are constantly learning and improving every single aspect. The engine team uses every test fire for new inputs and adjust their simulation and improve the design, the engine manufacturing team is trying to improve the cost per engine and the production quality, the rocket manufacturing engineers are constantly improving the way the rocket is built and later prototypes have these improvements, the materials team invents new materials and is measuring their performance on the prototypes, the operations team is trying to reduce the amount of work it takes set up a launch and I could go on and on like that. Literally every prototype coming of the manufacturing line is a incrementally improved and usually cheaper then the one that came before it. The current SN8, SN9, SN10, SN11 are only small differences and with them they want to test the landing. They will be museum pieces once the landing is done, them blowing up generates real world data that can then improve their simulations. One of SpaceX core believe with this project is that the manufacturing system is 10-100x more difficult then the design of the rocket itself, and that their goals can only be achieved if these two things are co-designed. A test of a prototype is not just testing the design but also the manufacturing and quality control. When you try to design something that has never been done before and is incredibly complex, and you have the requirement that it must be incredibly cheap and incredibly reliable there is no way you can simply design it on a white sheet of paper, simulate it and then simply have a mass production system of that vehicle. That is simply impossible. And your claim that this is just 'cash burn' for no reason is equally wrong. SpaceX approach to engineering has routinely beat everybody in every single competition and usually by quite a lot. Nobody knows better how to develop something with a small budget compared to SpaceX. The whole Starship program so far, including new revolutionary engines, has cost less half of the much smaller Ariane 6, or less then a single year of the SLS program. SpaceX is simply universally acknowledged as the most advanced rocket company in the world, and its not close. They are doing it this way for a reason, and they are a lot smarter then you.

MauranKilom 6y ago

Honest question: Have you worked with fluid simulations before? We cannot fully predict turbulent flow from first principles. I mean, we can, but when constrained by real-world computing hardware, we can only do it in very tiny domains. Turbulence requires way too many orders of magnitude in spatial resolution to fully resolve it in "real world" problems. Therefore, any practical simulation for engineering purposes involves some way of modelling (read: approximating) turbulent behavior at sub-grid scales. There are tons of these models suitable for all kinds of different applications, domains, flows, etc. - but they are all just models. Part of the engineering effort is finding the right model for the task on hand, and for that you need experimental data. This of course doesn't apply only to fluid dynamics (but also e.g. the overall dynamic behavior of the entire assembled rocket and rocket engine, which could interact with the fluid flows in a nontrivial manner), but the point is that simulations aren't automatically accurate because you do more of them or throw more money or compute at them (that is also a good way to burn cash) - they are still approximations of unknown accuracy until you actually compare them with data from reality to confirm whatever modeling assumptions you made. The "least cash expenditure" approach will thus involve both simulations and experiments, and you will eventually reach the point where putting money into making rockets (potentially) crash will give you better lessons than running yet another simulation with (unbeknownst to you) subtly flawed assumptions.

emilecantin 6y ago

SpaceX does do simulations, and tons of it. SN8 and 9 wouldn't have performed that well during the descent stage without amazing guidance software, which could only have been developed through extensive simulations. Simulations are always going to be "assume a spherical cow in a vacuum" to a degree, as the real world is unbelievably complex, and you have to use models at some point. These models _can_ be wrong, and the only way to test them is through experimentation.