3 ms·

Super interesting! I wonder if there is an orbital limit to this technology. From what I remember, Rocket labs is mainly focusing on low orbital launches. As gr

Super interesting! I wonder if there is an orbital limit to this technology. From what I remember, Rocket labs is mainly focusing on low orbital launches. As great as batteries are, they are no where near the energy density of the propellants out there. Though the advancement of electrical pumps for rockets is super exciting!

Gibbon1 8y ago
I saw a paper that examined pressure fed, turbo pumps, and electric. Electric beats both pressure fed and turbo pumps at the size Rocket Lab is targeting. At large sizes turbines beat electric but the plumbing is much more complex and technically challenging. I'm suspicious that electrics are viable for first stages where performance advantage is less important. For first stages the cost is linear with ISP. Where it's exponential for second and third stages. (X^2 and X^3!!) For instance the Protons's first stage specific impulse is 285, Electron rockets specific impulse is 303. That's totally comparable.
- syntaxing 8y ago
  I would love to read that paper if you can find it! Does metal 3D printing mitigate any of these challenges? Or is the problem a packaging problem where there is a minimum size required for the mechanical parts?
  - Gibbon1 8y ago
    This is the paper I'm drawing most of my blather from. Apparently helpfully linked from the great wiki. https://www.aacademica.org/hernan.emilio.tacca/9.pdf https://www.aacademica.org/hernan.emilio.tacca/9.pdf I did some more looking, the linked study says that turbopumps scale better then electric as the burn time increases. Because burning fuel and oxidizer is more weight efficient than batteries. At short burn times that's offset by the increased weight of the turbopump. Along with my earlier comment, the Proton first stage only burns for 130 seconds. Which puts first stages in the short burn category where eletrics do well. *but never as good as turbo pumps. Which supports the idea that electric systems can compete for large first stages by being simple, cheap, and reliable. More whack is relanding first stage electric fed rockets. Ala SpaceX.
    - syntaxing 8y ago
      Super awesome! Thanks! I really wish I learned more about rockets during my graduate studies. Haven't really learned much about them besides supersonic nozzles and the math behind the staged combustion cycle during my ICE class. Any good websites or books you recommend to learn more about them?
  - Gibbon1 8y ago
    > Does metal 3D printing mitigate any of these challenges? I remember reading an interview with some NaSA engineers who were reverse engineering the F1 engines used for the Saturn V. He said notable was the amount of welded assemblies vs ones machined using 5 axis mills, and parts created via Powder Metallurgy on modern designs. http://atlaspressedmetals.com/index.php/pm-advantages/history-of-pm http://atlaspressedmetals.com/index.php/pm-advantages/histor...

Gibbon1 8y ago

I saw a paper that examined pressure fed, turbo pumps, and electric. Electric beats both pressure fed and turbo pumps at the size Rocket Lab is targeting. At large sizes turbines beat electric but the plumbing is much more complex and technically challenging. I'm suspicious that electrics are viable for first stages where performance advantage is less important. For first stages the cost is linear with ISP. Where it's exponential for second and third stages. (X^2 and X^3!!) For instance the Protons's first stage specific impulse is 285, Electron rockets specific impulse is 303. That's totally comparable.

syntaxing 8y ago
I would love to read that paper if you can find it! Does metal 3D printing mitigate any of these challenges? Or is the problem a packaging problem where there is a minimum size required for the mechanical parts?
- Gibbon1 8y ago
  This is the paper I'm drawing most of my blather from. Apparently helpfully linked from the great wiki. https://www.aacademica.org/hernan.emilio.tacca/9.pdf https://www.aacademica.org/hernan.emilio.tacca/9.pdf I did some more looking, the linked study says that turbopumps scale better then electric as the burn time increases. Because burning fuel and oxidizer is more weight efficient than batteries. At short burn times that's offset by the increased weight of the turbopump. Along with my earlier comment, the Proton first stage only burns for 130 seconds. Which puts first stages in the short burn category where eletrics do well. *but never as good as turbo pumps. Which supports the idea that electric systems can compete for large first stages by being simple, cheap, and reliable. More whack is relanding first stage electric fed rockets. Ala SpaceX.
  - syntaxing 8y ago
    Super awesome! Thanks! I really wish I learned more about rockets during my graduate studies. Haven't really learned much about them besides supersonic nozzles and the math behind the staged combustion cycle during my ICE class. Any good websites or books you recommend to learn more about them?
- Gibbon1 8y ago
  > Does metal 3D printing mitigate any of these challenges? I remember reading an interview with some NaSA engineers who were reverse engineering the F1 engines used for the Saturn V. He said notable was the amount of welded assemblies vs ones machined using 5 axis mills, and parts created via Powder Metallurgy on modern designs. http://atlaspressedmetals.com/index.php/pm-advantages/history-of-pm http://atlaspressedmetals.com/index.php/pm-advantages/histor...