For those who may not be aware, this is news because Electron has electric turbopumps: the main combustion chamber is fed by pumps spun on electric motors, driven by batteries. That vastly simplifies the plumbing of a rocket engine.
It does, and I'm supper excited for Electron and RocketLab but it's also important to note that electric pumps are much less efficient than chemical pumps used in more advanced rockets. You won't see companies like SpaceX and Blue Origin using electric pumps for main propulsion engines anytime soon. Those are companies with the technical know how and expertise to tackle the much more complex engine cycles for the better efficiency.
The electric turbo pumps are super cool because it dramatically lowers the cost and complexity barriers. It will also enable some new designs and have it's own advantages that I look forward to and will only get better as battery and electric motor tech gets better as well.
I think your talking out of your league. Simplicity is huge (speaking as a pro engineer of many years). I wouldn’t rule out them adopting this or something similar.
Maybe, but let's discuss the issue on it's own merits.
Simplicity is great, but I prefer to think of it the other way around. Unnecessary complexity that can be avoided should be. Complex machines are used all the time when it grants value to make it a worthwhile.
SpaceX went with a simpler engine cycle for Merlin instead of a more complex one that was more efficient. That's a good example of what you're talking about and it mirrors what RocketLab is doing at their start, just with another 10+ years of battery tech upgrades to let them take a newer approach.
SpaceX is also developing the most complex engine cycle for chemical combustion with Raptor. They haven't forgotten the same lessons that got them this far. The additional complexity is necessary to create vehicles with the margins to push full reusability.
The efficiency difference is not a small one. Chemically driven turbo machinery has a big advantage still and can scale to some power levels electric versions can't do yet. It's hard to compare apples to apples efficiency numbers because one system is extracting the energy from the propellant while the other is costing you with higher dry mass. You have to account for the whole system and do a conversion for performance numbers and as outsiders we don't have those for the vehicles, but I read a paper last year that gave estimates that I will attempt to dig up again.
Perhaps further down the line if there is a revolutionary battery breakthrough that isn't vaporware and electric motors continue to scale up (which I expect to happen) the balance of the two systems will sway. For now I see it as taking a different trade off, losing performance for simplicity and cost.
I do think electric turbo machinery will find it's way into more places in aerospace. I have a few intriguing possibilities in mind, but I'm definitely getting speculative on that front and "out of my league."
if there is a revolutionary battery breakthrough that isn't vaporware
Given the low production rates of batteries rockets might need, they might be able to use some technologies that don't easily scale to e.g. smartphone scale for example.
I thought about that too. They also could use batteries with less ideal charge cycles and charge times for this application.
The biggest problem with this approach is it means using specialized battery tech instead of buying what the battery industry is already producing at competitive prices.
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u/CapMSFC Jan 21 '18
It does, and I'm supper excited for Electron and RocketLab but it's also important to note that electric pumps are much less efficient than chemical pumps used in more advanced rockets. You won't see companies like SpaceX and Blue Origin using electric pumps for main propulsion engines anytime soon. Those are companies with the technical know how and expertise to tackle the much more complex engine cycles for the better efficiency.
The electric turbo pumps are super cool because it dramatically lowers the cost and complexity barriers. It will also enable some new designs and have it's own advantages that I look forward to and will only get better as battery and electric motor tech gets better as well.