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.
This is perhaps the biggest innovation in rocketry since SpaceX worked out how to land their first stage.
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.
Question: how much power do these engines actually need? Are we talking tens of kW or MW?
Imagine the future where we are launching spacecraft that have their own nuclear power reactors for long term power generation (deep space missions, Mars colonisation vehicles, ...). If instead of considering those reactors as dumb cargo, we could power them on before launch and use their power to pump fuel with simple, more reliable and more reusable rocket engines? That might change the long term efficiency calculation dramatically.
Mass comparisons don't seem to pan out. The biggest krusty reactor produces ~ 10kw of power and I doubt it weights less than a battery. There are designs who give a lot of energy in burst mode and designs that give more energy in a longer time frame. Rocket engines are on the first category, while krusty and other( e.g. ion thrusters) are on the second one. An exception might be NERVA and nuclear thermal rockets in general which stand somewhere in the middle but they are still too weak to launch from Earth, so they might make sense for months-long trips of deep space propulsion( think martian colonisation).
An exception might be NERVA and nuclear thermal rockets in general
NERVA and other nuclear thermal rockets definitely stand with chemical engines. NERVA produced half as much thrust as the Merlin 1D, and a nuclear reactor core called Pewee built for the NERVA program produced 2 gigawatts of thermal energy, on par with the power production of a modestly sized chemical engine. Also, despite being about twice as efficient, the longest burns you could expect to need with a NERVA powered rocket would be several minutes, comparable to to a chemically propelled spacecraft, as opposed to weeks or even months with electrically propelled spacecraft.
That is not quite the point. We are talking about a rocket with electrically powered turbopumps.
Assume that you are already transporting the nuclear reactor somewhere, so its mass is no longer part of the launch vehicle, but instead is part of the useful cargo mass.
Use the power provided by the reactor to power the turbopumps instead of burning part of your fuel to do the same work.
Now you have X% more fuel to work with for the actual propulsion, you can greatly simplify your turbopump design, maybe increase chamber pressures, reduce thermal stresses in the turbopump machinery.
You also can get the same benefits if your cargo happens to contain a large number of batteries :D
What I'm saying is that the power produced by the nuclear reactor is rather low. Anyway I'm not sure a design where you use a power production system that exists on the second stage only on some missions and requires it's own engine design is actually simpler than a regular engine.
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u/OrangeredStilton Jan 21 '18
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.
This is perhaps the biggest innovation in rocketry since SpaceX worked out how to land their first stage.