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by DarmokJalad1701 705 days ago
Unlike a car battery though, these batteries provide a not-insignificant part of the energy that is generated by the engine. Each Rutherford engine generates around 37 mega-watts of power at sea-level (24900 N and 3.05 km/s exhaust velocity, Power = 1/2 * Thrust * v_e) and there are nine in the first stage. The first stage battery provides around one megawatt [1].

That's about 0.3% of all energy generated by the engines, which is significantly more than what a spark plug does in an ICE.

[1] https://theaeroblog.com/the-rutherford-rocket-engine-the-fir...

This is the closest we have to electric power directly powering the ascent of a rocket from Earth.

Something like a HyperCurie engine (which is also electric pump-fed), could probably lift off from a planetary body like the moon. When they used it in orbit, they actually had to wait for the batteries to charge up from solar panels between each engine burn.
1 comments
ben_w 705 days ago
> not-insignificant

> 0.3%

> the closest we have

I don't understand why you're trying to paint the battery as a significant contribution here.

Like a car battery, although it's neat that they consider it as part of the engineering, it's none of the actual thrust unless it explodes.

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DarmokJalad1701 705 days ago
It is about 1 megawatt (1341 HP) of the power pushing the rocket into the sky (directly translated into exhaust velocity and therefore thrust). That would be like a spark plug generating 1 HP in a 300 HP engine (Which would exhaust the typical car battery in about 1 second if it could even push that much power out).

It is all semantics anyway.

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DarmokJalad1701 704 days ago
Correction: It won't drain in a second. But my point is the same. We don't really have 1 HP spark plugs out there :)
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ben_w 704 days ago
Rough estimates I've seen say the starter motor is about that, though. (Not that I can tell real pages from GenAI ad content farms, I'm not a petrolhead).

I'd agree "it's all semantics", but yours are confusing me :P

(And for energy content, like for like is comparing the size of the fuel tank with the capacity of the battery, but cars aren't 90% fuel by weight).

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