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Comment by sabujp | Hacker News Reader

I don't understand how the 1.2mN/kW is better than the hall thruster that achieves 60mN/kW ? Isn't it better to achieve higher mN per kW than lower?

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Every other thruster works by pushing something small at very high speeds in the opposite direction of the direction you wish to move in. Hall thrusters are pushing small ions at near the speed of light or something, right?

This thruster pushes nothing. It just achieves thrust with only energy. No refueling ever, solar/nuclear energy into movement until you have no more energy.

This violates certain physical laws, but there it is being measured anyways.

Hall-effect thrusters throw ions at 15 to 30 Km/s, or 0.0001c.

There is one other thruster that doesn't need a tank of reaction mass: a photon rocket-- moving yourself around only using radiation pressure. Exhaust speed really is c, but generated thrust is tiny, since photons are pretty light. The resonant cavity thruster is more interesting than a photon rocket, since its thrust is much higher.

> Although this test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust-to-power figure of 1.2 mN/kW in context. The current state-of–the-art thrust to power for a Hall thruster is on the order of 60 mN/kW. This is an order of magnitude [more like two] higher than the test article evaluated during the course of this vacuum campaign; however, for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2 mN/kW performance parameter is over two orders of magnitude higher than other forms of “zero-propellant” propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the [0.0033-0.0067 mN/kW] range.

This is the first iteration of this device, I imagine that when the very first computing systems were being built, some humans were still on parity / better than the new systems.

The interesting part will be to see how this performs when we scale it up in size and stick it in a true space vacuum - it seems based on the experiments done that the amount of thrust scales linearly based on kW/h input, I imagine there are some significant gains to be made in terms of efficiency and cavity design which could well see significant increases in performance.

Then take in to account that the Hall Thruster requires a propellant - this only requires electricity, theoretically with a nuclear reactor on board, you could achieve constant acceleration, instead of our current methods of putting things in to deep space which consist mostly of "Blow up a ton of stuff behind it and then coast along for tens of millions of miles"

I'm not a trained physicist, by the way, so there could be fallacies or inaccuracies here, this is based on my understanding.

>I imagine that when the very first computing systems were being built, some humans were still on parity / better than the new systems.

I mean I guess it depends on how far back you want to go. The early electronic systems (Collosus, ENIAC, the crazy relay boards and bedsteads in the Newmanry at Bletchley) were all pretty much built expressly to solve practical and immediate problems (breaking ciphers, calculating parameters for nuclear weapons) that would take too long or contain too many errors if done by hand. Babbage got his freak on because of error rates in (IIRC) log tables. My Mesopotamian history is a little rusty, but it's easy to imagine a similar development story for the abacus. (In the sense of 'tool to surpass unaugmented human in speed and accuracy of computation' rather than 'hacking crypto and nuke yields'). But I dunno. Maybe.

Weren't collosus and ENIAC extremely error prone? I think ENIAC installed transistors as banks so they could easily replace them and this was required just to keep the machine somewhat functioning. I wonder how they compared to humans when factors like that are included?

This thing only needs energy to propel (if it actually works), while every other kind of viable thruster[1] needs some kind of "fuel" or propellant that is consumed, including hall thrusters, which limits the delta-v AKA change-of-speed you can achieve (more than energy availability).

[1] ie. nothing working with radiation pressure (solar sails, lasers etc)

reaction mass

Good to know. Wikipedia has a nice explanation of the concept:

> Working mass, also referred to as reaction mass, is a mass against which a system operates in order to produce acceleration. In the case of a rocket, for example, the reaction mass is the fuel shot backwards to provide propulsion. All acceleration requires an exchange of momentum, which can be thought of as the "unit of movement". Momentum is related to mass and velocity, as given by the formula P = mv, where P is the momentum, m the mass, and v the velocity. The velocity of a body is easily changeable, but in most cases the mass is not, which makes it important.

Calling this fringe research thruster research is misleading.

If their idea worked, it would be completely new physics.

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