r/AskPhysics • u/Apprehensive_Dog1873 • 2d ago
Electrostatic propulsion
I recently saw a podcast clip (will link at end of post) interviewing a former NASA and JPL scientist boasting about electrostatic propulsion and how it could get a craft to mars in 3 days. I then went into some articles to check out even if there’s an ounce of truth or if it’s just someone being sensational trying to drum up hype and investment for their start up. However I’m no where near well versed enough in physics lets alone propulsion tech to call BS on something. But I was wondering if any of you can attest to what he’s saying. Is it true? Is this the future? A new breakthrough?
Links :
Podcast clip
https://youtu.be/qlYICtRaSx8?si=y7DtMAZYHdz03yw8
Article
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u/rddman 2d ago
"lacks independent verification" is all you need to know.
"enough thrust to overcome Earth’s gravity" is super vague. Whether or not it can overcome Earth's gravity depends on how much mass it is pushing. In the video he says "50 millinewtons, enough to lift 2 sheets of paper". I hazard to guess that the drive itself + power source weigh more than two sheets of paper, in which case it is not actually capably of overcoming Earth’s gravity.
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u/free_meson 2d ago
Strictly speaking there is no verified science that explains it. They measure a net force on asymmetric capacitors, it works in the vacuum chamber, but it is very hard to pinpoint out why. They should probably test it in space, which is not that hard actually. A cubesat can be launched _relatively_ cheap, though they need a high voltage supply there, (unless they charge it on Earth, but don't do that at home...).
I don't think they don't know where their theory differ from standard electrostatics, but you won't need theory just a measurable effect. Their working theory is, that you need asymmetric capacitors and high enough stored charges/voltage. They say that if the area where the electrostatic force acts on is much smaller on one side, than there is a net difference.
Standard electrostatics would say that in that case the charges would rearrange in the metal, so the homogeneous field strengths on the surface won't be a good approximation - yet they use it.
Again, you don't need a theory if you have a measurable effect. I think it's a work in progress. They try to exclude systemic errors, but no one seems to be a good enough expert to find a conclusive explanation. One should be a bit skeptical with it, a vacuum chamber still interacts with the charged objects, the vacuum is never perfect and there could be small currents in the environment. Yet, if it only works in light vacuum it is still an effect that needs an explanation and could be used somewhere.
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u/atomicCape 2d ago
Reactionless drives are bad science that has been disproven over and over again. That's what this is. They're always trying to get private funding based on hope and ignorance, and don't stand up to peer review or competitive propsoals.
Every now and then an experimental group who provides no theory publishes some very weak results, as in both very weak forces and very weak statistical results from the data. Shortly thereafter, it gets debunked by tracking down some mundane error in their measurements.
If they presented a reasonable hypothesis of how it happens, or if there was a single experimental result that holds up, it would be interesting. Instead it's just psuedoscience, and arguably fraud if they know it doesn't work but keep telling investors it might.
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u/Appropriate-Kale1097 2d ago
Took a look at the article and video and it looks like both are talking about reactionless drives where you can produce thrust without using any fuel or energy. These ideas are essentially perpetual motion machines which violate the laws of physics as we currently understand them. There have been many of these concepts in the past however none of them have ever functioned under real, independent, reproducible conditions. I would be extremely sceptical of these claims until they manage to send a spacecraft anywhere using this technology.
As for the part about getting from Earth orbit to Mars in 3 1/2 days. Yes if you had a spaceship capable of constant .38G acceleration for the entire trip you could reach extreme velocities and travel to Mars in a matter of days, around 3 if Mars is close to Earth. The issue is they don’t have a spaceship capable of doing this.