EM Drive

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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rcain
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Re: EM Drive

Postby rcain » Sat Aug 02, 2014 1:06 am

Guys,

i just caught the story on EM/VE drives on:

http://nasawatch.com/archives/2014/08/j ... A+Watch%29

http://sploid.gizmodo.com/nasa-reveals- ... socialflow

via twitter.

what's the reckoning here? how seriously should we treat the claim?

djolds1
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Re: EM Drive

Postby djolds1 » Sat Aug 02, 2014 2:32 am

Vae Victis

birchoff
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Re: EM Drive

Postby birchoff » Sat Aug 02, 2014 3:59 am


Betruger
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Re: EM Drive

Postby Betruger » Sat Aug 02, 2014 4:49 am

Birchoff your links are shortened by forum autocorrect. You have to put them in [url] tags.

edit-

- 13 feb 2013
- 2 nov 2012
- 2 nov 2012

birchoff
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Re: EM Drive

Postby birchoff » Sat Aug 02, 2014 5:33 am


RERT
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Re: EM Drive

Postby RERT » Sat Aug 02, 2014 1:37 pm

Although there is massive cause for scepticism on these results, it's amusing to do some arithmetic on what it might mean if true.

5mN per kW combined with 2kW/kg, gives an acceleration of 10^-2 ms^-2. That's about 10^-3 light years per year per year.

On a simple newtonian calculation, accelerating for 63 years gets you 0.5*a*t^2, or 2 light years. You arrive at Alpha Centauri,
at rest, after 126 years. Too long for humans, but interesting for a 'survey' probe. If the thrust efficiency rose to 50mN/kW, it
gets there in 40 years.A barely feasible human mission of 13 years requires 500mN/kW or a higher specific power.

Can the fuel last that long? It is't immediately infeasible, unless the conversion efficiency from mass-energy deficit to electricity
is down in the 1% range. Interested to hear what the forum members think about this.

Interestingly, the LM skunkworks '100MW on the back of a truck' must be in the ball park of 1MW/T or 1kW/Kg, so roughly what's required.

Interested to hear if anybody else here has done similar sums.

birchoff
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Re: EM Drive

Postby birchoff » Sat Aug 02, 2014 2:20 pm


DeltaV
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Re: EM Drive

Postby DeltaV » Sat Aug 02, 2014 4:16 pm


Image

Image

GIThruster
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Re: EM Drive

Postby GIThruster » Sat Aug 02, 2014 5:28 pm

"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Carl White
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Re: EM Drive

Postby Carl White » Sat Aug 02, 2014 5:33 pm


birchoff
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Re: EM Drive

Postby birchoff » Sun Aug 03, 2014 1:05 am


D Tibbets
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Re: EM Drive

Postby D Tibbets » Sun Aug 03, 2014 5:58 am

A perhaps more detailed experimental description. One red flag is that the test article and a supposed null control both apparently produce thrust... which suggests either the test setup is flawed or the physics is confounding...

http://ntrs.nasa.gov/search.jsp?R=20140006052

Dan Tibbets
To error is human... and I'm very human.

tokamac
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Re: EM Drive

Postby tokamac » Sun Aug 03, 2014 10:23 am

Last edited by tokamac on Fri Aug 15, 2014 7:36 pm, edited 1 time in total.

RERT
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Re: EM Drive

Postby RERT » Sun Aug 03, 2014 2:57 pm

Apropos various remarks:

2 kW/kg was rather arbirary and used to calculate N/kg, aka acceleration. So higher thrust per watt reduces the specific power requirement. Higher thrust/Watt may be entirely sensible, per others comments. Also, do you agree the proposed skunkworks generator is about 1kw/kg? I cross-checked my memory just now, and the plan is definitely 100MW on the back of a truck. They are not being entirely serious if that is planned to be more than 100T. So 1MWe/T or 1kWe/kg looks reasonably sane for a fusion power plant. If it weighed 100T, the payload and fuel would be immaterial. I don't know the specific power of space based fission plants, so have no reason to contradict what you said about their limitations.

DeltaV, with the 'Saucer' photo: I must confess that part of my reaction to my calculation was 'So where are the aliens?' If they are not here, something must be wrong...

Lastly, on the theory part: if the proper acceleration (in the device's rest frame) is not constant, then there goes another law of physics, because the setup would not be relativistically invariant. Still, you lose conservation of momentum, and who knows what comes next.

birchoff
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Re: EM Drive

Postby birchoff » Sun Aug 03, 2014 4:02 pm



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