Monday, August 24, 2015

Still like this idea, but I am missing something

Check over the math for the electron thruster idea

Speed of light equals 299,792,458  m / s

ISP equals effective velocity/  9.80665 m/s2  equals 30570323 ( rounded )

Thrust equals m dot times effective velocity

1 mole of electrons masses 1/1836 th one mole of protons

Atomic weight of hydrogen equals 1.00794, yielding 5.49e-4 grams sec, or 5.4899e-7 kg sec

If c is  299,792,458  m / s, and assuming m dot of   5.4899e-7 kg, then we obtain  164.58 kg m/ s squared

This calc looks correct, but the other calc for Isp may be wrong.  Double check rocket equation
want to be able to determine how much mass is needed and how long the thrust will take in order to accelerate a mass of 100k pounds to 2 km/sec

Okay, I've check rocket equation, and it says what it did before.  It will take about 300 grams to do the trick.  So, what accounts for the discrepancy?

Not using correct equations.  Just guessing at what it should be.  Moral to story?  Sometimes, you just don't know what you're doing, so it's best just to admit it.  Okay, I'm not a rocket scientist.


I've been fooling around with those equations linked to in the above paragraph, and plugging some numbers into the calculator.  In order to get the 30 million ISP number, the amount of electrons needed would only be
1/1000th of a mole of hydrogen.   The mass is 1/1836 of a gram divided by a thousand equals 5.45 e-7 grams electrons per second.  That should yield an ISP of close to 30 million, but that could be only a fantasy anyway.  Can't determine the true ISP cuz I ain't that smart.

Anyhow, with an ISP of a 30 million, then it should only use about 300 grams of electrons for the delta v of 2.1 km/sec.  It would have to obtain the electrons from hydrogen, which would require about 600 kg of hydrogen to go along for the ride.

The true number may be greater than a million, which is the number I've heard about for fusion engines.  They expel particles out at a fraction of the speed of light.  It is the velocity that makes all the difference.


I'm back to thinking that the real ISP is closer to 30 thousand than to 30 million.  This isn't a practical idea.


Maybe one more update, and I will leave this alone.  In order to make this idea work, you have to bring along the hydrogen for the source of electrons.  But that is why it won't work.  That is because it implies extra mass, and that extra mass makes it a problem.  You can get 30 million ISP if you use electrons exclusively, and leave the hydrogen home.  But to do that, you will have to confine the electrons and be able to retrieve them when you want them.  There isn't any way to do that for the length of time required.  If there was, they could make the Polywell Fusion device work.  The answer to the puzzle then, is that you cannot confine enough electrons to make this work.  It isn't feasible.

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