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Quince
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I actually got a reply from the author! Though I forgot to ask for permission to post his response, I'm sure he won't mind (but
please do not email him quoting the message below). Here it is; the paper is too large to attach, so I can email it to people that request
it (contact me by U2U):
| Quote: | Dear *****,
here is the paper, as it was presented at the IAF in Fukuoka just a few days ago.
WRT fusion propulsion I clearly believe that this will become the propulsion system of choice in a few decades, when humanity will finally really go
out to explore space.
Although there a lot of objections, I believe that most of those will disappear when ITER has proven that fusion is a feasible energy technology. On
the other hand fusion propulsion is anyway much easier to do, because of the lower Q-value and all the lessened requirements on plasma stability.
Personally I believe that the first fusion nuclear thermal propulsion system will not be of the inertial but rather of the magnetic confinement type.
However it will not look like the ITER's TOKAMAK configuration but will more resemble a pinch, as the lower Q reduces the plasma stability
constraints.
The Gas Dynamic Mirror and/or the Dense Plasma concepts are likely systems we might see in the future.
Whether the thrust will be high enough to outweigh the weight is indoubt, but with an adding of additional hydrogen/oxygen this might well be the
case.
As concerns our invention described in the paper, the thrust of this very early prototype is still in the mN-region, but then on the other hand we are
not aiming for a missile propulsion system, but rather for an attitude control / NSSK and kick-booster system.
cheers
Norbert
Am 18.10.2005 20:27 schrieben Sie:
> Regarding http://www3.inspi.ufl.edu/space/program/abstracts/1146.pdf
> I would be interested in obtaining the full text if possible.
>
> In addition, I am interested in getting your comment on whether you think that fusion-based propulsion is practical even in the long term. In an
online discussion
> (http://www.sciencemadness.org/talk/viewthread.php?tid=4658) a member
> member has stated that they are not due to fusion being an 'ineherently low density effect', and are thus a mere academic exercise. So
I'm writing to you to ask for the opinion of an expert in the field.
>
> Thank you.
---------- AD ASTRA PER ASPERA ----------
Dipl.-Ing. Norbert "Norbi et Orbi" FRISCHAUF
Email: Norbert.Frischauf@cern.ch
----------------------------------------- |
Anyone care to explain what is Q-value, and what is this pinch he mentions? Also, what did he mean by inertial type? The only intertial fusion
I've heard of is the Fransworth fusor, which is so inefficient it's only useful as a laboratory neutron source. Besides this and the
magnetic confinement fusion, I only know of two other types -- the burst type using pellets bombarded by lasers/X-rays/antimatter, and the
pyroelectric crystal driven fusion (http://rodan.physics.ucla.edu/pyrofusion/), where some billion volt electric field is created by concentrating the field on the crystal at a very
fine point, and the field acts as an accelerant on the deuterium ions (so I guess it's a type of electrostatic confinement).
[Edited on 24-10-2005 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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IrC
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The pinch effect occurs when magnetic pressure exceeds the particle pressure of the plasma. The magnetic field may diffuse the plasma, or the plasma
boundary can increase the particle pressure. Imagine a gas which is highly ionized, subjected to such a strong magnetic field that the plasma is
actually squeezed out of a region (think in terms of the appearance of a link of sausages). This effect makes for some of the properties found in a
bolt of lightning. Plasma current (as in the current in a bolt of ligthning) creates a magnetic field that exerts a radially inward force acting
against the plasma pressure nkT. This can cause the current flow in a column of plasma to be cut off, if you have ever seen bead lightning, it is
thought this is the effect producing the beads.
As to Q value I have not read this paper but I think they are referring to A magnetohydrodynamic safety factor describing the number of times field
lines need to pass round the major circumference of the plasma before they close around the minor circumference; q=(R/a)(BT/BP). Put another way,
plasma Q-value is the value indicating the degree of twist in the spiral magnetic field lines. It is equal to the number of rotations in the main
radial direction for one turn of the magnetic field lines in the sub- radial direction.
[Edited on 24-10-2005 by IrC]
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Marvin
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I think it may be a little unfair to ask someones opinion on fusion who's paper has nothing to do with fusion, but he's in the right area
and his opinion is valid.
I think his point about the Q value is more basic. The Q-value for a fusion reactor is just the thermal power being output divided by the power
required to maintain the plasma in a steady state. Since his paper is about a plasma rocket driven electrically any power that could be obtained by
fusion of the plasma itself would be better than nothing, and he seems to envision a power producing reactor not a million miles away from his plasma
rocket confinement system. I'd probably go furthur than he does though, and say that a working pinch fusion reactor would be better setup to
leak plasma directly, rather than used to heat reaction mass.
I also agree with him. It may be feasable in a few decades, following successful completion of ITER, and it may be used in deep space missions. I
still dont believe we'll see one working within the next 50 years.
He also makes very modest claims about his actual plasma rocket. He's not trying to launch anything into orbit, or even from orbit furthur, just
perform corrections.
To answer the earlier question,
"I'm wondering what assumptions Marvin is making about the type of fusion reactor to be used."
I'm not making any assumptions about the reactor. I am assuming conditions for fusion are similar to the ones showing the most promise
currently. To do anything else would be like booking a holiday expecting to win the lottery in time to pay for it.
"I imagine air would play havoc on any parts that were not made of stable ceramics. "
I think by the time you start reaching plasma temperatures it nolonger matters much what the chemistry of the ionised gas is. Its almost certain to
be boiling off high energy neutrals that cant be contained.
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Quince
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New plasma propulsion, still efficient but thrust increased:
http://news.bbc.co.uk/1/hi/technology/4527696.stm
[Edited on 15-12-2005 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Texium
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19-11-2023 at 10:52 |
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