Re: Space based VLBI - next steps beyond Hubble

On Apr 22, 10:42 am, Ian Parker <ianpark...@xxxxxxxxx> wrote:
On 22 Apr, 13:26, Willie.Moo...@xxxxxxxxx wrote:





On Apr 21, 2:36 pm, Ian Parker <ianpark...@xxxxxxxxx> wrote:

There is one decisive reason why Tokomaks are the preferred choice and
this is the nature of the thermonuclear reaction. 80% of the energy of
fusion goes into neutrons in the case of Tritium and protons in the
case of He3. A pellet is much too small to hold this energy. If we are
using magnetic containment protons will spiral in the magnetic field
and contribute to plasma heating.

To get He3/D to fuse requires twice the temperature of T/D but is
gives off protons not neutrons. To use a tritium reaction you need a
heavy blanket of material which is heated/transmuted by neutrons. This
is why I spole of He3 as the fuel of space. He3/D will if magnetically
contained produce a self sustaining reaction. Hot He4/H which is what
we have is the final and only product. It may well be eaasier to
SUSTAIN He3/D than T/D for this reason.

As I have said inertial containment of a pellet loses 80% of the
energy. This is true of both He3 and Tritium.

  - Ian Parker

I see.  Well, power to weight and thrust to weight are what you want
to optimize.  Using an aneutronic fusor makes things rather efficient
with respect to neutron loss.  You seem to be generally knowledgeable
about what's going on around you, you are still clueless about rocket
design however.  Consider that as long as 80% of the energy is
directed into a jet producing thrust - it doesn't matter for rocket
applications if its lost to the reaction..- Hide quoted text -

- Show quoted text -

Protons and neutrons are omnidirectional.

That's why you use aneutronic reactions - reactions that do not have
neutrons (even though they may be initiated with neutrons)

http://en.wikipedia.org/wiki/Aneutronic_fusion

Please note that Li6D produces alpha particles only.


To have a rocket you need to
use something like liquid hydrogen as a working fluid.

Well, you can heat liquid hydrogen to produce a jet of hot hydrogen
certainly. Obviously, you can make a directed jet of any substance.
The speed of a jet under ideal conditions is given by;

V = sqrt( 2* power / mass flow rate)

for non-relativistic velocities (less than 150,000,000 m/sec)

V is in meters per second
power is in watts
mass flow rate is in kg per second.

So, if you mix in hydrogen, you can estimate how that effects your
exhaust velocity.

Since power level and thrust are related by exhaust velocity; you can
increase mass flow to get more thrust out of a power limited system -
at cost of carrying around larger amounts of propellant.

Doing this you
will get 10km/s approx. The Nerva SI if I recall was about 900secs.

Yes, this is true about Nerva it is a temperature limited system -
which limits the energy which limits the velocity - which means you
want a low molecular weight propellant - hydrogen - but do you
understand the fundamentals? Increase the temperature by using liquid
core or gas core reactions - contained by non-material means - and you
have far superior performances possible.

http://en.wikipedia.org/wiki/Gas_core_reactor_rocket

PULSED operation - circumvents many of the difficulties of a
CONTINUOUS system at the cost of reducing thrust to weight and
requiring a way to smooth out the pulses - but still, pulsed systems
are doable TODAY

http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

BTW - I prefer km/s to secs as a SI has gravity as one of its units.
10km/s is set roughly by the temperature structures can withstand.

Yes - if you place the requirement that the structures remain solid.
However if you remove that constraint either by going with a pulsed
system, or by using some sort of magnetic containment - which is about
1/20th the requirement of a magnetic containment for a fusion system -
then, you don't have those limits.

Looking at the specific energy density of Li6D and U235 you can see
what the upper limit of a rocket built around these fuels can be..
and from that determine what's the best way to proceed.

Look at this 1964 study -

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760065935_1976065935.pdf

and realize that by 1968 the USAF already had determined that a
fission free thernonuclear aneutronic blast was possible.

My query is can an implosion thermonuclear reaction ever be self
sustaining,

In a pulse system you are interested in how much energy does it take
to initiate a reaction (about 10 kJ using a HF laser - built into the
pulse unit - used only once) and how much energy do you get out
(unlimited since limited by size of Li6D pellet which can be any size)
- and what is the burnup fraction (100%)

The chemical laser initiator ignites a deuterium-tritium primary that
then causes a burnup of the Li6D secondary very similar to the
original Teller-Ulam design.

http://en.wikipedia.org/wiki/Teller-Ulam_design


bearing in mind that you have to charge your lasers up
again.

You are not getting what I'm saying. The laser is disposable - think
inkjet print cartridge.

A chemical laser operates by mixing two chemicals that produce light
when they react. Hydrogen and Flourine for example,

http://en.wikipedia.org/wiki/Chemical_laser
http://en.wikipedia.org/wiki/Pulsed_Energy_Projectile

The hydrogen fluoride laser resembles a MEMS rocket engine array.

http://www.me.berkeley.edu/mrcl/rockets.html
http://sciencelinks.jp/j-east/article/200617/000020061706A0418442.php

The chemicals mix in the combustion chamber. The reaction produces
free excited fluorine radicals. Just after the nozzle, the mixture is
injected to the exhaust stream; the hydrogen reacts with the fluorine
radicals, producing excited molecules of hydrogen fluoride. Think of
an old timey flashbulb

http://en.wikipedia.org/wiki/Flash_photography#Flash_bulbs

But tinier and faster.

The excited molecules then undergo stimulated emission in the optical
resonator region of the laser.

http://en.wikipedia.org/wiki/Fabry_perot_etalon

The whole thing releases 10,000 Joules of optical energy in about 1
nano-second creating a 10 terawatt pulse.

Hydrogen/flouride material is about 3% efficient so you'll need 340 kJ
of reactants to produce 10 kJ of laser photons. With 150 kJ per gram
of material, that's about 2.25 grams of hydrogen and flourine
materials.

Think about metal hydride storage of hydrogen. Now, think about
silicon hydride storage of hydrogen.

http://en.wikipedia.org/wiki/Silicon_hydride

Now consider silicon flouride storage of flourine.

http://en.wikipedia.org/wiki/Silicon_tetrafluoride

Now think about a MEMs based layer between these two surfaces - that
cause them to combine - and concentric rings of Fabrey Perot etalons
focusing the laser energy to a central 'dot' of deuterium and tritium.

http://upload.wikimedia.org/wikipedia/commons/b/b8/Fusion_microcapsule.jpg

The whole thing is about 3/4 inch in diameter and weighs as much as 3
pennies -and costs less than $1.32 each.

There is a mechansim surrounding the whole primary that focuses the
blast along a tube-like Li6D secondary - located in a tube-like
tamper. This system masses 5 pennies. A penny weighs about a gram.

See the Teller-Ulam article to get an idea of this.

So, a capacitor bank is charged up while the device is accelerated
electromagnetically into the reaction chamber. The capacitor bank
discharges driving electrical heating elements across the two 'storage
surfaces' hydrogen and flourine pour out of the surfaces into the
porelike MEMS rocket nozzle array and exhaust into the etalon region.
Light energy is processed by the optical cavities and focused radially
inward to the pellet - while a theta-pinch fiber - energized by the
current flowing to the heating elements squeezes the expanding
deuterium-tritium plasma ball.

http://en.wikipedia.org/wiki/Pinch_%28plasma_physics%29

This detonates the primary which then flashes through the secondary
setting it off.

4.6 grams of Li6D in this system - are detonated, releasing the
equivalent of exploding 27.6 tons of TNT - nearly ALL the resulting
energy is in the form of helium nuclei - which are easily deflected -
despite their high energy - by a magnetic containment and magnetic
nozzle.

The entire thing is about the size of a small arms round

Implosions are viiewed not as thermonuclear solutions but as
research tools.

This is meaningless. I've given this subject a lot of thought, based
on my training and deep study - you have said nothing that indicates
you understand the subject let alone saying anything that suggests
I've made any mistakes or errors in my research and design.

The question of heat loss is relevant in terms of
sustainability, as well as everything else.

This too is meaningless. The plasma will lose a specific amount of
energy in the form of radiation due to Stephan Boltzmann - that's
calculable given the reaction conditions. This radiation - mostly UV
and gamma rays - will be less than 0.01% of the total - frozen flow
losses in the plasma account for 10% which is radiated by the cooling
jet behind the spacecraft - but this is not a problem given the
wavelength and diffuse nature of the light.

The 'flash' loss of detonation will require a rather massive radiation
reflector pointing those flashes away from the cabin if we are to have
continuous operation of the ship. Absorbing even 0.1% - would
overheat most systems - so, that's not even attempted.

This sheild, can also be used to sheild against space and solar
radiation, and is where the cabin level is where passengers and crew
sleep and spend most of their time.

.

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