Nuclear fusion rocket eingine
Jim Relsh
http://wsx.lanl.gov/MTF/mtf-pix/images/MTF-Schematic-color.jpg
Looks like a candidate for a nuclear fusion rocket engine, I kid you not.
What would the ISP be of such an engine? 10.000 seconds or so? Could this
make cheap space travel with tiny spaceships a reality? You know like the
one in Aliens which is about as big as a helicopter yet is still able to go
into orbit.
--
Posted via a free Usenet account from http://www.teranews.com
Willie...@gmail.com
This looks like a fusion test of a variation of electromagnetic
compression technique. How does the liner get replaced?
Specific impulse is a function of exhaust speed,
Isp = Ve / g0
and exhaust speed is a function of temperature
Ve = SQRT( f(To))
where f(To) depends on the following gas conditions (assuming
isentropic expansion)
f(To) = ((2 *W *gamma *R *To)/(gamma - 1))*(1 - (Pf/Po) ^((gamma - 1)/
gamma))
Where
W is the mean molecular weight of the exhaust
gamma is the ratio of specific heats of the exhaust
R is the universal gas constant
To is the operating temperature of the rocket's reaction chamber
Po is the operating pressure of the rocket's reaction chamber
Pf is the exhaust pressure
The only real reaction variable here is the chamber temperature and
pressure and the pressure ratio between exhaust and chamber is a
design variable depends on teh expansion ratio between throat area and
exhaust area.
But there is a limit a supersonci flow can get to, which is a function
of gas conditions again;
Pf/Po = (2/(gamma+1)*(gamma-1)
So, like I said, its really a function of chamber temperature and the
gas exhausted.
The temperature and pressure and efficiency of the reaction is unknown
from your link. However, an ideal fusion reactor rocket would start
out with hydrogen and end up with helium and no hydrogen.
Under those conditions you'd have about a 20,000,000 m/sec exhaust
speed. - or 2 million seconds Isp.
A constant gee interplanetary spaceship is possible with this sort of
performance.
Top velocity is related to distance
d = 1/2 g0 t^2
Vf = g0 t
so
d =Vf^2 / (2 g0)
then
Vf = SQRT(2 g0 d)
So, halfway to the moon is 193,000 km or 193 million meters
Vf = SQRT(2 * 9.82 * 193,000,000) = 61,600 m/sec
then you flip over and slow down to achieve zero speed at zero
altitude above the moon.
That means the vehicle's total velocity is 123,200 m/sec - and to
boost back at a constant speed - doubls that value again to 246,400 m/
sec.
That's your mission delta vee. The trip time each way would be
double the boost time to the halfway point which is just the boost
speed divided by g0
61,600 / 9.82 = 6,272.8 seconds --> 1.742 hours ~ 1 hr 45 min
So, it'll take 3 hr 30 min to go from Earth to Moon at one gee.
I assume I boost off Earth at 2 gees and drop acceleration as a
function of 1/r^2 - and then add it in for the moon so you boost at
1+1/6 gee at lunar touch down. This adds a few percent to the delta
vee requirement to about 260,000 m/sec..
Now, we know Vf - 260,000 m/sec and Ve - 20,000,000 m/sec .so we can
figure propellaant fraction
Vf = Ve * LN(1/(1-u))
Where u = propellant fraction
rewrite this to solve for u
u = 1 - 1/EXP(Vf/Ve) = 0.0129
Approximately 1.3% of the total weight of the vehicle must be hydrogen
fuel.
So if we have something the size and capacity of an automobile -
something that weighs about 6,600 pounds at lift off (3 tons) it would
have to carry 1.3% about 85.2 pounds (38.7 kg) of hydrogen - which in
liquid form would take up about half a cubic meter.
Power exhaust speed and thrust are related to one another. To
generate the required 13,200 pounds of thrust at an exhaust speed of
20 million m/sec requires a lot of power
F = mdot * Ve
P = 1/2 * mdot * Ve ^ 2
F = newtons = 58,920 newtons = 13,200 pounds force
mdot = 58,920 / 20,000,000 = 2.946 grams per second
P = 1/2 * 0.002946 * 40 trillion = 58.92 giga-watts
This drops to half this figure at the flip-over point. This power
level is sufficient to power the East Coast of the United States. Or
put differently, converting this to 20 GW of electrical power and
selling it at $0.03 per kWh - produces $600 million each hour of
operation.
So, this suggests how to get your travel money for your trips.
Any prompt neutrons produced would be deadly at this power level.
That's why aneutronic reactions are preferred.
http://en.wikipedia.org/wiki/Aneutronic_fusion
We have enough information here to figure out the propellant fractions
to get to mars and so forth.
If we fly to Mars at 77 million km distance that means we boost at one
gee for 38.5 million kilometers - that's 38.5 billion .meters so;
Vf = SQRT(2 * 9.82 * 38.5 billion ) = 869,563
This takes 88,950 seconds or 24.6 hours - about a day to reach the
half way point. Four times these values give mission delta vee and
times. Travel time of four days - and top speed of 3,478,252 or 3.5
mllion m/sec
u = 1/EXP(Vf/Ve) = 0.15953
about 16% of the propellant mass is hydrogen. So, for our 3 metrtic
ton vehicle - about the size of an SUV - 480 kg of hydrogen is
needed. about 6.85 cubic meters of fuel.
The minimum energy transfer orbits between the moon and planets are
four days to the moon and 8 months to mars. A constant boost
transfer to the moon is 4 hours to the moon and two days to mars. The
first trip times are equivalent to the great sailing ships of
exploration in the 16th century. The second trip times are equivalent
to the air travel times of aircraft before the jet age.
BradGuth
Willie.Moo will gladly take you to the moon and back in no time at
all. The only problem being that we'll all be broke as well as dead
and gone long before anything of William Mook ever gets accomplished,
especially for other than his rich and powerful friends because, the
rest of us minions as village idiots simply don't count any more so
than salvaging our badly failing environment matters to the likes of
lord Mook.
In his mindset bed of continual denial, he of course doesn't think so,
but it's pretty much another one of those MI5/CIA Jewish things. If
we go into nuclear rockets, it'll be China or India with something of
a Thorium and U233 breeder basis for the required energy of driving
those very large ion propulsion thusters, and otherwise it'll be the
renewable and clean burning likes of h2o2 plus a little synfuel usage
that get large payloads efficiently into LEO.
. - Brad Guth
BradGuth
Willie.Moo never has to think about stopping whatever spacecraft, or
about many other consequences to our frail human DNA. Of course you
believe in anything published by your corrupt government, even if
there's all sorts of those innocent dead bodies lying all about, the
rest of us are broke and there's yet another Christ placed on a stick
to boot.
. - Brad Guth
Martha Adams
unfortunate choice of name is a puzzle to me. But
I liked the piece he wrote: it stirs me to recall
some of my math and physics from decades ago, and
to study out what he says.
Titeotwawki -- mha [sci.space.policy 2008 Feb 19]
"BradGuth" <brad...@gmail.com> wrote in message
news:7d82c78c-6602-473e...@u10g2000prn.googlegroups.com...
> On Feb 19, 3:04 am, Willie.Moo...@gmail.com wrote:
>> On Feb 14, 5:13 pm, "Jim Relsh" <jrel...@gmail.com> wrote:
<snip>
Ian Parker
Not with tiny spacecraft. Thermonuclear fusion requires a given engine
size. You need a certain Int(B)dl call it a magnetic potential. To
shrink your engine you will need higher magnetic fields.
There is one other very important point. Tritium cannot be used for
space propulsion - reason 80% of energy coming off is in the form of
neutrons. You must have He3 and deuterium in space. Energy now comes
off in the form of protons and will cause the plasma to heat and
expand.
As far as specific impulse is concerned this can be varied. If you
have a pure helium exhaust you have about 20,000km/s. However in
practice you would use a working fluid. I would suggest mixing either
with liquid hydrogen, or in the case of a hypersonic aircraft, just
possibly, air. You would probable settle for 20-100 km/s depending on
mission. Some 20km/s for the Moon, a bit more for Mars.
- Ian Parker
Douglas Eagleson
If you stick a 1e18 neutron/sec tritium targeted neutron generator in
the system a basic fusion will blow it up. It is hard to control
large plasmas when you get real fusion exothermically occuring. And
the usage of neutron is critical to understanding the exact reaction.
x2neutron + H + H -> ? + x1 neutrons Where x1>x2
So the old 1million curie DT accelerator at Livemore could power the
drive engine nicely. Just think small little plasmas and likely a
pulsed fusion.
Douglas Eagleson
Gaithersurg, MD USA
BradGuth
> Why 'Willie.Moo' wants to impeach himself with that
> unfortunate choice of name is a puzzle to me. But
> I liked the piece he wrote: it stirs me to recall
> some of my math and physics from decades ago, and
> to study out what he says.
>
> Titeotwawki -- mha [sci.space.policy 2008 Feb 19]
>
>
> news:7d82c78c-6602-473e...@u10g2000prn.googlegroups.com...
>
> > On Feb 19, 3:04 am, Willie.Moo...@gmail.com wrote:
> >> On Feb 14, 5:13 pm, "Jim Relsh" <jrel...@gmail.com> wrote:
>
> <snip>
I agree, our Willie.Moo and his CIA World FactBook are always
interesting to hear about, as well as for all the other 4th, 5th or
whatever second hand resources of those interesting numbers.
Unfortunately, our Willie.Moo hasn't actually contributed anything
original, nor has our Willie.Moo (aka William Mook) accomplished much
of anything on behalf of delivering his green hydrogen.
I've asked for his wizardly assistance, and instead it's all
Willie.Moo, or else you get nothing. His continual out-of-context or
off-topic rants are vary much focused upon spending every last cent of
our hard earned loot, and apparently our badly failing environment,
limited fossil energy resources and equally failing American way of
life is just going to have to wait until lord all-knowing Mook is
fully in charge, because only his mindset of physics and science is
what counts, at the same time as the past simply doesn't count.
In other words, the means always justifies the ends, such as for all
of the bad that transpired as of yesterday is simply without a speck
of remorse in the good Old Testament book of Mook.
If ever the DNA/RNA of Hitler needed to be cloned and born-again, our
Willie.Moo and those of his pretend-atheist posse is it, because it's
all-or-nothing his way, or else.
. - Brad Guth
Ian Parker
There is one question which spings to mind. If you are going for a
quasi inertial confinemenement, why not accelerate "warm" 250ev plasma
to high velocity and create shock waves. Could we make a kind of
scramjet out of thermonuclear material?
Plasma is, of course, extremely conducting and a linear induction
motor could accelerate it to high speed.
- Ian Parker
BradGuth
Terrific idea, however our own Willie.Moo has already been there and
done that, of which means that no one else can even consider the
thought without his all-knowing expertise of how to best spend our
hard earned loot.
. - Brad Guth
Ian Parker
As you know I am in favor of a commercial edge. That is to say space
would not be primerally funded by the taxpayer. Mark R. Whittington
has posted on the space policies of the 3 realistic contenders for the
Presidency. Point is Barack Obama does not appear to be being punished
by the electorate for his negative attitude to manned space flight.
The fact that Hillary not him is suffering leads me to believe that
manned spaceflight SUPPORTED BY THE TAXPAYER must be regarded as a
thing of the past.
As I have stated earlier governments (all governments) are supporting
basic research. Thermonuclear fusion must come into this category at
the moment. These days a lot can be done by a finite element analysis.
My suggestion is that anyone investigating inertial fusion from a warm
plasma should at least put shockwaves and a continuous flow onto a
supercomputer or or posssibly just a network of 2GHz PCs.
Certainly if thermonuclear fusion could be made to work (as I said
only He3 can possibly give a continuous flow) the costings for manned
spaceflight would radically change. William Mook could go to Ceres,
but he would have to get the money from a merchant bank, not the
government. With a large demand for catalysts "Ceres Platinoids" could
be viable, as would space tourism.
- Ian Parker
BradGuth
I 100% agree, in that at best it should become a 50/50 thing.
>
> As I have stated earlier governments (all governments) are supporting
> basic research. Thermonuclear fusion must come into this category at
> the moment. These days a lot can be done by a finite element analysis.
> My suggestion is that anyone investigating inertial fusion from a warm
> plasma should at least put shockwaves and a continuous flow onto a
> supercomputer or or posssibly just a network of 2GHz PCs.
Our NASA has the newest and best supercomputer of 2048 fast CPUs, that
for the most part is just sitting around collecting dust. So, since
that's yet another 100% public owned, housed and operated tidbit of
nifty technology, having all the very best of software to boot, we
should just use a small portion of those extremely fast CPUs for doing
whatever's within the best public and environment interest.
>
> Certainly if thermonuclear fusion could be made to work (as I said
> only He3 can possibly give a continuous flow) the costings for manned
> spaceflight would radically change. William Mook could go to Ceres,
> but he would have to get the money from a merchant bank, not the
> government. With a large demand for catalysts "Ceres Platinoids" could
> be viable, as would space tourism.
>
> - Ian Parker
I agree, that all-knowing wizards like our Willie.Moo could kick
serious nuclear, fusion and/or ion rocket butt, and get that deployed
and/or extended mission cost per tonne way the hell down without
further polluting mother Earth in the process. With the 50/50 public
matching funds worth of backing up whatever's privately invested
should more than do the trick, or we can just sit back and watch China
or even India do most everything.
. - Brad Guth