Polynitrogen Rocket Fuel

"sanman" wrote

I don't think it matters that it would take a lot of energy to make
anti-matter for rocket fuel. The thing that counts is energy density,
from what I can see, even if it takes a lot of energy to make the High
Energy Density Material.

I'd say you were correct. The cost of building the atomic bomb was much
greater than that of building enough B-29s to drop 13kt of conventional
explosives but the impact, literal and otherwise, of the Bomb made it worth
it militarily speaking.

The same would apply to an anti-matter weapon.

Presumably most portable energy sources - gas cylinders for instance - are
similarly inefficient.

On Wed, 3 Nov 2004 19:02:59 -0000, John Redman
om wrote:


"sanman" wrote

I don't think it matters that it would take a lot of energy to make
anti-matter for rocket fuel. The thing that counts is energy density,
from what I can see, even if it takes a lot of energy to make the High
Energy Density Material.

I'd say you were correct. The cost of building the atomic bomb was much
greater than that of building enough B-29s to drop 13kt of conventional
explosives but the impact, literal and otherwise, of the Bomb made it
worth
it militarily speaking.

The same would apply to an anti-matter weapon.

Presumably most portable energy sources - gas cylinders for instance -
are
similarly inefficient.




I don't think I can advise you in strong enough terms not to use
anti-mater weapons!

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On Wed, 3 Nov 2004 16:55:20 -0000, "Keith Willshaw"
wrote:


"sanman" wrote in message
. com...


Hmm, I'd like to ask more about this.

I don't think it matters that it would take a lot of energy to make
anti-matter for rocket fuel. The thing that counts is energy density,
from what I can see, even if it takes a lot of energy to make the High
Energy Density Material.


It matters because if the cost works out a million dollars
per microgram you wont build many rockets, the current
price is around 62.5 million per microgram

Exactly: as I tell my friends about the very entertaining "Angels and
Demons" book, I preface it by saying that first you must make the
gigantic suspension of disbelief that it actually makes sense to
-make- anti-matter [non-spoiler IMO as it is obvious to anyone with
a nodding acquaintance with science that that's what is going on.]




But I'd like to ask about the feasibility of using anti-matter as a
rocket fuel.
Are there any lingering environmental dangers posed by anti-matter?
From what I've read, anti-matter will anihilate with ordinary matter,
releasing only X-rays.

That's true for electrons and positrons (anti-electrons). They'll produce
gamma rays at 511,000 electron volts.
But heavier particles like protons and anti-protons are somewhat messier,
making gamma rays and leaving a spray of secondary particles that eventually
decay into neutrinos and low-energy gamma rays.

And of course, X-rays are very hard to capture.
But aside from that, will X-rays fracture enough surrounding nuclei to
lead to lingering radioactive decay radiation that causes
environmental concerns?

Sorry to phrase it in environmental terms, but that's where all the
political controversy is. Politically, nobody seem to care if the
launch crew gets killed, just as long as there isn't some kind
lingering contamination for the general public to feel scared about.




But suppose some material or mechanism could be found to capture and
harness that X-ray energy for propulsive purposes. Wouldn't there be
an inherent amount X-ray exposure to the flight crew? Or could you
tailor the matter-antimatter anihilation to somehow minimize this?

I realize that if your magnetic bottle blinks and you lose the
magnetic containment, then your entire fuel supply will blow up in a
big X-ray burst, and there would be no hope of the flight crew
surviving. But if it only takes a few minutes to get up into space,
then your crew only has to be near the anti-matter for that short
period of time. And how much anti-matter would you really need, just
to get a Saturn-V type of payload into orbit?

Your crew would be sitting at the top of the Saturn-V sized rocket,
and the ittybitty quantity of anti-matter would be sitting all the way
at the bottom of it.

99% of the volume of the Saturn V is used
to store fuel. Your antimatter drive could have a specific
impulse 100 times better than a H2O2 rocket thus reducing
the volume of propellant needed to 1% of that of the
Saturn V

http://science.nasa.gov/newhome/head...p12apr99_1.htm

Keith

John Thingstad wrote:

Oh, just wonderful! Just what we need. A more powerful bomb..
Antimatter is a great source of energy if used intelligently.

Antimatter for bombs is an extraordinarily stupid idea, and
not because it makes bombs 'more powerful' (it doesn't, really).

Nuclear weapons are important mainly because they are so
damned cheap to make and deliver, per unit energy released.

Antimatter is extremely costly to make, per unit energy.
At current manufacturing efficiency, a large nuclear powerplant
could, over 30 years, supply enough energy to make only
enough antimatter to have the yield of a single *high explosive*
bomb. This is obviously ludicrously noncompetitive. Even
boosting the efficiency by orders of magnitude would not
save the idea.

Then there's the little fact that antimatter requires constant
confinement suspended without contact in extremely high vacuum
(and, for antihydrogen, at extremely low temperature, 1 Kelvin or
less, to keep the vapor pressure low enough so there is not
thermal runaway). Anything goes wrong and BOOM. In contrast,
nuclear weapons can be designed so that accidental initiation
is very difficult to achieve, even in violent accidents.

Paul

On Thu, 04 Nov 2004 08:00:03 -0600, Paul F. Dietz wrote:

John Thingstad wrote:

Oh, just wonderful! Just what we need. A more powerful bomb..
Antimatter is a great source of energy if used intelligently.

Antimatter for bombs is an extraordinarily stupid idea, and
not because it makes bombs 'more powerful' (it doesn't, really).

Nuclear weapons are important mainly because they are so
damned cheap to make and deliver, per unit energy released.


Correct. At a price of something like 6500 million a gram I doubt
if it makes much sense as bomb material.
The bomb itself would cost more the anything it is likely to destroy
Hence it is good for destroying the users economy faster than
the enemies.
As I mentioned I am not exactly loosing sleep over it (yet)
Still fact remains that the navy is looking into the possibility.
But then it is hardly the first stupid project the navy has founded.

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On Thu, 04 Nov 2004 16:01:53 +0100, John Thingstad
wrote:

Correct. At a price of something like 6500 million a gram I doubt
if it makes much sense as bomb material.
The bomb itself would cost more the anything it is likely to destroy
Hence it is good for destroying the users economy faster than
the enemies.
As I mentioned I am not exactly loosing sleep over it (yet)
Still fact remains that the navy is looking into the possibility.
But then it is hardly the first stupid project the navy has founded.


I might add that like the hydrogen bomb there is really no limit to how
big you could make the bomb. If you had unlimited resources and patience
you could make a bomb any size you want.
A anti-matter bomb would be 1000 times more powerful per weight than
a nuclear bomb and 200 times more powerful than a hydrogen bomb.
That is if I remember the figures correctly.

So it makes the *ultimate* rocket fuel. Of course if you get a power
failure...
ka-boom... instant vapor.
Failure at launch would be a spectacular event taking out most of the
state... Anyways at the current level of technology I doubt if we need be
too worried anytime soon. Having determined the insane cost's of this
matter.

It will by it's nature always be a ridicolusly expensive fuel to use given
that the only way to produce anti-matter is from pure energy.
Today taking a particle accelerating it in a accelerator and then
letting the particle 'crash' into a tungsten filament.
This the gives off a gamma quant which again decays into a positron
electron pair.

I once envisioned something I called a phase up converter.
This would use photons to kick up electrons to higher energies in steps.
Then it would kick protons into higher orbits. Finally the photon
would be sufficiently powerful to produce matter, anti-matter pairs.
An entertaining idea though I have no idea if it would work.

Still, as a sci-fi buff, the idea of anti-matter fuel is irresistible

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Oh, just wonderful! Just what we need. A more powerful bomb..
Antimatter is a great source of energy if used intelligently.

Antimatter for bombs is an extraordinarily stupid idea, and
not because it makes bombs 'more powerful' (it doesn't, really).

And it's not an energy source. Making it is a net energy drain.

On 04 Nov 2004 19:27:42 GMT, G EddieA95 wrote:

Oh, just wonderful! Just what we need. A more powerful bomb..
Antimatter is a great source of energy if used intelligently.

Antimatter for bombs is an extraordinarily stupid idea, and
not because it makes bombs 'more powerful' (it doesn't, really).

And it's not an energy source. Making it is a net energy drain.

Sigh! But once you have it it is a very compact source of energy.. yes
Technically the sun could provide almost unlimited energy.
The troposphere is 12 million degrees kelvin, yes.
And the magnetic current's it gives a near unlimited source of electricity.
Anti-matter is certainly not a option today.
Tomorrow? Who knows. The energy to produce large quantities is out there.
Also taking the anti-matter off earth removes the risc of human life.
There seems to be no reason why such a facility could not be made fully
automatic.

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"Christopher M. Jones" wrote in message ...
sanman wrote:
What would you all recommend as a promising High-Energy Density
Material?

Uranium, Plutonium, Deuterium...

Or if you want to be more exotic, anti-matter. There is still the "slight"
problem fission or fusion will usually produce neutrons, some of these will
produce gamma rays, fission has nice radwaste like Strontium-90 and so on.
Not very nice to run inside a biosphere, which is where we need the better
propulsion anyway! *sigh*

If you want high ISP, low thrust propulsion for deep space IMHO the problem
has already basically been solved with ion engines in their many variants.

The problem is to get out of this gravity well we call Earth we want reasonably
high ISP and high thrust, with low toxicity.

All the fission rockets designs I know usually try putting the fission bits
directly in the exaust to enhance performance, which is not nice. Fusion is
a bit useless unless you propose to use fusion bombs, which actually work and
have nice energy density. Once again you get gamma rays and ****.

Then we have the microwave/laser propulsion concepts, which are nice. Except
that you need a beam in every gravity well and lasers are still ludicrously
expensive. I suppose the idea is not too dissimilar from the space elevator
(large infrastructure costs, fixed position, etc) but with higher energy costs.

So I think the best bets are gas core nuclear, without emission of rad waste,
and microwave/laser propulsion. Orion pollutes too much, the space elevator
requires unobtanium.

The cold fusion lunatic fringe claims to be able to do net positive D+D nuclear
fusion without any emission of neutrons whatsoever. If this is actually true,
great, we may have just solved all of our problems. But I wouldn't put much
faith into it.

On 4 Nov 2004 12:36:28 -0800, quasarstrider
wrote:

There is always VASIMR
http://www.space.com/businesstechnol..._020807-1.html

VASIMR is basically a tokamak reactor which heats up ions but not
enough to create fusion temperatures. The flip side is that it needs a lot
of energy.
That means a nuclear reactor.
Still it creates a large impulse from a Small amount of gas.
A VASIMR could travel to mars by continuous acceleration in 3 months.
This would alts eliminate the problems of withstanding zero gravity for
long times. I think VASIMR is probably the most promising space propulsion
system we have to day and have no forgiveness for the idiots that
continually
try to trash it by removing the funding.

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