Ion engines

I did some calculations on current ion engines, and it's rather ugly.
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust. Yes it's freaking tonnes. Add to
that 4000 s ISP, and space warships are realizable with current
technology (actually it's a little outdated technology because the
energy source I used for calculation had only 1/5 efficiency.).

The biggest problem would be that faux pass named Xenon, which is a
nice sleeping gass, however there are cheaper things that could be
used as an ion engine fuel.

So does anyone know a resource where I could discover a mass of a
lightened 30 m mirror with adaptive optic? 1 MW free electron laser
was placed into an aircraft, so weight of these things can't be that
bad.

Considering it took me few tens of hours to look around internet for
reliable informations about current ion engines there is a little
table just in case someone would need it.

10/0.36/4000
6/0.2/5500
8/0.3/3200
10.5/0.25/6000
250/2.5/19000
11.6/0.0128/13116 (1.6/0.08/4000 with H)

Of course you can add another ones to the list.

BTW you can try to guess names of engines on that list. ^_^

On May 30, 9:01 am, Raghar wrote:
1 MW free electron laser was placed into an aircraft

There was a study by Jefferson Labs that suggested a weaponized FEL be
placed in a modified 747, but this beastie has never been built. The
highest power FEL that has ever been operated is the Jefferson Labs
laser, which puts out several tens of kilowatts, not megawatts, and
takes up a considerable portion of a building.

Luke

On May 30, 12:15 pm, Luke Campbell wrote:
On May 30, 9:01 am, Raghar wrote:

1 MW free electron laser was placed into an aircraft

There was a study by Jefferson Labs that suggested a weaponized FEL be
placed in a modified 747, but this beastie has never been built. The
highest power FEL that has ever been operated is the Jefferson Labs
laser, which puts out several tens of kilowatts, not megawatts, and
takes up a considerable portion of a building.

Luke

I think he's talking about the US Airborne Laser project, which
consumes power on the megawatt scale (though I think it only produces
a kilowatt-level beam) and weighs "only" 7 tons. Apparently it's
actually been built, tested, and flown on an airplane, but not test-
fired in flight.

On May 30, 2:27 pm, Damien Valentine wrote:
I think he's talking about the US Airborne Laser project, which
consumes power on the megawatt scale (though I think it only produces
a kilowatt-level beam) and weighs "only" 7 tons. Apparently it's
actually been built, tested, and flown on an airplane, but not test-
fired in flight.

The ABL is a megawatt class laser, but it's a _chemical_ laser (more
exactly a Chemical Oxygen Iodine Laser). See http://www.airforce-
technology.com/projects/abl/, for example.

--
Mariano M. Chouza
http://mariano.chouza.googlepages.com

Raghar wrote in
ups.com:

I did some calculations on current ion engines, and it's
rather ugly. Why would anyone say ion engines are weak? In
that custom calculation the engine had 7 tonnes of thrust.
Yes it's freaking tonnes. Add to that 4000 s ISP, and space
warships are realizable with current technology (actually
it's a little outdated technology because the energy source
I used for calculation had only 1/5 efficiency.).

You must have confused newtons with something else, or
you're just confused, period.

Mostly you're just wildly wrong.

--Damon

Raghar wrote:
I did some calculations on current ion engines, and it's rather ugly.
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust.


That seems wildly improbable. Let's see your calculations.

Sylvia.

Raghar wrote:

I did some calculations on current ion engines, and it's rather ugly.
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust. Yes it's freaking tonnes. Add to
that 4000 s ISP, and space warships are realizable with current
technology (actually it's a little outdated technology because the
energy source I used for calculation had only 1/5 efficiency.).

Since you didn't indicate what calculations you made, that's probably
where the error is.

--
Erik Max Francis && && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM, Y!M erikmaxfrancis
Chastity the most unnatural of the sexual perversions.
-- Aldous Huxley

On 30 May 2007 09:01:27 -0700, Raghar wrote:

I did some calculations on current ion engines, and it's rather ugly.
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust. Yes it's freaking tonnes. Add to
that 4000 s ISP, and space warships are realizable with current
technology (actually it's a little outdated technology because the
energy source I used for calculation had only 1/5 efficiency.).

Did your calculations indicate that your custom ion engine was fifty
meters in diameter and required roughly 1.5 gigawatts of electric
power?

Because if they didn't, you got the math wrong.


The biggest problem would be that faux pass named Xenon, which is a
nice sleeping gass, however there are cheaper things that could be
used as an ion engine fuel.

Oops, now your ion engine is sixty meters in diameter and requires
a full two gigawatts of electric power.


So does anyone know a resource where I could discover a mass of a
lightened 30 m mirror with adaptive optic? 1 MW free electron laser
was placed into an aircraft, so weight of these things can't be that
bad.

You have a budget for two thousand of them?


Considering it took me few tens of hours to look around internet for
reliable informations about current ion engines there is a little
table just in case someone would need it.

10/0.36/4000
6/0.2/5500
8/0.3/3200
10.5/0.25/6000
250/2.5/19000
11.6/0.0128/13116 (1.6/0.08/4000 with H)

BTW you can try to guess names of engines on that list. ^_^

Or you could provide us with the units for that list. Because
I'm guessing that's part of the math you got wrong.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-718-0955 or 661-275-6795 * -58th Rule of Acquisition *

In article . com,
Raghar wrote:
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust. Yes it's freaking tonnes. Add to
that 4000 s ISP...

Assuming that by "7 tonnes" you mean circa 70 kilonewtons of thrust -- a
tonne is a unit of mass, not force -- that's an interesting engine. With
a much more interesting power supply.

70,000N of thrust and 4000s Isp (that is, exhaust velocity circa
40,000m/s) at, say, 50% DC-to-jet efficiency -- which would be pretty good
for an ion engine, although you need to read the spec sheets *VERY*
carefully to realize this, because they have a bad habit of quoting only
partial efficiencies rather than the end-to-end total -- requires a 2.8GW
power supply.

(This is simply conservation of energy, with a "per second" on energy
and mass: power = 0.5 * thrust * exhaustvelocity / efficiency, bearing
in mind that thrust = massflow * exhaustvelocity.)

The very largest nuclear (etc.) power plants -- which weigh millions of
tons -- put out that kind of power.

And of course, at 50% efficiency, nearly half that power comes out as
heat. Worse, the power plant itself is only maybe 30-40% efficient. So
you have 5-6GW of heat that you have to get rid of, somehow. (The power
plants do this with rivers of cooling water, or immense cooling towers
that use up lots of water to help dump heat into huge masses of air.)

By the way, by no stretch of the imagination are gigawatt ion engines
"current technology". But it's definitely not worth bothering with
calculations about the *engines* until you explain what you're using for a
power supply and a cooling system.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

On May 30, 8:05 pm, John Schilling wrote:
On 30 May 2007 09:01:27 -0700, Raghar wrote:
I did some calculations on current ion engines, and it's rather ugly.
Why would anyone say ion engines are weak? In that custom calculation
the engine had 7 tonnes of thrust. Yes it's freaking tonnes. Add to
that 4000 s ISP, and space warships are realizable with current
technology (actually it's a little outdated technology because the
energy source I used for calculation had only 1/5 efficiency.).

Did your calculations indicate that your custom ion engine was fifty
meters in diameter and required roughly 1.5 gigawatts of electric
power?

How'd you get the diameter?