Microwave beamed power

zoltan wrote:
[...]
I have an experimental air breathing engine that generates about 1 MW
of power in terms of
the heat output of the propane burnt. This engine has a 7 inch nozzle
and an Isp of 4000.

That seems very good --- Armadillo's only getting an ISP of a few hundred on
their biprops. Do you have any more information?

One thing I do have to ask is, at what range of speeds will it air-breathe?
Sucking in stationary air on a bench is a *very* different thing from
running at hypersonic speeds in the upper atmosphere.

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+- David Given --McQ-+ "...you could wire up a *dead rat* to a DIMM
| | socket, and the PC BIOS memory test would pass it
| ) | just fine." --- Ethan Benson
+- www.cowlark.com --+

"zoltan" :

If you could boost the Isp to say 1000 you would not need nearly as
much power as 15GW.

I have an experimental air breathing engine that generates about 1 MW
of power in terms of the heat output of the propane burnt. This engine
has a 7 inch nozzle and an Isp of 4000.

No, you don't. You have an air-breathing engine that at static workbench or
at a fraction of a mach speed appears to work that well. What you don't have
is a supersonic engine. As far as I know you still have not flown your
design to see how it performs at even a good fraction of a mach.

To get to orbit at an Isp of 1000 you need a mass ratio of 2.5
To get to orbit at an Isp of 400 you need a mass ratio of 10
You could probably get the shuttle to orbit on 5GW received power.

GW is a rate of power flow, not a total sum. That are other factors than
just mass-ratio. That is why there are no beer-can size SSTO rockets being
built.

Zoltan

Earl Colby Pottinger

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David Given :

zoltan wrote:
[...]
I have an experimental air breathing engine that generates about 1 MW
of power in terms of
the heat output of the propane burnt. This engine has a 7 inch nozzle
and an Isp of 4000.

That seems very good --- Armadillo's only getting an ISP of a few hundred
on
their biprops. Do you have any more information?

One thing I do have to ask is, at what range of speeds will it air-breathe?
Sucking in stationary air on a bench is a *very* different thing from
running at hypersonic speeds in the upper atmosphere.

He have been making this claim for over a year now. The one thing he seems
to refuse to do is to test fly it.

Infact, he will not even strap it onto a car and test it at low speeds (0-100
mph). For some reason he thinks his intake has no drag.

Earl Colby Pottinger


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I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

bob wrote:
zoltan wrote:

The Powers are just HUGE. One SSME, assuming 100% energy conversion to
kinetic energy of the exhaust is about 5GW . Thats 15 GW for the space
shuttle. In practice you will need a lot more than this.

At 1 GW per nuclear reactor, 15 nuclear reactors. Expensive, but
doable. The French manage to generate nuclear electrity at
3 eurocents/kWh. That would be about $0.036 USD/kWh.

Wouldn't the fact that the vehicle weighs less (because you need less
fuel) mean you need less power to move it up the gravity well than
Shuttle?

This is Massive. Producting that kinda power in microwaves has only been
done on paper and the reality is that its unlikely to scale up as nicely as
you mite like.

A prototype does not need to be as big as the Shuttle.

If you need more power, just use a bunch of microwave generators
instead
of just one. The microwave generator is going to be fixed in the
ground,
size and weight don't matter. Just cost.

Bottom line. Chemical rockets are not as bad as you mite think.

Yes they are bad. They may be the best we got, but they still suck.

zoltan wrote:
I have an experimental air breathing engine that generates about 1 MW
of power in terms of
the heat output of the propane burnt. This engine has a 7 inch nozzle
and an Isp of 4000.

Jet engines are not rated in ISP, but fuel consumed per hour per unit
thrust. They need air.

You could probably get the shuttle to orbit on 5GW received power.

Higher ISP means more energy is put into the exhaust. Also it will be a neat
trick to get a jet engine to work in a vacuume.


greg.

Joe Strout wrote:
In article . com,
"William Mook" wrote:

Gaseous hydrogen and gaseous oxygen can be entrained in a spongelike
hydrocarbon aerogel and create a mixture less dense than air!

And here I've been giving my kids helium balloons that last only a week
or two. Where can I get some of this lighter-than-air aerogel?

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

lighter-than-air aerogel? sounds like a good material to build aircraft
from but it could become a very difficult to clean up form of litter. I
wonder how pieces of it might affect jet engines or how it might feel
on a windy day to have to dodge chunks of the stuff.
Ken

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wrote:
[...]
Bottom line. Chemical rockets are not as bad as you mite think.

Yes they are bad. They may be the best we got, but they still suck.

Yeah, they do. Someone should hurry up and invent antigravity, quick.

I had a lot of hopes on the Woodward Effect --- this is the Mach's Principle
based theory that seems to predict that you can vary something's mass by
changing its energy density quickly --- but I haven't heard anything from
him for some time. Pity, because Woodward is actually a real scientist,
with, like, papers and everything. I know that someone discovered a flaw in
his experiment, and he was redesigning it, but I suspect the whole theory
didn't pan out.

The least weird-science way of cheaply getting to orbit seems to be one of
the space elevator variants. Alas, while they seem to be considerably
cheaper and easier to build than originally expected, I'm still going to be
lucky to see one in my lifetime.

- --
+- David Given --McQ-+ "You cannot truly appreciate _Atlas Shrugged_
| | until you have read it in the original Klingon."
| ) | --- Sea Wasp on r.a.sf.w
+- www.cowlark.com --+

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Of course the contrail shown has zero lateral or tensile strength.
Which is quite correct for the contrail of fuel patent you cited. Not
so for the lightweight aerogel. A true analysis would look at winds
aloft and determine the tensile strength needed to sustain a good
enough trail of fuel and oxidizer. Clearly (see below) with a 16 kPa
tensile strength, aerogels have sufficient strength to withstand
considerable wind shear for some period of time. Hydrogen and oxygen
will of course diffuse out of the gel over time, which will cause it to
sag as time goes on. Which means the trail must be used minutes after
it is in place. Rise times versus leakage times is an important
ratio...

Aerogel Specifications:
Apparent density: 0.001-0.35 g/cc
Internal surface area: 600-1000m2/g
% solids 0.07-15%
Mean pore diameters ~20 nm
Primary particle diameter 2-5 nm
index of refraction 1-1.05
Thermal tolerance to 500 C
Coefficient of thermal expansion 2-4x10-6
Poisson ratio 0.2
Young's modulus 106-107 N/m2
tensile strength 16 kPa
Fracture toughness 0.8 kPa*m0.5
Dielectric constant 1.1
Sound velocity through medium 100 m/s

bob wrote:

zoltan wrote:
I have an experimental air breathing engine that generates about 1 MW
of power in terms of
the heat output of the propane burnt. This engine has a 7 inch nozzle
and an Isp of 4000.

Jet engines are not rated in ISP, but fuel consumed per hour per unit
thrust. They need air.

Isp is the same quantity as specific consumption, but inverted, except that
it's usually measured in seconds rather than 1/hours.

Eg one pound of fuel per pound of thrust per hour is the same as an Isp of
one hour or 3600 seconds.

And 4,000 s Isp is 0.9 pound of fuel per pound of thrust per hour specific
consumption.

The presence of air doesn't affect that (although it's absence might


(I have no use for slugs or poundals)

--
Peter Fairbrother

William Mook wrote:

Of course the contrail shown has zero lateral or tensile strength.
Which is quite correct for the contrail of fuel patent you cited. Not
so for the lightweight aerogel. A true analysis would look at winds
aloft and determine the tensile strength needed to sustain a good
enough trail of fuel and oxidizer. Clearly (see below) with a 16 kPa
tensile strength, aerogels have sufficient strength to withstand
considerable wind shear for some period of time. Hydrogen and oxygen
will of course diffuse out of the gel over time, which will cause it to
sag as time goes on. Which means the trail must be used minutes after
it is in place. Rise times versus leakage times is an important
ratio...



As the air pressure drops around the ascending aerogel "propellant
stick", the oxygen and hydrogen will leech out of the aerogel's
structure unless it is covered in some sort of impermeable membrane.
I still think there is going to be a problem regarding pre-ignition of
the aerogel propellant stick- one static discharge anywhere within it,
and your propellant supply gets turned into a giant fuel/air bomb.
The other problem is how the oxygen and hydrogen get put into the
aerogel in the first place; if this is to be done on the ground then
it's going to require some sort of filling building several miles in
length that can turn into the wind to release the filled aerogel
cylinder through its roof, or a non traversing building that can only
release in near dead calm conditions.
In either case the two gases are going to stratify within the stick in
fairly short order, with the hydrogen at the top.
Getting the stick properly aligned for the TAV to ascend through is
going to be a problem also; it must be aligned on the correct bearing
for the intended orbit, as well as be floating at the correct angle to
the horizontal for the intended ascent trajectory.
This implies that the stick must be under control of some sort, most
likely by being towed by an aircraft that attaches itself to the stick
after it floats out of its gas loading shed, and then pulls it skyward
to the intended altitude, trajectory, and ascent angle- probably at
quite a low speed to stay within the structural limits of the aerogel. A
helicopter of some sort sounds like a candidate for a tow aircraft,
although this is going to badly limit the total altitude it can achieve.
Pulling the stick through the air at even low speed is going to generate
terrific drag given its length, and you are going to need a huge
helicopter to even have a chance of moving and controlling it- something
along the lines of a Mil-26 "Halo".

Pat