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Small, cheap, reusable rocket launcher



 
 
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  #11  
Old August 13th 06, 04:12 PM posted to sci.space.tech
Andrew Nowicki
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Posts: 43
Default Small, cheap, reusable rocket launcher

dan wrote:

Back in the 50's when no one knew if spaceflight was even possible,
several tests were made with sounding rockets launched by balloon at
high altitude. However the payload capability of even very large
balloons declines at extreme altitude, and launching a large balloon is
tricky. Because of the long period climbing to launch altitude
cryogenic propellants were not practical. Ultimately it was not
possible to carry rockets capable of getting into orbit. A similar
problem will occur with rotorcraft.


It will not.

The helicopter can fly much faster than the balloon.
If it flies vertically at the rate of 33 meters per second,
it will reach the altitude of 30 kilometers in 15 minutes.
Liquid oxygen and liquid methane will not evaporate
in 15 minutes.

On the other hand, a fixed-wing aircraft.i.e. the B-70, can indeed be
designed to carry a large payload at high altitude. While a large blunt
cone would have to much drag for external carriage on an aircraft, a
saucer-shaped vehicle could be carried and launched edge first and
re-enter flat side first; this is pretty much what Rutan's SpaceShip
One does with its pivoting tail. This can spread the heating over a
large area as with the Apollo Capsule, reducing thermal loads.


The airplane is superior to rocket as a means of transportation
through the troposphere because it is slower and much more
reusable. It is however not as slow as the helicopter, and
the separation of the rocket launcher and its cargo from the
airplane is tricky due to the aerodynamic drag.
  #12  
Old August 13th 06, 04:12 PM posted to sci.space.tech
Andrew Nowicki
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Posts: 43
Default Small, cheap, reusable rocket launcher

Andrew Nowicki wrote:

The problem is how to bring the balloon or the airship
back to the earth -- you would have to release lots of
expensive hydrogen.


Joe Strout wrote:

Why? Normal airships don't release lifting gas; they compress it, by
inflating internal bladders with air. I don't see why it should be any
different for this application.


I was not familiar with this technology, but it seems
that it may be troublesome to use it in a balloon or
an airship that reaches the altitude of 30 km. The
problem is that atmospheric pressure at the altitude
of 30 km is about 100 times lower than the sea level
pressure. You would need two bladders: one of them
would hold all the helium at the sea level, the other
would hold all the helium at the altitude of 30 km.
It takes lots of energy to pump all the helium from
the big bladder to the small one. Furthermore, as
you compress the helium by the factor of 100, it
heats up a lot, so you have to cool it. Thin air is
not a good coolant, so the cooling is slow. It would
be interesting to calculate how much time it would
take to compress and cool all the helium.

Andrew Nowicki wrote:

Leik N. Myrabo experimented with this idea some 20 years ago.
It works, and it is not very expensive. The microwave
electronics would cost about $100 per 1kg of the rocket weight.
(Batteries cost about $200 per 1kg of the rocket weight.)
I did not mention microwaves because the safety concerns would
drive up the cost.


Joe Strout wrote:

But they reduce the logistical issues. I wonder whether the safety
issues can be mitigated by careful selection of the wavelength used.


There is some info he
http://radsafe.berkeley.edu/nir1101c.html

The idea is not stupid, but it would take some effort
to develop this technology. Batteries are probably
less efficient, but they are easier to use.

Magnetrons are used to generate long microwaves. Low frequency
magnetrons are more efficient than high frequency magnetrons.
Microwave ovens have magnetrons which operate at a frequency
of 2.45 GHz and have efficiency of about 70%. Magnetrons
operating at 915 MHz frequency have efficiency of about 85%.
Magnetrons cost about $0.1/W.

Gyrotrons can produce short microwaves ( 3 mm) which are easy
to focus into a narrow beam, but their efficiency is low (15%-60%).
The maximum frequency is about 170 GHz. Gyrotrons cost about $1/W.

Atmospheric absorption of microwaves:
http://www.submm.caltech.edu/cso/weather/atplot.shtml
  #13  
Old August 17th 06, 09:20 PM posted to sci.space.tech
Herman Rubin
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Posts: 13
Default Small, cheap, reusable rocket launcher

In article ,
Andrew Nowicki wrote:
dan wrote:


Back in the 50's when no one knew if spaceflight was even possible,
several tests were made with sounding rockets launched by balloon at
high altitude. However the payload capability of even very large
balloons declines at extreme altitude, and launching a large balloon is
tricky. Because of the long period climbing to launch altitude
cryogenic propellants were not practical. Ultimately it was not
possible to carry rockets capable of getting into orbit. A similar
problem will occur with rotorcraft.


It will not.


The helicopter can fly much faster than the balloon.
If it flies vertically at the rate of 33 meters per second,
it will reach the altitude of 30 kilometers in 15 minutes.
Liquid oxygen and liquid methane will not evaporate
in 15 minutes.


I question whether that rate can be maintained at
high altitudes. Both an airplane and a helicopter
rely on air (or some other gas) for there to be
any power usable for lifting.

On the other hand, a fixed-wing aircraft.i.e. the B-70, can indeed be
designed to carry a large payload at high altitude. While a large blunt
cone would have to much drag for external carriage on an aircraft, a
saucer-shaped vehicle could be carried and launched edge first and
re-enter flat side first; this is pretty much what Rutan's SpaceShip
One does with its pivoting tail. This can spread the heating over a
large area as with the Apollo Capsule, reducing thermal loads.


The airplane is superior to rocket as a means of transportation
through the troposphere because it is slower and much more
reusable. It is however not as slow as the helicopter, and
the separation of the rocket launcher and its cargo from the
airplane is tricky due to the aerodynamic drag.


If it can reach 30 kilometers, the drag will be small.





--
This address is for information only. I do not claim that these views
are those of the Statistics Department or of Purdue University.
Herman Rubin, Department of Statistics, Purdue University
Phone: (765)494-6054 FAX: (765)494-0558
  #14  
Old August 21st 06, 08:43 AM posted to sci.space.tech
Mike Swift
external usenet poster
 
Posts: 8
Default Small, cheap, reusable rocket launcher

In article ,
Andrew Nowicki wrote:

dan wrote:

Back in the 50's when no one knew if spaceflight was even possible,
several tests were made with sounding rockets launched by balloon at
high altitude. However the payload capability of even very large
balloons declines at extreme altitude, and launching a large balloon is
tricky. Because of the long period climbing to launch altitude
cryogenic propellants were not practical. Ultimately it was not
possible to carry rockets capable of getting into orbit. A similar
problem will occur with rotorcraft.


It will not.

The helicopter can fly much faster than the balloon.
If it flies vertically at the rate of 33 meters per second,
it will reach the altitude of 30 kilometers in 15 minutes.
Liquid oxygen and liquid methane will not evaporate
in 15 minutes.

On the other hand, a fixed-wing aircraft.i.e. the B-70, can indeed be
designed to carry a large payload at high altitude. While a large blunt
cone would have to much drag for external carriage on an aircraft, a
saucer-shaped vehicle could be carried and launched edge first and
re-enter flat side first; this is pretty much what Rutan's SpaceShip
One does with its pivoting tail. This can spread the heating over a
large area as with the Apollo Capsule, reducing thermal loads.


The airplane is superior to rocket as a means of transportation
through the troposphere because it is slower and much more
reusable. It is however not as slow as the helicopter, and
the separation of the rocket launcher and its cargo from the
airplane is tricky due to the aerodynamic drag.


Andrew, the record altitude that a helicopter has flown with only a
pilot is 8,848 meters (29028 feet). To scale this up to a vehicle
capable of carrying a rocket of significant weight for say a 1000 kg
orbital payload would be akin to scaling up the Golden Gate Bridge to
span from San Francisco to Hawaii.

--
Mike

Some say we must tax corporations more. What they do not understand is that
corporations do not pay taxes. One of our governments conditions for their
existence is they collect the taxes from their customers and pass them to
the government.
Mike Swift
  #16  
Old August 22nd 06, 10:01 AM posted to sci.space.tech
[email protected]
external usenet poster
 
Posts: 18
Default Small, cheap, reusable rocket launcher


Damon Hill wrote:
wrote in news:1153423748.965872.310530
@i42g2000cwa.googlegroups.com:

As I understand it, helicopters are unable to rescue people off Mount
Everest, K2 or other mountains. It seems that the Pakistani army has
special helicopters that can go up over 6,000 metres.


A helicopter has recently landed on top of Everest, but I doubt it
had any payload beyond the pilot. I didn't think helicopters could
go that high myself.

http://www.greatoutdoors.com/publish...licopteronever
estmakeshistory/

--Damon


Quote:
"The remarkable Eurocopter flight breaks the World Record for the
highest altitude landing and take-off ever, for any flying machine on
Earth, and sets an undeniable milestone in the history of aviation."

I don't think this record will be beaten any time soon!

  #17  
Old August 23rd 06, 02:57 PM posted to sci.space.tech
Andrew Nowicki
external usenet poster
 
Posts: 43
Default Small, cheap, reusable rocket launcher

Andrew Nowicki wrote:

The helicopter can fly much faster than the balloon.
If it flies vertically at the rate of 33 meters per second,
it will reach the altitude of 30 kilometers in 15 minutes.
Liquid oxygen and liquid methane will not evaporate
in 15 minutes.


Herman Rubin wrote:

I question whether that rate can be maintained at
high altitudes. Both an airplane and a helicopter
rely on air (or some other gas) for there to be
any power usable for lifting.


The helicopter needs two sets of propellers/rorors:
small propellers used at low altitude and big
propellers used at high altitude.

Another option is to use two helicopters having
different size propellers: first stage helicopter
and second stage helicopter. If we choose this
option, there is no need to drop batteries on
the parachutes.

Andrew Nowicki wrote:

The airplane is superior to rocket as a means of transportation
through the troposphere because it is slower and much more
reusable. It is however not as slow as the helicopter, and
the separation of the rocket launcher and its cargo from the
airplane is tricky due to the aerodynamic drag.


Herman Rubin wrote:

If it can reach 30 kilometers, the drag will be small.


I disagree. The lift is constant regardless of altitude
because the airplane mass is constant. To keep the lift
constant you have to fly it faster at high altitude.
When you fly faster, you increase both lift and drag.
You can increase lift without increasing drag if you
have variable geometry wings -- they are common in
commercial aircraft. If you want to reduce cargo drag,
canard wings are probably better than variable geometry
wings. Both methods reduce the cargo drag, but not as
much as the helicopter with two sets of wings or the
two stages of the helicopters.

I guess you could try using two stages of airplanes: one
having small wings and propellers and the other having
big wings and propellers. Well... you still cannot
beat the helicopter, and dragging the big airplane
through the dense troposphere is a major nuisance.
It is easier to drag big helicopter propellers through
the dense troposphere than the big airplane wings
because the propellers are smaller than the wings.
Because they are smaller, the can be very flat and yet
lightweight. Flat things do not generate much drag.
Airplane wings cannot be flat because they are big
and because big flat wings would be too weak. This
fact is explained by the Cube-Square Law which states
that as scale is reduced, properties which are a function
of volume (mass) will decrease faster than those which
are a function of area (thrust and strength).
  #19  
Old August 24th 06, 11:16 PM posted to sci.space.tech
Andrew Nowicki
external usenet poster
 
Posts: 43
Default Small, cheap, reusable rocket launcher

Mike Swift wrote:

Andrew, the record altitude that a helicopter has flown with only a
pilot is 8,848 meters (29028 feet). To scale this up to a vehicle
capable of carrying a rocket of significant weight for say a 1000 kg
orbital payload would be akin to scaling up the Golden Gate Bridge to
span from San Francisco to Hawaii.


Apparently you have not read the first
post of this thread.

The helicopters cannot fly above the altitude
of 8,848 meters because their internal
combustion engines choke in the thin air.
If you replace the engines with electric
motors and replace small rotors/propellers
with big ones, they can fly much higher.
  #20  
Old August 26th 06, 09:17 PM posted to sci.space.tech
Herman Rubin
external usenet poster
 
Posts: 13
Default Small, cheap, reusable rocket launcher

In article ,
Andrew Nowicki wrote:
Andrew Nowicki wrote:


The helicopter can fly much faster than the balloon.
If it flies vertically at the rate of 33 meters per second,
it will reach the altitude of 30 kilometers in 15 minutes.
Liquid oxygen and liquid methane will not evaporate
in 15 minutes.


Herman Rubin wrote:


I question whether that rate can be maintained at
high altitudes. Both an airplane and a helicopter
rely on air (or some other gas) for there to be
any power usable for lifting.


The helicopter needs two sets of propellers/rorors:
small propellers used at low altitude and big
propellers used at high altitude.


Another option is to use two helicopters having
different size propellers: first stage helicopter
and second stage helicopter. If we choose this
option, there is no need to drop batteries on
the parachutes.


Andrew Nowicki wrote:


The airplane is superior to rocket as a means of transportation
through the troposphere because it is slower and much more
reusable. It is however not as slow as the helicopter, and
the separation of the rocket launcher and its cargo from the
airplane is tricky due to the aerodynamic drag.


Herman Rubin wrote:


If it can reach 30 kilometers, the drag will be small.


I disagree. The lift is constant regardless of altitude
because the airplane mass is constant.


This would be the case if the air density was constant.
But it is not; the lift decreases with the density of
the surrounding medium, and becomes 0 when there is no
density outside.

To keep the lift
constant you have to fly it faster at high altitude.


This is because of decreased pressure.

Present military aircraft may reach somewhat more
than 10 km, maybe 15. But at this altitude, air
pressure decreases rapidly relatively. I doubt
that fuel-only aircraft can reach 30 km.

--
This address is for information only. I do not claim that these views
are those of the Statistics Department or of Purdue University.
Herman Rubin, Department of Statistics, Purdue University
Phone: (765)494-6054 FAX: (765)494-0558
 




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