Turbulent fluid flow in space
propulsion
Introduction.
This site is intended to present and promote a new method of propulsion
that permits spacecraft in micro-gravity environment to accelerate for extended
periods of time in order to obtain a very high velocity without expelling mass.
The technique is based on a ram mass assembly (RMA) contained in 1 or more
pressurized structures attached to the spacecraft.
Part 1: Presenting the idea, part 2: experimentations,
building a working model,
video of homemade working
model
Part 1 the problem.
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Fig 1 illustrates a typical spacecraft that has been propelled to
explore the solar system with a relative velocity of 15.5 Km/sec, even though
it is traveling at a very high relative (to us) velocity, it will take months
or years to arrive at its destination. The spacecraft can not increment its velocity without expelling mass,
and no matter how efficient its onboard engine is (Ion drives are
presently the most efficient option), its use is limited by the amount of
mass it can afford to carry for use as propellant. I present a simple method for acceleration the spacecraft without expelling mass explained in 9
illustrations (Fig 1 to Fig 9) |
Fig 1 |
In fig 2 we attach a pressurized structure, aluminum or composite cylinder
approximately 10m long with a diameter of 3m to the spacecraft, the structure
contains air (or other suitable fluid) at normal atmospheric pressure.
Fig 2
Inside the pressurized structure we have a “free floating” mass assembly
(let us say 100k ), as the spacecraft with the attached pressurize structure
have a relative velocity of 15.5 km/sec and the mass assembly has the same 15.5
km/sec velocity, to a observer the mass assembly is “floating” inside the
pressurized structure (Fig 3 and Fig 4.)
Fig 3
Fig 4
What we desire is to accelerate
the mass assembly in the +X direction until it reaches a velocity
relative to the spacecraft of V1 (for example 1m/s), we shall examine two
methods of accelerating the mass assembly.
Method 1, expelling 1 or more
steel balls.
We may accelerate the mass assembly in the +X direction by expelling
steel balls from the mass assembly in the –X direction, depending on the mass
of the steel balls, and the velocity they are expelled in the –X direction, it may
be necessary to expel more than 1 ball. (Fig 5)
Fig 5
When the mass assembly collides with the “forward” or +X direction of
the spacecraft (fig 6). It’s momentum in the +X direction according to the mass
(100k) and the relative velocity (1m/second) will give the spacecraft a forward
nudge incrementing the spacecraft’s relative velocity, but as soon as the steel
ball (or balls) collide with the “rear” or -X end of the spacecraft any forward
increase will be canceled, and this is true regardless the length of the
pressurized structure, we may double or triple the length, or shortened it, the
forward and backward collisions will always cancel out.
Fig 6
Method 2, accelerating the
mass assembly with counter-rotating propellers.
Another method of accelerating the 100k ram mass assembly is to replace
the “ball throwing mechanism” with a fan (with its power source included, more
on that later, for now we will just have batteries included in the fan), the
new ram mass assembly must also have a 100k mass.
The fan is composed of the electric motor (a), connecter to a pair of
counter rotating propellers (b), fig 7.
Fig 7
When we turn on the fan (fig 8), its counter rotating propellers will
blow air in the –X direction and will begin to move in the +X direction,
gaining relative velocity reaching the desired 1mps velocity just before
collision with the “forward” or +X direction of the spacecraft (fig 9). It’s
momentum in the +X direction according to the mass (100k) and the relative
velocity (1m/second) will give the spacecraft a forward nudge incrementing the
spacecraft’s relative velocity that is equal to the momentum obtained expelling
steel balls described in method 1.
Fig 8
Fig 9
But the force excreted on the “rear” or –X end of the spacecraft is not
equal to the force excreted by the 100k ram mass assembly against the “forward”
or +X end for various reasons:
Momentum is lost because
turbulent fluids in the described example are not as efficient as steel balls
to transfer momentum. Force is excreted not only at the –X end of the
pressurized structure but against the sides and even the forward section. (See
part 2)
The momentum that
is transferred to the –X end of the spacecraft (using method 2) by the fluid
not the same regardless of the length (D1+D2 in fig 4) of the pressurized
structure, it will decrease if elongated and enlarged if shortened. But the
momentum transferred using method 1 (steel balls) is the same regardless of the
length of the pressurized structure.
Part 2 contains a more
detailed presentation of the idea, plans for building a simple working model,
video of simple model working.
Plans of testing a working model in a 0g environment are being
considered for the first semester of 2009 (Zero Gravity Flights) we hope to
demonstrate we have a practical working idea.
Many may find the idea of a mechanism that is in apparent conflict with
law of conservation of momentum difficult to
digest, people that are smarter than me are attacking the problem, I hope they
comment on any conclusions they arrive at.
But consider:
Motion of matter is
absolute, since it exists independently of the system with respect to which it
is considered, and, at the same time, it is relative, since physical systems
move with respect to other physical systems; Matter moves in space and time,
and the properties of the measure of motion must not contradict the properties
of space and time; The scalar and vector measures of motions must be considered
components of one complex measure, which has an absolute nature but is
differently decomposed into components in different reference systems; The
principle of relativity enables one to determine the nature of the connection
between the components of the measure of motion of any physical system and its
velocity in an arbitrary inertial reference system. It also permits one to
introduce the concept of inert mass for any physical system, as a value
connecting the velocity and the measure of motion.
Using the behavior of
turbulent fluid flow in space propulsion.
Behavior of turbulent fluid
flow vs. laminar fluid flow
First we must establish than even in a closed system the force on a
surface produced by a jet of air (or other Newtonian
fluid ) decreases as the distance from the source increases. This is true
if the flow is turbulent
(fig 11).
We can easily explore the forces generated with the experimental setup
described in Fig
Using a simple spring scale (or other force measuring instrument) we
will confirm that more force is measured in the D1 distance (as near as
possible to the source, and decreases as we move to the D2, D3 and D4 (as far
as possible) position.
We can reach the same conclusion empirically simply by standing in front
of a fan inside a closed stadium, if we stand
You can also have a friend blow air to you face from across the room,
you will not feel it. But if he fires a paper dart with a Blowgun (tube)
you will feel it on your face
Fluid dynamics is generally more concerned with laminar flow, in the
laminar example the force does not necessarily decrease with distance (Fig 12).
In the previous stadium example, if a long tube is installed between the fan
and our face, we will feel more airflow.
Also remember that under turbulent flow conditions, Poiseuille’s Law
no longer applies (see Reynolds number)
< -X -
- - - - -
- - --
- - -
- - -
- - -
- - -
- - +X
>
Fig 10
Fig 11 turbulent flow.
Fig 12 laminar flow
Therefore we reaffirm that the force exerted by a turbulent flow
decreases as the distance from its source increases.
Freeing the fan-motor
assembly.
If the fan-motor assembly is installed on a free rolling platform (wheels),
it will accelerate in the +X direction gaining velocity in accordance to the
trust generative by the propeller (1) and mass of the
fan-motor assembly (Fig 13).
< -X
- - -
- - -
- - --
- - -
- - - - -
- - -
- - -
+X >
Fig 13
When the moving fan-motor assembly collides into the +X wall it is
simple to calculate the force generated by the “bump” in the +X direction for
we have the mass and velocity of the fan-motor assembly the instant it collides
with the wall (Fig 14).
F= (final velocity) x mass.
The force (F1) in the +X direction will always be the same if the final
velocity of the moving fan-motor assembly is the identical the instant of
collision.
- -
- - -
- - -
- - - +X >
Fig 14
We are accustomed to automatically assume that if a force F1 is
generated in a given direction (+X) inside a closed system, a equal force will
be excreted in the opposite (-X)
direction, for we are very habituated to think in mechanical terms (Fig
15).
Fig 15
In fig 15 we have a representation of the forces generated by expelling
a steel ball from the assembly.
The assembly’s position at rest is (a), when the ball is expelled from
the assembly, the ball and assembly travel in opposed directions eventually
colliding with the +X wall and the –X wall, the ball will collide with the –X
wall with the same force regardless if the –X wall is in the D1 position, the
D2 position, or positions D3 or D4, and the forces in the +X direction and –X
direction will always be equal.
But we have seen that a flow of air if given sufficient space to flow
turbulently does not exert the same force against a wall (surface) at any
distance, the force in the –X direction is less if the “wall” is in the D2
position than the D1 position, and decreases as even further in the D3 and D4
positions.
If the opposite (-X) wall is sufficiently distant the force created by
the turbulent air flow will be quite insignificant.
We can make the moveable assembly collide with the same force (F1) onto
the (+X) wall regardless of the distance between walls (D1, D2, D3 or D4) by
assuring it has the same velocity the instant it collides.
But the balancing force of the air flow will not be the same regardless
of distance form the source, we can diminish the force in the –X direction by
incrementing the length of the container, maintaining the force in the +X
direction creating a strong directional force within the system enclosed in the
container (Fig 16).
Fig 16
It is simple to construct an experimental assembly to recreate the
closed system experiment, you can find instruction on constructing a working
model with Legos here (//wjetech.50webs.com/howto1.htm)
and a video (at
http://www.youtube.com/watch?v=ssQOdouJp-U)
If you wish to
reproduce the experiment you will need a level table (not always easy), and a
platform for the vehicle that is as frictionless as possible for avoiding a
“false positive”.
A flat table with
dry-ice pucks (such as those used in physic demonstrations) is perfect.
A air-hockey table
may also be used but it may be necessary to argument the air pressure with a
secondary pump.
A sandwich of
roller bearings between two glass panels works very well.
In the following
video I simply used aluminum rails separated by aluminum tubes.
Note: In the video
the module is placed on aluminum rails separated by aluminum rollers (tubes)
this setup permits a near frictionless surface for recording the video,
unfortunately the rail assembly in not very visible on the video. A new video
is “in the works”.
Space Propulsion Application
Now we will evolve the “closed system propulsion method” as illustrated
in Fig 7 into a mechanism optimized to function in micro-gravity environment.
The motor assembly must now be connecter to a pair of counter rotating propellers
(Fig 8a) with reversible pitch (the designers will have to decide between
reversing the motor’s rotation, reversing the propeller’s pitch or a
gear-cultch system).
The propeller-motor assembly will be glided by rails (not shown) or
glided in its path by jets of compressed air.
Fig 17
The propeller-motor assembly will be contained in a pressurized
structure attached to the spacecraft we wish to propel, the dimensions (Fig 9)
must be such that distance D1 is sufficient to allow the propeller-motor
assembly to gain sufficient velocity to collide against the +X wall with the
required momentum, and distance D2 must be sufficient to allow the dispersal of
the –X momentum by the turbulence of the non-laminar airflow (Fig 10).
Fig 18
Fig 19
Fig 20
It may be possible to increase efficiency by enclosing the
propeller-motor assembly but allowing the air flow to return by the “edges” of
the container, (Fig 11) therefore it may be possible to obtain propulsion using
laminar flow but we have not tested this hypothesis.
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Cycle for generating trust |
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Cycle 0 When the spacecraft is in orbit we detach the fan assembly from its
docking mounts (not shown), floating freely inside the spacecrafts
pressurized structure. |
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Cycle 1 When we turn on the fan, its counter rotating propellers will blow air
in the –X direction and will begin to move (slowly at first) in the +X
direction. (effect on the spacecraft assembly negligible) |
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Cycle 2 The fan assembly will gain velocity as it travels in the +X direction. |
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Cycle 3 BUMP. The fan assembly will move in the +X direction until it bumps into the
spacecraft’s structure giving it a small push (fan assembly’s mass x velocity) in the +X direction. As the spacecraft is in space, it will keep the small increase in
velocity |
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Cycle 4 The instant of the “bump”, the propellers pitch is reversed, thrusting
the fan assembly in the –X direction. The air blown against the spacecraft’s structure is negligible, does
not increase spacecrafts velocity |
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Cycle 1 (again) At a pre-programmed distance (length of D1 Fig 4), the propellers
pitch is returned to its original position, generating wind in the –X
direction, slowing the fan assembly until it stops (relative to the velocity
of the pressurizes spacecraft structure) and begins acceleration in the +X
direction until it catches up with the spacecraft structure giving it another
bump, another increase in velocity the spacecraft will not lose. |
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Fig 21
Each cycle the spacecraft will increase velocity without expelling mass,
therefore if it is powered by a solar or atomic power plant it will continue
accelerating the spacecraft indefinitely
(as long as we can power the motor)
Indefinitely, (ad
infinitum?) That’s interesting.
Beyond the Propeller
It may be possible that for
some combinations of available power and spacecraft mass a propeller driven
spacecraft may be desirable, but for most applications it may be better to
replace the fan assembly (fig 8) with a ram mass assembly (RMSA),
described in fig 13.
Fig 22
Principal parts of the ram mass structure assembly RMSA.
- AIPS Air Independent
Power Supply (radioisotope thermoelectric generator or RTG Fig 14)
- Electric Motor
- Compressor fan
- Air ducts
- Air valve
- Air jet nozzle
Fig 23 Radioisotope thermoelectric generator (RTG). Image The Internet ENCYCLOPEDIA OF SCIENCE
In this example (Fig 13), we have 4 RTG power sources (5) included in
the ram mass structure assembly (RMSA), more than adequate to power the
electric motor (6), that will power the compressor fan (7), that will blow air
thru the air ducts (8), reaching the Air valves (9) that open and close expelling air thru
the forward or rear Air jet nozzles (10) that propel the RMSA in the
“forward” (+X) or “rear” (-X) direction.
Putting It All Together
Fig 24
In Fig 15 we have a spacecraft (1) that is propelled in space by a
Elliott Air Driven Space Propulsion System (2), inside the pressurize structure
(2) we can see the ram mass structure assembly RMSA (3) traveling in the +X
direction propelled by air jets, soon to bump into the forward contact area
(15) giving the spacecraft a small increment in velocity.
Note that the pressurized structure (2) has a forward (15) and rear (14)
contact area, therefore the mechanism can create forward and backwards impulse.
If instead of using just one Elliott Air Driven Space Propulsion System,
we use three or more (Fig 9), we may also maneuver the spacecraft by
synchronizing the movements of the various RMSAs
Fig 25
Continuously accelerating spacecraft to never before velocities? Am I
serious?
Yes.
Does it work?
Yup.
Interested?
Send mail to wjetech@gmail.com to
receive updates. (Or contribute?)
Adventures
souls can see the instructions to build a working model at http://wjetech.50webs.com/howto1.htm
You can see
a video of a simpler to make demo model at
http://www.youtube.com/watch?v=ssQOdouJp-U
(1) The details of how a
propeller generates thrust are
complex, but the fundamentals using the simplified momentum theory presented
here. http://www.grc.nasa.gov/WWW/K-12/airplane/propth.html