WJETech (we push from the inside)



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Extending satellites useful life (positioning)

(Beyond “all electric” satellites)

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The importance of extending a satellite’s usefulness is quite straightforward, satellites are very expensive.


A satellite can cost around US$ 300 million (spy satellites are often more expensive) and US$ 80 million to US$ 400 million to place in orbit, therefore prolonging the satellite’s useful life increases chance of a reasonable return on the investment.




Satellites (especially spy satellites) occasionally need to modify their position, they do this by using small thrusters (Fig 1) that use fuel/propellant, when the propellant tank is empty the satellite is stuck in its position and cannot make even minor corrections necessary for operation.


Many newer (so called “all electric satellites”) use electrical thrusters (ion or others Fig 2) that offer LESS thrust but a greater fuel efficiency permitting a longer useful life.


We offer the use of fluid thrusters (Fig 3) that create more thrust (28 millinewtons) than most ion drives and longer useful life as it does not expel propellant.



Many persons still mistakenly believe that it is not possible for a closed box to accelerate by pushing itself from the inside, please see http://wjetech.cl/ex102017.htm where a simple DIY test/demonstration is described.


Simplified description of the propulsion method.

(Full description of the propulsion method)


We have two (or more) rounded cylinders of inflated air bags (balloons) 1.1 meter diameter and 2.6 meters of length attached to the satellite via extendable arms.

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Fig 4


This gives us a volume of 2.1 cubic meters of air composed of 54 septillion fast moving (500m/s) molecules constantly colliding with other molecules and the contender’s inner wall (just normal air).

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Inside on the forward (+X) end of the inflated airbags there is a motorized propeller attached to the airbags inner structure and therefore the satellite.

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Fig 7: When an air molecule is hit by a blade of the spinning propeller the collision exerts a force (F1) against the molecule that accelerates the molecule in approximate –X direction.


As for every force there is an equal and opposite force (F2), the propeller receives the same force but in the +X direction (Fig 8).


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Fig 9


As the propeller spins, every collision gives it a push in the +X direction, the sum of those pushes exert a force in the +X direction transmitted to the spacecraft via the positioning shaft (fig 9)


the molecules that have been accelerated in the rear direction do not reach the air bag’s rear surfaces directly, they collide with other air molecules randomizing their vectors (see kinetic theory of gases) so part of the force the propeller exerted on the air molecules will be diverted towards all the inner walls, not just the rear wall (fig 9).

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As the force on the propeller, motor, positioning shaft in the +X direction is larger than the –X force exerted on the rear end of the airbag (again this can be observed a confirmed here) a useful force is generated in the +X direction (Fig 11).


Remember this is a simplified description of what is observed directly (airtight box accelerates) in various experiments (see here, here, here and here ).


To summarize we have 3 methods of exerting thrust (push) on a satellite


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With the advantage going to the Fluid Drive, this is especially true when it comes to reconnaissance satellites


For more information see http://wjetech.cl/