Rotational Slingshot Catapult (RSC)
- Đ Frank Ellinghaus -
catapult propulsion -
speed lever -
force lever -
Mini STS -
Micro STS -
Fig. 7 - N E W on June 27/2003 in red colour
Through using simple lever rules, an advantageous weight distribution and the fact that the shooted probe doesnīt have to carry itīs own fuel, small lightweight probes could reach now considerable higher speeds with rotational catapult propulsion than direct driven space crafts.
That means we donīt have to develop new sorts of thrusters (such as the vasimir drive) to go faster. Just using what we have now would do it. This mechanical way to enhance speed works like car gears, were the gear is the speed lever.
The Rotational Slingshot Catapult is a giant thruster powered light weight carbon fibre ring with carbon fibre belts and a center propulsion unit to cause rotation which is able to shoot spacecraft and material with high speeds through space. A space transporter which doesnīt leave his place when transporting.
What would it be good for? For instance throwing a flyby probe outside of our sun system with conventional chemical fuel, something we couldnīt do with this sort of propulsion when the probe would be direct driven.
The point is, that the probe doesnīt have to accelerate the fuel. And the catapult has only to accelerate the fuel located in itīs center between the thruster units hence saving force in contrast to direct acceleration of this mass. The saved force can now be used to accelerate the probe and the lightweight pipe ring using a speed lever which can be choosen freely through the distance to the driving center thrusters (until the craft crashes through the centrifugal force).
To give an example: The center tank unit with the center of mass at 0,33 (the thruster-units would be located at 1,00) could weight about 360 to. The catapult would only need the force for 120 tons to rotate it. 240 tons of fuel could be used to propel the outer ring and the probe weighting about 100 kg (the probe 10 kg and the ring 90 kg). Choosing a speed lever of say 20 - which speed could the probe reach using standard chemical thrusters at the catapult until the 360 tons of fuel are exhausted?
Do your own calculation and please tell me, what you got out of it. I would like to put the outcome onto this site.
Using this lever we could even bring steam propulsion driven by water prospected at asteroids to further use, reducing the cost of such type of transports by orders of magnitude (see neofuel.comīs article on steam rockets).
Catapult propulsion
This rotating disk accelerates itīs rotation until it has reached the wished cruising speed for the object which is to be catapulted. Then it decelerates a bit releases the object from the brackets and holding sling at the outer ring and lets it take itīs straight way towards the destination.
While using a speed lever to throw an object the RSC also uses a force lever to minimize the force needed to accelerate the heavier center parts of the craft.
Distinguishing features of the construction is the carbon pipe ring with carbon belts (RSS) to hold the ring and itīs weight placement, - heavy parts to the center, ultra light carbon parts outside and itīs lever-usage as mentioned above.
While the object is mounted onto brackets with a sling on the outside of the enfolding ring, the driving thrusters are mounted near the crafts center thus achieving a speed lever.
The biggest mass, the fuel tank and all the heavier parts which can be placed there are mounted between the main thrusters at the center providing the force lever and center mass.
The craft needs less force to rotate the heavy center parts than would be needed to drive them into a straight direction without the force lever. It needs more force to rotate the outer lightweight parts than would be needed to accelerate them without the speed lever.
For a speed lever of 20 - 20 times the force is needed to get the outer ring moving. Therefore it is essential to get those outer parts as light as possible.
In addition and because of the force lever used it is possible to employ conventional thruster systems as rotational thrusters since they need less force to rotate themself and their fuel at the crafts center.
The disadvantage of conventional thrusters their low speed is overcompensated through the speed lever!
With a speed lever of 20 the catapult propulsion driven object getīs 20 times the speed of the driving thrusters. The advantage the higher force of conventional propulsion is saved in part through the advantageous weight placement.
It would be a good idea, using rebuilt booster tanks of the space shuttle as the central tank and thruster unit which is also the catapults mass centrum. The outer lightweight ring would be fixed to it with strong carbon fibre belts.
When the Space Shuttle would transport the replacement tank units filled with fuel, it could take the used units back to fill it up again on earth. This would reduce costs through reusage of parts and avoid space cluttering with waste.
Speed lever
What does speed lever exactly mean in this case?
When the driving thrusters of the RSC, which are placed near the spacecrafts center do a full turn, the object which is to be catapulted of a bracket from the outer ring, covers a lot more of ground. For instance: We have a RSC of 100 m diameter, the thrusters are located 5 m away from the center. While they are covering only 15,7 m doing a full turn, the object on the outer ring covers 314 m in the same time.
In this case the slingshot object rotates 20 times as fast as the driving thrusters are rotating. This is what I call speed lever.
Weīll need 20 times as much force though but if we have thrust in abundance for instance when using chemical thrusters this should be a viable possibility to enhance the thruster speed for the catapulted object.
Force lever
What does force lever mean in this case?
If you have a screw driver with a handle bar, you know what I mean. Youīll need less force to drive the screw if you have a longer handle. If you have a similar tool with very big handles for both hands, one hand pushing, one hand pulling the force you can exercise is incredible. The same principle works for the RSC also. Two opposite thrusters one pushing one pulling replace the hands. All mass-particle with a shorter distance to the disk center than the driving thrusters need less force for acceleration because they have to do shorter distances as the thrusters.
Mini STS
The Mini STS is a little solar sail based on the Solar Thruster Sailor (STS) design steered with the help of ion thrusters. It getīs transported to itīs near sun orbit with the Rotational Slingshot Catapult (RSC). This craft could even land on asteroids with low gravitation using the ion thrusters in this case as main propulsion and the thruster brackets as landing feet.
How could a small solar sail work at all carrying relative heavy ion thrusters too? Shouldnīt it have a pretty big sail area because of the low force of the light pressure?
This is correct - in principle, but as you get nearer to the sun as stronger getīs the photonic force also. At 0,25 AU this force should be 16 fold stronger than at near earth position!
A solar sail of about 10 m diameter (about 78,5 square metre area) could gain the force of a 1256 square metre solar sail on near earth position. This would be considerable more than the area (and the force available) of the 30 m diameter Cosmos 1 solar sail of the Planetary Society, hopefully to be launched soon (written on Dec. 2002).
Building and launching such a lightweight STS to LEO would be a special offer compared with the costs (if possible at all) of missions to and around the sun with other propulsion technics. Planning and installing the Slingshot Catapult at LEO would be more demanding but this could be a one time investment for a multitude of cheap missions enabling a cluster installation of near sun satellites, with many fly by observations of venus and mercury.
In contrast to conventional satellites this Mini STS would be able to fully navigate for a long time, spiraling towards the sun through positive declination and changing direction spiraling away from the sun through negative declination. The ion thrusters would have to do just this one turn to steer the craft when changing direction hence staying functional for a long time of operation since they need only sparse fuel.
Micro STS
The Micro STS is a little solar sail based on the Solar Thruster Sailor (STS) design steered with the help of micro- or digital thrusters.
Since the lower weight of the thrusters would be substantial this solar sails could be even smaller than the Mini STS or they could move faster. Such small propulsion devices could be used in this case because they are only needed to turn the (ultra light) sail. Through weight placement (all heavier parts should be placed as near to the center as possible) and force lever (the steering propulsion devices move a large lever from the outer ring to the center) they are able to steer the craft.
Fig. 7 - RSC - Rotational Slingshot Catapult
Two double thruster units in the center for rotational propulsion, two thrusters mounted outside of the ring for directional propulsion.
This craft, a giant rotating disc with an outer ring from pipes can propel objects like satellites into straight tracks. It gets itīs shooting speed through the speed lever provided from thrusters mounted in the middle of the structure. When this thrusters rotate, points on the farer outside of the disc are moving with a much higher speed depending to the distance from the driving thrusters. An object placed on such an outside point unclasped from itīs brackets will move forward with the gained speed in a straight direction.
Placing one of them near Mars and one of them near earth could make transportation cheaper or using one to propell flyby probes could make missions possible, which are not, when the probes are direct driven.
RSC - German Page