Novel methods for propelling a rocket

Discussion in 'Physics & Math' started by Rocket Paul, Sep 23, 2017.

1. Rocket PaulRegistered Member

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Why blast a rocket in to movement from the back when it can be done from the front, giving much more balance to the rocket structure.

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3. originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Seems like it would burn up the rocket.

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5. exchemistValued Senior Member

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You would have to either angle it, as here: https://en.wikipedia.org/wiki/Launch_escape_system , losing power via wasted lateral thrust, or else mount the rockets on gantries either side, which would need to be strong enough to transmit the thrust, adding a lot of weight.

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7. Rocket PaulRegistered Member

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Its great to see so many new propulsion concepts ready to be tried and tested, most of them can be combined with my concept.

For years magnetic propulsion systems have been flawed because Newton’s third law applies, I want to explain how we can overcome this by nullifying the reaction to a magnetic repulsion engine, although there are probably a few drives “engines” that we could use to power the magnetic system lets begin by using just one a plasma drive.

If we use a rocket ship and had a fixed magnet at the front of the ship and a fixed magnet at the back of the ship and try and use the repelling force of the magnets to move the ship in to motion then nothing happens because they cancel each other out action and reaction.

If we make the repelling magnet at the back of the ship free moving on guide rails attached to a plasma drive then the plasma drive can thrust forward along the guide rails towards the fixed magnet at the front of the ship and push the ship in to motion with the combination of the free moving plasma drive and free moving magnet repelling against the fixed magnet at the front, with the now repelling magnets fixed magnet action and free moving magnet cancelling any reaction against the ship as its held in place by the free moving plasma drive we can now build up momentum with the repelling magnets.

Not only could we achieve possible light speed but a huge saving on any fuel would be made, for example if we put the same method to work with rocket ships we use today, by being able to thrust from the front the rocket it would be much more stable and controllable and you can escape earths gravity at a much slower speed, you can try this by holding a pencil on the tip of your finger and try and push it upwards and the faster you move your finger the easier it is to keep the pencil stable, but by pushing from the front if you had a hole in the pencil to do this then it becomes no problem at any speed.

8. exchemistValued Senior Member

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This is ballocks.

By the law of conservation of momentum, you cannot increase the momentum of the spacecraft unless you cause the momentum of some other mass to change by an equal and opposite amount, thereby conserving the total. The force on the spacecraft is given by the rate of change of momentum of that mass: d/dt (mv) = ma = F.

This is why all drives expel a stream of mass in the opposite direction to the direction in which the momentum of the spacecraft increases. You cannot get away from that, any more than you can pull yourself up by your own bootstraps.

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9. sideshowbobSorry, wrong number.Valued Senior Member

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I think Wile E. Coyote tried that.

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10. DaveC426913Valued Senior Member

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I have reported this thread to request it be split off to its own thread starting at post 12.
If the opening thread is not exhausted, we should probably wait for that, to continue this discussion, so as not to carry this further off the rails.

Or, more relevantly, attaching a fan to the stern of a sailboat.

RP is new, and is exploring Newton's Laws in relation to propulsion. It's a common enough error. He'll get it eventually, he just needs some guidance to get there.

11. NotEinsteinValued Senior Member

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I'm quite saddened by the fact everyone learns of the Newton way of looking at things, but not the Lagrangian way.

12. exchemistValued Senior Member

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Yes you have a point. I certainly never learnt the Lagrangian approach and I now wish I had.

13. NotEinsteinValued Senior Member

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It's never to late to learn!

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14. Rocket PaulRegistered Member

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Guys thank you for your replies....
I think we are going away from the main subject on how to push a rocket from the front, lets do away with the magnets for now and do the theory without them.

If we had a rocket inside a larger outer skin and thrust the rocket up some guide rails between front and back and between skins and a long tail pipe sticking out the back of both skins then once the rocket applies force to the front of the outer skin the whole thing will move just like a rocket moves today, but now we have pushed the rocket from the front as long as there is no force on the guide rails, before we say the passengers are incinerated all cargo is joined at the front. all be it we have lost the magnetic cushion or spring if you like at the front for when both skins come together. the whole craft is no longer top heavy as its now lifted from the top and yes flames and smoke coming out the back tailpipe, a simple test for this is to send a firework rocket up in to the sky with an outer cardboard cover.

15. NotEinsteinValued Senior Member

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I'm having trouble visualizing what you are describing; a picture or diagram would be very helpful.

16. DaveC426913Valued Senior Member

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OK. I see what he's saying.

Ignore the rails; they serve no function.

Ingredients: a pickle jar (empty), swim trunks (full), a backyard pool (any size), little green army men to-taste.
1. Glue little green army men to the outside of the pickle jar.
2. Take the S.S. Dillhole into your pool.
3. Put your hand on the open mouth and push the jar through the water bottom-first. It will flip over because you're pushing from the back.
4. Now, stick your fist all the way inside the pickle jar and push on its bottom. It will not flip. It is self-stabilizing because you're pushing from the front, in the hollow.
1.5 Put on swim trunks!! Oh God put on the swim trunks! The children!

Rocket Paul, what makes you think that rockets are prone to veering off-course?
What existing problem does your idea attempt to solve?

And at what cost?
You've doubled the diameter of the rocket,
You've got combustion, exhaust and lots of heat against the entire inner surface of the payload, with resultant friction (loss of propulsion) and destruction and transfer of heat to the payload.
And now you can't turn the nozzle to steer.
And if anything goes awry with the engine, you are guaranteed to fricasee the payload from the inside out.

Last edited: Sep 24, 2017
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17. exchemistValued Senior Member

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There seems to be something quintessentially Canadian about this hilarious response...

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18. iceauraValued Senior Member

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That can work, on the same principles by which one tacks into the wind.
Not the most efficient way to do it.

btw: in a medium (water, air) that creates instability, pushing on the front from behind like that does not completely solve the stability problem. The pickle jar in the swimming pool trial can mislead, because the role of the length of guided, directed, arm (or whatever one is pushing with rather than one's pickles) is hidden - likewise the directional role of the wind, in sailboat thought models.

Otherwise, the rocket could be made stable simply by transferring the force of the rear mounted engine to the nose by an internal rigid rod - pushing on the nose from behind, directly.

To discover the issues involved, try paddling a canoe from the front on a calm day.

Last edited: Sep 24, 2017
19. sideshowbobSorry, wrong number.Valued Senior Member

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The old rockets were stabilized by a stick-tail. Didn't that have the effect of moving the center of gravity back behind the center of thrust?

The German V2 used graphite vanes to direct the exhaust stream for stabilization and steering. The Saturn 5 gimballed the whole engine for the same purposes.

Yes, there's always a trade-off between stability and maneuverability.

20. DaveC426913Valued Senior Member

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No it can't.
The fan, in pushing air forward, has the equal and opposite reaction of pushing the boat backward, cancelling out the air filling the sail. Net effect: zero.

That being said, there is a video out there on YouTube that shows all the ways it does not work. But it also shows that, in highly contrived circumstances, if you take advantage of the entrainment of air, it is possible in theory. But pretty sure that's not what you were talking bout.

21. iceauraValued Senior Member

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The trick is to aim the fan at an angle to the direction of travel, and angle the sail appropriately, so more back pressure than fore pressure is converted to side pressure on the keel. It's just like tacking into the wind.
(Vague trig allusion edited out)
Consider the limiting case in a keeled sailboat: the onboard fan is blowing directly sideways to the axis of the keel, right angle. If the sail is very slightly angled into that airstream, there would be forward acceleration, along the axis, proportional to the sine of that angle - right? But no back pressure at all, and side pressure (including rotational) movement blocked by the keel (key factor: much force for little speed, sideways through the water).
It can work, and it has been done. https://mythresults.com/blow-your-own-sail
(Note: they didn't even need a keel, getting some back pressure block not only from the hull configuration in the water but apparently from gravity afaik - the back pressure from the fan partly converted to rotational force around the travel axis, trying to tip the boat over. The key technique was to find a configuration - fan and sail placements, steering tricks - that balanced the rotational forces around the vertical axis).

Last edited: Sep 24, 2017
22. DaveC426913Valued Senior Member

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EehhhhOK. Granted.

23. James RJust this guy, you know?Staff Member

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With the fan on the sailboat setup, you still end up pushing air backwards if you want to drive the boat forward.

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