Author Topic: Sublimation process for deep space propulsion  (Read 15842 times)

Offline Paul451

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Re: Sublimation process for deep space propulsion
« Reply #20 on: 04/10/2020 08:58 pm »
I just thought about "SUBLIMATION METHOD" for deep space propulsion.
As per sketch if camphor solid heated then the vapor will be ejected  and a thrust will be created to propell the craft.
The camphor vapor will be again deposited on a surface to reuse again and again.
The deposited camphor can be reused several time and it is technically possible.
Now my question is that should this method will work to propel the spacecraft without spring??
Second if it doesn't work without a spring and if i use a spring then should it work  as the deposited camphor will work to stretch the spring after each 3 second(the vapor will be ejected after each 3 seconds) and the spring will again compressed, pushing the craft.

You have a main-body on the left and a plate on the right. The main body has a block of camphor. Nothing is moving.

Total momentum is zero units.

The main body ejects 1 unit of camphor towards the right, towards the plate, at 1 unit of velocity. Because of conservation of momentum, the main-body now moves to the left of screen with a momentum equal to 1 unit of camphor-velocity.

The momentum of the parts of the system are: Caphor - a momentum of 1 unit right. Main-body - a momentum of 1 unit left. Plate - zero units.

Total momentum is therefore 1 left + 1 right, which equals zero units.

The unit of camphor hits the plate and gets captured, transferring 100% of its momentum to the plate. Because of conservation of momentum, the combined plate+camphor now moves to the right of the screen with a momentum equal to 1 unit of camphor-velocity.

The momentum of the parts of the system are: Camphor+Plate combined - a momentum of 1 unit right. Main-body - a momentum of 1 unit left.

The total system has a momentum of 1 unit right + 1 unit left. Total momentum is therefore zero units.

A spring between the main-body and the plate is stretched apart. It slows the movement of the main-body and the plate, converting their momentum into stored energy. Because of Newton's third law, the spring doesn't have a directional preference. It can't slow one side only. It must affect both sides equally.

So the main-body and the plate are both brought to a rest, this is the maximum stretch available to the spring. At this moment, the main-body has zero momentum and the plate+camphor has zero momentum. The spring is storing energy equal to 2 momentum units, but the system has an actual total momentum of zero.

Now the spring contracts. It pulls both ends towards itself. Again, it doesn't have a directional preference, it can't pull on one side only, it must affect both sides equally. So the main-body now gains a momentum of 1 unit of camphor-velocity to the right. The plate+camphor 1 unit to the left. Total momentum, zero.

Eventually they smack back together, resetting the spring. Their momentum cancels each other, and we again have zero momentum. (The energy is converted to heat, vibration, noise, whatever.)

So what's changed? After everything comes to a rest, the only difference is that we've moved 1 unit of camphor from the left to the right. By conservation of momentum, we must have moved the main-body, plate, and spring, all 1 unit to the left. But the final velocity is zero.

Success! We've moved without any external force, and without expending any fuel. All we need to do is keep repeating this and we can go anywhere, one unit at a time!

So now we move the camphor back to its starting position... Ah. But hang on, if we move the camphor back to the left, then the whole process I've described above will happen again, but with the directions reversed.

Conservation of momentum means that if you move 1 unit of camphor back from right to left, you must have moved the main-body, plate, and spring, 1 unit from the left to the right. That will cancel out the original movement and put us right back where we started!

All we are doing is expending energy (heating and cooling the camphor) to move the centre of mass of the whole system back and forth between two points. The movement to the right must balance the movement to the left. So once the camphor is back where it started, so is everything else. No net movement in any direction.

 

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