Would a space vacuum jet produce thrust?

[Spacescifi]

10 minutes ago, Dale Christopher said:

The “compressing” of spacetime would basically create a gravity well, I’d imagine. Expelling it out of the rear is probably a bad way of looking at it, since you are creating a gravitational pull at the point of compression and once space left whatever environment that was causing it to contract it would return to normal. The gravitational pull wouldn’t pull you in a certain direction though... it would only be like artificially changing your center of mass and then once out of the area of effect the gravitational effect would be gone. 

Pinching space at one end of a craft and moving that through/past the craft to the rear where it becomes unpinched, should be virtually the same as moving a mass from the front to the rear and expelling it. I’d imagine you’d get translational momentum in a similar way to how the rotation of a reaction wheel gives you rotational momentum.

If you looked at it like that you wouldn’t need a big pinch either. The gravity well of 1000kg is imperceptibly small however moving a mass that size from the front of a craft and out the rear would transfer a decent amount of momentum to the craft in the opposite direction. 

It wouldn’t be a jet engine, more a caterpillar drive like in The Hunt for Red October XD

 

Weird.

So originally I had a saucer design. You are telling me that if I place the engines antywhere on the hull of my ship and turn them on, they will become artifical gravity wells? Gravity is omnidirectional too.

Awesome! Never thought of that.

Might need g-force dampeners after all, since this only adds to the g-load of normal acceleration.

 

[Guest]

I’m speaking as though the distortion of spacetime gives gravitational effects directly without mass. I’d imagine it would, but I duno and I also duno the mechanic behind how you would be manipulating it. If it was via the application of buttloads of energy... well it would be literal mass I guess so no need to speculate. 

[Spacescifi]

7 minutes ago, Dale Christopher said:

I’m speaking as though the distortion of spacetime gives gravitational effects directly without mass. I’d imagine it would, but I duno and I also duno the mechanic behind how you would be manipulating it. If it was via the application of buttloads of energy... well it would be literal mass I guess so no need to speculate. 

Energy is mass and mass is energy.

So yeah. That works for me.

 

[YNM]

5 hours ago, Spacescifi said:

My idea literally compresses space vacuum like air and expels it out the back for forward acceleration.

Alcubierre drive does that too. Extreme "compression" at front (gravity well), extreme "expansion" in the back (reverse gravity well, which needs negative mass, and is the single biggest PITA for it).

Edited July 8, 2019 by YNM

[Guest]

24 minutes ago, YNM said:

Alcubierre drive does that too. Extreme "compression" at front (gravity well), extreme "expansion" in the back (reverse gravity well, which needs negative mass, and is the single biggest PITA for it).

It’s not really the same as what he is talking about. He is talking about his spaceship being propelled by a jet of spacetime out the back. Warp drive is essentially a ripple travelling through space which the craft rides inside.

[Guest]

There are some ideas based on Casimir effect and quantum vacuum, but they're incredibly speculative. Before it was debunked, a lot of those were postulated as a possible explanation for the EmDrive.

[YNM]

2 hours ago, Dale Christopher said:

He is talking about his spaceship being propelled by a jet of spacetime out the back.

Technically that's how you'd see the surrounding spacetime from the internal spacetime of an Alcubierre Drive.

Same with how a jet plane at crusing speed spews air at only a bit faster speed wrt the surrounding air, but the plane is moving much, much faster. If you have huge difference between the two, your propulsion system is not very efficient (see turbojet vs. turbofan).

Spacetime cannot be compressed at one end without relaxing the other. And also you have to consider the fact your ship do occupy spacetime... and if what you're doing is just to the local spacetime, you're just a lump of mass, not doing anything useful.

Edited July 9, 2019 by YNM

[kerbiloid]

Without an absolute coordinate system or a global universal object identifier, what is "here", "now", "position", and other absolute categories?

[YNM]

9 hours ago, kerbiloid said:

Without an absolute coordinate system or a global universal object identifier

You're right, there isn't one.

[StrandedonEarth]

13 hours ago, kerbiloid said:

Without an absolute coordinate system or a global universal object identifier, what is "here", "now", "position", and other absolute categories?

Well, position is generally given as relative to a fixed, agreed-upon reference point. That could be ten leagues due west of the peak of Mt Everest, but that would be next to meaningless. At one time,IIRC, the French used Paris as their Prime Meridian, in competition with Greenwich. 

For galactic navigation, while Earth or Sol would be logical reference points, they revolve around the galactic core, so the core would be the best choice.