Is There A Way In Physics To Push Off Vacuum?

[Spacescifi]

 

I ask because if there is or if there was, it would beat the whole tyranny of the rocket equation?

 

If there is no conceivable way you can think of in physics that's fine.

 

Just wondering if there is a possible way... and if not, it will be purely scifi wish fulfillment.

 

Even if there was a way I am betting the drive would have a speed limit based on overheating.

Since for every action there is a reaction, and if the drive is reacting off space itself...

 

Discuss?

[Terwin]

Closest thing I can think of would be the Alcubierre drive.(the one that stretches space behind you and squeezes it in front of you to move your location instead of moving your vessel)

Only problem is we need some sort of 'negative mass' to make it work. 

[p1t1o]

15 minutes ago, Spacescifi said:

 

I ask because if there is or if there was, it would beat the whole tyranny of the rocket equation?

 

If there is no conceivable way you can think of in physics that's fine.

 

Just wondering if there is a possible way... and if not, it will be purely scifi wish fulfillment.

 

Even if there was a way I am betting the drive would have a speed limit based on overheating.

Since for every action there is a reaction, and if the drive is reacting off space itself...

 

Discuss?

There has been some research and surprising results with some kinds of "reactionless" "drives" ("Q drives" "EmDrive", they all sound and look similar) that appear under some circumstances to generate milli-Newton or micro-Newton thrusts, without the application of any propellant or reactionary force.

However, the general consensus is approaching "this is bunk science" as nobody seems to be able to generate repeatable results that can be confirmed not to be simple noise.

 

Short answer - no it isnt possible

Long answer - the current total of human knowledge still has gaps, but we havent found a way yet

[sevenperforce]

Nope, you can't push off a vacuum. You can push off of a local electromagnetic field, though.

[Spacescifi]

56 minutes ago, sevenperforce said:

Nope, you can't push off a vacuum. You can push off of a local electromagnetic field, though.

Interesting. Space don't have a lot of concetrated EM fields without a source of mass.

Space has a lot of EM waves (radiation), but I am not sure that can be converted into momentum without a lot of focusing mirrors and large sails plus a lot of time.

 

So whatever ship could pull off the OP without infrastructure would be freakishly powerful.

 

[Guest]

21 minutes ago, Spacescifi said:

Space has a lot of EM waves (radiation), but I am not sure that can be converted into momentum without a lot of focusing mirrors and large sails plus a lot of time.

Sails are totally feasible. There are some craft out there with them right now.

[Bill Phil]

 This may be possible in an absolute sense but you don’t escape the rocket equation.

The rocket equation can be converted to be a function of energy ratio and specific impulse - but in terms of impulse per unit energy. This creates a problem - you still have something similar to a rocket, essentially. The propellant isn’t internal though. But the energy used is.

Edited February 24, 2020 by Bill Phil

[Spacescifi]

2 hours ago, Bill Phil said:

 This may be possible in an absolute sense but you don’t escape the rocket equation.

The rocket equation can be converted to be a function of energy ratio and specific impulse - but in terms of impulse per unit energy. This creates a problem - you still have something similar to a rocket, essentially. The propellant isn’t internal though. But the energy used is.

 

I see. So even if we had a form of propulsion without propellant the question becomes what kind of reactor is providing you power and how efficient is it?

Taking a modern example...

 

 

A nuclear sub. 

 

Using nuclear reactor to power a vacuum reaction drive. Absurd I know, but it is just an example of the concept.

 

Nuclear subs do not have the greatedt TWR, even if they had no water to run against and used space instead. Could not even make orbit.

Antimatter reactors maybe work with OP drive.

[wumpus]

Back in the 90s there was some claim that a nanotech device managed to use the EM background radiation as a power source.  Unfortunately it only managed to push a piston in a single direction and couldn't drive it the other way.  I'm not even sure that thermodynamics allowed that much, but nobody was hoping for more than a localized nanotech power supply, and a weak one at that (think "solar" energy from 3K radiation).

1 hour ago, Spacescifi said:

Could not even make orbit

If you are limiting yourself to Earth's orbit you don't have to bother with vacuum.  There is an abundant magnetic field that physics allows you to push against.

At least one spacecraft has used it, although it was more of a proof of concept than an effective choice.

[Spacescifi]

18 minutes ago, wumpus said:

Back in the 90s there was some claim that a nanotech device managed to use the EM background radiation as a power source.  Unfortunately it only managed to push a piston in a single direction and couldn't drive it the other way.  I'm not even sure that thermodynamics allowed that much, but nobody was hoping for more than a localized nanotech power supply, and a weak one at that (think "solar" energy from 3K radiation).

If you are limiting yourself to Earth's orbit you don't have to bother with vacuum.  There is an abundant magnetic field that physics allows you to push against.

At least one spacecraft has used it, although it was more of a proof of concept than an effective choice.

 

Magnetic fields eh?

 

I only wish this happened, but the current state of affairs and physics would make it nigh impossible.

 

Gravity is tough. For being the supposedly the weakest of the four fundamental forces it is more influential and more obvious than most.

https://m.youtube.com/watch?v=FLujoeWx0RE

Edited February 25, 2020 by Spacescifi

[wumpus]

1 hour ago, Spacescifi said:

Magnetic fields eh?

I only wish this happened, but the current state of affairs and physics would make it nigh impossible.

https://m.youtube.com/watch?v=FLujoeWx0RE

I only said they were bountiful.  Not necessarily strong enough for whatever you want, but certainly there.  And far, far, easier to manipulate than vacuum.  But slowly changing orbits has been shown to work.

[StrandedonEarth]

10 hours ago, p1t1o said:

There has been some research and surprising results with some kinds of "reactionless" "drives" ("Q drives" "EmDrive", they all sound and look similar) that appear under some circumstances to generate milli-Newton or micro-Newton thrusts, without the application of any propellant or reactionary force.

I believe proper testing showed that previous tests didn't account for EM reactions against the power cables. So yeah, debunked.

But while photon drives are possible, the power-to-thrust ratio is ludicrous

Edited February 25, 2020 by StrandedonEarth

[K^2]

Absolutely. You pick your favorite boson field, preferably one with a zero rest mass. Then you polarize the vacuum in that field, flip the polarization, and repel from vacuum. Easy. For example, lets pick electromagnetic field. Vacuum is a dielectric, so you can apply electric polarization. Start alternating the electric field in your generator, and you will get a reaction force propelling the craft forward. Of course, you'll be producing electromagnetic waves, but you have to have something carry away momentum, so that makes perfect sense. Congratulations, you just invented a photon drive, AKA, pushing yourself with a flashlight. It has best-in-class I_SP of over 30,000,000s, or nearly 100,000x better than kerlox! The only problem is that it does take a bit of power. 300MW per 1N of thrust, to be specific. So you better bring some matter/anti-matter fuel or a black hole to power this thing.

There's a reason why we don't discuss propellant-less thrusters outside of science fiction topics. Energy-momentum is a conserved current, which means you either bring mass to propel yourself with, or you waste an enormous amount of energy to stand in for that mass. Anything else violates the most fundamental of underlying principles - local symmetries. You can think of it as being geometrically impossible to do better than this.

That said, there are ideas out there that involve moving yourself places without actually accelerating. Warp drives, wormholes, etc. Sadly, nobody figured out yet how to do any of this without negative energy densities and enormous amounts of ordinary energy. A black hole drive is way more realistic at this point, and that's all that needs to be said on the matter.

[kerbiloid]

Yes, it is.

Every time when you push off a gas jet, you are also pushing off the vacuum between the gas atoms. Use the jet, push the vacuum.

Actually, the answer depends on your definition of the "vacuum".

Edited February 25, 2020 by kerbiloid

[Starman4308]

The primary alternative is ISRU: In Situ Resource Utilization, ranging from fairly plausible concepts (Sabatier reaction, CO reverse fuel cells) to not-yet-known-feasible (Bussard ramjet).

Other than that: you're at the mercy of relying on external magnetic fields (very weak until you get very close to large objects), photon drives (which require inordinate amounts of power), and stored reaction mass (looping right back around to the rocket equation).

[p1t1o]

4 hours ago, kerbiloid said:

Yes, it is.

Every time when you push off a gas jet, you are also pushing off the vacuum between the gas atoms. Use the jet, push the vacuum.

Actually, the answer depends on your definition of the "vacuum".

Oooh, nooo. You're pushing off the molecule-molecule electrostatic repulsion and against their inertia.

Though probably one school of of thought would say that inertia itself is how objects are "attached to space" so simply by using reaction mass, you are "pushing against vacuum" just that the tool you are using to "grip" space is mass.

And another might suggest that EM fields and waves are constructed from the intrinsic structure of spacetime, so electrostatic repulsion itself is mediated by the structure of the universe (not wave/particle/photons travelling through space, more like waves travelling over the surface of a lake. The [lake]wave is not an object, the [lake]wave is the effect of energy on the underlying substrate [water])

Indeed, even physical "particles" may be simply a figment of the underlying structure of spacetime, in this scheme, there is no "space with objects in it" there is only one object, the universe, and matter is simply a shifting pattern on its surface, not seperate, discretely interacting entities. Which negates the question entirely.

 

 

And this is how Physics starts to approach philosophy when you take it so far down the rabbithole that you are approaching the structure of existence itself, when you start to draw links between physics and the nature of "being". Dont even get started on "free will" and physical determinism...

Edited February 25, 2020 by p1t1o

[kerbiloid]

As I said, it depends on the definition of vacuum which the OP means, what does it include (say, fields) and what doesn't.

The existence of the "vacuum" also depends on it. Continuity of matter and so on.

Edited February 25, 2020 by kerbiloid