Author Topic: Helical Engine  (Read 11191 times)

Offline Star One

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Offline meberbs

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Re: Helical Engine
« Reply #1 on: 10/12/2019 12:38 am »
It was also linked on the emDrive thread, but to keep things clean, better to use this new thread.
Something like Woodward and his team envisions but with a little twist.

Quote
Burns, David   (NASA Marshall Space Flight Center, Huntsville, AL, United States)
Abstract:   A new concept for in-space propulsion is proposed in which propellant is not ejected from the engine, but instead is captured to create a nearly infinite specific impulse. The engine accelerates ions confined in a loop to moderate relativistic speeds, and then varies their velocity to make slight changes to their mass. The engine then moves ions back and forth along the direction of travel to produce thrust. This in-space engine could be used for long-term satellite station-keeping without refueling. It could also propel spacecraft across interstellar distances, reaching close to the speed of light. The engine has no moving parts other than ions traveling in a vacuum line, trapped inside electric and magnetic fields.
Publication Date:   August 19, 2019
https://ntrs.nasa.gov/search.jsp?R=20190029657
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190029657.pdf

Shell

I am not sure exactly what they are claiming, but I think I worked out the source of the confusion.

At first I expected that this would be something that works by radiating photons, or maybe something with "hidden momentum" in electrodynamics. After looking at it closer I think there is just a simple misunderstanding of relativity. They state that since F = m*a, the z velocity would not change from a force in the x or y directions. That is simply wrong, because the better definition is F = dp/dt where p=momentum. For an object with velocity in the x and z directions, applying a force in the x direction increases the energy of the particle, increasing its relativistic mass. This therefore means the velocity of the particle in the z direction would decrease proportional to the additional mass to keep the z component of momentum constant. Basically this boils down to confusion about what happens in relativity when applying forces at angles, and they simply don't actually do the detailed calculations to point to a clear location for their mistake.

A classical analogy is if you drop a sack of flower onto the bed of a moving truck (ignore friction with the road etc.). The truck slows down despite there being no external force that you apply. That it because there is a force between the the sack and the truck as the sack starts at 0 velocity and friction with the truck causes it to accelerate. to match the truck velocity while the truck slows an equivalent amount. The extra relativistic mass is basically equivalent, having come from the source of the external force (not from nowhere) and initially not coming with any z momentum, so it needs to catch up by slowing the rest of the particle mass slightly in the z direction.

The presentation helpfully ends with the following, which is much preferable to the common absolute assertions that "this must work" often seen in propellantless propulsion papers.
Quote
•Basic concept is unproven
•Has not been reviewed by subject matter experts
•Math errors may exist!

Offline Star One

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Re: Helical Engine
« Reply #2 on: 10/12/2019 06:32 am »
I started a new thread as my interpretation of what was said in the article I posted was that he didn’t want it associated with something like the EM drive.

Offline Bob012345

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Re: Helical Engine
« Reply #3 on: 10/13/2019 09:55 pm »
Quote
•Basic concept is unproven
•Has not been reviewed by subject matter experts
•Math errors may exist!

I think this whole paper just amounts to "Hey, here's a neat idea that probably won't work but I thought of it first."
« Last Edit: 10/13/2019 09:57 pm by Bob012345 »

Offline bad_astra

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Re: Helical Engine
« Reply #4 on: 10/14/2019 06:52 am »
Quote
•Basic concept is unproven
•Has not been reviewed by subject matter experts
•Math errors may exist!

I think this whole paper just amounts to "Hey, here's a neat idea that probably won't work but I thought of it first."

It reads in places like a potus Tweet

"Basic concept is unproven•Has not been reviewed by subject matter experts•Math errors may exist!"

Yep, that's what you want to see in a public NASA paper written by the deputy of Space Systems Department, MSFC.
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Re: Helical Engine
« Reply #5 on: 10/14/2019 11:10 am »
Has he accounted for the mass of the energy?

If you have a self contained accelerator/decelerator system, the ions gain mass as they speed up and lose it as they slow down. But the energy to do that has to be stored in the system as well, so you're alternating between kinetic and other forms of it. Since the energy has mass of its own, which will be substantial, the overall system doesn't change its mass, so moving it back and forth doesn't generate a net thrust.

Offline mlorrey

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Re: Helical Engine
« Reply #6 on: 10/14/2019 07:08 pm »
This is just Burns trying to coopt Woodward's Mach Effect theory and his thruster tech, and apply his own  theory to it so he can slap his name on it.
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Offline meberbs

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Re: Helical Engine
« Reply #7 on: 10/14/2019 07:18 pm »
This is just Burns trying to coopt Woodward's Mach Effect theory and his thruster tech, and apply his own  theory to it so he can slap his name on it.
No, this has literally nothing to do with Mach effects.

Also, you just finished telling people off in the other thread for daring to refer to it as Woodward's effect, and now you do so yourself, giving the possession to him. (Which isn't actually wrong, the issue is you giving him the possession right after you incorrectly claimed that was a tool to dismiss him.)

Online AnalogMan

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Re: Helical Engine
« Reply #8 on: 10/14/2019 07:20 pm »
There is a conference paper that accompanies the presentation slides linked to in the second post.  May give more details for those who are interested.

Links:
https://ntrs.nasa.gov/search.jsp?R=20190029294
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190029294.pdf

Offline meberbs

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Re: Helical Engine
« Reply #9 on: 10/14/2019 07:51 pm »
There is a conference paper that accompanies the presentation slides linked to in the second post.  May give more details for those who are interested.

Links:
https://ntrs.nasa.gov/search.jsp?R=20190029294
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190029294.pdf
Looking through this confirms my initial thoughts. They are ignoring the fact that no force in the z-axis means constant z component of momentum, not constant z component of velocity. They also seem to miss the fact that a force tangential to the circle with no z component would have both parallel and perpendicular components (relative to particle velocity) which are related to acceleration by different equations as they show. If they worked through the math on those equations, the result would change the z component of velocity at exactly the rate needed to keep the z component of momentum constant.

Offline mlorrey

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Re: Helical Engine
« Reply #10 on: 10/14/2019 11:53 pm »
This is just Burns trying to coopt Woodward's Mach Effect theory and his thruster tech, and apply his own  theory to it so he can slap his name on it.
No, this has literally nothing to do with Mach effects.

Also, you just finished telling people off in the other thread for daring to refer to it as Woodward's effect, and now you do so yourself, giving the possession to him. (Which isn't actually wrong, the issue is you giving him the possession right after you incorrectly claimed that was a tool to dismiss him.)
Woodward deserves credit for the theoretical work and experimental work, and as the discoverer, he has the right to name the effect. Burns has his own theory to claim inertial manipulation via transient mass variations. This sort of cooption is  not new. Sonny White tried to do the same thing several years ago, while in possession of a Mach Effect Thruster made for him  by  Woodward.
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Online leovinus

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Offline Ixokani

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Re: Helical Engine
« Reply #12 on: 10/16/2019 12:38 pm »
I like the analogy in one of the comments on that ARS article:

https://arstechnica.com/science/2019/10/corkscrewing-bouncy-ion-drive-would-provide-thrust-in-different-universe/?comments=1&post=38115607#comment-38115607

Quote
It sounds like the equivalent of taking your car out of gear, sitting in the back seat and trying to get it to move forward by throwing a tennis ball (at relativistic velocities) at the dashboard.

Offline ChrisWilson68

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Re: Helical Engine
« Reply #13 on: 10/16/2019 05:52 pm »
Like a lot of threads in this section, this isn't so much a "New Physics" idea.  It's more a "Conventional Physics Claimed to Do Something Mathematically Proven Impossible with Conventional Physics" idea.  Or, perhaps more succinctly, "Bad Math with Conventional Physics".

Maybe we need a new section.

Offline trm14

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Re: Helical Engine
« Reply #14 on: 10/16/2019 07:38 pm »
Like a lot of threads in this section, this isn't so much a "New Physics" idea.  It's more a "Conventional Physics Claimed to Do Something Mathematically Proven Impossible with Conventional Physics" idea.  Or, perhaps more succinctly, "Bad Math with Conventional Physics".

Maybe we need a new section.

It's really strange and frustrating how many seem to think that some sort of clever contraption can do something that can be proven to be impossible within known laws of physics. Yet they claim that no new physics is needed. Though I guess I shouldn't be surprised, impossibility of angle trisection (under the classical rules) has been known for more than 150 years, but plenty of people are still trying.

There's appears to be an odd divide in people's minds between conservation of energy on one hand and conservation of momentum on the other.  I seems to me that people are much more willing to accept propellantless drives than perpetual motion machines, as if conservation of energy were somehow a more sacred law of nature.

Offline edzieba

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Re: Helical Engine
« Reply #15 on: 10/17/2019 12:49 pm »
Like a lot of threads in this section, this isn't so much a "New Physics" idea.  It's more a "Conventional Physics Claimed to Do Something Mathematically Proven Impossible with Conventional Physics" idea.  Or, perhaps more succinctly, "Bad Math with Conventional Physics".

Maybe we need a new section.

It's really strange and frustrating how many seem to think that some sort of clever contraption can do something that can be proven to be impossible within known laws of physics. Yet they claim that no new physics is needed. Though I guess I shouldn't be surprised, impossibility of angle trisection (under the classical rules) has been known for more than 150 years, but plenty of people are still trying.

There's appears to be an odd divide in people's minds between conservation of energy on one hand and conservation of momentum on the other.  I seems to me that people are much more willing to accept propellantless drives than perpetual motion machines, as if conservation of energy were somehow a more sacred law of nature.
To play Devils Advocate:
A close approximation of a reactionless drive is useful even if it not a 'real' reactionless drive. A perfect angle trisector may be impossible, but a 6-sigma approximation is still useful for the cases where you need to draw an angle geometrically. Likewise, your drive may not be a 'true' reactionless drive and may 'merely' be just pushing against distant masses/vacuum potential/dark energy/all of the universe/the luminiferous aether, but if it takes in energy and gains momentum with more efficiency than a photon rocket, then it has utility.

The problem of course is that so far no drive has even met the low bar of demonstrating the same efficiency as a photon rocket (or indeed working period).

Offline Star One

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Re: Helical Engine
« Reply #16 on: 10/17/2019 01:35 pm »
Like a lot of threads in this section, this isn't so much a "New Physics" idea.  It's more a "Conventional Physics Claimed to Do Something Mathematically Proven Impossible with Conventional Physics" idea.  Or, perhaps more succinctly, "Bad Math with Conventional Physics".

Maybe we need a new section.

Yet the person proposing this is hardly some nobody from the streets. So I would guess he’s more qualified than you or I in this area.

Offline trm14

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Re: Helical Engine
« Reply #17 on: 10/17/2019 03:19 pm »
To play Devils Advocate:
A close approximation of a reactionless drive is useful even if it not a 'real' reactionless drive. A perfect angle trisector may be impossible, but a 6-sigma approximation is still useful for the cases where you need to draw an angle geometrically. Likewise, your drive may not be a 'true' reactionless drive and may 'merely' be just pushing against distant masses/vacuum potential/dark energy/all of the universe/the luminiferous aether, but if it takes in energy and gains momentum with more efficiency than a photon rocket, then it has utility.

But all of those would mean new physics (at least according to how most physicist see it), while many claim to get propellantless propulsion from well established theories like Maxwell's equations or special relativity. 

Sure, there are also some theories that do propose new physics, although none have been particularly convincing. But at least the proposers recognise that something new is needed.

(Constructing a perfect trisector of an angle is possible and at least one method was known to ancient Greeks. But it isn't a compass and (unmarked) straightedge construction.)
« Last Edit: 10/17/2019 04:18 pm by trm14 »

Offline meberbs

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Re: Helical Engine
« Reply #18 on: 10/17/2019 03:20 pm »
To play Devils Advocate:
A close approximation of a reactionless drive is useful even if it not a 'real' reactionless drive. A perfect angle trisector may be impossible, but a 6-sigma approximation is still useful for the cases where you need to draw an angle geometrically. Likewise, your drive may not be a 'true' reactionless drive and may 'merely' be just pushing against distant masses/vacuum potential/dark energy/all of the universe/the luminiferous aether, but if it takes in energy and gains momentum with more efficiency than a photon rocket, then it has utility.
No, you are stretching the analogy to where it doesn't apply. A close approximation of a reactionless drive is still a device that sits there and does nothing. All of those things that you listed about how the drive actually pushes off something: those are not possible within standard physics. They all require something new or magical to appear to make them work. The whole point is that many concepts such as the one in this thread, or Shawyer's claims about the emDrive are claimed to work without any of that. Since they are based purely on existing physics, it is 100% guaranteed that the result is due to a maathematical error by the person proposing it.

Yet the person proposing this is hardly some nobody from the streets. So I would guess he’s more qualified than you or I in this area.
No he literally says that he is not a subject matter expert when he says that the proposal has not been reviewed by a subject matter expert and may contain errors. There is no reason to think he is more qualified than any other random person, and is certainly less qualified than anyone who knows that special relativity is proven consistent and that such ideas simply do not work in it. To his credit he at least acknowledged that he may be wrong unlike roughly 90% of such impossible proposals.

Offline Bob012345

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Re: Helical Engine
« Reply #19 on: 10/17/2019 04:15 pm »
Like a lot of threads in this section, this isn't so much a "New Physics" idea.  It's more a "Conventional Physics Claimed to Do Something Mathematically Proven Impossible with Conventional Physics" idea.  Or, perhaps more succinctly, "Bad Math with Conventional Physics".

Maybe we need a new section.

It's really strange and frustrating how many seem to think that some sort of clever contraption can do something that can be proven to be impossible within known laws of physics. Yet they claim that no new physics is needed. Though I guess I shouldn't be surprised, impossibility of angle trisection (under the classical rules) has been known for more than 150 years, but plenty of people are still trying.

There's appears to be an odd divide in people's minds between conservation of energy on one hand and conservation of momentum on the other.  I seems to me that people are much more willing to accept propellantless drives than perpetual motion machines, as if conservation of energy were somehow a more sacred law of nature.

The idea that we know enough to discount any conceivable possibility that the laws of physics as we know them might have some practical "loopholes" at least at a local level yet to be discovered is the more problematic stance. For example, can one say apriori that it wouldn't be worth it to even consider the existence of such things as Mach effect devices? Especially when we do admit in physics violations of energy conservation at the quantum level, entanglement over the size of the universe, multiple universes just springing into existence which seemingly also violate conservation of energy. The problem is that the proof that something is impossible often assumes only what's known at present and disallows not necessarily new physics, though that may be needed, but new understandings of established physics. In 1957 Yang and Lee won a Nobel prize for overthrowing the Conservation of Parity, something so basic to physicists it was as shocking as overthrowing conservation of momentum would be. Then there's concepts such as the Alcubierre Drive which though may never be, probably won't be practical, at least in principle allowed the possibility to overcome the speed of light. Shocking indeed. Perhaps the reviewers should have just told Alcubierre that his idea used "bad math" and violated Special Relativity and prevented publication! That seems simple, enough on the surface. I'm glad they didn't so the idea could be explored.

BTW, true propellentless propulsion devices would also be energy generation devices. Just spin up the device in a rotating reference frame with constant power giving constant acceleration and harvest the kinetic energy in a non-rotating frame where the kinetic energy rises as time squared. Of course that cuts two ways as it could also be used as an argument such a device is impossible.
« Last Edit: 10/17/2019 04:31 pm by Bob012345 »

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