Re: A gravitational wave rocket

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spudb...@aol.com

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Jan 15, 2022, 11:55:58 PMJan 15
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So earlier today I watched Sabine hassenfelder the physicist from Germany indicate that any kind of wormhole travel or FTL is strictly unlikely. What I'd like to ask is, whether all the work that's done today for creating commercial nuclear fusion is more or less likely, than using the same technology to develop fusion plasma rockets to travel much more swiftly within the solar system? Our fusion plasma rockets the lower hanging fruit, versus commercial nuclear fusion? Thanks!


On Saturday, January 15, 2022 Lawrence Crowell <everyth...@googlegroups.com> wrote:

It is possible for a binary star system to interact with a third star so there is an exchange.  We do normally expect binary star systems to have similarly oriented angular momenta.

 This is an interesting result. To compute this would have been tough. This is a case of a Robinson-Trautman twisting solution or a twisting type N. The addition of the two angular momenta results in the occurrence of angular momenta perpendicular to the initial angular momenta. This can be seen in with the classical group [L_i, L_j] = ε_{ijk}|L|^2 n_k, for n_k a unit vector. This means there is the emission of angular momentum in the gravitational radiation. The calculation was most likely done numerically.

LC


On Thursday, January 13, 2022 at 1:13:02 PM UTC-6 johnk...@gmail.com wrote:
On Thu, Jan 13, 2022 at 1:37 PM Brent Meeker <meeke...@gmail.com> wrote:


> Kudos to whomever did the calculation for this.  But I would have thought that most collisions would be misaligned in both spin axes and impact plane.  The Sun's spin axis isn't aligned with the Milky Way's axis of rotation, so I had assumed most stars have randomly directed spin axes.

Stars do have random axis of rotations in general but not if you're talking about double stars, and the sun is rather unusual in being only a single star, most stars are double stars, and they were created at the same time from the same rotating cloud of gas and dust and thus have similar axis of rotation, so when the resulting stars turned into Black Holes they would also have similar axes. And indeed most of the Black Hole mergers so far detected by gravitational waves have been of that sort, but not this one, that's what makes it so unusual. This system must've been formed by two stars that formed at different places at different times but then got close together and somehow went into orbit around each other.  

John K Clark    See what's on my new list at  Extropolis
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Brent

On 1/13/2022 3:49 AM, John Clark wrote:
For the first time a sort of gravitational wave rocket has been found. By re-examining the data from the LIGO and Virgo gravitational wave observatories researchers report on January 6 they have detected the merger of 34 and 29 solar mass Black Holes that resulted in a Black Hole of about 62 solar masses with about one solar mass being converted into gravitational waves. What makes this merger unusual is that it was not symmetrical, the axis of spin of the 2 black holes were not aligned with each other and neither was aligned with the axis of orbit around each other. This would indicate that the 2 stars that form them (assuming these 2 large Black Holes were actually formed from the corpses of dead stars) were not born in an isolated system but probably came from a denser environment like a globular cluster. Even more interesting is that the misalignment of the spins means that the gravitational waves emitted were not emitted symmetrically, and gravitational waves carry some linear momentum. So the resulting 62 Solar mass Black Hole must've received a pretty substantial kick causing it to move pretty fast, and that's just what the researchers found, because of that kick the huge 62 solar mass Black Hole started moving at least 700 km a second and probably closer to 1500.  It's probably moving fast enough to escape whatever galaxy it was in.



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John Clark

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Jan 16, 2022, 5:50:03 AMJan 16
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On Sat, Jan 15, 2022 at 11:55 PM spudboy100 via Everything List <everyth...@googlegroups.com> wrote:

> So earlier today I watched Sabine hassenfelder the physicist from Germany indicate that any kind of wormhole travel or FTL is strictly unlikely.


I'd say practical wormhole travel, although not absolutely forbidden by the laws of physics as far as we know, is unlikely. And FTL, the ability to travel through space faster than light, as opposed to taking a shortcut through space as with a wormhole, is very very unlikely because that is forbidden by the laws of physics as we know them. We don't know everything but we do know some things, and some things can't be done. 
 

> What I'd like to ask is, whether all the work that's done today for creating commercial nuclear fusion is more or less likely, than using the same technology to develop fusion plasma rockets to travel much more swiftly within the solar system? Our fusion plasma rockets the lower hanging fruit, versus commercial nuclear fusion? Thanks!


If you have the technology to make a powerful fusion reactor light enough to fit into a rocket that can operate for years without maintenance then you certainly have the technology to make a commercial fusion reactor, but the reverse is not necessarily the case.

John K Clark    See what's on my new list at  Extropolis
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Brent Meeker

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Jan 16, 2022, 2:20:16 PMJan 16
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No, a fusion rocket is much more technologically difficult than a fusion power plant.  The power plant can be very large and heavy.  The power plant just need to produce heat; the rocket needs to direct the fusion products.

Brent

spudb...@aol.com

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Jan 16, 2022, 3:23:13 PMJan 16
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This surely can't be done anytime soon. My suspicion is that new discoveries of profound impact will wait until we can build better equipment, as Freeman Dyson state long ago. For astrophysics, this will be placing enormous telescopes at the Kuiper Belt and beyond. Does this change the physics? No, but it does open the opportunity of learning of new phenomena.  This can only change the big picture.  


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spudb...@aol.com

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Jan 16, 2022, 3:40:26 PMJan 16
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My guess is the opposite of this, because all we'd need to do is use plasma for thrust, as opposed to containing it successfully, to extract usable energy on planet earth.  Alternatively, there is inertial confinement fusion, which'd be an improvement over Freeman Dyson's Orion bomblets against a pusher plate. Here laser fusion would never contain the energy released by the micro-detonations,  simply be used as a driver for thrust. Nothing commercial here. just the thrust. Perhaps we could achieve the same thing using photon sails, that catch not the sun's light, but that of a massive solar power sat to push explorer and cargo craft from here to the Asteroid Belt?



Now, all we need is a budget ;-]

-----Original Message-----
From: Brent Meeker <meeke...@gmail.com>
To: everyth...@googlegroups.com
Sent: Sun, Jan 16, 2022 2:20 pm
Subject: Re: A gravitational wave rocket

John Clark

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Jan 16, 2022, 4:19:31 PMJan 16
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On Sun, Jan 16, 2022 at 3:23 PM spudboy100 via Everything List <everyth...@googlegroups.com> wrote:

> This surely can't be done anytime soon. My suspicion is that new discoveries of profound impact will wait until we can build better equipment, as Freeman Dyson state long ago.

I wrote this a few years ago for another list but as the subject of nuclear space propulsion has come up here and you mentioned Freeman Dyson I thought I'd repeat it: 
== 

I've been reading a little about an incredible idea taken very seriously in the late 50's and early 60's but today is almost completely forgotten, it was called Project Orion. The idea was to make a spaceship big enough for 150 people and all the equipment they could ever want and blast it into space. They wanted to make it 135 feet in diameter and 160 feet high and they wanted most of that space to be usable by people not wasted on fuel. They figured weight would be no problem, if a crew member wanted to bring along his antique bowling ball collection and his own personal barber chair there would be no objection. The advocates of this approach were not interested in low earth orbit or even the moon, they were certain they could be on Mars by 1965 and Saturn by 1970, the leader of the project was determined to visit Pluto. And they figured all this would cost less than 10% what the Apollo moon project did.

You might think that these people must have been a bunch of crackpots, but it's not so. Nobel Prize winners  Niels Bohr, Hans Bethe and Harold Urey were all enthusiastic advocates of the idea. Freeman Dyson thought the idea was so brilliant that he took a one year leave of absence from the prestigious Institute of Advanced Study so he could work full time on the project.

Yes, there is a catch, Project Orion needed nuclear energy, even worse it needed nuclear bombs. The Orion spacecraft would contain 2000 nuclear bombs, most in the 20 kiloton range, the size of the bomb that destroyed Nagasaki. A bomb in a tank of water would shoot out the back of the ship, when it was100 feet away it would explode, the water would hit a carefully designed 75 ton pusher plate and accelerate the ship. Between the pusher plate and the ship were 50 foot long gas filled shock absorbers to even out the jerk. They wanted everything to be as cheap as possible, so they asked the Coca-Cola company for the blueprints of one of their vending machines, then they scaled it up a little and planned to use it as the mechanism to dispense the bombs.

The pusher plate was obviously the most important part of the design. If you explode a powerful bomb near a circular plate of constant thickness it will shatter because of the uneven stresses that build up, but it turns out that if you carefully taper the plate and make certain that the explosion is dead center, the plate will be extraordinarily  resistant to damage. A layer on the plate will be vaporized by the heat but if some heavy protective oil is sprayed on it before each use it would be good for 2000 blasts. This beast was tough, if it was properly oriented the Orion Spacecraft could survive a 16 megaton H bomb blast from only two thousand feet away, a fact of more than passing interest to the military. Orion needed lots of radiation shielding to protect the crew, but weight was never an issue so this was no problem.

Wernher von Braun though all this was a dumb idea, then he saw a movie of the launch of a one meter working model of Orion that shot 6 carefully timed high explosives chemical bombs out the back of the model, it rose 300 feet into the air in stable controlled flight. Wernher von Braun became a vocal supporter of project Orion.


"Hot Rod" - Nuclear Orion spacecraft prototype (1959)

They planned to launch Orion from atop eight 250 foot towers in Jackass Flats Nevada. The first bomb would be tiny, just 0.1 kiloton (100 tons of TNT) exploded 100 feet below the craft and 150 feet above the ground, then a new and slightly larger bomb would be spit out the back every second for 50 seconds, the last bomb would be the largest, 20 kilotons, and by then the craft would be out of the atmosphere, the total yield of the 50 bombs would be 200 kilotons. The launch would have been a spectacular sight, it'd make the Space Shuttle look like a bottle rocket.

Project Orion was led by Ted Taylor, a mediocre physicist but a very good inventor. Taylor had one unique talent, he has been called by some the best nuclear weapon engineer on planet Earth and the Leonardo da Vinci of nuclear bomb design. Taylor is the man who figured out how a two foot long 200 pound bomb could be made as powerful as the 12 foot long 10 ton World War 2 Nagasaki bomb. The reason the Orion spaceship was so much bigger and faster than anything we have today is that pound for pound such bombs have about a million times as much energy as any chemical rocket fuel.

Orion wasn't the only thing Taylor was interested in, he found a way to make a new type of nuclear bomb, one that would produce a highly directional blast. He designed a little one kiloton bomb that could blast a 1000 foot tunnel straight through solid rock, he wanted to build a cheap tunnel between New York and San Francisco and have a supersonic subway 3000 miles long.

Considering the big controversy we had when a deep space probe was launched with just a few pounds of non weapon grade Plutonium on it to power the electronics it may seem incredible and irresponsible that anyone would even consider something as environmentally unfriendly as Orion, but we live in a very different world. At the time Orion was under serious study the USA was blowing up one megaton bombs deep under the sea and 300 miles in space and the USSR was blowing up 57 megaton bombs in the atmosphere, Orion seemed and indeed was pretty benign compared to that.

It all came to nothing of course, in 1963 the test ban treaty was signed stopping all nuclear explosions in space or the atmosphere making Orion illegal. The project died, but to this day most say it would have worked technologically if not politically.

Idea for a science fiction novel: A huge nickel iron asteroid is heading for Earth, it would take a 200,000 megaton bomb to divert it but no existing rocket is nearly powerful enough to deliver such a huge payload to the asteroid. The Earth seems doomed, then our hero remembers Project Orion.
John K Clark    See what's on my new list at  Extropolis
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spudb...@aol.com

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Jan 17, 2022, 12:58:52 AMJan 17
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Clear back in 1974 the British Interplanetary Society did a paper where the ORION effect would be better fulfilled by Daedalus which would detonate thousands of deuterium-tritium pellets using electron beams. Same principle using many micro-detonations. Orion itself gives me the willies, if only because we'd have to stop it in an Newtonian manner, say when Dyson and company arrived to view Saturn's rings close-up. I am thinking of some means of slowing it down, because at fast speed, the gentle Hohnman Transfer Orbits become unavailable. Thus, we'd need thrusters of some kind to slow her down. 

Ted Taylor went on to work on solar ponds for providing air conditioning from ice frozen in the winter to provide cooling in the summer. A less grandiose project indeed. For fast interplanetary travel, there needs to be a motivator and yes, your meteorite would do, but mining the Belt seems more sustainable. I am not wedded to any one technology, just one that will work to specification.


-----Original Message-----
From: John Clark <johnk...@gmail.com>
To: 'Brent Meeker' via Everything List <everyth...@googlegroups.com>
Sent: Sun, Jan 16, 2022 4:18 pm
Subject: Re: A gravitational wave rocket

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Henrik Ohrstrom

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Jan 17, 2022, 4:06:37 AMJan 17
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You turn the rocket around and as you slow down using BF flashbulbs as you did at takeoff. That's your thruster. 
Also grav slingshoting can be used to slow down as well as hurry up.
If you have not played with Kerbal space program, do so now. It is the best way of getting an understanding of orbital mechanics. Then when you are getting cocky, try children of a dead earth. That one is a mouthful even for NASA personel.
/Henrik

Lawrence Crowell

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Jan 17, 2022, 7:05:09 AMJan 17
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Sabine Hossenfelder's video is about the warp drive, based on the Alcubierre warp solution of the Einstein field equations. Her conclusions are more or less on the mark I think. A sub-luminal (slower than light) warp drive could work. Even with negative mass-energy if the moduli for these fields is compact the vacuum could be stable. However, if it reaches the speed of light there occur horizons in the warp bubble that would disrupt it by preventing causal communications through it. 

The main investigator of this report of a possible warp bubble is Harold White, who has a history of being a bit "out there" on things. He also advanced the so-called EM drive last decade which was found to not work. Why anyone though that would work is beyond me. White has been a big exponent of the Alcubierre warp drive. To be fair though, this claimed result, is just a calculation of an energy spectra of the Casimir effect comparable to what a warp bubble would give, is how Kip Thorne proposes to generate wormholes. Wormholes and warp drives share the same energy feature with T^{00} < 0, for for a source that is a quantum field 〈0|T^{00}|0〉 < 0.

  https://bigthink.com/starts-with-a-bang/no-warp-bubble/

The Casimir vacuum provides the energy conditions required for the warp drive. The negative vacuum can be a source for hyperbolic geometry for exotic structures such as wormholes and warp drives. This experiment employed the Casimir vacuum and came up with results that appear suggestive of a warp bubble. This does not though mean we have conclusive evidence of one. There are some other reasons to maintain a skeptical perspective on this.

 The Alcubierre warp bubble is probably only stable for sub-light speed. If it is set above the speed of light it has particle horizons that causally separate the bubble. This means it is not stable, for Unruh-like radiation occurs.

This may lead to deep questions. for the vacuum energy is related to the moduli of curves, such as in the Poincare disk and half-plane, and this is also in some ways related to the moduli of gauge symmetry. Each curve bounds a region, thinking in 2-dimensions, and this region is associated with entropy and curvature. For this to work the vacuum has to be stable, which means it is Virasoro or CFT_2 or more. I think this imposes this limit on the warp bubble as being sub-light speed.

This warp bubble might exist, and for various reasons it would be a fascinating development for the foundations of physics. This is not to say I think we will be using this for spaceships, at least not at all soon. These DARPA results are suggestive, but actual experiments will have to rise to what might be called the 5-σ level. I am rather skeptical of this however, even though if this is real it would pave the way for a major probe of the quantum vacuum.

As for fusion, just getting a fusion powerplant is a big hurdle to jump. The Chinese have made an announcement of a fusion device that sustained 15 million K temperatures for 100 or a 1000 second. I cannot remember which. This has a long way to go, and as the joke goes, 20 years from now fusion power will still be 20 years in the future. As for a space power or propulsion, that is far out. We still do not have fission powered space systems or propulsion, and fusion will be far more difficult. The Chinese system is fairly large and the ITER program involves a really large reactor. Space based systems need to be small and as low mass as possible.

LC


John Clark

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Jan 17, 2022, 7:14:58 AMJan 17
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On Mon, Jan 17, 2022 at 12:58 AM <spudb...@aol.com> wrote:

> Clear back in 1974 the British Interplanetary Society did a paper where the ORION effect would be better fulfilled by Daedalus which would detonate thousands of deuterium-tritium pellets using electron beams. Same principle using many micro-detonations.
 
Yeah that would be better, but it would involve technology we don't even have today, but ORION would have used technology we had in 1960.

> Orion itself gives me the willies,

Me too, at least the atmospheric Earth launch part of it 

> if only because we'd have to stop it in an Newtonian manner, say when Dyson and company arrived to view Saturn's rings close-up.

I don't see the problem, they could use tiny chemical thruster rockets to turn the ship around 180 degrees or however much is needed until it's oriented correctly and then start up the main nuclear engine.  It would then slow down the same way it sped up.

> For fast interplanetary travel, there needs to be a motivator 

In the late 1960s the motivator to get into space was to beat the Soviet Union, I think that same motivator would have worked in the early 1960s too.   
John K Clark    See what's on my new list at  Extropolis
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