Friday, March 25, 2016

Reaching for the Stars

Scientists and engineers in BAE Systems' Project Greenglow are trying to control, or sidestep, gravity.

Back on my side of the Atlantic, scientists at NASA's Eagleworks say they've successfully tested prototype RF resonant cavity thrusters and a warp field generator. Other scientists are skeptical. Very skeptical.
  1. Project Greenglow, Gravity, and Dime Store Magnets
  2. The Weird Stuff: EM Drives, Warp Field Generators, and More
Newfangled ideas appeal to some, and upset others. (February 20, 2015; January 9, 2015; July 18, 2014))

Maybe, back in the 'good old days' when fire was the latest thing in high tech, some folks still slept with their backs against a tree, hoping hyenas didn't find them — while congratulating themselves on not being like those fire-making innovators.

The rest of us: well, that's another topic. (May 29, 2015)


Rockets in Space: "Absurd?"


Yes, someone actually opined that rockets won't work in a vacuum:
"JULY 17, 1969: On Jan. 13, 1920, Topics of The Times, an editorial-page feature of The New York Times, dismissed the notion that a rocket could function in a vacuum and commented on the ideas of Robert H. Goddard, the rocket pioneer, as follows: 'That Professor Goddard, with his 'chair' in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react -- to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools.'

"Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error."
("150th Anniversary: 1851-2001; The Facts That Got Away," Tom Kuntz, The New York Times (November 14, 2001))
Quite a few folks apparently still haven't gotten used to the idea, judging from articles like this:
The first interstellar probes may use rocket engines for propulsion: or not. There are some intriguing — and testable — ideas on the table.

Quotes



(From NASA/Tracy Caldwell Dyson, via Wikimedia Commons, used w/o permission.)
("Self portrait of Tracy Caldwell Dyson in the Cupola module of the International Space Station observing the Earth below during Expedition 24."
(Wikimedia Commons))
"Manned space flight . . . has opened for us thus far only a tiny door for viewing the awesome reaches of space. Our outlook through this peephole at the vast mysteries of the universe only confirms our belief in its creator."
(Wernher von Braun, cited in Awake! magazine (June 22, 1999), via Wikiquote)

"O LORD, our Lord, how awesome is your name through all the earth! You have set your majesty above the heavens!

"When I see your heavens, the work of your fingers, the moon and stars that you set in place -

"What are humans that you are mindful of them, mere mortals that you care for them?

"Yet you have made them little less than a god, crowned them with glory and honor."
(Psalms 8:2-6)

"The heavens declare the glory of God; the sky proclaims its builder's craft."
(Psalms 19:2)

"4 Indeed, before you the whole universe is as a grain from a balance, or a drop of morning dew come down upon the earth.

"But you have mercy on all, because you can do all things; and you overlook the sins of men that they may repent.

"For you love all things that are and loathe nothing that you have made; for what you hated, you would not have fashioned."
(Wisdom 11:22-24)

1. Project Greenglow, Gravity, and Dime Store Magnets



(From BBC News, used w/o permission.)
("Dr Ron Evans, the man behind Project Greenglow"
(BBC News))
"Project Greenglow and the battle with gravity"
BBC News Magazine (March 23, 2016)

"A handful of leftfield scientists have been trying to harness the power of gravity. Welcome to the world of Project Greenglow, writes Nic Young.

"In science there exists a uniquely potent partnership between theory and engineering. It's what's given us atomic energy, the Large Hadron Collider and space-flight, to name a few of the more headline acts.

"The theorists say: 'This is theoretically possible.' The engineers then figure out how to make it work, confident the maths is correct and the theory stands up.

"These camps are not mutually exclusive of course. Theorists understand engineering. Engineers draw on their deep understanding of the theory. It's normally a pretty harmonious, if competitive, relationship...."
This is where I could declare that "tampering with things man was not supposed to know" will lead to something pretty much awful.

But I won't, for reasons that I've said so often that I'm tired of repeating them. For now. ☺ (March 18, 2016; March 11, 2016; March 3, 2016)

Some scientists who say controlling gravity isn't practical, or possible, may simply be repeating what they learned in physics 101.

Most, I suspect, understand what's involved:
"...First of all, there was the big, big problem of scale. As Dr Clifford Johnson from the University of Southern California puts it: 'We tend to think of gravity as very strong - after all it's what binds us to the earth. But actually of all the forces we know in nature, gravity's the weakest.

" 'Let me give you a number. It's 10 to the power 40 times weaker than electromagnetism, that's a one with 40 zeros after it!' It seemed that even if one could manipulate gravity in the lab, there was almost nothing there to create any meaningful effect.

"In short, to alter the gravity of a planet, you need the mass of another planet...."
(BBC News Magazine)
Think about it this way: a dime store magnet weighing an ounce will pull a paper clip up, against the force of Earth's gravity.

Putting numbers on that comparison, one ounce is roughly 0.028 kilograms. Earth's mass is right around 5,900,000,000,000,000,000,000,000 kilograms: which is a good example of why scientists use scientific notation, and that's another topic.

Besides, gravity isn't so much a force as it is an effect of space-time's curvature caused by concentrations of mass-energy. That's what Einstein's general theory of relativity says, anyway, and that's the best explanation we've found so far.

Newton, Phlogiston, the Big Bang, and an Expanding Universe


A century from now, we may have a better explanation for gravity. Speaking of which, Newton's law of universal gravitation isn't "wrong."

It's still a pretty good approximation of the phenomenon: and "still considered accurate enough for most small calculations," as the BBC News article said.

I figure Einstein's theory may hold up longer than Becher's phlogiston combustion theory: which made sense, given what researchers knew in 1667. Unlike phlogiston, however, new data has been supporting general relativity's predictions: for the most part. (April 10, 2015)

We also discovered that this universe is expanding.

A bit later we learned that the data makes more sense if we assume that this universe expanded really fast in the moments after the Big Bang, slowed down abruptly: and that the rate of expansion has been increasing since then. (April 17, 2015; April 10, 2015)

That's — odd — and almost certainly means that we have a great deal left to learn.

To the Stars — Doing the Math



(From Project Greenglow, via BBC News, used w/o permission.)
("One of the original sketches for Project Greenglow"
(BBC News))
"...When, in the late 1980s, the aerospace engineer Dr Ron Evans went to his bosses at BAE Systems and asked if they'd let him attempt some form of gravity control, they should probably have offered him a cup of tea and a lie down. Gravity control was a notion beloved of science fiction writers that every respectable theoretical physicist said was impossible.

"As Evans himself admits, it was a tough sell. 'Let's be clear - there were many people in the company who felt we shouldn't do it because we made aeroplanes and this was highly speculative.' Pushing against gravity with wings and jets was BAE's multi-billion pound business, why dabble in scientific heresy? Because, as Evans puts it: 'The potential was absolutely enormous. It could totally change aerospace.'...

"...In the US, Nasa aerospace engineer Marc Millis began a parallel project - the Breakthrough Physics Propulsion Program. Nasa had committed to getting beyond the solar system within a generation, but knew conventional rockets would never get them there.

"According to Millis: 'If you wanted to go to our nearest neighbouring star, and say you want to do it in 50 years, you're having to go at a tenth of the speed of light. Well, the amount of propellant you'd need for that journey is about the mass of our entire sun. We needed something radically different.' Like Evans, Millis was told: 'To think radical, and think big.'..."
(BBC News Magazine)
Researching this post, I learned that at least one chap believes that human spaceflight is a hoax, "even if rockets actually work in vacuum." In his version of reality, Yuri Gagarin's 1961 Earth orbital flight was "communist propaganda."

Oddly enough, he didn't mention the Illuminati and the shape-shifting space-alien lizard-men who control the world. Allegedly.

Before getting back to interstellar flight, a link to the Lemming's discussion of conspiracies; with tongue firmly in cheek:
Getting back to Marc Millis, the Breakthrough Physics Propulsion program, and big numbers —

Saying that "the amount of propellant you'd need for that journey is about the mass of our entire sun" is a good comparison: or would be, if Marc Millis had described the payload and propulsion system. Maybe he did, and BBC News edited that part out.

I did a little checking — there's a link list of resources at the end of this section — the energy needed to accelerate one ton to one tenth the speed of light is 125 terawatt hours: minimum. Unless the mission is to fly by the destination at that speed, decelerating the mass will take the same energy.

That's a lot of energy: very roughly what everyone on Earth uses in 11 hours, if I did the math right.1

I suspect that Millis had in mind a spacecraft with something like a one ton payload, driven by rockets like the ones we use today.

That gets me to mass ratio, the ratio of a rocket's mass with propellant to its mass empty. Multistage rockets are more efficient, since they drop 'empty' parts along the way.

I agree that "conventional rockets would never get them there." More accurately, a spacecraft like Voyager could reach Alpha Centauri: in about 10,000 years.

I talked about interstellar distances, Guy Ottewell's "THE THOUSAND-YARD MODEL/or, The Earth as a Peppercorn" Solar System model, and Wolf 1061 earlier this month. (March 3, 2016)

By the time we have tech that will stay in working order that long, I strongly suspect that we'll have cut the travel time considerably. (January 15, 2016)

Big, but (Fairly) Conventional: Beamed-Core Antimatter Rockets, Gigawatt Laser Arrays


"Conventional" rockets, using energy released by chemical reactions, aren't the only propulsion tech available today.

NASA's Dawn mission uses NSTAR thrusters, Magnetohydrodynamic rocket engines that are much more efficient than their chemical counterparts. (March 13, 2015)

The faster a rocket's exhaust is, the more efficient it is: so ideally the exhaust velocity would be speed-of-light, hence speculative fiction's 'photon drive.'

A beamed core antimatter rocket isn't quite a photon rocket, but the electrons and positrons in its exhaust would be traveling at just under the speed of light.

We know the physics involved, but building one isn't practical today.

For one thing, antimatter is still hard to contain and expensive to produce.

For another, the positive pion/negative pion to positive muon/negative muon to positron/electron reaction requires a containment structure about 1,871 meters long: 6,138 feet. (October 3, 2014)

That's a small project, compared to some other proposals using today's science.

One of my favorites is Robert Forward's gigawatt laser array powered by solar collectors sharing Mercury's orbit, a planet-size fresnel lens several dozen astronomical units out focusing the beam on a light sail.

The technology involved isn't much more advanced than what we have now, although keeping equipment in good condition that close to our sun would be a challenge. My guess is that the cost is what will keep that proposal on the drawing board — for now.

I suspect something like Forward's laser array could push asteroids and comets out of Earth-impact orbits, and that's yet another topic.

'Photon drives,' light sails, and conventional rockets all use Newton's third law of motion:
Next: unconventional propulsion systems.


2. The Weird Stuff: EM Drives, Warp Field Generators, and More



(From Dr. Harold (Sonny) White, Eagleworks Lab; via NASASpaceFlight.com; used w/o permission.)
(NASA Eagleworks' warp-field interferometer test apparatus.)
"Evaluating NASA’s Futuristic EM Drive"
José Rodal, Ph.D, Jeremiah Mullikin, Noel Munson; NASASpaceFlight.com (April 29, 2015)

"A group at NASA’s Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum – a major breakthrough for a multi-year international effort comprising several competing research teams. Thrust measurements of the EM Drive defy classical physics' expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.

"EM Drive:

"Last summer, NASA Eagleworks – an advanced propulsion research group led by Dr. Harold 'Sonny' White at the Johnson Space Center (JSC) – made waves throughout the scientific and technical communities when the group presented their test results on July 28-30, 2014, at the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference in Cleveland, Ohio.

"Those results related to experimental testing of an EM Drive – a concept that originated around 2001 when a small UK company, Satellite Propulsion Research Ltd (SPR), under Roger J. Shawyer, started a Research and Development (R&D) program...."
First of all, I am not making this up.

NASA seems to have put warp field research on the back burner: no surprise, considering America's politics and economy, and that's yet again another topic.

Research outlined in this article (not affiliated with NASA, by the way, despite the name) isn't 'tin foil hat' stuff, though. The Alcubierre metric and other ideas may go the way of phlogiston: or not. Right now, we're sorting that out.

Informed speculation by scientists:
- - - and the Dean Drive:
Norman Lomer Dean may or may not have really believed that he'd invented a reactionless drive. However:
"...Dean made several controlled private demonstrations of a number of different devices, however no working models were ever demonstrated publicly or subjected to independent analysis and Dean never presented any rigorous theoretical basis for their operation. Analysts conclude that the motion seen in Dean's device demonstrations was likely reliant on unsymmetrical frictional resistance between the device and the surface on which the device was set, resulting in the device moving in one direction when in operation, driven by the vibrations of the apparatus...."
(Wikipedia)
After Dean's death, folks didn't find any working models, or diagrams, of his 'Dean drive.'

The demonstration models he'd shown had been obviously different from his patents; and those were missing, too. This is the stuff of which conspiracy theories are made: but I figure that efforts to replicate the Dean drive failed because it doesn't work: and never did.

RF resonant cavity thrusters, "EM Drives," sound a bit like the Dean Drive, with one important difference: they can be tested, and apparently work.

I'll get back to that, after a quick — for me — look at the Bussard ramjet, which probably won't work.

'It Looked Good on Paper'



(From DavidSZondy.com, used w/o permission.)
(Bussard fusion ramjet: it looked like a good idea at the time.)

Back in 1960, physicist Robert W. Bussard had what looked like a good idea: the Bussard ramjet. The math was valid, as far as it went; but involved "handling energy in quantities that scientists refer to in technical terms as 'bat guano crazy.'2"

It looked good on paper.

Interstellar space is far from empty. Depending on where you are in our galaxy, there's between 0.0001 and 1,000,000 molecules in each cubic centimeter.

That sounds like a lot, but the best "vacuum" we can get in an Earth-surface lab has about 10,000,000,000 molecules per cubic centimeter: which is another reason why space-based labs make sense, and that's still another topic.

About 99% of the stuff is gas, the other 1% dust. The gas is about 91% hydrogen, 9% helium, plus 0.1% of everything else. Quite a bit of it's ionized; so magnetic fields could, in principle, concentrate the stuff enough for fusion to happen.

That sounds promising, since stars run on hydrogen fusion. On the down side, the proton-proton chain reaction only works for some varieties of hydrogen.

Bussard said that the interstellar medium had enough non-hydrogen/helium to keep the CNO (carbon–nitrogen–oxygen) fusion cycle going.

He may have been right, but a 'small' Bussard ramjet needs an intake several kilometers across. For meaningful payloads, we're talking a scoop tens of thousands of kilometers across.

That picture shows the habitat and fusion engine of a 'Bussard' ship: that part is a few hundred meters long. Fanning out at the right are the "field wires," stretching out thousands of kilometers. Minimum.

Comparison time again: Earth is about 12,750 kilometers across. I'm an American with a nearly-lifelong interest in science and engineering, so I'm used to big numbers: but that's big, even by my standards.

Given time and motivation, humanity may get around to building planet-size structures. My guess is that's a long way off, though.

I won't dismiss the idea, though. Back when the sickle was cutting-edge agricultural technology, my ancestors might have found something like the Antonov An-225 Mriya or MS Oasis of the Seas implausible.

Someone may find a way around the 1985 Zubrin/Andrew analysis of Bussard ramjet technology: but it looks like even if we built a scoop big and light enough, the thrust produced is less than the system's drag:

The EM Drive and Other RF Resonant Cavity Thrusters


Radio frequency (RF) resonant cavity thrusters produce thrust without reaction mass or directional radiation: so they're apparently in violation of the law of conservation of momentum.

That's the principle that total momentum is constant in a closed system. Newton's laws of motion and all that.

Scientists who have been developing hardware to test their theories say RF resonant cavity thrusters conserve momentum: but not the usual way.

NASA's Eagleworks tested EM Drive and Cannae drive devices. They say the things produced thrust: not much, but measurable amounts.

Other scientists say that the results show effects of air currents, don't adequately deal with observational error, or aren't right for other reasons. They could be right.

Scientists who are working on RF resonant cavity thrusters say that they've got solid theory to explain what's happening. They could be right. So far, it's "controversial" in the sense that scientists are dealing with a set of new ideas that don't fit what they learned in high school.

These thrusters send microwaves into an enclosed conical metal chamber with a dielectric resonator at the small end. The idea is that electrical power runs the magnetron, directional thrust gets sent toward the narrow end — where it gets caught, sort of.

This excerpt from a Wikipedia page is a pretty good example of how the research and discussions have been going:
"...Shawyer has self-published theory papers about the EmDrive. These include the fundamental assertion underlying the theory: '[t]his force difference is supported by inspection of the classical Lorentz force equation F = q(E + νB). (1) If ν is replaced with the group velocity νg of the electromagnetic wave, then equation 1 illustrates that if vg1 is greater than vg2, then Fg1 should be expected to be greater than Fg2." This statement makes two assumptions which Shawyer does not substantiate and which may explain the discrepancy between Shawyer's predictions and those of conventional physics. For example he assumes that radiation pressure is the result of the Lorentz force acting on charged particles in the reflecting material. This is analyzed by Rothman and Boughn[32] who point out that the standard theory of radiation pressure is more complicated than the simplified analysis suggests...."
(Theory, RF resonant cavity thruster, Wikipedia)
Maybe these thrusters work because there's a radiation pressure imbalance between the two faces, or because they create a virtual plasma toroid, producing net thrust using magnetohydrodynamic forces acting on quantum vacuum fluctuations.

Or maybe the researchers were detecting pressure from air currents. I don't know.

Complicating matters, RF resonant cavity thrusters have an annoying habit of "dying from internal corona discharges around [their] RF output circulator." ("NASA Emdrive experiments have force measurements while the device is in a hard vacuum," The Next Big Future (February 07, 2015))

Replacing them costs money, so researchers have to wait until there's room in the budget.

That NASASpaceFlight.com article says that the Eagleworks warp-field interferometer produced (very slight) results last year:
"...During the first two weeks of April of this [2015] year, NASA Eagleworks may have finally obtained conclusive results. This time they used a short, cylindrical, aluminum resonant cavity excited at a natural frequency of 1.48 GHz with an input power of 30 Watts.

"This is essentially a pill-box shaped EM Drive, with much higher electric-field intensity, aligned in the axial direction. The interferometer's laser light goes through small holes in the EM Drive.

"Over 27,000 cycles of data (each 1.5 sec cycle energizing the system for 0.75 sec and de-energizing it for 0.75 sec) were averaged to obtain a power spectrum that revealed a signal frequency of 0.65 Hz with amplitude clearly above system noise. Four additional tests were successfully conducted that demonstrated repeatability.

"One possible explanation for the optical path length change is that it is due to refraction of the air. The NASA team examined this possibility and concluded that it is not likely that the measured change is due to transient air heating because the experiment’s visibility threshold is forty times larger than the calculated effect from air considering atmospheric heating...."
(NASASpaceFlight.com)
A next step will be to repeat the steps in a vacuum.

More stuff you may find interesting, or not:

Afterword: "A Planet is the Cradle...."


As I write this, Thursday night is turning into Friday morning. It's Holy Week, tomorrow's a big day, and besides — I need sleep. A brief quote, and I'm done:
"Планета есть колыбель разума, но нельзя вечно жить в колыбели"
"A planet is the cradle of mind, but one cannot live in a cradle forever."
(Konstantin Eduardovich Tsiolkovsky, from a letter written in 1911, via Wikiquote)


More, looking around and looking ahead:

1 The International Energy Agency's estimate of world energy use in 2012 was 104,426 terawatt hours.

2 That gem is from David S. Zondy's excellent website. It's still up and running, but as of March 24, 2016 he has still not been able to fix display issues — not his fault, I think. He and his hosting service had a difference of opinion which ended badly, for him. His content is still available, but I have to highlight text to make it visible. It's worth the effort, I think:
  • "Bussard Ramjet"
    Spaceship, Future Space, Tales of Future Past; DavidSZondy.com

2 comments:

Brigid said...

Extra word: "may be simply be repeating what"

Missing letter: "with observatonal error,"

Wrong word: "by I have to highlight text to make it visible."

The Friendly Neighborhood Proofreader

Brian Gill said...

Brigid: Oops. Right. Fixed! Thanks!

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Marian Apparition: Champion, Wisconsin

Background:Posts in this blog: In the news:

What's That Doing in a Nice Catholic Blog?

From time to time, a service that I use will display links to - odd - services and retailers.

I block a few of the more obvious dubious advertisers.

For example: psychic anything, numerology, mediums, and related practices are on the no-no list for Catholics. It has to do with the Church's stand on divination. I try to block those ads.

Sometime regrettable advertisements get through, anyway.

Bottom line? What that service displays reflects the local culture's norms, - not Catholic teaching.