Earth and our home-planets float in a magnetized bubble of hot plasma spewed out by our sun in impressive speeds. The bubble's edge is like a placenta of sorts, which Voyager must break through to enter the Interstellar Ocean. Image courtesy of NASA/JPL (click to enlarge).
Is interstellar travel possible in our lifetime? Last week ExWebs 4-part Space series went up. Image courtesy of NASA.
Launched in 1977, Voyager 1 is the man-made object farthest away from Earth at approx 108 AU (AU=mean distance from Sun to Earth). Image courtesy of NASA/JPL (click to enlarge).
Estimated to be comms functional until 2025, the spacecraft registers signals in its environment and transmits them to the Deep Space Network (in Calif, Spain and Australia) dishes from where the messages are shot over to the Jet Propulsion Lab. Image courtesy of NASA/JPL (click to enlarge).
Not even our most kick-ass rockets (such as this Delta IV) are enough. 99% operate by chemical combustion; and even with the fanciest fine-tunes the propellant mass required to get to Alpha Centauri in 900 years using chemical systems exceeds the mass of the known Universe, said Greg. Image courtesy of NASA.
Among our advanced propulsion ideas are Ramjets scooping up interstellar hydrogen - refuelling as they go. The problem is that we would have to sweep 1018 cu. meters of space to collect a mere 1 gram of hydrogen. By comparison the engine of the experimental X-43A scramjet (in image) used about two pounds (1 kg) of hydrogen for about ten seconds of flight. Image coutesy of NASA (click to enlarge).
Here's where we are at right now, according to Gregory V. Meholic. The NASA readiness goes from "an idea" (red) to "working or worth a shot" (pink/white). Slide by Gregory V. Meholic (click to enlarge).
Gregory's bottom line is that conventional systems work for Mars but not for interstellar missions within a human lifetime. Science therefore needs a paradigm shift in propulsion technology: to move from mechanics-based to physics-based concepts. Slide by Gregory V. Meholic (click to enlarge).
The Cern particle collider has produced antimatter but not yet negative (dark) matter. The collider is looking for Higgs (God) particle to help us understand the true nature of Mass.
These are the only ideas allowing interstellar travel in reasonable time at this point, according to Greg. Slide by Gregory V. Meholic (click to enlarge).
NASA has put most of the Breakthrough Propulsion Physics theories to the test. "Null" Research Findings include a number of antigravity experiments, "unresolved" include inertia and gravity...
..."open" research (the most promising) are Space Drives (revisiting Mach's principle) and a few others. Slides by Gregory V. Meholic (click to enlarge).
ExWeb 2009 space report, part 2: Interstellar travel - from LOX to eternity over Einstein's speed bumps
Posted: Sep 16, 2009 07:47 pm EDT
(Pythom.com) Jetting between planets could soon become both routine and profitable, but at some point inhospitable home-rocks will bore us. We'll want to find real Earths like ours, or better.
So what are our chances to travel outside our solar system in reasonable time? Here goes an interstellar space travel crash course. Be ready, this story is a brutal head-spin, but worth it if you make it through.
To the edge!
Traveling to other planets in our own solar system is fairly easy. A number of man made spacecraft are already doing just that.
Launched in 1977, Voyager 1 is the farthest away from Earth at approx 108 AU (AU=mean distance from Sun to Earth). Estimated to be comms functional until 2025, the spacecraft still reports to JPL (NASA Jet Propulsion Lab in California).
Earth and our home-planets float in a magnetized bubble of hot plasma spewed out by our sun. The bubble's edge is like a placenta of sorts, which Voyager must break through to leave the mother womb.
When in recent years Voyager 1 began recording low-frequency (so low they are impossible to detect on earth) but very intense radio emissions, NASA knew they came from beyond our solar system. The ship was touching the edge!
Voyager first felt it at the termination shock (approx 85 AU) where the supersonic solar wind hit the interstellar wind and slowed to subsonic speed.
Crossing this area, Voyager has entered a storm of messed up plasma flow and magnetic fields. Final turbulence is to be expected in the bow shock (think a boat's bow breaking through water, thus the name), after which Voyager is free to drift with the great interstellar wind into the great unknown.
With 108 Sun to Earth distances behind it, Voyager is well into the stormy heliosheath (see top image). So when can we expect it to make it through?
The craft travels at about 3.6 AU per year. Some NASA folks believe the bow shock may lie at around 230 AU from the Sun. Depressingly enough that means another 30 years or so. And it gets worse. If Voyager was traveling in the direction of the nearest star, it would arrive there in about 75,000 years.
E = mc2: Einstein's speed bump
At 4.2 light years away (LY=Distance light travels in one year); Alpha Centauri is the closest star system to our sun. We would have to travel with the Speed of Light (c) to reach it in 4 years.
Even though Voyager rushes forward with an impressive speed of almost four time the distance between earth and sun in one year; it still travels at a mere fraction of "c" (less than 0.01%). So what chances do we have at all to travel to other stars within reasonable time (say 15 years)?
Beside the fact that we today have no idea how to reach Speed of Light, even if we did, Einstein's relation between energy and mass show that we balloon as we near c. At the very last stages of acceleration (actually just as we are so close we think we have it), the energy required to push us further will become infinite.
Using up the mass of the known universe; or Al Gore's ultimate nightmare
To reach other stars in reasonable time, we need to stop kicking at the same, old wall and change our thinking, said Advanced Technology/Performance Engineer Gregory V. Meholic, Senior Member of the Technical staff at The Aerospace Corporation in El Segundo, California.
And here's why:
99% of all rocket engines today operate by chemical combustion (think fireworks). This tech has however reached an upper limit of development, said Meholic, adding that even with the fanciest fine-tunes the propellant mass required to get to Alpha Centauri in 900 years using chemical systems exceeds the mass of the known universe.
As for our advanced conventional propulsion systems, nuclear fission (split atomic nuclei) and nuclear fusion (fuse atomic nuclei), both are very hard to store and contain. In addition, Greg said, fission is highly radioactive while fusion has yet to yield greater than 1% of the energy required to sustain it.
A third option is matter/antimatter annihilation (convert oppositely charged particles to energy). It's not as crazy as it sounds; Antimatter (AM) is a reality, we have already produced it in facilities such as the Cern particle accelerator.
The global annual production right now is a mere 2-20 nanograms/yr however, Gregory said, at a cost of $300B per milligram. A few grams of AM would contain enough energy to propel a spacecraft to Mars in one month, but creating it would take millions of years with existent technology. Storage is another problem, as AM cannot come in contact with normal matter.
Then there are the Ramjets, scooping up interstellar hydrogen and refueling as they go. Very tempting, except they would have to sweep 1018 cu. meters of space to collect a mere 1 gram of hydrogen, Greg said.
By comparison the engine of the experimental X-43A scramjet (a beefed up version of ram) used about two pounds (1 kg) of hydrogen for about ten seconds of flight.
Gregory's bottom line was that while conventional systems work for Mars; they don't for interstellar missions within a human lifetime. Science needs a paradigm shift in propulsion technology, he said, and move from mechanics-based to physics-based concepts.
Thinking outside the box
Vs=speed of the object relative to the medium
u=the speed of sound in the medium
Speed of sound on Earth: ca 343 m/s, 768 mph or 1,236 km/h = Mach 1
Subsonic speed: M < 1
Solar wind speed: approx 400 km/s
Stellar wind speed=stellar speed of sound: approx 100 km/s
Speed of Light: approx 300,000 km/s
After we escape through the bow shock, we'll enter the great interstellar ocean: a truly frigid and dark one. There are no suns to power our solar panels, no planetary islands for rest and provisions, and no objects to navigate by. And the stellar wind is too rarefied for sails.
Moving to physics-based concepts we arrive at warp drive, worm holes, and/or alternate dimensions. Let's take a closer look:
Warp Drive is accomplished when we generate a positive (attractive) gravity well in front of the spaceship and a negative (repulsive) well behind it. The region between the two fields (including our rocket) will move through space at speed of light or greater unaffected by relativistic effects.
The trouble is that warp drive would require negative matter. As opposed to antimatter (an electron with a positive charge or a proton with a negative charge for ex) we have never produced negative (dark) matter, whose existence we only guess from gravitational effects. If we did find it and could make it, our ship would possibly need up to a kilogram (compare to our yearly production of the "easy" antimatter at 2-20 nanograms/yr.)
Wormholes would offer instant travel between A and B without relativistic effects. Cons: building our own would require handling exotic matter in the size of neutron stars. Using existing ones would involve a seriously scary ride - in fact scientists now say that only entering such a hole would annihilate us.
Worm holes and warp drive are backed by good math. Other theories suffer complicated equations plus particles and forces entirely made up to fit the reasoning.
Scrubbing the box; mental free falls
Some of you might have read tales of people disappearing from home only to reappear on another side of the world moments later. This would be possible with the existence of hyperspace, where you simply step out of your space-time, step into another dimension (where travel at speed of light is normal), and then step back in again at your home dimension. Very convenient, the idea solves most problems and allows fast travel.
Only we have no proof of it at all, and critics say that Hyperspace including all its related faster-than-light travel (FTL) theories is mere wishful thinking, no more.
Yet among a vast number of misses in Breakthrough Propulsion Physics; there are actually a few hits, i e experiments showing favorable results. Looking for unusual answers, scientists study abnormal happenings.
Mach (that's right, the guy behind the sonic speed numbers listed above) is also behind the Mach's principle. Using his idea we try to make distant matter in Universe pull our ship towards it (remember the movie Contact) by creating mass fluctuations. Experiments in progress reportedly show curious signals related to rotational speed. Cons: while something seems to be going on we don't know what or why.
Other experiments involve superconductivity which takes place when metals and ceramic materials lose electrical resistance. Already used in MRIs and (slapped together) for super fast, high-speed computers, when superconductivity can be achieved in room temps our whole world of electronics, power and transportation will change. Within the vicinity of rotating, superconducting rings a gravity-like field is generated, 20-30 times stronger than predicted by general relativity! Not entirely understood, it's there, and if we can produce it efficiently we could use the force for propellant-less propulsion.
Then there is the weird Casimir effect (two uncharged metallic plates are placed in a vacuum a few micrometers apart, without any external electromagnetic field and no force between them: the plates still react - creating a force attracting or repulsing each other.)
NASA has put most of the Breakthrough Propulsion Physics theories to the test. "Null" Research Findings include a number of antigravity experiments, "unresolved" include inertia and gravity, "open" research (the most promising) are mainly Space Drives (revisiting Mach's principle). Check Greg's slides illustrating this story for more.
Even with such iffy results, if we really put our minds to it, it would take no more than 50 years to find a way to reach outer stars in reasonable time, Gregory said.
And why not, Tom Sjogren from HumanEdgeTech agrees. We've after all come a long way and most of it only in the last century. Looking at the problem from another angle, Tom offers the following observation:
7 million years ago: the first hominids started to walk upright and run. For millions of years our maximum sustainable speed remained at 1m/s and even running we hardly made it above 3 m/s or a millionth of the speed of light (3 million meter/second).
6000 years ago: our speed went up slightly with the domestication of horses.
150 years ago: railways and automobiles were introduced, with speeds at 30m/s or a 100,000th of the speed of light.
1903: The Wright Brothers reached 5m/s.
Only 40 years later: The speed of sound, 343 m/s, was achieved. (At that point we were already three times faster then our own thoughts: Electrochemical brain signals travel at 100m/s.)
The following 40 years: astonishing speeds were achieved with Gagarin escaping Earth to orbit at 7600m/s or a 40,000th of the Speed of Light. Delta V reached speeds above 11000m/s - the present speed record for human travel.
Our present capacity: as shown by ion propulsion aided Voyager 1: speeds of 17800m/s or a 17,000th of the speed of light.
"From a mathematical perspective, human speed increases have shown exponential growth," Tom says. "We made very little progress during millions of years, but can now travel 17000 times faster than we could only a couple of centuries ago. Interesting enough we are now also at 1/17000 of the speed of light or halfway there in that aspect."
"Although history shows us that making prognoses 10 years or longer is like guessing the weather," Sjogren concluded, "what we do know is that *Ion Propulsion (engine on Voyager 1, thrust on DAWN and DS1) has capacity to reach speeds of up to 30,000m/s and nuclear up to 100,000 or even a million m/s."
"In the Space shuttle we built a much slower vehicle aimed for much shorter distances than what we were capable off," Tom said. "Who knows what would have happened if NASA had gone for Mars instead of the ISS after the moon?"
Next: Space Solar Power
Ion propulsion: Advanced conventional propulsion using electrically charged gas to propel a craft.
Mach's principle: "Standing in a field looking at the stars, your arms are resting freely at your side, and you see that the distant stars are not moving," Mach said. "Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move?" If you make all the stars whirling around you, there is some physical law which make you feel a centrifugal force = Mach's principle. "When the subway jerks, it's the fixed stars that throw you down," Mach concluded.
#Mountaineering #Polar #Space #Mountaineering #Oceans #choice