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Interstellar Hydrogen Prevents Light-Speed Travel?
garg0yle writes "As if relativity wasn't enough to prevent us traveling at light speed, Professor William Edelstein of the Johns Hopkins University School of Medicine is now claiming that the interstellar hydrogen, compressed in front of the ship, would bring the journey to a shocking end. 'As the spaceship reached 99.999998 per cent of the speed of light, "hydrogen atoms would seem to reach a staggering 7 teraelectron volts," which for the crew "would be like standing in front of the Large Hadron Collider beam."'"
They already figured this out nearly a hundred years ago.
After reading the article (yeah, I know...) tow thought spring to mind...
/., I expect you all to forgive me for using the present tense here [grin]
1) Warp drive doesn't posit a traditional "go-very-fast-through-normal-space" type of spacecraft engine - it warps[*] space-time (hence the name!) in front of and behind the spacecraft - see here for an explanation. The spacecraft itself is sitting in a bubble of normal space, possibly even at rest.
2) Um, ramjets, anyone ?
Seriously, any number of sci-fi authors have covered this problem in enormous detail over the last few decades
Simon
[*] And because this is
Physicists get Hadrons!
. . .to GET to .99999998 c, this is unlikely to be a concern. And if you have the effectively-infinite energy to move a ship at this speed, providing sufficient shielding should be a trivial exercise in additional hand-wavium. . . .
I don't think anyone seriously contemplating relativistic or FTL travel expects to be physically accelerated to such speeds. After all, if stationary interstellar hydrogen is effectively hitting you at teravolt levels, it means that every particle in your body (and the ship) has actually been accelerated to velocities equivalent to the particles in the LHC beam. Not bloody likely. We need warp drive, subspace, wormholes, or something else to solve the problem, not ridiculous conventional acceleration.
- Michael
In a Bussard Ramjet, the hydrogen is a feature, not a bug, something to be used as fuel. If not that, design the ship aerodynamically (is that the right word?) with a long sharp prow to deflect the hydrogen. Of course, by the time we can actually build such a ship, other solutions will be around. Our current issues will be as antiquated looking as 19th century notions of a flying machine.
So, what he's saying is that the interstellar hydrogen density will limit us to no more than about 9600 light years nonstop at a continuous 1g acceleration/deceleration.
Given that even a matter/antimatter conversion drive would require about 116,000,000 tons of reaction mass (half antimatter) for every ton of payload, it would seem that we're going to be hitting a great many limits long before this particular limit begins to be meaningful.
"I do not agree with what you say, but I will defend to the death your right to say it"
UM, I thought the plan was to scoop them up and use them for fuel, ie. you WANT those hydrogen atoms to pile up in front of the ship.
No sig today...
I am afraid toyota's quality problems far exceed simple material issues PPS / PA46 caused by a friction lever or faulty floor mats. Toyota stopped testing their cars properly prior to launch and relied on everyone else to be their test dummies. This is gross negligence on the part of any manufacturer and now they are only beginning to pay the price. I think everyone should be scared when they press on a brake and it takes a second to begin slowing the car down. You would think when you design a car the braking system would have a pretty high priority when testing. I mean if a car company gets one piece of equipment right, it should be the one to stop the 1 ton+ bullet flying out of control. I am just waiting for all the software bugs in the ECU to come out.
Math
Interstellar travel is fundamentally an economic paradox — ignoring, of course, such fantasies as Warp drives.
Sending a Shuttle-sized craft to Alpha Centauri in a matter of years would require roughly the current total energy consumption of humanity.
Only when our civilization advances to the point that we harness a significant portion of the Sun’s total energy output would the energy budget for interstellar travel approximate the same proportion of the energy budget we spend today on interplanetary missions.
One can suggest “sleeper ships,” but building mechanical devices that will survive thousands of years is as hard a problem as throwing them across light years of distance. Any gas will leak out of any container in such a timeframe, and no plastic or rubber seal would last a fraction of the time necessary. The next thought is to provide power to the ship during the long journey, but you need as much total energy as for getting there fast — and, if you can comfortably survive for millennia in interstellar space, why even bother with stars in the first place?
Oh — and the Fermi Paradox applies especially well. Assume that it takes even ten thousand years to colonize a remote solar system, and the entire galaxy would have been overrun by now if a colonizing civilization had started in the terrestrial Jurassic period.
Interstellar travel makes for great space opera, but it has no more bearing on reality than unicorns and dragons.
Cheers,
b&
All but God can prove this sentence true.
Don't forget you have to accelerate and decelerate. At an acceleration which you can survive.
The Tao of math: The numbers you can count are not the real numbers.
And I was just about to get into my 99.999998% lightspeed spaceship.
Aside from the current nonexistence of such a craft, that really does count as the faulty premise with Edelstein's conclusion...
Why would you go that fast (presuming you can't go much faster, of course)? It takes exponentially more energy to accelerate as you approach the speed of light, but that doesn't get you to your destination all that much faster. At a mere 99.9% of the speed of light, you spend less than one extra hour of travel (externally measured, of course) per month. For a "realistic" trip to nearby stars, that means an extra day and a half out of the 4.37 years to get to Alpha Centauri.
For relatively local trips, the difference amounts to a triviality - And longer trips simply will never happen unless we have some breakthrough that makes Star-Trek-like warp engines a reality.
B: Star Trek ain't real.
But science keeps coming up with things based on it: cellphones, PDAs, netbooks, flash memory, etc. Everyone needs inspiration from something.
I don't see how that is an advantage.
If you go faster, you get less time to do.. whatever you'd want to do during the flight. If you <i>want</i> to work slower, slow down the computer running your brain.
Oh, you were planning to go in a biological body? Shame on you, that will never happen when uploading makes it so much cheaper.
Well, the only material difference is the time dilation factor for the person in the spaceship. At 99.9% the speed of light, that factor is about 22 - i.e. the 4.4 years seems to take only about 0.2 years, or 10 weeks. At 99.999998% of the speed of light, it is almost exactly 5000 - which means the trip would seem to pass in about 7 hours. This is ignoring the general relativistic effects of acceleration and deceleration.
So, it's a material difference to the person traveling, but not so material to the observer stationary relative to Alpha Centauri.
Anything that gets sucked into the 'engine' isn't going to be colliding with superstructure or crew like a blast from a particle accelerator.
In essence, a highly efficient Bussard Ramjet design would also be a highly efficient defense from that hydrogen bombardment.
Yep, round-trip time from Earth is important. One-way time is only important if 1) you don't plan on returning home, and 2) you actually know where you're going. Without sending probes or whatever to various star systems, and getting data back from them showing what's there, then any one-way colonization ship isn't going to have a viable destination. It would spend way too much time jumping from star to star until you find something suitable.
If you accept as givens that 1) intelligent life develops with relative ease, and 2) interstellar travel is technologically feasible, then what the Fermi paradox is telling you that we shouldn't expect to be the first, as that outcome is quite unlikely. The universe has been in business for almost 15 billion years, which is plenty of time for lots of civilizations to have developed. Since it's manifestly not true that the universe has been overrun with space-faring aliens, one or both of the premises must be false. My personal bet is that they both are, but I'm pessimistic that way.
That sounds like you're kind of proposing using air resistance to make your car go faster. Which, of course, doesn't make much sense. It's not that the hydrogen has 7 teV of kinetic energy - it's that your SPACESHIP has that energy, and is colliding with hydrogen which is (basically) at rest. You can't extract energy from the 'at rest' hydrogen atoms, because they don't have it. What would happen is that your collision with those molecules would likely destroy your ship (massive hull heating, until you get vaporization; possibly sub-atomic reactions, not sure), and those atoms that passed through the ship would destroy your flesh.
There is a concept, called the Bussard Ramjet, which suggests using some sort of 'scoop' to gather some of the hydrogen in front of and around the ship, and using some of your kinetic energy to compress/heat the hydrogen until you cause fusion, so that you can actually extract energy from the 'at rest' H, but that is fusion energy, not kinetic energy. Once you've released the fusion energy, you could try to direct it away from the ship, thereby getting a net increase in kinetic energy. But, again, the key point there is the energy is being extracted from Hydrogen fusion.
Lasers in front to plasmatize the hydrogen, huge magnetic fields to move the plasma to the REAR of the ship, where a "virtual" burn chamber (really just magnetic fields) captures the plasma. Another mag field keeps the antimatter from touching anything, and gradually releases anti-atoms to the furnace. BOOM mega boost. Easy to shield mere energies if you can do all that trickery with fields. Certainly possible - just very, very hard.
'Once scientists, even the dim-witted social scientists, get muzzled, the Western Civilization is finished.' - oldhack