Interstellar Hydrogen Prevents Light-Speed Travel? 546
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."'"
old news... (Score:1, Insightful)
They already figured this out nearly a hundred years ago.
Do keep up, dear boy... (Score:5, Insightful)
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 [wikipedia.org] for an explanation. The spacecraft itself is sitting in a bubble of normal space, possibly even at rest.
2) Um, ramjets [wikipedia.org], 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
Considering the energy required. . . (Score:5, Insightful)
True, But Irrelevant... (Score:5, Insightful)
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
Bussard ramjet or other solutions perhaps? (Score:1, Insightful)
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.
Fascinating limitation (Score:4, Insightful)
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.
Re:Fuckin' Noobs (Score:5, Insightful)
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.
Re:Let's just hope... (Score:2, Insightful)
Re:Do keep up, dear boy... (Score:5, Insightful)
Re:Do keep up, dear boy... (Score:5, Insightful)
Yes, any number of sci-fi authors have handwaved around these problems for the last few years. Actual scientists, not so much. And, as with TFA, the conclusions of the ones that have been less than sanguine. (From the POV of actually doing it.)
Economics (Score:5, Insightful)
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&
Re:Do keep up, dear boy... (Score:3, Insightful)
Re:Oh noes (Score:2, Insightful)
Don't forget you have to accelerate and decelerate. At an acceleration which you can survive.
Re:Damn it, now they tell me (Score:5, Insightful)
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.
Re:Do keep up, dear boy... (Score:3, Insightful)
You know until we fix the relativity thing, I think we need to just ignore all the other silly problems of near light travel.
Hell that pesky E=Mc2 formula makes even getting to 1/2 the speed of light a massive pain in the ass.
Scientific though experiments are fun and all, but I'd rather they figure out a propulsion system that can generate enough power to get a 1 person spacecraft hit 1/4 the speed of light without needing nearly the energy of an entire planet.
"I'm on the return trip, let's suck up jupiter so we can make it home before supper."
Re:Warp drives don't exist (Score:3, Insightful)
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.
Re:Damn it, now they tell me (Score:4, Insightful)
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.
Re:Damn it, now they tell me (Score:5, Insightful)
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.
Re:old news... (Score:3, Insightful)
Since most of the time the LHC is down that doesn't seem like a big problem :-p
Not to mention, does that comparison mean anything to anyone else? I've never stood in front of the LHC personally and don't know anyone who has. I can -assume- it wouldn't be healthy, but... well, it doesn't really ring home with me. It's not like "Oh shit, interstellar FTL would be like standing in front of the LHC? Well the last time I did that, I got horrible hemorrhoids. Good to know. Note to self: do not drive faster than light to a nearby solar system."
How hard would it have been to make a more visceral if less accurate car metaphor. "99.999998 percent of the speed of light through hydrogen atoms would be like trying to drive your car at 90 miles an hour into a concrete wall." ...although I haven't done that either recently...
Re:Fuckin' Noobs (Score:1, Insightful)
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.
Re:Damn it, now they tell me (Score:3, Insightful)
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.
Re:Economics (Score:2, Insightful)
Long trips: Takes a lot of time to get somewhere else. What if we take time out of concerns? Send entire colonies to get somewhere else at a relatively slow speed, and dont care if it takes a hundred years if they could be sleeping, or have enough resources to make it awake.
...ala generation ships. Here's the problem: Anyone who can make a habitat you can live in for that long has mastered the art of living in space. The last thing such a civilization is going to desire, having successfully climbed out of the gravitational hole they were born in, is climb into another one. So, they might visit other stars, but they wouldn't be "sending entire colonies", they'd be sending tourists.
The point of the Fermi paradox... (Score:3, Insightful)
That sounds like. . . (Score:3, Insightful)
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.
Re:Do keep up, dear boy... (Score:3, Insightful)
Personal Pet Peeve:
Americans who butcher the queen's english and then cringe when they hear/see it spoken/written correctly.
Poul Anderson solved all this (Score:3, Insightful)